Dissertations / Theses on the topic 'Organic carbon'

The thesis mainly deals with the explorations of homogeneous palladium and heterogeneous Ruthenium catalyzed Carbon–Nitrogen bond forming reaction of aryl halide with amine and alkyne with sodium azide and benzyl bromide. Heterogeneous palladium, Gold and Brønsted acid catalysed C-C bond forming reaction is investigated by using cross coupling and Michael addition reaction of p-Quinone methide with nucleophile. The work demonstrated in this thesis has been divided into three chapters
CSIR HRDG for fellowship
AcSIR

In the past decade, significant advances have been made in the formation of Csp2-Csp 2 bonds by direct arylation. However, this process generally requires the use of forcing conditions at temperatures typically above 100 °C, which limits the substrate compatibility as well as large-scale applications. Inspired by the recent advances in the development of milder reaction conditions for the arylation of electon-rich arenes in an aqueous medium, we describe that such reactivity is also possible with electron-deficient polyfluorinated arenes at room temperature under biphasic conditions. Several examples are included, highlighting the application of this method to the preparation of a variety of biaryls using iodides bearing electron-poor, electron-rich and sterically encumbering substituents. Several polyfluoroarenes with different substitution patterns are also tolerated. In addition, the method can be extended to the arylation of halogenated thiophenes in a regioselective fashion. However, direct arylation conditions that are general for a broad variety of heterocyclic coupling partners are only sparsely reported and the use of a different set of conditions for each type of substrate remains the norm. As part of a program dedicated to the study of the direct arylation mechanism and the development of broadly applicable reaction conditions, we became interested in investigating the effect of electron-deficient biaryl-type phosphine ligands on the C-H bond cleavage step of this process under Pd(0) catalysis. Inspired by previous reports validating the efficiency of these types of ligands in intramomecular direct arylation, we have developed a new electron-deficient fluoroarylphosphine ligand that promotes C-H bond functionalization of a broad variety of heterocycles. The demonstrated ability of these types of ligands to facilitate the C-H bond cleavage step of this process has been assessed and experimental evidence suggests a concerted metalation-deprotonation mechanism in the presence of an electrophilic metal center. Only recently, nonetheless, has attention been paid to the formation of Csp3-Csp2 bonds by the direct arylation strategy. As an alternative to the use of aliphatic halides as an entry point to a1kylpalladium(II) intermediates, we describe the use of a Heck-like cyclization of an aryl halide as a means of intercepting the key palladium(II) species, along with the first examples of domino Heck-arylation involving intermolecular capture with heterocyclic arenes via C-H bond cleavage. Several examples are presented, demonstrating the application of this method to the preparation of diverse dihydrobenzofurans, indolines and oxindoles substituted with sulfur-containing heterocycles such as thiazoles, thiophenes and benzothiophene.

The conversion of solar energy into electricity through the photovoltaic effect could be a viable approach to supply the global energy requirements with minimal detrimental effects on the enviromnent. Recent research on photovoltaics has focussed on organic photovoltaics (OPVs) which utilises organic materials due to their ease of processing, high light absorption coefficient and potential for low cost thin film device fabrication compared to its inorganic counterparts. The work presented in this Thesis is focussed on enhancing the photo-generated CUlTent of OPV s based on conjugated polymers and fullerene derivatives through the incorporation of multi wall carbon nanotubes (MWCNTs). Initial studies focus on the identification of suitable conditions for the fabrication of efficient reference devices (photo-active layer composed of poly(3-hexylthiphene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (C6o-PCBM)) in order to observe any improvements upon addition of MWCNTs into the active layer. Deteriorated device characteristics are achieved with pristine MWCNTs (p- MWCNTs) incorporated P3HT:PCBM active layer devices due to the poor thin film morphology of the P3HT:p-MWCNTs:PCBM active layer films. This is identified as being due to the poor dispersion of nanotubes in organic solvents that hampers the formation of good interpenetrating networks at the nano-scale. Therefore, to improve the dispersion of MWCNTs in 1,2 dichlorobenzene (DCB) solvent acid functionalisation of MWCNTs is carried out. These dispersible acid functionalised MWCNTs (O-MWCNTs) in DCB are characterised by Raman and infrared spectroscopy, for verification of attachment of functional groups. An enhanced device performance is achieved through the incorporation of 0- MWCNTs in to the P3HT:PCBM system. Optimisation ofP3HT:0-MWCNTs:PCBM solar cells is observed to lead to devices with higher short circuit current densities (Jsc). Investigations towards understanding the enhancement of Jsc from P3HT:0- MWCNTs:PCBM is carried out through external quantum efficiency (EQE) measurements and photoluminescence (PL) spectroscopy. Higher EQE values of P3HT:O-MWCNTs:PCBM active layer devices, in particularly the higher collection probability in the blue and green region of the electromagnetic spectrum suggests an efficient charge separation at donor/acceptor (D/A) heterojunction, reduced recombination, and improved charge carrier mobility as the reasons affecting the increase in the net photo-generated current. The Jsc is shown to increase from 8.0 mAcm-2 in the reference device to 8.34 mAcm-2 in the O-MWCNTs incorporated device. Furthermore, the drastic PL quenching suggests enhanced exciton dissociation in the system and is in agreement with the results achieved from EQE measurements. Analysis of these observations lead to the conclusion that O-MWCNTs are responsible for creating additional charge generating sites (exciton dissociation centres, EDCs) in the active layer. Favourable charge generation at P3HT/O- MWCNTs is observed due to the efficient exciton dissociation at the nano- heterojunction. A hypothesis of "O-MWCNTs as EDCs" is formulated on considering these observations and further investigation ofthe hybrid OPV system is carried out. The dielectric constant (ε) for the composite systems of P3HT:PCBM and P3HT:O- MWCNTs:PCBM are estimated from a space charge limited current (SCLC) model and compared. A 1.23 times increase in the e of P3HT:O-MWCNTs:PCBM composite compared to P3HT:PCBM indicates a lower Coulombic attraction which leads to a lower binding energy. Charge transport analysis conducted through a SCLC model is used to understand the effect of addition of the tertiary component to the existing system and hole mobility is estimated. The addition of O-MWCNTs is favourable in lowering the ε , minimising the exciton binding energy and enhancing the exciton dissociation process in the P3HT:O- MWCNTs:PCBM system. The Jsc achieved for this system is higher than the existing P3HT:PCBM system and the calculated higher hole mobility of this system supports the improved charge transport process. As a result of these achievements, the role of O-MWCNTs in the OPV system is recognised as beneficial for charge generation.

This thesis investigated the use of carbon nanotubes as active components in solution processible organic semiconductor devices. We investigated the use of functionalized carbon nanotubes in carbon nanotubes network transistors (CNNFET) and in photoactive composites with conjugated polymers. For CNNFETs, the objective was to obtain detailed understanding of the dependence of transistor characteristics on nanotubes bundle sizes, device geometry and processing. Single walled carbon nanotubes were functionalized by grafting octadecylamine chains onto the tubes, which rendered them dispersible in organic solvents for solution processing. To investigate the dependence of electronic properties of carbon nanotubes networks on bundle size, we developed a centrifugal fractionation protocol that enabled us to obtain nanotube bundles of different diameters. The electronic properties of networks of nanotube bundles deposited from solution were investigated within a CNNFET device configuration. By comparing devices with different degree of bundling we elucidated the dependence of key device parameters (field effect mobility and on/off ratio) on bundle sizes. We further found that, in contrast to traditional inorganic transistors, the electronic properties of the CNNFETs were dominated by the channel rather than contact resistance. Specifically, the apparent mobility of our devices increased with decreasing channel length, suggesting that the charge transport properties of CNNFETs are bulk rather than contacts dominated. This meant that charge traps in the channel of the device had a significant effect on transport properties. We found that charge traps in the channel region introduced by adsorbed oxygen and silanol groups on the SiO2 surface were responsible for the dominant p-type conductance in as-fabricated devices. Based on this understanding, we demonstrated the p-type to n-type conversion of the transistor characteristics of CNNFETs by depositing nanotubes on electron-trapfree dielectric surfaces. Finally, by combining annealing and surface treatment, we fabricated CNNFETs with high n-type mobility of 6cm2/V.s. For polymer composites, the objective was to obtain detailed understanding of the interactions between carbon nanotubes and the conjugated polymer; a prerequisite for using these composites in organic electronic devices. We fabricated well dispersed nanotube/polymer composites by using functionalized carbon nanotubes and studied the effect of nanotubes addition on the photophysical properties of the technologically important conjugated polymer poly(3-hexylthiophene) (P3HT). Measurement of the photoluminescence efficiency of nanotubes/polymer composites showed that addition of 10wt% carbon nanotubes effectively quenched the polymer emission indicating close electronic interactions. This indicated that nanotubes/polymer composites have potential in organic photovoltaic or light-sensing devices. Further analysis of the steady-state photoluminescence spectra revealed that nanotube addition resulted in increased structural disorder in the polymer. The incorporation of structural disorder into the polymer with the addition of even a small amount of carbon nanotubes may be detrimental to charge transport. UV-vis adsorption studies revealed that one-dimensional templating of P3HT chains by nanotubes resulted in a red-shifted feature in the solutionstate optical adsorption spectra of P3HT. This suggested that presence of nanotube surface templates the polymer self-organisation to produce highly ordered coating of P3HT chains around the nanotube. In order to elucidate the nanoscale origin of this phenomenon, we performed detailed STM studies on individual nanotubes adsorbed with P3HT chains. Since carbon nanotubes can be considered as rolled up sheets of graphite, we also performed STM on P3HT chains assembly on graphite for comparison. For P3HT assembly on HOPG, we found that while 2D crystals were observed when P3HT was cast onto HOPG from dilute solution, a thicker and more disordered film resulted when cast from concentrated solutions and subsequent layers were more likely to align normal to an underlying monolayer of P3HT on the HOPG surface. STM studies of nanotube/polymer mixtures revealed that the P3HT chains are adsorbed on nanotubes surface in such a way that the thiophene and hexyl moieties of the polymer associated with the nanotube surface in identical manner to P3HT monolayer depositions on graphite. This resulted in the increased order as inferred from adsorption UV-Vis spectroscopy, where the polymer chains, which are otherwise prone to chain kinks and twists in solution, adopt a planar configuration when adsorbed onto the nanotube surface.

This thesis investigated the use of carbon nanotubes as active components in solution processible organic semiconductor devices. We investigated the use of functionalized carbon nanotubes in carbon nanotubes network transistors (CNNFET) and in photoactive composites with conjugated polymers. For CNNFETs, the objective was to obtain detailed understanding of the dependence of transistor characteristics on nanotubes bundle sizes, device geometry and processing. Single walled carbon nanotubes were functionalized by grafting octadecylamine chains onto the tubes, which rendered them dispersible in organic solvents for solution processing. To investigate the dependence of electronic properties of carbon nanotubes networks on bundle size, we developed a centrifugal fractionation protocol that enabled us to obtain nanotube bundles of different diameters. The electronic properties of networks of nanotube bundles deposited from solution were investigated within a CNNFET device configuration. By comparing devices with different degree of bundling we elucidated the dependence of key device parameters (field effect mobility and on/off ratio) on bundle sizes. We further found that, in contrast to traditional inorganic transistors, the electronic properties of the CNNFETs were dominated by the channel rather than contact resistance. Specifically, the apparent mobility of our devices increased with decreasing channel length, suggesting that the charge transport properties of CNNFETs are bulk rather than contacts dominated. This meant that charge traps in the channel of the device had a significant effect on transport properties. We found that charge traps in the channel region introduced by adsorbed oxygen and silanol groups on the SiO2 surface were responsible for the dominant p-type conductance in as-fabricated devices. Based on this understanding, we demonstrated the p-type to n-type conversion of the transistor characteristics of CNNFETs by depositing nanotubes on electron-trapfree dielectric surfaces. Finally, by combining annealing and surface treatment, we fabricated CNNFETs with high n-type mobility of 6cm2/V.s. For polymer composites, the objective was to obtain detailed understanding of the interactions between carbon nanotubes and the conjugated polymer; a prerequisite for using these composites in organic electronic devices. We fabricated well dispersed nanotube/polymer composites by using functionalized carbon nanotubes and studied the effect of nanotubes addition on the photophysical properties of the technologically important conjugated polymer poly(3-hexylthiophene) (P3HT). Measurement of the photoluminescence efficiency of nanotubes/polymer composites showed that addition of 10wt% carbon nanotubes effectively quenched the polymer emission indicating close electronic interactions. This indicated that nanotubes/polymer composites have potential in organic photovoltaic or light-sensing devices. Further analysis of the steady-state photoluminescence spectra revealed that nanotube addition resulted in increased structural disorder in the polymer. The incorporation of structural disorder into the polymer with the addition of even a small amount of carbon nanotubes may be detrimental to charge transport. UV-vis adsorption studies revealed that one-dimensional templating of P3HT chains by nanotubes resulted in a red-shifted feature in the solutionstate optical adsorption spectra of P3HT. This suggested that presence of nanotube surface templates the polymer self-organisation to produce highly ordered coating of P3HT chains around the nanotube. In order to elucidate the nanoscale origin of this phenomenon, we performed detailed STM studies on individual nanotubes adsorbed with P3HT chains. Since carbon nanotubes can be considered as rolled up sheets of graphite, we also performed STM on P3HT chains assembly on graphite for comparison. For P3HT assembly on HOPG, we found that while 2D crystals were observed when P3HT was cast onto HOPG from dilute solution, a thicker and more disordered film resulted when cast from concentrated solutions and subsequent layers were more likely to align normal to an underlying monolayer of P3HT on the HOPG surface. STM studies of nanotube/polymer mixtures revealed that the P3HT chains are adsorbed on nanotubes surface in such a way that the thiophene and hexyl moieties of the polymer associated with the nanotube surface in identical manner to P3HT monolayer depositions on graphite. This resulted in the increased order as inferred from adsorption UV-Vis spectroscopy, where the polymer chains, which are otherwise prone to chain kinks and twists in solution, adopt a planar configuration when adsorbed onto the nanotube surface.

The objective of this work is to improve the energy density of carbon/carbon supercapacitors. For achieving this objective, two different strategies were followed depending on the electrolyte used: i) in aqueous electrolytes, our efforts were focused on extending the operating cell voltage by using neutral alkali sulfate solutions; ii) in organic electrolyte, the target was to improve the volumetric capacitance by setting a mild activation method able to produce a porous carbon with average pore size matching the ion size, while not enlarging the pores upon porosity development. A practical cell voltage of 1.8 V has been demonstrated by implementing aqueous alkali sulfates in symmetric carbon/carbon capacitors. It has been shown that the voltage is limited by a partial destructive electro-oxidation of the positive electrode. Such irreversible electro-oxidation could be mitigated by mild chemical oxidation of the active carbon material with hydrogen peroxide; consequently, the voltage could be further expanded up to 1.9 V. Even 2.0 V could be attained after mass balancing the electrodes in order to allow them to operate in their stability window. Finally, pouch-cells with carbon coating on stainless steel current collector were realized by using 2 mol L-1 Li2SO4 as electrolyte. An exceptional cycling stability at cell voltages up to 2.1 V was obtained during 10,000 cycles. Hence, the use of alkali sulfate electrolytes is a cost-effective alternative to organic electrolytes for producing environment friendly and safe carbon/carbon supercapacitors. Dense nanoporous carbons with pores fitting the dimension of ions of the Et4NBF4/acetonitrile organic electrolyte were obtained by high pressure oxidation of non-porous carbon at low temperature, followed by a thermal desorption to remove the surface groups and unblock pore entrances. The activation mechanism consisted in drilling the narrow pores existing initially in the char. Due to the low burn-off, the density of the electrodes was remarkably high allowing high volumetric capacitance values to be reached. This novel production method associates the advantages of environment friendly, cost-effective, high yield and low energy consumption characteristics.

This thesis details the development of methods for and application of the synthesis of carbon carbon bonds using organic sulfur(IV) chemistry. More specifically, the formation of C(sp2) C(sp3) and C(sp3) C(sp3) bonds is explored in detail. The necessity for this research stems from a correlation between a high proportion of sp3 centres in drug candidates, and their success in clinical trials. By facilitating the synthesis of drug candidates with higher fractions of sp3 hybridised carbon atoms, it is hoped that the rate of candidates proceeding through clinical trials may increase. The first topic addressed is the ligand coupling reactions of sulfoxides. In such reactions, the treatment of appropriately substituted sulfoxides with organometallic reagents forms C(sp2) C(sp3) coupling products via σ sulfurane intermediates. These reactions have the ability to excel where transition metal catalysed cross couplings fail; in the coupling of electron deficient (hetero)aromatic groups and alkyl groups. Very few reports have been published detailing the scope and utility of this reaction. The application of this methodology to the synthesis of diarylmethanes is explored in detail. Diarylmethanes are designated as privileged structures for the presence of these moieties in a vast array of diversely functional drug products. Investigation of the scope of the ligand coupling reaction allows for the elucidation of (hetero)aromatic moieties which can undergo this reaction. The depth of analysis in which the scope of benzylic substituents is studied allowed for the elucidation of previously unreported trends, which have been assigned to steric and electronic characteristics of the σ sulfurane intermediates. This knowledge gained is applied to the synthesis of both enantiomerically enriched diarylmethanes and well known drug products. Further exploration of the scope of ligand coupling reactions focusses on the coupling of α functionalised alkyl groups. Remarkable success is found in this completely unexplored area. Benzylic ethers, carbamates and halides are synthesised through a combination of inter molecular and intra molecular ligand coupling reactions. It is proposed that these reactions would be suitable for use in the synthesis of natural products to prove their utility. A newly-discovered sulfoxide homologation is detailed, which occurs upon reaction of sulfenate by products with the aforementioned benzylic halides, both synthesised by a ligand coupling reaction. This is particularly interesting since a similar homologated sulfoxide is found in the substructure of omeprazole, a blockbuster proton pump inhibitor. The second topic addressed is the synthesis of (±)-TAN1251A. The envisaged route proceeds through a novel palladium catalysed [3+2] cycloaddition of sulfinimines, forming methylene pyrrolidines. Previous work focussed on the use of this methodology to produce a diamine, mono-protected as a sulfonamide. A key aspect of the research presented in this thesis is the formation of the C ring of the spiro fused 1,4 diazabicyclo[3.2.1]octane moiety. Initial investigations focus on the synthesis of a pyruvic acid fragment to react with the aforementioned diamine. This concept is developed into the use of pyruvic acid synthetic equivalents: azlactones. A late stage intermediate is produced, however formation of the C ring from this intermediate is not observed. Synthesis is hampered by the deprotection of the sulfonamide, which forms several by-products under the strongly acidic conditions required. A revised retrosynthesis proposes that early deprotection of the diamine sulfonamide would prevent complications. The use of a simplified fragment to facilitate C ring formation is devised, comprising of an α-haloketone. Synthesis of the unprotected diamine is accelerated by serendipity, where a reductive amination also effects the elimination of a sulfinyl group. Formation of an α haloketone fragment is found to be troublesome, however synthesis via the natural product chavicol provides the required functionality. A wide variety of conditions are examined to effect the combination of these fragments. While coupling of the fragments is successful in providing another late-stage intermediate of (±) TAN1251A, formation of the desired C ring is not achieved. Finally, the potential to effect an enantioselective synthesis of (±)-TAN1251A is confirmed using a chiral sulfinamide to direct diastereoselective ketone reduction.

El balanç entre l´entrada de C (dels residus vegetals) i sortides de C (principalment com CO2 de la descomposició del carboni orgànic del sòl -SOC-), determina el contingut de SOC, que és el depòsit de C més voluminós a la superfície terrestre. Als agroecosistemes semiàrids Mediterránis, l’aigua és el principal factor limitant del creixement del cultiu i de l´entrada de residus al sòl. Les pràctiques agronòmiques alternatives poden millorar el creixement vegetal i augmentar la quantitat de residus (entrada de C) en aquestos sistemes. No obstant això la resposta del contingut de SOC dependrà del balanç de les entrades amb les sortides de C. Aquest treball estudia els efectes de l’adopció a llarg termini de sistemes de conreu (NT, sembra directa; MT, mínim conreu CT, conreu convencional) i del nivell de fertilizació nitrogenada (zero; mitjà, 60 kg N ha-1; alt, 120 kg N ha-1) al balanç de C del sòl i el contingut de SOC. El contingut de SOC augmentà finalment 4.3 i 3.9 Mg C ha-1 sota NT repecte a MT i CT. Nivells mitjans i alts de fertilització nitrogenada augmentaren el contingut de SOC en 3.4 i 4.5 Mg C ha-1 respecte al contingut a les parcel•les no fertilitzades. L´adopció a llarg termini de pràctiques de conreu de conservació (sembra directa), juntament amb l’ús adequat de la fertilització nitrogenada van demostrar ser eines per a millorar la sostenibilitat dels nostres secans i emmagatzemar C al sòl.
El balance entre la entrada de C (de los residuos vegetales) y salidas de C (principalmente como CO2 de la descomposición del carbono orgánico del suelo -SOC-), determina el contenido de SOC, que es el mayor depósito terrestre de C. En agroecosistemas semiáridos Mediterráneos, el agua es el principal factor limitante del crecimiento del cultivo y de la entrada de residuos en el suelo. Las prácticas agronómicas alternativas pueden mejorar el crecimiento vegetal y aumentar la cantidad de residuos (entrada de C) en estos sistemas. Este trabajo estudió los efectos de la adopción a largo plazo de sistemas de laboreo (NT, no-laboreo; MT, laboreo minimo; CT, laboreo convencional) y del nivel de fertilización nitrogenada (cero; medio, 60 kg N ha-1; alto, 120 kg N ha-1) en el balance de C del suelo y el contenido de SOC. El contenido de SOC aumentó en 4.3 y 3.9 Mg C ha-1 bajo NT con respecto a MT y CT. Niveles medios y altos de fertilización nitrogenada aumentaron el contenido de SOC en 3.4 y 4.5 Mg C ha-1 con respecto al contenido en las parcelas no fertilizadas. La adopción a largo plazo de prácticas de laboreo de conservación (no-laboreo o siembra directa), junto con el uso adecuado de la fertilitzación nitrogenada demostraron ser herramientas para mejorar la sostenibilidad de los secanos semiáridos Mediterráneos y almacenar C en el suelo.
The balance between C inputs (from plant residues) and C outputs (mainly as CO2 from soil organic carbon -SOC- decomposition) determines the content of SOC which is is the largest terrestrial reservoir of carbon. Under semiarid Mediterranean agroecosystems, water limitation restrains plant growth and the return of crop residues to the soil. Alternative agronomical practices may improve crop growth and increase return of crop residue (C inputs) under these systems. This work studied the effects of long term adoption of tillage practices (NT, no-tillage; MT, minimum tillage; CT, conventional tillage) and nitrogen (N) fertilization level (zero; medium, 60 kg N ha-1; high, 120 kg N ha-1) on the SOC balance and the content of SOC. The stock of SOC was increased by 4.3 and 3.9 Mg C ha-1 under NT in comparison to MT and CT respectively. Long-term medium and high N fertilization increased the stock of SOC by 3.4 and 4.5 Mg C ha-1 in contrast to unfertilized plots. Long-term adoption of conservation tillage practices (no-tillage) together with adequate N fertilizer use, proved to be effective tools to improve sustainability of semiarid Mediterranean drylands and to store C in the soil.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1998.
Includes bibliographical references (leaves 185-201).
Many industrially important synthesis reactions are carried out in liquid solvents such as aromatic compounds, chlorinated hydrocarbons, and other organic liquids which pose environmental and health hazards either because of their toxicity or their persistence in the environment. Hence proper disposal of these solvents and the prevention of accidental releases or routine emissions cause serious difficulties and costs for the industries who use them. An approach to mitigating these problems is to use alternative solvents that are environmentally benign or that can be completely recycled in a closed-loop process. One such alternative solvent is supercritical carbon dioxide. Although supercritical carbon dioxide is used in many industrial extraction and chromatography processes it is not widely used as a reaction medium and its effects on chemical reactions are not well understood. The goals of this research were to gain a better understanding as to the effect of supercritical carbon dioxide through a systematic investigation of solvent conditions on the rates and selectivities of several model organic synthesis reactions. In addition, the use of environmentally benign catalysts/promoters in gaseous and supercritical carbon dioxide as well as developing chemical pathways in which carbon dioxide can act as a solvent as well as a reactant were explored to expand the possible industrial applications. In the pursuit of these goals, new reactors, feed and sampling procedures, as well as new chemical pathways were explored. Specifically, the bimolecular rate constants of the Diets-Alder reaction of ethyl acrylate and cyclopentadiene were measured in supercritical carbon dioxide from 38 to 88 °C and pressures from 80 to 210 bar. At constant temperature, the rate increased with pressure or density and was most dramatic near the critical point of carbon dioxide. A traditional Arrhenius expression was used to correlate the kinetic data at a constant system density. All of the rate constant data were normalized to the rate constant at the same temperature and at a fixed density of 0.5 g/cm3. These normalized rate constants over a range of temperatures then collapsed on a single line as a function of density. Rates could be predicted using a bimolecular Arrhenius expression with the pre-exponential term having a linear dependence on density. Theoretically, a rigorous transition state theory rate constant was derived and used to gain a better understanding of the non-ideal solvent-reactant-product interactions which could influence the rate. Effects of pressure/density and temperature on the regio- and stereo- selectivity of several Diels-Alder reactions were explored. Regioselectivity did not correlate well with density changes; however, stereoselectivity did. As pressure was increased, the endo isomer always increased in the supercritical region. The stereoselectivity changes were modeled using temperature and density as the model inputs. Again, the rigorous transition state theory rate constant was used to explain the observed selectivity changes. Phase behavior played an important role in these investigations, sometimes influencing selectivity. The design and construction of reactors with a sapphire window allowed for visual access into the reaction environment to monitor phase behavior. Silica was shown to increase the rate and selectivity of several Diels-Alder reactions in carbon dioxide. Pressure/density effects were explored using the reaction of methyl vinyl ketone and penta-1,3-diene. Pressure did not affect the selectivity; however, it had a large effect on the yield of the reaction. This was discovered to be caused by the change in phase partitioning of the reactants between the fluid phase and the solid surface as pressure was changed. Adsorption isotherms at various pressures and temperatures were found. Because of the non-ideal system, the thermodynamic effect of temperature on the adsorption equilibrium needed to be derived. The effect of temperature on the adsorption was found at constant pressure. Although an enthalpy of adsorption could be determined, the presence of non-ideal phase behavior complicates its interpretation. In general, the adsorption enthalpy consists of partial molar enthalpies of both species (reactant and carbon dioxide) on/in both phases (solid/fluid). At constant density, the effect of temperature allows for the direct calculation of the entropy of adsorption. This term is affected by the partial molar entropies of both species on/in both phases. Three different carboxylation reactions were investigated in supercritical carbon dioxide. The Kolbe-Schmitt reaction (direct carboxylation of a phenolate salt) was found to proceed at high yields in supercritical carbon dioxide. Attempts at lowering the temperature of reaction by using cosolvents was not successful. Temperature and pressure had minimal effect on the selectivity of the reaction. Two other carboxylation reactions were examined. In the first study, the homogeneous catalyzed caboxylation of an allylsilane was performed in supercritical carbon dioxide. Pressure did not appear to affect the reaction; however, there was a narrow temperature range which allowed the reaction to proceed. At best, yields were only 15%. The final reaction studied was the catalyzed (Lewis acid) carboxylation of an alkene by carbon dioxide. Unfortunately it did not proceed in supercritical carbon dioxide to any measurable extent at temperatures of 40 to 350 °C with and without the presence of various catalysts.
by Randy D. Weinstein.
Ph.D.

Thesis: Ph. D. in Environmental Chemistry, Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2015.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 101-110).
.Organic molecules have many important roles in the atmosphere, acting as climate and biogeochemical forcers, and in some cases as toxic pollutants. The lifecycle of atmospheric organic carbon is extremely complex, with reaction in multiple phases (gas, particle, aqueous) and at multiple timescales. The details of the lifecycle chemistry (especially the amount and properties of particles) have important implications for air quality, climate, and human and ecosystem health, and need to be understood better. Much of the chemical complexity and uncertainty lies in the reactions and properties of low-volatility oxidized intermediates that result from the oxidation of volatile organic precursors, and which have received comparatively little study thus far. This thesis describes three projects that link together the entire chain of oxidation (volatile to intermediate to condensed) in an effort to improve our understanding of carbon lifecycle and aerosol production. Laboratory studies of atmospherically relevant aerosol precursors show that the slow oxidation of intermediates is critical to explaining the yield and properties of aerosol under highly oxidized ("aged") conditions, and that the production of organic particles is significantly increased when intermediates are fully oxidized. This aging process is a strong function of molecular structure, and depends on aerosol concentration through the phenomenon of condensational trapping. Further laboratory studies of a series of (poly)cyclic 10 carbon alkanes show that structural effects are largely explained through fragmentation reactions, and that more generally, carbon-carbon bond scission is a ubiquitous and important reaction channel for oxidized intermediates. Finally, direct measurement of oxidized intermediate compounds in field studies shows that these compounds are abundant and important in the ambient atmosphere, with concentrations and properties in between those of volatile and particulate organic compounds. Together with other co-located measurements and complementary techniques, this enables estimates of emission, oxidation, and deposition to be constructed. The results from this thesis can be used to inform more sophisticated models of atmospheric organic carbon cycling, and to improve prediction of organic particulate matter concentrations.
by James Freeman Hunter.
Ph. D. in Environmental Chemistry

This dissertation mainly contains two parts: one is C-X (C, O, S) bond formation through gold(I) catalysis, one is new applications via gold(I/III) redox catalysis. In first part, gold(I) catalysts would be introduced and their general applications, then the TA-Au species will be emphasized including the design, synthesis, characters and their application in catalysis. The applications are well developed during the past decade in our group, but here only involves three examples regarding C-C, C-O and C-S bond formations. From these effective applications, the unique stability and reactivity of TA-Au will be studied and explained, which is the reason and value of TA-Au discovery. In second part, gold(I/III) redox catalysis will be presented through two application examples: cross-coupling of terminal alkynes, multiple bond di-functionalization. The most challenging part for coupling reactions is the competition between homo-coupling and cross-coupling products, while in our project, we have successfully developed a new method to selectively obtain cross-coupling as major product to homo-coupling product (ratio 12:1). Later on, we found a new method to achieve gold (I/III) redox cycle by using mild oxidant diazonium salt instead of PIDA or Selectfluor strong oxidant. The new mild and efficient method have largely extended the application of gold(I/III) redox catalysis into organic synthesis. In sum, the new gold catalysts and catalysis methods reported here are important to the development of gold catalysis field, which are critical and useful to help people understand the reason of applying noble gold species as catalysts, and the advantages that other metals do not have.

Total organic carbon (TOC) and chemical oxygen demand (COD) are two methods used for measuring organic pollutants in wastewater. Both methods are widely used but the COD method results in production of hazardous wastes, including mercury.The purpose of this study was to validate the method TOC that will replace COD and find a factor to convert TOC to COD. In this study 26 samples were analyzed from four sewage treatment plant in the municipality of Enköping.The results show that the COD method could be replaced by the TOC method.The factor for COD/TOC was between 3.1 - 3.3. Both methods will be used in parallel until 2013 when it will be forbidden to use the COD analysis.

Le dioxyde de carbone (CO2), principal contaminant des gaz naturels bruts et du biogaz doit être extrait en vue d’un enrichissement en méthane (CH4) compatible avec les spécifications d’injection en réseaux de gaz naturel. Au cours des dernières années, une famille de matériaux poreux de type réseaux organométalliques à base de magnésium (Mg-MOF-74) a ouvert une nouvelle perspective à cet effet en raison d’une excellente affinité des sites métalliques exposés au sein de la structure cristalline pour l’adsorption du CO2. Ce matériau est un adsorbant potentiellement bon candidat pour l’enrichissement en CH4 de gaz naturel et de biogaz par des procédés opérant en modulation de pression. La présente étude propose d’examiner l’amélioration des performances d'adsorption du CO2 en mélange avec le CH4 par dopage du matériau Mg-MOF-74 avec des nanotubes de carbone et de l'oxyde de graphène. L'objectif est d'améliorer les propriétés texturales pour favoriser la diffusion des molécules des gaz dans les micropores et leur accessibilité aux sites d'adsorption. Les matériaux ont été synthétisés sous réaction solvothermique et caractérisés par DRX, IRTF, MEB, ATG et physisorption d’azote à 77K. Les équilibres et énergies d'adsorption ont été mesurées suivant une méthode manométrique dans une gamme de pression allant jusqu'à 35 bar et à 25°C, 50°C et 75°C. La cinétique de sorption a été étudiée à partir d’expériences de manométrie et de la méthode dite « Zero Length Column » à 25°C, 50°C et 75°C. A une teneur optimisée à 0,3% en masse d’agent dopant, le modèle de Brunauer–Emmett–Teller montre que la surface spécifique des matériaux dopés est augmentée de plus de 21% par rapport à celle du matériau non-dopé. Les données d'équilibre indiquent que la capacité d’adsorption en CO2 est sensiblement améliorée pour les matériaux dopés dans toute la gamme opératoire étudiée, tandis qu’ils démontrent une sélectivité comparable ou améliorée, dépendante de la température
Carbon dioxide (CO2), which is the major contaminant present in raw natural gas and biogas need to be extracted to increase their methane (CH4) content and match the standards of pipeline injection. In recent years, a family of porous materials, magnesium-based Metal Organic Framework (Mg-MOF-74), has opened new perspectives for this purpose thanks to strong adsorption affinity of CO2 with exposed metallic sites in the crystalline network. This material is a potential good adsorbent candidate for the enrichment in CH4 of natural gas and biogas by Pressure Swing Adsorption processes. The present study proposes to examine the CO2 adsorption performances and separation ability from CH4 of Mg-MOF-74 materials doped with carbon nanotubes and graphene oxide. The objective is to improve the texture of the materials to promote the diffusion of gas molecules into micropores and their accessibility to adsorption sites. The materials were synthesized under solvothermal reaction and characterized by PXRD, FTIR, FESEM, TGA and physisorption of nitrogen at 77K. The adsorption equilibria and energies were measured using manometric method in a pressure range up to 35 bar and at 25°C, 50°C and 75°C. The sorption kinetics of CO2 and CH4 on the materials were studied from manometric experiments and using the Zero Length Column method at 25°C, 50°C and 75°C. At an optimized content of the doping agents of 0.3 wt%, Brunauer–Emmett–Teller model shows that the specific surface area is increased for both composites, by more than 21% compared to the pristine material. The equilibrium data indicates that the CO2 adsorption capacity is significantly improved in the whole range of operating conditions for both composites compared to the pristine material, whereas the CO2/CH4 adsorption selectivity appears either comparable or better as a function of temperature

Soils in permafrost regions hold substantial amounts of carbon, much of which has accumulated due to processes that are related to cold temperatures. A warming climate will alter the dynamics governing the fluxes of carbon within a system and consequently the pools of carbon therein. Of particular concern is whether previously stored carbon will be released to the atmosphere contributing to the pool of greenhouse gases and creating a feedback effect. At the moment the International Panel of Climate Change (IPCC) does not include carbon dynamics of the Arctic in their forecast models due to a lack of adequate scientific understanding in the area. Understanding the controls which govern the fluxes of carbon between the land, the atmosphere and the aquatic systems is important in evaluating the transient state of the carbon cycle. This study investigates the potential relationship between terrestrial soil organic carbon (SOC) pools and the dissolved organic carbon (DOC) concentrations in streams observed at the beginning of August 2012 in the Abiskojokka catchment in the sub-arctic region of northern Sweden. The results show that soil organic carbon pools could tentatively explain between 24 % and 44 % of the variation in DOC concentrations in streams. This is only a fraction of the variation explained compared to regions where peatlands are the single most important indicator of DOC concentrations. In the absence of peatland, which covers less than 2 % of the Abiskojokka catchment area, heath vegetation and the associated soil forming processes were shown to be an important indicator of stream water DOC concentrations.

It is well documented that increases in soil organic matter (SOM) improve soil physical properties and increase the overall fertility and sustainability of the soil. Research in SOM storage has recently amplified following the proposal that agricultural soils may provide a significant carbon (C) sink that may aid in the mitigation of increasing atmospheric carbon dioxide. Observed differences in lint yield and nitrogen response from a cotton performance study at the Texas A&M University Experimental Farm near College Station, TX prompted us to examine the effects of tillage and rotation on soil organic C (SOC), soil microbial biomass C (SMBC), 38-day cumulative C mineralization (38-day CMIN), hot-water extractable organic C (hot-WEOC), carbohydrate C, and total glomalin. The treatments examined included conventional-till continuous cotton (CT), reduced-till continuous cotton (RT), and conventional-till cotton after corn rotation (CC) treatments. In pre-plant soil samples, SOC, SMBC, and 38-day CMIN in the top 5 cm were 33, 58, and 79 % greater in RT and 29, 32, and 36 % greater in CC vs. CT. Comparable differences were observed for hot-WEOC and carbohydrate C. Little seasonal variation was observed for labile-C pools throughout the growing season, suggesting minimal C input from cotton roots. Water-stable aggregation was not significantly affected by management, and did not correlate with labile-C pools or total glomalin. Labile-C pools were generally more responsive to management vs. SOC and were strongly correlated with one another. Carbohydrate C of hot-water extracts exhibited the strongest relationships with SMBC and 38-day CMIN, even though it comprised only 3 and 5 % of these pools, respectively. Our data suggest that increasing SOC in Texas cotton-cropping systems through conservation management is possible. Long-term data are still needed to fully address SOC storage potentials in Texas, but increases in labile-C pools resulting from conservation management are attainable and have the potential to positively impact soil fertility.

This thesis presents the study of organic layers covalently assembled onto carbon surfaces. As a result of their attachment, the properties of carbon surfaces were controllably adjusted so that these surfaces could be used for desired applications. In order that a wide range of properties were imparted onto the carbon surface, many different modifiers were attached and thoroughly characterised. Three applications that the modified carbon surfaces were used for were the subsequent coupling of molecular species, adsorption of protein and assembly of aldehyde/sulfate-functionalised polystyrene (PS) and citrate-capped gold nanoparticles (NPs). Finally, patterning of different organic layers at pre-determined spatially defined locations on the one carbon surface was also investigated. The carbon surfaces used in this work were glassy carbon (GC) and pyrolysed photoresist film (PPF) surfaces. For PPF, methods for the reproducible fabrication of electrochemically suitable surfaces were investigated. The properties of GC and PPF surfaces are very similar apart from the surface roughness. PPF has near atomic smoothness and has RMS roughness values that are approximately four times smaller than GC. The first series of modifier layers attached to the carbon surfaces was via the oxidation of seven different primary amines. The different layers allowed the modulation of the wettability of the surface. Both n-tridecylamine (TDA, monoamine) and 1,12-diaminododecane (DAD, diamine) are able to form multilayers. The stability of TDA and DAD layers were tested by scanning, soaking and sonicating the layers in different media. Changes in the layer were monitored by the probe response of ferrocene monocarboxylic acid (FCA). However, atomic force microscope (AFM) depth profiling experiments showed that changes in the probe response did not indicate cleavage of the covalently attached layer and mechanisms are proposed to account for the changes in the response of the probe. Surface concentrations of the amine modifiers were estimated by the coupling of an electrochemically active species, FCA and nitrobenzoyl chloride (NBC). The electrochemical reduction of the 4-nitrophenylethylamine (NPEA) layer in acid caused the layer to 'shrink'. Surface concentration estimates of NPEA from acid reduction of layers with different thicknesses suggested that only a limited fraction of the p-nitrophenyl groups were reduced in acid. However, in ACN (acetonitrile)/0.1 M [Bu4N]BF4 (tetrabutyl ammonium fluoroborate) the relationship between the concentration of electroactive surface groups and layer thickness was linear. The other series of modifiers that was attached to alter the surface properties was performed by the reduction of aryl diazonium salts. Subsequent coupling reactions of tetraethylene glycol diamine (TGD) to para methylene carboxylic acid phenyl (MCA) and NBC to electrochemically reduced para nitro phenyl (NPh) layers were carried out. Surface concentrations of NPh as estimated from reduction scans was higher when reduction was performed in ethanol/water compared to acid. Four peaks at N1s binding energies were observed in x-ray photoelectron spectroscopy (XPS) spectra for both acid and ethanol/water reduced layers. The ability of attached amine and aryl layers to modulate the adsorption of protein was investigated using fluorescently labelled protein, bovine serum albumin-fluorescein isothiocynate (BSA-FITC) and fluorescence microscopy. TGD, para methyl phenyl (MP), para hexyl phenyl (HP) and para polyethylene glycol phenyl (PEG)-modified GC surfaces promoted protein adsorption relative to as-prepared GC, whereas n-hexylamine (HA) and polyethylene glycol diamine (PGD) layers reduced protein adsorption. The assembly of two types of NPs, aldehyde/sulfate-functionalised PS and citrate-capped gold NPs, onto amine-containing modifiers layers was examined. Citrate-capped gold NPs were synthesised and characterised. The surface coverage of the gold NPs was controlled by using different modifiers of different chemical compositions, tuning the modification conditions and adjusting the immersion time, concentration and pH of gold NP solution. Approaches to creating patterns of modifiers in pre-determined spatially defined locations on GC and PPF surfaces using poly(dimethyl)siloxane (PDMS), poly(vinyl)alcohol (PVA) and thin metal films were investigated. With the "fill-in" approach using PDMS, the smallest pattern of modifiers was the parallel lines with a line width of 20 µm and straight edges and was created by performing electrochemistry in PDMS microchannels which has not been previously investigated. Visualisation techniques, based on optical and scanning electron microscopy, were demonstrated for the molecular patterns.

With the emission of carbon dioxide (CO2) becoming an international worry due its role in climate change, solutions such as CO2 capture and storage technologies are needed to decrease the emissions. The main proportion of CO2 gas emissions is from fossil fuel combustion in a range of industries, including power generation. To develop the CO2 capture system for these operations, new materials are needed for CO2 capture. Metal-organic framework (MOF) materials have porous crystal structures containing organic molecules (organic ligands) linked to each other by metalcontaining nodes. The large internal surface area can be exploited for the adsorption of small gas molecules, and for this reason MOFs may be ideal candidate materials for CO2 capture and gas separations. Thousands of MOF materials have been reported, with different combinations of the ligands and metals and with the capability of forming many different network topologies. Experimentally it is very difficult to study the gas absorption dynamics, interaction and gas adsorption capacity for the large number of materials. This problem can be solved by simulations. The aim of the thesis is to develop a systematic simulation method to screen the MOF properties and CO2 adsorption capacity and interaction dynamics at different environment. The molecular dynamics (MD) method with parameterised force fields was used to study the interactions between CO2 molecules and one class of the MOFs, zeolitic imidizolate frameworks (ZIFs) with zinc as the metal cation. To develop the model, the atom charges have been developed by using the distributed multipole analysis (DMA) method based on ab initio DFT calculations for molecules and clusters. The intermolecular forces were developed by fitting against the MP2 calculations of small clusters of the metal cations and molecular ligands. In order to evaluate the models I simulated the gas-liquid coexistence curve of CO2 and showed that it is consistent with experiments. I also simulated the pure ZIF structures on changing both temperature and pressure, demonstrating the stabilities of the structures but also showing the existence of displacive phase transitions. I have used this approach to successfully study CO2 absorption in a number of ZIFs (from ZIF-zni, ZIF-2, ZIF-4, ZIF-8 and ZIF-10) using MD. The gas absorption capacity and dynamics have been investigated under 25 bar and 30 bar, 200 , showing a promising uptake of CO2. The results have shown that CO2 capacity is mainly determined by the pore sizes and pore surfaces, in which a higher capacity is associated with a higher pore surface. The intermolecular distance of CO2 inside the pores and channels have been investigated in the saturation state. It has been shown that the distance is approximately 4 Å. The attraction force is from the interaction between CO2 and the imidazolate ligands. In addition, the systematic studies of the saturated ZIF system gave the minimum diameters for CO2 adsorption which is approximately 4.4 Å. This interaction has caused the gate opening effects, with the imidazolate ligands being pushed to be parallel to the CO2 molecules and opening up to allow more gas molecules go through the channels that connect the pore structures. This gate opening effect also explains the phase transition in ZIF-10 caused by CO2 molecules in our simulation, and can be applied to predict phase transitions in other materials with similar structure such as ZIF-7 and ZIF-8. The dynamics have also shown that the gas diffusion velocity is determined by the pore structure as well and by the accumulated layers of CO2 on the surface prior to being pushed in toward the centre of the material layer by layer. The de-absorption processes have also been studied in these materials by decreasing the pressure from 25 bar to 1 bar under at same temperature. The results indicate that the de-absorption is a reverse process of absorption. The structure of ZIF-10 went through a phase transition induced by CO2 recovered after the guest molecules had been released. The de-absorption can be accelerated by increasing the temperature.

Peatlands are serving as one of the most important terrestrial carbon stores in the United Kingdom and globally. In the UK, the current trend of peatlands turning from carbon sinks to carbon sources is widely observed and reported. As numerous factors may affect the carbon cycle of peatlands, including climate, land management, hydrology and vegetation, dissolved organic carbon (DOC) was commonly used as an indicator of peatland carbon changes. Besides the function as an indicator of carbon turnover in peatland, increasing DOC in the stream water also raises concern in water companies as the removal of DOC from water represents a major cost of water treatment. This thesis investigates the impacts of land management such as drain blocking and revegetation on stream DOC changes. By building a pilot column study, this thesis also assessed the potential of bank filtration serving as DOC treatment in UK. Results of drain blocking shows the management was a significant impact on the DOC changes. However, later investigation of peak flow events indicates such positive impacts from drain blocking were minor in terms of high peak flow events. Since the majority of DOC export occurred during such peak flow events, drain blocking were found not as an efficient management of DOC changes. The field study of revegetation observed minor effects of revegetation on stream DOC. The results of column bank filtration indicate low DOC removal rate under the current stream DOC level in UK. The bank filtration may efficient remove DOC when higher DOC input applied. However, it is not suitable for UK peatland under current DOC export.

Present organic carbon fluxes from an upland peat catchment were quantified through measurement of in-situ direct and indirect greenhouse gas fluxes. To predict future greenhouse gas (GHG) fluxes, peat from eroded (E) and uneroded (U) site of an upland peat catchment was characterized.Composition of peat from E and U sites at the Crowden Great Brook catchment, Peak District Nation Park, UK that was characterized by Pyrolysis-Gas Chromatography-Mass Spectrometry (Py-GC-MS) at 700 oC. Pyrolysis products of the peat were then classified using the Vancampenhout classification into 6 compound classes - viz. aromatic and polyaromatic (Ar), phenols (Ph), lignin compounds (Lg), soil lipids (Lp), polysaccharide compounds (Ps) and N-compounds (N). There was no significant difference in the composition between the eroded and uneroded sites within the study area or between peats from different depths within each site. Nevertheless, there was a significant difference between sites in the proportions of Sphagnum that had contributed to the peat. Pyrolysis products of the peat were also classified into pedogenic (Pd) and aquagenic (Aq) OC – the mean percentage of Pd in both eroded and uneroded peats was 43.93 ± 4.30 % with the balance of the OC classified as Aq.Greenhouse gas (GHG) fluxes were quantified directly by in-situ continuous measurement of GHG was carried out at the E and U sites of the catchment using a GasClam: mean in-situ gas concentrations of CH4 (1.30 ± 0.04 % v/v (E), 0.59 ± 0.05 % v/v (U) and CO2 (8.83 ± 0.22 % v/v (E), 1.77 ± 0.03 % v/v (U)) were observed, with both the CH4 and CO2 concentrations apparently unrelated to atmospheric pressure and temperature changes. Laboratory measurements of ex-situ gas production - for both CH4 and CO2 this was higher for U site soils than for E site soils. At the U site, maximum production rates of both CH4 (46.11±1.47 mMol t-1 day-1) and CO2 (45.56 ± 10.19 mMol t-1 day-1) were observed for 0-50 cm depth in soils. Increased temperature did not affect gas production, whilst increased oxygen increased gas production. The CH4/CO2 ratios observed in-situ are not similar to those observed in the ex-situ laboratory experiments; suggest that some caution is advised in interpreting the latter. However, the maximum OC loss of 2.3 wt. % observed after 20 weeks of ex-situ incubation is nevertheless consistent with the long-term degradation noted by Bellamy et al (1985) from organic-rich UK soils. Indirect greenhouse gas (GHG) fluxes were quantified through the mass flux of suspended organic carbon (SsOC) drained from studied catchments. The SsOC was quantified by interpolating and rating methods. Unfiltered (UF) organic carbon (OC) fluxes in 2010 were calculated to be 8.86 t/km2/yr for the eroded sub-catchment and 6.74 t/km2/yr for the uneroded sub-catchment. All the rating relationships have a large amount of scatter. Both UF OC and <0.2 µm fraction OC are positively correlated with discharge at the eroded site, whilst there is no discernable relationship with discharge at the uneroded site. SsOC is dominated by Pd type OC (95.23 ± 10.20 % from E; 92.84 ± 5.38 % from U) far more so than in sources of the peats, suggesting slower oxidation of Pd (cf. Aq) OC.

En els darrers anys, el desenvolupament de reaccions de carboxilació reductiva de (pseudo) halogenurs orgànics amb diòxid de carboni (CO") catalitzada per metalls per a la preparació d'àcids carboxílics s'ha convertit en una poderosa alternativa a l'ús d'èspecies organometàl·liques, en la majoria dels casos sensibles a l'aire. Tanmateix, l'ús d'alcohols simples no protegits o d'hidrocarburs insaturats en combinació amb CO" per obtenir àcids carboxílics mitjançant una reacció de formació d'un enllaç C-C han rebut molta menys atenció. Aquests representen una alternativa atractiva als halurs orgànics, ja que són abundants i fàcilment disponibles. En aquesta tesi doctoral es descriu la carboxilació selectiva d'alcohols al·lílics amb CO2, una metodologia capaç d'obtenir àcids carboxílics insaturats amb un control excel·lent de la selectivitat obtinguda.

Carbon-14 was measured in the dissolved organic carbon (DOC) in ground water and compared with ¹⁴C analyses of dissolved inorganic carbon (DIC). Two field sites were used for this study; the Stripa mine in central Sweden, and the Milk River Aquifer in southern Alberta, Canada. The Stripa mine consists of a Precambrian granite dominated by fracture flow, while the Milk River Aquifer is a Cretaceous sandstone aquifer characterized by porous flow. At both field sites, ¹⁴C analyses of the DOC provide additional information on the ground-water age. At the Stripa site the DIC from the recharge area probably precipitates at around the 300 m level of the mine, never reaching the deeper ground waters. In this case, ¹⁴C analyses of the DOC provides a better estimate of the ground-water age. The dilution of the DIC by carbonates and microbial processes in the Milk River Aquifer is so great that geochemical corrections of ¹⁴C data are difficult. This is another example where ¹⁴C analyses of the DOC provide more information on ground-water age. Carbon-14 was measured on both the hydrophobic and hydrophilic organic fractions of the DOC. At the Stripa site, the hydrophobic organic compounds in the V2 borehole ranged from 7,500 to 15,500 years before present, suggesting a young component of ground water. Other hydraulic and isotopic evidence supports relatively recent ground water mixing with older brines in this borehole. The δ¹³C values of the DIC in the V2 borehole are light and similar to the stable carbon isotope values for the DOC, supporting a biogenic origin of the DIC. The organic compounds in the hydrophobic and hydrophilic fractions were also characterized. The DOC may originate from kerogen in the aquifer matrix, from soil organic matter in the recharge zone, or from a combination of these two sources. Carbon-14 analyses, along with characterization of the organics, were used to determine this origin. Carbon-14 analyses of the hydrophobic fraction in the Milk River Aquifer suggest a soil origin, while ¹⁴C analyses of the hydrophilic fraction suggest an origin within the Cretaceous sediments (kerogen) or from the shale in contact with the aquifer.

El canvi climàtic, produït per l’increment de la concentració de gasos d’efecte hivernacle a l’atmosfera, amenaça la integritat del nostre planeta. En aquestes circumstàncies el biochar, material obtingut a partir de biomassa pirolitzada, s’ha proposat com a una possible mesura per augmentar el segrest de carboni en sòls. L’aplicació de biochar en sòls pot servir com a magatzem de carboni a llarg termini compensant les emissions de CO2. No obstant, l’eficàcia del biochar depèn del tipus de biochar i sòl utilitzats. L’objectiu principal d’aquesta tesi és avaluar els efectes de l’aplicació de biochars de pi (PB) i de blat de moro (ZB) a una dosi de 6.5 g kg-1 en un sòl franco-arenós amb pH neutre i baix contingut de carboni orgànic (CO) en condicions de camp durant dos anys. Els objectius específics són els efectes de l’aplicació de biochar en : 1) la resistència termoquímica del CO del sòl (Capítol 1 i Capítol 2); 2) la disponibilitat del CO pels microorganismes (Capítol 3); 3) la protecció física del CO per oclusió en els agregats (Capítol 4). Els mètodes utilitzats per estudiar els efectes del biochar sobre la resistència del CO van ser: pèrdua de pes per ignició (LOI), combustió-seca (TOC), oxidació forta (sO) i feble (mO) amb dicromat-potàssic, hidròlisis-àcida (AH), oxidació amb peròxid d’hidrogen (PO) i anàlisis-isotòpic. A més, el CO-resistent del sòl i del biochar es va estimar mitjançant un balanç de masses. També, es van dur a terme dos mostrejos de sòl a curt i llarg termini (2 i 26 mesos), i es van incubar durant 250 dies. El dia 30 i 250 d’incubació va ser determinada la quantitat i la senyal isotòpica del CO2-C respirat. Addicionalment, es va mesurar el CO-dissolt en les mostres de sòl mitjançant el mètode d’extracció amb aigua-calenta. Les propietats físiques van ser avaluades quantificant el pes dels agregats estables amb aigua destil·lada i de la fracció en partícules amb hexametafosfat (per la disgregació dels agregats) utilitzant el wet-sieving apparatus. A més, el CO procedent del sòl natiu i del biochar dins i fora dels agregats es va estimar mitjançant un balanç de masses utilitzant el mO i el TOC. També es va estimar la contribució de CO del sòl i del biochar en els sòls esmenats amb ZB utilitzant el anàlisis-isotòpic. Es van trobar quantitats de ROC similars en els sòls controls estimats mitjançant mO i AH (5 g CO kg-1), mentre que més contingut de ROC es va observar en els sòls esmenats (6-12 g CO kg-1). La presencia de biochar es va detectar en els sòls esmenats mitjançant la comparació del δ13C en sòls esmenats i no-esmenats, independentment de l’origen del biochar. D’altra banda, el 35% del CO del biochar de ZB dels sòls esmenats es va perdre en dos anys com a resultat de la dissolució del biochar en el sòl. A curt termini, es va observar un priming-negatiu en sòls esmenats amb PB i el contrari en sòls esmenats amb ZB, en resposta al major contingut de CO-làbil del ZB. No obstant, un lleuger priming negatiu es va observar en els dos sòls esmenats a mig termini ja que augmenta la protecció física del CO. Mentre el PB tendeix a ser incorporat en els agregats, el ZB promou l’oclusió del CO natiu del sòl. Al esgotar-se el CO-làbil, el CO queda protegit dins dels agregats. Per tant, l’aplicació del biochar en sòls agrícoles mediterranis augmenta la persistència del CO en el sòl com a resultat de la resistència innata del CO del biochar i la protecció física augmentant el contingut de CO dins dels agregats.
El incremento de gases de efecto invernadero en la atmosfera puede tener consecuencias severas para nuestro planeta. El uso de biochar como enmienda, material obtenido a partir de biomasa pirolizada, se ha propuesto como estrategia para el secuestro de carbono en el suelo. Sin embargo, la efectividad del biochar varía mucho dependiendo del biochar y el tipo de suelo. El objetivo principal de esta tesis es evaluar los efectos de dos biochares, de restos de pino (PB) y mazorca de maíz (ZB), incorporados a una dosis de 6.5 g kg-1 en un suelo de viña franco-arenosa con pH neutro y bajo contenido de carbono orgánico (CO), en condiciones de campo durante dos años. Los objetivos específicos fueron la evaluación de: 1) la resistencia del CO en el suelo a los procesos termoquímicos (Capítulo 1 y Capítulo 2); 2) la disponibilidad de CO a ser mineralizada por microorganismos del suelo (Capítulo 3); y 3) protección física de CO por aumento de agregados (Capítulo 4). Los métodos analíticos utilizados para evaluar los efectos del biochar en el CO resistente del suelo fueron: pérdida de peso por ignición (LOI), combustión-seca (TOC), oxidación fuerte (sO) y suave (mO) con dicromato potásico, hidrólisis-ácida (AH), oxidación con peróxido de hidrogeno (PO) y análisis isotópico. Además, se estimó el CO-resistente del suelo y del biochar a través de un balance de masas. Por otro lado, el suelo se muestreó a corto y medio plazo (2 y 26 meses) y las muestras se incubaron en el laboratorio durante 250 días. Se determinó el CO2-C liberado durante la respiración del suelo y la señal isotópica del día 30 y 250 de incubación. Además, se cuantificó el CO disuelto mediante un extracto con agua caliente. Para evaluar las propiedades físicas, se determinaron los agregados estables en agua destilada y el peso de la fracción particulada con hexametafosfato para la disrupción de los agregados usando el wet-sieving apparatus. El CO oxidable del suelo nativo y del biochar dentro y fuera de los agregados se estimó a través de un balance de masas usando mO y TOC. Por otro lado, mediante el análisis isotópico se estimó la contribución de CO del suelo nativo y del biochar en suelos enmendados con ZB. Se cuantificaron valores similares de ROC en los suelos control mediante AH y mO (5 g C kg-1), mientras que se obtuvieron valores de ROC más altos en los suelos enmendados con biochar (6-12 g C kg-1). Además, la detección cualitativa de biochar se logró comparando δ13C en suelos enmendados y controles, independientemente del origen del biochar. Sin embargo, el 35% de ZB-CO se perdió durante los dos años de experimento por dilución del biochar en el suelo. A corto plazo se observó un priming-negativo en suelos enmendados con PB y al contrario en los suelos con ZB debido al mayor contenido de CO-lábil en ZB comparado con PB. Sin embargo, se encontró un priming ligeramente negativo a medio plazo en ambos suelos enmendados con biochar, como consecuencia de una mayor protección física del CO. Mayores cantidades de TOC y BOC se encontraron en los agregados de los suelos enmendados aunque tuvieron lugar dos procesos diferentes, mientras el PB tiende a incorporarse en agregados el ZB promueve la oclusión del CO del suelo nativo. Al agotarse el CO-lábil, el CO-ocluido queda protegido previniendo las pérdidas adicionales por degradación. Por lo tanto, la aplicación de biochar a un suelo agrícola mediterráneo aumenta la persistencia del CO del suelo debido a la resistencia innata al biochar-CO y la protección física del CO, que previene la degradación biótica o abiótica del CO.
The increment of global threats due to climate change, caused by an increase in atmospheric concentration of GHGs, is predicted to have a severe impact on our planet. The use of biochar, obtained from the thermochemical conversion of biomass in an oxygen-limited environment, as a soil amendment has been proposed as one strategy for C-sequestration. Many environmental benefits have been attributed to the application of biochar into soil, including long-term C-sequestration compensating for CO2 emissions. However, biochar effectiveness still remains under debate because effects can vary greatly depending on biochar and soil type. The main objective of this thesis was to assess the effects of two contrasting biochars, from pine wood (PB) and corn cob (ZB) remains, incorporated at a rate of 6.5 g kg-1 on a sandy loam vineyard soil with neutral pH and low organic carbon (OC) content, in field conditions over two years. Specifically, the aims were to evaluate the consequences of the addition of the different biochars on: 1) soil OC resistance to thermochemical processes (Chapter 1 and Chapter 2); 2) the potential OC availability to be mineralized by soil microorganisms (Chapter 3); and 3) physical OC protection by the promotion of aggregates (Chapter 4). The analytical methods used to evaluate the effects of biochar in soil OC-resistance were: weight loss-on-ignition (LOI), dry-combustion (TOC), strong (sO) and mild (mO) acid potassium dichromate oxidations, acid hydrolysis (AH), peroxide-oxidation (PO) and isotope analysis. Moreover, soil and biochar resistant-OC (ROC) was estimated through a mass balance. Also, soil field samples were collected at the short- and the medium-term (2 and 26 months after the application, respectively), and then incubated in the lab for 250 additional days. The CO2-C released as soil respiration and the CO2-C isotopic signature were assessed after 30 and 250 days of the incubation. Additionally, dissolved-OC was assessed in the field soil samples by hot-water extraction. Regarding physical properties, water-stable aggregates and particulate fraction weight were determined using a wet-sieving apparatus, using distilled water or hexametaphosphate for aggregates disruption. Oxidisable and resistant OC (attributed mainly to native soil and biochar, respectively) inside and outside of aggregates was estimated through a mass balance using mO and TOC. On the other hand, native soil and biochar-OC contribution in ZB biochar-amended soil was estimated by isotope analysis. The ROC estimated by AH and mO led to similar values in control soil (5 g C kg-1 soil), whereas higher ROC values were obtained in biochar-amended ones (6-12 g C kg-1 soil). Moreover, qualitative biochar detection was achieved by comparing δ13C in amended and non-amended soils regardless of the biochar feedstock origin. However, 35% of ZB biochar-OC was apparently lost over two years, which was attributed to biochar dilution into soil. In addition, in the short-term, negative-priming was observed in amended-soil with PB (made at high temperature) whereas positive-priming was seen in those amended with ZB (produced at lower temperatures) as a result of the highest labile-OC content in ZB biochar compared to PB. However, in the medium-term, slightly negative-priming effects in both biochar-amended soils were found. This could be explained by promotion of physical protection processes preventing priming. This fact was corroborated as higher TOC and BOC amount was observed inside of aggregates in biochar-amended soils compare to controls. It seems that PB tended to be incorporated into aggregates while ZB promoted native soil-OC occlusion. Then, after labile-OC has been exhausted, the promotion of OC occlusion prevented further losses. Therefore, the application of biochar to a Mediterranean agricultural soil increases soil-OC persistence due to innate biochar-OC resistance and OC physical protection, which decrease OC degradation by abiotic and biotic agents.

Methods for the 11C-labeling of carbonyl compounds applicable in the preparation of radiotracers for Positron Emission Tomography (PET) are described. To this end [11C]carbon monoxide at low concentration was used in transition metal- mediated reactions. Stille couplings were employed in the synthesis of [carbonyl-11C]ketones from methyl and aryl halides with [11C]carbon monoxide. The synthesized [carbonyl-11C]ketones were obtained from the corresponding organostannanes with analytical radiochemical yields up to 98%. A number of synthetic routes were designed using [11C]carbon monoxide and rhodium complexes. Nitrene intermediates were generated from azides and reacted via a rhodium-mediated carbonylation reaction as a general synthetic route to [carbonyl-11C]isocyanates, versatile precursors. [carbonyl-11C]Isocyanate reacted via nucleophilic attack of an amine to form N,N’-diphenyl[11C]urea in 82% analytical radiochemical yield, ethyl phenyl[11C]carbamate was synthesized by the same route, using ethanol as the nucleophile, in 70% radiochemical yield. [11C]Isocyanate was also able to react in a [2+3] cycloaddition with ethylene oxide to form 3-phenyl[carbonyl-11C]oxazolidin-2-one in over 80% analytical radiochemical yield. This method was applied to the synthesis of a potential efflux system tracer [11C]hydroxyurea in 38% isolated radiochemical yield and the derivative 1-hydroxy-3-phenyl[11C]urea in 35% isolated radiochemical yield. Carbene intermediates, generated from diazo compounds, were reacted with [11C]carbon monoxide in the rhodium-mediated synthesis of [carbonyl-11C]ketenes. [carbonyl-11C]Ketene intermediates were utilised in the synthesis of diethyl[carbonyl-11C]malonate, from ethyl diazoacetate and ethanol. The product was obtained with a 20% isolated radiochemical yield. Alkylation of diethyl[carbonyl-11C]malonate, with ethyliodide and tetrabutylammonium fluoride, was successfully accomplished and diethyl diethyl[carbonyl-11C]malonate was synthesized in 50% analytical radiochemical yield. Several (carbonyl-13C)compounds were also synthesized using the described methods as a way of characterizing the position of the label using 13C-NMR.

Thesis advisor: Lawrence T. Scott
The focus of this project was to probe the ability of various transition metal complexes to cleave carbon-carbon bonds in a C30H12 hemifullerene. The hemifullerene was synthesized in our lab from commercial 1-tetralone and bromonaphthalene in six steps. Palladium and nickel complexes were used to open the five membered rings along the periphery of the C30H12 bowl. Diphosphine complexes of nickel were capable of opening either all three five membered rings or one of the periphery five membered rings and the central six membered ring
Thesis (BS) — Boston College, 2005
Submitted to: Boston College. College of Arts and Sciences
Discipline: Chemistry
Discipline: College Honors Program

This thesis investigates a total synthesis of the incednine aglycon by utilising alkenylsilane reagents to assemble the pentaenyl and tetraenyl systems through cross-coupling reactions. The early chapters develop methodology to access both cyclic alkenylsiloxanes and functionalised (E)-alkenylsilanes by the controlled hydrogenation of alkynylsiloxanes and silylolefination of aldehydes, respectively, and culminate in the synthesis of a C6-C13 bis(alkenylsilane)incednine fragment (Scheme 1). The C1-C5 and C14-C23 coupling partners are synthesised in three and ten steps from propargyl alcohol and L-alanine methyl ester through phosphorous-based olefination strategies. In the final chapter we describe our first generation approach to incednine which entails orthogonal cross-couplings to construct the C5-C6 and C13-C14 bonds (Scheme 2).

La chimie d'interface du diazonium a progressé au cours des dernières années et s'est pratiquement impliquée dans tous les domaines de la science et technologie des matériaux. L’utilisation des sels de diazonium est justifiée par le fait qu’ils adhèrent aux surfaces avec de fortes énergies de liaison, en particulier sur le carbone sp², ce qui en fait d’excellents agents de couplage pour les polymères aux surfaces. Dans ce contexte, nous avons travaillé sur deux types de nanohybrides de nanotubes de carbone (NTC) : NTC-polytriazole (NTC-PTAz) et NTC-colorant. Le nanohybride NTC-PTAz a été synthétisé par polymérisation « click » en surface. Pour ce faire, les NTCs ont été greffés de groupes 4-azidophényle à partir du sel de diazonium correspondant. Le NTC modifié (NTC-N3) a servi de support pour une polymérisation confinée en surface de type polyaddition générant ainsi le nanohybride NTC-PTAz. Ce matériau a été caractérisé par ATG, XPS, IR et Raman. Ses applications potentielles sont dans le développent d’adsorbants de métaux lourds, l’immobilisation de nanocatalyseurs ou pour le stockage des gaz. La seconde partie de la thèse est plus étoffée et porte sur les nanotubes de carbone greffés de colorants diazotés Rouge Neutre (NR), Azure A (AA) et Rouge Congo (CR). L’analyse fine de ces matériaux a révélé une très forte adhésion des colorants aux NTCs et les couches superficielles ont des épaisseurs de 2 à 6 nm, sont homogènes et continues. Les NTC-colorant ont été incorporés dans des matrices élastomères de type EVA pour la réalisation d’actionneurs opto-thermiques implantés dans des pads pour non-voyant. Dans les matrices EVA, les NTCs greffés de colorants servent à capter la lumière et induire un changement de forme dans le pad qui soit palpable par le non voyant (250 µm). Les matrices EVA renforcées de nos nanotubes greffés de colorants ont été réalisées et testées par analyse mécanique dynamique. Les composites NTC/colorant-EVA sont flexibles et prometteurs pour le développement de nouveaux types des pads tactiles pour les non-voyants. Les nanohybrides NTC-NR ont servi comme capteurs chémo-résistifs pour la reconnaissance moléculaire de l’acétone.Dans une dernière application, le nanohybride CNT-CR a été étudié en tant qu’électrocatalyseur pour l’oxydation directe du méthanol. Des résultats intéressants ont été obtenus avec ces nanohybrides mais des améliorations significatives (rapport 3) des propriétés électrocatalytiques ont été obtenues avec des CNT-CR décorés avec des nanoparticules d'or. Le système électrocatalytique nouvellement conçu pourrait être considéré pour différentes applications prometteuses, notamment les capteurs, les biocapteurs, les catalyseurs hétérogènes pour les piles à combustible. Pour résumer, les nanohybrides à base de CNT nouvellement conçus présentent des performances uniques attribuées à la polyvalence de la chimie d'interface du diazonium pour la fixation efficace de couches moléculaires et macromoléculaires fonctionnelles. Les nanohybrides novateurs servent de blocs de construction pour la conception de matériaux nanocomposites à hautes performances potentiellement utiles dans les nouveaux défis socio-économiques tels que l’environnement, la biomédecine et l’énergie
Diazonium interface chemistry has progressed over the last few years and practically involved in all areas of materials science and engineering. The rationale for employing diazonium salts is that they attach to surfaces with remarkable bond energies, particularly on sp² carbon materials, making them an ideal coupling agent for polymers to surfaces In this context, novel CNT-polytriazole (CNT-PTAz) and CNT-dye nanohybrids were designed and thoroughly characterized. First, CNT-PTAz nanohybrid was prepared by click polymerization: multiwalled carbon nanotubes (CNTs) were modified with azidophenyl groups (CNT-N3) from 4-azidobenzenediazonium precursor and served as nanoscale platform for the surface confined polyaddition. The CNT-PTAz nanohybrid was characterized by TGA, XPS, IR, and Raman. The robust CNT-PTAz is robust and has potential in developing heavy metal adsorbents, nanosupport for catalysts or for gas storage. In the second major part, we grafted CNT with diazotized Neutral red (NR), Azure A (AA) and Congo Red (CR) dyes by simple, spontaneous reaction of the diazonium salts and CNTs in water, at RT. A thorough investigation of the nanohybrids showed that the adhesion is strong (CNT-dye C-C bond energy higher than 150 kJ/mol), and the layer is uniform. These nanohybrids further served to reinforce ethylene-vinyl acetate (EVA) an elastomeric matrix. The reinforced matrix is flexible and serves as optothermal actuators where the grafted dye catches the light to induce mechanical changes in the matrix monitored by dynamic mechanical analysis. CNT/dye-reinforced EVA is a promising flexible composite for developing new types of visual-aid tablet for visually impaired people. The versatile CNT-dye nanohybrids are also unique chemiresistive gas sensors for the molecular recognition of acetone vapours. In a final application, CNT-CR nanohybrid was investigated as an electrocatalyst for the Direct Oxidation of Methanol. Interesting results were obtained with these nanohybrids but significant improvements (3-fold) of the electrocatalytic properties were achieved with CNT-CR decorated with gold nanoparticles. The newly designed electrocatalytic system could be regarded for different promising applications most likely as for sensors, biosensors, heterogeneous catalysts for fuel cells and for nanotechnology To summarize, newly designed CNT-based nanohybrids have unique performances ascribed to the versatility of the diazonium interface chemistry in efficiently attaching functional molecular and macromolecular layers. The novel nanohybrids serve as building blocks for designing high performance nanocomposite materials relevant to challenging timely social economic issues, namely environment, biomedicine and energy

A major control on the attenuation of organic contaminants dissolved in groundwater is their sorption onto solid organic matter (OM) in the rock. Sorption modelling is currently based on the amount of solid organic carbon in the rock. However, there are very few available data on the total organic carbon (TOe) content in common UK geological materials. A significant new set of Toe measurements on a range of important formations is presented. Methods to measure TOe in geological, especially carbonate-rich, samples are reviewed and evaluated. The impact of the type of OM on its sorption capacity is not understood. Non-linear isotherms measured on seven samples (of Lincolnshire Limestone, Glacial Till from Norfolk and unconsolidated deposits) had a wide range of organic carbon normalised distribution coefficients (Koc from 7.85 l/g to 767 l/g at 0.01 gil trichloroethene). This indicates the impact of characteristics of the OM. Bulk geochemistry and micro-morphology characteristics of the OM that could be important predictors for sorption capacity are investigated and identified. Organic matter has been isolated, and the isolation technique evaluated. The major element composition of the isolated OM has been determined; elemental results were found to correlate with results of a pyrolysis analysis applied to whole rock samples. Morphological analysis of microscope slides of isolated organic matter provided information on the physical types (visually) and size (by image analysis) of the organic particles. Measured Koc values correlated with the elemental HlO content of the sample's OM and with the pyrolysis measurements, but not with morphological results. The effect of selected empirical isotherms on solute transport was simulated: use of an accurate distribution coefficient is essential, but non-linearity was found not to make a major impact on arrival results. Recommendations are made for the improvement of sorption modelling, and for appropriate analysis methods to supply relevant data on the type of OM in this context.

This thesis is focused on developing metal-organic and organic molecules for photocatalytic water splitting and carbon dioxide reduction. In chapter 1, an overview of hydrogen production, dye-sensitized solar cells and carbon dioxide reduction are provided. The development history and reaction mechanisms of catalytic systems are introduced along with the typical examples in each field. The applications of both metal-organic and organic compounds are covered. In chapter 2, nine molecular organic photosensitizers were designed and synthesized. The nine molecules were employed as the photosensitizing reagent in the fabrication of dye-sensitized solar cells and applied in photocatalytic water reduction via coupling with TiO2 semiconductors and Pt co-catalyst. The highest turnover number (TON) of 10200 was achieved by organic photosensitizer 1g for hydrogen generation. The effect of alkyl chains and triarylamine donor moiety to the photocatalytic performance was investigated. A shorter alkyl chain was found to favor the reaction due to a lower hydrophobicity which in turn may block the interaction between the photocatalyst and water molecules. Besides, the triarylamine donor units facilitated high hydrogen generation rates by reducing the contact between catalytic active sites and the oxidized form of sacrificial reagents. In chapter 3, five earth-abundant metal complexes were synthesized to serve as the catalyst and CdS nanorods (NRs) were prepared to be the photosensitizer for the photocatalytic water reduction. A cobalt dithiolene complex (2a) achieved a TON of 30635 in 20 h under the blue light irradiation at a concentration of 10 µM. A new complex 2c also gave a high TON of 12375 under the same conditions and its TON was further improved to 115213 in 87 h by reducing the concentration of catalyst by ten times. The size effect of CdS NRs was investigated and larger nanoparticles exhibited higher hydrogen production rates. In chapter 4, ten iridium(III) complexes were synthesized and used as dual-functional molecules in photocatalytic carbon dioxide reduction by acting as both the photosensitizing reagent as well as the catalyst. The best performance was achieved by 3j, giving a TON of 230 under the irradiation of blue LED. A push-pull effect brought by trifluoromethyl and methoxy group sucessfully enhanced the carbon dioxide reduction efficiency. The hydrophobicity of n-butyl chain also provided effective protection to the active sites of reaction intermediate. Additional steric hindrance was found to extend the lifespan of photocatalytic systems but led to a drop in the overall conversion efficiency. Chapter 5 summarizes the specific synthetic procedures and characterization parameters of the molecules in chapters 2-4.

L’exportació de carboni fixat mitjançant la fotosíntesi pel fitoplàncton, des de la superfície dels oceans a les capes més profundes, és un component clau de la bomba biològica de carboni i, per extensió, del cicle global del carboni, ja que manté els nivells de CO2 atmosfèrics per sota d’on es trobarien en l’actualitat si aquest procés no es donés (Feely et al., 2001; Khatiwala et al., 2009; Parekh et al., 2006). El cicle de les partícules i la seva exportació són també essencials pels cicles biogeoquímics d’altres macronutrients i espècies químiques de vital importància per la biota marina, així com metalls i contaminants d’origen antropogènic. El parell de radiotraçadors 234Th:238U ha estat utilitzat de forma extensa en l’estudi de l’exportació de partícules i en la determinació de la força de la bomba biològica de carboni en els oceans (Coale and Bruland, 1985; Le Moigne et al., 2013b). Aquesta tesi avalua els fluxos d’exportació de carboni als oceans i l’eficiència del segrest de diòxid de carboni mitjançant processos biològics fent ús d’aquest parell de radiotraçadors naturals en diversos règims oceanogràfics i sota contrastades condicions biogeoquímiques. En primer lloc, la variabilitat de l’export a escala de conca oceànica va ser examinada a l’Atlàntic Nord- Occidental al llarg d’un transsecte latitudinal (de 64ºN a l’equador) amb alta resolució espacial, proveint dades addicionals en zones sub-mostrejades. Els resultats, que coincideixen amb estudis previs que varen tenir lloc al Nord Atlàntic, van ser comparats amb diferents models d’exportació derivats de satèl·lits. Aquests models tenen una forta dependència en les estimacions de temperatura superficial del mar i producció primària neta, però normalment no consideren paràmetres biològics que influencien l’exportació de carboni, com ara l’estructura de la xarxa tròfica, la intensitat de depredació, l’eficiència de reciclatge, l’activitat bacteriana o l’exportació de carboni orgànic dissolt (Maiti et al., 2013). Les diferències observades entre les estimacions d’exportació de carboni derivades dels models de satèl·lits o del mètode del 234Th posen de manifest la necessitat d’incloure aquest tipus de paràmetres biològics a escala regional, per la qual cosa són necessaris esforços continuats d’observació. La inclusió d’aquests paràmetres reduiria la incertesa de l’inventari de carboni global i milloraria el monitoratge del cicle del carboni des de plataformes basades en satèl·lits. En segon lloc, la zonació de les propietats de les aigües superficials derivades dels diferents fronts localitzats al llarg d’un transsecte a 10ºE, de 44ºS to 53º S, en el Corrent Circumpolar Antàrtic va ser avaluada en relació amb l’exportació de partícules. Els nostres resultats mostren com, malgrat el contrast en les xarxes tròfiques observades al nord i al sud del Front Polar Antàrtic (~49ºS), la magnitud dels fluxos d’exportació de carboni era similar al llarg del transsecte. Existien diferències, però, en examinar les eficiències de transferència: a la meitat nord de la secció, la qual estava dominada per nanofitoplàncton, presentava eficiències d’exportació altes i eficiències de transferència baixes en comparació a la meitat sud de la secció, dominada per microfitoplàncton. Així doncs, malgrat que els diferents règims de xarxa tròfica donaren lloc a exportacions de carboni similars, el conjunt de partícules que sedimentaven diferia en la seva composició entre el nord i el sud del Front Polar Antàrtic (agregats de partícules petites en el nord vs partícules grans de sedimentació ràpida al sud), donant lloc a dos escenaris diferents pel que fa a la quantitat de carboni exportat que arribà a les capes més profundes. Per últim, les estimes del flux de partícules i l’eficiència d’exportació van ser examinades a una conca semitancada (el Golf de California i les aigües adjacents del Pacífic Tropical Nord Oriental) amb una estacionalitat molt marcada que va acompanyada de canvis en la comunitat fitoplanctònica. Les estimes d’exportació es varen obtenir mitjançant el mètode del 234Th, juntament amb trampes de sediment. Les dades de fraccionament per mides i l’alta ressolució vertical obtingudes amb bombes in situ van permetre la comparació de l’atenuació amb la fondària de les ràtios C/234Th entre partícules petites (1-53 μm) i grans (>53 μm). El resultats indiquen que, sota el domini de pico- i nanoplàncton i amb la presència de diazotrofs, les partícules petites juguen un paper important en l’exportació de carboni i que aquest export, en la zona d’estudi en qüestió, pot ser més eficient que l’export resultant d’una comunitat planctònica dominada per diatomees.
The particulate export of photosynthetically fixed carbon from the surface ocean to the ocean interior by marine plankton is a key component of the biological carbon pump and, by extension, of the global carbon cycle as it helps to maintain atmospheric CO2 levels lower than would occur with out this process (Feely et al., 2001; Khatiwala et al., 2009; Parekh et al., 2006). Particle cycling and export are also essential for the biogeochemical cycles of other major nutrients and chemical species of vital importance for marine biota, as well as anthropogenic metals and pollutans. The radiotracer pair 234Th: 238U as been commonly and extensively used to study particle export and determine the strength of the biological carbon pump in the upper ocean (Coale and Bruland, 1985; Le Moigne et al., 2013b). This thesis evaluates oceanic carbon export fluxes and the efficiency of the biologically mediated uptake of atmospheric CO2 using this naturally occurring radiotracer pair in a variety of regimes under contrasting biogeochemical conditions. First, basin-scale export variability was examined in the North Western Atlantic Ocean along a latitudinal transect (from 64ºN to the equator) with high spatial resolution, providing additional data in under sampled areas. The results agreed with previous studies carried out in the North Atlantic and were also compared with different satellite-derived export models. These models have a strong dependence on sea surface temperature and net primary productivity estimates, but they usually do not consider biological parameters that influence carbon export, such as the trophic structure, the grazing intensity, the recycling efficiency, the bacterial activity and the dissolved organic carbon export (Maiti et al., 2013). The differences observed between the satellite-derived and the 234Th-derived carbon export estimates highlights the necessity to include such biological parameters at a regional scale, for which continued observing efforts are needed. This would thereby reduce uncertainty in the global carbon budget and improve carbon cycle monitoring from satellite-based platforms. Second, the zonation of surface properties derived from the various fronts crossed along a 10ºE transect, from 44ºS to 53ºS, in the Antarctic Circumpolar Current were evaluated in relation to particle export. Our results show that, despite the contrasting food webs encountered north and south of the Antarctic Polar Front (~49ºS), the magnitude of the carbon export fluxes were similar along the transect. However, differences appeared when examining transfer efficiencies: in the northern section, which was dominated by nanophytoplankton, presented high export efficiencies and reduced transfer efficiencies in comparison to the southern section, dominated by microphytoplankton. Thus, and although different food web regimes led to similar export of carbon, the sinking particle pools differed in their composition north and south of the Antarctic Polar Front (aggregates of small particles in the north vs fast-sinking large particles in the south), resulting in two different scenarios regarding the amount of exported carbon that reached greater depths. Finally, estimates of particle flux and export efficiency were examined in a semi-enclosed basin (Gulf of California and the surrounding waters of the Eastern Tropical North Pacific), with a strong seasonality that leads to changes in the planktonic community. Export estimates were assessed using the 234Th approach in combination with surface-tethered sediment traps. Data on size fractionation and high vertical resolution of in situ pump deployments allowed a comparison of the C/234Th ratios attenuation with depth between small (1-53 μm) and large (>53 μm) particles. Results indicate that, under dominance of pico- and nanoplankton and with presence of diazotrophs, small particles play and important role in carbon export and that this export might be more efficient than that resulting from a diatom dominated planktonic community in the study area.

Since the carbon nanotubes were first discovered by Iijima in 1991, CNTs have been the focus of intense research by many groups. Nearly 7000 papers and 700 theses on carbon nanotubes can be found from the eminent journals such as Nature and Science in the last decade. Since carbon nanotubes show impressive mechanical, physical and electronic properties such as high stiffness, high strength, low density, and excellent thermal conductivity, suggesting its role in light-weight high strength material application. A great quantity of important research has evidently been done in this field. The purpose of this thesis research is to investigate the feasibility of MWCNTs for the application of polymer organic photovoltaics, and to study the formed MWCNTs-P3HT polymer nanocomposites properties, which are optical absorption, fluorescence emission, and morphology, as well as the formed photovoltaic device performance. This fundamental research would significantly contribute to the advanced technology development for how to improve the efficiency of the polymer organic photovoltaics.

In rivers draining the western Southern Alps, the organic carbon concentration (C_org) and stable isotopes of organic carbon (δ¹³C_org) are used to determine the source of riverine particulate organic carbon (POC). The rivers contain a mixture of POC derived from the terrestrial biosphere (vegetation and soils) and fossil POC in bedrock described by C_org and δ¹³C_org. The fraction of riverine POC derived recently from atmospheric CO₂ (fraction non-fossil POC, F_nf) is quantified using this mixing relationship. F_nf, C_org suspended sediment transfer and water discharge (Q_w) are used to calculate the erosion of POC from the terrestrial biosphere in these active mountain belts. The high yields (34±5 tC km^-2 yr^-1 in western Southern Alps, and 31±7 tC km^-2 yr^-1 in Taiwan) are presently sustained by the net primary productivity of the forest ecosystem in both mountain belts. With detailed knowledge of the source of riverine POC the processes responsible for its mobilisation and transfer are investigated. The primary tool is the detailed sample set collected from 15 rivers in Taiwan that combine the geochemistry of riverine suspended load POC with records of water discharge (Q_w), SSC and precipitation. Remote sensing is used to provide additional insight. Three main routing processes are identified: 1. Landsliding – mobilising standing biomass and soils; 2. Overland flow – during precipitation organic materials are washed from hillslopes to the channel; and 3. Grinding – breakdown or coarse organic fragments during transport in turbid river waters. These processes cause the observed enrichment in non-fossil POC concentration in rivers (POC_nf, mg L^-1) during floods, which conflicts with a conventional view of dilution at high Q_w and SSC. These processes lead to positive relationships between POC_nf and Q_w in Taiwanese rivers and this may be common throughout vegetated mountain catchments. The POC routing processes identified here lead to the high non-fossil POC yields in these mountain belts sustained by both tectonic uplift and climatically-driven erosion and sustenance of the terrestrial biosphere. Because of the observed power law relationship between POC_nf and Q_w, large floods caused by storms are responsible for the bulk of the riverine non-fossil POC transfer. It is recognised for the first time that storm-triggered floods optimise the delivery of non-fossil POC to depositional environments at times when it is likely to be sequestered in sediment. In Taiwan, the mobilisation of non-fossil POC from hillslopes significantly impacts the terrestrial biosphere. A move toward N-limitation on steep slopes (observed in δ¹⁵N of vegetation and soil) is driven by the physical removal of organic matter during rainfall and may influence the net primary productivity of the ecosystem. If common throughout mountains in tropical Oceania, this climatically driven phenomenon affects the ability of these forests to sequester atmospheric CO₂ on decadal time-scales.

Dissolved organic matter (DOM) including carbon and nitrogen (DOC and DON) are important but poorly understood components of the marine biogeochemical cycle. In this study, the distribution and cycling of DOC and DON, and particulate organic carbon and nitrogen (POC and PON) were investigated in North Sea surface and bottom water during the stratified summer season in 2011 and 2012, along with other key biogeochemical parameters such as nutrients. The summer DOC, DON, POC and PON ranged from 32.7-134.5, 2.8-13.7, 1.1-43.8 and 0.3-5.9 μM, respectively. The well-mixed water of the southern North Sea was also surveyed in the winter of 2011; measured concentration of DOC and DON were 56.2-224.8 and 3.7-12.3 μM. In summer, DOM and POM generally exhibited high levels in the southern well-mixed water (SM), whereas inorganic nutrient concentrations were higher in the northern bottom water (NB) due to nutrient regeneration and offshore water inflow. DOM in summer and inorganic nutrients in winter were also clearly influenced by riverine inputs. DON was the dominant nitrogen fraction of northern surface water and SM in summer, while in NB, TOxN (nitrate + nitrite) was the dominant fraction. Analysis of SmartBuoy samples show phytoplankton provided a net source of DOM over the spring bloom period with net degradation in autumn and winter. Incubation experiments on water collected from two North Sea sites in autumn, winter 2013 and spring 2014 showed no nutrient (N and P) limitation on DOM degradation. The experiments yield mean bacterial decay rate constants (for three seasons) at the two sites of 4 ± 8 and 2 ± 3 %d-1 kDOC and 3 ± 4 and 4 ± 4 %d-1 kDON, under dark conditions. In comparison to the Redfield ratio, the bulk C:N molar ratio is enriched in carbon relative to nitrogen, while the slope C:N ratio is close to the Redfield ratio, but with a background of high C:N material.

The focus of the current study was on the recovery of carbon from municipal bio-waste streams. Firstly, the relationship between methanogenic pathways and the properties of anaerobic granules was studied using two pilot-scale upflow anaerobic sludge blanket (UASB) reactors with different granule size distribution. UASB1 granules were larger (3-4 mm) with multi-layered internal structure and the archaeal community was dominated by acetoclastic methanogens, while the UASB2 granules were smaller (1-2 mm) without a layered internal structure and the archaeal community was predominated by hydrogenotrophic methanogens. The acetoclastic methanogenic activities of UASB1 (250-437 mL CH4/g VS·d) than UASB2 (150-260 mL CH4/g VS·d), confirming that acetoclastic methanogenesis was more dominant in UASB1. Temperature increase from 20oC to 28oC did not change the microbial community but resulted in increased and stable biogas production for both reactors. There was an increase in chemical oxygen demand (COD) with hydraulic retention time due to increased contact time. The second part of the study focused on anaerobic co-digestion to produce volatile fatty acid (VFA) due to its higher value. The impact of substrate ratio of primary sludge (PS) and external organic waste (OW) and the robustness of the VFA system in the long term were assessed. Lab-scale batch study with different proportions of PS and OW; 0%, 25%, 50%, 75%, 100% of OW in terms of COD and scaled up in a semi-continuous pilot reactor with substrate ratio of 50% OW based on the results of the lab-scale study were performed. There was an increase in VFA production with an increase in OW proportion due to the availability of biodegradable organics. Acetic acid was the most dominant VFA in the batch reactors while in the semi-continuous experiment, caproic acid was dominated (50%). As carbon sources, the VFA-rich liquid attained the highest specific denitrification rate when compared with acetate and methanol.
I kommunala avfallsströmmar finns det en stor potential för resursåtervinning på grund av det höga organiska innehållet vilket kan användas för biobaserade produkter. På grundval av detta så fokuserar denna studie på resursåtervinningen av kol från kommunala avfallsströmmar genom att undersöka nuvarande och nytillkomna tekniker för att få vattenreningssystem att också bli resursåtervinningssystem. Första delen av studien undersöker relationen mellan metanproduktion och karaktäriseringen av anaerobiska granuler med ändamålet att förbättra energiproduktionen genom direkt behandling av kommunalt avloppsvatten. För detta ändamål så användes två UASB (Upflow Anaerobic Sludge Blanket) pilotreaktorer. Reaktorerna kördes med olika stora granuler, olika temperaturinställningar och olika hydrauliska uppehållstider (HRTs). Storlek, mikrobiell struktur, intern mikrostruktur och specifik metanogenaktivitet av de anaerobiska granulerna analyserades. Granulerna i UASB1 var 3-4 mm stora med interna multilager av mikrostrukturer som bestod av acetoklastika-metanogen arkéer. Granulerna i UASB2 var 1- 2 mm stora utan interna multilager och bestod av hydrogenotrofa metanogener. Aktiviteten i granulerna i UASB1 var 250-437 mL CH4 /g VS·d och i UASB2 var det 150-260 mL CH4 /g VS·d, vilket bekräftar att de acetoklastisk-metanogesa var mer effektiva i UASB1 än de hydrogenotrofa i UASB2. Att öka temperaturen från 20 o C till 28 o C under försöket medförde ingen förändring av den mikrobiologiska strukturen, men gav en ökning i biogasproduktion i UASB1 och högre och stabilare biogasproduktionshastighet i UASB2. Ökningen av biogasproduktion berodde på en reduktion i metans löslighet i utflödet och stabilare metanogenes. Ökning i HRT resulterade i större reduktion av organiskt material mätt som kemisk syreförbrukning (COD) och större biogasproduktion på grund av längre kontakttid mellan substrat och mikroorganismer. Den andra delen av studien fokuserar på att utveckla ett tillvägagångssätt att få en anaerob rötning att producera flyktiga fettsyror (VFA) istället för biogas. Studien fokuserar på effekten som kvoten mellan substraten primärslam och externt matavfall (OW) har och hur robust VFA-systemet skulle vara i stor skala på lång sikt. Olika kvoter av primärslam och matavfall testades i labbskala i batchstudier med 0 %, 25 %, 50 %, 75 % och 100 % COD OW. Baserat på resultaten från labbskala så kördes 50% COD OW i ett semi-kontinuerligt pilotförsök. Batch-testerna i labbskala visade att högre % COD OW, gav högre VFA produktion på grund av högre koncentration av organiskt material. Ättiksyra var den mest förekommande VFAn i batch-testerna medan kapronsyra var högst förekommande (50%) i det semi-kontinuerliga försöket. Denitrifikationsförsök visade att VFA-rik vätska från pilotskalareaktorerna gav den högsta specifika denitrifikationshastigheten i jämförelse med acetat och metanol. Resultaten visar att värdefulla kolkällor kan återvinnas från kommunalt avfall genom anaerob behandling av kommunalt avloppsvatten och samfermentering av primärslam och matavfall.

QC 2020-06-15

In recent times there is an increasing interest in the quantification of the variation in soil organic carbon (SOC) in space and time. Quantification of this variation is important since SOC is important for many soil physical, chemical and biological properties and soil processes which lead to sustainable crop production in agricultural soil. In addition, SOC also helps to reduce the impacts of climatic change if it can be stored in soil for the long term in what is called “soil carbon sequestration”. The focus of the work included in this thesis is to model the space and time variation using both statistical as well as process/mechanistic models of SOC. In process modelling of SOC, the Rothamsted carbon model (RothC model) was used to assess the spatial and temporal changes in SOC. The RothC model can be used to simulate the variation of SOC over the time using readily available spatial data. Therefore, this research has (a) tested the application of mid infra red / partial least-square regression models (MIR/PLSR models) in predicting SOC in archived soil data in combination with newly collected SOC data; (b) assessed changes in SOC using legacy soil data as the baseline survey; (c) mapped the measurable SOC fractions related to RothC model at the catchment scale; (d) simulated SOC across a catchment with the RothC model using readily available spatial data; (e) calibrated the rate constants of the RothC model at the catchment scale using Bayesian inverse modelling. The first research chapter (chapter 3) concentrates on the development of MIR/PLSR models to predict total SOC in archived soil datasets in relation to legacy soil datasets. The legacy soil information can be used to assess the temporal changes of SOC if they are considered to be the baseline survey. However, the use of legacy soil data directly for comparison will not be possible due to differences in the laboratory method used to measure SOC (analytical) and in the sampling support (see chapter 4 for more details). Therefore, an attempt was made to predict total SOC for archived soil data which corresponds to a legacy soil dataset collected in year 2000 in combination with newly collected data in year 2010. A total of eight (8) different MIR/PLSR calibration models were developed to predict SOC in archived soils. In development of these models an attempt was made to select samples (n = 24) from archived soil data using different sampling strategies which were used in combination (spiking) with the newly collected dataset for year 2010. It was found that all developed calibration models performed well based on internal cross validation. However, the independent validation results revealed sample selection through the Kernnard Stone algorithm performed best compared to other approaches, e.g. conditional latin hypercube sampling. In practical terms, it is not possible to analyse a large number of soil samples in archives with traditional lab based methods. Therefore, development of effective and practical oriented MIR/PLSR models will be cost effective and save laboratory processing time in relation to the determination of total SOC in archived soil properties. Chapter 4 is focused on the assessment of the change in SOC at the catchment scale using legacy soil data as the baseline survey. In this chapter two main approaches were used to assess the change in SOC namely; design-based inference methods and model-based inference methods. It also demonstrated “how to get design-based estimates when the sampling design is non-probabilistic” which is common for most legacy datasets. Design-based inference was carried out to see the change in SOC after calculating the 95 % confidence interval around the mean for the considered soil-land use complexes (SLU). If the 95 % confidence intervals for a considered SLU complex overlap each other, then it was concluded that the change is statistically not significant at the 0.05 probability level. In the model-based approach digital soil mapping (DSM) techniques were utilized where linear mixed models (LMM) were used to map the changes in SOC across the catchment. This chapter also reported issues with legacy soil data when they are used as the baseline survey and some of the ways to overcome those issues. Both statistical inference methods revealed that there is a drop in SOC between the two surveys (year 2000 and year 2010). However, that drop was not reported as statistically significant at the 0.05 probability level for both inference methods. Chapter 5 is focused on mapping measurable fractions of the RothC model at the catchment scale. The measurable fractions of the RothC model were predicted based on MIR spectra acquired for the 2010 dataset using newly developed MIR/PLSR models from the Australian carbon research programme (SCaRP) lead by CSIRO (2009 – 2012). Even though there are many papers related to mapping SOC there are only very few papers that are available related to mapping of SOC fractions. According to the reviewed literature this is the first time that measurable fractions of SOC related to the RothC model have been mapped. For the mapping purposes three separate LMMs were used and developed models were validated with leave-one-out-cross validation. In addition, conditional sequential Gaussian simulations were carried out to assess the uncertainties related to predicted maps. Throughout this chapter it is discussed how these DSM outputs can be used as inputs to the RothC model in order to run it spatially. Finally chapter 6 and 7 are focused on process modelling of SOC with RothC model. Chapter 6 highlights different ways of running RothC model spatially across a catchment. As the first step, the RothC model was initialized across the landscape using different initialization methods. A novel approach was tested where temporal C inputs were predicted from MODIS derived NPP data. Once data is prepared simulations across landscapes were carried out with 50 model combinations. These different model combinations consisting of different rate constants (2 levels), methods of initialization (5 levels) and sources of C inputs (5 levels) were compared (2 × 5 × 5 = 50 model combinations). It was found that different methods of initialization resulted in statistically significant initial SOC pools that are used as part of the RothC model. Further, it revealed that at the end of the simulations, (after 10 years) total SOC was statistically different at the 0.05 probability level based on different combinations. Results highlighted that there is great potential to use satellite derived products as drivers for future modelling of SOC. In chapter 7 Bayesian inverse modelling was utilized to estimate the uncertainty of the rate constants of the RothC model. The RothC model was re-programmed and calibrated in a Bayesian context using the “DREAM” algorithm. Once the posterior probability density functions (PDF) for the four (4) rate constants were obtained, they were used to carry out simulations using the entire PDF. Simulated results show the uncertainty created due to uncertainty about the model rate constants. This is an important step since process models such as RothC are widely applied to assess the impact of future climatic scenarios in relation to SOC without any calibration or assessment of uncertainties of the simulations. According to reviewed literature this is the first application of DREAM algorithm in calibration of RothC model rate constants for a catchment scale dataset.

This scholarly research investigates synthesis of different Zr-MOFs and some of Al- MOFs and studies their charcateristics and applications in capture or separation of carbon dioxide. CO2 is consdered as a main gas in greenhouse gases which have caused global warming.This thesis takes into account of using modified synthesis and activation procedures toward improving MOF affinity to adsorb CO2 and reducing its heat of adsorption. Also, the dynamic adsorption capacities were calculated for some Zr-MOFs and Al- MOFs from breakthrough experiments.Zr-MOF, Zr-MOF-NH4, Zr-MOF-NH2, Zr-MOF-NO3, and Zr-MOF-NO2 were obtained during direct synthesis process while MIL-53, and amino-MIL-53 were synthesized according to previous procedures with some modifications in activation process and MIL-96 was synthesized and activated by a new procedure.A fine crystalline powder of Zr-MOF was solvothermally synthesized and activated by chloroform and methanol separately. Chloroform activation was more vigorous to enhance surface area; the BET surface area was 1434 m2 g-1 which is higher than that of samples in methanol activation and previously reported. The Zr-MOF was stable up to 753 K. Chloroform activated Zr-MOF presented CO2 adsorption capacity of 79 and 45 cc g-1 at 1 atm, 273 and 302 K, respectively. Also, the heat of CO2 adsorption was around 28 kJ mol-1. However, the separating factor of CO2/CH4 was higher for methanol activated Zr-MOF although the adsorption capacity was lower.Ammonium hydroxide was used as an additive in the synthesis process to modify the pore size. Zr-MOF-NH4-2 showed the largest pore size; it was 2.3 nm. It was found that this modification has a negative impact on the CO2 adsorption capacity at STP. However, the adsorption capacity increased at increasing pressure over 5 atm(8.63 mmol g-1 at 987 kPa) while the heat of adsorption was 22 kJ/mol (which was calculated at 1 atm at the coverage of 5- 29 cc/g). In addition, Zr-MOF-NH4-1 and Zr-MOF-NH4-3 were more selective to separate CO2 from CO2-CH4.Amino-Zr-MOF was thermally stable up to 623K. In addition, its surface area was lower than Zr-MOF-(Parent). On the other hand, CO2 adsorption capacity was higher, giving 100 cc g-1 (4.46 mmol) at 273K and 1 atm. Also, it showed 9 mmol g-1 at 273K and 988 kPa.Another modification in direct synthesis process was achieved using nitric acid as an additive or using NO2-functionalised linker. NO3-modified samples exposed thermal stability the same as Zr-MOF (Parent), they may be decomposed at 773K. However, Zr- MOF-NO2 decomposed at 623K. Nitric acid additives played a main role in enlarging the pore size and reducing crystal size. Zr-MOF-NO3 exposed lower CO2 adsorption at STP with increasing amount of the additives. Zr-MOF-NO3-1 and Zr-MOF-NO3-2 presented adsorption capacities of 61.4 and 57.9 cc g-1 respectively, while Zr-MOFNO3- 2 had the lowest heat of adsorption of 17.8 kJ/mol. Conversely, Zr-MOF-NO2 revealed an adsorption capacity of 74.7 cc g-1 and the heat of adsorption was 37 kJ/mol. However, Zr-MOF-NO3 samples exposed higher CO2 adsorption capacity at high pressure. Also, the selectivity of CO2/CH4 was the highest on Zr-MOF-NO3-2.Al-MOF exposed different thermal stability. MIL-53, MIL-96 and amino-MIL-53 were stable up to 773, 570, and 650K respectively. MIL-96 exposed higher CO2 adsorption as 124 cc g-1 at STP while amino-MIL-53 has lower value at 48 cc g-1. However, amino- MIL-53 demonstrated heat of adsorption of 28 kJ/mol. Also, MIL-53 displayed the highest dynamic adsorption (169 cc g-1 at 1 bar and 304K).

The European renewable energy directive 2009/28/EC (E.C. 2009) provides a legislative framework for reducing GHG emissions by 20%, while achieving a 20% share of energy from renewable sources by 2020. Perennial energy crops could significantly contribute to limit GHG emissions through replacing equivalent fossil fuels and by sequestering a considerable amount of carbon into the soil through the large amounts of belowground biomass produced. The objective of this study is to evaluate the effects of land use change that perennial energy crops have on croplands (switchgrass) and marginal grasslands (miscanthus). For that purpose above and belowground biomass, SOC variation and Net Ecosystem Exchange were evaluated after five years of growth. At aboveground level both crops produced high biomass under cropland conditions as well as under marginal soils. At belowground level they also produced large amounts of biomass, but no significant influences on SOC in the upper layer (0-30 cm) were found. This is probably because of the "priming effect" that caused fast carbon substitution. In switchgrass only it was found a significant SOC increase in deeper layers (30-60 cm), while in the whole soil profile (0-60 cm) SOC increased from 42 to 51 ha-1. However, the short experimental periods (for both switchgrass and miscanthus), in which land use change was evaluated, do not permit to determine the real capacity of perennial energy crops to accumulate SOC. In conclusion the large amounts of belowground biomass enhanced the SOC dynamic through the priming effect resulting in increased SOC in cropland but not in marginal grassland.

The European renewable energy directive 2009/28/EC (E.C. 2009) provides a legislative framework for reducing GHG emissions by 20%, while achieving a 20% share of energy from renewable sources by 2020. Perennial energy crops could significantly contribute to limit GHG emissions through replacing equivalent fossil fuels and by sequestering a considerable amount of carbon into the soil through the large amounts of belowground biomass produced. The objective of this study is to evaluate the effects of land use change that perennial energy crops have on croplands (switchgrass) and marginal grasslands (miscanthus). For that purpose above and belowground biomass, SOC variation and Net Ecosystem Exchange were evaluated after five years of growth. At aboveground level both crops produced high biomass under cropland conditions as well as under marginal soils. At belowground level they also produced large amounts of biomass, but no significant influences on SOC in the upper layer (0-30 cm) were found. This is probably because of the "priming effect" that caused fast carbon substitution. In switchgrass only it was found a significant SOC increase in deeper layers (30-60 cm), while in the whole soil profile (0-60 cm) SOC increased from 42 to 51 ha-1. However, the short experimental periods (for both switchgrass and miscanthus), in which land use change was evaluated, do not permit to determine the real capacity of perennial energy crops to accumulate SOC. In conclusion the large amounts of belowground biomass enhanced the SOC dynamic through the priming effect resulting in increased SOC in cropland but not in marginal grassland.