Rozprawy doktorskie na temat „Heterogeneous Catalysis - Organic Chemistry”

Nanoparticles are involved in a broad range of applications, including heterogeneous catalysis. Nanoparticles tend to quickly lose their well-defined shapes and facets due to aggregation under duress such as heat. A series of highly studied materials are explored as support materials for nanoparticle supports. These supports include metal-organic frameworks (MOF), graphene oxide (GO), and a MOF-PRGO (partially reduced graphene oxide) hybrid. The inclusion of a support with the palladium increased lifespan of the catalyst by separation of nanoparticles. The choice of support material not only allowed for supporting of palladium nanoparticles, but allowed for rational catalyst synthesis in order to design catalysts with improved catalytic activity. CO oxidation, vanillin hydrogenation, and Suzuki cross coupling were studied. For the CO oxidation reaction, a cerium-based MOF, Ce-MOF, is shown to increase activity of palladium nanoparticles by capturing reactant gases and acting as an oxygen reservoir that cycles between (III) and (IV) states while transferring oxygen to palladium nanoparticles at the Pd/Ce-MOF interface. A hybrid Ce-MOF-PRGO was synthesized to increase the surface area and acidity of Ce-MOF materials and was shown to be active for vanillin hydrogenation. Smaller rod-like Ce-MOF crystals were observed, indicating intercalation of crystals on GO. Zirconium-based MOF UiO-66-NH2 was acidified via incorporation of tungstophosphoric acid (HPW), which increased the selectivity of products by adjusting the mechanistic pathway. GO was partially functionalized with aromatic amines to improve the coupling of bromobenzene and phenylboronic acid. Small amounts of aromatic amines increased the Pd(0) content and decreased nanoparticle size.

The administration of enantiopure drugs brings advantages such as improved efficacy, more predictable pharmacokinetics and reduced toxicity from the point of view of the pharmaceutical area.[1] For this reason, a tremendous amount of supply and demand for enantiomeric pure compounds has been shown not only in market, but industry and academia.[2-4] According to the industry publication Genetic Engineering and Biotechnology News (GEN) in 2014, 22 billion dollars were accounted for enantiopure form of drugs such as Sovaldi® (Sofosbuvir), Crestor® (Rosuvastatin), and Advair® (fluticasone/salmeterol). The fact that one enantiomer can be pharmacologically effective whereas the other enantiomer can be inactive or display non-desirable activity, chiral resolution and asymmetric synthesis research has broken out in recent years to obtain one desired stereoisomer. Enormous amounts of well-organized and rationalized research results for higher enantiomeric selectivity and efficiency has been reported with diverse chiral ligands and transition metals in academia.[5-10] However novelty-driven results from academic area does not meet the requirement in industry field for the practical issue, especially tedious separation process that require high cost and effort. In addition, methodologies developed with privileged chiral ligands and transition metal complexes leave a concern like undesired residue of trace amount of toxic metals in the products. In this dissertation, two types of heterogeneous asymmetric catalyst were investigated to find the alternative that accommodates industrial requirement to obtain enantiomeric pure compounds and novelty-driven academic demands. Firstly, constructions of rationally designed metal organic frameworks (MOFs) using chiral BINOL-derived phosphoric acid ligands were achieved. Overall, catalytic reactions with ocMOFs showed lower enatioselectivity than their homogeneous counterparts, but one of the MOFs, ocMOF-1, was found to exhibit improved enantioselectivity than its homogeneous counterpart in the context of transfer hydrogenation reaction of benzoxazine. Lower enatioselectivity with ocMOFs was rationalized by the chiral environment change by the formation of frameworks in a computational study. In addition, self-supported heterogenization of chiral BINOL-phosphoric acid was achieved by the Yamamoto coupling reaction, and by using catalytically active ocPOP-1 having nanoscopic channels, enantioselectivity was obtained up to 48% in transfer hydrogenation of N-PMP ketimine. Although extension of substituent groups at 3, 3' positions was expected to bring enhanced steric hindrance and to influence to enantioselectivity positively, lack of spatially well-defined interactions induced by this chiral environment change might have lowered the enantiomeric selectivity of the catalytic reaction using ocPOP-1 than its counterpart.

La present tesi tracta sobre el desenvolupament de catalitzadors homogenis que contenen fragments poliaromàtics per facilitar el seu ancoratge en suports sòlids per aconseguir la fàcil separació i reciclatge del catalitzador. Es van triar els grups pirè, ja que és conegut que promouen interaccions aromàtiques fortes pi-pi per apilament en superfícies de carboni. En conseqüència, el treball s'ha centrat en els suports de carboni (nanotubs de carboni, òxid de grafè reduït i perles de carboni) com a suports sòlids per a aquesta estratègia d'ancoratge no covalent en suports sòlids. A més, s'ha explorat un sistema catalític bifàsic com una altra estratègia per al reciclatge i la reutilització de catalitzadors homogenis. Aquest sistema catalític bifàsic, que consisteix en líquids iònics (IL) i diòxid de carboni supercrític (scCO2), s'usa en la reacció de telomerització de 1,3-butadiè amb diòxid de carboni per produir ä-lactona en un flux continu.
La presente tesis trata sobre el desarrollo de catalizadores homogéneos que contienen fragmentos poliaromáticos que se han introducido con el objetivo de facilitar el anclaje en soportes sólidos para conseguir la fácil separación y el reciclaje del catalizador. Se eligieron grupos pireno, ya que es conocido que promueve interacciones aromáticas fuertes pi-pi por apilamiento en superficies de carbono. En consecuencia, el trabajo se ha centrado en los soportes de carbono (nanotubos de carbono, óxido de grafeno reducido y perlas de carbono) como materiales para esta estrategia de anclaje no covalente en soportes sólidos. Además, se ha explorado un sistema catalítico bifásico como otra estrategia para el reciclaje y la reutilización de catalizadores homogéneos. Este sistema catalítico bifásico, que consiste en líquidos iónicos (IL) y dióxido de carbono supercrítico (scCO2), se usa en la reacción de telomerización de 1,3-bytadieno con dióxido de carbono para producir ä-lactona en un flujo continuo.
The present thesis deals with the development of established homogeneous catalysts bearing polyaromatic fragments that would facilitate catalyst separation and recycling. Pyrene tags were chosen as it is a well-known antenna that promotes strong aromatic pi-pi stacking interactions onto carbon surfaces. Consequently, we focused our attention on carbon supports (carbon nanotubes, reduced graphene oxide and carbon beads) as solid supports for this noncovalent anchoring strategy on solid supports. In addition, a biphasic catalytic system as another strategy for the recycling and reuse of homogeneous catalysts is explored. This biphasic catalytic system consisting of ionic liquids (ILs) and supercritical carbon dioxide (scCO2) was used in the Pd-catalyzed telomerization reaction of 1,3-butadiene with carbon dioxide to yield ä-lactone in a continuous flow-manner.

There is an increasing necessity for the pharmaceutical industry to develop enantiomerically pure drugs. Up till now, production of enantiomerically pure molecules has been provided by harvesting them from plants or utilising homogeneous catalysis and biocatalysis. None of these methods are efficient means of production, and attention is now being directed towards heterogeneous enantioselective catalysis as the preferred technique. This is on account of the high product yield and ease of separation of catalyst from the reaction mixture. Over the past few decades, a great deal of research has been conducted into investigating the Ni catalysed hydrogenation of β-ketoesters and Pt catalysed hydrogenation of α-ketoesters. These are the most successful systems for enantioselective heterogeneous catalysis. However, they are unsuitable for industrial purposes due to the low thermal and mechanical stability of the modified surfaces. The main goal throughout this project has been the investigation of surface-confined covalent reactions. The motivation of this research is to develop enantioselective heterogeneous catalysis; covalent networks are believed to infer the necessary thermal and chemical stability required to chirally modify catalytic surfaces for docking interactions with reactant species. Covalent organic frameworks (COFs) on surfaces hold potential for a number of chemical applications, and not just in the field of heterogeneous catalysis; for example in areas such as molecular electronics and templating.

Heteropolyacids (HPAs), such as phosphotungstic acid (PTA) and phosphomolybdic acid (PMA), with the Keggin structure are well known as solid superacids with estimated pKa of -13. High acidity of HPAs enabled their use as highly active homogeneous catalysts. However, homogeneous catalysis has many drawbacks, e.g. difficult and expensive separation of the used catalyst from the reaction mixture and its recycling. Application of pure HPAs in heterogeneous catalysis is limited by their low surface area and solubility in polar solvents. For increasing their surface area, HPAs should be immobilized on solid support. The objective of this work is the development of an active and stable HPA-containing catalyst for synthesis of long chain alkylbenzenes, which are essential precursors in the manufacture of surfactants. To prevent leachability of HPA from the support, it was covalently bonded into the silica matrix via Si‑O‑W bridges. The catalysts were obtained by co-condensation of tetraethoxysilane (TEOS) with PTA using sol-gel method in the presence of various surfactants as pore-forming agents. The synthesis was conducted by simultaneous addition of 20% HCl and ethanol solution of a mixture of TEOS and PTA to a solution of a surfactant. The reaction mixture was refluxed for 24 h. The obtained product was filtered, washed, air-dried, and calcined for total removal of a surfactant from pores. Use of Pluronic P123 as a non-ionic pore-forming agent produced the most acidic material. The synthesized mesoporous materials were tested as heterogeneous catalysts in liquid-phase alkylation of mesitylene by long-chain alkenes. They demonstrated higher activity than well-known zeolite HY. The analysis of catalyst recovered after the alkylation indicated no PTA leaching from silica matrix. Obtained superacidic mesoporous materials can potentially replace hazardous liquid Lewis acids currently used for long-chain alkylbenzene synthesis in petrochemical industry.

Nowadays, the modern chemical industry has to deal with increasing environmental concerns, including the disposal of waste and its economic impact, or the diminution of important worldwide resources such as transition metals. In this Ph.D. thesis, we aimed to bring improvement in this area by the development of green processes, based on the use of recyclable heterogeneous catalysts. By combining the catalytic properties of several metal cations with the properties of solid catalysts such as polyoxometalates or zeolites, we were able to set up new tools for organic synthesis. Silver-doped polyoxometalates proved to be very efficient catalysts in the rearrangement of alkynyloxiranes to furans. Acetals and spiroketals were synthetized by dihydroalkoxylation of alkynediols under catalysis with silver-zeolites. As a perspective, we highlighted the potential applications of such green procedures in the total synthesis of more complex molecules. The first results suggested that these environmental friendly processes should gain increasing interest in the future.

Heterogeneous catalysts are key materials in research and industry. Herein we study two materials in different stages of development toward being applied as heterogeneous catalysts. First, MoO3SnO2 was synthesized and studied as a catalytic system similar to Sn-beta zeolites. While the Mo-based catalyst did not show similar activity to Sn-beta, it did show interesting reactivity in activating carbonyls and oxidizing organic substrates. Second, a method was developed for grafting amines onto carboxylic acid functionalized carbon nanotubes for CO2 capture. The method was successful for grafting monomer ethylamine groups onto CNT and can be further developed to allow for polymeric amine groups to be grafted.

Metal organic frameworks have gained much attention due to their tunable pore sizes and very high surface areas. With the discovery many of these type materials the need has raised to look into new applications of theses porous frameworks. This thesis focuses on the synthesis of a new perovskite-type metal organic framework and measurement of its thermal conductivity in search of its applicability as a thermoelectric material. The second part of this work focuses on the synthesis of a metal organic framework incorporated with a Lewis pair for the first time. The optimum loading amount of the Lewis pair into the framework was also investigated.

The anthropogenic carbon dioxide (CO2) emission into the atmosphere, mainly through the combustion of fossil fuels, has resulted in a balance disturbance of the carbon cycle. Overwhelming scientific evidence proves that the escalating level of atmospheric CO2 is deemed as the main culprit for global warming and climate change. It is thus imperative to develop viable CO2 capture and sequestration (CCS) technologies to reduce CO2 emissions, which is also essential to avoid the potential devastating effects in future. The drawbacks of energy-cost, corrosion and inefficiency for amine-based wet-scrubbing systems which are currently used in industry, have prompted the exploration of alternative approaches for CCS. Extensive efforts have been dedicated to the development of functional porous materials, such as activated carbons, zeolites, porous organic polymers, and metal-organic frameworks (MOFs) to capture CO2. However, these adsorbents are limited by either poor selectivity for CO2 separation from gas mixtures or low CO2 adsorption capacity. Therefore, it is still highly demanding to design next-generation adsorbent materials fulfilling the requirements of high CO2 selectivity and enough CO2 capacity, as well as high water/moisture stability under practical conditions. Metal-organic frameworks (MOFs) have been positioned at the forefront of this area as a promising type of candidate amongst various porous materials. This is triggered by the modularity and functionality of pore size, pore walls and inner surface of MOFs by use of crystal engineering approaches. In this work, several effective strategies, such as incorporating 1,2,3-triazole groups as moderate Lewis base centers into MOFs and employing flexible azamacrocycle-based ligands to build MOFs, demonstrate to be promising ways to enhance CO2 uptake capacity and CO2 separation ability of porous MOFs. It is revealed through in-depth studies on counter-intuitive experimental observations that the local electric field favours more than the richness of exposed nitrogen atoms for the interactions between MOFs and CO2 molecules, which provides a new perspective for future design of new MOFs and other types of porous materials for CO2 capture. Meanwhile, to address the water/moisture stability issue of MOFs, remote stabilization of copper paddlewheel clusters is achieved by strengthening the bonding between organic ligands and triangular inorganic copper trimers, which in turn enhances the stability of the whole MOF network and provides a better understanding of the mechanism promoting prospective suitable MOFs with enhanced water stability. In contrast with CO2 capture by sorbent materials, the chemical transformation of the captured CO2 into value-added products represents an alternative which is attractive and sustainable, and has been of escalating interest. The nanospace within MOFs not only provides the inner porosity for CO2 capture, but also engenders accessible room for substrate molecules for catalytic purpose. It is demonstrated that high catalytic efficiency for chemical fixation of CO2 into cyclic carbonates under ambient conditions is achieved on MOF-based nanoreactors featuring a high-density of well-oriented Lewis active sites. Furthermore, described for the first time is that CO2 can be successfully inserted into aryl C-H bonds of a MOF to generate carboxylate groups. This proof-of-concept study contributes a different perspective to the current landscape of CO2 capture and transformation. In closing, the overarching goal of this work is not only to seek efficient MOF adsorbents for CO2 capture, but also to present a new yet attractive scenario of CO2 utilization on MOF platforms.

Understanding the supramolecular interactions governing the self-assembly of molecular building blocks upon surfaces is fundamental to the design of new devices such as sensors or catalysts. Successful heterogeneous enantioselective catalysts have relied upon the adsorption of ‘chiral modifiers’, usually chiral amino acids, onto reactive metal surfaces. One of the most researched examples is the hydrogenation of β-ketoesters using nickel-based catalysts. The stability of the chiral modifiers upon catalyst surfaces is a major obstacle to the industrial scale-up of this reaction. In this study, the replacement of conventional modifiers with porous, chiral and functionalised self-assembled networks is investigated. Perylene-3,4,9,10-tetracarboxylic diimide (PTCDI) and melamine (1,3,5-triazine,-2,4,6-triamine) have been shown to form hydrogen bonded networks on Ag-Si(111)√3x√3R30° in ultra-high vacuum (UHV) and Au(111) substrates in UHV and ambient conditions, these networks are capable of hosting guest molecules. These networks are investigated further in this study. In UHV, the behaviour of the components and network formation on Ni(111) is probed using scanning tunnelling microscopy (STM) and temperature-programmed desorption (TPD). The stability of the PTCDI-melamine network on Au(111) was analysed using TPD. Metal coordination interactions between each of the network components and nickel upon the Au(111) surface were examined by STM before testing the ability of the network to act as a template for metal growth. Finally, a number of polymerisation reactions are investigated with a view to replacing chiral modifiers with porous, chiral, functionalised covalent networks. Periodic covalent networks should possess the greater chemical and thermal stability required for more widespread use. In UHV and ambient conditions, STM is used to monitor the progress of surface-confined reactions on Au(111) and characterise the resultant covalent structures.

De nos jours, l’industrie chimique est de plus en plus confrontée à la question de son impact environnemental. Dans le même temps, elle doit faire face à la diminution des ressources de matières premières importantes tels que les métaux de transition, tout en respectant des contraintes économiques. Ces travaux de thèse avaient pour but de tenter de répondre à ces exigences, par le développement de méthodologies de synthèse basées sur l’utilisation de catalyseurs hétérogènes recyclables. En combinant les propriétés catalytiques de certains ions métalliques avec les propriétés de catalyseurs solides tels que les polyoxométallates ou les zéolithes, nous avons pu mettre au point de nouveaux outils pour la synthèse organique. Les polyoxométallates dopés à l’argent ont démontré leur efficacité dans le réarrangement d’alcynyloxiranes en furanes. La synthèse de spiroacétals et d’acétals par dihydroalkoxylation d’alcyne diols a été effectuée pour la première fois en catalyse à l’argent, via l’utilisation de zéolithes. En perspective, nous avons mis en évidence les applications potentielles de ces procédés verts dans la synthèse totale de molécules plus complexes. Les premiers résultats suggèrent que de telles synthèses plus respectueuses de l’environnement ont tout intérêt à être davantage utilisées à l’avenir
Nowadays, the modern chemical industry has to deal with increasing environmental concerns, including the disposal of waste and its economic impact, or the diminution of important worldwide resources such as transition metals. In this Ph.D. thesis, we aimed to bring improvement in this area by the development of green processes, based on the use of recyclable heterogeneous catalysts. By combining the catalytic properties of several metal cations with the properties of solid catalysts such as polyoxometalates or zeolites, we were able to set up new tools for organic synthesis. Silver-doped polyoxometalates proved to be very efficient catalysts in the rearrangement of alkynyloxiranes to furans. Acetals and spiroketals were synthetized by dihydroalkoxylation of alkynediols under catalysis with silver-zeolites. As a perspective, we highlighted the potential applications of such green procedures in the total synthesis of more complex molecules. The first results suggested that these environmental friendly processes should gain increasing interest in the future

Heterogeneous catalysis is the core of synthetic chemistry, with a significant impact on modern academic and industrial research. The excellent capabilities of accelerating the rate of reactions with low cost, high conversion, and product selectivity, along with the intrinsic recyclability nature of heterogeneous catalysts and their adaptability to continuous flow conditions enable their application in the development of efficient and sustainable processes. In this thesis the development and study of new heterogeneous protocols in organic synthesis are outlined, focusing on heterogeneous organocatalysis and solid inorganic acid catalysts applied in biomass valorisation process and APIs synthesis. In this context, an unprecedent N-heterocyclic carbene (NHC)-organocatalyzed fully regiodivergent protocol to access exo (2‐OH) and endo (5‐OH) monoacyl-isosorbides (MAIs) esters is described. Exo-selective strategy was successfully transferred into heterogeneous phase and applied to continuous-flow catalysis, through the fabrication and long-term operation of the corresponding packed-bed mesoreactor. In particular, the polystyrene-supported version of the selected NHC showed a catalytic activity comparable to that of the homogeneous counterpart in terms of both conversion efficiency (turnover number = 108) and regioselectivity (exo/endo up to 5.3). Our strategy in continuous flow conditions was successfully applied for the production of 2-benzoyl-IS (IS-5MN) which is the key intermediate in the synthesis of the commercial vasodilator isosorbide-5-mononitrate. Following, a novel N‐heterocyclic carbene (NHC)‐promoted regiodivergent protocol for exo (2‐OH) and endo (5‐OH) isosorbide (IS) imidates synthesis is also described. The employment of an immobilized‐NHC under heterogeneous conditions was assessed, showing satisfactory selectivity towards exo ‐MIIs (exo / endo = 3.8). Overall, the methodology presented provided an unprecedented collection of high value‐added products with potential applications in different fields. Following the imobilisation of organocatalysts onto solid supports, an unprecedented strategy for the immobilization of chiral 2,3-bisaminocyclopropenium salt (pre-catalyst) onto polystyrene and silica supports is presented together with a suitable procedure for the conversion into the corresponding cyclopropenimine Brønsted superbase bifunctional catalysts.The preferred silica-supported cyclopropenimine behaved very similarly to the soluble counterpart in the Michael addition reaction of glycine imine with different Michael acceptors (48-92% yield; 60-98% ee) and it could be utilized for the first time as packing material for the fabrication of fixed-bed mesoreactors (pressure-resistant stainless-steel columns). Continuous-flow experiments were performed with satisfactory long-term stability (24 h on stream) with unaltered conversion efficiency and enantioselectivity. Regarding the application of solid acid inorganic catalysts to bio-mass valorisation protocols, a study that combines techniques, including elemental analysis, nitrogen sorption and BJH, with NMR relaxation and diffusion techniques to study deactivation of SBA-15-pr-SO3H is presented. Combined, they shed light on and rationalise heterogeneous catalyst deactivation from humins deposition during Brønsted-acid catalysed alcoholysis of FOL to ethyl levulinate (EL) mediated by a series of SBA-15-pr-SO3H catalysts with tuned mesopore size. Finally, the synthesis in contnous flow conditions in a packed bed reactor of a wide range of N-substituted pyrrolidines, piperidines, and pyrroles, was proposed by the direct reaction of cyclic ethers or furans with primary amines over amorphous silica-alumina (ASA) as simple and readily available catalyst. The synthesis of 1-(4-bromo-2-fluorobenzyl)pyrrolidine, a key intermediate in the preparation of a histamine H3 receptor antagonist, was demonstrated.
La catalisi eterogenea è il fulcro della chimica sintetica moderna, grazie al suo significativo impatto sulla ricerca sia accademica che industriale. In particolare, l’impiego di catalizzatori eterogenei per lo sviluppo di nuovi di processi efficienti e sostenibili avviene in virtù delle caratteristiche dei catalizzatori eterogenei quali basso costo, alta conversione e selettività del prodotto, insieme all’intrinseca riciclabilità degli stessi e alla loro adattabilità a processi in condizioni di flusso continuo. Nel presente elaborato di tesi vengono delineati lo studio e lo sviluppo di processi eterogenei innovativi rilevanti nell’ambito della sintesi organica, con particolare approfondimento su organocatalisi eterogenea e catalizzatori acidi inorganici solidi applicati in processi di valorizzazione di biomassa e nella sintesi di molecole ad elevato interesse farmaceutico (API). In questo contesto, viene descritto un nuovo protocollo organocatalitico e altamente regioselettivo per la sintesi di esteri del diolo bio-based isosorbide. Il processo è incentrato sulla catalisi da carbeni N-eterociclici (NHC) e permette l’ottenimento di derivati eso (2-OH) e endo (5-OH) monoacil-isosorbide (MAI). La strategia eso-selettiva è stata trasposta con successo in fase eterogenea e applicata ad un processo a flusso continuo, attraverso la fabbricazione e l’utilizzo a lungo termine di un mesoreattore a letto fisso. In particolare, la versione in polistirene dell'NHC selezionato ha mostrato un'attività catalitica paragonabile a quella della controparte omogenea sia in termini di efficienza di conversione (TON = 108) che di regioselettività (eso/endo fino a 5,3). Tale processo di flusso continuo è stato applicato per la produzione di 2-benzoil-IS (IS-5MN) che è l'intermedio chiave nella sintesi del vasodilatatore commerciale isosorbide-5-mononitrato. Successivamente, lo studio di organocatalisi eterogenea è prosegue con lo sviluppo di nuovo protocollo regiodivergente promosso da NHC per la sintesi di imidati eso ed endo di isosorbide. Il Catalizzatore NHC immobilizzato su supporto solido è stato applicato in in condizioni eterogenee, mostrando una soddisfacente selettività verso exo-MII (exo / endo = 3,8). Nel complesso, la metodologia presentata ha fornito una libreria varia di prodotti ad alto valore aggiunto con potenziali applicazioni in diversi campi. In seguito, l’argomento di imobilizzazione di organocatalizzatori su supporti solidi viene ulteriormente approfondito presentando la prima strategia per l'immobilizzazione di ciclopropenimmine chirali, quali catalizzatori bifunzionali superbasi di Brønsted. 2,3-bisaminociclopropenimina supportata su silice è stata utilizzata come catalizzatore nel processo in flusso continuo per la reazione di addizione di Michael enantioselettiva fra glicinimmina e diversi accettori di Michael, ottenendo ottimi risultati in termini di conversione ed enantioselettività. La seconda parte della tesi riguarda l’applicazione di solidi acidi inorganici come catalizzatori eterogenei per processi di valorizzazione di bio-massa e produzione di molecole di interesse farmaceutico. Inizialmente, viene presentato uno studio che combina l’impego sinergico si tecniche diverse, tra cui analisi elementare, assorbimento di azoto e BJH, rilassamento e diffusione NMR, per studiare la disattivazione di SBA-15-pr-SO3H con diversa porosità durante la reazione di alcolisi catalizzata da acido di Brønsted di furfuryl alcohol (FOL) a levulinato di etile (EL). La disattivazione del catalizzatore è stata razionalizzata tramite la lo studio della formazione e diffusione di umine all’interno dei pori del catalizzatore in dipendenza alla grandezza dei pori stessi Infine viene descritto lo sviluppo di un efficiente processo in flusso per la sintesi di N-eterocicli in reattore a letto fisso tramite reazione diretta di eteri ciclici o furani con ammine primarie catalizzata da silice-allumina amorfa

Kyoto University (京都大学)
0048
新制・課程博士
博士(人間・環境学)
甲第21178号
人博第850号
新制||人||203(附属図書館)
29||人博||850(吉田南総合図書館)
京都大学大学院人間・環境学研究科相関環境学専攻
(主査)教授 吉田 寿雄, 教授 内本 喜晴, 教授 田部 勢津久
学位規則第4条第1項該当

Developing a fundamental understanding of the interactions between catalytic surfaces and adsorbed molecules is imperative to the rational design of new materials for catalytic, sorption and gas separation applications. Experiments that probed the chemistry at the gas-surface interface were employed through the utilization of in situ infrared spectroscopic measurements in high vacuum conditions to allow for detailed and systematic investigations into adsorption and reactive processes. Specifically, the mechanistic details of propene epoxidation on the surface of nanoparticulate Au supported on TiO2 and dimethyl chlorophosphate (DMCP) decomposition on the surface of TiO2 aerogel-supported Cu nanoparticles were investigated. In situ infrared spectroscopy illustrates that TiO2-supported Au nanoparticles exhibit the unprecedented ability to produce the industrially relevant commodity chemical, propene oxide, through the unique adsorption configuration of propene on the surface of Au and a hydroperoxide intermediate (-OOH) in the presence of gaseous hydrogen and oxygen. Whereas, TiO2-supported Cu aerogels oxidize the organophosphate-based simulant, DMCP, into adsorbed CO at ambient environments. Through a variety of spectroscopic methods, each step in these oxidative pathways was investigated, including: adsorption, oxidation and reactivation of the supported-nanoparticle systems to develop full mechanistic pictures. Additionally, the perturbation of vibrational character of the probe molecule, CO, was employed to characterize the intrinsic µ3-hydroxyls and molecular-level defects associated with the metal-organic framework (MOF), UiO-66. The adsorption of CO onto heterogeneous surfaces effectively characterizes surfaces because the C-O bond vibrates differently depending on the nature of the surface site. Therefore, CO adsorption was used within the high vacuum environment to identify atomic-level characteristics that traditional methods of analysis cannot distinguish.
Doctor of Philosophy

Two MOFs, [H2N(CH3)2][Zn3(TATB2(HCOO)]·HN(CH3)2·DMF·6H2O (1) and ZnHKUST-1 (2) (TATB = 4,4′,4″-s-triazine-2,4,6-triyl-tribenzoate) were investigated as potential hosts to encapsulate Fe(III) protoporphyrin IX (ferrihaem = Fe(III)PPIX) and Fe(III) tetraphenylporphyrin (Fe(III)TPP). Methyl orange (MO) adsorption was used as an initial model for substrate uptake in MOFs 1 and 2. MOF 1 showed good adsorption of MO (10.3 ± 0.8 mg.g-1 ) which could undergo in situ protonation upon exposure to aqueous HCl vapour. By contrast MO uptake by 2 was much lower (2 ± 1 mg.g-1 ) and PXRD indicated structural instability on exposure to water was the likely cause. Two methods for Fe(III)PPIX incorporation into 1 were investigated: soaking and encapsulation. Encapsulation was verified by SEM-EDS and showed comparable concentrations of Fe(III)PPIX on exposed interior surfaces and on the original surface of fractured crystals. SEM EDS results were consistent with ICP-OES data on bulk material (1.2 ± 0.1 mass % Fe). PXRD data showed that the framework in 1 was unchanged after encapsulation of Fe(III)PPIX. MO adsorption (6 ± 1 mg.g1 ) by Fe(III)PPIX-1 confirmed there is space for substrate diffusion into the framework, while the UV-visible spectrum of solubilized crystals confirmed that Fe(III)PPIX retained its integrity. A solid-state UV-visible spectrum of Fe(III)PPIX-1 indicated that Fe(III)PPIX was not in a µ-oxo dimeric form. Although single-crystal XRD data did not allow for full refinement of the encapsulated Fe(III)PPIX molecule owing to disorder of the metalloporphyrin, the Fe atom and pyrrole N atoms were located, enabling rigid-body modelling of the porphine core. For comparison, Fe(III)PPIX was further encapsulated in 2, forming Fe(III)PPIX-2. Reaction ABSTRACT of 2,2'-azino-bis(3-ethylbenzothiazoline)-6-sulphonic acid (ABTS) with H2O2, catalysed by Fe(III)PPIX-1 and -2 showed that Fe(III)PPIX-1 is significantly more efficient than Fe(III)PPIX-2 and is superior to solid Fe(III)PPIX-Cl due to the faster initial rate of reaction as well as the greater conversion of ABTS to ABTS●+ . Both frameworks 1 and 2 were also investigated as potential hosts to encapsulate Fe(III) tetraphenylporphyrin (Fe(III)TPP). Attempts to encapsulate Fe(III)TPP into 1 were unsuccessful, but Fe(III)TPP was successfully encapsulated into 2, forming Fe(III)TPP-2. The framework was characterised by PXRD and SEM-EDS confirmed uniform distribution of Fe(III)TPP through the framework. The loading of Fe(III)TPP determined using ICP-OES (0.604 ± 0.008 Fe mass %) agreed well with SEM-EDS data. Single crystals of Fe(III)TPP-2 were obtained and structure determination showed that the Fe(III) porphyrin was positionally disordered over three positions. The instability of Fe(III)TPP-2 in the presence of H2O resulted in it being an inappropriate choice as an oxidation catalyst. The kinetics of ABTS oxidation by H2O2 catalysed by Fe(III)PPIX-1 were further investigated. The peroxidatic activity of this heterogeneous system conforms to a rate law identical to that observed in solution with no discernible influence of particle size, suggesting that the MOF system closely mimics the solution state. The proposed rate law indicates a reaction mechanism with two possible pathways, as suggested for the same reaction in solution. The major pathway describes the coordination of H2O2 to the Fe(III) centre and subsequent formation of a high valent intermediate, while the minor pathway describes the same process preceded by ABTS coordination to the Fe(III) centre forming a six-coordinate complex. The further application of Fe(III)PPIX-1 as an oxidation catalyst was probed by investigating the catalytic oxidation of hydroquinone, thymol, benzyl alcohol and phenyl ethanol by tert-butyl-hydroperoxide ( tBuOOH). Reactions were successful and showed t1/2 values that increase with increasing substrate molecular volume.

Over the last two centuries, the discovery and application of catalysts has had a substantial impact on how and what chemicals are produced.Given their broad significance, our group has focused on developing new catalyst systems that are recoverable and reusable, in an attempt to reduce concomitant costs. Our efforts have centered on constructing a recyclable chiral heterogeneous catalyst capable of effecting asymmetric hydrogenations of olefins with high stereoselectivity. A class of phosphinoimidazoline ligands, developed by researchers at Boehringer-Ingelheim, known as BIPI ligands, have proven efficacious in the asymmetric reduction of alkenes. However, these chiral ligands are homogeneous and coordinated to precious metals, rendering them irrecoverable and expensive. To address these issues, our group has derivatized the BIPI ligand-metal complex and immobilized it to the surface of graphene oxide as well as polystyrene. Their efficacy and recyclability toward the asymmetric hydrogenation of a functionalized olefin have been evaluated. Another facet of our work has included developing a cost effective synthetic process to artemisinin, the gold standard drug in the treatment of malaria.As a natural product, artemisinin’s worldwide supply remains highly unpredictable, contributing to great price volatility.Combining the benefits of catalysis and the advantages of continuous flow chemistry, our research has sought to develop an economical approach to convert a biosynthetic precursor, artemisinic acid, to artemisinin in three chemical transformations. High-throughput experimentation allowed us to screen a prodigious number of catalysts and identify those effective in the asymmetric hydrogenation artemisinic acid to dihydroartemisinic acid, the first step in the transformation. This screening directed us to an inexpensive, heterogeneous ruthenium catalyst. The second step of the process includes the photooxygenation of dihydroartemisinic acid, which involves photochemically generated singlet oxygen. We have evaluated a commercially available heterogeneous photocatalyst packed in a transparent bed, surrounded by light emitting diodes in the continuous photooxygenation of dihydroartemisinic acid to dihydroartemisinic acid hydroperoxide. The third and final step, an acid induced hock cleavage, initiates an intricate cascading reaction that installs an endoperoxide bridge to deliver artemisinin. Our process afforded a 57% yield from dihydroartemisinic acid to artemisinin.

With the dwindling availability of petroleum, focus has shifted to renewable energy sources such as lignocellulosic biomass. Lignocellulosic biomass is composed of three main constituents, lignin, cellulose and hemicellulose. Due to the low value of cellulosic ethanol, utilization of the lignin component is necessary for the realization of an economically sustainable biorefinery model. Once depolymerized, lignin has the potential to replace petroleum-derived molecules used as bulk and specialty aromatic chemicals. Numerous lignin depolymerization strategies focus on cleavage of β-aryl ether linkages, usually at high temperatures and under reductive conditions. Alternatively, selective benzylic oxidation strategies have recently been explored for lignin and lignin models. In this work, heterogeneous catalytic methods using supported base metals and layered-double hydroxides were evaluated for the oxidation of lignin models both before and after benzylic oxidation. Additionally, by studying putative reaction intermediates, insights were gained into the mechanisms of oxidative fragmentation of the model compounds. Generally, it was found that after benzylic oxidation models were more susceptible to oxidative fragmentation. Indeed, several heterogeneous oxidation systems were found to convert lignin models to oxygenated aryl monomers (mainly benzoic acids and phenols) using inexpensive primary oxidants (i.e., hydrogen peroxide and molecular oxygen). Reactions were conducted at relatively mild temperatures and at low oxygen concentrations for the purpose of an easy transition to large-scale experiments. Finally, the catalytic systems that resulted in significant cleavage of lignin models were applied to a Kraft lignin. Oxidation of Kraft lignin resulted a mixture of products for which analytical data and increased solubility are consistent with interunit cleavage within the lignin macromolecule.

The purpose of this doctoral thesis is to investigate and develop catalytic processes mediated by iridium(III) complexes. By understanding the mechanisms, the weaknesses of the designed catalysts can be identified and be overcome in the following generation. The thesis is composed of two general sections dedicated to the synthesis and applications of homogeneous catalysts and to the preparation of heterogeneous catalysts based on metal-organic frameworks (MOFs). After a general introduction (Chapter 1), the first part of the thesis (Chapters 2-4, and Appendix 1) covers the use of several homogeneous bifunctional [Cp*Ir(III)] catalysts in a variety of chemical transformations, as well as mechanistic studies. Chapter 2 summarizes the studies on the N-alkylation of anilines with benzyl alcohols catalyzed by bifunctional Ir(III) complexes. Mechanistic investigations when the reactions were catalyzed by Ir(III) complexes with a hydroxy-functionalized N-heterocyclic carbene (NHC) ligand are discussed, followed by the design of a new generation of catalysts. The chapter finishes presenting the improved catalytic performance of these new complexes.    A family of these NHC-iridium complexes was evaluated in the acceptorless dehydrogenation of alcohols, as shown in Chapter 3. The beneficial effect of a co-solvent was investigated too. Under these base-free conditions, a wide scope of alcohols was efficiently dehydrogenated in excellent yields. The unexpected higher activity of the hydroxy-containing bifunctional NHC-Ir(III) catalysts, in comparison to that of the amino-functionalized one, was investigated experimentally. In the fourth chapter, the catalytic process presented in Chapter 3 was further explored on 1,4- and 1,5-diols, which were transformed into their corresponding tetrahydrofurans and dihydropyrans, respectively. Mechanistic investigations are also discussed. In the second part of the thesis (Chapter 5), a Cp*Ir(III) complex was immobilized into a MOF. The heterogenization of the metal complex was achieved efficiently, reaching high ratios of functionalization. However, a change in the topology of the MOF was observed. In this chapter, the use of advanced characterization techniques such as X-ray absorption spectroscopy (XAS) and pair distribution function (PDF) analyses enabled to study a phase transformation in these materials.

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Submitted.

Cette thèse porte sur l’immobilisation de catalyseurs moléculaires à la surface de nanotubes de carbone. Différentes stratégies ont été utilisées, à l’aide de molécules amphiphiles comprenant un motif di-acétylènique ou à l’aide de molécules amphiphiles polyaromatiques comprenant un motif pyrène. Ces assemblages ont été caractérisés par électrochimie dans différentes conditions afin d’évaluer les performances en oxydation d’hydrogène. L’assemblage utilisant un motif polyaromatique a ensuite été introduit en dispositif de pile complète avec électrolyte afin de caractériser les performances de la pile, avec et sans platine. Les résultats obtenus sont prometteurs et permettent une nouvelle vision de l’optimisation des électrodes
This thesis deals with the immobilization of molecular catalysts on the surface of carbon nanotubes. Different means have been used, using amphiphilic molecules containing a diacetylenic moiety and using polyaromatic amphiphilic molecules containing a pyrene moiety. These assemblies have been characterized by electrochemistry under different conditions in order to characterize the performances in hydrogen oxidation. The assembly using a polyaromatic moiety was then introduced as a complete fuel cell device with electrolyte to characterize the performance of it, with and without platinum. The results obtained are promising and allow a new vision of electrode optimization

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
The heterogeneous catalysis is a promising alternative to solve the environmental problems found in homogeneous catalysis, because it allows the continuous use of the catalyst until its deactivation and minimizes the generation of effluents. Thus, this work aims to synthesize, optimize and evaluate the activity of heterogeneous catalysts, using PET bottles as a starting material in the synthesis of the active phase and SiO2 as catalyst support for the transesterification reaction of soybean oil. The the catalysts were obtained by a impregnating reaction using methanol. The active phase, the catalysts and catalyst support were characterized by X-ray diffraction (XRD), infrared (IR), Raman spectroscopy, scanning electron microscopy (SEM) and EDS, thermal analysis (TG) and measurement surface area (BET). The biodiesels has been synthesized using a molar ratio of 1:9 (soybean oil: methanol), 0,1 g of active phase as catalyst (room temperature) and 1,2 g of the catalysts synthesized at 75 °C, where its kinematic viscosities were measurements. All catalysts were effective in the synthesis of biodiesel because the viscosity reduction of soybean oil used was very significant, indicating that may have occurred the transesterification process, among all biodiesels synthesized the catalyst that stood out was the 30%-K2CO3/70% SiO2, which was obtained greater viscosity reduction at a lower reaction time. The quality tests were made for 1h Bio-30%, which proved be inside the parameters established by the Agência Nacional de Patróleo (ANP). The experiment reuse of the catalyst used in the synthesis of Bio-1h 30%, showed that the catalytic activity is reduced due to possible leaching phenomenon, then preliminary studies have been proposed to study the possible leaching of the active phase.
A catálise heterogênea é uma alternativa promissora para resolver os problemas ambientais encontrados na catálise homogênea, pois permite o uso continuo do catalisador até sua desativação e minimiza a geração de efluentes. Neste sentido, este trabalho visa em sintetizar, otimizar e avaliar a atividade de catalisadores heterogêneos, utilizando a garrafa PET pós-consumo como matéria prima na síntese da fase ativa e SiO2 como suporte catalítico para a reação de transesterificação com óleo de soja. Os catalisadores foram obtidos pela o método de impregnação utilizando o metanol como solvente. A fase ativa, os catalisadores e o suporte catalítico foram caracterizados por difração de raios-X (DRX), espectroscopia na região do infravermelho (IV), espectroscopia Raman, microscopia eletrônica de varredura (MEV) e EDS, análise térmica (TG), e medida de área superficial (BET). Os biodieseis foram sintetizados utilizando uma razão molar de 1:9 (óleo de soja: metanol), 0,1 g da fase ativa como catalisador a temperatura ambiente e 1,2 g dos catalisadores sintetizados a 75 °C, onde suas viscosidades cinemáticas foram medidas. Todos os catalisadores foram efetivos na síntese do biodiesel, pois promoveu a redução de viscosidade do óleo de soja utilizado, no qual mostrou um indicativo que a reação de transesterificação ocorreu, dentre todos os biodieseis sintetizados o catalisador que mais se destacou foi o 30%-K2CO3/70%-SiO2, onde obteve-se a maior redução de viscosidade com um menor tempo reacional. Os testes de qualidade foram feitos para o Bio 1h-30%, o qual mostrou estar dentro dos parâmetros estabelecidos pela Agência Nacional de Petróleo (ANP). O experimento de reuso do catalisador utilizado na síntese do Bio 1h-30%, mostrou que a atividade catalítica é reduzida devido ao possível fenômeno de lixiviação, então estudos preliminares foram propostos para estudar a possível lixiviação da fase ativa.

In recent years Green Chemistry has become a central area of research for chemists working in both industry and academia. The fundamental concepts of sustainable chemistry are, among others, atom efficiency, waste prevention, use of renewable materials and innocuous solvents, as well as design of safer products. Within this context, microreactor technology offers, on the one hand, safe, environmentally benign, and high throughput processes typically intensified by a fast postreaction phase (workup and purification) and direct scalability; on the other hand, asymmetric organocatalysis allows for new and unique opportunities towards efficient and highly stereoselective metal-free catalytic syntheses. In the first part of this thesis project it has been carried out the synthesis of new heterogeneous organocatalysts for their ultimate utilization in continuous-flow processes. Precisely, proline-like mimetics and thiazolium salt pre-catalysts have been immobilized on silica and polystyrene macroporous supports, respectively; next, these functionalized solid materials have been employed as packing material for the fabrication of fixed-bed microreactors in the form of either packed or monolithic columns. During this research, it has been demonstrated that operation of this type of organocatalytic microreactors results in flow processes with levels of stereoselectivity comparable to those of the corresponding homogeneous batch processes, allowing at the same time productivity enhancements thanks to the higher long-term stability of the heterogeneous organocatalytic species in flow regime. In the second part of this thesis project, the same techniques of support functionalization have been employed to prepare perfluorinated stationary phases for the determination of perfluorinated compounds (PFCs). These are emerging pollutants widely spread in the environment. They can be found in soils, sediments, superficial waters, particulate matter, as well as in animal and human tissues or organs. PFC are characterized by environmental persistence and have negative side effects for the biota where they accumulate. The chromatographic behavior of perfluorinated acid pollutants have been investigated on the basis of the specific fluorine-fluorine interactions (fluorophilicity) occurring between these analytes and the perfluoroalkyl groups of the newly prepared stationary phases. It has been demonstrated that the retention profile of perfluorinated acids is dependent on the composition of the mobile phase, thus permitting the use of the prepared fluorinated stationary phases as means of pre-concentration of PFCs from environmental and biological matrices.

Copper is an inexpensive, earth-abundant, non-toxic metal that is found to have widespread applications in catalysis. Ullmann and Ullmann-type reactions and Glaser-Hay oxidative coupling of terminal alkynes are some of the well-established copper catalyzed coupling reactions used for the construction of important organic molecules, including pharmaceuticals, commodity chemicals and polymers. Those reactions have been mainly performed homogeneously, where the removal of residual copper from the reaction mixture is a challenge. Therefore, many researchers tried supporting copper precatalysts in order to help recover, and thus reduce final product contamination. Some studies showed that copper leached significantly from the support, with others showing that leached copper has a role in the catalysis. Nevertheless, many studies reported that the used supported catalysts were recyclable and claimed catalyst's heterogeneity. In most cases, the nature of the truly active copper species is still not clear. The objectives of this thesis were (1) to assess the heterogeneity/homogeneity of active copper species in popular catalytic C-N coupling reactions with already studied catalysts, mainly a copper exchanged zeolite and copper oxide nanoparticles, and (2) to use the collected information in designing a truly heterogeneous (stable and recyclable) catalyst. Initially, and because of its shape selectivity characteristics, copper-exchanged NaY zeolite, Cu(II)Y, was chosen to study the heterogeneity of copper catalyzed amination of aryl iodide with imidazole. The collected results from conducted shape selectivity tests indicated that Cu(II)Y might be heterogeneous catalyst, but because of the used base, that is crucial for this C-N coupling reaction, the crystallinity of the zeolite structure was diminished. Therefore, it was important to support copper on a framework that is stable under the basic conditions required for this type of reaction if a heterogeneous, recyclable catalyst were to be achieved. For this purpose, cerium oxide was chosen, and copper oxide supported on cerium oxide, CuO-CeO₂, was investigated as a potential heterogeneous catalyst for C-N coupling reaction. This investigation included the role of each reaction reagent in facilitating copper leaching into solution. It was found that copper leached from the support and it was demonstrated through hot filtration tests that the leached copper species was the main active catalyst. Leaching was caused by the solvent (DMSO) as well as the used reactants and the base. Similar conclusions were drawn when this CuO-CeO₂ catalyst was used for the direct synthesis of imines from amines under aerobic conditions. Although this CuO-CeO₂ catalyst has the advantages of being more recoverable and active than unsupported CuO nanoparticles at similar copper loadings, it is not fully recyclable, as the copper catalysis occurs in solution. These findings meant that designing a truly heterogeneous catalyst for this reaction is a challenging task. Understanding the effect of each individual factor of this complicated system might help in achieving the second goal - designing a truly heterogeneous catalyst. Therefore, further studies were carried out to understand the effect of reaction conditions, including temperature, base, support, and solvent, on copper leaching. Homocoupling of terminal alkynes was chosen as a model reaction for this study, and CuO was supported on TiO₂ (10CuO-TiO₂) and on γ-Al₂O₃ (10CuO-Al₂O₃). It was found that copper interaction with the support affects the extent of leaching as well as the nature and activity of leached species. High temperature also facilitates copper leaching especially when a ligating amine, like piperidine, is present in the system.

The preparation, testing and characterisation of catalysts for the total oxidation of two volatile organic compounds (VOCs) have been studied. These two VOCs were naphthalene and propane. Naphthalene was the main focus of this study. CeZrC>2 with varied Ce:Zr ratios and preparation methods was investigated for the total oxidation of naphthalene. These preparation methods were all precipitation methods using different precipitating agents (urea, sodium carbonate and supercritical CO₂). Zr contents as low as 1 molar percent enhanced activity for both urea and sodium carbonate precipitated catalysts compared to CeC>2. A supercritical analogue was found to be less active. Pt/SiC>2 as a catalyst for naphthalene total oxidation was studied with a view to optimise an existing impregnation technique. A Pt loading of 2.5wt% with a calcination regime of 550 °C for 12h in static air with a ramp rate of 5 °C/min was found to be optimal. These preparation conditions were found to increase the proportion of metallic Pt which was found to exist as large crystallites with low dispersion. Other catalyst features were probed in this study. The type of silica used as a support was changed to novel hollow sphere silica then nanopore silica but no improvement in activity was found. Pt was then substituted for Pd which again did not improve activity. It was found that the Pd existed as Pd oxide hence Pd oxide is not as active for naphthalene oxidation as metallic Pt. The preparation of impregnated catalysts using non-aqueous solvents on so-called 'hydrophobic' materials was also investigated. These were tested for both naphthalene and propane total oxidation. It was found that Pt and Pd based catalysts afforded the most active catalysts. Several supports were studied which interacted with the impregnated metals in different ways. This affected the nature of the impregnated metals and therefore the activities of these catalysts. Some of the more active catalysts used supports that were of a low surface area. A high surface area SnO₂ support was produced and impregnated with Pd. The high surface area SnO₂ was found to be more active than the original Pd/SnO₂ catalyst for propane total oxidation.

A combination of Temporal Analysis of Products, Temperature Programmed Reduction, and Density Functional theory techniques have been used to perform kinetic analysis on data from heterogeneous catalysis experiments. A new method of data filtering has been developed for Temporal Analysis of Products, and has been applied to a system of 4 Pt−Mo2C, and the current methodology has been expanded upon to calculate rate coefficients for the oxidation of CO to CO2 via the Boudard reaction. From the kinetic constants it appears that a phase change occurs in the material at approximately 200�C. The current theory for analysing Temperature Programmed Reduction has been applied in a new methodology which is able to perform the deconvolution of thermograms with high accuracy, while also calculating the kinetic parameters related to the reduction processes. This new methodology has been applied to a system of CeO2 calcined at 400, 500 and 600�C and the strengths and limitations of the methodology are explored. From the deconvolution procedure it was found that there are three distinct reduction processes occurring on the CeO2 and that a phase change occurs between 400 and 500�C. Finally Density Functional Theory combined with classical dynamics has been used to explore the mechanism of the hydrogenation of Levulinic Acid to gamma-Valerolactone over a CuZrO2 catalyst. It was found that the Levulinic Acid is more likely to hydrogenate then cyclise, and from using molecular dynamics simulations it was shown that the solvent H2O plays a very important role in the cyclisation of the hydrogenated intermediate.

En la present tesi s’han emprat tècniques computacionals per investigar la utilització de materials basats en òxids de metalls de transició amb estructura de rutil com a catalitzadors per a compostos halogenats. Els estudis exploren la interacció entre l’estructura i composició de la superfície, l’activitat catalítica i la selectivitat de formació de productes. El treball se centra en diòxids de ruteni i titani com catalitzadors per les reaccions d’oxidació d’halurs d’hidrogen i oxicloració d’etilè. Els càlculs amb la teoria del funcional de la densitat demostren com pot tindre lloc la substitució d’oxígens superficials, sota condicions de reacció per la oxidació d’halurs d’hidrogen. Particularment, una important absorció de brom va ser determinada en òxid de ruteni, amb la substitució de brom extenent-se des de la superfície fins les capes sub-superficials, i introduint una gran reorganització estructural de la superfície. Per tant, es proposa que el mecanisme de reacció estigui estretament vinculat al grau de substitució a la superfície. Les investigacions també examinen sistemes basats en diòxids de titani dopats. Ha estat explorada la relació entre els defectes a l’estructura electrònica induïts pel dopant, i l’activitat catalítica cap a processos elementals associats a l’oxidació d’halurs d’hidrogen. Particularment, ha estat determinat que es pot realitzar una elecció racional del dopant per optimitzar el nombre de defectes, i les seves energies associades, amb la finalitat de modificar de forma acurada l’estructura electrònica de la superfície, i així, obtenir una activitat òptima. Finalment, el diòxid de ruteni es investigat com un potencial catalitzador per a la oxicloració d’etilè. Es va determinar que la competició entre els processos de combustió i oxicloració es millorada pel confinament dimensional dels adsorbats sobre la superfície del catalitzador, i que el recobriment superficial és un factor essencial per determinar la viabilitat de certs processos elementals, i així, la selectivitat dels productes. La tesi proporciona una clara visió general dels rutils com catalitzadors per la química dels halògens. A més, també proporciona coneixements detallats que poden ser utilitzats per al desenvolupament de millors catalitzadors al futur.
En la presente tesis se han empleado técnicas computacionales para investigar el uso de materiales basados en óxidos de metales de transición con estructura de rutilo como catalizadores para la química de halógenos. Los estudios exploran la interacción entre la estructura y composición de la superficie, la actividad catalítica y la selectividad de los productos. El trabajo se enfoca en sistemas basados en dióxidos de rutenio y titanio como catalizadores para las reacciones de oxidación de haluros de hidrógeno y oxicloración de etileno. Los cálculos con métodos de la teoría del funcional de la densidad muestran como, bajo condiciones de reacción para la oxidación de haluros de hidrógeno, la sustitución de oxígenos superficiales puede tener lugar. Particularmente, una importante absorción de bromo fue encontrada en dióxido de rutenio, con la sustitución de bromo extendiéndose desde la superficie hacia las capas subsuperficiales, e induciendo una gran reorganización estructural de la superficie. Por lo tanto, se propone que el mecanismo de reacción está estrechamente vinculado al grado de sustitución en la superficie. Las investigaciones también examinan sistemas basados en dióxidos de titanio dopados. La relación entre los defectos en la estructura electrónica inducidos por el dopante, y la actividad catalítica hacia procesos elementales asociados con la oxidación de haluros de hidrógeno, es explorada. Particularmente, se encontró que una elección racional del dopante puede ser realizada para optimizar el número de defectos, y sus energías asociadas, con la finalidad de modificar de forma precisa la estructura electrónica de la superficie y, así, obtener una actividad óptima. Finalmente, se investigó el dióxido de rutenio como un potencial catalizador para la oxicloración de etileno. Se encontró que la competición entre los procesos combustión y oxicloración es mejorada por el confinamiento dimensional de adsorbatos sobre la superficie del catalizador, y que la recubrimiento superficial es un factor esencial para determinar la viabilidad de ciertos procesos elementales y, así, la selectividad de los productos. La tesis proporciona una clara visión general de los rutilos como catalizadores para la química de los halógenos. Además, también proporciona conocimientos detallados que pueden ser usados para el desar
Computational techniques are applied to investigate the utility of rutile transition metal oxide based systems as catalysts for halogen chemistry. The studies explore the interplay between surface structure and composition, catalytic activity and product selectivity. The work focuses on ruthenium dioxide and titanium dioxide based systems as catalysts for hydrogen halide oxidation and ethylene oxychlorination reactions. DFT calculations show that under hydrogen halide oxidation conditions, replacement of surface oxygen atoms in the rutile catalyst can occur. In particular, significant bromine uptake was found to occur in ruthenium dioxide, with bromine replacement extending beyond the surface to the subsurface layers and inducing a major structural rearrangement at the surface. It is thus proposed that the reaction mechanism is closely linked to the extent of surface replacement. The investigations also examine doped titanium dioxide based systems. The relationship between dopant-induced electronic structure defect states, and the catalyst activity towards elementary processes associated with hydrogen halide oxidation, is explored. In particular, it was found that a judicious choice of dopant atom can be made to optimise the number of defect states, and their associated energies, in order to fine-tune the electronic structure of the system for optimal activity. Finally, ruthenium dioxide is investigated as a potential catalyst for ethylene oxychlorination. It was found that competition between combustion and oxychlorination processes is enhanced by dimensional confinement of adsorbates on the catalyst surface, and that surface coverage is an essential factor in determining the feasibility of certain elementary processes, and thus product selectivity. The thesis provides a clear overview of rutile catalysts for halogen chemistry and provides detailed insights which can inform the future development of superior catalysts.

The chemical bond – a corner stone in science and a prerequisite for life – is the focus of this thesis. Fundamental and applied aspects of chemical bonding are covered including the development of new computational methods for the characterization and rationalization of chemical interactions. The thesis also covers the study of corrosion of copper-based materials. The latter is motivated by the proposed use of copper as encapsulating material for spent nuclear fuel in Sweden. In close collaboration with experimental groups, state-of-the-art computational methods were employed for the study of chemistry at the atomic scale. First, oxidation of nanoparticulate copper was examined in anoxic aqueous media in order to better understand the copper-water thermodynamics in relation to the corrosion of copper material under oxygen free conditions. With a similar ambition, the water-cuprite interface was investigated with regards to its chemical composition and reactivity. This was compared to the behavior of methanol and hydrogen sulfide at the cuprite surface. An overall ambition during the development of computational methods for the analysis of chemical bonding was to bridge the gap between molecular and materials chemistry. Theory and results are thus presented and applied in both a molecular and a solid-state framework. A new property, the local electron attachment energy, for the characterization of a compound’s local electrophilicity was introduced. Together with the surface electrostatic potential, the new property predicts and rationalizes regioselectivity and trends of molecular reactions, and interactions on metal and oxide nanoparticles and extended surfaces. Detailed atomistic understanding of chemical processes is a prerequisite for the efficient development of chemistry. We therefore envisage that the results of this thesis will find widespread use in areas such as heterogeneous catalysis, drug discovery, and nanotechnology.
Den kemiska bindningen – en hörnsten inom naturvetenskapen och oumbärlig för allt liv – är det centrala temat i den här avhandlingen. Både grundläggande och tillämpade aspekter behandlas. Detta inkluderar utvecklingen av nya beräkningsmetoder för förståelse och karaktärisering av kemiska interaktioner. Dessutom behandlas korrosion av kopparbaserade material. Det sistnämnda är motiverat av förslaget att använda koppar som inkapslingsmaterial för hanteringen av kärnavfall i Sverige. Kvantkemiska beräkningsmetoder enligt state-of-the-art har använts för att studera kemi på atomnivå, detta i nära sammabete med experimentella grupper. Initialt studerades oxidation av kopparnanopartiklar under syrgasfria och vattenrika förhållanden. Detta för att bättre kartlägga koppar-vattensystemets termodynamik. Av samma orsak detaljstuderades även gränsskiktet mellan vatten och kuprit med fokus på dess kemiska sammansättning och reaktivitet. Resultaten har jämförts med metanols och vätesulfids kemiska beteende på ytan av kuprit. En övergripande målsättningen under arbetet med att utveckla nya beräkningsbaserade analysverktyg för kemiska bindningar har varit att överbrygga gapet mellan molekylär- och materialkemi. Därför presenteras teoretiska aspekter samt tillämpningar från både ett molekylärt samt ett fast-fas perspektiv. En ny deskriptor för karaktärisering av föreningars lokala elektrofilicitet har introducerats – den lokala elektronadditionsenergin. Tillsammans med den elektrostatiska potentialen uppvisar den nya deskriptorn förmåga att förutsäga samt förklara regioselektivitet och trender för molekylära reaktioner, och för interaktioner på metal- och oxidbaserade nanopartiklar och ytor. En detaljerad förståelse av kemiska processer på atomnivå är en nödvändighet för ett effektivt utvecklande av kemivetenskapen. Vi förutspår därför att resultaten från den här avhandlingen kommer att få omfattande användning inom områden som heterogen katalys, läkemedelsdesign och nanoteknologi.

QC 20170829

A sustainable solution for meeting the energy demands at our planet is by utilizing wind-, solar-, wave-, thermal-, biomass- and hydroelectric power. These renewable and CO2 emission-free energy sources are highly variable in terms of spatial and temporal availability over the Earth, introducing the need for an appropriate method of storing and carrying energy. Hydrogen has gained significant attention as an energy storage- and carrier media because of the high energy density that is exploited within the ‘power-to-gas’ process chain. A robust way of producing sustainable hydrogen is via electrochemical water splitting. In this work the search for new heterogeneous catalyst materials with the aim of increasing energy efficiency in water splitting has involved methods of both electrochemical water splitting and chemical water oxidation. Some 21 compounds including metal- oxides, oxofluorides, oxochlorides, hydroxide and metals have been evaluated as catalysts. Two of these were synthesized directly onto conductive backbones by hydrothermal methods. Dedicated electrochemical cells were constructed for appropriate analysis of reactions, with one cell simulating an upscale unit accounting for realistic large scale applications; in this cell gaseous products are quantified by use of mass spectrometry. Parameters such as real time faradaic efficiency, production of H2 and O2 in relation to power input or overpotentials, Tafel slopes, exchange current density and electrochemical active surface area as well as turnover numbers and turnover frequencies have been evaluated. Solubility, possible side reactions, the role of the oxidation state of catalytically active elements and the nature of the outermost active surface layer of the catalyst are discussed. It was concluded that metal oxides are less efficient than metal based catalysts, both in terms of energy efficiency and in terms of electrode preparation methods intended for long time operation. The most efficient material was Ni-Fe hydroxide electrodeposited onto Ni metal foam as conductive backbone. Among the other catalysts, Co3Sb4O6F6 was of particular interest because the compound incorporate a metalloid (Sb) and redox inert F and yet show pronounced catalytic performance. In addition, performance of materials in water splitting catalysis has been discussed on the basis of results from electron microscopy, solubility experiments and X-ray diffraction data.

Metal-organic frameworks (MOFs) are crystalline hybrid materials with interesting chemical and physical properties. This thesis is focused on the synthesis and characterization of different MOFs and their use in heterogeneous catalysis. Zeolitic imidazolate frameworks (ZIFs), including ZIF-4, ZIF -7 and ZIF -62, Ln(btc)(H2O) (Ln: Nd, Sm, Eu, Gd, Tb, Ho, Er and Yb), Ln2(bpydc)3(H2O)3, (Ln: Sm, Gd, Nd, Eu, Tb, Ho and Er), MOF-253-Ru and Zn(Co-salophen) MOFs were synthesized. Various characterization techniques were applied to study the properties of these MOFs. X-ray powder diffraction (XRPD), single crystal X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) were extensively used. The effect of synthesis parameters, such as batch composition and temperature, on the formation and morphology of ZIF-7 and ZIF-62 was studied. Structural transformation and flexibility of two series of lanthanide-based MOFs, Ln(btc)(H2O) (Ln: Nd, Ho and Er) and Ln2(bpydc)3(H2O)3, (Ln: Sm and Gd) upon drying and heating were characterized. Relations between metal coordination, structure flexibility and thermal stability among the Sm2(bpydc)3(H2O)3, Nd(btc)(H2O) and MOF-253 were investigated. Salophen- and phenanthroline-based organic linkers were designed, synthesized and characterized. Metal complexes were coordinated to these linkers to be used as catalytic sites within the MOFs. Catalytic studies using two MOF materials, Ln(btc) and MOF-253-Ru, as heterogeneous catalysts in organic transformation reactions were performed. The heterogeneous nature and recyclability of these MOFs were investigated and described.

At the time of doctoral defence the following papers were unpublished and had a status as follows: Paper nr 4: Submitted; Paper nr 5: Submitted

The thesis is divided into a total of 6 chapters and the organization of each chapter is given below. Chapter 1: This chapter gives introduction to Metal Oxyhydroxides, their structures, synthesis method, available applications. A literature review of heterogeneous tandem catalysis is also discussed with comparative study on the active sites responsible for catalysis. This chapter also deals with analytical tools required for characterization of metal oxyhydroxides and the tandem catalysis products. This Chapter also provides the blueprint about the intent of the thesis. Chapter 2: A study of acid-base behaviour of hierarchically condensed phases consisting of Hydroxides, Oxyhydroxides and Oxides of Cr, Mn, Co, Al was done. All the three phases M(OH)x, MO(OH) and Mx(O)y show acid-base bifunctional behavior to varying extent. The strength of acid sites is stronger on MO(OH) while the strength of basic sites is stronger on M(OH)x. MO(OH) are versatile due to its stability and two types of active sites OH/O- and O2- Chapter 3 is divided into two sub chapters 3a & 3b dealing with acid-base properties of FeO(OH) Chapter 3a: A study of acid-base behaviour of polymorphs of FeO(OH) was undertaken in this chapter. Within a same FeO(OH), its polymorphs α, β, γ and δ all show bifunctional acid-base reactivity. The origin of acid and base bifunctional property is due to the surface chemical equilibrium between FeO(OH) and FeOO groups. The difference in the selectivity with the polymorphs is probably due to the different types of FeO(OH) sites and the density of the sites present on the crystal facets of the polymorphs. Chapter 3b: In this chapter, γ-FeO(OH) was demonstrated as an efficient solid base catalyst for the synthesis of pseudoionones (PS). High activity can be attributed to the formation of chemically stable Brønsted basic sites (-O - ) of the surface hydroxyl Chapter 1 2020-Ph. D. Thesis: Mr. Dnyanesh Vernekar, CSIR-NCL, AcSIR 30 groups. In the presence of water, there was an enhancement of catalytic activity by several folds due to the generation of basic sites. Chapter 4 is sub divided into 4a & 4b dealing with redox-base property of metal oxyhydroxides Chapter 4a: This chapter deals with sequential transformation of benzyl alcohol to a variety of C-C and C-N coupling products on layered K-α-CrO(OH). The transformations were feasible because of the co-existence of redox Cr(III) and basic sites (O- and O2- ) on the surface of the K-α-CrO(OH). The presence of electron rich sites (O2- ) due to doping of K and the surface hydroxyl groups were found to be the basic sites on the catalysts using spectroscopy and thermal probe studies. Chapter 4b: A study on usefulness of oxide-oxyhydroxide interface was carried out over a defect manganese oxyhydroxide sample MnOx(OH). An oxide impurity in MnOx(OH) was identified and thoroughly characterized. Its effect on sequential oxidation-condensation reaction was studied and its superiority over a pure MnO(OH) catalyst was explored. The oxide impurity increased O2- basic sites on MnOx(OH). Chapter 5: This chapter studies a mixed metal oxyhydroxide WFeCoO(OH) for catalytic conversion of cyclohexane to adipic acid conversion in one pot. A high surge in Lewis acidity was obtained by W doping in Co-Fe matrix. The high acidity and W sites are responsible for activity. DFT calculations indicated a decrease in deprotonation energies for WFeCoO(OH) as compared to undoped CoO(OH). Chapter 6: This chapter to gives summary and future scope of the present work.
AcSIR

This PhD program has focused on the study, preparation and characterization of new functionalized microporous materials for applications in chromatographic and chromatographic-like flow systems, including the possibility of performing chemical transformations in flow-mode (flow chemistry). The work has been multidisciplinary in nature, including elements of analytical and organic chemistry, material science and process modeling. The materials prepared in this work have been used for different purposes. They have been employed, on the one hand, for the preparation of packed-bed microreactors to perform advanced stereoselective chemical transformations by means of organocatalysts anchored to solid supports (polystyrene and silica gel based) and, on the other, as new stationary phases for chromatographic separations. In the case of organocatalyst-functionalized silicon packed-bed microreactors, we followed the idea that mechanisms of chiral induction due to organocatalysts (asymmetric synthesis) might be exploited for chiral discrimination (chiral chromatography) with their immobilized counterparts. The new materials have been thoroughly characterized in terms of chemico-physical, geometric and thermodynamic properties by investigating the mass transfer phenomena in packed beds, by measuring the adsorption isotherms of different substrates on different porous materials and by characterizing some of their fundamental properties such as porosity, superficial area, functionalization degree, etc. In addition, their dynamic behavior in reactive systems has been studied and modeled to understand not only the thermodynamics but also the kinetics of the process and to optimize, based on this information, the experimental conditions as to maximize production yield. Microreactors and the possibility of performing flow-chemistry through them satisfy the fundamental criteria of green chemistry, allowing for the realization of sustainable processes in terms of environmental impact and cost. The activities of my work have produced seven papers on international peer-reviewed journals. These publications are included at the end of my dissertation. One additional paper is in preparation.

Metalloenzymes catalyse the most fundamental reactions in organic chemistry from oxidation of hydrocarbons to complex C-C bond forming reactions with exceptional selectivity. Mimicking the active site of a metalloenzyme by immobilising well-defined amino acids containing catalytically active transition metal centres based on transitionmetals on a robust inorganic framework, affords powerful catalysts that can be utilised in oxidation reactions. Porous aluminosilicates, mesoporous silicas and polymers offer suitable supports for single-site bio-derived catalysts. Dispersion of catalytically active centers within porous solids with high surface area improves site-isolation which is essential in catalytic processes. These materials can be created from a range of methodologies and the different strategies used for immobilisation can greatly affect the nature of the active catalyst. The routes by which these catalysts are immobilised have given the potential to derivatize inorganic porous hosts and organic polymer structures with amino acids for complexation to metal centres. These bio-derivatized frameworks offer advantages over the homogeneous counterparts in terms of easy separation, recover and recyclability and can carry out selective oxidation reactions with great effectiveness. Herein, heterogenous bioinspired complexes of two amino acids; proline and valine with a series of transition metals (Fe, Cu) were synthesised and immobilised within zeolite cages, mesoporous silica MCM-41 and polystyrene. The preparation methods allowed the synthesis of materials with varying loadings of immobilized active sites. The structural information obtained by spectral and elemental analysis suggested tetrahedral geometry for iron complexes and distorted square planar geometry for copper complexes. Both amino acids coordinated to metal ions through the nitrogen atom of amino group and oxygen atom of carboxylate group via dissociation of the acidic proton as bidentate N,O-donors. The resulting biomimetic complexes were employed as catalysts for oxidation of cyclohexane, cyclohexene, benzyl alcohol and dimethyl sulfide, using molecular dioxygen (O2), tert-butyl hydroperoxide (TBHP) and acetylperoxyborate (APB) as oxidants. The observed trends in catalytic activity showed that the metal loading and separation of the active sites played key role in the selective oxidation reactions. By decreasing the loading of metal active centres, their spatial separation increased which strongly enhanced the activity of catalysts. The decrease in metal active site content resulted in significant increase in TON and TOF. The product selectivity was dependent on the nature of oxidant, hydrophobicity/hydrophilicity of the support, loading of metal active centres and the metal/substrate ratio.

There have been many applications of cerium oxide in oxidation catalysis but the understanding of its role in catalysis is rather limited. This research is concerned with the use of nano-size cerium oxide in methane steam reforming reaction. It is found that addition of cerium oxide to the commercial supported Ni catalysts can dramatically reduce the undesirable carbon deposition (through surface oxidation), which is thermodynamically favorable under low steam conditions. In order to understanding the fundamental role of oxidation activity of the cerium oxide, different sizes of nano-crystallined cerium oxides have been carefully prepared by micro-emulsion technique. Their reactivity is clearly shown to be size dependent. We found that ceria particle sizes of lower than 5.1 nm are able to activate molecular oxygen, which accounts for the unprecedentedly reported critical size effect on oxidation. Characterizations by EPR, XPS, TPR suggest that a substantially large quantity of adsorbed oxygen species (O₂ ^-) is preferentially formed in the small size ceria from air. Also, it is found that the oxygen vacancies are formed in the interface of metal and oxide, and the strength of the metal oxide interaction may influence the formation of the efficient oxygen vacancies, which are responsible for the adsorbed surface oxygen.

[ES] En este trabajo de tesis doctoral, la investigación se ha centrado en el desarrollo de diferentes procesos catalíticos heterogéneos empleando materiales híbridos orgánico-inorgánicos porosos (MOFs y sílices funcionalizadas) y materiales orgánicos aromáti-cos (PAFs), que se han estudiado en diversas reacciones orgánicas. Tras la preparación de los MOFs en estudio, se han caracterizado sus propiedades estructurales y se han determinado sus centros activos en los clústeres metálicos (circonio, hafnio o cerio). La reactividad de estos MOFs y de los materiales híbridos sílice-aminas se ha estudia-do teniendo en cuenta sus centros catalíticos; estas reacciones se han optimizado lle-vando a cabo un estudio de los mecanismos de reacción. Finalmente, se han preparado sólidos homoquirales de tipo PAF que presentan el sistema binaftilo, cuya reactividad también ha sido probada. Más específicamente, en el capítulo 3 se ha estudiado la esterificación de amidas, que permite convertirlas en ésteres, grupos funcionales más versátiles. Esta transfor-mación se ha abordado desde la catálisis heterogénea via MOFs basados en circonio, hafnio y cerio de las series MOF-808, UiO-66 y MOF-801. El catalizador más eficien-te para la esterificación de amidas ha sido el MOF-808-Zr. Mediante análisis TGA y la adsorción de una molécula sonda básica (CO) estudiada utilizando espectroscopia FT-IR, se han determinado los centros ácidos de Lewis y Brönsted presentes en ellos. De los MOFs preparados en este trabajo, el MOF 808-Zr posee una menor conectividad de los clústeres metálicos y un mayor tamaño de poro mayor que el UiO-66 y el MOF-801; además, tiene el balance adecuado de centros ácidos y básicos de Brönsted y Lewis para activar los sustratos de la reacción. El alcance de la alcoholisis con n-butanol se ha extendido a un gran número de sustratos (amidas primarias, secundarias y terciarias; aromáticas y alifáticas). La reacción también se ha estudiado en condicio-nes no solvolíticas con alcoholes más complejos. El catalizador es estable durante la reacción y puede ser reutilizado fácilmente. El mecanismo de reacción en la esterifica-ción de benzamida con n butanol catalizada por MOF-808-Zr se ha investigado me-diante el análisis cinético empleando el modelo de LHHW y el estudio in situ de las interacciones moleculares por FT-IR. En el capítulo 4, se ha investigado la deuteración por intercambio isotópico deute-rio/hidrógeno catalizada por aminas soportadas en sílice comerciales empleando D2O como fuente de deuterio. Este procedimiento es aplicable a una gran gama de sustra-tos, como compuestos carbonílicos, sales de organofosfonio, nitrocompuestos e, inclu-so, hormonas esteroideas. La estabilidad del catalizador, SiO2-(CH2)3-NH2, se mantie-ne hasta en 10 usos de reacción sin pérdidas significativas de la actividad. Por último, en el capítulo 5, se afronta la síntesis y aplicación de PAFs homoquira-les donde se ha integrado el esqueleto del BINOL (1,1′-binaftil-2,2′-diol) y del BIN-BAM (1,1' binaftil-2,2'-disulfonimida) generando tres nuevos PAFs activos en catáli-sis asimétrica: PAF-3,3'-(S)-BINOL, PAF-6,6'-(R)-BINOL y PAF 3,3'-(S)-BINBAM. En concreto, el PAF-6,6'-(R)-BINOL ha demostrado su actividad catalítica en la reacción de alquilación de aldehídos aromáticos con dietil-zinc y el catalizador PAF-3,3'-(S)-BINBAM es activo en la reacción aldólica de Mukaiyama y la reducción del doble enlace de compuestos carbonílicos a,b-insaturados.
[CA] En aquesta tesi doctoral, la investigació s'ha centrat en el desenvolupament de dife-rents processos catalítics heterogenis emprant materials híbrids orgànic-inorgànics porosos (MOFs i sílices funcionalitzades) i materials orgànics aromàtics (PAFs), que s'han estudiat en diverses reaccions orgàniques. Després de la preparació dels MOFs en estudi, s'han caracteritzat les seues propietats estructurals i s'han determinat els seus centres actius en els clústers metàl·lics (zirconi, hafni o ceri). La reactivitat d'aquests MOFs i dels materials híbrids sílice-amines s'ha estudiat tenint en compte els seus cen-tres catalítics; aquestes reaccions s'han optimitzat duent a termini un estudi dels meca-nismes de reacció. Finalment, s'han preparat sòlids homoquirals de tipus PAF que presenten el sistema binaftilo, la reactivitat del qual també ha sigut provada. Més específicament, en el capítol 3 s'ha estudiat l'esterificació d' amides, que per-met convertir-les en èsters, grups funcionals més versàtils. Aquesta transformació s'ha abordat des de la catàlisi heterogènia via *MOFs basats en zirconi, hafni i ceri de les sèries MOF-808, UiO-66 i MOF-801. El catalitzador més eficient per a l'esterificació d'amides ha sigut el MOF-808-Zr. Mitjançant anàlisi TGA i l'adsorció d'una molècula sonda bàsica (CO) estudiada utilitzant espectroscopia FT-IR, s'han determinat els cen-tres àcids de Lewis i Brönsted presents en ells. Dels MOFs preparats en aquest treball, el MOF 808-Zr posseeix una menor connectivitat dels clústers metàl·lics i una major grandària de porus que el UiO-66 i el MOF-801; a més, té el balanç adequat de centres àcids i bàsics de Brönsted i Lewis per a activar els substrats de la reacció. L'abast de l'alcoholisi amb n-butanol s'ha estés a un gran nombre de substrats (amides primàries, secundàries i terciàries; aromàtiques i alifàtiques). La reacció també s'ha estudiat en condicions no solvolítiques amb alcohols més complexos. El catalitzador és estable durant la reacció i pot ser reutilitzat fàcilment. El mecanisme de reacció en l'esterifica-ció de benzamida amb n-butanol catalitzada per MOF-808-Zr s'ha investigat mitja-nçant l'anàlisi cinètica emprant el model de LHHW i l'estudi in situ de les interaccions moleculars per FT-IR. En el capítol 4, s'ha investigat la deuteració per intercanvi isotòpic deuteri/hidrògen catalitzada per amines suportades en sílices comercials emprant D2O com a font de deuteri. Aquest procediment és aplicable a una gran gamma de substrats, com a com-postos carbonílics, sals d'organofosfoni, nitrocompostos i, inclosa, hormones esteroi-dals. L'estabilitat del catalitzador, SiO2-(CH2)3-NH2, es manté fins a 10 usos de reac-ció sense pèrdues significatives de l'activitat. Finalment, en el capítol 5, s'afronta la síntesi i aplicació de PAFs homoquirals on s'ha integrat l'esquelet del BINOL (1,1′-binaftil-2,2′-diol) i del BINBAM (1,1'-binaftil-2,2'-disulfonimida) generant tres nous PAFs actius en catàlisi asimètrica: PAF-3,3'-(S)-BINOL, PAF-6,6'-(R)-BINOL i PAF 3,3'-(S)-BINBAM. En concret, el PAF-6,6'-(R)-BINOL ha demostrat la seua activitat catalítica en la reacció d'alquilació d'aldehids aromàtics amb dietil-zinc i el catalitzador PAF-3,3'-(S)-BINBAM és actiu en la reacció aldólica de Mukaiyama i la reducció del doble enllaç de compostos carbonílics a,b-insaturats.
[EN] In this Doctoral Thesis, the research has been focused on the development of different heterogeneous catalytic processes using hybrid porous organic-inorganic materials (MOFs and functionalized silicas) and organic aromatic materials (PAFs), which have been studied in various organic reactions. After the preparation of the MOFs under study, their structural properties have been characterised and their active centres in the metal clusters (zirconium, hafnium or cerium) have been determined. The reactivity of these MOFs and the hybrid silica-mine materials has been studied considering their catalytic centres; these reactions have been optimised by carrying out a study of the reaction mechanisms. Finally, homochiral PAF-type solids have been prepared with the binafil system, whose reactivity has also been tested. More specifically, the esterification of amides has been studied in Chapter 3. This reaction allows to convert the amides into esters, which are more versatile functional groups. This transformation has been approached from the heterogeneous catalysis via MOFs based on zirconium, hafnium and cerium of the MOF-808, UiO-66 and MOF-801 series. The most efficient catalyst for amide esterification has been MOF-808-Zr. Using TGA analysis and the adsorption of a basic probe molecule (CO) studied using FT-IR spectroscopy, the acid centres of Lewis and Brönsted present in them have been determined. Among the MOFs prepared in this work, MOF 808-Zr has a lower metal cluster connectivity and a larger pore size than UiO-66 and MOF-801; it also has the appropriate balance of acid and basic Brönsted and Lewis centres to activate the reaction substrates. The scope of n-butanol alcoholysis has been extended to a large number of substrates (primary, secondary and tertiary amides; aromatic and aliphatic). The reaction has also been studied in non-solvolitic conditions with more complex alco-hols. The catalyst is stable during the reaction and can be easily reused. The reaction mechanism in the esterification of benzamide with n-butanol catalysed by MOF-808-Zr has been investigated through kinetic analysis using the LHHW model and the in situ study of molecular interactions by FT-IR. In Chapter 4, the deuteration by isotopic deuterium/hydrogen exchange catalysed by commercial silica-supported amines using D2O as a source of deuterium has been investigated. This procedure is applicable to a wide range of substrates, such as carbonylic compounds, organophosphonium salts, nitro compounds and, even, steroid hormones. The stability of the catalyst, SiO2-(CH2)3-NH2, is maintained for up to 10 reaction uses without significant loss of activity. Finally, in Chapter 5, the synthesis and application of homochiral PAFs, in which the structure of BINOL (1,1′-binaftil-2,2′-diol) and BIN-BAM (1,1' binaftil-2,2'-disulfonimide) has been integrated, is discussed. Three new PAFs active in asymmetric catalysis has been generated: PAF-3,3'-(S)-BINOL, PAF-6,6'-(R)-BINOL and PAF 3,3'-(S)-BINBAM. In particular, PAF-6,6'-(R)-BINOL has demonstrated its catalytic activity in the alkylation reaction of aromatic aldehydes with diethyl zinc and the catalyst PAF-3,3'-(S)-BINBAM is active in the Mukaiyama aldolic reaction and the reduction of the double bond of carbonylic a,b-unsaturated compounds.
Villoria Del Álamo, B. (2021). Síntesis de catalizadores sólidos orgánicos e híbridos orgánicos-inorgánicos y su aplicación [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/163789
TESIS

This thesis investigated new metal nanoparticle and semiconductor catalyst and photocatalyst systems for achieving fine chemical synthesis from both fossil-fuel sourced reactants and biomass carbohydrate-derived reactants. Photocatalysts for industrially important organic oxidation reactions were developed that efficiently worked with the aid of solar light irradiation, at low temperature and pressure, that avoided the use of hazardous chemicals. The effects on the organic reaction mechanisms of different noble metal nanoparticle and metal oxide nanostructures were explored for these chemical transformations. Success in developing the nanomaterial photocatalysts has contributed to the field of sustainable green chemical synthesis.

Chapter 1 discusses the importance of the sulfonyl moiety in biological compounds and the developments in the use of sulfur dioxide and sulfur dioxide donors in metal catalysis and organic synthesis. Chapter 2 focuses on the serendipitous discovery, optimisation and exploration of a route towards the synthesis of sulfones via an N-aminosulfonamide intermediate exploiting both palladium-catalysed aminosulfonylation and the predisposition of N aminosulfonamides to decompose to the sulfinate salt (Scheme 1). Scheme 1 Chapter 3 investigates the synthesis of benzosultams with an aryl-N-SO2 linkage. A range of benzosultams and its derivatives were prepared after optimisation of a synthetic sequence involving palladium-catalysed aminosulfonylation and a subsequent Buchwald– Hartwig coupling (Scheme 2). Scheme 2 Chapter 4 describes efforts towards the synthesis of a benzosultam with an aryl-SO2-N linkage through various precursors and metal-catalysed routes using DABSO as the sulfur dioxide source (Figure 1). Figure 1 Chapter 5 provides a summary of this thesis and outlines possibilities for future work. Chapter 6 provides experimental details and data for compounds discussed in this thesis. Appendix A details a brief investigation into the synthesis of N aminosulfonamides from heteroaryl iodides as an extension of the Willis group palladium-catalysed aminosulfonylation reaction (Scheme 3). Scheme 3 Appendix B presents 1H and 13C NMR spectra as well as X-ray crystallographic data of key compounds.

The targets of this thesis were the selective oxidation of hydrocarbons under mild conditions, using cheap and environmentally friendly oxidants and initiators. Three projects are treated; the oxidation of an alkane using O2 and a co-oxidant, the oxidation of toluene using TBHP (tert-butyl hydroperoxide) and finally the oxidation of propane using hydrogen peroxide. C-H bond activation, O2 activation and high conversion with high selectivity were essential points to investigate. In the first project, alkane oxidation was studied in presence of a co-oxidant. The co-oxidant has for purpose to initiate the activation of the alkane and O2, as well as prevent the over-oxidation of the alkane. The co-oxidation of octane using benzaldehyde has been investigated using 1 wt. % AuPd/ C catalyst; the hypothesis is that benzaldehyde oxidation would use a radical mechanism able to activate octane to octanol. Also, the coupling of octanol with activated benzaldehyde would prevent the over-oxidation of octanol by the formation of an ester; octylbenzoate. The aim of the second study was to investigate the selective oxidation of toluene using TBHP at 80 °C with supported noble metal nanoparticle catalysts prepared by sol-immobilisation techniques. Au, Pd and Pt have been use to form mono, bi and trimetallic catalysts of different morphology supported on C and TiO2. These catalysts have been tested for toluene oxidation. The catalyst showing the best activity has been used for further investigation such as reuse test, using H2O2 as oxidant or O2 activation. The third project target was to oxidise propane using H2O2 in mild conditions. 2.5 wt. % Fe/ ZSM-5 (30) has been used to investigate reaction conditions in order to optimise the system. This catalyst has been acid treated; standard and treated catalysts were characterised and analysed to identify the structure and active sites. Role of supports and metals (mono and bimetallic) has been explored in order to improve this system.

Lignin is the most recalcitrant part of woody biomass yet is one of the few natural aromatic resources available in abundance. There is huge potential for this material to be used as a key feedstock in future applications however a conversion route to fine chemicals must first be established. In this thesis, a methodology to take raw wood sawdust and convert its lignin component to value added products whilst avoiding a pyrolysis route has been reported. During biofuel processing, lignin is subjected to a number of pretreatment steps in order to separate it from the lignocellulosic material and it is during these steps that modification of the lignin can occur. The aim of this project was to selectively cleave the dominant β-O-4 linkage using heterogeneous catalysis to form functional aromatic monomers. It was found to be imperative that an appropriate pretreatment was firstly identified in order to avoid depletion of this dominant alkyl-aryl ether bond where, for example, the lignin isolated using an ammonia pretreatment from poplar wood gave an uncondensed structure in comparison to the condensed lignin produced using an organosolv pretreatment. We have shown that lignin can be effectively depolymerised to low molecular weight compounds when the starting material is rich in β-O-4 bonds and we were able to verify this finding using a Pt/Al2O3 catalyst under hydrodeoxygenation/hydrogenolysis conditions. Organosolv lignin from Poplar sawdust was found to have a low β-O-4 content (9.2 %) and subsequently gave limited conversion to fine chemicals (9.0 %) in comparison to the ammonia lignin with a high β-O-4 content (28.9 %) which gave much higher conversion to monomeric product (16.4 %). Further work using lignins isolated using different pretreatment methods supported this conclusion. Whilst GPC was used to give an overview of the initial cracking to breakdown products, GC-MS analysis enabled us to successfully identify 21 monomeric products. Optimisation work using a Pt/Al2O3 catalyst with the ammonia lignin was carried out in order to minimise char production and maximize the yield of the fine chemical products to varying success. Experimental conditions were altered in terms of the solvent used and its composition, reaction temperatures, pressures, time and stirring rates, as well as changing the pH and active metal. It was found that the use of 100 % methanol under the standard conditions yielded the highest amount of monomeric product (43.5 %), whilst the use of 100 % water alternatively gave the highest char production (47.1 %). This knowledge obtained during the initial lignin conversion study was then used to tackle a sulfur-containing lignin known as Kraft lignin. This lignin is readily available as a by-product of the dominant pulping technique adopted by the paper and pulp industry but due to the nature of the technique used to isolate the lignin, the Kraft lignin often incorporates sulfur onto its structure. Such impurities could prove detrimental to the catalytic depolymerisation reaction via catalyst poisoning but it was found that the Kraft lignin behaved in a similar manner to the other condensed lignins under the standard conditions in terms of the total monomeric yield obtained. The Kraft lignin produced 9.2 % of alkylphenolic product in comparison to 7.4 % produced from the standard reaction with soda lignin. It was also noted that the optimised conditions found for the benchmark ammonia lignin did not depolymerise the Kraft lignin to the same extent where, for example, using 100 % methanol with the Kraft lignin hindered the reaction and gave an overall monomeric yield of 5.6 %. This highlighted the fact that whilst one set of conditions may be efficient for the conversion of one type of lignin, this may not be the case for another. This work was followed by an isotopic labelling study to investigate the reaction mechanism which indicated an inverse kinetic isotope effect and that the depolymerisation reaction occurred in two steps. These two steps involved an initial cracking step of the entire lignin molecule to fragmented lignin pieces followed by conversion to monomeric product. Some post-catalyst analysis was also carried out using XRD, BET, TPO and Raman analysis in order to analyse the catalyst surface. The work showed that during the reaction, the lignin deposited onto the catalyst surface and formed a carbonaceous layer which was graphitic in nature. Some samples were found to be more ordered in nature but no obvious trend with respect to the type of lignin used was established.

The reaction of (DIPP)₂TaCl₃(Et₂O) (6, DIPP = 2,6-(CH(CH₃)₂C₆H₃O-)) with two equivalents of 3,5-lutidine and two equivalents of Na/Hg yields the cyclometallated product (DIPP')(DIPP)TaCl(3,5-lutidine)₂ (8) in which one of the isopropyl groups on a DIPP ligand is activated to form a metallacyclopropane complex. This undesired cyclometallation activity prompted the synthesis of a linked aryloxide ligand set, 2,2 '-ethylenebis(6-isopropylphenol) (9, H₂BIPP ), which was designed to avoid the cyclometallation problem. The new H₂BIPP ligand was chelated to both titanium and tantalum to form the compounds (BIPP)TiCl₂ (16) and (BIPP)TaCl₃ (19). Several transition metal alkyl compounds were subsequently synthesized including (BIPP)TiX₂ (X = Me (17), X = benzyl (18)) and (BIPP)TaX₃ (X = Me (25), X = benzyl (24)). Initial reduction chemistry resulted in the formation of (BIPP)Ta(η⁶-C₆Et₆)Cl (31) through the reaction of 19 with two equivalents of Na/Hg and three equivalents of 3-hexyne. From the formation of 31 it was determined that sterics play a large role in the formation of η⁶-arene compounds through the cyclotrimerization of alkynes. The reaction of 31 with two equivalents of 3,5-lutidine resulted in the cyclometallation of the ethylene linker which joined the two phenoxide rings to form TaCl[(OC₆H₃Prⁱ)₂-η2(C,C)-CH=CH](3,5-lutidine)₂ (42) in moderate yield. Compound 42 could also be produced high yield in the reaction of (BIPP)TaCl₃ ( 19) with two equivalents of 3,5-lutidine and two equivalents Na/Hg. (1-[2-(5-Trifluoromethylpyridyl)]-2-hydroxy-3,5-di-t-butylbenzene) ( 45) and 2-(2-pyridyl)phenol (46) were synthesized with the intent to form a ligand set that took advantage of the cyclometallation problem by putting a pyridine functionality in the position likely to be cyclometallated. Monomeric compounds containing 45 and 46, however, were not isolable. In an effort to model the hydrodenitrogenation of pyrrole a novel tantalum-bis(η¹-pyrrolyl) compound was synthesized. The reaction of (DIPP)₃TaCl₂(Et₂O) (39) with two equivalents of lithium pyrrolide resulted in the formation of (η⁵-C₄Me₄N)TaMe₃(η¹(N)-C₄H₄N) (50) in low yield. Attempts to functionalize 50 with chloride groups resulted in the competitive removal of both pyrrolyl and DIPP ligands and, ultimately, intractable metal-containing products.

The known ruthenium pincer complex RuCl(eta3-dcpx)(PPh 3) (7) (PCP = eta3-2,6-(PCy2CH 2)2C6H3) was transformed into several different hydride products under standard transfer hydrogenation conditions. In situ 31P NMR analysis during thermolysis of 7 in basic isopropanol permitted identification of RuH(eta3-dcpx)(PPh 3)(N2) (8a/b), RuH(eta3-dcpx)(PPh 3) (10), and RuH(eta3-dcpx)(PPh3 )(H2) (9a/b). A spectroscopically unobservable species, Ru(H)2[eta2-PC(H)P] (12), is proposed as the active species in transfer hydrogenation catalysis. The novel precatalyst, RuCl(eta3-dcpx)(py)2 ( 14), which may provide a more active catalyst, was synthesized and characterized. Several primary and secondary phosphine complexes of ruthenium were synthesized and tested for their activity in catalytic transfer hydrogenation. Of these, only the bulky HPCy2 ligand in RuCl2(HPCy2) 4 (18a/b) provided high catalytic activity. Reaction of RuCl2(PCy3)2(=CHPh) (24) with HPCy2 transforms it cleanly to 18a, potentially opening new opportunities in tandem catalysis. (Abstract shortened by UMI.)

Hydrolase catalyzed reactions are used for selective chemical catalysis. With directed evolution, rational mutations and molecular modeling the selectivity of these hydrolases can be increased and the origin of selectivity determined. This study investigates four selective hydrolase catalyzed reactions. Using molecular modeling the unusual regioselectivity of Pseudomonas cepacia lipase (PCL) and the selectivity of Candida antarctica B lipase (CAL-B) in nucleoside acylation reactions has been attributed to the binding of the nucleoside base within the active site. The enantio-selectivity of Pseudomonas fluorescens esterase (PFE) has been improved using a rational approach to directed evolution and models to explain the origin of improved mutants has been produced. The enantioselectivity of the beta-lactam ring opening reaction by CAL-B has been attributed to unfavorable steric interaction of the substrate with Ile189 and a model has been proposed for an alcohol bridge between the catalytic histidine (His224) and the lactam amine. Finally, high acetyl selectivity of ThermoGen esterase E018b has been demonstrated and reaction conditions optimized.