Artículos de revistas sobre el tema "Bulk MoWS catalyst"
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1
Wezendonk, Tim A., Quirinus S. E. Warringa, Vera P. Santos, Adam Chojecki, Matthijs Ruitenbeek, Garry Meima, Michiel Makkee, Freek Kapteijn y Jorge Gascon. "Structural and elemental influence from various MOFs on the performance of Fe@C catalysts for Fischer–Tropsch synthesis". Faraday Discussions 197 (2017): 225–42. http://dx.doi.org/10.1039/c6fd00198j.
Resumen
The structure and elementary composition of various commercial Fe-based MOFs used as precursors for Fischer–Tropsch synthesis (FTS) catalysts have a large influence on the high-temperature FTS activity and selectivity of the resulting Fe on carbon composites. The selected Fe-MOF topologies (MIL-68, MIL-88A, MIL-100, MIL-101, MIL-127, and Fe-BTC) differ from each other in terms of porosity, surface area, Fe and heteroatom content, crystal density and thermal stability. They are re-engineered towards FTS catalysts by means of simple pyrolysis at 500 °C under a N2 atmosphere and afterwards characterized in terms of porosity, crystallite phase, bulk and surface Fe content, Fe nanoparticle size and oxidation state. We discovered that the Fe loading (36–46 wt%) and nanoparticle size (3.6–6.8 nm) of the obtained catalysts are directly related to the elementary composition and porosity of the initial MOFs. Furthermore, the carbonization leads to similar surface areas for the C matrix (SBET between 570 and 670 m2 g−1), whereas the pore width distribution is completely different for the various MOFs. The high catalytic performance (FTY in the range of 1.9–4.6 × 10−4 molCO gFe−1 s−1) of the resulting materials could be correlated to the Fe particle size and corresponding surface area, and only minor deactivation was found for the N-containing catalysts. Elemental analysis of the catalysts containing deliberately added promoters and inherent impurities from the commercial MOFs revealed the subtle interplay between Fe particle size and complex catalyst composition in order to obtain high activity and stability next to a low CH4 selectivity.
2
Zhao, Tian, Mingliang Luo, Minmin Zou, Saiqun Nie y Xianggang Li. "Advances in Nano-Sized Metal-Organic Frameworks and Biomedical Applications: A Review". Journal of Biomedical Nanotechnology 18, n.º 7 (1 de julio de 2022): 1707–27. http://dx.doi.org/10.1166/jbn.2022.3389.
Resumen
Metal-organic frameworks (MOFs) have attracted much attention since their discovery and have potential applications in many fields, including gas storage, separation, catalysis, and thermal energy conversion, due to their unique high porosity structure, tunable pore size, and functionalizability. Nano-sized MOFs (NMOFs) possessed both the properties of conventional bulk MOFs and additional physical/chemical properties because of their nanometer size, and thus can exhibit even better performance than related conventional bulk MOFs. In this paper, we introduced the development of NMOFs and presented several classical NMOFs structures and their applications. It also focused on the preparation methods and applications of some important NMOFs in recent years, and provided an outlook on the applications of NMOFs in novel material fields and their development perspective.
3
Navalón, Sergio, Mercedes Álvaro, Amarajothi Dhakshinamoorthy y Hermenegildo García. "Encapsulation of Metal Nanoparticles within Metal–Organic Frameworks for the Reduction of Nitro Compounds". Molecules 24, n.º 17 (22 de agosto de 2019): 3050. http://dx.doi.org/10.3390/molecules24173050.
Resumen
Nitro group reduction is a reaction of a considerable importance for the preparation of bulk chemicals and in organic synthesis. There are reports in the literature showing that incorporation of metal nanoparticles (MNPs) inside metal–organic frameworks (MOFs) is a suitable strategy to develop catalysts for these reactions. Some of the examples reported in the literature have shown activity data confirming the superior performance of MNPs inside MOFs. In the present review, the existing literature reports have been grouped depending on whether these MNPs correspond to a single metal or they are alloys. The final section of this review summarizes the state of the art and forecasts future developments in the field.
4
Wang, Zhanke, Lei Ge, Guangxu Zhang, Yao Chen, Rongrong Gao, Hao Wang y Zhonghua Zhu. "The controllable synthesis of urchin-shaped hierarchical superstructure MOFs with high catalytic activity and stability". Chemical Communications 57, n.º 70 (2021): 8758–61. http://dx.doi.org/10.1039/d1cc03547a.
Resumen
The sizes of rod-shaped bulk MOFs could be decreased to the nanoscale via using metal oxides as precursors, and then the as-obtained nanosized MOFs could be self-assembled to form urchin-shaped superstructure MOFs via changing the dosage of ligands.
5
Cherevko, A. I., G. L. Denisov, I. A. Nikovskii, A. V. Polezhaev, A. A. Korlyukov y V. V. Novikov. "Composite Materials Manufactured by Photopolymer 3D Printing with Metal-Organic Frameworks". Russian Journal of Coordination Chemistry 47, n.º 5 (mayo de 2021): 319–25. http://dx.doi.org/10.1134/s107032842105002x.
Resumen
Abstract New composite materials containing metal-organic framework (MOF-5) particles were manufactured by 3D printing. The optimal composition of the photopolymer formulation and printing conditions ensuring the highest quality of printing were selected. Retention of the metal-organic framework (MOF) structure in the resulting composite objects was demonstrated by powder X-ray diffraction. The distribution of MOF-5 particles over the whole bulk of the 3D product was studied by X-ray computed tomography. In the future, composite materials of this type containing catalytically active MOFs, with their structure and properties being controllable at the micro and macro levels, could find application as catalysts of various chemical processes.
6
Bukowski, Brandon C., Frerich J. Keil, Peter I. Ravikovitch, German Sastre, Randall Q. Snurr y Marc-Olivier Coppens. "Connecting theory and simulation with experiment for the study of diffusion in nanoporous solids". Adsorption 27, n.º 5 (22 de abril de 2021): 683–760. http://dx.doi.org/10.1007/s10450-021-00314-y.
Resumen
AbstractNanoporous solids are ubiquitous in chemical, energy, and environmental processes, where controlled transport of molecules through the pores plays a crucial role. They are used as sorbents, chromatographic or membrane materials for separations, and as catalysts and catalyst supports. Defined as materials where confinement effects lead to substantial deviations from bulk diffusion, nanoporous materials include crystalline microporous zeotypes and metal–organic frameworks (MOFs), and a number of semi-crystalline and amorphous mesoporous solids, as well as hierarchically structured materials, containing both nanopores and wider meso- or macropores to facilitate transport over macroscopic distances. The ranges of pore sizes, shapes, and topologies spanned by these materials represent a considerable challenge for predicting molecular diffusivities, but fundamental understanding also provides an opportunity to guide the design of new nanoporous materials to increase the performance of transport limited processes. Remarkable progress in synthesis increasingly allows these designs to be put into practice. Molecular simulation techniques have been used in conjunction with experimental measurements to examine in detail the fundamental diffusion processes within nanoporous solids, to provide insight into the free energy landscape navigated by adsorbates, and to better understand nano-confinement effects. Pore network models, discrete particle models and synthesis-mimicking atomistic models allow to tackle diffusion in mesoporous and hierarchically structured porous materials, where multiscale approaches benefit from ever cheaper parallel computing and higher resolution imaging. Here, we discuss synergistic combinations of simulation and experiment to showcase theoretical progress and computational techniques that have been successful in predicting guest diffusion and providing insights. We also outline where new fundamental developments and experimental techniques are needed to enable more accurate predictions for complex systems.
7
Nandiyanto, Asep Bayu Dani. "Nano Metal-Organic Framework Particles (i.e. MIL-100(Fe), HKUST-1(Cu), Cu-TPA, and MOF-5(Zn)) using a solvothermal process". Indonesian Journal of Science and Technology 4, n.º 2 (9 de julio de 2019): 220–28. http://dx.doi.org/10.17509/ijost.v4i2.18178.
Resumen
Metal-organic framework (MOF) is attractive because of its representation as a class of crystalline porous materials with excellent properties, specifically its chemical functionality and high porosity, making it potentially tailored for various desired applications. Although the synthesis of MOFs have been well-documented, most reports are in the bulk and micrometer sizes. The synthesis of MOFs in the smaller size is still inevitable. This work reports the synthesis of nano MOF particles (i.e., MIL-100(Fe), HKUST-1(Cu), Cu-TPA, and MOF-5(Zn)). In the experiment, MOFs were created by interacting ligands and metal ions in the specific solvent in the solvothermal process. Different from other reports, this study used low concentrations of ligands and metal ions, in which this is effective to control ligand-metal ion interaction, reaction, nucleation, and growth of MOF. The successful synthesis was obtained and effective for various MOF particles by changing types of ligands and metal ions. The study also obtained that compatibility and dilution of the ligands and the metal ions in the specific solvent are important parameters. This information will bring new strategies and further developments for the synthesis of MOF materials for wider range of potential applications in separation, catalysis, dye adsorption, and drug carrier uses.
8
Ntouros, Vasileios, Ioannis Kousis, Anna Laura Pisello y Margarita Niki Assimakopoulos. "Binding Materials for MOF Monolith Shaping Processes: A Review towards Real Life Application". Energies 15, n.º 4 (17 de febrero de 2022): 1489. http://dx.doi.org/10.3390/en15041489.
Resumen
Metal–organic frameworks (MOFs) could be utilized for a wide range of applications such as sorption, catalysis, chromatography, energy storage, sensors, drug delivery, and nonlinear optics. However, to date, there are very few examples of MOFs exploited on a commercial scale. Nevertheless, progress in MOF-related research is currently paving the way to new industrial opportunities, fostering applications and processes interconnecting fundamental chemistry with engineering and relevant sectors. Yet, the fabrication of porous MOF materials within resistant structures is a key challenge impeding their wide commercial use for processes such as adsorptive separation. In fact, the integration of nano-scale MOF crystallic structures into bulk components that can maintain the desired characteristics, i.e., size, shape, and mechanical stability, is a prerequisite for their wide practical use in many applications. At the same time, it requires sophisticated shaping techniques that can structure nano/micro-crystalline fine powders of MOFs into diverse types of macroscopic bodies such as monoliths. Under this framework, this review aims to bridge the gap between research advances and industrial necessities for fostering MOF applications into real life. Therefore, it critically explores recent advances in the shaping and production of MOF macro structures with regard to the binding materials that have received little attention to date, but have the potential to give new perspectives in the industrial applicability of MOFs. Moreover, it proposes future paths that can be adopted from both academy and industry and can further boost MOF exploitation.
9
Tao, Yehan, Jian Du, Yi Cheng, Jie Lu, Douyong Min y Haisong Wang. "Advances in Application of Cellulose—MOF Composites in Aquatic Environmental Treatment: Remediation and Regeneration". International Journal of Molecular Sciences 24, n.º 9 (24 de abril de 2023): 7744. http://dx.doi.org/10.3390/ijms24097744.
Resumen
Metal organic frameworks (MOFs) have gained remarkable interest in water treatment due to their fascinating characteristics, such as tunable functionality, large specific surface area, customizable pore size and porosity, and good chemical and thermal stability. However, MOF particles tend to easily agglomerate in nanoscale, thus decreasing their activity and processing convenience. It is necessary to shape MOF nanocrystals into maneuverable structures. The in situ growth or ex situ incorporation of MOFs into inexpensive and abundant cellulose-family materials can be effective strategies for the stabilization of these MOF species, and therefore can make available a range of enhanced properties that expand the industrial application possibilities of cellulose and MOFs. This paper provides a review of studies on recent advances in the application of multi-dimensional MOF–cellulose composites (e.g., aerogels, membranes, and bulk materials) in wastewater remediation (e.g., metals, dyes, drugs, antibiotics, pesticides, and oils) and water regeneration by adsorption, photo- or chemocatalysis, and membrane separation strategies. The advantages brought about by combining MOFs and cellulose are described, and the performance of MOF–cellulose is described and compared to its counterparts. The mechanisms of relative MOF–cellulose materials in processing aquatic pollutants are included. Existing challenges and perspectives for future research are proposed.
10
Tian, Jiayue, Feilong Jiang, Daqiang Yuan, Linjie Zhang, Qihui Chen y Maochun Hong. "Electric‐Field Assisted In Situ Hydrolysis of Bulk Metal–Organic Frameworks (MOFs) into Ultrathin Metal Oxyhydroxide Nanosheets for Efficient Oxygen Evolution". Angewandte Chemie International Edition 59, n.º 31 (26 de mayo de 2020): 13101–8. http://dx.doi.org/10.1002/anie.202004420.
11
Zheng, Daniel Jia, Mikaela Gorlin, Hongbin Xu, Junghwa Kim, Kaylee Lynn McCormack, Jiayu Peng, Yuriy Román-Leshkov y Yang Shao-Horn. "Stability of Metal Hydroxide Organic Frameworks for Oxygen Evolution". ECS Meeting Abstracts MA2022-02, n.º 44 (9 de octubre de 2022): 1682. http://dx.doi.org/10.1149/ma2022-02441682mtgabs.
Resumen
The oxygen evolution reaction (OER) is central to storing electrical energy via chemical bonds in energy carriers and fuels through reactions such as electrochemical water splitting to produce hydrogen, CO2 reduction for CO and liquid hydrocarbons, and nitrogen to ammonia. While there has been considerable work towards the engineering of inexpensive yet highly active OER catalysts, current state-of-the-art materials are still at least an order of magnitude less active than oxygen evolving complexes found in biological systems that intricately combine inorganic metal-oxo clusters with organic ligands.1 As a result, metal organic frameworks (MOFs) have drawn considerable attention as hybrid organic-inorganic systems that can potentially mimic the unique structure of biological oxygen evolving complexes. Recently, metal hydroxide organic frameworks (MHOFs),2 a new class of MOFs that combine layered hydroxides with aromatic carboxylate linkers that stabilize the structure via π-π interactions, have been shown to display three times the tunability of layered hydroxides, offering extensive opportunities for further engineering of its electrochemical properties for numerous applications. However, the long-term stability of these material during OER is still unclear, which would be paramount to understand for further rational design of this class of material. In this study, we investigated Ni-based MHOFs with carboxylate linkers of varying π-π interaction strengths to understand how these differences affect the electrochemical stability of these materials during OER. We observed that the MHOFs all undergo activation during OER leading to two orders of magnitude increase in OER activity, where the MHOFs with weaker π-π interaction strengths tend to transform at a faster rate than the MHOFs with stronger π-π interaction strengths. We further characterized the MHOFs using a wide range of analytical techniques, including scanning transmission electron microscopy, Raman spectroscopy, x-ray photoelectron spectroscopy, and hard x-ray absorption spectroscopy, before and after extended OER cycling and galvanostatic tests to understand the transformed phase, which suggested that while the bulk structure largely remains unchanged, the surface undergoes significant restructuring into a Ni(OH)2-like phase during OER. Using operando UV-vis and Raman spectroscopy measurements on the MHOFs during OER to understand the factors that induce the transformation process, we found that there was a clear link between the Ni2+/3+, 4+ redox couple observed around 1.4 VRHE and a loss in the carboxylate organic linkers for the linkers with weak π-π interactions. However, for the MHOFs synthesized with linkers exhibiting strong π-π interaction strengths, there were smaller changes to the overall material during OER, suggesting that the bulk stability of these materials is largely dictated by the linker interaction strength and activation are primarily only surface transformations. These results directly demonstrate that linker selection also plays a key role in the stability MOFs under electrochemical conditions and are pertinent for rational design and understanding of the stability and activity of hybrid organic-inorganic materials as electrocatalysts. References: Hong, W. T. et al. Toward the rational design of non-precious transition metal oxides for oxygen electrocatalysis. Energy Environ. Sci. 8, 1404–1427 (2015). Yuan, S. et al. Tunable metal hydroxide–organic frameworks for catalysing oxygen evolution. Nat. Mater. (2022).
12
Ren, Ren, Huilei Zhao, Xiaoyu Sui, Xiaoru Guo, Xingkang Huang, Yale Wang, Qianqian Dong y Junhong Chen. "Exfoliated Molybdenum Disulfide Encapsulated in a Metal Organic Framework for Enhanced Photocatalytic Hydrogen Evolution". Catalysts 9, n.º 1 (16 de enero de 2019): 89. http://dx.doi.org/10.3390/catal9010089.
Resumen
An exfoliated MoS2 encapsulated into metal-organic frameworks (MOFs) was fabricated as a promising noble-metal-free photocatalyst for hydrogen production under visible light irradiation. The as-synthesized samples were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller (BET) surface analysis. It is well known that bulk MoS2 is unsuitable for photocatalysis due to its inadequate reduction and oxidation capabilities. However, exfoliated MoS2 exhibits a direct band gap of 2.8 eV due to quantum confinement, which enables it to possess suitable band positions and retain a good visible-light absorption ability. As a result, it is considered to be an encouraging candidate for photocatalytic applications. Encapsulating exfoliated MoS2 into MOF demonstrates an improved visible light absorption ability compared to pure MOF, and the highest hydrogen production rate that the encapsulated exfoliated MoS2 could reach was 68.4 μmol h-1g-1, which was much higher than that of pure MOF. With a suitable band structure and improved light-harvesting ability, exfoliated MoS2@MOF could be a potential photocatalyst for hydrogen production.
13
Tian, Jiayue, Feilong Jiang, Daqiang Yuan, Linjie Zhang, Qihui Chen y Maochun Hong. "Cover Picture: Electric‐Field Assisted In Situ Hydrolysis of Bulk Metal–Organic Frameworks (MOFs) into Ultrathin Metal Oxyhydroxide Nanosheets for Efficient Oxygen Evolution (Angew. Chem. Int. Ed. 31/2020)". Angewandte Chemie International Edition 59, n.º 31 (22 de junio de 2020): 12545. http://dx.doi.org/10.1002/anie.202007873.
14
Mou, Qiuxiang, Zhenhang Xu, Wei Zuo, Tianyu Shi, Erlei Li, Gongzhen Cheng, Xinghai Liu, Huaming Zheng, Houbin Li y Pingping Zhao. "Metal-Organic-Framework Embellished through Ion Etching Method for Highly Enhanced Electrochemical Oxygen Evolution Reaction Catalysis". Materials Chemistry Frontiers, 2022. http://dx.doi.org/10.1039/d2qm00388k.
Resumen
Metal-organic-frameworks (MOFs) are scarely considered to catalyse electrochamical reaction directly, due to the limitation by their bulk structure, poor conductivity and scarce active sites. Fe ions, as an effective activity...
15
Huang, Chuanhui, Weiming Sun, Yingxue Jin, Quanquan Guo, David Mücke, Xingyuan Chu, Zhongquan Liao et al. "A General Synthesis of Nanostructured Conductive MOFs from Insulating MOF Precursors for Supercapacitors and Chemiresistive Sensors". Angewandte Chemie International Edition, 27 de noviembre de 2023. http://dx.doi.org/10.1002/anie.202313591.
Resumen
Two‐dimensional conjugated metal‐organic frameworks (2D c‐MOFs) are emerging as unique layer‐stacked crystalline coordination polymers that simultaneously possess porous and conductive properties. However, the controlled synthesis of hierarchically nanostructured 2D c‐MOFs with high crystallinity and customized morphologies is essential for energy and electronic devices, which remains a great challenge. Herein, we present a template strategy to synthesize 12 different 2D c‐MOFs with controlled morphologies and dimensions via insulating MOFs‐to‐c‐MOFs transformations. The resultant hierarchically nanostructured 2D c‐MOFs feature intrinsic electrical conductivity (up to 102 S cm‐1) and higher surface areas (up to ~62 times) than the reported bulk‐type 2D c‐MOFs, which are beneficial for improved access to active sites and enhanced mass transport. As proof‐of‐concept applications, the resultant hollow Cu‐BHT nanocube‐based supercapacitor exhibits over 2.3‐fold improvement in specific capacity (364.5 F g‐1) in organic electrolyte than the bulk‐type Cu‐BHT (161.9 F g‐1), surpassing the reported MOF‐based electrodes (up to 202 F g‐1). In addition, the Cu‐HHB nanoflower‐based chemiresistive gas sensor displays over 2.5‐fold enhancement in response intensity toward H2S compared to bulk‐type Cu‐HHB, boasting the fastest response speed and one of the lowest limits of detection ever reported for H2S sensors at room temperature.
16
Anan, Shizuka, Takuya Kurihara, Masaki Yamaguchi, Hirotsugu Kikuchi y Kenta Kokado. "Enhanced Orientation of Liquid Crystals Inside Micropores of Metal–Organic Frameworks Having Thermoresponsivity". Chemistry – A European Journal, 5 de enero de 2024. http://dx.doi.org/10.1002/chem.202303277.
Resumen
With the aim of controlling the orientation of liquid crystals (LCs) toward realizing external stimuli–responsive materials with tunable functionalities, we synthesized a composite of LCs and metal–organic frameworks (MOFs) by filling LCs into the pores of MOFs (LC@MOFs) for the first time. The included LCs interact with the MOFs through coordination bonds between the cyano groups of the LCs and the metal ions of the MOFs, enabling the orientation of the LC molecules inside the pores of the MOFs and the realization of birefringence of LC@MOFs. The three‐dimensional nanometer interstice frameworks maintained the LC orientation even at temperatures much higher than the isotropic phase transition temperature of bulk LCs. Furthermore, the orientational state changed upon heating or cooling, inducing temperature‐dependent birefringence. This study provides a new approach to the development of stimuli–responsive optical materials and stimuli–responsive MOFs.
17
Parashar, Ranjeev Kumar, Priyajit Jash, Michael Zharnikov y Prakash Chandra Mondal. "Metal‐organic Frameworks in Semiconductor Devices". Angewandte Chemie International Edition, 22 de enero de 2024. http://dx.doi.org/10.1002/anie.202317413.
Resumen
Metal‐organic frameworks (MOFs) are a specific class of hybrid, crystalline, nano‐porous materials made of metal‐ion‐based ‘nodes’ and organic linkers. Most of the studies on MOFs largely focused on porosity, chemical and structural diversity, gas sorption, sensing, drug delivery, catalysis, and separation applications. In contrast, much less reports paid attention to understanding and tuning the electrical properties of MOFs. Poor electrical conductivity of MOFs (~10‐7 – 10‐10 Scm‐1), reported in earlier studies, impeded their applications in electronics, optoelectronics, and renewable energy storage. To overcome this drawback, the MOF community has adopted several intriguing strategies for electronic applications. The present review focuses on creatively designed bulk MOFs and surface‐anchored MOFs (SURMOFs) with different metal nodes (from transition metals to lanthanides), ligand functionalities, and doping entities, allowing tuning and enhancement of electrical conductivity. Diverse platforms for MOFs‐based electronic device fabrications, conductivity measurements, and underlying charge transport mechanisms are also addressed. Overall, the review highlights the pros and cons of MOFs‐based electronics (MOFtronics), followed by an analysis of the future directions of research, including optimization of the MOF compositions, heterostructures, electrical contacts, device stacking, and further relevant options which can be of interest for MOF researchers and result in improved devices performance.
18
Parashar, Ranjeev Kumar, Priyajit Jash, Michael Zharnikov y Prakash Chandra Mondal. "Metal‐organic Frameworks in Semiconductor Devices". Angewandte Chemie, 22 de enero de 2024. http://dx.doi.org/10.1002/ange.202317413.
Resumen
Metal‐organic frameworks (MOFs) are a specific class of hybrid, crystalline, nano‐porous materials made of metal‐ion‐based ‘nodes’ and organic linkers. Most of the studies on MOFs largely focused on porosity, chemical and structural diversity, gas sorption, sensing, drug delivery, catalysis, and separation applications. In contrast, much less reports paid attention to understanding and tuning the electrical properties of MOFs. Poor electrical conductivity of MOFs (~10‐7 – 10‐10 Scm‐1), reported in earlier studies, impeded their applications in electronics, optoelectronics, and renewable energy storage. To overcome this drawback, the MOF community has adopted several intriguing strategies for electronic applications. The present review focuses on creatively designed bulk MOFs and surface‐anchored MOFs (SURMOFs) with different metal nodes (from transition metals to lanthanides), ligand functionalities, and doping entities, allowing tuning and enhancement of electrical conductivity. Diverse platforms for MOFs‐based electronic device fabrications, conductivity measurements, and underlying charge transport mechanisms are also addressed. Overall, the review highlights the pros and cons of MOFs‐based electronics (MOFtronics), followed by an analysis of the future directions of research, including optimization of the MOF compositions, heterostructures, electrical contacts, device stacking, and further relevant options which can be of interest for MOF researchers and result in improved devices performance.
19
Walker, Samuel E., William Chant, Shannon Thoonen, Kellie L. Tuck y David R. Turner. "Stabilization of Lantern‐Type Metal‐Organic Cages (MOCs) by Protective Control of Ligand Exchange Rates". Chemistry – A European Journal, 16 de febrero de 2024. http://dx.doi.org/10.1002/chem.202400072.
Resumen
Self‐assembling systems in nature display remarkable complexity with assemblies of different sub‐units to generate functional species. Synthetic analogues of such systems are a challenge, often requiring the ability to bias distributions that are under thermodynamic assembly control. Using lantern‐type MOCs (metal‐organic cages) as a prototypical self‐assembling system, herein we explore the role that steric bulk plays in controlling the exchange rate of ligands in paddlewheel‐based assemblies, and thus the stability of cages, in competitive self‐assembling scenarios. The effective lifetime of the lantern‐type MOCs varies over an order of magnitude depending on the steric bulk proximal to the metal nodes with lifetimes of the cages ranging from tens of minutes to several hours. The bulk of the coordinating solvents likewise reduces the rate of ligand exchange, and thus yields longer‐lived species. Understanding this subtle effect has implications for controlling the stability of complex assemblies in competitive environments with implications for guest release and application.
20
Yang, Dong y Bruce C. Gates. "Characterization, Structure, and Reactivity of Hydroxyl groups on Metal‐Oxide Cluster Nodes of Metal‐Organic Frameworks: Structural Diversity and Keys to Reactivity and Catalysis". Advanced Materials, 3 de septiembre de 2023. http://dx.doi.org/10.1002/adma.202305611.
Resumen
AbstractAmong the most stable metal–organic frameworks (MOFs) are those incorporating nodes that are metal oxide clusters with frames such as Zr6O8. This review is a summary of the structure, bonding, and reactivity of MOF node hydroxyl groups, emphasizing those bonded to nodes containing aluminum and zirconium ions. Hydroxyl groups are often present on these nodes, sometimes balancing the charges of the metal ions. They arise during MOF syntheses in aqueous media or in post‐synthesis treatments. They have been identified with infrared and 1H nuclear magnetic resonance spectroscopies and characterized by their reactivities with polar compounds such as alcohols. Terminal OH, paired μ2‐OH, and aqua groups on nodes are catalytic sites in numerous reactions. Relatively unreactive hydroxyl groups (such as isolated μ2‐OH groups) may replace reactive groups and inhibit catalysis; some node hydroxyl groups (e.g., μ3‐OH) are mere spectators in catalysis. There are similarities between MOF node hydroxyl groups and those on the surfaces of bulk metal oxides, zeolites, and enzymes, but the comparisons are mostly inexact, and much remains to be understood about MOF node hydroxyl group chemistry. We posit that understanding and controlling this chemistry will lead to tailored MOFs and improved adsorbents and catalysts.This article is protected by copyright. All rights reserved
21
Doan, Huan V., Harina Amer Hamzah, Prasanth Karikkethu Prabhakaran, Chiara Petrillo y Valeska P. Ting. "Hierarchical Metal–Organic Frameworks with Macroporosity: Synthesis, Achievements, and Challenges". Nano-Micro Letters 11, n.º 1 (8 de julio de 2019). http://dx.doi.org/10.1007/s40820-019-0286-9.
Resumen
Abstract Introduction of multiple pore size regimes into metal–organic frameworks (MOFs) to form hierarchical porous structures can lead to improved performance of the material in various applications. In many cases, where interactions with bulky molecules are involved, enlarging the pore size of typically microporous MOF adsorbents or MOF catalysts is crucial for enhancing both mass transfer and molecular accessibility. In this review, we examine the range of synthetic strategies which have been reported thus far to prepare hierarchical MOFs or MOF composites with added macroporosity. These fabrication techniques can be either pre- or post-synthetic and include using hard or soft structural template agents, defect formation, routes involving supercritical CO2, and 3D printing. We also discuss potential applications and some of the challenges involved with current techniques, which must be addressed if any of these approaches are to be taken forward for industrial applications.
22
Wang, Haosen, Yanwei Ren, Xiao Feng y Huanfeng Jiang. "Ultrathin 2D Porphyrin‐Based Zr‐MOF Nanosheets as Heterogeneous Catalysts for Styrene Epoxidation and Benzylic C‐H Oxidation". ChemCatChem, 27 de febrero de 2024. http://dx.doi.org/10.1002/cctc.202400119.
Resumen
Selective oxidation of hydrocarbons using molecular oxygen as sole oxidant under mild conditions remains a challenging task. In this context, metal‐organic frameworks (MOFs) have been widely used in various oxidation reactions due to their porosity, high surface area and designability. However, the slow diffusion of substrates/products in micropores of three‐dimensional (3D) bulk MOFs hinders the efficient catalytic performance of such materials. Herein an ultrathin two‐dimensional (2D) porphyrin‐based Zr‐MOF nanosheet (Zr‐TCPP) is synthesized through modulator‐control strategy. Subsequently, various metal ions are anchored into the porphyrin ring by post synthesis modification to afford a series of 2D Zr‐TCPP(M) (M=Mn, Fe, Co, Ni, Cu and Zn). Various structural characterization techniques indicate Zr‐TCPP(M) is nanoflower structure with ultrathin nanoplate petals which provides fully exposed accessible active sites. Among them, Zr‐TCPP(Fe) shows excellent catalytic performance in styrene epoxidation reactions and benzylic C‐H oxidation reactions using O2 as sole oxidant under ambient temperature and pressure. The remarkable activity arises from high density of exposed porphyrin‐Fe active sites, low diffusion barriers for substrates and products, as well as a similar homogeneous reaction space. Furthermore, Zr‐TCPP(Fe) nanosheet is easily recycled by centrifugation and reused at least five times without significant loss of catalytic activity.
23
Li, Meng-Hao, Zhiqiang Yang, Hui Hui, Bing Yang, Yan Wang y Ying-Wei Yang. "Superstructure‐Induced Hierarchical Assemblies for Nanoconfined Photocatalysis". Angewandte Chemie International Edition, 5 de octubre de 2023. http://dx.doi.org/10.1002/anie.202313358.
Resumen
Most attempts to synthesize supramolecular nanosystems are limited to a single mechanism, often resulting in the formation of nanomaterials that lack diversity in properties. Herein, hierarchical assemblies with appropriate variety are fabricated in bulk via a superstructure‐induced organic‐inorganic hybrid strategy. The dynamic balance between substructures and superstructures is managed using covalent organic frameworks (COFs) and metal‐organic frameworks (MOFs) as dual building blocks to regulate the performances of hierarchical assemblies. Significantly, the superstructures resulting from the controlled cascade between COFs and MOFs create highly active photocatalytic systems through multiple topologies. Our designed tandem photocatalysis can precisely and efficiently regulate the conversion rates of bioactive molecules (benzo[d]imidazoles) via competing redox pathways. Furthermore, benzo[d]imidazoles catalyzed by such supramolecular nanosystems are afforded in isolated yields ranging from 70% to 93% within tens of minutes. The multilayered structural states within the supramolecular systems demonstrate the importance of hierarchical assemblies in facilitating photocatalytic propagation and expanding the structural repertoire of supramolecular hybrids.
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Zhu, Shan, Chuanhui Huang, Xiao Li, Xiangyu Chen, Haochen Ye, Zhenjie Xue, Wenping Hu y Tie Wang. "Enhanced photothermal conversion in 3D stacked metal–organic framework nanosheets". Aggregate, 4 de marzo de 2024. http://dx.doi.org/10.1002/agt2.529.
Resumen
AbstractIncorporating metal nanoparticles (MNPs) in metal–organic frameworks (MOFs) demonstrated great potential in the field of photo‐/photothermal‐catalysis. However, the oriented design and optimization of the 3D nano‐architectures of MOF substrates to achieve high‐efficiency light harvesting remains a challenge. Herein, guided on theoretical simulation, a facile etching strategy was employed to fabricate a 3D orderly‐stacked‐MOF‐nanosheet‐structure (CASFZU‐1) with a high electric field energy‐density‐distribution; well‐dispersed MNPs were afterwards encapsulated onto the MOF support. The unique nanosheet structure improved the light absorbance over the broadband spectrum, thereby enhancing the plasmonic photothermal effects of the MNPs@CASFZU‐1 composites. Based on the plasmon‐driven photothermal conversion, the MNPs@CASFZU‐1 composites exhibited approximately twofold catalytic efficiency in the hydrogenation reaction and a lower temperature for the full conversion of carbon monoxide, compared to their bulk‐type composites. The surface‐plasmon‐driven photothermal effects can be exploited in innovative MNPs@MOF platforms for various applications.
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Kamanna, Kantharaju. "Amino acids and Peptides Organocatalysts: A Brief Overview on Its Evolution and Applications in Organic Asymmetric Synthesis". Current Organocatalysis 07 (17 de noviembre de 2020). http://dx.doi.org/10.2174/2213337207999201117093848.
Resumen
: This review highlights the application of biopolymers of natural α-amino acids and its derived wild type peptides employed as an organocatalysis for the asymmetric synthesis published by researchers across the globe is described. The α-amino acids with L-stereochemistry are available commercial in pure form are played crucial role in enantioselective chiral molecule synthesis. Out of twenty natural amino acids, only one secondary amine containing proline amino acid exhibited revolution in the field of orgnocatalysis, because of its rigid structure and formation of an imine like transition state during the reaction lead more stereoselectivity. Hence, it is referred to as a simple enzyme in organocatalyst. Further discussed chiral organic molecule synthesis by employing oligopeptides derived from the natural amino acids as a robust biocatalyst replaced enzyme catalysts. The peptide includes di-, tri, tetra-, penta- and oligopeptide derived demonstrated as a potential organocatalysts, whose reaction activity and mechanistic pathways are reviewed. Several choice of families of these organocatalysts permit chemist to achieve facile and efficient stereoselective synthesis of many complex natural products with optically pure isomer. Subsequently, researcher developed green and sustainable heterogeneous catalytic system containing organocatalyst immobilized onto solid inorganic supports or porous materials, and is responsible for accelerating the reaction through heterogeneous phase. The developed heterogeneous organocatalysts-MOFs found to be used easier and employed for bulk production and flow reactor synthesis. This review compiled many outstanding discoveries in organocatalysts derived amino acids and it’s heterogenized on to MOFs together role of the organocatalysis in many organic transformations in academic and industrial applications are covered.
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Hao, Yanke, Yu-Lin Lu, Zhiwei Jiao y Cheng-Yong Su. "Photocatalysis Meets Confinement: An Emerging Opportunity for Photoinduced Organic Transformations". Angewandte Chemie, 18 de enero de 2024. http://dx.doi.org/10.1002/ange.202317808.
Resumen
The self‐assembled metal‐organic cages (MOCs) have been evolved as a paradigm of enzyme‐mimic catalysts since they are able to synergize multifunctionalities inherent in metal and organic components and constitute microenvironments characteristic of enzymatic spatial confinement and versatile host‐guest interactions, thus facilitating unconventional organic transformations via unique driving‐forces such as weak noncovalent binding and electron/energy transfer. Recently, MOC‐based photoreactors emerged as a burgeoning platform of supramolecular photocatalysis, displaying anomalous reactivities and selectivities distinct from bulk solution. This perspective recaps two decades journey of the photoinduced radical reactions by using photoactive metal‐organic cages (PMOCs) as artificial reactors, outlining how the cage‐confined photocatalysis was evolved from stoichiometric photoreactions to photocatalytic turnover, from high‐energy UV‐irradiation to sustainable visible‐light photoactivation, and from simple radical reactions to multi‐level chemo‐ and stereoselectivities. We will focus on PMOCs that merge structural and functional biomimicry into a single‐cage to behave as multi‐role photoreactors, emphasizing their potentials in tackling current challenges in organic transformations through single‐electron transfer (SET) or energy transfer (EnT) pathways in a simple, green while feasible manner.
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Hao, Yanke, Yu-Lin Lu, Zhiwei Jiao y Cheng-Yong Su. "Photocatalysis Meets Confinement: An Emerging Opportunity for Photoinduced Organic Transformations". Angewandte Chemie International Edition, 18 de enero de 2024. http://dx.doi.org/10.1002/anie.202317808.
Resumen
The self‐assembled metal‐organic cages (MOCs) have been evolved as a paradigm of enzyme‐mimic catalysts since they are able to synergize multifunctionalities inherent in metal and organic components and constitute microenvironments characteristic of enzymatic spatial confinement and versatile host‐guest interactions, thus facilitating unconventional organic transformations via unique driving‐forces such as weak noncovalent binding and electron/energy transfer. Recently, MOC‐based photoreactors emerged as a burgeoning platform of supramolecular photocatalysis, displaying anomalous reactivities and selectivities distinct from bulk solution. This perspective recaps two decades journey of the photoinduced radical reactions by using photoactive metal‐organic cages (PMOCs) as artificial reactors, outlining how the cage‐confined photocatalysis was evolved from stoichiometric photoreactions to photocatalytic turnover, from high‐energy UV‐irradiation to sustainable visible‐light photoactivation, and from simple radical reactions to multi‐level chemo‐ and stereoselectivities. We will focus on PMOCs that merge structural and functional biomimicry into a single‐cage to behave as multi‐role photoreactors, emphasizing their potentials in tackling current challenges in organic transformations through single‐electron transfer (SET) or energy transfer (EnT) pathways in a simple, green while feasible manner.
28
Jiao, Yuzhen, Yajie Chen, Lu Liu, Xinyan Yu y Guohui Tian. "Engineering of Ultra‐Thin Layer of MIL‐125(Ti) Nanosheet\Zn‐Tetracarboxy‐Phthalocyanine S‐Scheme Heterojunction as Photocatalytic CO2 Reduction Catalyst". Small, 4 de enero de 2024. http://dx.doi.org/10.1002/smll.202309094.
Resumen
AbstractMetal–organic frameworks (MOFs) with ultrathin 2D structure have attracted remarkable attention in photocatalytic application owing to the accessibility of abundant active sites on the surface. But high charge recombination results in poor photocatalytic activity. Herein, the synthesis of ultrathin MIL‐125(Ti) nanosheets is reported with a thickness of 1.3 nm through a simple chemical reaction route of precursor solution aging and subsequent solvothermal process for photocatalytic CO2 production. The maximal CO evolution rate achieves 200.8 µmol g−1 h−1, which is prominently higher than that (78.6 µmol g−1 h−1) of the bulk MIL‐125(Ti) counterpart. Furthermore, the structurally stable Zn (II) tetracarboxy phthalocyanine (ZnTcPc) molecules assembly on ultrathin MIL‐125(Ti) nanosheet (NS) to form MIL‐125(Ti) NS\ZnTcPc S‐scheme heterojunction through the strong interaction between the Ti3+ in MIL‐125(Ti) and the COOH in ZnTcPc. The introduction of ZnTcPc greatly extends light absorption range and increases charge separation rate. The experimental and density functional theory calculation results validate that the MIL‐125(Ti) NS\ZnTcPc S‐scheme heterojunction can favor CO2 adsorption and effectively depress the formation energy of the intermediates, achieving a high CO evolution rate of 450.8 µmol g−1 h−1. This work provides a strategy of engineering 2D MOF‐based heterostructure systems for photocatalytic application.
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He, Dong, Qian Wang, Yan Rong, Zhifeng Xin, Jing‐Jing Liu, Qiang Li, Kejing Shen y Yifa Chen. "Sub‐nanometer Mono‐Layered Metal‐Organic Frameworks Nanosheets for Simulated Flue Gas Photoreduction". Advanced Materials, 18 de abril de 2024. http://dx.doi.org/10.1002/adma.202403920.
Resumen
AbstractThe dilemma between the thickness and accessible active site triggers the design of porous crystalline materials with mono‐layered structure for advanced photo‐catalysis applications. Here, we report a kind of sub‐nanometer mono‐layered nanosheets (Co‐MOF MNSs) through the exfoliation of a specifically designed Co3 cluster‐based metal‐organic frameworks (MOFs). The sub‐nanometer thickness and inherent light‐sensitivity endow Co‐MOF MNSs with fully exposed Janus Co3 sites that can selectively photo‐reduce CO2 into formic acid under simulated flue gas. Notably, the production efficiency of formic acid by Co‐MOF MNSs (0.85 mmol g−1 h−1) is ∼13 times higher than that of bulk counterpart (0.065 mmol g−1 h−1) under simulated flue gas atmosphere, which is highest in reported works up to date. Theoretical calculations prove that the exposed Janus Co3 sites with simultaneously available sites possess higher activity when compared with single Co site, validating the importance of mono‐layered nanosheet morphology. Our results might facilitate the development of functional nanosheet materials for CO2 photo‐reduction in potential flue gas treatment.This article is protected by copyright. All rights reserved
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Panchu, Sarojini Jeeva, Kumar Raju y Hendrik C. Swart. "Emerging Two–Dimensional Intercalation Pseudocapacitive Electrodes for Supercapacitors". ChemElectroChem, 10 de abril de 2024. http://dx.doi.org/10.1002/celc.202300810.
Resumen
AbstractThe growing need for efficient energy storage has spurred advancements in supercapacitors (SCs), aiming to offer high power and energy density simultaneously. While SCs offer longer cycles and higher power density values, their low energy densities limit practical applications. In response, pseudocapacitive materials have emerged, leveraging reversible Faradaic reactions at or near the surface for enhanced energy storage. This approach surpasses the constraints of the electrical double layer in SCs and the mass transfer constraints of batteries. Progress in asymmetric supercapacitors and high mass loading has improved energy density values, yet maintaining high mass loading without compromising power density remains a hurdle. Advancements in pseudocapacitance through intercalation during charging/discharging processes, especially in layered structures like graphite, graphene, transition metal oxides (TMOs) transition metal dichalcogenides (TMDCs), MXenes, and metal–organic frameworks (MOFs) have proven significant. The intercalated species induce reversible or irreversible structural changes, contributing to the physicochemical characteristics of the electrode materials. Exploring the intercalation mechanism in bulk two‐dimensional (2D) materials reveals distinct differences that enhance our understanding and improve electrochemical properties for superior energy storage. Finally, an in‐depth exploration of the intercalation pseudocapacitance in 2D materials such as TMDCs and MXenes underscores their significance, setting a benchmark for future electrochemical studies in the subsequent advancement of SCs research.
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Xiang, Hang, David Baudouin y Frédéric Vogel. "Metal oxide nanoparticles embedded in porous carbon for sulfur absorption under hydrothermal conditions". Scientific Reports 13, n.º 1 (20 de junio de 2023). http://dx.doi.org/10.1038/s41598-023-36395-8.
Resumen
AbstractMOx (M = Zn, Cu, Mn, Fe, Ce) nanoparticles (NPs) embedded in porous C with uniform diameter and dispersion were synthesized, with potential application as S-absorbents to protect catalysts from S-poisoning in catalytic hydrothermal gasification (cHTG) of biomass. S-absorption performance of MOx/C was evaluated by reacting the materials with diethyl disulfide at HTG conditions (450 °C, 30 MPa, 15 min). Their S-absorption capacity followed the order CuOx/C > CeOx/C ≈ ZnO/C > MnOx/C > FeOx/C. S was absorbed in the first four through the formation of Cu1.8S, Ce2S3, ZnS, and MnS, respectively, with a capacity of 0.17, 0.12, 0.11, and 0.09 molS molM−1. The structure of MOx/C (M = Zn, Cu, Mn) evolved significantly during S-absorption reaction, with the formation of larger agglomerates and separation of MOx particles from porous C. The formation of ZnS NPs and their aggregation in place of hexagonal ZnO crystals indicate a dissolution/precipitation mechanism. Note that aggregated ZnS NPs barely sinter under these conditions. Cu(0) showed a preferential sulfidation over Cu2O, the sulfidation of the latter seemingly following the same mechanism as for ZnO. In contrast, FeOx/C and CeOx/C showed remarkable structural stability with their NPs well-dispersed within the C matrix after reaction. MOx dissolution in water (from liquid to supercritical state) was modeled and a correlation between solubility and particle growth was found, comforting the hypothesis of the importance of an Ostwald ripening mechanism. CeOx/C with high structural stability and promising S-absorption capacity was suggested as a promising bulk absorbent for sulfides in cHTG of biomass.