Metal Organic Framework Catalysis Research Articles

New Opportunities in Metal Organic Framework Catalysis: From Bifunctional to Frustrated Lewis Pairs Catalysis.

This article highlights novel prospects for metal-organic frameworks (MOFs) in heterogeneous catalysis as having frustrated Lewis acid-base pairs (FLPs) or as bifunctional acid-base solid catalysts able to activate molecular hydrogen. Starting from the extensive application MOFs as Lewis acid and Lewis base catalysts, this article uses catalytic hydrogenation to briefly summarize the efforts made to heterogenize boron and amine in MOFs to mimic molecular FLP systems. The core of this concept is based on recent findings1 which demonstrate the ability of two commonly used MOFs, namely UiO-66 and MIL-101, to catalyze the selective hydrogenation of polar double X=Y bonds at moderate H2 pressures below 10 bar. The influence of electron-donating, the withdrawal of substituents on the linker, and the aniline poisoning effect highlight the significance of Lewis acid sites, while density-functional theory calculations indicate the heterolytic H-H bond cleavage at the MOF metal oxo clusters. It is expected that this new perspective on MOFs as solid FLP systems will spur further research to explore and define the potential of dual sites in the catalytic activation of small molecules.

Bioinspired Framework Catalysts: From Enzyme Immobilization to Biomimetic Catalysis.

Enzymatic catalysis has fueled considerable interest from chemists due to its high efficiency and selectivity. However, the structural complexity and vulnerability hamper the application potentials of enzymes. Driven by the practical demand for chemical conversion, there is a long-sought quest for bioinspired catalysts reproducing and even surpassing the functions of natural enzymes. As nanoporous materials with high surface areas and crystallinity, metal-organic frameworks (MOFs) represent an exquisite case of how natural enzymes and their active sites are integrated into porous solids, affording bioinspired heterogeneous catalysts with superior stability and customizable structures. In this review, we comprehensively summarize the advances of bioinspired MOFs for catalysis, discuss the design principle of various MOF-based catalysts, such as MOF-enzyme composites and MOFs embedded with active sites, and explore the utility of these catalysts in different reactions. The advantages of MOFs as enzyme mimetics are also highlighted, including confinement, templating effects, and functionality, in comparison with homogeneous supramolecular catalysts. A perspective is provided to discuss potential solutions addressing current challenges in MOF catalysis.

Kinetic Impacts of Defect Sites in Metal–Organic Framework Catalysts under Varied Driving Forces

Defects in metal–organic frameworks (MOFs) primarily manifest as missing linkers or metal nodes induced through synthesis, post-synthetic modification, and/or exposure to reaction conditions. By changing the nature of active site(s) and perturbing crystalline frameworks, defects confer physicochemical alterations to MOF catalysts that may promote or inhibit intrinsic reactivity, electron transfer and excitation, and mass transport. However, the complexity and dynamic character of defects often obfuscate the structure–function relations needed to permit rational catalyst design. Here, highlights of recent studies examining the impact of MOF defects in thermo-, photo-, and electrocatalytic systems pertinent to energy applications demonstrate progress toward identifying defect impacts on MOF catalysis, particularly for widely studied zirconium-based frameworks. Moreover, the combination of ex situ and operando/in situ defect identification and quantification will be paramount in future research to improve the mechanistic understanding of MOF-catalyzed systems for energy conversion but also extends to MOF energy storage, photovoltaics, and gas separations/storage applications.

High-Throughput Experimentation, Theoretical Modeling, and Human Intuition: Lessons Learned in Metal-Organic-Framework-Supported Catalyst Design.

We have screened an array of 23 metals deposited onto the metal-organic framework (MOF) NU-1000 for propyne dimerization to hexadienes. By a first-of-its-kind study utilizing data-driven algorithms and high-throughput experimentation (HTE) in MOF catalysis, yields on Cu-deposited NU-1000 were improved from 0.4 to 24.4%. Characterization of the best-performing catalysts reveal conversion to hexadiene to be due to the formation of large Cu nanoparticles, which is further supported by reaction mechanisms calculated with density functional theory (DFT). Our results demonstrate both the strengths and weaknesses of the HTE approach. As a strength, HTE excels at being able to find interesting and novel catalytic activity; any a priori theoretical approach would be hard-pressed to find success, as high-performing catalysts required highly specific operating conditions difficult to model theoretically, and initial simple single-atom models of the active site did not prove representative of the nanoparticle catalysts responsible for conversion to hexadiene. As a weakness, our results show how the HTE approach must be designed and monitored carefully to find success; in our initial campaign, only minor catalytic performances (up to 4.2% yield) were achieved, which were only improved following a complete overhaul of our HTE approach and questioning our initial assumptions.

MOF catalysis meets biochemistry: molecular insights from the hydrolytic activity of MOFs towards biomolecules

The versatility of metal–organic frameworks (MOF) towards hydrolysis of a range of biological molecules is explored in detail to underline specific challenges and exciting possibilities of developing MOFs as nanozymes.

A Potential Roadmap to Integrated Metal Organic Framework Artificial Photosynthetic Arrays.

Metal organic frameworks (MOFs), a class of coordination polymers, gained popularity in the late 1990s with the efforts of Omar Yaghi, Richard Robson, Susumu Kitagawa, and others. The intrinsic porosity of MOFs made them a clear platform for gas storage and separation. Indeed, these applications have dominated the vast literature in MOF synthesis, characterization, and applications. However, even in those early years, there were hints to more advanced applications in light-MOF interactions and catalysis. This perspective focuses on the combination of both light–MOF interactions and catalysis: MOF artificial photosynthetic assemblies. Light absorption, charge transport, H2O oxidation, and CO2 reduction have all been previously observed in MOFs; however, work toward a fully MOF-based approach to artificial photosynthesis remains out of reach. Discussed here are the current limitations with MOF-based approaches: diffusion through the framework, selectivity toward high value products, lack of integrated studies, and stability. These topics provide a roadmap for the future development of fully integrated MOF-based assemblies for artificial photosynthesis.

Development of soluble UiO-66 to improve photocatalytic CO2 reduction

The conversion of CO2 to valuable chemicals by photocatalysis has attracted widespread interesting. Owing to the linear structure of CO2 molecule with strong CO bond, the surface reaction is considered as one of the main issues to restrict the conversion efficiency. Herein, soluble UiO-66 has been developed as co-catalyst to enhance the photocatalytic performance for CO2 reduction. The soluble UiO-66 has presented the performance ca. 1.5 higher than the insoluble version, yielding 30.6 µmol/h for CO2 to CO conversion by using 5.0 mg sample. This improvement can be attributed to the preserved framework by soluble UiO-66. Therefore, the chemisorption of CO2 molecules can be improved, boosting the reduction reaction for CO production. This research provides a new path for a rational design of metal-organic framework (MOF) for photoredox catalysis, meanwhile inspiring advanced application of MOF catalysis with the soluble manner.

Corrigendum to “Propargylamine synthesis via direct oxidative C-C coupling reaction between N,N-dimethylanilines and terminal alkynes under metal-organic framework catalysis” [Journal of Molecular Catalysis A: Chemical 395 (2014) 300–306

Corrigendum to “Propargylamine synthesis via direct oxidative C-C coupling reaction between N,N-dimethylanilines and terminal alkynes under metal-organic framework catalysis” [Journal of Molecular Catalysis A: Chemical 395 (2014) 300–306

Corrigendum to “Direct C-N coupling of azoles with ethers via oxidative C-H activation under metal-organic framework catalysis” [J. Ind. Eng. Chem. 44 (2016) 136–145

Corrigendum to “Direct C-N coupling of azoles with ethers via oxidative C-H activation under metal-organic framework catalysis” [J. Ind. Eng. Chem. 44 (2016) 136–145

Programmable Logic in Metal-Organic Frameworks for Catalysis.

Metal-organic frameworks (MOFs) have emerged as one of the most widely investigated materials in catalysis mainly due to their excellent component tunability, high surface area, adjustable pore size, and uniform active sites. However, the overwhelming number of MOF materials and complex structures has brought difficulties for researchers to select and construct suitable MOF-based catalysts. Herein, a programmable design strategy is presented based on metal ions/clusters, organic ligands, modifiers, functional materials, and post-treatment modules, which can be used to design the components, structures, and morphologies of MOF catalysts for different reactions. By establishing the corresponding relationship between these modules and functions, researchers can accurately and efficiently construct heterometallic MOFs, chiral MOFs, conductive MOFs, hierarchically porous MOFs, defective MOFs, MOF composites, and MOF-derivative catalysts. Further, this programmable design approach can also be used to regulate the physical/chemical microenvironments of pristine MOFs, MOF composites, and MOF-derivative materials for heterogeneous catalysis, electrocatalysis, and photocatalysis. Finally, the challenging issues and opportunities for the future research of MOF-based catalysts are discussed. Overall, the modular design concept of this review can be applied as a potent tool for exploring the structure-activity relationships and accelerating the on-demand design of multicomponent catalysts.

Corrigendum to “Synthesis of α-acyloxy ethers via direct esterification of carboxylic acids with ethers under metal-organic framework catalysis” [Tetrahedron 73 (2017) 5883

Corrigendum to “Synthesis of α-acyloxy ethers via direct esterification of carboxylic acids with ethers under metal-organic framework catalysis” [Tetrahedron 73 (2017) 5883

Corrigendum to “Synthesis of aryl-substituted pyridines via cyclization of N,N-dialkylanilines with ketoxime carboxylates under metal-organic framework catalysis” [J. Ind. Eng. Chem. 54 (2017) 151–161

Corrigendum to “Synthesis of aryl-substituted pyridines via cyclization of N,N-dialkylanilines with ketoxime carboxylates under metal-organic framework catalysis” [J. Ind. Eng. Chem. 54 (2017) 151–161

Computational catalysis for metal-organic frameworks: An overview

Metal-organic frameworks (MOFs), a family of porous hybrid organic/inorganic materials, have shown great promise for many challenging chemical applications including gas separations, catalysis, and sensors. Numerous recent articles explore the field of catalytically active MOFs at an experimental and computational level. The stability, porosity, and periodic nature of MOFs allow them to act as both the active catalyst as well as supporting material to single atoms or small metal clusters. This review highlights recent work performed on catalytic reactions promoted by MOFs from a computational and theoretical standpoint. Computational modeling includes the elucidation of reaction mechanisms, the characterization of electronic structure effects of key intermediates and transition states, and the interpretation of experimental data. These topics are covered in this review article, and examples from the recent literature are presented. Studies that aim to better understand structure–function relations such as descriptors of catalytic activity have the potential to contribute to the design of new MOF catalysts are also included. We believe that the future of computational MOF catalysis will involve the use of high-throughput virtual screening and machine learning methods, some aspects of which are discussed in the current review.

Exploitation of Intrinsic Confinement Effects of MOFs in Catalysis

AbstractIn catalysis research the design of bio‐inspired,'artificial enzymes‘ is a field of huge interest. These catalysts are distinguished by their high catalytic efficiency resulting from a close proximity of several active sites and secondary substrate‐catalyst interactions enabled by functional groups in the catalytic pocket. A class of materials which meets these requirements are metal‐organic frameworks (MOFs). Here, the pores confine a reaction environment where several functionalities can be incorporated and spatially positioned in a tunable fashion. Recently, a number of reports revealed the importance of such confinement effects for the control of catalytic activity and selectivity by exploiting the intrinsic properties like pore size and neighboring group effects and the alignment and distance of different active sites within one MOF pore. Thus, this concept aims to accentuate the potential of the exploitation of those effects in MOFs for the design of sophisticated catalysts.

Effect of superabsorbent polymers (SAP) and metal organic frameworks (MOF) wiping sandwich patch on human skin decontamination and detoxification in vitro

Most chemical warfare agents partition rapidly into stratum corneum (SC) and subsequently slowly diffuse through – or are retained in the membrane. Since chemicals can interact with SC components during the process, skin decontamination poses a challenging yet important problem. To address these issues, we have developed a new method in combination with wet and dry decon technologies with new materials for emergency or delayed contamination scenarios. An in vitro human skin diffusion system was employed to model various dermal exposures of radiolabeled chemical warfare simulants, followed by surface decontamination with metal organic frameworks (MOFs), super-absorbent polymers (SAP), and/or dermal decontamination gel (DDGel). All samples measured for radioactive recovery and acetylcholinesterase activity to ascertain relative decon efficacy. Results demonstrated powerful water absorption of SAP, strong catalysis of UiO-66 MOF, and decon enhancement of pre-wetting surface contaminants. SAP had no interfering interactions with MOF yet provided additional benefits as porosity and reactivity that allowed for fast liquidized chemical transportation, absorption, and degeneration. We then designed a cotton-based SAP/MOF patch that worked cooperatively in decontamination and detoxification. Together with pre-wet, SAP/MOF wipe, and DDGel applications, maximum effect was observed in early and/or extended dermal exposure, and no “wash-in” effect occurred.

Catalytic Activation of Cobalt Doping Sites in ZIF-71-Coated ZnO Nanorod Arrays for Enhancing Gas-Sensing Performance to Acetone.

Developing acetone gas sensors with high sensitivity is crucially important for many applications including nonevasive diagnosis of diabetes. In the present work, cobalt doping is used to catalyze acetone gas-sensing reactions and hence to promote the sensitivity of acetone gas sensors. In order to achieve this, ZIF-71 metal-organic framework (MOF) is synthesized onto ZnO nanorod arrays with various concentrations of Co doping to form composite ZnO@ZIF-71(Co) sensors, which are then evaluated as sensing materials for acetone detection. Such sensors are shown to be sensitive to a trace amount of acetone (50 ppb) and have a massively enhanced response of about 100 times that for the undoped sensor at an optimal Co/Zn ratio and operating temperature. Fourier-transform infrared spectroscopy and temperature-programmed desorption with density functional theory calculations are also made to assist in elucidating the catalytic gas-sensing mechanism for the Co-doped composite sensors ZnO@ZIF-71(Co). It demonstrated that the introduced Co site in ZIF-71(Co) can activate oxygen catalytically and increase active oxygen released to the ZnO surface. Meanwhile, the Co sites also promote the decomposition of acetone. These two steps together affect the catalytic oxidation of gases and finally enhance the sensitivity. This work introduces the catalytic effect of the MOF into the gas-sensing mechanism and provides an idea for broadening the application of MOF catalysis.

Metal-Organic Frameworks Based on Group 3 and 4 Metals.

Metal-organic frameworks (MOFs) based on group 3 and 4 metals are considered as the most promising MOFs for varying practical applications including water adsorption, carbon conversion, and biomedical applications. The relatively strong coordination bonds and versatile coordination modes within these MOFs endow the framework with high chemical stability, diverse structures and topologies, and interesting properties and functions. Herein, the significant progress made on this series of MOFs since 2018 is summarized and an update on the current status and future trends on the structural design of robust MOFs with high connectivity is provided. Cluster chemistry involving Y, lanthanides (Ln, from La to Lu), actinides (An, from Ac to Lr), Ti, and Zr is initially introduced. This is followed by a review of recently developed MOFs based on group 3 and 4 metals with their structures discussed based on the types of inorganic or organic building blocks. The novel properties and arising applications of these MOFs in catalysis, adsorption and separation, delivery, and sensing are highlighted. Overall, this review is expected to provide a timely summary on MOFs based on group 3 and 4 metals, which shall guide the future discovery and development of stable and functional MOFs for practical applications.

Tuning Zr12O22 Node Defects as Catalytic Sites in the Metal–Organic Framework hcp UiO-66

Defects in metal–organic frameworks (MOFs) play important roles in MOF reactivity and catalysis. Now, we report evidence of the reactivity and the quantitative characterization of the missing linke...

Potential Utilization of Metal-Organic Frameworks in Heterogeneous Catalysis: A Case Study of Hydrogen-Bond Donating and Single-Site Catalysis.

Crystalline solid materials are platforms for the development of effective catalysts and have shown vast benefits at the frontiers between homogeneous and heterogeneous catalysts. Typically, these crystalline solid catalysts outperformed their homogeneous analogs due to their high stability, selectivity, better catalytic activity, reusability and recyclability in catalysis applications. This point of view, comprising significant features of a new class of porous crystalline materials termed as metal-organic frameworks (MOFs) engendered the attractive pathway to synthesize functionalized heterogeneous MOF catalysts. The present review includes the recent research progress in developing both hydrogen-bond donating (HBD) MOF catalysts and MOF-supported single-site catalysts (MSSCs). The first part deals with the novel designs of urea-, thiourea- and squaramide-containing MOF catalysts and study of their crucial role in HBD catalysis. In the second part, we discuss the important classification of MSSCs with existing examples and their use in desired catalytic reactions. In addition, we describe the relative catalytic efficiency of these MSSCs with their homogeneous and similarly reported analogs. The precise knowledge of discussed heterogeneous MOF catalysts in this review may open the door for new research advances in the field of MOF catalysis.

Computational Studies of Photocatalysis with Metal–Organic Frameworks

Metal–organic frameworks (MOFs) as photocatalysts and photocatalyst supports combine several advantages of homogeneous and heterogeneous catalyses, including stability, post‐reaction separation, catalyst reusability, and tunability, and they have been intensively studied for photocatalytic applications. There are several reviews that focus mainly or even entirely on experimental work. The present review is intended to complement those reviews by focusing on computational work that can provide a further understanding of the photocatalytic properties of MOF photocatalysts. We first present a summary of computational methods, including density functional theory, combined quantum mechanical and molecular mechanical methods, and force fields for MOFs. Then, computational investigations on MOF‐based photocatalysis are briefly discussed. The discussions focus on the electronic structure, photoexcitation, charge mobility, and photoredox catalysis of MOFs, especially the widely studied UiO‐66‐based MOFs.