Metal-organic framework (MOF) nanoparticles, also called porous coordination polymers, are a major part of nanomaterials science, and their role in catalysis is becoming central. The extraordinary variability and richness of their structures afford engineering synergies between the metal nodes, functional linkers, encapsulated substrates, or nanoparticles for multiple and selective heterogeneous interactions and activations in these MOF-based nanocatalysts. Pyrolysis of MOF-nanoparticle composites forms highly porous N- or P-doped graphitized MOF-derived nanomaterials that are increasingly used as efficient catalysts especially in electro- and photocatalysis. This review first briefly summarizes this background of MOF nanoparticle catalysis and then comprehensively reviews the fast-growing literature reported during the last years. The major parts are catalysis of organic and molecular reactions, electrocatalysis, photocatalysis, and views of prospects. Major challenges of our society are addressed using these well-defined heterogeneous catalysts in the fields of synthesis, energy, and environment. In spite of the many achievements, enormous progress is still necessary to improve our understanding of the processes involved beyond the proof-of-concept, particularly for selective methane oxidation, hydrogen production, water splitting, CO2 reduction to methanol, nitrogen fixation, and water depollution.

State of the Art and Prospects in Metal-Organic Framework (MOF)-Based and MOF-Derived Nanocatalysis.

Metal-organic frameworks (MOFs) are a class of distinctive porous crystalline materials constructed by metal ions/clusters and organic linkers. Owing to their structural diversity, functional adjustability, and high surface area, different types of MOF-based single metal sites are well exploited, including coordinately unsaturated metal sites from metal nodes and metallolinkers, as well as active metal species immobilized to MOFs. Furthermore, controllable thermal transformation of MOFs can upgrade them to nanomaterials functionalized with active single-atom catalysts (SACs). These unique features of MOFs and their derivatives enable them to serve as a highly versatile platform for catalysis, which has actually been becoming a rapidly developing interdisciplinary research area. In this review, we overview the recent developments of catalysis at single metal sites in MOF-based materials with emphasis on their structures and applications for thermocatalysis, electrocatalysis, and photocatalysis. We also compare the results and summarize the major insights gained from the works in this review, providing the challenges and prospects in this emerging field.

Metal-Organic Framework-Based Catalysts with Single Metal Sites.

A novel OER electrocatalyst, namely oxygen-incorporated amorphous cobalt sulfide porous nanocubes (A-CoS4.6 O0.6 PNCs), show advantages over the benchmark RuO2 catalyst in alkaline/neutral medium. Experiments combining with calculation demonstrate that the desirable O* adsorption energy, associated with the distorted CoS4.6 O0.6 octahedron structure and the oxygen doping, contribute synergistically to the outstanding electrocatalytic activity.

Oxygen-Containing Amorphous Cobalt Sulfide Porous Nanocubes as High-Activity Electrocatalysts for the Oxygen Evolution Reaction in an Alkaline/Neutral Medium

Metal organic frameworks (MOFs) are considered as a group of compounds, either metal ions or clusters, harmonized with organic ligands to form one or some dimensional structures. In addition to resilient bonds between inorganic and organic units, reticular synthesis creates MOFs, accurate selection of constituents of which can produce high thermal and chemical stability and crystals of ultrahigh porosity. Other solids have not shown the same accuracy normally used in chemical modification and even the capability of increasing their metrics with no modification of the underlying topology. With shape of building units and chemical compositions multiplying based on specific structures, MOFs might result in compounds that propose a synergistic mixture of features. This study presents up to date advances in both synthesis methods of MOFs and structural characteristics. Furthermore, the use of MOFs in different fields such as the removal of absorption and separation of toxic substances from gas and liquid, catalysts, a variety of sensors, storage of clean energies and environmental applications, medical and biological applications, and optoelectronic equipment is included.

A review on metal-organic frameworks: Synthesis and applications

Application of doped photocatalysts for organic pollutant degradation - A review

Semisacrificial Template Growth of Self-Supporting MOF Nanocomposite Electrode for Efficient Electrocatalytic Water Oxidation

Electrochemical reduction of CO2 to valuable fuels is appealing for CO2 fixation and energy storage. However, the development of electrocatalysts with high activity and selectivity in a wide potential window is challenging. Herein, atomically thin bismuthene (Bi-ene) is pioneeringly obtained by an in situ electrochemical transformation from ultrathin bismuth-based metal-organic layers. The few-layer Bi-ene, which possesses a great mass of exposed active sites with high intrinsic activity, has a high selectivity (ca. 100 %), large partial current density, and quite good stability in a potential window exceeding 0.35 V toward formate production. It even deliver current densities that exceed 300.0 mA cm-2 without compromising selectivity in a flow-cell reactor. Using in situ ATR-IR spectra and DFT analysis, a reaction mechanism involving HCO3- for formate generation was unveiled, which brings new fundamental understanding of CO2 reduction.

Metal-Organic Layers Leading to Atomically Thin Bismuthene for Efficient Carbon Dioxide Electroreduction to Liquid Fuel.

A highly ordered ZnO/TiO2 photonic crystal (ZnO/TiO2-PC) was obtained by a simply pyrolysis strategy. Combined with a series of characterizations, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and transmittance spectra, it was found that the in situ formed ZnO phases were uniformly grafted to TiO2-PC framework forming hybrid nanostructure. Additionally, the formation of heterojunction between ZnO and TiO2-PC enhanced the separation efficiency of photogenerated electron–hole pairs, which significantly improved the photocatalytic performances. Based on the results of photoelectrochemical measurement and the detection of active species in photocatalytic degradation process, the photocatalytic degradation mechanism of ZnO/TiO2-PC nanocomposite was proposed. It is hoped that our work could provide a good insight into the preparation of photonic crystal heterostructures for the environmental purification.

Construction of ZnO/TiO2 photonic crystal heterostructures for enhanced photocatalytic properties

Nitrogen-doped and carbon species decorated TiO2 composites (Cts/TiO2) are prepared by using chitosan as a natural nitrogen and carbon source to combine with TiO2 by a facile and low-cost method for the first time. Their structures and properties are characterized by X-ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy (DRS), Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), N2 adsorption–desorption isotherms (BET), and electron spin resonance spectroscopy (ESR). The results show that the visible light absorption range of the composites even can be extended to 650 nm. Photocatalytic degradation of Rhodamine B (RhB) under visible light (420 nm  −) play the most important role, then the probable degradation mechanism of the photocatalysts is proposed simultaneously. It is hoped that our work will open a new doorway to use a simple and green method to get high-efficiency TiO2-based photocatalysts.

Changsheng Cao

Papers

Semisacrificial Template Growth of Self-Supporting MOF Nanocomposite Electrode for Efficient Electrocatalytic Water Oxidation

Metal-Organic Layers Leading to Atomically Thin Bismuthene for Efficient Carbon Dioxide Electroreduction to Liquid Fuel.

Construction of ZnO/TiO2 photonic crystal heterostructures for enhanced photocatalytic properties

Investigation of nitrogen doped and carbon species decorated TiO2 with enhanced visible light photocatalytic activity by using chitosan

FeCo Alloy Nanoparticles Confined in Carbon Layers as High-activity and Robust Cathode Catalyst for Zn-Air Battery