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.

The ever-increasing amount of anthropogenic carbon dioxide (CO2) emissions has resulted in great environmental impacts. The selective hydrogenation of CO2 to methanol, the first target in the liquid sunshine vision, not only effectively mitigates the CO2 emissions, but also produces value-added chemicals and fuels. This critical review provides a comprehensive view of the significant advances in heterogeneous catalysis for methanol synthesis through direct hydrogenation of CO2. The challenges in thermodynamics are addressed first. Then the progress in conventional Cu-based catalysts is discussed in detail, with an emphasis on the structural, chemical, and electronic promotions of supports and promoters, the preparation methods and precursors of Cu-based catalysts, as well as the proposed models for active sites. We also provide an overview of the progress in noble metal-based catalysts, bimetallic catalysts including alloys and intermetallic compounds, as well as hybrid oxides and other novel catalytic systems. The developments in mechanistic aspects, reaction conditions and optimization, as well as reactor designs and innovations are also included. The advances in industrial applications for methanol synthesis are further highlighted. Finally, a summary and outlook are provided.

State of the art and perspectives in heterogeneous catalysis of CO2 hydrogenation to methanol.

Metal-organic frameworks (MOFs) have been widely recognized as one of the most fascinating classes of materials from science and engineering perspectives, benefiting from their high porosity and well-defined and tailored structures and components at the atomic level. Although their intrinsic micropores endow size-selective capability and high surface area, etc., the narrow pores limit their applications toward diffusion-control and large-size species involved processes. In recent years, the construction of hierarchically porous MOFs (HP-MOFs), MOF-based hierarchically porous composites, and MOF-based hierarchically porous derivatives has captured widespread interest to extend the applications of conventional MOF-based materials. In this Review, the recent advances in the design, synthesis, and functional applications of MOF-based hierarchically porous materials are summarized. Their structural characters toward various applications, including catalysis, gas storage and separation, air filtration, sewage treatment, sensing and energy storage, have been demonstrated with typical reports. The comparison of HP-MOFs with traditional porous materials (e.g., zeolite, porous silica, carbons, metal oxides, and polymers), subsisting challenges, as well as future directions in this research field, are also indicated.

Metal-Organic Framework-Based Hierarchically Porous Materials: Synthesis and Applications.

Surfactants as promising media in the field of metal-organic frameworks

Tetrahydroquinoline is one of the most important simple nitrogen heterocycles, being widespread in nature and present in a broad variety of pharmacologically active compounds. This Review summarizes the progress achieved in the chemistry of tetrahydroquinolines, with emphasis on their synthesis, during the period from mid-2010 to early 2018.

Progress in the Chemistry of Tetrahydroquinolines.

Direct hydrogenation of CO2 to methanol under milder conditions is of great importance. In this work, the catalytic performances of Au particles with different sizes on various supports for this reaction were studied. It was demonstrated that catalytic properties of the catalysts depended both on size of Au particles and the composition of the supports. The Au/ZrO2 with subnanometric Au particles (1.6 nm) had unprecedented high catalytic activity and excellent selectivity for the reaction, and methanol could be obtained even at 140 oC, which is obviously lower than those reported in the literature. The outstanding performance of the Au/ZrO2 with subnanometric Au particles resulted from both very small size of the Au particles and appropriate coupling between the Au particles and the support.

Efficient Hydrogenation of CO2 to Methanol over Supported Subnanometer Gold Catalysts at Low Temperature

In this work, we developed a strategy to in situ synthesize sub-nanometer metal particle/hierarchically mesoporous metal–organic framework (MOF) composites in emulsion. In this route, water droplets in the emulsion acted as both a solvent of the metal precursors and a template for the hierarchical mesopores of MOFs, and the surfactant was an emulsifier and a reductant for generating metal particles. Au/Zn-MOFs (MOFs formed by Zn2+ and methylimidazole), Ru/Zn-MOFs, Pd/Zn-MOFs, and Au/Cu-MOFs (MOFs formed by Cu2+ and methylimidazole) were prepared using this method, in which ultrafine metal particles (e.g. 0.8 nm) were immobilized uniformly on hierarchically mesoporous MOFs. Au/Zn-MOFs and Au/Cu-MOFs showed outstanding catalytic performances for the selective aerobic oxidation of cyclohexene to 2-cyclohexen-1-one in the absence of an initiator, and Ru/Zn-MOFs were very active and selective for the hydrogenation of diphenyl sulfoxide to diphenyl sulfide. In addition, the catalysts were also very stable in the reactions.

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In situ synthesis of sub-nanometer metal particles on hierarchically porous metal–organic frameworks via interfacial control for highly efficient catalysis

Driving dimethyl carbonate synthesis from CO2 and methanol and production of acetylene simultaneously using CaC2

N -methyl-tetrahydroquinolines (MTHQs) are a kind of very useful chemicals, which can be obtained from N -methylation of amines. However, the methylation of quinolines which is a kind of highly unsaturated nitrogen-containing heterocyclic aromatic compounds has not been reported. In this work, we report the first work for the synthesis of MTHQs by methylation of quinolines using CO2 and H2. It was found that Ru(acac)3-triphos [triphos: 1,1,1-tris(diphenylphosphinomethyl)ethanl] complex was very active and selective for the N -methylation reaction of quinolines, and the yield of the desired product could reach 99%.

Lujun Zhang

Papers

Efficient Hydrogenation of CO2 to Methanol over Supported Subnanometer Gold Catalysts at Low Temperature

In situ synthesis of sub-nanometer metal particles on hierarchically porous metal–organic frameworks via interfacial control for highly efficient catalysis

Driving dimethyl carbonate synthesis from CO2 and methanol and production of acetylene simultaneously using CaC2

N -methylation of quinolines with CO 2 and H 2 catalyzed by Ru-triphos complexes

Efficient emulsifying properties of glycerol-based surfactant