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 high carrier recombination rate and serious photocorrosion of Ag3PO4 greatly restrict its photocatalytic application. Here, we fabricated an Ag3PO4/Ti3C2 Schottky catalyst and found that Ti3C2 can greatly enhanced the catalytic activity and stability of Ag3PO4. This arises from: (i) the abundant surface hydrophilic functional groups of Ti3C2 construct strong interfacial contact with Ag3PO4, which facilitate the separation of carriers; (ii) the strong redox reactivity of surface Ti sites promote multiple electron reduction reactions to induce more OH production; and (iii) a Schottky junction formed at Ag3PO4-Ti3C2 interface timely transfer electrons to Ti3C2 surface by built-in electric field, inhibiting the photocossion of Ag3PO4 caused by photogeneration electrons. Consequently, Ag3PO4/Ti3C2 exhibited excellent photocatalytic activity and stability for the degradation of organic pollutants. Especially, the apparent rate constant of 2,4-Dinitrophenol degradation with Ag3PO4/Ti3C2 was 2.5 times that of Ag3PO4/RGO and 10 times that of Ag3PO4. The photocatalytic performance of Ag3PO4/Ti3C2 toward tetracycline hydrochloride still maintained 68.4% after 8 cycles, while Ag3PO4/RGO and Ag3PO4 only maintained 36.2% and 7.8%, respectively. Furthermore, the efficient photoreduction of Cr6+ using AgI/Ti3C2 further illustrated an enormous potential in coupling Ti3C2 with other photosensitivity semiconductor to improve their catalytic activity and stability.

Ag3PO4/Ti3C2 MXene interface materials as a Schottky catalyst with enhanced photocatalytic activities and anti-photocorrosion performance

As emerging crystalline porous organic-inorganic hybrid materials, metal-organic frameworks (MOFs) have been widely used as sacrificial precursors for the synthesis of carbon materials, metal/metal compounds, and their composites with tunable and controllable nanostructures and chemical compositions for electrochemical energy applications. Herein, recent progress of MOF-derived nanomaterials for various electrochemical energy storage and conversion applications including Li-ion batteries, Li-S batteries, Na-ion batteries, supercapacitors, water splitting, and oxygen reduction reaction is reviewed. Structural and compositional design of MOF-derived nanomaterials is systematically summarized, which may hopefully offer inspirations and guidances for future development of MOF-derived nanomaterials for more efficient and more durable electrochemical energy applications.

Metal-organic framework-derived materials for electrochemical energy applications

g-C3N4/carbon dot-based nanocomposites serve as efficacious photocatalysts for environmental purification and energy generation: A review

Carbon materials derived from metal-organic frameworks (MOFs) have attracted much attention in the field of scientific research in recent years because of their advantages of excellent electron conductivity, high porosity, and diverse applications. Tremendous efforts are devoted to improving their chemical and physical properties, including optimizing the morphology and structure of the carbon materials, compositing them with other materials, and so on. Here, many kinds of carbon materials derived from metal-organic frameworks are introduced with a particular focus on their promising applications in batteries (lithium-ion batteries, lithium-sulfur batteries, and sodium-ion batteries), supercapacitors (metal oxide/carbon and metal sulfide/carbon), electrocatalytic reactions (oxygen reduction reaction, oxygen evolution reaction, and hydrogen evolution reaction), water treatment (MOF-derived carbon and other techniques), and other possible fields. To close, some existing problem and corresponding possible solutions are proposed based on academic knowledge from the reported literature, along with a great deal of experimental experience.

Applications of Metal-Organic-Framework-Derived Carbon Materials.

In this work, an all solid Z-scheme g-C3N4/Ag3PO4/NCDs photocatalyst has been prepared through decorating the direct Z-scheme g-C3N4/Ag3PO4 photocatalyst with nitrogen-doped carbon dots (NCDs). The g-C3N4/Ag3PO4/NCDs photocatalyst exhibits excellent photocatalytic activity for the degradation of methylene blue (MB), rhodamine B (RhB) and phenol under visible light irradiation. The solutions of MB (10 mg L−1) and RhB (10 mg L−1) can be efficiently degraded within 20 min and 15 min, respectively, and the phenol (50 mg L−1) can be degraded to 36% within 80 min, which are much better than those of Ag3PO4 and g-C3N4/Ag3PO4, indicating that the introduction of NCDs into g-C3N4/Ag3PO4 can effectively improve the photocatalytic activity. Moreover, the photocatalytic performance of g-C3N4/Ag3PO4/NCDs shows just a slight decrease after four degradation cycles, indicating a high stability of the g-C3N4/Ag3PO4/NCDs photocatalyst. A possible photocatalytic mechanism based on the experimental results is proposed. It is revealed that NCDs on the ternary g-C3N4/Ag3PO4/NCDs can enhance the light harvesting capacity and molecular oxygen activation ability of the photocatalyst, and serve as excellent electronic transmission medium to promote the transfer and separation of photo-generated electron-hole pairs. This study demonstrates that NCDs decorated photocatalysts are very promising for environment and related applications.

Nitrogen-doped carbon dots decorated on g-C3N4/Ag3PO4 photocatalyst with improved visible light photocatalytic activity and mechanism insight

FeCo-based materials are promising candidates as efficient, affordable, and sustainable electrocatalysts for oxygen evolution reaction (OER). Herein, a composite based on FeSe2@CoSe2 particles supported on reduced graphene oxide (rGO) was successfully prepared as an OER catalyst. In the catalyst, the CoSe2 phase was located on the FeSe2 surface, forming a large number of exposed heterointerfaces with acidic iron sites because of strong charge interaction between CoSe2 and FeSe2. It is believed that the exposed heterointerfaces act as catalytic active sites for OER via a two-site mechanism, manifesting an overpotential as low as 260 mV to reach the current density of 10 mA cm–2 in 1 M KOH and excellent stability for at least 6 h, which is superior to those of CoSe2/rGO, FeSe2/rGO, as well as most of the FeNi- and FeCo-based electrocatalysts reported in recent literatures. It was demonstrated that the most optimal composite electrocatalysts release more Fe species into the electrolyte during the OER process...

Nanocomposites Based on CoSe2-Decorated FeSe2 Nanoparticles Supported on Reduced Graphene Oxide as High-Performance Electrocatalysts toward Oxygen Evolution Reaction.

Developing cheap, abundant, and easily available electrocatalysts to drive the hydrogen evolution reaction (HER) at small overpotentials is an urgent demand of hydrogen production from water splitting. Molybdenum disulfide (MoS2 ) based composites have emerged as competitive electrocatalysts for HER in recent years. Herein, nickel@nitrogen-doped carbon@MoS2 nanosheets (Ni@NC@MoS2 ) hybrid sub-microspheres are presented as HER catalyst. MoS2 nanosheets with expanded interlayer spacings are vertically grown on nickel@nitrogen-doped carbon (Ni@NC) substrate to form Ni@NC@MoS2 hierarchical sub-microspheres by a simple hydrothermal process. The formed Ni@NC@MoS2 composites display excellent electrocatalytic activity for HER with an onset overpotential of 18 mV, a low overpotential of 82 mV at 10 mA cm-2 , a small Tafel slope of 47.5 mV dec-1 , and high durability in 0.5 H2 SO4 solution. The outstanding HER performance of the Ni@NC@MoS2 catalyst can be ascribed to the synergistic effect of dense catalytic sites on MoS2 nanosheets with exposed edges and expanded interlayer spacings, and the rapid electron transfer from Ni@NC substrate to MoS2 nanosheets. The excellent Ni@NC@MoS2 electrocatalyst promises potential application in practical hydrogen production, and the strategy reported here can also be extended to grow MoS2 on other nitrogen-doped carbon encapsulated metal species for various applications.

Nickel@Nitrogen-Doped Carbon@MoS2 Nanosheets: An Efficient Electrocatalyst for Hydrogen Evolution Reaction.

In this work, CoMoO4/Co3O4 hollow porous octahedrons are synthesized by thermal conversion of a cyanide-metal framework (CMF) compound of Co2[Mo(CN)8]·xH2O. As anode materials for lithium ion batteries (LIBs), the CoMoO4/Co3O4 electrodes exhibit a remarkably improved electrochemical performance in terms of large lithium storage capacity (1175.1 mA h g−1 at 200 mA g−1), high initial coulombic efficiency (86.9%), outstanding cycling stability (96.9% capacity retention after 100 cycles) and remarkable rate capability (924.2 mA h g−1 at 2000 mA g−1). The excellent electrochemical performance of the CoMoO4/Co3O4 composite can be ascribed to the hollow porous structure and the possible synergistic effect of different components, which could provide more efficient charge storage sites, shorten ion diffusion and electron transport paths, and accommodate the volume change during cycling. The facile synthesis strategy and excellent lithium storage performance make the CoMoO4/Co3O4 hollow porous octahedrons a promising candidate for high-performance LIB anode materials.

Keqiang Xu

Papers

Nitrogen-doped carbon dots decorated on g-C3N4/Ag3PO4 photocatalyst with improved visible light photocatalytic activity and mechanism insight

Nanocomposites Based on CoSe2-Decorated FeSe2 Nanoparticles Supported on Reduced Graphene Oxide as High-Performance Electrocatalysts toward Oxygen Evolution Reaction.

Nickel@Nitrogen-Doped Carbon@MoS2 Nanosheets: An Efficient Electrocatalyst for Hydrogen Evolution Reaction.

Cyanide-metal framework derived CoMoO4/Co3O4 hollow porous octahedrons as advanced anodes for high performance lithium ion batteries

Metal organic framework derived NiFe@N-doped graphene microtube composites for hydrogen evolution catalyst