Nanoarchitectured Design of Porous Materials and Nanocomposites from Metal‐Organic Frameworks

The emergence of metal‐organic frameworks (MOFs) as a new class of crystalline porous materials is attracting considerable attention in many fields such as catalysis, energy storage and conversion, sensors, and environmental remediation due to their controllable composition, structure and pore size. MOFs are versatile precursors for the preparation of various forms of nanomaterials as well as new multifunctional nanocomposites/hybrids, which exhibit superior functional properties compared to the individual components assembling the composites. This review provides an overview of recent developments achieved in the fabrication of porous MOF‐derived nanostructures including carbons, metal oxides, metal chalcogenides (metal sulfides and selenides), metal carbides, metal phosphides and their composites. Finally, the challenges and future trends and prospects associated with the development of MOF‐derived nanomaterials are also examined.     

Facile Synthesis of Vanadium Metal‐Organic Frameworks for High‐Performance Supercapacitors

Compared to traditional metal oxides, metal‐organic frameworks exhibit excellent properties, such as a high surface area, significant thermal stability, low density, and excellent electrochemical performance. Here, a simple process is proposed for the fabrication of rod‐like vanadium metal‐organic frameworks (V^IV(O)(bdc), bdc = 1,4‐benzenedicarboxylate, or MIL‐47), and the effect of the structure on the electrochemical performance is investigated via a series of electrochemical measurements. The V^IV(O)(bdc) electrode exhibits a maximum specific capacitance of 572.1 F g^?1 at current densities of 0.5 A g^?1. More significantly, aqueous and solid‐state asymmetric supercapacitors are successfully assembled. The solid‐state device shows an excellent energy density of 6.72 mWh cm^?3 at a power density of 70.35 mW cm^?3. This superior performance confirms that V^IV(O)(bdc) electrodes are promising materials for applications in supercapacitors.     

Metal‐Organic Frameworks for CO2 Chemical Transformations

Carbon dioxide (CO₂), as the primary greenhouse gas in the atmosphere, triggers a series of environmental and energy related problems in the world. Therefore, there is an urgent need to develop multiple methods to capture and convert CO₂ into useful chemical products, which can significantly improve the environment and promote sustainable development. Over the past several decades, metal‐organic frameworks (MOFs) have shown outstanding heterogeneous catalytic activity due in part to their high internal surface area and chemical functionalities. These properties and the ability to synthesize MOF platforms allow experiments to test structure‐function relationships for transforming CO₂ into useful chemicals. Herein, recent developments are highlighted for MOFs participating as catalysts for the chemical fixation and photochemical reduction of CO₂. Finally, opportunities and challenges facing MOF catalysts are discussed in this ongoing research area.     

Porous Organic Frameworks Featured by Distinct Confining Fields for the Selective Hydrogenation of Biomass-Derived Ketones

The asymmetric hydrogenation of biomass-derived molecules for the preparation of single enantiomer compounds is an effective method to reduce the rapid consumption of fossil resources. Porous organic frameworks (POFs) with pure organic surfaces may provide unusual confinement effects for organic substrates in chiral catalysis. Here, a series of POF catalysts are designed with chiral active centers decorated into sharply defined one-dimensional channels with diameters in the range of 1.2–2.9 nm. Due to the synergistic effect originating from the conjugated inner wall, the POF material (aperture size 2.4 nm) concentrates over 90% of aromatic species into the porous architecture, and its affinity is one or two orders of magnitude higher than those of classical porous solids. As determined by PBE+D3 calculation, the phenyl fragment reveals strong π–π interaction for steric hindrance around the metal active site to achieve stronger asymmetric induction. Therefore, this POF catalyst achieves high conversion (>99% yield) and enantioselectivity (>99% ee) for various substrates. The advantages of using the POF platform as a chiral catalyst can provide new perspectives on POF-based solid-state host–guest chemistry and asymmetric heterogeneous catalysis.     

Thermally Stable Metal‐Organic Framework‐Templated Synthesis of Hierarchically Porous Metal Sulfides: Enhanced Photocatalytic Hydrogen Production

Porous nanostructured materials are demonstrated to be very promising in catalysis due to their well accessible active sites. Thermally stable metal‐organic frameworks (MOFs) as hard templates are successfully utilized to afford porous metal oxides and subsequently metal sulfides by a nanocasting method. The resultant metal oxides/sulfides show considerable Brunauer–Emmett–Teller (BET) surface areas, by partially inheriting the pore character of MOF templates. Preliminary investigation on the obtained hierarchically porous CdS for water splitting, as a proof of concept, demonstrates its much higher activity than both corresponding bulk and nanosized counterparts, under visible light irradiation. Given the structural diversity and tailorability of MOFs, such synthetic approach may open an avenue to the synthesis of advanced porous materials for functional applications.     

Bimetallic Metal‐Organic Frameworks: Probing the Lewis Acid Site for CO2 Conversion

A highly porous metal‐organic framework (MOF) incorporating two kinds of second building units (SBUs), i.e., dimeric paddlewheel (Zn₂(COO)₄) and tetrameric (Zn₄(O)(CO₂)₆), is successfully assembled by the reaction of a tricarboxylate ligand with Zn^II ion. Subsequently, single‐crystal‐to‐single‐crystal metal cation exchange using the constructed MOF is investigated, and the results show that Cu^II and Co^II ions can selectively be introduced into the MOF without compromising the crystallinity of the pristine framework. This metal cation‐exchangeable MOF provides a useful platform for studying the metal effect on both gas adsorption and catalytic activity of the resulted MOFs. While the gas adsorption experiments reveal that Cu^II and Co^II exchanged samples exhibit comparable CO₂ adsorption capability to the pristine Zn^II‐based MOF under the same conditions, catalytic investigations for the cycloaddition reaction of CO₂ with epoxides into related carbonates demonstrate that Zn^II‐based MOF affords the highest catalytic activity as compared with Cu^II and Co^II exchanged ones. Molecular dynamic simulations are carried out to further confirm the catalytic performance of these constructed MOFs on chemical fixation of CO₂ to carbonates. This research sheds light on how metal exchange can influence intrinsic properties of MOFs.