Large-Scale Production of Hierarchically Porous Metal–Organic Frameworks by a Reflux-Assisted Post-Synthetic Ligand Substitution Strategy

Abstract

The mass production of hierarchically porous metal–organic frameworks (HP-MOFs) with adjustable morphology and size as well as retained crystallinity is highly desirable yet challenging. Herein, we have developed a versatile post-synthetic ligand substitution (PSLS) strategy to convert typical microporous MOFs and even their composites to HP-MOFs and their composites at a 10 g level and beyond in a simple reflux system. The resulting HP-MOFs feature intrinsic micropores and abundant defective mesopores, which greatly facilitate the transport and activation of large substrates for stable and efficient heterogeneous catalysis. Furthermore, the presence of defective mesopores in the HP-MOF composites improves activity and selectivity for large molecule-involved one-pot tandem catalysis. This strategy opens a new door to fast, facile, general, and scale-up production of HP-MOFs and related composites for expanding applications of conventional microporous MOF-based materials.

Ligand Defect Density Regulation in Metal–Organic Frameworks by Functional Group Engineering on Linkers

“…As the previous works suggested that the catalytic performance is positively correlated with the number of unsaturated metal sites, − we hypothesize that Ce-UiO-66-F with the highest ligand defect density possesses the best catalytic activity. As expected, among four Ce-UiO-66-X samples, Ce-UiO-66-F presents the highest catalytic yield (96%) toward cycloaddition reaction of CO 2 with glycidol under identical conditions, whereas Ce-UiO-66-OMe with the lowest defect density shows the lowest activity (54% yield), as shown in Figure a.…”

Bifunctional {Pb10K2}–Organic Framework for High Catalytic Activity in Cycloaddition of CO2 with Epoxides and Knoevenagel Condensation

“…In addition, the excessive emission of carbon dioxide (CO 2 ) has led to a series of serious ecological problems such as global warming and ocean level rising, which make the technology of CO 2 capture and utilization (CCU) widely concerned. − At present, the technical means of using CO 2 to synthesize valuable chemicals can not only effectively reduce the CO 2 content in the environment but also bring huge economic benefits to mankind, which has gradually become one of the most favorable strategies. , So far, it is found that the synthetic technology of cyclic carbonates from CO 2 and epoxides is one of the most effective ways, which can realize the dual functions of solving environmental problems and resource utilization, as cyclic carbonates are a kind of widely used chemicals and chemical raw materials. − However, at present, the catalysts used for producing cyclic carbonates in the industry are mainly organic and inorganic halogenated salts, which have many disadvantages, such as strong pollution, low catalytic efficiency, and difficult separation. − However, the synergistic effect of the exposed metal cations (Lewis acids) and the basic groups (Lewis bases) in microporous MOFs leads to the excellent catalytic activity in the cycloaddition reaction of CO 2 with epoxides. − Furthermore, to enhance the selectivity and catalytic activity, the confined pore environments of MOFs can be adjusted using carefully designed structure-oriented ligands and adjusting the growth environments. , Among all reported MOFs, PbOFs account for a small proportion and are usually based on the most common SBUs, such as monomeric [Pb­(CO 2 ) n ]. , However, the excellent catalytic ability derived from the high-level p-orbitals of the Pb 2+ ion gives scientists impetus to explore more perfect lead–organic frameworks.…”

Fluorine-Functionalized NbO-Type {Cu2}-Organic Framework: Enhanced Catalytic Performance on the Cycloaddition Reaction of CO2 with Epoxides and Deacetalization-Knoevenagel Condensation

“…However, it is still a tremendous challenge for accurately designing and controlling the microstructure of MOF materials, by which the density of active sites and the intrinsic activity of active sites can be hoisted. Recent studies have proved that high catalytic activity of MOF materials can be achieved by modifying the ligands of MOF materials with functional groups. − In recent years, the introduction of Lewis basic sites such as −NH 2 and −CH 3 onto the nanochannel of MOFs has aroused widespread concern, by which the synergistic catalysis of acid–base sites to further improve their catalytic activity can be realized. − So far, Lewis basic functional groups, such as hydroxyl, amino, carboxyl, imidazole, and pyridine, have been successfully applied to functionalize the channels of MOFs, which, as expected, exhibit superior performance for the adsorption of CO 2 , selective and efficient catalysis for specific organic reactions, and the capture of toxic war gas.…”