Cd-MOF@PVDF Mixed-Matrix Membrane with Good Catalytic Activity and Recyclability for the Production of Benzimidazole and Amino Acid Derivatives
Yansong Jiang, Jing Sun, Xiaona Yang, Jieyu Shen, Yu Fu, Yong Fan, Jianing Xu, Li Wang
Abstract
Mixed-matrix membranes (MMMs) incorporating metal–organic framework crystalline fillers as heterogeneous catalysts for organic transformation reactions have attracted more attention in catalysis science. Herein, a new 3D cadmium metal–organic framework (H3O)·[Cd(dppa)] (1) was first synthesized using the rigid 4-(3,5-dicarboxylphenyl)picolinic acid (H3dppa) as an organic ligand under solvothermal conditions, exhibiting a novel 6,6-connected network and good tolerance to various solvents. After activation, 1 showed good catalytic reactivity and selectivity for the synthesis of benzimidazole derivatives, affording solvent-dependent catalytic activity. Then, using the microcrystals of 1 and poly(vinylidene fluoride) (PVDF) as raw materials, 1@PVDF MMMs were successfully prepared by polymer solution casting. Notably, the integration of MOF and PVDF endows the mixed-matrix membrane 1@PVDF with great advantages in terms of more dispersive Lewis acid catalytic sites and recyclability. As expected, 1@PVDF not only displays good catalytic activity comparable to that of activated 1 but also exhibits remarkable recyclability and continuous usability for the production of benzimidazole and α- or β-amino acid derivatives. To the best of our knowledge, this is the first time that a Cd-based MOF and MMMs have been applied as a catalyst for the production of a β-amino acid. The combination of catalytic MOF and PVDF provides a way to simplify the design of a flow reactor and reduce the costs of manufacturing.