Catalytic membrane micro-reactor with nano Cu/ZIF-8 assembly in membrane pores by flowing synthesis combining partial ion-exchange

A catalytic membrane micro-reactor (CMMR) is fabricated, with nano Cu/ZIF-8 particles immobilized in the pores of the microfiltration membrane for flow-through catalysis. Nano ZIF-8 is firstly assembled in polyethersulfone (PES) membrane pores by flowing synthesis and then Cu nanoparticles (NPs) are synthesized in-situ in ZIF-8 by the partial ion-exchange reaction. Cu/ZIF-8 nanoparticles are distributed evenly throughout the whole direction of membrane thickness while Cu NPs are dispersed well in ZIF-8. The 4-nitrophenol (4-NP) reduction is used to test the performance of the CMMR. The 4-NP reduction rate being 99.3% is achieved when the membrane flux is 2293 L m−2 h−1. The CMMR has good stability for over 210 min and presents a surprisingly high apparent reaction rate constant (Kapp, 837.43 min−1) at room temperature with the loading of ZIF-8 being 85 mg g−1 (PES) and Cu loading cycle number being 1. Compared with batch catalysis by powder catalysts, the Kapp is increased by 4 orders of magnitude via flow-through catalysis mode using CMMR. The nanoscale configuration of ZIF-8 and Cu NPs assembled inside pores of the membrane enhances remarkably the catalytic activity owing to the enhanced contact and mass transfer in the confined space of membrane pores.