Highly propylene-selective asymmetric mixed-matrix membranes by polymer phase-inversion in sync with in-situ ZIF-8 formation

Although mixed-matrix membranes (MMMs) have been extensively studied, their commercial applications have been hampered by scientific and engineering challenges. Herein, we report an innovative one-step MMM fabrication method that can put the commercialization of MMMs forward by overcoming most of the current challenges because it enables the rapid formation of high-performance asymmetric MMMs in a scalable manner. The method termed phase-inversion in sync with metal–organic framework (MOF) formation (PIMOF) involves a polymer film undergoing phase inversion and simultaneously ZIF-8 nanoparticles forming in-situ inside the polymer. The resulting MMMs show unexpectedly high C₃H₆/C₃H₈ separation performances (C₃H₆ permeance of ca. 7.5 GPU and C₃H₆/C₃H₈ separation factor of ca. 107), which is attributed mostly to the high effective ZIF-8 loading (>50 wt%) and the enhanced molecular sieving effect of the unusually small sub-5 nm ZIF-8 filler nanoparticles by restricted linker motion.