(697b) Highly Propylene-Selective Mixed-Matrix Membranes By in-Situ MOF Formation Using a Polymer-Modification Strategy

Despite the potentials of C₃H₆/C₃H₈ separation, there have been no industrial applications of ZIF-8 mixed-matrix membranes (MMMs) due to the moderate separation performances and several challenging processing issues. Herein, we present a new paradigm of MMM fabrication, named polymer-modification-enabled in-situ metal-organic framework formation (PMMOF), enabling in-situ formation of ZIF-8 nanocrystals inside 6FDA-DAM polymer. PMMOF consists of four steps including hydrolysis of polymer, ion-exchange, ligand treatment, and imidization. Each step was thoroughly analyzed and important processing parameters were identified, enabling the structural control of MMMs by PMMOF. The binary C₃H₆/C₃H₈ separation performance of the MMMs showed much higher separation factors than conventionally-prepared MMMs at similar filler loadings, satisfying the commercial C₃H₆/C₃H₈ separation performance criteria. PMMOF was successfully applied for other MOFs, demonstrating the process could be general. Finally, as a proof-of-concept, asymmetric mixed-matrix hollow fiber membranes with ultrathin selective skin layers were prepared by PMMOF, showing promising C₃H₆/C₃H₈ separation performances.