Rational Matching of Metal–Organic Frameworks and Polymers in Mixed Matrix Membranes for Efficient Propylene/Propane Separation

The exploitation of high-performance membranes selective for propylene is important for developing energy-efficient propylene/propane (C₃H₆/C₃H₈) separation technologies. Although metal-organic frameworks with a molecular sieving property have been considered promising filler materials in mixed-matrix membranes (MMMs), their use in practical applications has been challenging due to a lack of interface compatibility. Herein, we adopted a surface coordination strategy that involved rationally utilizing carboxyl-functionalized PIM-1 (cPIM) and ZIF-8 to prepare a mixed-matrix membrane for efficient propylene/propane separation. The interfacial coordination between the polymer and the MOF improves their compatibility and eliminates the need for additional modification of the MOF, thereby maximizing the inherent screening performance of the MOF filler. Additionally, the utilization of porous PIM-1 guaranteed the high permeability of the MMMs. The obtained MMMs exhibited excellent separation performance. The 30 wt% ZIF-8/cPIM-1 membrane performed the best, exhibiting a high C₃H₆ permeability of 1023 Barrer with a moderate C₃H₆/C₃H₈ selectivity of 13.97 under 2 bars of pressure. This work presents a method that can feasibly be used for the preparation of defect-free MOF-based MMMs for specific gas separations.