Staggered interfacial pores in hollow ZIF-67@ZIF-8 enable efficient C3H6/C3H8 separation in MMMs

Membrane separation technology offers a promising energy-efficient alternative to the energy-intensive separation of alkenes from alkanes, yet existing membranes are generally constrained by low selectivity and high mass transfer resistance. To address this, we constructed hollow ZIF-67@ZIF-8 (H-ZIF-67@8) core-shell nanocages with staggered interfacial pores and sieve properties, and incorporated them into a polyimide to fabricate mixed matrix membranes (MMMs). Mechanistic investigations reveal that the hollow cavity of H-ZIF-67@8 significantly minimizes diffusion resistance and serves as a fast track for gas transport. In addition, the staggered interfacial pores induced by lattice mismatch at the H-ZIF-67@8 core-shell interface enable precise kinetic sieving of C 3 H 6 /C 3 H 8 . By synergistically intensifying the diffusion and sieving mechanisms, the optimized MMM with 20 wt% loading showed a C 3 H 6 permeability of 62.12 Barrer and a C 3 H 6 /C 3 H 8 selectivity of 33.52, thereby surpassing the 2003 Robeson upper bound. This work provides new insights for the molecular engineering design of next-generation high-performance gas separation membranes.