Facile Defect Engineering of Zeolitic Imidazolate Frameworks towards Enhanced C₃H₆/C₃H₈ Separation Performance

Abstract Membrane‐based olefin/paraffin separations can be an attractive alternative to the current energy‐intensive cryogenic distillation for their high energy efficiency. This paper reports an amine modulator‐induced defect engineering of zeolitic imidazolate framework‐8 (AZIF8) nanoparticles (60 nm) for enhanced molecular sieving ability and good compatibility with various polymer matrices. It is revealed that an initial suppression of nuclei formation during synthesis enables amine modulators to deprotonate the neutral organic ligand as well as coordinate with Zn²⁺ ions. The resulting AZIF8s exhibit more rigid characteristics compared to the conventional ZIF‐8 counterparts as demonstrated by its delayed gate opening pressure. Molecular dynamics simulations also suggest that AZIF8s exhibit a narrower pore size distribution with a smaller opening compared to the conventional ZIF‐8 analogues, which makes them more suitable for size‐discrimination between C₃H₆ and C₃H₈. Furthermore, the coordination of alkyl amines into frameworks allows excellent compatibility with various commercial polymer matrices. The highly concentrated 6FDA‐DAM/AZIF8 (50/50 w/w) mixed matrix membrane (MMM) exhibits superior C₃H₆/C₃H₈ separation performance (C₃H₆ permeability of 79.38 Barrer and C₃H₆/C₃H₈ selectivity of 39.8 at single gas condition) to most existing MMMs. The structural engineering proposed herein can be applied to other metal–organic frameworks for optimizing their performance in molecular separations.