High-Performance Mixed-Matrix Membranes Using a Zeolite@MOF Core–Shell Structure Synthesized via Ion-Exchange-Induced Crystallization and Post-Synthetic Conversion

selectivity of 43.3, significantly surpassing the established upper limits for polymeric membranes. Our findings underscore the potential of core-shell structures composed of microporous materials for achieving the coveted properties necessary for high-performance gas separation membranes.