ZIF@MOF core-shell functional structure synthesized via controlled ligand-exchange for enhanced CO2 separation in mixed matrix-membranes

Abstract

Mixed matrix membranes (MMMs) have attracted considerable attention for gas separation applications; however, their performance is often limited by poor polymer-filler compatibility and the inherent permeability-selectivity trade-off. Herein, we report a controlled ligand-exchange strategy for the synthesis of ZIF-67@Co-MOF-74 core-shell nanoparticles, designed to simultaneously enhance interfacial compatibility and gas separation performance in Pebax 1657 based MMMs. In this architecture, the Co-MOF-74 shell improves filler dispersion and polymer-filler interactions, while the ZIF-67 core provides high CO2 affinity and molecular-sieving capability. As a result, the incorporation of these core-shell fillers leads to an adsorption-dominated increase in CO2 permeability accompanied by a suppressed N2 transport, outperforming MMMs containing pristine ZIF-67 and many state-of-the-art Pebax-based MMMs. The optimal membrane containing 2 wt.% ZIF 67@Co-MOF-74 exhibits a CO2 permeability of 130 Barrer and a CO2/N2 selectivity of 117, exceeding the neat Pebax-1657 membrane by 49% and 72%, respectively, and surpassing the 2019 Robeson upper bound. In addition, the membrane demonstrates excellent long-term operational stability, highlighting the effectiveness of the ligand-exchange-derived core-shell filler design as a promising strategy for advanced CO2 separation membranes.