Binary-filler engineering of ZIF-8 and mesoporous silica in PEBAX mixed-matrix membranes toward enhanced CO2 separation performance

Abstract

Mixed-matrix membranes (MMMs) incorporating porous fillers provide an effective strategy to overcome the permeability–selectivity trade-off in polymeric membranes for CO2 separation. In this study, a binary-filler system consisting of microporous ZIF-8 and mesoporous silica was introduced into a Pebax matrix to investigate their distinct and synergistic roles in regulating gas transport behavior and mechanical properties. Structural characterizations confirmed uniform filler dispersion and cooperative modulation of segmental packing without altering the intrinsic polymer framework. The incorporation of ZIF-8 enhanced CO2/N2 selectivity through preferential CO2 adsorption, while mesoporous silica introduced additional diffusion pathways that enhanced gas permeability. The silica loading was found to significantly influence both permeability and selectivity, and an optimal silica content of 0.25 wt% yielded a CO2 permeability of 136 Barrer with a CO2/N2 selectivity of 73.4, slightly exceeding the 2008 Robeson upper bound. These results demonstrate that binary-filler engineering provides an effective strategy for developing high-performance Pebax-based MMMs for carbon capture applications.