Reconstruction of mixed matrix membranes by in situ vapor aminolysis for CO2/N2 and CH4/N2 separations

Abstract

Membrane technology has great potential for gas separation. Incorporation of nanoporous fillers in polymers is attractive for constructing high-performance mixed matrix membranes (MMMs). However, for some mixtures, especially those molecules with similar properties, efficient membrane separation remains extremely challenging. In this study, we report post-synthetic reconstruction of MMMs by in situ aminolysis via chemical vapor deposition for enhancing gas separation performance. By utilization of amine substitution to functional groups of polymers of intrinsic microporosity and chelation to metal centers of metal-organic frameworks (MOFs), the MMMs are modified under mild conditions. Since aminolysis promotes amino grafting, boosts preferential sorption, regulates pathway, and enhances filler-polymer adhesion, the MMMs have substantially improved antiaging property and CO2/N2 separation performance, with permeability of 6986 Barrer and selectivity of 30.7. Importantly, for CH4/N2 mixture separation, that is critical for natural gas purification but difficult to separate, the MMMs also exhibit competitive selectivity and permeability of 5.0 and 897 Barrer, respectively. The performances for CO2/N2 and CH4/N2 separations can be close to and surpass the least trade-off upper bounds, respectively. Moreover, in situ aminolysis by vapor deposition has universal applicability for reconstructing various MMMs. This strategy is an alternative route to fabricate membranes for efficient separations.