Mechanochemical processing of interface-integrated mixed-matrix membranes for efficient gas separations

Abstract

Mixed-matrix membranes (MMMs), those hybridized by nanoporous fillers and polymers, hold great potential for energy-saving separations and offer ideal platforms to address permeability-selectivity trade-off, scale-up, and aging issues that plague polymer membranes or pure nanoporous membranes. However, achieving truly interphase integration to design high-performance MMMs remains extremely challenging. In this study, mechanochemistry is employed to construct interface-integrated MMMs based on metal-organic frameworks and polymers of intrinsic microporosity-1 for efficient gas separations. Characterizations and molecular dynamics simulation demonstrate that mechanochemical processing via facile, scalable, and versatile ball milling can disrupt crystalline periodicity of filler surfaces to form disordered interfaces and promote polymer-in-filler insertion and filler-matrix integration, thereby substantially enhancing filler dispersity, interfacial compatibility, separation performance, and antiaging property of MMMs. After natural aging for 220 days and humidity/temperature-swing operations, the CO2 and CH4 permeability and CO2/N2 and CH4/N2 selectivity of the interface-integrated MMMs are still achieved up to 18400 and 1500 Barrer and 32.1 and 4.0, respectively, which easily outclass the least performance upper bounds. It can be envisaged that this concept reported here provides an alternative route to achieve the desired property and maximize the separation performance of MMMs.