Preparation of [C2mim][BF4]@ZIF-8/Pebax mixed matrix membranes for enhanced CO2/N2 separation performance

Abstract

Mixed matrix membranes (MMMs) demonstrate promising separation capabilities for CO₂ capture, representing a key area of current research interest. Nonetheless, the propensity for inorganic nanoparticles to cluster can degrade the CO₂ separation efficiency. Addressing the challenge of nanomaterial aggregation within polymer matrices, this investigation employs a polyether-block-amide (Pebax), the ionic liquid (IL) 1-ethyl-3-methylimidazolium tetrafluoroborate ([C₂mim][BF₄]), and ZIF-8 to develop MMMs designed for CO₂ separation. The preparation of the IL@ZIF-8 composite involved the wet impregnation method, while the IL@ZIF-8/Pebax MMMs were created through the solution casting approach. Analysis confirms the successful encapsulation of IL within the ZIF-8 nanocage structures, which can adjust the size of ZIF-8's pores. Concurrently, the IL@ZIF-8 composite material exhibits excellent dispersion within Pebax, which is conducive to exposing a greater number of active sites. Furthermore, the porous architecture of IL@ZIF-8 further facilitates gas adsorption and diffusion, leading to enhanced gas separation efficiency. As the IL@ZIF-8 loading hits 6 wt%, the MMM maximizes CO₂ separation, offering a CO₂ permeability of 169 Barrer and a CO₂/N₂ selectivity of 80, going beyond the 2008 Robeson upper bound and showcasing excellent gas separation functionality. This offers novel approaches for the development of more accurate and effective MMMs.