Highly permeable mixed matrix materials comprising ZIF-8 nanoparticles in rubbery amorphous poly(ethylene oxide) for CO₂ capture

Amorphous polymers containing poly(ethylene oxide) are leading membrane materials for CO₂ capture from fossil fuel-derived flue gas and syngas, such as those prepared from poly(ethylene glycol) diacrylate (PEGDA) and poly(ethylene glycol) methyl ether acrylate (PEGMEA). This work shows that introduction of zeolitic imidazolate framework-8 (ZIF-8) nanoparticles in these polymers increases CO₂ permeability with minimal effect on CO₂/H₂ and CO₂/N₂ selectivity. Specifically, ZIF-8 nanoparticles with a size of 150-250 nm were synthesized and fabricated into mixed matrix materials (MMMs). The effect of ZIF-8 loading on gas transport properties at 35 °C in MMMs was systematically investigated. Adding 10 wt% ZIF-8 in the crosslinked PEGDA increases CO₂ permeability from 130 Barrers to 320 Barrers unexpectedly by 170% without any reduction of CO₂/light gas selectivity. While the CO₂/light gas selectivity in the MMMs can be satisfactorily described using the Lewis-Nielsen model, the model underestimates the gas permeability. Despite a body of studies of MMMs comprising ZIFs, this work represents one of the few on the MMMs based on amorphous rubbery polymers elucidating the effect of ZIF-8 loading on the polymer properties and demonstrating their impact in achieving superior CO₂/H₂ and CO₂/N₂ separation properties.