Mixed matrix membrane comprising glycine grafted CuBTC for enhanced CO2 separation performances with excellent stability under humid atmosphere

Benefitting from its remarkable adsorption selectivity, CuBTC has been a prospective filler for mixed matrix membranes (MMMs). However, CuBTC is unstable in humid atmosphere, which hinders its further applications. In this work, CuBTC and glycine grafted CuBTC (named Gly@CuBTC) particles were synthesized and embedded into Pebax MH 1657 to form the corresponding MMMs. CuBTC was grafted with glycine molecules to simultaneously enhance its moisture stability and CO2 adsorption capacity. It could be found that Gly@CuBTC exhibited higher CO2 adsorption capacity than pristine CuBTC. Besides, based on characterization by using SEM, XRD, FT-IR and nanomechanical tests, the as-prepared Pebax/Gly@CuBTC MMMs possessed improved interfacial compatibilities and mechanical strengths. Moreover, the CO2/CH4 separation performance of the MMMs were studied at different filler loadings and feeding pressures. With the addition of 5 wt% Gly@CuBTC, the resultant MMM exhibited the best performance with CO2 permeability of 175 Barrer and CO2/CH4 selectivity of 29. Better yet, Pebax/Gly@CuBTC MMMs showed excellent stability against moisture. This work demonstrated that Gly@CuBTC could be a promising filling material to develop industrial MMMs for separation and purification of natural gas.