Enhancing the gas separation properties of mixed matrix membranes via impregnation of sieve phases with metal and nonmetal promoters

•Impregnation of sieves is a possible approach to achieve more efficient MMMs.•Mesoporous ZSM-5 nanoparticles were impregnated by metal/nonmetal promoters.•Ideal MMMs were prepared using the impregnated ZSM-5 nanoparticles.•Impregnation enhanced gas permeation rates ascribed to dealumination phenomenon.•Impregnation by transition metals (Mn and Fe) improved CO2 removal efficiency. In recent years, numerous studies investigated influence of many different sieves on gas separation performance of mixed matrix membranes (MMMs), but few studies have investigated effects of morphology of sieve phases. Herein, we used two transition metal oxides, based on manganese (Mn) and iron (Fe), and also a nonmetal oxide, based on phosphorus (P), as modifier agents in impregnation process of ZSM-5 nanoparticles. These metal/nonmetal oxides are briefly named promoters. Influence of the impregnated ZSM-5 nanoparticles on separation performance of PEBA/ZSM-5 MMMs were investigated, [PEBA: polyether block amide]. Morphological changes made during the impregnation process considerably affected the gas separation properties of the MMMs. ZSM-5 nanoparticles impregnated with Mn, Mn-ZSM5, showed a separation performance beyond that of the parent ZSM-5 nanoparticles. Compared to the parent, Mn-ZSM-5 at the highest loading content, 9 wt%, increased the CO2 permeability by 44%, while CO2/CH4 and CO2/N2 selectivity values respectively enhanced from 22.7 and 48.8 to 33.3 and 52.2. Our results confirmed that impregnation of sieve phases with metal promoters can be considered as a reliable approach to provide a general toolbox for improving the gas separation performance of membranes bearing molecular sieve phases.