Graphene nanoplatelets based polyimide/Pebax dual-layer mixed matrix hollow fiber membranes for CO2/CH4 and He/N2 separations

•GNPs based PI/Pebax dual-layer MMMs for gas separations were prepared and studied.•NMP solvent was partially replaced by the green GBL during the membranes’ formation.•Ternary phase diagram was plotted for P84/solvent (NMP/GBL & GBL)/water systems.•A real selectivity of 82 for CO2/CH4 was achieved, which is among the highest.•High separation factors was also achieved for He/N2 and other gas mixtures.