A novel polysulfone (PSF) mixed matrix membrane blended by polyethylene glycol (5 and 10 wt.%) was synthesized in which the graphene hydroxyl (G-OH) nanoparticles incorporated. Polyethelene glycol (PEG) as an affordable additive provides a proper CO2 affinity. Moreover, the G-OH nanoparticles was enhanced the CO2 permeability in MMMs through Lewis acid- base interaction between electron withdrawing oxygen of -OH and CO2. First, PSF membrane was modified via adding PEG. Obtained results were shown that the CO2 permeability increased significantly from 15.9 Barrer (for neat PSF) to 28.2 Barrer (for PSF/PEG (10 wt%), while a fairly significant increase in CO2/CH4 selectivity (from 12.23 forneat PSF to 12.81 for PSF/PEG (10 wt%) at the pressure of 2 bar and temperature of 35 degrees C. Second, the G-OH nanoparticles were incorporated (1, 2, 3, 4 and 5 wt%) into the both PSF/PEG (5 wt%) and PSF/PEG(10 wt%) matrix to prepare the PSF/PEG/G-OH MMMs. Results showed the best CO2/CH4 selectivity was obtained at 5 wt% loading of G-OH for both PSF/PEG (5 wt%) and PSF/PEG (10 wt%) were 20.94 and 22.39, respectively; at pressure of 8 bar. The separation properties of membranes were also evaluated at higherfeed pressure and the obtained results were discussed. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.