The gas transport properties of MMM measured using single gas permeation set up (N2, O2, CO2, and CH4) at ambient temperature and different feed pressures. Additionally, sorption isotherms for mixed matrix membranes made for CH4 and CO2. The sorption data were analyzed by the dual-mode sorption model. The morphological studies show that the incorporation of CNFs appreciably changed the surface properties of membranes. The permeation test showed that the mixed matrix membrane exhibited high permeability. With increasing CNF concentration, CNFs/PSF membrane permeability raised from 2.134 to 12.04 Barrer for CO2. The results found that this unique membrane had increased permeability and enhanced selectivity. Also it has a great potential to be used practically in gas separation technology.