The surface of polysulfone membranes has been modified using the fluorine chemicals, PFPA (pentafluoropropionic anhydride F.W.=310.05) and TFI (Trideca-fluoro-8-idoctane, F.W.=474.0), based on Friedel-Crafts reaction mechanism with varying reaction temperatures, reaction time, and catalysis types. The resulting membranes were characterized through the analysis of ESCA, contact angle measurement and pure water permeability. And the modified PS membranes were exposed to gases of O-2, N-2, and CO2 to measure the permeation rates and ideal separation factors. In addition, the diffusivities and solubilities of individual gases were measured.