The CO2/CH4 and CO2/H-2 permselectivity of poly(vinylbenzyltrimethylammonium fluoride), PVBTAF polyelectrolyte membranes can be significantly improved by blending in certain fluoride-containing organic and inorganic salts. For example, the CO2 permeance of a PVBTAF-4CsF (4 mel CsF/mol repeat unit) composite membrane was more than four times that of a simple PVBTAF composite membrane while CO2/CH4 and CO2/H-2 selectivities were comparable. Surprisingly, the blends are at least macroscopically homogeneous even with as much a 6 mel salt/mol PVBTAF repeat unit. The optimal salt loading appears to be approximately 4 mol CsF/mol polyelectrolyte repeat unit. Membrane performance is strongly dependent on the relative humidity of the gas streams and is maximized in the range of 30-50% relative humidity. Membranes containing choline fluoride exhibited improved membrane performance at relative humidities below 30%. Permselective data suggests that CO2 transport is kinetically limited in 10 mu m thick films. The blends are stable in CO2/CH4/H-2 streams for more than 30 days of continuous operation, however, the membranes suffer an irreversible degradation due to reaction with trace level sulfur-containing contaminants common to cylinder H2S.