The fabrication and permselective properties of polyelectrolyte and polyelectrolyte-salt blend membranes and their utility for acid gas separations have been described. Such membranes permeate acid gases by a facilitated transport mechanism and, in addition, act largely as barriers to the permeation of non-acidic gases. Fabrication of defect free polyelectrolyte membranes is difficult and even a relatively low defect rate can result in a substantial decrease in selectivity. A technique to repair polyelectrolyte membranes is described that surprisingly results in both improved CO2 permeances and selectivities. The technique involves casting an additional polyelectrolyte layer upon a precast polyelectrolyte membrane. Membranes consisting of a layer of poly(vinylbenzyltrimethylammonium fluoride) (PVBTAF) cast upon poly(diallyldimethylammonium fluoride) (PDADMAF) exhibited CO2/H-2 selectivities and CO2 permeances, which were 2-18 and 1.3-2.3 times greater, respectively, than for those consisting of a single layer of PDADMAF This is surprising since defect repair is expected to improve selectivity but not permeance. Although the cause of the unexpectedly high CO2 permeances remains unknown, it is perhaps related to a mutual dissolution of the two polyelectrolytes at their interface.