The effect of Ag2O nanoparticles on long-term stable poly(vinylpyrrolidone) (PVP)/AgBF4/Al(NO3)(3) complex membrane was investigated for olefin/paraffin separation. Even though PVP/AgBF4/Al(NO3)(3) complex membrane showed the long-term stability by effect of Al(NO3)(3), the relatively low separation performance was observed, especially mixed-gas permeance. Thus, Ag2O nanoparticles were incorporated into PVP/AgBF4/Al(NO3)(3) complex membrane for the enhanced separation performance. When PVP/AgBF4/Al(NO3)(3)/Ag2O nanoparticles composite membrane was prepared, they showed substantially enhanced performance for separation of the propane/propylene gas mixture, with a selectivity of 21.7 and permeance of 4.3 GPU while PVP/AgBF4/Al(NO3)(3) membrane showed 1.3 GPU with a selectivity of 15.0. FT-IR, TGA, and Raman analyses demonstrated that the enhanced separation performance induced by Ag2O nanoparticles was mainly related to two factors: (1) silver(I) oxide functioned as barrier for propane and (2) the interaction of the Ag ion and the oxygen of Ag2O could enhance the activity of Ag ions as olefin carriers. (C) 2017 Elsevier B.V. All rights reserved.