In this study, we showed for the first time that polymer electrolyte membranes consisting of tetrafluoroboric acid solution (HBF4) and poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) could be utilized for CO2 separation. We utilized tetrafluoroboric acid solution to increase the solubility of CO2 in PVDF-HFP membranes. Strong acidic HBF4 could be easily solvated by water molecules and then well distributed in PVDF-HFP chain. The hydrated protons generated by HBF4 in polymer chains could be selective channels for CO2 transport, resulting in high separation performance. The interaction between fluorine in PVDF-HFP and proton ions in HBF4 was investigated by FT-IR and Raman spectroscopy. Thermal gravimetric analysis (TGA) data demonstrated thermal stability of the membrane after the addition of HBF4 and formation of hydrated proton ions. The hydrated proton ions significantly increased the solubility of CO2 gas, resulting in both high selectivity and high gas permeance for CO2 (CO2/N-2 = 25 and 25 gas permeance unit (GPU), respectively). (C) 2016 Elsevier B.V. All rights reserved.