We report the effect of graphene oxide (GO) on a facilitated CO2 transport membrane consisting of copper nanoparticles (CuNP) prepared in situ in ionic liquids (IL), such as 1-hexyl-3-methylimidazolium nitrate (HmimNO(3)) and 1-methyl-3-octylimidazolium tetrafluoroborate (MoimBF(4)). The highly smooth surface of the GO was characterized by atomic force microscopy, and the interactions between the GO and the IL were investigated by Fourier transform-Raman spectroscopy. With GO, the fabricated HmimNO(3)/CuNP/GO and MoimBF(4)/CuNP/GO composite membranes showed CO2/N-2 separations of 8.7 and 30.7, respectively, with enhanced CO2 gas permeance compared to IL/CuNP composite membrane without GO. This implies that graphene oxide can be used as an effective additive in nanocomposite membranes for enhanced CO2 permeance. (C) 2014 Elsevier B.V. All rights reserved.