Copper nanoparticles were successfully prepared from metallic copper flakes using a facile synthetic method involving the ionic liquid, 1-butyl-3-methyl imidazolium nitrate (BMIM+1\105-). The formation of copper nanoparticles was verified using UV-Vis and transmission electron microscopy (TEM). Furthermore, this facile synthetic route allowed the in-situ fabrication of the facilitated CO2 transport membrane because the ionic liquid polarized and later, stabilized the surfaces of copper nanoparticles. It was expected that the CO2 molecules would interact with the positively charged copper nanoparticles and free imidazolium cations of the ionic liquid. The positive charges on the surfaces of the copper nanopartides and the interaction with the ionic liquid were verified using X-ray photoelectron spectroscopy (XPS) and Fourier transform (FT)-Raman, respectively. The BMIMINI0i/Cu nanoparticle membrane showed the ideal selectivities of 12.0 (CO2/N2) and 12.6 (CO2/CH4), while the CO2 permeance enhanced from 5.2 to 9.8 GPO. (C) 2014 Elsevier B.V. All rights reserved.