Ionic liquids (ILs) are promising in the capture and separation of CO2. In this work, IL 1-n-butyl-3-methylimidazolium heptafluorobutyrate, [C(4)mim][CF3CF2CF2COO], has been synthesized and characterized by H-1, C-13 and F-19 NMR spectra. Solubilities of CO2, H-2, N-2 and O-2 in this IL have been determined at the temperature range from (303.15 to 333.15) K and the pressure up to 8.9 MPa. From these data, the Henry's constant, the standard state solution Gibbs energy, standard state solution enthalpy and standard state solution entropy of these gases in [C(4)mim][CF3CF2CF2COO] were derived and analyzed from molecular interactions. It was shown that the solubility of CO2 is obviously higher than that in [C(4)mim] [CF3COO] and [C(4)mim][CF3SO3] reported in literature, which makes this IL an attractive solvent for gas separation processes. Furthermore, these solubility data were well correlated by Pitzer model. (C) 2012 Elsevier Ltd. All rights reserved.