Selective absorption of CO 2 from H 2 , O 2 and N 2 by 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate Liu, X.; He, M.; Lv, N.; Xu, H.; Bai, L.; The Journal of Chemical Thermodynamics 2016, 97, 48-54