CO2-driven surface reconstruction in quaternary ammonium ionic liquid-propanol solutions

Abstract

X-ray reflectivity (XRR) examined surface structures of hydrophobic quaternary ammonium ionic liquids, and their propanol mixtures were examined by XRR. The quaternary ammonium cations were [N(n)111]+ (n = 3, 4, and 6) and an anion was commonly bis(trifluoromethanesulfonyl)imide, [TFSI]−. The surface tension of pure [N(n)111][TFSI] increased with increasing n. Pure [N(n)111][TFSI] surface structures were stable in all gas atmospheres. The XRR of [N3111][TFSI]-1-propanol equilibrated showed CO2-induced surface roughness. Time-resolved XRR under CO2 of [N(n)111][TFSI]-propanol provided surface instabilities and a reconstruction process. The addition of 2-propanol to CO2 in [N4111][TFSI] promoted specific surface layering and a large amount of CO2 capture.