title: Mechanisms of CO2capture in ionic liquids: a computational perspective.
abstract: We present computational studies of CO2sorption in two different classes of ionic liquid. The addition of carbon dioxide to four superbase ionic liquids, [P3333][Benzim], [P3333][124Triz], [P3333][123Triz] and [P3333][Bentriz], was studied using the DFT approach and considering anions alone and individual ion pairs. The addition of CO2to the anion alone clearly resulted in the formation of a covalently-bound carbamate function with the strength of binding correlated to experimental capacity. In the ion pair however the cation significantly alters the nature of the bonding such that the overall cohesive energy is reduced. Formation of a strong carbamate function occurs at the expense of weakening the interaction between anion and cation. In [N1111][l-ALA], a representative amino acid ionic liquid, evidence was found for a low-energy monomolecular mechanism for carbamate formation, explaining the 1 : 1 molar uptake ratio observed in some amino acid ionic liquids. The mechanism involves proton transfer to the carboxylate group of the aminate anion.
authors.affiliation: Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK. r.g.bell@ucl.ac.uk.
authors.forename: Maxime
authors.initials: M
authors.lastname: Mercy
authors.affiliation: Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK. r.g.bell@ucl.ac.uk and School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, UK. deleeuwn@cardiff.ac.uk.
authors.forename: Nora H
authors.initials: NH
authors.lastname: de Leeuw
authors.affiliation: Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK. r.g.bell@ucl.ac.uk.
authors.forename: Robert G
authors.initials: RG
authors.lastname: Bell