Volume 192, 2016

Mechanisms of CO2 capture in ionic liquids: a computational perspective

Abstract

We present computational studies of CO2 sorption 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 CO2 to 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.

Associated articles

Article information

Article type
Paper
Submitted
15 เม.ย. 2559
Accepted
03 พ.ค. 2559
First published
03 พ.ค. 2559

Faraday Discuss., 2016,192, 479-492

Mechanisms of CO2 capture in ionic liquids: a computational perspective

M. Mercy, N. H. de Leeuw and R. G. Bell, Faraday Discuss., 2016, 192, 479 DOI: 10.1039/C6FD00081A

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