Issue 43, 2015

The addition of CO2 to four superbase ionic liquids: a DFT study

Abstract

The addition of carbon dioxide to four superbase ionic liquids, [P3333][Benzim], [P3333][124Triz], [P3333][123Triz] and [P3333][Bentriz] was studied using a molecular DFT approach involving anions alone and individual ion pairs. Intermolecular bonding within the individual ion pairs is characterised by a number of weak hydrogen bonds, with the superbase anion geometrically arranged so as to maximize interactions between the heterocyclic N atoms and the cation. The pairing energies show no correlation to the observed CO2 adsorption capacity. 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 the more weakly absorbing ion pairs which contain [123Triz] and [Bentriz], the carbamate-functionalised systems are very close in energy to adducts in which CO2 is more weakly bound, suggesting an equilibrium between the chemi- and physisorbed CO2.

Graphical abstract: The addition of CO2 to four superbase ionic liquids: a DFT study

Supplementary files

Article information

Article type
Paper
Submitted
28 Aug 2015
Accepted
25 Sep 2015
First published
25 Sep 2015
This article is Open Access
Creative Commons BY license

Phys. Chem. Chem. Phys., 2015,17, 28674-28682

Author version available

The addition of CO2 to four superbase ionic liquids: a DFT study

M. Mercy, S. F. Rebecca Taylor, J. Jacquemin, C. Hardacre, R. G. Bell and N. H. De Leeuw, Phys. Chem. Chem. Phys., 2015, 17, 28674 DOI: 10.1039/C5CP05153C

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