Understanding the High Solubility of CO2 in an Ionic Liquid with the Tetracyanoborate Anion
- ORNL
The ionic liquid 1-ethyl-3-methylimidazolium tetracyanoborate, [emim][B(CN){sub 4}], shows greater CO{sub 2} solubility than several popular ionic liquids (ILs) of different anions including [emim]bis(trifluoromethylsulfonyl)imide [emim][Tf{sub 2}N]. Herein, both classical molecular dynamics simulation and quantum mechanical calculations were used to understand the high solubility of CO{sub 2} in the [emim][B(CN){sub 4}] IL. We found that the solubility is dictated by the cation-anion interaction, while the CO{sub 2}-anion interaction plays a secondary role. The atom-atom radial distribution functions (RDFs) between cation and anion show weaker interaction in [emim][B(CN){sub 4}] than in [emim][Tf{sub 2}N]. A good correlation is observed between gas-phase cation-anion interaction energy with CO{sub 2} solubility at 1 bar and 298 K, suggesting that weaker cation-anion interaction leads to higher CO{sub 2} solubility. MD simulation of CO{sub 2} in the ILs showed that CO{sub 2} is closer to the anion than to the cation and that it interacts more strongly with [B(CN){sub 4}] than with [Tf{sub 2}N]. Moreover, a higher volume expansion is observed in [emim][B(CN){sub 4}] than in [emim][Tf{sub 2}N] at different mole fractions of CO{sub 2}. These results indicate that [B(CN){sub 4}] as a small and highly symmetric anion is unique in giving a high CO{sub 2} solubility by interacting weakly with the cation and thus allowing easy creation of cavity for close contact with CO{sub 2}.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- DE-AC05-00OR22725
- OSTI ID:
- 1024701
- Journal Information:
- Journal of Physical Chemistry B, Vol. 115, Issue 32; ISSN 1520--6106
- Country of Publication:
- United States
- Language:
- English
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