Understanding the High Solubility of CO2 in an Ionic Liquid with the Tetracyanoborate Anion

Journal Article · Sat Jan 01 04:00:00 EST 2011 · Journal of Physical Chemistry B

DOI:https://doi.org/10.1021/jp205399r· OSTI ID:1024701

Babarao, Ravichandar ^[1]; Dai, Sheng ^[1]; Jiang, Deen ^[1]

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1. 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 Laboratory (ORNL)
• Sponsoring Organization: SC USDOE - Office of Science (SC)
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 1024701
• Journal Information: Journal of Physical Chemistry B, Journal Name: Journal of Physical Chemistry B Journal Issue: 32 Vol. 115; ISSN 1520-6106
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ANIONS
CATIONS
MOLTEN SALTS
SIMULATION
SOLUBILITY
SPATIAL DISTRIBUTION