Vibrational Spectroscopy of CO2 in 1-Ethyl-3-Methylimidazolium Ethyl Sulfate Ionic Liquid: A Quantum Chemical Approach

Abstract

Nowadays, global climate change is a noticeable and challenging environmental issue for the mankind. The expected cause of climate change is mostly the greenhouse gas emission. The possible ways to reduce these emissions may be through carbon capture and its storage. In this scenario, ionic liquids (ILs) have the potential to absorb the CO2 and thus have been investigated to a larger extent. Here, the solubility of CO2 was investigated using 1-ethyl-3-methylimidazolium ethyl sulfate (C2mim EtSO4) ILs. To do so, the quantum chemical calculations based on DFT in the gas phase were performed at wB97XD/6-311++G(d,p) level of theory, where dispersion effect is considered to obtain information at the molecular level on the certain parameters related to efficient CO2 capture by ILs. During the interaction of C2mim EtSO4 and CO2, it was found that the CO2 considerably interacts at C2-position and ethyl chain of the cation at the cost of the weakening of the cation–anion interactions. Results were also analyzed and consistent with the vibrational mode analysis. TD-DFT calculations were performed to obtain the frontier molecular orbitals (FMOs) for analyzing the charge transfer in the ion pair having the CO2 molecule.