Probing the Reorganization of Ionic Liquids' Structure Induced by CO 2 Sorption.

The sorption of CO ₂ is often used to modify the macroscopic properties of liquids and solids. In the particular case of ionic liquids, different from molecular liquids, the sorption of CO ₂ may not induce volume expansions due to the strong Coulombic interactions between the ions of the fluid. However, a considerable viscosity decrease has been systematically observed. In order to understand the mechanisms of properties modifications in ionic fluids, herein we used Raman spectroscopy to probe the effect of CO ₂ on the structure of ionic liquids. It is shown that CO ₂ perturbs the electrostatic interactions between cations and anions, thus inducing a change in the polar domain of ionic liquids. It is observed that ionic liquids having bulkier ions are more prone to be perturbed by CO ₂ in comparison to ionic liquids having smaller ions. These results reveal new means of controlling the electrostatic forces between the ions and contributes to the mechanistic understanding of the modification of the macroscopic properties of ionic liquids by CO ₂ sorption.
(© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)