Probing the Reorganization of Ionic Liquids’ Structure Induced by CO2 Sorption

• Published in: Chemphyschem Vol. 21; no. 12; pp. 1230 - 1234
• Main Authors: Lepre, Luiz Fernando, Costa Gomes, Margarida, Ando, Rômulo Augusto
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 16.06.2020
• Subjects: Carbon dioxide; CO2-expanded solvents; ionic liquid structure; Ionic liquids; ionic solvents; Ions; Properties (attributes); Raman spectroscopy; Solvents; Sorption
• ISSN: 1439-4235; 1439-7641; 1439-7641
• DOI: 10.1002/cphc.202000109

The sorption of CO2 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 CO2 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 CO2 on the structure of ionic liquids. It is shown that CO2 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 CO2 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 CO2 sorption. Perturbing the polar domains: The effect of CO2 sorption on the structure of ionic liquids was investigated by means of Raman spectroscopy. The CO2 sorption perturbs the polar domain of these non‐volatile solvents, thus decreasing the Coulombic forces between their constituent ions. Such perturbations can be used to tune the macroscopic properties of ionic solvents and render these neoteric solvents more suitable media for synthesis, catalysis and separations.