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Title: Molecular insight into the anion effect and free volume effect of CO 2 solubility in multivalent ionic liquids
For many years, experimental and theoretical studies have investigated the solubility of CO 2 in a variety of ionic liquids (ILs), but the overarching absorption mechanism is still unclear. Currently, two different factors are believed to dominate the absorption performance: (a) the fractional free volume (FFV) accessible for absorption; and (b) the nature of the CO 2 interactions with the anion species. The FFV is often more influential than the specific choice of the anion, but neither mechanism provides a complete picture. Herein, we have attempted to decouple these mechanisms in order to provide a more definitive molecular-level perspective of CO 2 absorption in IL solvents. We simulate a series of nine different multivalent ILs comprised of imidazolium cations and sulfonate/sulfonimide anions tethered to benzene rings, along with a comprehensive analysis of the CO 2 absorption and underlying molecular-level features. We find that the CO 2 solubility has a very strong, linear correlation with respect to FFV, but only when comparisons are constrained to a common anion species. The choice of anion results in a fundamental remapping of the correlation between CO 2 solubility and FFV. Overall, the free volume effect dominates in the ILs with smaller FFV values, while the choice of anion becomes more important in the systems with larger FFVs. Our proposed mechanistic map is intended to provide a more consistent framework for guiding further IL design for gas absorption applications.  more » « less
Award ID(s):
1605411
NSF-PAR ID:
10302197
Author(s) / Creator(s):
; ; ;
Date Published:
Journal Name:
Physical Chemistry Chemical Physics
Volume:
22
Issue:
36
ISSN:
1463-9076
Page Range / eLocation ID:
20618 to 20633
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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