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Uptake of CO2 by choline acetate under ambient conditions: an NMR study and the role of hydration

Year: 2026
Type: article
Abstract: The objective of this study was to investigate the passive CO 2 uptake by choline acetate under laboratory-scale static ambient-air exposure, compared to its uptake under pure CO 2 . The perspective is to use further the CO 2 concentrated in this ionic liquid in electrochemical conversion. Quantitative NMR analysis was used to quantify the CO 2 -derived species formed during absorption as well as the water content. The use of 13 C-enriched CO 2 enables the determination of the chemical nature of the CO 2 derived species and ensures high measurement precision, even at very low CO 2 concentrations (≈500 ppm) close to atmospheric levels. The results show that choline acetate, even under passive conditions, absorbs CO 2 directly from ambient air, reaching an uptake of 0.08 mmol/g, which is 4 times the atmospheric CO 2 concentration. Under pure CO 2 and without stirring, the material achieved its highest uptake of 1.24 mmol/g, which is 62 times the atmospheric concentration. NMR analysis showed that the CO 2 absorbed is primarily in the form of bicarbonate. We also investigated the influence of water content on CO 2 uptake. A water/choline acetate molar ratio of 1.7 enabled the highest CO 2 uptake. To assess whether the CO 2 -loaded system could serve as a basis for future electrochemical studies, its ionic conductivity and cyclic voltammetry was also examined. An optimal conductivity of 30 mS.cm −1 was measured for a water/choline acetate molar ratio between 10 and 20, placing this bio-sourced ionic liquid in the same range as common non-fluorinated ionic liquids like EMIM ES (40 mS.cm −1 ).
DOI: 10.1016/j.ces.2026.124870
Language: English
Open Access status: hybrid
Estimated APC paid: $4,050
OpenAlex ID: W7202216003
FWCI:
Cites: 67
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Related to: 10