Uptake of CO₂ by choline acetate under ambient conditions: an NMR study and the role of hydration
Abstract
The objective of this study was to investigate the passive CO₂ uptake by choline acetate under laboratory-scale static ambient-air exposure, compared to its uptake under pure CO2. The perspective is to use further the CO₂ concentrated in this ionic liquid in electrochemical conversion. Quantitative NMR analysis was used to quantify the CO₂-derived species formed during absorption as well as the water content. The use of ¹³C-enriched CO₂ enables the determination of the chemical nature of the CO₂ derived species and ensures high measurement precision, even at very low CO₂ concentrations (≈500 ppm) close to atmospheric levels. The results show that choline acetate, even under passive conditions, absorbs CO₂ directly from ambient air, reaching an uptake of 0.08 mmol/g, which is 4 times the atmospheric CO₂ concentration. Under pure CO₂ 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 CO₂ absorbed is primarily in the form of bicarbonate. We also investigated the influence of water content on CO₂ uptake. A water/choline acetate molar ratio of 1.7 enabled the highest CO₂ uptake. To assess whether the CO₂-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).
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BibTeX
@article{wu2026uptake,
title = {{Uptake of CO₂ by choline acetate under ambient conditions: an NMR study and the role of hydration}},
author = {Boya Wu and Christophe Coudret and Marc Vedrenne and Gonzalo Guirado and Juliette Fitremann},
journal = {Chemical Engineering Science},
year = {2026},
month = sep,
doi = {10.1016/j.ces.2026.124870},
url = {https://hal.science/hal-05740245v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Uptake of CO₂ by choline acetate under ambient conditions: an NMR study and the role of hydration
AU - Boya Wu
AU - Christophe Coudret
AU - Marc Vedrenne
AU - Gonzalo Guirado
AU - Juliette Fitremann
PY - 2026
DA - 2026/09/08
JO - Chemical Engineering Science
DO - 10.1016/j.ces.2026.124870
UR - https://hal.science/hal-05740245v1
AB - The objective of this study was to investigate the passive CO₂ uptake by choline acetate under laboratory-scale static ambient-air exposure, compared to its uptake under pure CO2. The perspective is to use further the CO₂ concentrated in this ionic liquid in electrochemical conversion. Quantitative NMR analysis was used to quantify the CO₂-derived species formed during absorption as well as the water content. The use of ¹³C-enriched CO₂ enables the determination of the chemical nature of the CO₂ derived species and ensures high measurement precision, even at very low CO₂ concentrations (≈500 ppm) close to atmospheric levels. The results show that choline acetate, even under passive conditions, absorbs CO₂ directly from ambient air, reaching an uptake of 0.08 mmol/g, which is 4 times the atmospheric CO₂ concentration. Under pure CO₂ 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 CO₂ absorbed is primarily in the form of bicarbonate. We also investigated the influence of water content on CO₂ uptake. A water/choline acetate molar ratio of 1.7 enabled the highest CO₂ uptake. To assess whether the CO₂-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).
SN - 0009-2509
SN - 1873-4405
ER -