Enhancing the low concentration CO2-capture abilities of aminium ionic liquids through blending with acetate ionic liquids

The efficient capture of low-concentration CO 2 is essential for achieving carbon neutrality and recycling. This study explored aminium and acetate ionic liquid (IL) mixtures for enhanced CO 2 capture. The physical properties, nuclear magnetic resonance spectra, and CO 2 solubilities of the mixtures of N -2-hydroxyethyl-aminoethylaminium bis(trifluoromethanesulfonyl)imide ( 1 ·[Tf 2 N]) and 1-ethyl-3-methylimidazolium acetate ([C 2 mim][AcO]) were compared with those of the corresponding [C 2 mim][Tf 2 N] mixtures. It was found that the mixtures were less dense and viscous than the pure aminium IL, enabling faster absorption/desorption kinetics and lowering energy consumption. In addition, mixtures containing 10 and 30 mol% 1 ·[Tf 2 N] absorbed greater amounts of CO 2 than the pure ILs at CO 2 partial pressures of up to 10 kPa, with a lower absorption heat than pure 1 ·[Tf 2 N]. This was attributed to the formation of nonionic components via proton recombination, along with the suppression of ammonium formation by proton sharing between the CO 2 adduct and the [AcO] − anions. Blending [C 2 mim][AcO] with other aminium ILs further enhanced the CO 2 absorption capability at low partial pressures, offering a higher CO 2 solubility and a lower enthalpy compared to the 1 ·[Tf 2 N] mixture. Overall, the results indicated that mixing aminium ILs with [C 2 mim][AcO] enhances low-concentration CO 2 capture and is applicable to various aminium ILs, providing an effective alternative to chemical modification for the development of CO 2 separation materials. • Aminium–acetate ionic liquid mixtures enhance CO 2 capture at low concentrations. • These mixtures are less dense and viscous compared to pure aminium ionic liquids. • The mixture absorbs more CO 2 than pure aminium and exhibit a lower absorption heat. • Blending offers a new approach for developing superior CO 2 separation materials.