Fig. 5: Amine-CO₂ reactions in nonaqueous solvents.

a Regeneration of carbamic acid adduct via 1H⁺−1CO₂ pathway and carbamate adduct via 2H⁺−1CO₂ pathway. b ¹H NMR study of the amine-CO₂ reaction pathways in DMSO as a factor of amine concentration, supporting salt, and CO₂ partial pressure. Black, MEA (50 mM) under N₂; red, MEA (50 mM), HTFSI (50 mM) under N₂; blue, MEA (50 mM) saturated with 100% CO₂; green, MEA (50 mM) in DMSO with LiTFSI (500 mM) saturated with 100% CO₂; purple, MEA (500 mM) in DMSO with LiTFSI (500 mM) saturated with 100% CO₂; yellow, MEA (500 mM) in DMSO with LiTFSI (500 mM) saturated with 10% CO₂. c Illustration of the titration experiment setup. The solution was purged by a stream of 20% CO₂ (balanced with N₂) at a flow rate of 10 sccm. The CO₂ level at the exit of the septum-capped vial was monitored by an IR-based CO₂ sensor. For the CO₂ absorption experiment, various amounts of MEA were added to the vial containing either neat DMSO or DMSO with 0.5 M LiTFSI. For the CO₂ desorption experiment, a solution of MEA (500 mM) and LiTFSI (500 mM) in DMSO was saturated with 20% CO₂ and then added with various amounts of TfOH. For both experiments, the CO₂ level was allowed to return to 20% before the next addition. d CO₂ absorption capacity at various MEA concentrations. Grey, pure DMSO solvent; red, DMSO with 500 mM LiTFSI as the supporting salt. e CO₂ desorption capacity with various concentrations of TfOH added. Source data for Fig. 5 are provided as a Source Data file.