Novel Hydrazide-Based Ionic Liquid Aqueous Solutions Realize CO2 Capture through the Multisite Synergistic Action of N and O Atoms

A new strategy for enhancing the hydrazine structure based on the inductive effect and conjugation effect of strong electron-withdrawing groups has been designed to effectively absorb CO 2 with hydrazide-based ionic liquids (ILs). All three ILs aqueous solutions (diethylenetriamine oxalyl dihydrazide [DETAH] 2 [ODH], diethylenetriamine propanedioyl dihydrazide [DETAH] 2 [PDH], and diethylenetriamine succinic dihydrazide [DETAH] 2 [SDH]) exhibit good absorption performance. Through a combination of absorption–desorption experiments, FT-IR and NMR characterizations, and density functional theory (DFT) calculations, the results indicate that the unique structure of anions enables physical adsorption to occur again after chemically absorbing CO 2 . The special absorption process is responsible for the unusual regeneration properties. Hopefully, the results of this work are helpful in providing a new method for designing highly efficient gas absorbents.