Surpassing the Performance of Phenolate‐derived Ionic Liquids in CO2 Chemisorption by Harnessing the Robust Nature of Pyrazolonates

Abstract Superbase‐derived ionic liquids (SILs) are promising sorbents to tackle the carbon challenge featured by tunable interaction strength with CO 2 via structural engineering, particularly the oxygenate‐derived counterparts (e. g., phenolate). However, for the widely deployed phenolate‐derived SILs, unsolved stability issues severely limited their applications leading to unfavorable and diminished CO 2 chemisorption performance caused by ylide formation‐involved side reactions and the phenolate‐quinone transformation via auto‐oxidation. In this work, robust pyrazolonate‐derived SILs possessing anti‐oxidation nature were developed by introducing aza‐fused rings in the oxygenate‐derived anions, which delivered promising and tunable CO 2 uptake capacity surpassing the phenolate‐based SIL via a carbonate formation pathway (O−C bond formation), as illustrated by detailed spectroscopy studies. Further theoretical calculations and experimental comparisons demonstrated the more favorable reaction enthalpy and improved anti‐oxidation properties of the pyrazolonate‐derived SILs compared with phenolate anions. The achievements being made in this work provides a promising approach to achieve efficient carbon capture by combining the benefits of strong interaction strength of oxygenate species with CO 2 and the stability improvement enabled by aza‐fused rings introduction.