Proton Donor-Induced intermolecular proton transfer boosts CO2 capture by Anion-Functionalized ionic liquids with weak basicity

As we know, ionic liquids (ILs) used for efficient carbon capture primarily depend on anions with strong basicity to form robust chemical interactions with CO 2 . However, these ILs often suffer from high regeneration consumption and low stability. Herein, for anion-functionalized ILs with weak basicity but high thermostability and low regeneration energy, we establish an intermolecular proton transfer reaction by introducing proton donors and thus a ternary synergistic system of “anion with weak basicity-proton donor-CO 2 ″ was created to activate and enhance the CO 2 binding efficiency. Delightfully, the introduction of these proton donors leads to a substantial increase in CO 2 absorption capacity, particularly in the presence of water, the absorption capacity of wet ILs is three to six times higher than that of dry ILs. The good stability of these systems is verified by continuous absorption and desorption cycle experiment. Through a combination of spectroscopic analysis and the DFT method, including noncovalent interaction (NCI) and reduced density gradient(RDG) analysis, we elucidate the chemical mechanism of CO 2 absorption by the IL-proton donor system. In the presence of proton donors, intermolecular proton transfer reactions occur between anions and proton donors, which activate nucleophilic oxygen sites on the donors to bind with CO 2 . This process drives the formation of thermodynamically favorable bicarbonate or carbonate species, thereby significantly enhancing CO 2 absorption capacity. The strategy offers novel perspectives for applying anion-functionalized ILs with weak basicity in CO 2 capture.