Imidazolium-Functionalized Anthraquinone for High-Capacity Electrochemical CO<sub>2</sub> Capture
Hiroki Iida, Shinji Kondou, Seiji Tsuzuki, Mao Tashiro, Naoki Shida, Ken Motokura, Kaoru Dokko, Masayoshi Watanabe, Kazuhide Ueno
Abstract
Electrochemical separation methods utilizing quinones as CO 2 capture agents have gained considerable interest owing to their low-energy requirements for near-isothermal CO 2 separation. However, the low solubility of quinones in nonaqueous solvents limits their total CO 2 carrying capacity in the system. In this study, we synthesized an ionically modified anthraquinone, 1-butyl-3-((2′-anthraquinoyl)methyl)imidazolium bis(trifluoromethanesulfonyl)amide ([BAQMIM][TFSA]), which exhibited a 360-fold increase in solubility compared to pristine anthraquinone in dimethyl sulfoxide. The synthesized ionic quinone derivative can also serve as a supporting electrolyte, offering both high ionic conductivity (12.2 mS cm –1 ) and quinone concentration (200 mM). Constant-potential electrolysis demonstrated a high CO 2 carrying capacity in a highly concentrated [BAQMIM][TFSA] solution. The predominantly reversible CO 2 capture and subsequent release processes were successfully monitored through in situ spectroscopic analysis and density functional theory calculations. These findings provide a promising approach toward large-scale volumetric CO 2 separation through the functionalization of quinones.