Functionalized Ionic Liquids for CO2 Capture under Ambient Pressure.

Abstract

Ionic liquids (ILs) have been widely explored as alternative solvents for carbon dioxide (CO₂) capture and utilization. However, most of these processes are under pressures significantly higher than atmospheric level, which not only levies additional equipment and operation costs, but also makes the large-scale CO₂ capture and conversion less practical. In this study, we rationally designed glycol ether-functionalized imidazolium, phosphonium and ammonium ILs containing acetate (OAc^-) or Tf₂N^- anions, and found these task-specific ILs could solubilize up to 0.55 mol CO₂ per mole of IL (or 5.9 wt% CO₂) at room temperature and atmospheric pressure. Although acetate anions enabled a better capture of CO₂, Tf₂N^- anions are more compatible with alcohol dehydrogenase (ADH), which is a key enzyme involved in the cascade enzymatic conversion of CO₂ to methanol. Our promising results indicate the possibility of CO₂ capture under ambient pressure and its enzymatic conversion to valuable commodity.