Functionalized ionic liquids for CO 2 capture under ambient pressure

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.