(406c) CO2 Capture Under Ambient Conditions in Functionalized Ionic Liquids

Ionic liquids (ILs) are becoming attractive solvents for CO₂ capture due to their versatile structures, but most physisorption processes in ILs required relatively high pressures (>10 bar). IL anions have strong influence on CO₂ solubility; fluorinated anions such as bis(trifluoromethylsulfonyl)imide (Tf₂N^‒) and acetate (OAc^–) tend to have strong interactions with CO₂ molecules. We designed glycol ether-functionalized ILs carrying imidazolium, phosphonium or ammonium cations along with OAc^– or Tf₂N^– anions, and determined that these task-specific ILs captured up to 0.55 mol CO₂ per mole of IL (or 5.9 wt% CO₂) at room temperature and atmospheric pressure. Alcohol dehydrogenase (ADH) is one of the key enzymes used in the cascade enzymatic process to convert CO₂ to methanol, and we found that ADH was more active in aqueous solutions of Tf₂N^‒ based ILs than acetate analogues. This study allows us to better understand the relationship between IL structure and CO₂ solubility, and enables us to design low-cost solvent systems for large-scale CO₂ capture under ambient conditions.