Ether Functionalized Choline Tethered Amino Acid Ionic Liquids for Enhanced CO₂Capture

Abstract

Amino acid ionic liquids (ILs) are the most interesting and effective for CO2 capture due to their low toxicity, biodegradability, and fast reactivity toward CO2. The ionic nature of amino acid ILs can raise an environmental issue if the cation counterpart becomes toxic to the aquatic ecosystems, and they can become potential atmospheric pollutants. In this regard, choline based ILs are known to be promising scaffolds for the development of less toxic amino acid ILs. However, the existing choline amino acid ILs are highly viscous, limiting their applicability as solvents. Ether functionalized choline based amino acid ILs with a novel series of less toxic green ILs were explored with reduced viscosity and high CO2 capture capacity. A simple, economic, clean, and environmentally benign method was utilized for the synthesis of novel choline based amino acid ILs using a commercially available and economical starting material, 2-(dimethylamino)ethanol (deanol, a human dietary food supplement). These ILs have low viscosity with high CO2 capture capacity (1.62 mol of CO2 /mol of IL, 4.31 mol of CO2/kg of IL, 19.02 wt % of CO2). The mechanism of [N1,1,6,2O4][Lys] + CO2 reaction and adduct structure was proposed by using DFT calculations, and IR and NMR spectroscopic techniques.