Arginine-Based Ionic Liquid in a Water–DMSO Binary Mixture for Highly Efficient CO₂ Capture from Open Air

Abstract

Carbon dioxide (CO 2 ) absorption in the open air is essential for reducing the atmospheric CO 2 concentration and averting global climate change. The high CO 2 absorption capacity of amino acid-based ionic liquids (AAILs) makes them a more plausible carbon capture system than conventional amine solutions. We synthesized an ionic liquid derived from arginine, triethylmethylammonium argininate ([N 2221 ][Arg]), and utilized it to capture pure CO 2 and CO 2 from the open air. Although AAILs have some notable advantages for CO 2 capture, like low toxicity, biocompatibility, and superior stability, they also have important drawbacks, such as high viscosity and low mass transfer. Now, in order to resolve these problems, we blended [N 2221 ][Arg] with a binary mixture of water and dimethyl sulfoxide (DMSO) with a variable volume ratio. On increasing the volume of DMSO in water–DMSO binary mixtures, the CO 2 uptake gradually decreased, reaching a minimum in a pure DMSO medium and the maximum in an aqueous solution, which was obtained from the vapor–liquid equilibrium (VLE) experiment. We applied this [N 2221 ][Arg] ionic liquid in the aqueous medium to absorb CO 2 from direct air. The open-air CO 2 uptake value was approximately 1.01 mol/mol in the aqueous solution of arginine-based ionic liquid; to the best of our knowledge, this is the first report of such an ionic liquid system having high CO 2 absorption efficiency under ambient air. We believe that our system will be advantageous for removing CO 2 from highly polluted air.