CO2 Capture in Ionic Liquids Based on Amino Acid Anions With Protic Side Chains: a Computational Assessment of Kinetically Efficient Reaction Mechanisms

Absorption and capture of CO2 directly from sources represents one of the major tools to reduce its emission in the tropo- sphere. One of the possibilities is to incorporate CO2 inside a liquid exploiting its propensity to react with amino groups to yield carbamic acid or carbamates. A particular class of ionic liquids, based on amino acids, appear to represent a possible efficient medium for CO2 capture because, at difference with current industrial setups, they have the appeal of a biocompat- ible and environmentally benign solution. We have investi- gated, by means of highly accurate computations, the feasibility of the reaction that incorporates CO2 in an amino acid anion with a protic side chain and ultimately transforms it into a carbamate derivative. Through an extensive exploration of the possible reaction mechanisms, we have found that different prototypes of amino acid anions present barrierless reaction mechanisms toward CO2 absorption.