Absorption and capture of CO 2 directly from sources represents one of the major tools to reduce its emission in the troposphere. One of the possibilities is to incorporate CO 2 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 CO 2 capture because, at difference with current industrial setups, they have the appeal of a biocompat-ible and environmentally benign solution. We have investigated, by means of highly accurate computations, the feasibility of the reaction that incorporates CO 2 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 CO 2 absorption.

CO 2 capture at the production site represents one of the accessible ways to reduce its emission in the atmosphere. In this context, CO 2 chemisorption is particularly advantageous and is often based on exploiting a liquid containing amino groups that can trap CO 2 due to their propensity to react with it to yield carbamic derivatives. A well-known class of ionic liquids based on amino acid anions might represent an ideal medium for CO 2 capture because, at difference with present implementations, they are known to be fully biocompatible. One of the problems is however the relatively low molar ratio of CO 2 absorption. Increasing this ratio turns out to be possible by choosing appropriate anions. We present here a set of accurate computations to elucidate the possible reaction paths that allow the anion to absorb two CO 2 molecules, thus effectively doubling the overall intake. An extensive exploration of some reaction mechanisms suggests that some of them might be quite efficient even under mild conditions.