Evaluating the efficacy of amino acids as CO₂ capturing agents: a first principles investigation

Abstract

Comprehension of the basic concepts for the design of systems for CO₂ adsorption is imperative for increasing interest in technology for CO₂ capture from the effluents. The efficacy of 20 naturally occurring amino acids (AAs) is demonstrated as the most potent CO₂ capturing agents in the process of chemical absorption and physisorption through a systematic computational study using highly parametrized M05–2X/6-311+G(d,p) method. The ability of AAs to bind CO₂ both in the noncovalent and covalent fashion and presence of multiple adsorption sites with varying magnitude of binding strengths in all 20 AAs makes them as most promising materials in the process of physisorption. The binding energies (BEs) estimating the strength of noncovalent interaction of AAs and CO₂ are calculated and results are interpreted in terms of the nature and strength of the various types of cooperative interactions which are present. The study underlines the possibility to engineer the porous solid materials with extended networks by judiciously employing AA chains as linkers which can substantially augment their efficacy. Results show that a significant increase in the CO₂···AA affinity is achieved in the case of AAs with polar neutral side chains. Furthermore, the study proposes AAs as effective alternatives to alkanolamines in chemical dissolution of CO₂.