Investigation of the CO2 capture behavior in multiple-site natural deep eutectic solvents

The sustainable development of carbon dioxide (CO 2 ) resource requires the realization of green and efficient capture for the fossil fuel CO 2 . However, the high operation costs and biological toxicity have hampered the application. Natural deep eutectic solvents (NADESs) are efficient and green CO 2 absorbent. In this manuscript, kinds of amino acid-based NADESs were prepared successfully to improve the absorption efficiency of CO 2 capture solvent. The chemical structure of NADESs was characterized, and the thermal stability was also measured. The CO 2 capture behavior of amino acid-based NADESs was investigated. With multi-reactive sites, unstable stage and more accessibility of alkyl structure on HBA (alkyl amino acids and aromatic amino acids, especial L -Ary), and less electronegativity on HBD (EG), L -Arg/EG NADESs had lower solvation effect ( β value, 1.286) and reduced viscosity (48.33 mpa.s at 60 ºC). It behaved better absorption capacity . The optimized conditions by single-factor analysis and Response surface methodology were L -Arg/EG at the mole ratio of 1:5, 30 °C and 200 mL/min, and the absorption could reach 0.81 molCO 2 /kgNADESs. Additionally, an insight into the reaction mechanism was investigated. It was found that hydrogen-bond structure played an important role in CO 2 capture. The broken of H-O···H-N formed by amino acids and ethylene glycol promoted the formation of new bonds of -(O=)C···NHR between L -Arg/EG and CO 2 , thus achieved higher CO 2 capture. The investigated proved that the green solvent amino acid-based NADESs could be efficient absorbents for CO 2 capture.