Exploiting proton masking to protect amino achieve efficient capture CO2 by amino-acids deep eutectic solvents

Abstract

In previous studies, high captures of CO2 by alkaline Amino-acids DESs were found and reported, as well as kinetic studies of CO2 capture by amino acids. Based on the above works, we have attempted to enhance the capture of CO2 by amino-acids DESs through non-aqueous, non-superbase modification scheme with the addition of triethanolamine (TEA), a buffering agent, to the hydrogen bond donor (HBD) to mask the protons and protect the amino groups. However, the interaction mechanism of CO2 capture by basic amino acids are not fully understood. In this study, we investigated the effect of HBD modification of l-Arg DESs on CO2 capture and the effect of prepare and modification of l-Lys DESs on CO2 capture. The experimental data showed that the CO2 loading reached 1.194 mol/mol when l-Arg: GLY: TEA was 1:3:3 and 1.378 mol/mol when l-Lys: GLY: TEA was 1:3:3, and both had good regeneration ability. Based on 13C NMR, In-suit IR and quantum chemical calculations, it was found that the amino group at the guanidine position in l-Arg was not reactive and the attack of CO2 was directed towards the imino site because of sp2 hybridization. l-Lys DESs showed phase change during the reaction and were waxy. After In-suit ATR, the internal salt formation of l-Lys mainly caused this behaviour.