Objective In order to find a new absorbent with good absorption performance, low solvent loss, and low energy consumption for CO₂ capture, the preparation and performance of guanidine amino acid ionic liquids to capture CO₂ in flue gas was investigated.

Methods Three kinds of guanidine amino acid ionic liquids with low viscosity, namely TMG Lys, TMG Ala, and TMG Asp, were prepared using tetramethylguanidine (TMG) as a cation and lysine (Lys), alanine (Ala), and aspartic acid (Asp) as anions. The effects of anionic types on CO₂ absorption were investigated.

Results The alkaline TMG Lys had a higher CO₂ absorption, with a CO₂ absorption capacity of 0.64 mol CO₂/mol IL under the condition of atmospheric pressure, 45 ℃, and 80 mL/min. The addition of water had a positive effect on the absorption of CO₂. The absorption capacity of 30 wt% TMGLys aqueous solution increased to 0.99 mol CO₂/mol IL and could still keep 0.81 mol CO₂/mol IL after 5 absorption-desorption cycles. The decarbonization mechanism of TMG Lys was analyzed by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance hydrogen spectroscopy (¹H-NMR). CO₂ mainly reacts with the amino group on the anion to form carbamate to achieve efficient capture of CO₂ in the flue gas.

Conclusions It can provide reference for the development of new absorbents in industrial CO₂ capture.