Reversible methyldiethanolamine-based deep eutectic solvents capture CO2: Experiments and molecular mechanisms

Methyldiethanolamine (MDEA), an efficient and environmentally friendly absorbent, has been widely used in CO 2 capture. This study prepared and evaluated two novel ternary MDEA-based deep eutectic solvents (DES1 and DES2) for CO 2 capture performance. Experimental results show that the maximum CO 2 absorption capacities of DES1 and DES2 were 0.1237 and 0.1016 g CO 2 /g DES, with viscosities of 14 and 9.6 mPa s at 50 wt% water content. After five absorption–desorption cycles, DES1 maintained 82% of its initial absorption efficiency. Nuclear magnetic resonance analysis confirms the successful synthesis of DESs, which effectively absorb CO 2 . After regeneration, the structure remains unchanged despite chemical absorption, indicating the reversibility of MDEA-based DESs. Molecular-level analysis indicates that the DES1 capture CO 2 process involves physical absorption and chemical reactions. Specifically, ethanolamine reacts with CO 2 to form carbamate, and the interaction energy between CO 2 and MDEA is −2699.40 kJ/mol.