Development of Energy-Efficient Nonaqueous Deep Eutectic Solvents for Carbon Capture: Properties, Performance, and Mechanism

Considering that the combustion of fossil fuels is the primary source of CO2 emission, it is crucial to focus on postcombustion carbon capture. Deep eutectic solvents (DES) are potential CO2 absorbents. However, research overemphasizes their absorption capacity, thus lacking comprehensiveness. In this work, eight DESs were prepared. 1,5-Diazabicyclo[4.3.0]non-5-ene (DBN), benzimidazole (Benz), and 2-oxazolidone (Oxa) were selected to form [DBN][Benz] and [DBN][Oxa] as hydrogen bond acceptors and ethylene glycol (EG) as the hydrogen bond donor. The research aims to establish a comprehensive evaluation system for DES nonaqueous absorbents based on excellent absorption performance, fast absorption rate, and excellent cycle performance, with low-regeneration energy consumption as the guiding principle. It also considers good thermal stability and low/no ecological toxicity. It has been measured that 1 g of [DBN][Oxa]–EG (1:0.5) could absorb 0.1679 g of CO2 and the regeneration energy consumption could reduce by 70.41% compared to that of 30 wt % monoethanolamine. The absorption ability of EG is activated to generate carbonate instead of carbamate, which is metastable and thus helps reduce energy consumption.