Physicochemical Properties of Ethylene Glycol-Based Deep Eutectic Solvents for CO2 Capture

Deep eutectic solvents (DESs) show great potential in the field of CO2 capture; however, the lack of systematic physicochemical property data remains a bottleneck constraining their rational design and industrial application. This study prepared six representative DESs and systematically characterized their key fundamental properties as absorbents: density, viscosity, thermal stability, and specific heat capacity. The results indicate that the chemical structure of the hydrogen bond acceptor has a decisive influence on the properties of the DESs. The viscosity and density of all DESs decreased significantly with increasing temperature. Thermogravimetric analysis revealed their varying thermal stabilities, with the onset decomposition temperature ranging from 366.52 K (menthol–ethylene glycol) to 415.17 K (choline chloride–ethylene glycol). The measurement of specific heat capacity data provides a key basis for evaluating solvent regeneration energy consumption. This study fills the gap in systematic property data of various DESs. Comprehensive analysis indicates that the choline chloride-ethylene glycol system achieves the best balance among viscosity, thermal stability, and specific heat capacity, making it a highly promising candidate based on its physicochemical property profile for CO2 capture among the studied systems. This work provides solid data support and theoretical guidance for the screening, design, and energy optimization of DESs in CO2 capture processes.