Supercritical CO₂/Deep Eutectic Solvent Biphasic System as a New Green and Sustainable Solvent System for Different...

Deep eutectic solvents (DESs) are one of the most interesting research subjects in green chemistry nowadays. Due to their low toxicity, simple synthesis, and lower prices, they have gradually taken the place of other green solvents such as ionic liquids (ILs) in sustainable processes. However, problems such as high viscosity and high polarity limit the applications of DESs in areas such as extraction, catalysis, and biocatalysis. In this work, we introduce and evaluate the potential application of scCO₂/DES for the first time. Molecular dynamics simulations were used to examine the phase behavior, polarity, molecular mobilities, and microstructure of this system. Results show that CO₂ molecules can significantly diffuse to the DES phase, while DES components do not appear in the scCO₂ phase. The diffused CO₂ molecules significantly enhanced the molecular mobility of the DES components. The presence of CO₂ molecules changes the DES polarity so that hexane can be solubilized and dispersed in the DES phase. Radial distribution functions show that the solubilized CO₂ molecules have negligible effects on the microstructure of DES. It was shown that chloride and urea are the main interaction sites of CO₂ in DES. The results of this study show that scCO₂/DES as a new class of green and versatile solvents can open a new promising window for research in sustainable chemistry and engineering.