Natural deep eutectic solvents (NADES) are studied in this work on their carbon dioxide (CO2) capture performances. Monoterpenoids (cineole, carvone) we used as hydrogen bond acceptors (HBA), and they are mixed with other terpenes (menthol, thymol) and organic acids (malic acid (MA), salicylic acid (SA), tartaric acid (TA), lactic acid (LA)) are studied using a combined experimental and molecular modeling approach. The reported physicochemical properties showed low viscous fluids whose properties were characterized as a function of temperature. CO₂ solubility performance of studied NADES systems have been investigated via high pressure isochoric apparatus experimentally and benchmarked against the other green solvents. The COSMO-RS predictions are compared against the experimental solubility data. The theoretical study combining quantum chemistry (DFT) and classical molecular dynamics (MD) simulations provided a nanoscopic characterization of the fluids, particularly for the hydrogen bonding network and its relationship with the macroscopic properties.
The considered fluids constitute a suitable type of solvents considering their properties, cost, origin, and sustainability in different technological applications and sow the possibility of developing type V NADES from different types of molecules, especially in the terpenoid family of compounds. DFT and MD studies provide a nanoscopic characterization of the fluid paying particular attention to the hydrogen bonding structure in the NADES. Likewise, prediction of selected thermophysical properties using machine learning (ML) methods was carried out to develop predictive tools for Type V NADES, which would allow in silico development of new fluids. The reported results provide a micro and macroscopic characterization of type V NADES allowing to infer the role of intermolecular forces as well to contribute to the development of rules for designing suitable DES involving non-ionic species. It has been shown that the suitable interactions of NADES with CO₂ did not result disruptions in the solvent hydrogen bonding network. Moreover, predicted ecotoxicological properties have showed low impact fluids, which may be considered as suitable alternatives for different operations including carbon capture.

Santiago Aparicio-Martinez

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