(84a) A Nanoscopic Explanation on Hydrophobic Deep Eutectic Solvents and Their Carbon Dioxide Solubility Performance

Type V Natural Deep Eutectic Solvents (NADES) considering carvone, 1,8-cineole, menthol, thymol are studied considering a theoretical approach with the purpose of developing a multiscale characterization of these fluids with particular attention to intermolecular forces (hydrogen bonding) of NADES and carbon dioxide, and their relationships with macroscopic behavior. Supporting experimental data has also been collected during this study and compared to theoretical data. Density functional theory (DFT) calculations with at B3LYP/6-311++G** theory levels and we have shown that this theory/basis-set combination works very well on such systems. Quantum Theory of Atoms in a Molecule (QTAIM, Bader's theory) using MultiWFN code has been applied for the analysis of bonding structures and strengths between the hydrogen bond acceptor and hydrogen bond donor of the NADES between the carbon dioxide molecule. From this analysis, interaction regions are characterized by the developed bond critical points and the corresponding values of electron density, ρ, and the Laplacian (∇) of electron density, ∇²Ï. Classical molecular dynamics simulations were also performed allowing to characterize bulk liquid phases at the nanoscopic level, analyzing the fluid’s structuring, voids distribution and dynamics. The reported results allowed to infer nano – macro relationships, which are required for the proper design of these green solvents and their application for different technologies. 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.