Investigating the microscopic mechanisms of deep eutectic solvents formed with natural compounds: Multiscale simulation and cross-validation

Designing eco-friendly deep eutectic solvents (DESs) for industrial applications relies on choosing environmentally sustainable hydrogen bond acceptors (HBAs) and donors (HBDs). The study of the weak interactions between these components are essential to assess the performance of DESs in extraction and separation processes. However, there remains a dearth of knowledge regarding the molecular mechanisms influencing the structure-activity relationships in DES systems. This work introduces a new multiscale simulation analytical approach based on the mechanism revealed by the HBA-HBD interaction sites. Quantum chemical (QC) calculations were used to calculate the binding energy, weak interaction type and charge transfer analysis of each site. And the obtained microscopic mechanism was subsequently applied to a real macroscopic phenol-toluene separation system for cross-validation. Molecular dynamics (MD) simulations further illuminate the impact of HBA structure on the extraction process at the molecular level, corroborating QC calculation results. Notably, this underscores the significance of HBAs structure interactions with phenol. The multiple interaction sites of the L-carnitine structure with phenol validate the use of a lower L-carnitine dosage compared to ChCl and betaine in the liquid-liquid extraction (LLE) experiments. These results extend to advancing understanding of eco-friendly DESs, providing a basis for the development of sustainable and efficient extraction processes. [Display omitted] •Two natural, non-toxic compounds betaine and L-carnitine were chosen as HBAs.•The relationship between the structure of HBAs and their ability to segregate was elucidated by focusing on the interaction sites of HBAs with phenol.•QC calculations were used to compare the microscopic mechanisms of interaction between interaction sites in each system.•The microscopic mechanism was applied to the macroscopic system for cross-checking and mutual verification.