Unveiling Molecular Features Controlling the Solubility of Hydrofluorocarbons in Fluorine-Based Eutectic Solvents

Abstract

This work investigates the solubility and solvation mechanisms of fluorinated refrigerant gases in fluorine-based deep eutectic solvents (FESs) using COSMO-RS and molecular dynamics simulations. Three FESs based on perfluoropentanoic acid (PFPA) as a hydrogen bond donor were evaluated to understand how ionic and molecular hydrogen-bond acceptors influence the absorption of HFCs (R125, R134a, and R32). The molecular models were validated through computed densities and activity-coefficient-based thermodynamics, confirming their liquid behavior. Structural and energetic analyses, including distribution functions and free-energy perturbation, show that the solubility is driven by synergistic fluorinated dispersion interactions, ionic polarization, and PFPA self-association. These specific interactions between PFPA fluorinated domains and ionic species define the eutectic network and govern HFC uptake, providing a rational basis for designing advanced fluorinated solvents for refrigerant recovery in a circular economy context.