Bridging molecular interactions and macroscopic thermodynamics in deep eutectic solvents for CO₂ capture

Abstract

Deep eutectic solvents (DESs) offer a sustainable route to low-energy CO₂ capture owing to their tunable structure, low volatility, and recyclability. However, establishing clear relationships between molecular structure, thermophysical behaviour, and gas solubility remains essential for the rational design of next-generation DES-based capture systems. In this work, we integrate semi-empirical modeling with molecular dynamics (MD) simulations to describe the thermophysical properties and CO₂ solubility of three prototypical DESs—Reline, Glyceline, and Ethaline. A perturbed hard-sphere equation of state (PHS EoS) was applied to predict density, compressibility, and viscosity up to 100 MPa, while a revised μ–μ framework was used to correlate CO₂ solubilities over the temperature range 303–343 K. The PHS EoS provided accurate predictions of thermophysical properties, and the revised μ–μ model reproduced CO₂ solubilities with deviations below 10%. MD simulations revealed stable hydrogen-bond networks that promote CO₂ retention through a combination of physical and chemical interactions. Overall, this integrated and data-efficient approach bridges molecular-scale structure and macroscopic thermodynamics, providing a rational pathway for designing environmentally benign solvents for carbon capture and green separation processes.