Carbon dioxide dehydration with choline‐based deep eutectic solvents: Pitzer–Debye–Hückel ‐corrected COSMO ‐ RS modeling and molecular insights

CO 2 dehydration is critical for carbon capture and storage. Choline chloride (ChCl)‐based deep eutectic solvents (DESs) offer a promising green alternative due to their low volatility, tunable structure, and strong water affinity. This study combines predictive thermodynamic modeling with molecular simulations to evaluate four ChCl‐based DESs (Ethaline, Glyceline, Reline, and Maline) as CO 2 dehydration media. The prediction accuracy of COSMO‐RS, COSMO‐RS‐PDH, and COSMO‐SAC‐DHB‐PDH is systematically compared for CO 2 /water/DES ternary systems. The Pitzer–Debye–Hückel correction is essential for concentrated aqueous DES mixtures, reducing the overall average relative deviations from 19% to 20% (COSMO‐RS) to 7.74% (COSMO‐RS‐PDH) and improving outlier control (COSMO‐SAC‐DHB‐PDH). Density functional theory and molecular dynamics simulations reveal that chloride anions dominate the hydrogen‐bond network, while hydrogen‐bond donor topology modulates network rigidity, free volume, and water‐binding affinity. This work provides reliable thermodynamic models and molecular insights for the rational design of efficient DES‐based dehydrants for CO 2 capture pre‐treatment.