Molecular layering and CO₂ selectivity in graphene-supported natural deep eutectic solvent films: An in-silico investigation

A multiscale computational study was conducted to investigate graphene-supported thin films composed of a natural deep eutectic solvent (NADES) formed by menthol and decanoic acid (MENTH:DA), with a focus on applications in sustainable CO₂ capture. Density functional theory (DFT) and molecular dynamics (MD) simulations were employed to elucidate interfacial structuring, molecular interactions, and gas adsorption behavior. DFT results indicated a strong interaction between decanoic acid and the graphene surface (−35.88 kJ/mol), characterized by a parallel orientation that maximizes van der Waals interactions. In contrast, menthol displayed weaker adsorption energies (−5.15 kJ/mol) and a predominantly perpendicular orientation. MD simulations revealed the formation of distinct adsorption layers, with decanoic acid enriched in the first layer and menthol in the second, while the NADES hydrogen-bonding network remained largely intact. CO₂ exhibited preferential adsorption over flue gas components (N₂, H₂O, O₂), with substantial accumulation in both the first and second interfacial layers. Approximately 50% of the CO₂ content from flue gas mixtures was retained within the structured region. Adsorption performance was found to be largely independent of temperature (303−323 K ) and NADES film thickness (20–50 Å). These results provide fundamental insight into NADES–graphene interactions and highlight the potential of type V, naturally derived deep eutectic solvents as selective and environmentally benign materials for CO₂ separation technologies. • Graphene supports stratified NADES films with stable layered organization. • Decanoic acid anchors to graphene; menthol enriches upper solvent layers. • CO₂ preferentially adsorbs in interfacial layers over N₂, H₂O, and O₂. • Film structure and CO₂ capture are robust across temperature and thickness. • NADES–graphene films offer a green, selective platform for CO₂ separation