Role of surface oxygen functional groups in the adsorption of catechol, hydroquinone, and aniline on graphene oxide

Catechol (CT), hydroquinone (HQ), and aniline (AN) are environmentally significant aromatic pollutants that pose severe risks to human health even at trace levels. Their structural similarity makes selective detection and removal challenging, particularly on carbon-based adsorbents such as graphene oxide (GO). In this work, all-atom molecular dynamics (MD) simulations were employed to investigate the interfacial structure, dynamics, and adsorption behavior of CT, HQ, and AN on GO surfaces functionalized with epoxide (-O-), hydroxyl (-OH), and carboxyl (-COOH) groups. CT and HQ, as positional isomers, were compared to assess the impact of hydroxyl group arrangement, while AN served to evaluate the influence of a different functional group (-NH₂). Radial distribution function analysis revealed strong hydrogen-bonding interactions between molecular functional groups and oxygen-containing surface functionalities, with distinct second-neighbor peaks for CT and AN linked to their molecular geometry. HQ exhibited island-like aggregation on the surface, enabling simultaneous interaction via both hydroxyl groups and the aromatic ring, leading to enhanced affinity for -O- sites but reduced accessibility to -COOH groups. Native contact analysis indicated a parallel adsorption geometry for HQ, while CT and AN preferentially interacted via hydroxyl or amine-linked hydrogens. Interaction energy calculations confirmed that HQ had the strongest -O- affinity, whereas CT and AN showed balanced but slightly higher interactions with -O- and -COOH compared to -OH. These results elucidate the role of both surface chemistry and molecular structure in determining adsorption preferences and mobility, providing molecular-level guidelines for designing GO-based sensing and separation platforms for aromatic contaminants.