Defect-activated anatase TiO2 surfaces for enhanced capture of bisphenol S and sulfolane: A coupled DFT and SCC-DFTB analysis

Abstract

Titanium dioxide (TiO₂) has emerged as a vital nanomaterial for environmental remediation, yet the adsorption mechanisms of persistent contaminants such as Bisphenol S (BisS) and Sulfolane (SulF) remain insufficiently understood. In this study, a hybrid computational framework; combining quantum chemical methods, COSMO-RS modeling, and self-consistent charge density-functional tight-binding (SCC-DFTB) simulations, was employed to investigate how BisS and SulF interact with pristine and oxygen-vacancy-modified anatase TiO₂. Chemical reactivity descriptors highlighted BisS’s greater propensity for electron donation and acceptance, while SulF’s sulfone group emerged as a localized site for bonding. The COSMO-RS results revealed both molecules to be strong hydrogen-bond acceptors, pointing to robust polar interactions under aqueous conditions. SCC-DFTB calculations showed enhanced adsorption on defect-rich surfaces, with BisS exhibiting binding energies of –2.39  eV (defected) and –2.05  eV (pristine), whereas SulF binds with –1.91  eV and –1.18  eV, respectively. Projected density of states (PDOS) analyses indicated significant orbital mixing and peak broadening upon adsorption, emphasizing how surface defects can intensify pollutant–TiO₂ interactions. Overall, these findings demonstrate that molecular functionalities and lattice vacancies synergistically control adsorption strength, offering a pathway for targeted pollutant removal strategies.