Agrochemical residues and food safety: In-depth in silico assessment of the degradation mechanism of chlorpyrifos-oxon by niobium dioxide (NbO₂), a naturally occurring and cost-effective mineral

CONTEXT: The widespread use of chlorpyrifos-based pesticides has raised increasing concerns regarding environmental persistence, food safety, and human exposure to toxic organophosphate residues. In this work, the degradation mechanism of chlorpyrifos-oxon mediated by niobium dioxide (NbO₂), a naturally occurring and low-cost mineral, was investigated through in silico approaches. The results indicate that NbO₂ can promote the degradation of chlorpyrifos-oxon through energetically favorable pathways, reducing activation barriers and stabilizing key intermediates along the reaction coordinate. Electronic structure analyses revealed significant charge redistribution during the degradation process, supporting the catalytic role of the mineral surface. These findings reinforce the potential application of NbO₂ as an accessible material for agrochemical remediation and food safety strategies. METHODS: Density functional theory calculations were performed using the ωB97X-D3 functional with the def2-TZVP basis set. Geometry optimizations, vibrational frequency analyses, intrinsic reaction coordinate calculations, and electronic structure analyses were carried out using ORCA software. Solvent effects were considered through an implicit solvation model to better represent the reaction environment.