Insight into microplastic-derived DOM modulation of interfacial reactive pathways in covalent triazine framework photocatalysis

Dissolved organic matter (DOM), ubiquitous in natural and treated waters, strongly modulates photocatalytic processes by regulating interfacial electron and energy transfer. However, the component-specific effects of different DOM types, particularly microplastic-derived DOM (MP-DOM), on photocatalyst-pollutant interfacial photochemistry remain poorly understood. In this study, we developed a nitrogen-vacancy engineered covalent triazine framework (N-CTF-0.03) as a visible-light-driven photocatalyst, which exhibited enhanced adsorption and strong resilience to interference from coexisting DOM. The photocatalytic degradation of bisphenol A (BPA) and naphthalene (NAP) was systematically assessed in the presence of humic acid (HA) and MP-DOM (PE-, PS-, and PET-DOM), and •O was identified as the dominant reactive oxygen species (ROS). Competitive kinetic analysis revealed strong DOM-dependent modulation. HA suppressed ROS generation, likely via competitive light absorption or quenching, whereas PET-DOM markedly promoted ROS production through π-π interactions and defect-site coordination, facilitating directional electron transfer. Mechanistic investigations integrating 3D excitation-emission matrix fluorescence combined with fluorescence regional integration (3D EEM-FRI), electron transfer capacity measurements, and density functional theory (DFT) calculations indicate that PET-DOM, enriched in oxygenated functional groups and fulvic acid-like moieties, enhances N-CTF-0.03 photocatalysis via dual pathways, mediating energy transfer to promote O reduction to •O and facilitating interfacial electron-hole separation through its distinctive electron donor-acceptor properties. These findings establish PET-DOM as a component-specific photochemical mediator and provide mechanistic guidance for designing DOM-resilient, high-performance photocatalysts in complex aquatic systems.