Electrochemiluminescence Monitoring of Microplastics Photodegradation Reveals a Superoxide Radical-Induced Hollowing-Collapse Mechanism on a COF@TiO ₂ Heterojunction

Photocatalysis offers a sustainable strategy for degrading microplastics (MPs), yet monitoring of the process remains a significant challenge. Herein, we report the solvothermal synthesis of a COF@TiO 2 heterojunction that integrates sensitive electrochemiluminescence (ECL) detection with the efficient visible-light-driven photocatalytic degradation of MPs. Notably, this study demonstrates the application of ECL to elucidate the photodegradation kinetics of polystyrene (PS), achieving approximately 98% degradation within 6 h and thereby establishing a sensitive platform for assessing catalytic performance. A combination of π–π stacking, hydrophobic, and electrostatic interactions between COF@TiO 2 and PS facilitates stable interfacial contact, which enhances both the ECL detection sensitivity and photocatalytic activity. The heterojunction favors selective superoxide radical (O 2 • – ) generation, owing to its optimized band alignment and efficient interfacial charge transfer. Mechanistic analysis reveals that this selective production of reactive oxygen species (ROS) drives a distinctive hollowing-collapse degradation pathway involving sequential surface erosion, internal disintegration, and eventual fragmentation. The efficacy of this mechanism is validated by the high degradation efficiency achieved for PS and its generalizability to other MPs, including polypropylene (PP) and poly(methyl methacrylate) (PMMA). Overall, this work provides new insights into selective ROS-mediated degradation and underscore the potential of COF-based heterojunctions as ECL-active analytical platforms for the precise monitoring and remediation of MPs.