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Electrochemiluminescence Monitoring of Microplastics Photodegradation Reveals a Superoxide Radical-Induced Hollowing-Collapse Mechanism on a COF@TiO 2 Heterojunction
Summary
Researchers built a hybrid material — a covalent organic framework layered onto titanium dioxide — that can both degrade polystyrene microplastics under visible light and simultaneously monitor the degradation process using electrochemiluminescence. The system achieved roughly 98% breakdown of polystyrene within six hours, and revealed that the process proceeds through a superoxide radical mechanism that causes microplastic particles to hollow out and collapse. This dual detection-and-degradation platform advances both our understanding of photocatalytic microplastic breakdown and the development of real-time monitoring tools.
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@TiO2 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@TiO2 and PS facilitates stable interfacial contact, which enhances both the ECL detection sensitivity and photocatalytic activity. The heterojunction favors selective superoxide radical (O2• -) 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.