Efficient Hydrogen Peroxide Photosynthesis over CdS/COF for Water Disinfection: The S-Scheme Pathway, Oxygen Adsorption, and Reactor Design

Solar-driven photocatalytic hydrogen peroxide (H2O2) production presents a promising avenue for achieving sustainable water disinfection. However, the development of a robust and durable system for practical applications remains a notable and unresolved challenge. Herein, a star photocatalyst, the covalent organic frameworks (COFs), was modified with CdS for boosting environmentally benign H2O2 synthesis. Under simulated sunlight and without sacrificial reagents, the composite material exhibited a boosting capacity for H2O2 production, which was attributable to the establishment of a "step" (S)-scheme transfer pathway and facilitation of adequate oxygen diffusion. Nevertheless, it was found that photocatalytically derived H2O2 alone exhibited inefficient disinfection performance, whereas the addition of Fe(II) allowed rapid inactivation of Escherichia coli, emphasizing the pivotal importance of integrating photocatalysis and Fenton reactions within the photocatalytic H2O2 production system. Furthermore, a dual-compartment reactor, employing a semipermeable membrane, was devised to spatially segregate photocatalysts from microorganisms. Such an operation mode enabled H2O2 diffusion from the photocatalytic compartment to the microbial compartment, thereby achieving a "long-distance" sterilization manner and simultaneous consummating recovery strategy of the photocatalysts. This study not only provides a paradigmatic approach for boosting the production of H2O2 from a COF-based material but also illuminates an innovative technological option for sustainable photocatalytic-based water disinfection.