Constructing S-scheme heterojunction between porphyrinyl covalent organic frameworks and Nb2C MXene for photocatalytic H2O2 production

We have developed a novel S-scheme heterojunction photocatalyst for the photocatalytic production of hydrogen peroxide (H₂O₂) via a two-electron (2e⁻) oxygen reduction reaction. This S-scheme heterojunction Tph-Dha-COF@Nb₂C was fabricated via the in-situ solvothermal growth of Tph-Dha-COF nanostructures on amino-functionalized Nb₂C MXene nanoflakes (Nb₂C-NH₂). The integration of Nb₂C significantly extended the visible light absorption of Tph-Dha-COF into the near-infrared region for photocatalytic H₂O₂ production. The Tph-Dha-COF@Nb₂C composite demonstrated efficient charge separation, rapid electron transfer, and enhanced oxygen adsorption. Consequently, the Tph-Dha-COF@Nb₂C heterojunction exhibited a high H₂O₂ production rate of 1833 μmol g^‒1 h^‒1 without sacrificial agents. In-situ Fourier transformed infrared spectroscopy and density functional theory calculations revealed the photocatalytic H₂O₂ production mechanism. The generated H₂O₂ demonstrated enhanced antibacterial activity. This work presents the first application of Nb₂C in the photocatalytic synthesis of H₂O₂ and provides a novel strategy for constructing COF-based heterojunctions for photocatalytic H₂O₂ generation and wastewater treatment.