Coupling Electron Transfer and Redox Site in Boranil Covalent Organic Framework Toward Boosting Photocatalytic Water Oxidation

Abstract

AbstractThe efficient polymeric semiconducting photocatalyst for solar‐driven sluggish kinetics with multielectron transfer oxygen evolution has spurred scientific interest. However, existing photocatalysts limited by π‐conjugations, visible‐light harvest, and charge transfer often compromise the O2 production rate. Herein, we introduced an alternative strategy involving a boranil functionalized‐based fully π‐conjugated ordered donor and acceptor (D–A) covalent organic frameworks (Ni‐TAPP‐COF‐BF2) photocatalyst. The co‐catalyst‐free Ni‐TAPP‐COF‐BF2 exhibits an excellent ~11‐fold photocatalytic water oxidation rate, reaching 1404 μmol g−1 h−1 under visible light irradiation compared to pristine Ni‐TAPP‐COF (123 μmol g−1 h−1) alone and surpasses to reported organic frameworks counterpart. Both experimental and theoretical results demonstrate that the push/pull mechanism (metalloporphyrin/BF2) is responsible for the appropriate light‐harvesting properties and extending π‐conjugation through chelating BF2 moieties. This strategy benefits in narrowing band structure, improving photo‐induced charge separation, and prolonged charge recombination. Further, the lower spin magnetic moment of M‐TAPP‐COF‐BF2 and the closer d‐band center of metal sites toward the Fermi level lead to a lower energy barrier for *O intermediate. Reveal the potential of the functionalization strategy and opens up an alternative approach for engineering future photocatalysts in energy conversion applications.