In Situ Construction of Bifunctional Nickel Phthalocyanine‐Based COF on Ga ³⁺ ‐doped SrTiO ₃ for Efficient Overall Water Splitting

Abstract Photocatalytic overall water splitting represents an ideal way to convert solar energy into renewable hydrogen energy. Herein, nickel phthalocyanine derivative coupled benzidine sulfone covalent organic framework (NiPc‐Bs COF) is designed and grown in situ on Ga ³⁺ ‐doped strontium titanate loaded with CoO _x (GSTO‐CoO _x ) for constructing a novel COF‐based heterojunction (NiPcBs/GSTO‐CoO _x ). After loading Rh@Cr ₂ O ₃ , the resultant heterojunction achieves excellent overall water splitting activity with H ₂ /O ₂ yields up to 427/213 µmol h ⁻¹ and an apparent quantum yield of 23.1% at 365 nm. This in situ growth strategy can construct a Z‐scheme heterojunction with tight NiPcBs/GSTO‐CoO _x interfacial contacts, and enable the COF component to perform dual functions of hydrogen evolution photocatalyst and interface charge transfer promoter, while the Rh/Cr ₂ O ₃ and CoO _x cocatalysts loaded optimize the kinetics of water redox reactions, thereby synergistically boosting the photocatalytic overall water splitting efficiency. These findings not only offer new insights for the design and construction of high‐efficiency COF‐based heterojunctions, but also reveal the synergistic mechanism between spatial charge separation and surface reaction kinetics to improve the photocatalytic overall water splitting activity.