Efficient and Durable Photochemical CO ₂ Reduction by TiO ₂ ‐Immobilized Metal Porphyrin Catalysts

The advancement of molecular catalysts featuring 3d metals provides a sustainable alternative to noble‐metal‐based systems for CO 2 ‐to‐C1 fuel conversion; however, their widespread application remains limited by modest activity and selectivity. Herein, we report a dye‐sensitized ternary hybrid photocatalyst composed of a visible‐light‐absorbing Ir(III) complex, a TiO 2 electron mediator, and a covalently anchored porphyrin catalyst incorporating 3 d metals (Fe, Co, Ni, and Cu). Immobilization of the porphyrin via carboxylate groups enables strong electronic coupling with the TiO 2 scaffold, facilitating efficient multielectron accumulation and directional charge transfer. Under visible‐light irradiation, the TiO 2 ‐immobilized porphyrins ( M‐TCPP ; M = Fe, Co, and Ni) exhibit markedly enhanced CO 2 ‐to‐CO conversion performance with turnover numbers exceeding 3000, surpassing their homogeneous analogs. Notably, Cu‐TCPP shows distinct reactivity, favoring H 2 evolution over CO formation. Electrochemical analysis reveals a metal‐dependent mechanistic divergence, in which Cu‐TCPP undergoes protonation to form a Cu–H intermediate, whereas Fe‐, Co‐, and Ni‐based porphyrins proceed through conventional M–COOH pathways. These findings highlight the synergistic role of TiO 2 in tuning interfacial electron transfer and promoting efficient CO 2 reduction using earth‐abundant molecular catalysts.