Efficient and Durable Photochemical CO2 Reduction by TiO2-Immobilized Metal Porphyrin Catalysts

초록

The advancement of molecular catalysts featuring 3d metals provides a sustainable alternative to noble-metal-based systems for CO2-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 TiO2 electron mediator, and a covalently anchored porphyrin catalyst incorporating 3d metals (Fe, Co, Ni, and Cu). Immobilization of the porphyrin via carboxylate groups enables strong electronic coupling with the TiO2 scaffold, facilitating efficient multielectron accumulation and directional charge transfer. Under visible-light irradiation, the TiO2-immobilized porphyrins (M-TCPP; M = Fe, Co, and Ni) exhibit markedly enhanced CO2-to-CO conversion performance with turnover numbers exceeding 3000, surpassing their homogeneous analogs. Notably, Cu-TCPP shows distinct reactivity, favoring H2 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 TiO2 in tuning interfacial electron transfer and promoting efficient CO2 reduction using earth-abundant molecular catalysts. © 2026 The Author(s). ChemSusChem published by Wiley-VCH GmbH.

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