CuS-Cobalt Porphyrin Organic-Inorganic Heterojunction with a Long-Lived Charge-Separated State for Efficient CO₂-to-CH₄ Conversion under Infrared Light.

Abstract

Harnessing infrared (IR) light for the selective reduction of CO₂ remains a significant challenge due to sluggish kinetics and poor carrier dynamics. In this research, a novel organic-inorganic hybrid heterojunction was designed consisting of HKUST-1-derived CuS and cobalt porphyrin (CoTPPS), which achieves an exceptional CH₄ generation (178.02 µmol g^- ¹ h^- ¹) and 96.5% CH₄ selectivity under IR irradiation. Femtosecond transient absorption spectra and synchrotron radiation measurements show that strong interfacial electronic coupling enables a significant charge transfer, creating a robust internal electric field which greatly increases carrier lifetimes (170-fold). Density functional theory (DFT) calculations further elucidate how the heterojunction lowers the rate-determining *COOH formation barrier (from 1.43 to 1.07 eV) and stabilizes the critical *CHO intermediate. This effectively steers the eight-electron pathway towards CH₄ while suppressing CO desorption. The synergy between the porous MOFs-derived scaffold and the molecular active center provides a versatile paradigm for engineering IR-responsive photocatalysts with precise intermediate regulation. This work promotes the rational design of hybrid materials for efficient solar-to-fuel conversion.