Mononuclear Iron Pyridinethiolate Complex Promoted CO2 Photoreduction via Rapid Intramolecular Electron Transfer

An efficient single-component bifunctional iron molecular catalyst was designed and employed for visible-light-driven CO₂ reduction reaction without additional photosensitizers. This is the first example of using an earth-abundant metal as an active center for single-component catalytic system. Expectedly, it will provide new insights into photocatalytic CO₂ reduction using earth abundant metal-based mononuclear molecular catalysts.

Abstract

Designing earth-abundant metal complexes as efficient molecular photocatalysts for visible light-driven CO₂ reduction is a key challenge in artificial photosynthesis. Here, we demonstrated the first example of a mononuclear iron pyridine-thiolate complex that functions both as a photosensitizer and catalyst for CO₂ reduction. This single-component bifunctional molecular photocatalyst efficiently reduced CO₂ to formate and CO with a total turnover number (TON) of 46 and turnover frequency (TOF) of 11.5 h⁻¹ in 4 h under visible light irradiation. Notably, the quantum yield was determined to be 8.4 % for the generation of formate and CO at 400 nm. Quenching experiments indicate that high photocatalytic activity is mainly attributed to the rapid intramolecular quenching protocol. The mechanism investigation by DFT calculation and electrochemical studies revealed that the protonation of Febpy(pyS)₂ is indispensable step for photocatalytic CO₂ reduction.

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