Accelerated Water Oxidation Kinetics Triggered by Supramolecular Porphyrin Nanosheet for Robust Visible‐Light‐Driven CO₂ Reduction

Abstract Water oxidation is one of the most challenging steps in CO₂ photoreduction, but its influence on CO₂ photoreduction is still poorly understood. Herein, the concept of accelerating the water oxidation kinetics to promote the CO₂ photoreduction is realized by incorporating supramolecular porphyrin nanosheets (NS) into the C₃N₄ catalyst. As a prototype, porphyrin‐C₃N₄ based van der Waals heterojunctions with efficient charge separation are elaborately designed, in which the porphyrin and C₃N₄ NS serve as the water oxidation booster and CO₂ reduction center, respectively. Theoretical calculations and relevant experiments demonstrate that the added porphyrin NS reverses the rate‐limiting step in the water oxidation while reducing its energy barrier, thus resulting in faster reaction kinetics. Therefore, the optimal sample shows excellent performance in visible‐light‐driven CO₂ reduction with a maximum CO evolution rate of 16.8 µmol g⁻¹ h⁻¹, which is 6.8 times that of the C₃N₄ NS and reaches the current state of the art for C₃N₄‐based materials in CO₂ photoreduction. Overall, this work throws light that accelerating water oxidation kinetics can effectively improve the CO₂ photoreduction efficiency.