Accelerated Water Oxidation Kinetics Triggered by Supramolecular Porphyrin Nanosheet for Robust Visible-Light-Driven CO 2 Reduction.

Water oxidation is one of the most challenging steps in CO 2 photoreduction, but its influence on CO 2 photoreduction is still poorly understood. Herein, the concept of accelerating the water oxidation kinetics to promote the CO 2 photoreduction is realized by incorporating supramolecular porphyrin nanosheets (NS) into the C 3 N 4 catalyst. As a prototype, porphyrin-C 3 N 4 based van der Waals heterojunctions with efficient charge separation are elaborately designed, in which the porphyrin and C 3 N 4 NS serve as the water oxidation booster and CO 2 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 CO 2 reduction with a maximum CO evolution rate of 16.8 µmol g -1 h -1 , which is 6.8 times that of the C 3 N 4 NS and reaches the current state of the art for C 3 N 4 -based materials in CO 2 photoreduction. Overall, this work throws light that accelerating water oxidation kinetics can effectively improve the CO 2 photoreduction efficiency.