Dual Active Sites in a Single MOF: Achieving High‐Rate and Selective Photocatalytic CO ₂ Reduction to Formate With Concurrent Water Oxidation

Abstract

ABSTRACT A critical challenge in artificial photosynthesis is the limited availability of photocatalysts that effectively integrate active sites for both CO 2 reduction and water oxidation reactions. Herein, we first use defect engineering to integrate the ruthenium 2,2'‐bipyridine‐6,6'‐dicarboxylic acid Ru(bda) 3+ moiety, renowned for its photosensitivity and water‐oxidizing capabilities, into the CO 2 ‐reducing NH 2 ‐UiO‐66 framework, that is, d ‐MOF/Ru. The photoelectrochemical and in situ XPS measurements reveal that the Ru(bda) 3+ sites fulfill a dual function: enhance visible‐light absorption and promote charge separation, while simultaneously serving as active centers for water oxidation. Remarkably, enabled by the concurrent water oxidation activity at the Ru(bda) 3+ sites, the d ‐MOF/Ru generates HCOOH at a rate of 2157 µmol g cat. −1 h −1 with 99.7% selectivity under visible light irradiation, a performance 500 times greater than that of pristine NH 2 ‐UiO‐66. Furthermore, in situ DRIFTS and theoretical calculations indicate that Zr‐oxo clusters promote CO 2 reduction while Ru(bda) 3+ sites drive water oxidation in a synergistic cycle. This work presents a molecular‐level strategy for optimizing photocatalysts, offering new perspectives for improving the efficiency of artificial photosynthesis.