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

A critical challenge in artificial photosynthesis is the limited availability of photocatalysts that effectively integrate active sites for both CO2 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 CO2-reducing NH2-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 gcat. -1h-1 with 99.7% selectivity under visible light irradiation, a performance 500 times greater than that of pristine NH2-UiO-66. Furthermore, in situ DRIFTS and theoretical calculations indicate that Zr-oxo clusters promote CO2 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.