Visible light-driven efficient palladium catalyst turnover in oxidative transformations within confined frameworks

Pd(II) catalyst turnover by reoxidation of a low valent Pd species is the key step for a Pd(II) catalyzed oxidation reaction. Here, the authors report a new strategy to address Pd reoxidation by fabricating spatially proximate photocatalyst and Pd(II) catalyst into metal-organic framework. Palladium catalyst turnover by reoxidation of a low-valent Pd species dominates the proceeding of an efficient oxidative transformation, but the state-of-the-art catalysis approaches still have great challenges from the perspectives of high efficiency, atom-economy and environmental-friendliness. Herein, we report a new strategy for addressing Pd reoxidation problem by the fabrication of spatially proximate Ir-III photocatalyst and Pd-II catalyst into metal-organic framework (MOF), affording MOFs based Pd/photoredox catalysts UiO-67-Ir-PdX2 (X = OAc, TFA), which are systematically evaluated using three representative Pd-catalyzed oxidation reactions. Owing to the stabilization of single-site Pd and Ir catalysts by MOFs framework as well as the proximity of them favoring fast electron transfer, UiO-67-Ir-PdX2, under visible light, exhibits up to 25 times of Pd catalyst turnover number than the existing catalysis systems. Mechanism investigations theoretically corroborate the capability of MOFs based Pd/photoredox catalysis to regulate the competitive processes of Pd-0 aggregation and reoxidation in Pd-catalyzed oxidation reactions.