High-Density Palladium Single-Atom Catalysts for Photoinduced Tandem Decarbonylation/Carbonylative Reductive Coupling

In carbonylation reactions, a carbonyl source is typically required, often supplied by carbon monoxide (CO) gas or CO surrogates that release CO via decarbonylation. Herein, we report a novel carbonylative reductive coupling reaction utilizing pivaldehyde as a facile and cost-effective carbonyl source with water serving as an environmentally benign reductant. A polymeric carbon nitride semiconductor functionalized with high-density single-atom palladium was designed as a multifunctional catalytic system, simultaneously driving a cascade decarbonylation-CO migration-carbonylative coupling process while enabling photocatalytic water oxidation to supply electrons for the reductive coupling. Life cycle assessment analysis further supports the economic viability of our carbonylative reductive coupling strategy. The spatial proximity of Pd atoms is crucial in promoting efficient CO migration, and computational studies offer atomic-level insights into this high-density configuration in the reaction. The heterogeneous single-atom photocatalyst exhibits exceptional stability, maintaining its catalytic activity over 10 consecutive cycles with minimal loss in performance. The practical utility of this method was demonstrated through the efficient synthesis of pharmaceutical compounds, including a decagram-scale synthesis of AdipoRon in a high-speed circulation flow system. This work seamlessly integrates decarbonylation, photocatalytic water splitting, and reductive coupling reactions, underscoring the tremendous potential of single-atom photocatalysts in advancing sustainable cascade organic transformations.