Phosphorus‐Doped Single Atom Copper Catalyst as a Redox Mediator in the Cathodic Reduction of Quinazolinones

The use of clean electric energy to activate inert compounds has garnered significant attention. Homogeneous redox mediators (RMs) in organic electrosynthesis are effective platforms for this purpose. However, understanding the RM's electronic structure under operational conditions, electron transport processes at the electrode surface, and substrate adsorption‐desorption dynamics remains challenging. Here, we synthesized a Cu single‐atom catalyst (SAC, named Cu‐N‐P@NC) with a CuN3P1 micro‐coordination structure, employing it as a unique cathode redox mediator. Introducing phosphine atoms into the coordination system allowed modulation of the SAC's electronic metal‐support interaction, optimizing catalyst‐substrate adsorption‐desorption dynamics and accelerating electrochemical reactions. Utilizing the heterogeneous SAC strategy, we achieved a novel electro‐reduction coupling ring‐opening reaction of inert quinazolinone frameworks. The Cu‐SAC exhibited exceptionally high catalytic activity and substrate compatibility, operating smoothly at gram‐scale production. Additionally, we applied the SAC to modify 11 natural product molecules. Integrating micro‐coordination environment regulation and theoretical adsorption models elucidated the significant influence of electrode‐RMs‐substrate interactions on reaction kinetics and catalytic efficiency‐a feat challenging for homogeneous RMs. This approach offers a novel pathway for advancing efficient organic electrosynthesis reactions and provides critical insights for mechanistic studies.