De‐Saturation of Single‐Atom Copper Catalysts for Accelerating Propargylic Substitution Reactions

Rational design of proximal coordination microenvironments surrounding catalytic sites to achieve optimal reaction kinetics represents a paramount pursuit in single‐atom catalysts (SACs), yet continues to pose substantial synthetic challenges. Developing innovative strategies that simultaneously stabilize low‐coordinated single‐metal species on solid supports, while ensuring atomic precision and high activity, remains imperative. Herein, a de‐saturation strategy for SACs is demonstrated (denoted as De‐sat SACs) using a top‐down approach based on a KOH‐mediated Joule thermal shock to obtain under‐coordinated and asymmetric SACs for efficient organic synthesis. Using copper‐based SACs as a proof‐of‐concept, the de‐saturation strategy effectively converts the CuN 4 to CuN 3 configuration. The De‐sat Cu SACs exhibit remarkable catalytic activity in propargylic substitution reactions, tolerating a broad range of nucleophiles (N–, C–, and O–), as well as diverse aryl, alkyl, tertiary, and cyclic propargylic carbonates. The coordination reduction in these De‐sat SACs not only breaks the structural symmetry to enhance site accessibility but also elevates the energy of the orbital of Cu atom, thereby facilitating the formation of copper–alkynyl intermediates and boosting their catalytic performance. These findings establish a new platform for the rational design and synthesis of de‐saturated yet stable SACs, facilitating challenging catalytic transformations toward sustainable chemical manufacturing.