Ionic Exchange of Metal−Organic Frameworks for Constructing Unsaturated Copper Single‐Atom Catalysts for Boosting Oxygen Reduction Reaction

Regulating the coordination environment of atomically dispersed catalysts is vital for catalytic reaction but still remains a challenge. Herein, an ionic exchange strategy is developed to fabricate atomically dispersed copper (Cu) catalysts with controllable coordination structure. In this process, the adsorbed Cu ions exchange with Zn nodes in ZIF‐8 under high temperature, resulting in the trapping of Cu atoms within the cavities of the metal?organic framework, and thus forming Cu single‐atom catalysts. More importantly, altering pyrolysis temperature can effectively control the structure of active metal center at atomic level. Specifically, higher treatment temperature (900 °C) leads to unsaturated Cu–nitrogen architecture (Cu? N₃ moieties) in atomically dispersed Cu catalysts. Electrochemical test indicates atomically dispersed Cu catalysts with Cu? N₃ moieties possess superior oxygen reduction reaction performance than that with higher Cu–nitrogen coordination number (Cu? N₄ moieties), with a higher half‐wave potential of 180 mV and the 10 times turnover frequency than that of CuN₄. Density functional theory calculation analysis further shows that the low N coordination number of Cu single‐atom catalysts (Cu? N₃) is favorable for the formation of O₂* intermediate, and thus boosts the oxygen reduction reaction.