From Transient Fluctuations to Programmable Dynamics: Operando‐Reversible Reconstruction of Single‐Atom Sites

The dynamic nature of single‐atom catalysts, manifested as transient coordination fluctuations during individual molecular turnovers, has provided crucial mechanistic insights. However, the practical exploitation of such molecular‐level dynamics remains fundamentally challenging due to their experimental elusiveness and poor controllability. Here, we report a paradigm shift from these stochastic fluctuations to programmable coordination switching, enabled by the operando‐reversible reconstruction of single‐atom Cu sites in a Pt/bpy‐UiO‐CuX 2 model catalyst. Triggered by a reductive environment during hydrogenation, a metastable N 2 ‐Cu‐H configuration is generated under reducing conditions and remains the dominant Cu state during catalysis, before reversibly converting to an oxidized Cu‐(OH) 2 form after depletion of reducing species and air exposure. Meanwhile, the coordination anions can be reprogrammed through external acid/anion environments, enabling interconversion among Cl − , OH − , and sulfate‐containing Cu coordination states. Multimodal operando spectroscopy combined with theoretical calculations demonstrates that the N 2 ‐Cu‐H intermediate modulates the electronic state of the active Pt center, thereby boosting phenylacetylene‐to‐styrene selectivity by simultaneously lowering styrene desorption energy by 0.68 eV while raising the barrier for styrene hydrogenation by 0.66 eV. This work elevates dynamic single‐atom sites from stochastic structural fluctuations to programmable coordination switching, establishing a new paradigm for enzyme‐mimetic catalysts with adaptive responsiveness to redox and acid–base environments.