Rigidity-Flexibility Integrated Porous Coordination Polymers via Lattice-Confined Adaptive Evolution for Efficient Neutral Nitrate Reduction to Ammonia.

Adaptive catalytic systems hold significant potential for designing electrocatalysts with both high activity and stability. However, achieving a balance between structural robustness and dynamic adaptability remains challenging. Herein, we report a new design strategy for self-adaptive electrocatalysts for boosting the electrosynthesis of ammonia by integrating a rigid framework with flexible coordination bonds within a porous coordination polymer (PCP). A rigid-flexible coupling copper pyrazole-based PCP, referred to as Cu-pyNDI, is designed to function as a self-adaptive electrocatalyst that exhibits both structural robustness and dynamic adaptability. Operando x-ray absorption spectroscopy (XAS) reveals that during the reaction, the copper sites in Cu-pyNDI undergo reversible local structural restructuring, resulting in the formation of lower-valence Cu, which serves as potentially active species. Building on the operando XAS findings, we introduced iron doping into Cu-pyNDI to modulate the self-regulating behavior of copper by enhancing the formation of low-valence copper species with lower coordination numbers, which serve as potential active centers, thereby facilitating the generation of the *NO2 intermediate. Consequently, Fe0.25Cu0.75-pyNDI demonstrated improved electrocatalytic performance, achieving a Faradaic efficiency of 93% and an ammonia yield of 18847 µg h-1 mgcat -1 in neutral electrolytes, comparable to state-of-the-art electrocatalysts.