Dynamic coordination flexibility unlocks efficient electrocatalytic nitrate reduction to ammonia over molecular cobalt catalysts

Electrocatalytic nitrate reduction to ammonia (NO₃RR) offers a sustainable and energy-efficient alternative to the Haber-Bosch process for green ammonia synthesis. Molecular catalysts have shown significant promise for NO₃RR owing to their tunable coordination environments and electronic structures. However, conventional molecular catalysts with rigid coordination configurations suffer from inherent structural immobility, which severely limits their ability to dynamically adapt to and activate diverse reaction intermediates. Herein, we designed a cobalt-based molecular catalyst featuring a flexible coordination structure capable of dynamic configuration adjustment during catalysis. In situ characterization and theoretical calculations reveal that the flexible Co site enables selective adaptation to various intermediate species, thereby enhancing their stabilization and activation—particularly promoting the *NO intermediate hydrogenation as the rate-determining step. Consequently, the catalyst achieves an outstanding ammonia yield rate of 1.57 mmol cm⁻² h⁻¹ with a near-unity faradaic efficiency of 99.3% at −0.7 V vs. RHE and facilitates gram-scale synthesis of ammonium chloride. This work establishes dynamic coordination flexibility as an effective strategy to overcome the intrinsic limitations of static molecular catalyst sites, providing new insights into the rational design of high-performance electrocatalysts for nitrogen cycle conversions.