In Situ Reconstruction of Bimetallic MOFs to Form Copper-Cobalt Relay Catalysis for Efficient Nitrate Reduction to Ammonia

The electrochemical nitrate reduction reaction (eNO₃RR) is hindered by poor selectivity and sluggish kinetics due to competing hydrogen evolution and complex multi-electron/proton transfers. Here, a bimetallic CuCo-MOF （Metal-Organic Framework） is reported catalyst that undergoes in situ electrochemical reconstruction to form copper nanoparticles embedded within a cobalt-MOF matrix, establishing spatially coupled active sites for tandem catalysis. Mechanistic investigations reveal that the in situ-generated Cu nanoparticles selectively catalyze the nitrate-to-nitrite conversion, while the adjacent cobalt sites in the MOF framework facilitate water dissociation to provide reactive hydrogen species (*H) for subsequent nitrite hydrogenation to ammonia. The confined MOF architecture ensures efficient intermediate transfer, effectively preventing nitrite accumulation. This unique relay catalysis mechanism enables the reconstructed CuCo-DHTA catalyst to achieve remarkable NO₃RR performance, including a Faradaic efficiency exceeding 95% across a wide potential window (−0.8 to −1.0 V vs RHE) and a record-high ammonia production rate of 20.02 mg h⁻¹ cm⁻², surpassing state-of-the-art MOF-based catalysts. The pre-catalyst's reconstruction strategy in this work provides a flexible design for high-performance nitrate reduction catalysts.