One-Pot Sequential Coordination-Covalent Construction of Symmetry-Broken MN2O2 Catalytic Sites in Cobalt-Polyimide Polymers for Nitrate Electroreduction.

The metal-nitrogen chelated species, MN₄, have shown promise as efficient electrocatalysts for nitrate reduction, yet the symmetric arrangement of N atoms results in suboptimal adsorption affinity toward reaction substrates and intermediates. The current approaches to breaking the symmetry of MN₄ suffer from inaccuracy and inhomogeneity because of the lack of strategies stemming from molecular design aspects. Herein, we report the construction of symmetry-broken MN₂O₂ sites in coordination polymers via sequential coordination-covalent control in a one-pot reaction. The dehydrogenating coordination preferentially occurs prior to the covalent imide-formation reaction, allowing the two reactions to be completely separated to afford molecularly precise polymer electrocatalysts that feature near-unity coordination degree and monodispersed atomic MN₂O₂ species with lowered symmetry, facilitating efficient nitrate reduction. Our study provides a design rationale to integrate diverse coordination and covalent chemistries into coordination polymers for electrocatalysis.