Atomic-level dynamic spacing engineering in COF-based electrocatalysts for urea synthesis in ultra-low and wide...

Electrocatalytic CO₂ and NO₃^- co-reduction synthesis of urea is of great significance for renewable energy storage and carbon cycling. At present, despite the excellent performance of diatomic catalysts, their preparation relies on trial-and-error synthesis, resulting in inaccurate active site structure and difficult to control metal spacing. In this study, 2,6-diformylphenol (DFP) and 1,8-dihydroxynaphthalene-2,7-dicarboxaldehyde (DHDA) were used as building blocks to construct two diatomic catalysts with a clear coordination environment and adjustable diatom spacing. Both of them achieved efficient urea synthesis at ultra-low potentials, and the urea yield of 2Cu-NiPc-DHDA-COF (containing Cu₂N₄O₄ sites) was as high as 54.3% at -0.1 V vs. reversible hydrogen electrode (RHE), and had wide potential window stability. The in-situ mechanism study showed that its excellence was derived from the optimal atomic spacing and dynamic adaptive properties of the Cu₂N₄O₄ site, which could regulate the adsorption of *CONH intermediates and promote electron transfer. This work highlights the unique advantages of covalent organic framework (COF) materials in accurately designing the local environment of bimetals and studying the structure-activity relationship.