Designing Molecular Reactor of Interlayer Dual-Atom Toward Urea Electrosynthesis

Electrocatalytic C─N coupling offers a sustainable alternative to energy-intensive industrial processes for urea synthesis. Herein, we design conjugated polymer-based molecular reactors featuring interlayer diatomic Cu-N₄ sites and precisely tunable spacings (4.0, 4.6, and 5.7 Å) to optimize CO₂ and nitrate coupling. The 4.0 Å-spaced copper polyphthalocyanine (CuPPc-4.0) delivers a remarkable urea yield rate of 460.0 mmol h^-1 g^-1 with 26.1% Faradaic efficiency at -1.3 V (versus RHE), outperforming wider-spaced analogs. The optimal 4.0 Å cavity spatially confines reactants and intermediates, matching urea's molecular dimensions (3.5 Å), thereby enhancing C-N coupling and urea synthesis activity, while the layered AA stacking structure stabilizes unbonded diatomic Cu configurations, preventing aggregation and ensuring durability. Mechanistic studies reveal that while ball-milling treatment increases single-atom exposure, it disrupts the layered architecture and eliminates interlayer diatomic sites, reducing activity by about 50%. This work demonstrates a multidimensional catalyst design integrating atomic precision and molecular confinement for sustainable electrosynthesis.