Triadic σ-π Coordination Programs Cuδ+ Sites to Drive Sequential Dual-N Species C-N Coupling for Efficient Urea...

Electrocatalytic CO2/NO3- coreduction to urea through C-N coupling (EcnRR) offers a low-carbon route that couples carbon utilization with nitrate valorization. However, its efficiency is limited by poor spatiotemporal synchronization of C- and N-derived intermediates, site competition and local repulsion at single active sites, and insufficient control over the NO3- reduction reaction (NtrRR) hydrogenation. Here, we construct a series of secondary-coordination-tunable single-atom Cu-alkynyl-X sites in conjugated microporous polymers (Cu-X-CMPs, X = N, C, S), where X → Cu σ coordination and an alkynyl π channel work together through triadic σ-π coupling to electronically program low-valent Cu atomic sites (Cuδ+). Experiments and theory show that N-coordinated Cu stabilizes the Cuδ+ working state, enhances local interfacial polarization, and reorganizes the interfacial hydrogen-bond network. These effects improve proton-coupled electron transfer (PCET) compatibility and increase the synchronized local coverages of *CO and *NHx near the active site. More importantly, Cu-N-CMPs establishes a sequential dual-N-species C-N coupling pathway initiated by *NH and completed by *NH2, with *CONH identified as the key intermediate in the first coupling step. As a result, Cu-N-CMPs delivers a Cu-site-normalized TOF of 1321.2 h-1 at -0.6 VRHE. In the membrane electrode assembly (MEA) electrolyzer, it further delivers a urea formation rate of 92.8 mmol gcat.-1 h-1 with 77.6% FEurea and stable operation for 85 h. This work demonstrates that Cu site electronic programming can coordinate sequential dual-N species C-N coupling, providing a transferable atomic-site engineering strategy for complex multi-intermediate electrocatalysis.