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

Abstract 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.