Sequential-chain coupling over hierarchical click-sites enables highly selective urea electrosynthesis

Electrochemical C - N coupling is an appealing approach for sustainable urea synthesis, while it is technically challenging due to the complex reaction mechanism and the spatiotemporal mismatch between C- and N- intermediates. Here, inspired by click chemistry, we design a hierarchical click-site catalyst (Se-InO_x) that enables an efficient sequential-chain coupling pathway for urea electrosynthesis, achieving a urea yield rate of 254.94 mmol h^-1 g^-1, Faradaic efficiency of 78.61%, >85% N_urea-selectivity and 100% C_urea-selectivity. Mechanistic studies reveal that Se-InO_x as the first click-site can selectively adsorb NO₃^- and hydrogenate it to stable *NO₂, while inhibiting CO₂ adsorption at this stage. The surface-anchored *NO₂ then acts as the second click-site to click couple with CO₂, forming the key *CO₂NO₂ intermediate. This sequential-chain coupling strategy effectively resolves the spatiotemporal mismatch between N- and C- intermediates, thereby maximizing the suppression of side-reactions and enhancing C - N coupling selectivity. Techno-economic analysis and scalable synthesis validate the feasibility of this approach, providing a blueprint for high-selectivity multicomponent electrosynthesis.