Developing electrochemical C–N coupling as a sustainable alternative to conventional thermochemical routes offers a promising pathway for converting environmentally relevant small molecules into nitrogen-containing, high-value chemicals. However, the efficiency of C–N bond formation is often limited by the lack of synchronization between carbon- and nitrogen-derived intermediates. Here, we introduce and validate spatiotemporal intermediate matching as a catalytic concept governing efficient C–N coupling. Guided by this concept, we design a functionally complementary, molecularly defined Co–Zn dual-site catalyst, featuring a subnanometer (∼1.1 nm) intersite distance to facilitate intermediate encounters and tailorable site ratios to balance their generation kinetics. In the CO2/NO3– coreduction system, the catalyst achieves near-theoretical stoichiometric coupling, leading to a 5-fold enhancement in the Faradaic efficiency for methylamine. Importantly, this concept can be extended to other C–N coupling systems, opening sustainable electrochemical routes toward higher-value amines such as dimethylamine and N-methylaniline. Our findings establish spatiotemporal intermediate matching as a guiding principle for C–N bond formation and offer a generalizable strategy for rational catalyst design toward sustainable chemical production.