Electrocatalysis for C–N coupling reactions (EcnRR) plays a crucial role in the synthesis of various organic molecules. However, the C–N coupling process is inherently complex and kinetically sluggish. Single atom catalysts (SACs), with their high atomic efficiency, tunable structures, and remarkable catalytic activity, exhibit exceptional performance and hold great promise for C–N coupling reactions. The design of SACs requires a deep understanding of the reaction mechanisms, particularly the dynamic evolution of multi-component reactions. This necessitates systematic studies of multi-species coupling mechanisms to move beyond traditional trial-and-error approaches. This review elucidates the activation mechanisms of carbon- and nitrogen-containing molecules, providing fundamental insights into the SACs-mediated electrocatalytic C–N coupling process. Notably, the core focus lies in proposing novel design principles for SACs systems tailored for C–N coupling, based on theoretical frameworks and experimental findings. These insights not only guide the improvement of existing methodologies but also offer transformative pathways for electrocatalytic organic nitrogenation via C–N coupling chemistry, potentially reshaping the landscape of organic synthesis. Looking ahead, a comprehensive understanding of the structure–activity relationships in SAC design will be key to advancing this rapidly evolving field.

Organic conjugated polymers have received extensive attention due to their unique electronic properties. However, there have been relatively few reports on the dark photocatalytic reactions utilizing organic conjugated polymers. Herein, we report the successful synthesis of an organic conjugated polymer based on poly (heptazine imide) nanocrystals (CNNCs) for H₂O₂ evolution and biomedical applications using a simple salt molten method and sonication–centrifugation process. The results show that these colloid CNNCs have the characteristics of photogenerated electrons accumulation and realize dark photocatalysis with high reducibility under visible light irradiation. Notably, these accumulating photogenerated electrons can reduce O₂ in darkness to produce H₂O₂. In addition, cytotoxicity tests were conducted and it was found that H₂O₂ produced under dark conditions could oxidize L-arginine (L-Arg) to NO, which effectively killed tumors in the dark. This work provides an important strategy to construct organic conjugated semiconductor nanocrystals and applying them to future energy and biomedical fields.