De Novo Engineering High‐Density Proximal Copper Single Atoms for Enhanced C─C Coupling in CO 2 Electroreduction

Copper‐based single‐atom catalysts (SACs) are promising for the electrochemical CO 2 reduction reaction, yet their multicarbon production remains restricted by the inherent trade‐off among atomic loading, dispersion, and proximity required for efficient C─C coupling. In this study, we develop a de novo coordination‐site and geometry engineering strategy to construct high‐density proximal Cu SACs for improving CO 2 ‐to‐C 2+ electroreduction. Flexible molecular building blocks rich in N/O coordination motifs assemble into wrinkled 2D networks and further hierarchically organize into a 3D nanoflower framework, where isolated Cu sites with high loading of 14 wt% are anchored via robust N/O coordination. The structural bending brings adjacent Cu atoms into close proximity (∼2.6 Å). Competitive N/O coordination generates asymmetric and low‐coordinated microenvironments, promoting *CO intermediate stabilization and subsequent C─C coupling. The optimized catalyst achieves a C 2+ Faradaic efficiency of 81.34% at 500 mA·cm −2 , including 51% ethylene selectivity, with stable operation exceeding 100 h. This work sheds light on structural dimensional control and microenvironment engineering for promoting cooperative catalysis in single‐atom systems, offering new opportunities for efficient multicarbon electrosynthesis.