Synergistic Interaction Between N‐Heterocyclic Carbene (NHC)‐Anchored Cu(I) Atom and In Situ‐Generated Cu Nanoparticles in a Post‐Modified MOF‐808 Framework Promoting C─C Coupling in CO ₂ Reduction

The electrochemical reduction of CO 2 to high‐value chemicals like C 2 H 4 represents a promising route for sustainable energy and CO 2 mitigation. However, its efficiency remains constrained by the high energy barrier for C─C bond formation and the competing hydrogen evolution reaction (HER). Herein, we report a synergistic catalyst for electrochemical CO 2 reduction reaction (eCO 2 RR), which comprises an N‐heterocyclic carbene (NHC)‐anchored Cu(I) atom and in situ electrogenerated Cu nanoparticles in a MOF‐808 framework. The catalyst exhibits outstanding performance in a neutral electrolyte, achieving a high Faradaic efficiency (FE) of 61.0% for C 2 H 4 and 79.5% for total C 2+ products. Experimental and theoretical studies reveal a dual role of the NHC ligand in eCO 2 RR: (i) promoting proton transfer and *CO hydrogenation via a robust hydrogen‐bonding network with interfacial water and (ii) stabilizing key intermediates such as *CHO and *COCHO through its strong electron‐donating ability. The synergy between a molecular NHC‐Cu(I) atom and adjacent Cu nanoparticles in a tailored microenvironment suppresses HER and lowers the energy barrier for asymmetric C─C coupling. This work offers a strategic design concept for constructing molecular‐nanostructured synergistic active sites in metal‐organic frameworks (MOFs) to advance electrocatalytic CO 2 conversion.