In Situ Synthesis of Copper-Based Metal–Organic Frameworks with Ligand Defects for Electrochemical Reduction of CO₂ into C₂ Products

Electrochemical reduction of CO₂ into high-value-added products is a potential approach to solving environmental problems but is limited by poor product selectivity and low efficiency. Metal-organic framework (MOF) materials have been considered one of the most promising catalysts, but their application is limited by complicated preparation processes, especially during the synthesis of organic ligands. In this work, a new three-dimensional Cu-MOF (<b>JXUST-301</b>) with high porosity was constructed based on the naphthalene diimide (NDI) ligand. Furthermore, <b>JXUST-301</b> with ligand defects (<b>JXUST-301D</b>) originating from the missing NDI unit was synthesized via an <i>in situ</i> reaction. The presence of ligand defects endows <b>JXUST-301D</b> with a better CO₂RR performance with a FE_C2 of 56.7% and a <i>j</i>_C2 of -162.4 mA cm^-2. Mechanistic studies revealed that the hierarchical pore structure and amino sites are created from the absence of the NDI unit, which promotes the exposure of catalytically active sites and CO₂ enrichment. Furthermore, the electronic structure of the Cu sites is modulated to upshift the d-band center, facilitating chemical adsorption and activation of key reaction intermediates. This work provides new insight into the <i>in situ</i> preparation of efficient Cu-MOF catalysts by introducing defects for the CO₂RR.