Surface Modification via Click Chemistry Enhances CO ₂ Reduction Selectivity between C ₂₊ /C ₁ on Shape‐Controlled Cu ₂ O

Molecular fabrication of metal surfaces has potential to harness diverse surface processes, such as CO 2 electrolysis on copper. CO 2 reduction is influenced not only by the local environment of the active copper atom but also by the surface atomic order, surface dynamics under electrode polarization, and mass transport. CO 2 reduction on two types of Cu 2 O‐derived Cu metal, modified with chemically identical organic layers, is studied. Surface click chemistry enables uniform modification, precisely replicating the surface morphologies of 2D‐packed and dispersed nanocubic Cu 2 O. In both types of catalysts, the modification affects CO 2 reduction, but with markedly different selectivity. On 2D‐packed Cu 2 O, the modified organic layer forms two distinct functional domains, one promoting proton reduction and the other facilitating CO adsorption, on a continuous copper surface. These domains cooperatively promote the formation of C 2+ products. In modified nanocubic Cu 2 O, where a limited number of copper atoms are enclosed in the organic layer shell, the crystal regularity of reduced Cu is disrupted significantly inhibiting CC bond formation. Assisted by proton transport through organic layer, this surface instead selectively produces methane. These results highlight the multifunctional effects of molecular modification, which creates distinct yet cooperative domains and induces surface atom restructuring.