Copper Nanoclusters with Atomic Precision as Organocatalysts

Atomically precise copper nanoclusters (Cu NCs) have emerged as a distinctive class of catalysts that bridge molecular complexes and conventional nanoparticles. Their well-defined nuclearity, discrete electronic structures, and tunable ligand environments enable direct structure–activity correlations that are inaccessible with traditional Cu catalysts. This review summarizes recent advances in the use of atomically precise Cu NCs as organocatalysts for a broad range of organic transformations, including cycloadditions, C–C and C–N coupling reactions, hydroboration, hydrogenation, oxidation, protosilylation, sulfonylation, and multicomponent reactions. Emphasis is placed on how subtle structural features—such as nuclearity, hydride content, ligand dynamics, surface defects, mixed-valence states, and exposed metal sites—govern catalytic activity, selectivity, and reaction mechanisms. Representative examples illustrate that Cu NCs can operate via radical or polar pathways, act as intrinsic photo- and redox catalysts, and exhibit single-site behavior in both homogeneous and heterogeneous systems. Overall, this review highlights key structure–activity relationships and outlines emerging design principles and future opportunities for developing efficient, sustainable, and earth-abundant Cu-based catalysts.