Copper nanoclusters with atomic precision as catalyst for organic reactions

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.