Mn ²⁺ -Doped and Alloyed (CdS) ₁₃ Magic-Sized Clusters as Molecular Building Blocks for Bright Self-Assembled Photocatalytic Nanostructures

Magic-sized clusters (MSCs) represent the missing molecular link between precursors and colloidal semiconductor nanocrystals; yet their synthetic fragility and limited compositional scope have hindered systematic exploration. Stoichiometric MSCs with precise metal–chalcogen parity are particularly elusive, restricting access to well-defined families and their emergent functions. Here, we report the synthesis of Mn 2+ -doped (CdS) 13 MSCs (denoted as Mn 2+:(CdS) 13 ) and their directed self-assembly into suprastructures (SSs) featuring a distinct nanohexagonal morphology. Comprehensive optical spectroscopic and mass spectrometric analyses confirm that the MSCs retain their atomically precise (CdS) 13 frameworks within the SSs. The ordered assembly markedly enhances orange photoluminescence, yielding quantum efficiencies up to 57% through the reduction of surface defect states. Extending this strategy, we synthesize SSs based on alloy Mn 2+:(Zn x Cd 1– x S) 13 clusters, enabling atomic-level control of composition. These cluster-assembled materials serve as highly active photocatalysts for solar-driven hydrogen evolution, with alloyed systems reaching rates of ∼100 mmol g –1 h –1 and exhibiting up to 3.5-fold enhancement over unalloyed analogues due to atomic-level synergistic effects. This work establishes a general platform for generating doped and alloyed stoichiometric MSCs and demonstrates how the hierarchical assembly of atomically precise clusters can unlock emergent photophysical and catalytic properties.