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 Mn²⁺-doped (CdS)₁₃ MSCs (denoted as Mn²⁺:(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 Mn²⁺:(ZnxCd1-xS)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.