Ligand-Free MgCO₃ Nanoclusters Catalyze Nucleophilic Alcohol Addition Reactions

Subnano and nanometric metal clusters are ultrasmall aggregates in which most atoms are exposed on the surface, directly interacting with reactants and enabling highly efficient catalysis. However, metal carbonate clusters have been barely prepared and used in catalysis. Here, we report the synthesis of ultrasmall, ligand-free MgCO₃ clusters formed via CO₂ capture with MgCl₂, with an average composition of [MgCO₃]₅·3H₂O. These clusters exhibit catalytic activity in various nucleophilic alcohol addition reactions, showing a 5-fold enhancement compared to bulk MgCO₃ and CaCO₃-triethylamine clusters. These results pave the way for synthesis of ultrasmall alkaline metal carbonate clusters beyond Ca, which can be employed as efficient catalysts in organic synthesis.