A Dual Purpose Strategy to Endow Gold Nanoclusters with Both Catalysis Activity and Water Solubility

Gold nanoclusters have attracted extensive interest for catalysis applications in recent years due to their ultrasmall sizes and well-defined compositions and structures. However, at least two challenges exist in this emerging field. First, the steric hindrance of the ligands inhibits the catalysis activity, and second, the mechanism underlying water-phase catalysis using gold nanoclusters is often ambiguous. Herein, we introduce a "kill two birds with one stone" strategy to address these two challenges via the use of host-guest chemistry. As an illustration, a novel adamantanethiolate-protected Au₄₀(S-Adm)₂₂ nanocluster was synthesized, bound with γ-CD-MOF, and then transferred to the HRP-mimicking reaction system. The as-obtained catalyst exhibits excellent water solubility and catalytical activity, totally different from the virgin Au₄₀(S-Adm)₂₂ nanoclusters. Further, the detailed HRP-mimicking catalysis mechanism was proposed and supported by DFT calculation. Another interesting finding is the unique structure of Au₄₀(S-Adm)₂₂, which can be regarded as an Au₁₃ icosahedron unit derived structure but different from the widely reported icosahedron contained nanocluster where the Au₁₃ icosahedrons are often centered. These novel, intriguing results have important implication for the property tuning and practical application of metal nanoclusters in the future.