Regulating interaction with surface ligands on Au₂₅ nanoclusters by multivariate metal-organic framework hosts for...

While atomically precise metal nanoclusters (NCs) with unique structures and reactivity are very promising in catalysis, the spatial resistance caused by the surface ligands and structural instability poses significant challenges. In this work, Au₂₅(Cys)₁₈ NCs are encapsulated in multivariate metal-organic frameworks (MOFs) to afford Au₂₅@M-MOF-74 (M = Zn, Ni, Co, Mg). By the MOF confinement, the Au₂₅ NCs showcase highly enhanced activity and stability in the intramolecular cascade reaction of 2-nitrobenzonitrile. Notably, the interaction between the metal nodes in M-MOF-74 and Au₂₅(Cys)₁₈ is able to suppress the free vibration of the surface ligands on the Au₂₅ NCs and thereby improve the accessibility of Au sites; meanwhile, the stronger interactions lead to higher electron density and core expansion within Au₂₅(Cys)₁₈. As a result, the activity exhibits the trend of Au₂₅@Ni-MOF-74 > Au₂₅@Co-MOF-74 > Au₂₅@Zn-MOF-74 > Au₂₅@Mg-MOF-74, highlighting the crucial roles of microenvironment modulation around the Au₂₅ NCs by interaction between the surface ligands and MOF hosts.