Stabilization of Ligand‐Free Small Gold Nanocluster Within a Metal–Organic Framework for Enhanced Hydrogen Evolution and Horseradish Peroxidase‐Mimicking Catalysis in Aqueous Media

ABSTRACT Atom‐precise metal nanoclusters (NCs) have garnered considerable attention due to their photoluminescence and catalytic properties arising from the quantum confinement effect and metal‐ligand interaction. However, the tendency of NCs to aggregate under reaction conditions hinders their catalytic activity. Surface‐protecting ligands can enhance the stability, but they often reduce surface exposure and, consequently, catalytic activity. The incorporation of surface‐cleaned clusters into the pores of metal–organic framework (MOF) is highly desirable. Here, we constructed a hybrid structure in which Zr‐based MOF, UiO‐66‐NH ₂ , is grown directly on the surface of the [Au ₉ (PPh ₃ ) ₈ ](NO ₃ ) ₃ cluster. During the nanocluster‐templated growth of MOF, the triphenylphosphine ligand was removed, yielding a surface‐clean gold cluster‐MOF composite material. An integrated experimental‐theoretical analysis revealed that the ligand‐free Au clusters occupy the pores of the MOF framework. This composite exhibited an overpotential of 65 mV and demonstrated a high chronopotentiometric stability in the hydrogen evolution reaction (HER). For the horseradish peroxidase (HRP)‐mimicking reaction, the Michaelis–Menten constants (K _m ) for H ₂ O ₂ and TMB were determined to be 0.1 and 2.7 m m , respectively. Experimental and computational studies demonstrated that the MOF‐induced confinement, coupled with NH ₂ group interactions within its pores, modulates catalyst–substrate interactions, thereby improving the catalytic performance and stability of the composite.