Biomimetic Ligand Engineering of Metal Nanoclusters for Synergizing Enzyme-like Catalysis and Electrocatalysis.

Abstract

Inorganic nanoparticles serve as robust nanozymes mimicking natural enzymes' catalytic activity and selectivity, yet their on-demand design is hindered by insufficient atom-level mechanistic insights. Herein, we develop a biomimetic ligand engineering approach to reproduce natural peroxidase (POD) catalytic environments on the surface of metal nanoparticles, boosting their POD-like activity. Using atomically precise Au₂₅(Cys)₁₈ (Cys = l-cystine) nanoclusters (NCs) as a model nanozyme, customized cysteine-proline (CP), cysteine-histidine (CH), and cysteine-arginine (CR) dipeptides are anchored on their surfaces via stepwise ligand exchange. Combined absorption spectroscopy, nuclear magnetic spectroscopy, and mass spectrometry examinations evidence the spatial proximity of CP, CH, and CR on the surface of resultant Au₂₅(Cys/CP/CH/CR)₁₈ NCs, mimicking the catalytic microenvironment of horseradish peroxidase. Thereby, Au₂₅(Cys/CP/CH/CR)₁₈ NCs exhibit significantly enhanced POD-like catalytic activity, which stems from improved H₂O₂ adsorption affinity and reduced energy barrier for their conversion to the OOH species. The ligand engineering process concurrently boosts the electrocatalytic oxygen reduction reaction (ORR) activity and selectivity of Au₂₅ NCs toward H₂O₂. Synergizing the ORR and POD-like catalytic activities of Au₂₅(Cys/CP/CH/CR)₁₈ NCs enables direct ^•OH generation from O₂ for the efficient removal of organic pollutants and bacteria from waters. This work provides a facile nanozyme customization method while revealing atom-level ligand effects on enzyme-mimetic behaviors.