Chiral Heterometallic Ag₄Cu₄ Nanocluster: Environment-Sensitive Phosphorescence and Efficient Electrocatalytic Nitrate Reduction to Ammonia

Abstract

We report an atomically precise chiral Ag4Cu4 nanocluster featuring a helically symmetric bitetrahedral core and a rigidified ligand shell enforced by intramolecular π–π stacking. Single-crystal structural analysis reveals that the π–π interaction acts as a supramolecular lock, suppressing non-radiative relaxation and enabling oxygen- and temperature-dependent room-temperature phosphorescence, with an absolute solid-state quantum yield of 8.37% and a lifetime of 16.27 μs. In addition, the heterometallic Ag–Cu core endows the cluster with electrocatalytic activity toward nitrate reduction to ammonia in neutral electrolyte, affording a maximum Faradaic efficiency of 78.9% at −0.89 V vs. RHE. Control experiments using catalyst-free and ligand-only electrodes produced only trace NH₃ in the presence of KNO₃, whereas no NH₃ was detected in nitrate-free electrolyte, confirming that the dominant catalytic activity originates from the Ag₄Cu₄ nanoclusters. This work demonstrates that atomically precise heterometallic clusters can serve as well-defined platforms for correlating molecular structure with photophysical and electrocatalytic properties.