Quenching of singlet oxygen as a decisive role in the efficiency and stability of ligand-protected Au cluster for photocatalytic oxidation

Abstract

Atomically precise gold nanoclusters (Au NCs) exhibit immense potential in photo-catalysis, yet their application is often hampered by low efficiency and stability under oxidative turnover. Here, we posit that this issue stems from a destructive kinetic competition for the photogenerated singlet oxygen (¹O₂) by the nanocluster itself over the intended substrate, leading to irreversible catalyst degradation and diminished performance. To resolve this, we introduce a "Kinetic Shielding" strategy. By situating the reaction within a micellar medium, we engineer the local environment to kinetically prioritize the scavenging of ¹O₂ by the substrate and thereby suppressing parasitic attacks on the nanocluster. Exemplified by the selective oxidation of sulfides using the classic [Au₂₅(PET)₁₈]- catalyst, this strategy not only boosts the reaction conversion from a mere 11% in a conventional organic solvent (CH2Cl2) to 98% but, crucially, imparts exceptional stability and reusability to the catalyst. The power of this approach is further demonstrated by the successful conversion of challenging electron-deficient substrates. Kinetic and theoretical studies reveal that the micellar nano-reactor achieves this by simultaneously concentrating the substrates and providing a more favorable energetic landscape for the key reaction step. This work establishes "Kinetic Shielding" as a simple and generalizable strategy to resolve the long-standing efficiency-stability issue in metal cluster catalysis.