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

Abstract

Atomically precise gold nanoclusters (Au NCs) exhibit immense potential in photocatalysis, 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 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, 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 also, 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 nanoreactor 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.