Single-catalyst operando photoluminescence spectroscopy of perovskite quantum-dot-driven photoredox reactions

Realizing the full potential of photocatalysis in synthetic organic chemistry demands detailed insight into its elemental reaction steps. For stochastic, rare and often nonuniform processes like charge transfer or photocatalyst deactivation, much information remains hidden in ensemble measurements. Methods with single-catalyst sensitivity are uniquely capable of uncovering such information; however, tracking individual catalysts under authentic reaction conditions remains challenging. Here, we present a single-catalyst operando photoluminescence spectroscopy technique for photoredox reactions catalyzed by lead halide perovskite quantum dots. The method achieves realistic reactant loadings and resolves particle-to-particle variations by directly probing individual catalysts, capturing signatures of charge transfer and catalyst degradation at the few-atom level. Case studies of synthetically relevant C-C coupling and C(sp 3 )-H bromination reactions help devising the mitigation strategies for catalyst degradation, while real-time monitoring of photocatalytic activities uncovers dormant states lasting several seconds. These results highlight the potential of addressing static and temporal heterogeneity in photocatalytic function to promote refined structure-property relationships.