CsPbBr₃ in the Activation of the C–Br Bond of CBrX₃ (X = Cl, Br) under Sunlight

A newly synthesized green-fluorescent, orthorhombic, bromide-rich, perovskite nanocrystal (Φ ∼ 0.93, τ ∼ 12.5 ns, E_ox = +1.6 V) obtained from an unprecedented bromide precursor dibromoisocyanuric acid was found to be an excellent visible-light (sunlight or blue-light-emitting diode (LED)) photocatalyst toward the synthesis of gem-dihaloenones for the first time. The photoactivated CsPbBr₃ catalyzed the homolytic cleavage of CBrX₃ (X = Cl, Br) to generate the ^•CX₃ radical, which underwent cascaded C–C cross-coupling with terminal alkynes into the corresponding gem-dihaloenones. Radical-trapping experiments and luminescence-quenching studies helped establish a single-electron-transfer (SET) mechanism. Interestingly, other highly stable CsPbBr₃ NCs, obtained from N-bromosuccinimide (NBS) and dibromohydantoin (DBHT) precursors, are unable to carry out these transformations. These results not only enrich the CsPbBr₃ synthetic methodology but also encourage the research community to develop efficient and cost-effective photocatalytic materials.