Ultrasmall CsPbBr₃ Nanocrystals as a Recyclable Heterogeneous Photocatalyst in 100% E- and Anti-Markovnikov Sulfinylsulfonation of Terminal Alkynes

The precise synthesis of ultrasmall, monodisperse CsPbBr₃ nanocrystals is crucial due to their enhanced photophysical properties resulting from strong quantum confinement effects. Traditional methods struggle with size control, complicating synthesis. Although CsPbBr₃ nanocrystals find applications in LEDs and photovoltaics, their use in photocatalysis for organic reactions remains limited. Our study introduces ultrasmall TBIA-CsPbBr₃ nanocrystals (∼5.6 nm), synthesized via a three-precursor hot injection method using tribromoisocyanuric acid (TBIA) as a bromine precursor for the first time. These nanocrystals exhibit a near-unity photoluminescence quantum yield (PLQY) of 0.99 and an elevated oxidation potential of +1.80 V. We demonstrate their efficacy as recyclable heterogeneous photocatalysts in a one-pot, 100% E-selective, anti-Markovnikov sulfinylsulfonation of terminal alkynes under visible light, achieving a high product conversion rate (PCR) of 62,500 μmol g^–1 h^–1 and recyclability for up to five cycles. Density functional theory (DFT) calculations support the exclusive formation of the E-isomer. TBIA-CsPbBr₃ outperforms other CsPbBr₃ perovskites in photocatalysis, with superior efficiency attributed to their extended excited-state lifetime and higher surface area, which accelerates the organic transformation process.