C-H Chalcogenation by a Bromide Rich and Environmentally Benign Orthorhombic CsPbBr3 under Visible Light, Polar Media and Aerobic Condition

The stability of CsPbBr3 nanocrystals (NCs) in open air remains challenging and can vary depending on the specific material and conditions. Generally, perovskites are prone to degradation due to oxygen, moisture, polar solvent, and light exposure. In this work, we have aimed to develop strategies to improve the stability of CsPbBr3 perovskite and broaden its potential applications in organic synthesis. An orthorhombic CsPbBr3 perovskite nano-crystal (NC) obtained from bromide precursor dibromoisocyanuric acid, can work efficiently as a visible light photocatalyst (blue LED, 5 mol % and TON ~ 18.11) under O2 atmosphere and in acetonitrile (dielectric constant ε ~ 37.5). The synthesis of diaryl sulfides and a diaryl selenide were achieved via template-free C-H functionalization of electron-rich arenes. The electron-rich arenes also helped to enhance the stability of the CsPbBr3 perovskites photocatalyst within the reaction system. The orthorhombic and bromide-rich CsPbBr3 NC displayed superior photocatalytic activity than cubic CsPbBr3 NCs and was found to be environmentally benign. After the reaction, only 32 ppb of Pb(II) was leached out (ICP-OES analysis) which is quite lower than the maximum permissible limit for drinking water of humans (50 ppb).