Assembling polydopamine on TiO2 for visible light photocatalytic selective oxidation of sulfides with aerial O2

The selective aerobic oxygenation of organic sulfides under mild conditions represents one of the most important chemical transformations because of a wide variety of applications of sulfoxides. However, this reaction is very challenging to be implemented by conventional semiconductor photocatalysis. Herein, polydopamine (PDA) could be easily assembled onto TiO2 semiconductor to afford visible light absorbing TiO2@PDA with a large pi-conjugated system of PDA. Subsequently, TiO2@PDA was used to implement aerobic oxidation reaction in CH3OH, relying on the improved stability of PDA due to a large 7C-conjugated system. Irradiated by 460 nm blue light LEDs, PDA could efficiently transfer electrons to the conduction band of anatase TiO2 which can activate aerial O-2. Subsequently, visible light-promoted selective aerobic oxidation of sulfides into corresponding sulfoxides with the cooperation of 2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) on TiO2@PDA have been achieved eventually. This work suggests that the promise of assembling a large pi-conjugated system on a semiconductor in establishing visible light photocatalytic selective chemical transformations.