Selective aerobic oxidation of sulfides by cooperative polyimide-titanium dioxide photocatalysis and triethylamine catalysis

Abstract

The selective aerobic oxidation of sulfides is highly attractive for modern organic and pharmaceutical synthesis. Thus, there is an urgent need for exploring new photocatalytic system on this reaction. In this work, we investigated the polyimide-titanium dioxide (Aeroxide P25 TiO₂, denoted as P25) photocatalyst in visible light-driven selective aerobic oxidation of sulfides. Polyimide-P25 shows enhanced absorption of visible light. Subsequently, this makes polyimide-P25 exhibits observable photocatalytic activity on visible light-driven selective aerobic oxidation of sulfides while pure polyimide and P25 individually have none. Aided by triethylamine (TEA), the yield of sulfoxide by polyimide-P25 photocatalysis reaches more than 3 folds compared to that without TEA, highlighting the remarkable cooperative effect between polyimide-P25 photocatalysis and TEA catalysis. Moreover, a plausible mechanism is figured out based on the quenching control experiments, kinetic studies and in-situ electron paramagnetic resonance (EPR) tests. This work could provide useful guidance for the rational design of hybrid photocatalysts to undertake challenging selective chemical transformations.

Keywords: Molecular oxygen; Photocatalysis; Polyimide-TiO(2); Sulfide; Triethylamine.