Titanate Nanotubes Confined Merger of Organic Photocatalysis and TEMPO Catalysis for Highly Selective Aerobic Oxidation of Sulfides
1D titanate (H2Ti3O7) nanotubes were prepared by hydrothermal method of treatment of TiO2 under 10 M NaOH and ensuing acid treatment. Here, it was discovered that H2Ti3O7 nanotubes can facilitate the merger of organic photocatalysis and TEMPO catalysis. Confined within H2Ti3O7 nanotubes, organic photocatalyst erythrosin B (ErB) could drive highly selective aerobic oxidation of sulfides under irradiation of green light-emitting diodes (LEDs), when 0.5 mol% of TEMPO was added as co-catalyst. The turnover number (TON) for selective aerobic oxidation of thioanisole in terms of ErB is 2352, which is hitherto the best record of TON. Apart from confining the successful merger of ErB photocatalysis and TEMPO catalysis, H2Ti3O7 nanotubes not only activate inert O2 to generate superoxide radical anion (O2•-), but also ensure high selectivity of sulfoxides with their protons. This work represents a crucial step forward in selective oxidation reactions by materials design of dye-semiconductor photocatalysis.