Membrane-free selective oxidation of thioethers with water over a nickel phosphide nanocube electrode

Developing a membrane-free oxidation reaction, especially using water as the oxygen source, to generate high-value chemicals with high selectivity for replacing low-value O-2 over a cost-effective catalyst is significant. In this study, nickel phosphide (Ni2P) hollow nano-cubes are designed and shown to enable membrane-free selective oxidation of thioethers to sulfoxides and sulfones with H2O. In situ Raman data reveal the surface reconstruction of Ni2P to NiOOH, and the resulting Ni-II/Ni-III redox couple promotes this transformation. The O-18-labeling experiments confirm H2O as the oxygen source. A cross-coupling of the sulfur-related radical with the hydroxyl radical is proposed. Sulfoxides and sulfones with high yields and selectivity can be controlled via potential modulation, which is challenging for traditional methods. Deuterated sulfoxides and sulfones are readily synthesized via one-pot thioether oxidation and the tandem H/D exchange processes. Wide substrate scopes, good functional group compatibilities, integrating hydrogen production, and paired synthesis of deuterated sulfoxide and arene highlight the potential of this membrane-free strategy.

Automated summary

The study developed a membrane-free oxidation reaction using nickel phosphide hollow nano-cubes as catalyst, enabling selective oxidation of thioethers to sulfoxides and sulfones with water as the oxygen source. In situ Raman data showed surface reconstruction of Ni2P to NiOOH, promoting the transformation via Ni-II/Ni-III redox couple. O-18-labeling experiments confirmed water as the source of oxygen, with a proposed cross-coupling mechanism of sulfur and hydroxyl radicals.