Rational Design of Co(II)-Pyridine-Decorated Reduced Phosphomolybdate Photocatalysts for Efficient Aniline Oxidation under Mild Conditions

The conversion of aniline to nitrosobenzene (NSB), a key step in the synthesis of important chemicals, demands the development of environmentally friendly photocatalysts that operate under mild conditions. This process is driven by the need for sustainable methods, given toxic nature of aniline and its central role in the production of dyes, pharmaceuticals, and agricultural chemicals. This study reports on the synthesis of three reduced phosphomolybdate compounds with Co(II) centers and polypyridine ligands, which show great potential as photocatalysts for the mild oxidation of aniline to NSB. The synthesis uses 30% H₂O₂ as the oxidant and the compounds as the sole catalysts, achieving high conversion rates and selectivity without additional additives or photosensitizers. The integration of multidentate ligands with {P₄Mo₆} clusters significantly reduces the band gap, facilitating visible-light-driven photocatalysis. The adsorption interaction between coordinated water molecules and Co ions and H₂O₂ is found to enhance the conversion rate of aniline, a finding supported by DFT analyses.