Surface organic phosphates enhance mild oxidation of toluene by O2 to benzaldehyde over VTiOx/γ-Al2O3

The direct oxidation of toluene by O 2 to benzaldehyde with high efficiency is a bright route for the green production of benzaldehyde but still a significant challenge. In this study, we develop a ligand modification strategy by bonding organophosphonic acid (OPA) to VTiO x /γ-Al 2 O 3 to restructure its interface microenvironment for enhancement of toluene oxidation to benzaldehyde. The as-prepared catalyst exhibits excellent selectivity over 99 % under mild conditions. Results of comprehensive characterizations and calculations reveal that the OPA bonding in bidentate with the V 6-coordinated species causes noticeable phase reconstruction between VO x and TiO 2 , thereby generating nearby new reactive oxygen species, which is responsible for the conversion of toluene to benzaldehyde at temperatures as low as ∼50 °C, much lower than that over VO x /TiO 2 (>130°C). The interface microdomain around the bonding site of OPA helps to significantly weaken the methyl C H bond of toluene molecule in reaction manifested as the significant decrease in apparent activation energy. Hence, the current work reveals a novel mechanism of the typical catalyst VO x /TiO 2 under OPA bonding, which is useful to solve the classic difficult reaction of toluene to benzaldehyde by O 2 oxidation.