Characteristics of the Photocatalytic Oxidation of Methane into Methanol on V-Containing MCM-41 Catalysts

V-containing MCM-41 catalysts were prepared by a direct synthesis method under acidic and basic conditions and impregnation. Their photocatalytic reactivity was evaluated for the selective photocatalytic oxidation of methane with NO under UV irradiation at 295 K. Selective methanol formation was observed on V-MCM-41 prepared in acidic solution and imp-V/MCM-41, while only coupling reaction products were obtained on V-MCM-41 prepared in basic solution. The photocatalytic reactivity of the catalysts for the partial oxidation of methane was found to strongly depend on the local structure of the V-oxide species including the coordination and loading sites, i.e., the charge transfer excited states of the isolated tetrahedral V5+-oxide species supported on the catalyst surface act as the active sites for the selective photocatalytic oxidation of methane into methanol.