V substituted phosphomolybdic acids could hydroxylate benzene with nearly 100% selectivity at appreciable conversion levels in the presence of oxidizing agents like H2O2 and AcOOH. There appears to be a correlation, for the liq. phase, between phenol yield and its rate of formation with V content in the phosphomolybdic acid. Unfortunately, these materials do not show the same activity in gas-phase with N2O as oxidant. Therefore, the high acidity of these solids is not involved in the reaction pathway. [on SciFinder (R)]