The hydroxylation of benzene to phenol over heteropolyacid encapsulated in silica

• H5PMoV2O40 nH2O PMoV2 was encapsulated in silica with preserved Keggin-structured (PMoV2@SiO2).
• The PMoV2 found to be dispersed homogeneously in the silica coated with thin carbon film in PMoV2@SiO2.
• The PMoV2@SiO2 was highly active and selective for the hydroxylation of benzene.
• The PMoV2@SiO2 was heterogeneous and reusable.

The vanadium-substituted heteropoly acid (H5PMo10V2O40 nH2O) (PMoV2) was encapsulated in silica as an immobilized catalyst (PMoV2@SiO2) for the hydroxylation of benzene to phenol with H2O2. The PMoV2@SiO2 was prepared by the one-pot hydrolysis of tetraethyl orthosilicate (TEOS) with PMoV2 and Pluronic P123, and then the P123 was removed by pyrolysis at 500 °C to give PMoV2@SiO2. The PMoV2@SiO2 was found to be highly porous with micropores, mesopores and macropores, and the PMoV2@SiO2 was highly active and selective for the hydroxylation of benzene under mild conditions. Moreover, the catalyst can be reused at least 5 times without obvious deactivation.

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