Periodic mesoporous organosilicas functionalized with iron(iii) complexes: preparation, characterization and catalysis on direct hydroxylation of benzene to phenol

Abstract

Three reusable, recoverable, iron(III) complexes incorporating periodic mesoporous organosilica PMO-Fe₁–PMO-Fe₃ were prepared. The composition, morphology, and textural properties with ordered mesoporous channel structure of the prepared materials were characterized by FT-IR, ICP, TGA, BET, SEM and TEM. Their catalytic performances were tested in the direct hydroxylation of benzene to phenol in liquid phase using H₂O₂ as oxidant. As expected, the incorporation of active-iron-centers within hydrophobic periodic mesoporous organosilica prevents over-oxidation of the designed phenol and hence significantly improves the selectivity of phenol with nearly two-folds compared with their corresponding homogeneous iron precursors Fe₁–Fe₃. In addition, these heterogeneous catalysts can be recovered and reused for at least four times without any significant loss of catalytic activity and selectivity.