Mesoporous ferrosilicates with high content of isolated iron species synthesized in mild buffer solution and their catalytic application

The mesoporous ferrosilicates with high content of framework iron species have been synthesized under mild acidic conditions (pH 4.4, buffer solution) by co-condensation of iron acetylacetonate and a mixture of tetraethoxysilane (TEOS) and sodium silicate using block copolymer Pluronic P123 as the template. The XRD, N2 sorption and TEM results show that the materials have well-ordered, two-dimensional, hexagonal mesoporous structure with uniform large pore. The higher amount of iron species incorporated in the mesoporous framework could be attributed to the mild acidic conditions and a better match of the hydrolysis rates of silica source and iron source during the synthesis under such conditions. The results of UV–vis diffuse reflectance spectra, UV resonance Raman spectra and EPR spectra show that tetrahedral iron species incorporated in the mesoporous framework of the materials are predominant. The mesoporous ferrosilicates can efficiently catalyze the hydroxylation of phenol in water using H2O2 as an oxidant. The framework iron species are found to be more active than the extra-framework iron oxide oligomer in the hydroxylation of phenol.