Iron ions embedded in hexagonal mesoporous silica via a simple method: implementation in mild oxidation catalysis

Mesoporous silica monoliths containing dispersed Fe-III sites have been prepared following a direct and simple synthetic method. The iron-containing materials are able to catalyze the epoxidation of cyclooctene by H2O2 under mild conditions. Textural and spectrophotometric analyses reveal that, when the thermal treatment temperature of the materials increases (from 500 degrees C to 1000 degrees C), the pore diameter of the silica matrix decreases while the formation of small oxo-iron(III) clusters is promoted. Among the five materials obtained after treatment at 500, 700, 800, 900 or 1000 degrees C, the one prepared at 700 degrees C exhibits the best catalytic performances. This indicates that a compromise must be found between several parameters, such as the pore size (which decreases with calcination temperature) and the hydrophobicity of the channel surface (which is favored at higher temperature), for an optimal reactivity.