Preparation, characterization, and unusual reactivity of Fe-MCM-41

A new preparation method for highly dispersed iron in mesoporous MCM-41 materials has been developed, employing a methanolic solution of iron(III) nitrate. In situ EXAFS and NO adsorption followed by IR spectroscopy suggest that the resulting iron is present mainly in the form of isolated cations bound to the internal surface of the purely siliceous host material. Interchange between the Fe(II)/Fe(III) redox pair is facile, depending on the way in which the material is treated. The preparation procedure not only generates these highly dispersed iron species but also results in the formation of methoxy groups strongly bound to the MCM-41. It is suggested that the iron cations are chemically bound through siloxane bridges at silanol nests within the porous framework of the MCM-41 material.