Synthesis of nanostructured mesoporous silica materials containing manganese

The nanostructured mesoporous silica MCM-41 materials with different amounts of manganese have been synthesized under basic conditions at room temperature. The characteristics of the Mn-containing mesoporous samples were investigated by XRD, FTIR, N₂ adsorption, ²⁹Si MAS NMR and HREM techniques. It has been shown that the (100) peak intensity of XRD patterns became weakened and the specific surface area of materials decreased monotonously with the increase of Mn contents. FTIR results indicated that Mn ions could be incorporated into the Si-O framework and lead to the vibration of Si-O-Mn bond. ²⁹Si MAS NMR results suggested that the values of [SiO₄] tetrahedra in the framework decreased with the increase of Mn ions addition, resulting in the decrease of Q₄/Q₃ ratio. It could be seen from HREM images that nanostructured framework of Mn-modified mesoporous silica was distorted, and lamellar structure co-existed with hexagonal structure in some area.