Synthesis of Mesoporous Aluminosilicates with Low Si/Al Ratios under Acidic Conditions with a Single-Source Molecular Precursor

A key scientific objective has been the synthesis of mesoporous materials with higher amount of tetrahedral Al in the mesoporous framework since the discovery of ordered mesoporous materials, because the tetrahedral coordinated trivalent aluminum atoms are usually the major interaction sites for guest molecules and responsible for the generation of the acidity. It is difficult to incorporate the large amount of aluminum ions to the framework and to control the structural and morphological properties of the synthesized materials at the same time. In the present work, a single source molecular precursor ((sec-BuO)2AlOSi(OEt)3) together with tetramethyl orthosilicate (TMOS) was used for the synthesis of mesoporous aluminumsilicate with Si/Al ratios in the range of 1 to 10 under acidic conditions templated with P123. It is found that the aluminum can be stoichiometrically incorporated into the framework of mesoporous silicates with most of the aluminum in tetrahedral coordination by using the single-source molecular precursors. The results of powder X-ray diffraction (XRD), N2 sorption isotherms and Transmission electron microscopy (TEM) show that the material synthesized with [(sec-BuO)2AlOSi(OEt)3] as precursor exhibits wormhole-like pore structure, while the materials synthesized by co-condensation of aluminumsilicon ester and TMOS have ordered hexagonal mesoporous structures. The acidity characterizations show that the aluminosilicate materials have a large amount of medium acidic sites