Chem. Mater. 1998, 10, 467-470

Synthesis of Ordered Microporous Silicates with Organosulfur Surface Groups and their Applications as Solid Acid Catalysts

Myong H. Lim, Christopher F. Blanford, and Andreas Stein*

<>Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, MN 55455-0431

Mercaptopropyl-functionalized porous silicates were synthesized by the co-condensation of mercaptopropyltriethoxysilane (MPTS) and tetramethoxysilane (TMOS) in the presence of a cationic surfactant under basic conditions. Ordered hexagonal arrays of channels, similar to those of MCM-41 mesoporous sieves but with smaller pore diameters, were obtained with MPTS:TMOS ratios as high as 1:2.5 and a thiol content up to 5 mmol S/g silica. The extracted solids were microporous, with an average pore diameter of ca. 14 Å, a surface area of 792 m2/g and a total pore volume of 0.47 cm3/g. The surface thiol groups were demonstrated to be efficient absorbers of heavy metals, such as mercury ions. Furthermore, it was possible to oxidize the supported thiol groups to sulfonic acid groups, thus creating a solid acid ion exchanger or catalyst. The sulfonic-acid functionalized material was found to be an efficient heterogeneous catalyst for the protection of alcohols by tetrahydropyranylation.