Hybrid mesoporous molecular sieve material based on lacunary polyoxometalate, K₈SiW₁₁O₃₉•12H₂O, was prepared via sol-gel method as well as block copolymer templating technique. The as-obtained SiW₁₁/SBA-15 composites were characterized by FT-IR, UV/DRS, XRD, ICP-AES, N₂ adsorption-desorption and TEM. The results indicate that not only a hexagonal-like packing of channels with homogeneous pore diameter is maintained in the hybrid materials, but also Keggin units remain perfectly with a content of ～25% and are grafted onto the pore wall of mesoporous silica by covalent linkage. The immobilization degree of polyoxometalate was measured in water at 25 ℃ and compared with those of the samples prepared by impregnation. It is shown that the lost percent of polyoxometalate in the hybrid material is much less than those of the impregnated samples.

Key words: polyoxometalate, lacunary Keggin anion, SBA-15, mesoporous molecular sieve