Superacidic mesoporous silica materials containing embedded heteropolyacids (HPAs) were synthesized by sol-gel method in acidic media. In these materials, HPAs were immobilized into the silica structure covalently. The most acidic materials were obtained at the use of Pluronic P123 as a non-ionic pore-forming agent. Ionic surfactants also formed mesoporous structures, however, their interaction with HPA reduced acidity of the products. Obtained materials were tested as heterogeneous catalysts in liquid-phase alkylation of 1,3,5-trimethylbenzene by 1-decene. The most effective catalyst demonstrated higher conversion of starting substances to long-chain isomeric alkylbenzenes as compared to the activity of zeolite HY, a well-known alkylation catalyst. No leaching of HPA from silica gel was observed after the alkylation. [GRAPHICS] .