This paper discusses the design of different W and PW heterogeneous catalysts. The first part focuses on the electrostatic immobilization of those species on organic resins. Ln the second part, some new silica materials are synthesized as carrier materials for PW species. Both electrostatic immobilization and covalent linking of the species on the modified silica materials are discussed. Besides a thorough spectroscopic study (FT-IR, Raman, NMR, TGA and EPMA), the catalytic properties of the designed catalysts are evaluated for the epoxidation of a variety of bulky olefins. (C) 2000 Elsevier Science B.V. All rights reserved.