A new hybrid organic-inorganic material has been obtained by the incorporation of a manganese(m) porphyrin into a mesoporous aerogel matrix. The new heterogeneous catalyst was active in the epoxidation of a variety of olefins and polycyclic aromatic hydrocarbons, using iodosylbenzene as oxidizing agent. The catalyst was stable, readily recovered, and re-used without loss of activity. The hybrid aerogel catalyst was more active than the corresponding metalloporphyrin in homogeneous solution.