Epoxy resins were polymerised using molybdenum ethoxide and 2-ethylhexanoate as polymerisation initiators. The thermosets thus obtained are useful epoxidation catalysts for a variety of alkenes, including propene with tert-butyl hydroperoxide as an oxidant. To investigate the long-term performance of these resins, they were used repeatedly in up to 120 reactions without any reconditioning. Compared with other catalyst systems based on organic polymers, they reveal unprecedented long-term activities over periods of months so that catalyst lifetimes of years can be expected. Di-, tri-, tetra- and oligofunctional epoxy resin monomers were used and compared. The catalytic performance of the thermosets strongly depends on the resin type and the polymerisation initiator. Promising results were obtained with monomers bearing 3 or 4 glycidyl groups in combination with Mo(OEt)(5) as an initiator. Metal leaching, determined by sensitive atomic spectroscopic techniques, is extremely low. Inorganic-organic hybrid catalysts can be easily prepared by adding inorganic components such as silicagel to the liquid resins, followed by polymerisation. (c) 2006 Elsevier Inc. All rights reserved.