Supported photooxidation catalysts containing a metal oxide or metal ion as catalyst which is fixed to the support by means of carboxylate moieties are an alternative to existing such catalysts, particularly if low cost supports such as organic polymers, particularly polyethylene, are used. The supported photocatalysts can be used in mineralisation of organic pollutants in both liquids and gases and show reduced leaching of the catalyst and good resistance towards reactive oxygen species generated during the degradation process.