The　photocatalytic　degradation　of　organic　compounds　in　airstreams　or　in　solution　was　studied　by　using　the　commercial　HZSM-5　as　photocatalyst.　It　was　found　that　the　commercial　HZSM-5　had　an　unanticipated　photocatalytic　activity　for　ethylene,　bromomethane　and　methyl　orange.　XRF　and　AAS　analysis　revealed　that　all　of　the　HZSM-5　samples　employed　contain　a　trace　amount　of　iron　species.　The　photocatalytic　activity　of　samples　was　proportional　to　the　content　of　iron.　The　primary　results　of　characterization　by　XRD,　DRS,　XPS　and　SPVS　suggested　that　the　most　of　Fe　existed　in　framework　of　zeolite　and　in　a　tetrahedral　coordination.　The　iron　species　might　be　excited　by　UV　irradiation　to　form　a　charge　transfer　excited　complex　along　with　the　ligands　and　an　electron　excited　state　of　Fe3+,　which　are　responsible　for　the　photocatalytic　behavior　of　zeolites.　(C)　2004　Elsevier　B.V.　All　rights　reserved.