H3PMo12O40　molecules　have　been　successfully　encapsulated　in　the　cavities　of　MIL-100(Fe)　via　a　facile　hydrothermal　method　(denoted　as　HPMo@MIL-100(Fe)).　A　series　of　characterization　has　corroborated　the　insertion　of　H3PMo12O40　within　the　cavities　of　MIL-100(Fe).　The　resulting　HPMo@MIL-100(Fe)　nanocomposites　have　exhibited　much　higher　photoactivity　than　the　original-MIL-100(Fe)　toward　the　photocatalytic　selective　oxidation　of　benzylic　alcohols　and　the　reduction　of　Cr(vi)　under　visible　light　irradiation　(λ　≥　420　nm).　The　higher　photoactivity　of　HPMo@MIL-100(Fe)　can　be　attributed　to　the　integrative　effect　of　enhanced　light　absorption　intensity　and　more　efficient　separation　of　photogenerated　electron-hole　pairs.　The　host　porous　structure　of　MIL-100(Fe)　can　achieve　a　uniform　composition　with　H3PMo12O40,　which　is　significantly　important　for　producing　highly　reactive　dispersed　H3PMo12O40　molecules　and　enhancing　the　photocatalytic　activity　of　HPMo@MIL-100(Fe)　nanocomposites.　And　the　immobilized　H3PMo12O40　molecules　are　more　convenient　for　recycling.　Importantly,　almost　no　Fe　and　Mo　ions　leach　from　the　MIL-100(Fe)　during　the　reaction,　which　verifies　the　photostability　of　the　HPMo@MIL-100(Fe).　In　addition,　possible　photocatalytic　redox　reaction　mechanisms　have　been　investigated.　©　2015　The　Royal　Society　of　Chemistry.