Bi2MoO6　hierarchical　microspheres　(BMO-SP)　consisting　of　monolayer　nanosheets　with　abundant　surface　oxygen　defects　and　unsaturated　Mo　sites　are　constructed　for　the　one-pot　synthesis　of　secondary　amine　via　a　photocatalytic　coupling　reaction　of　nitrobenzene　(NB)　and　benzyl　alcohol　(BA).　The　performance　of　this　photocatalyst　is　12　times　higher　than　that　of　bulk　Bi2MoO6　(BMO-bulk).　Experiment　results　and　density　functional　theory　calculations　reveal　that　surface　oxygen　defects　induce　more　unsaturated　Mo　atoms　facilitating　the　coordination　activation　of　NB　and　BA　molecules　through　the　formation　of　–N–O···Mo　and　–C–O···Mo　coordination,　respectively.　The　surface　oxygen　defects　also　promote　the　separation　of　photogenerated　carriers.　More　photogenerated　holes　transfer　to　the　surface　for　oxidizing　the　activated　BA　while　the　photogenerated　electrons　are　trapped　by　oxygen　defects　for　reducing　NB.　Thus,　the　photocatalytic　performance　is　markedly　improved.　This　work　successfully　designs　an　efficient　photocatalyst　for　the　tandem　reaction　via　surface　defect　engineering.　©　2023　Elsevier　Ltd