A　series　of　Al3+-doped　UiO-66(Ce)　MOFs　(U(CexAl1−x))　was　developed　to　reveal　the　roles　of　metal　doping　on　active　site　formation　and　substrate　activation　in　photocatalytic　selective　transformation　of　amines　to　imines.　Al3+　doping　induced　crystal　structure　distortion　to　form　coordinately　unsaturated　metal　(Al,　Ce)　sites　as　Lewis　acid　sites　to　chemisorb　and　activate　benzylamine　(BA).　In　situ　FTIR　revealed　that　the　Al　site　with　stronger　acid　strength　facilitated　BA　activation.　The　activation　degree　of　N–H　bonds　in　BA　was　evaluated　by　changes　of　calculated　force　constant.　The　intermediate　products　were　confirmed　through　time-dependent　in　situ　FTIR.　The　Al3+-doped　sample　U(Ce0.90Al0.10),　the　optimal　catalyst,　showed　a　significantly　increased　BA　conversion　(97.6　%)　than　that　(47.5　%)　of　undoped　sample,　which　was　attributed　to　enough　active　sites　and　the　optimal　charge　mobility.　Finally,　the　present　study　proposes　a　synergistic　photocatalytic　mechanism　associated　with　molecular　activation　to　demonstrate　selective　oxidation　pathways　at　the　molecular　level.　©　2024　Elsevier　Inc.