Two　ultrathin　ZnTi-LDH　nanosheets　with　different　thickness　(1.4　and　4.0　nm)　were　prepared　to　study　the　interplay　between　the　active　site　and　catalytic　performance　in　photocatalytic　synthesis　of　N-benzylideneanilline　via　a　tandem　reaction.　ZnTi-LDH　nanosheet　possesses　dual　isolated　active　sites　including　the　coordinatively　unsaturated　Ti　atoms　(Lewis　acid　sites)　and　the　H　atoms　of　OH　groups　(Brönsted　acid　sites),　achieving　the　activation　of　benzyl　alcohol　and　nitrobenzene　via　C–O···Ti　species　and　N–O···H–O　species,　respectively.　Photogenerated　holes　and　electrons　facilitate　the　oxidation　of　benzyl　alcohol　to　benzaldehyde　and　the　reduction　of　nitrobenzene　to　aniline,　respectively.　The　thinner　sample　possesses　more　active　sites,　facilitating　not　only　the　activation　of　reactants　but　also　the　separation　of　photogenerated　carriers.　Therefore,　a　thinner　ZnTi-LDH　nanosheet　shows　the　high　conversion　(100%)　and　the　high　selectivity　(96%).　Finally,　a　synergetic　photocatalytic　mechanism　connected　to　the　molecular　activation　is　illustrated　at　the　molecule　level.　©　2023　Dalian　Institute　of　Chemical　Physics,　the　Chinese　Academy　of　Sciences