An　efficient　metal-free　catalytic　system　has　been　developed　based　on　hexagonal　boron　carbon　nitride　(h-BCN)　nanosheets　for　the　dehydrogenation　of　N-heterocycles　with　visible　light;　hydrogen　gas　is　released　in　the　process,　and　thus　no　proton　acceptor　is　needed.　This　acceptorless　dehydrogenation　of　hydroquinolines,　hydroisoquinolines,　and　indolines　to　the　corresponding　aromatic　N-heterocycles　occurred　in　excellent　yield　under　visible-light　irradiation　at　ambient　temperature.　With　h-BCN　as　the　photocatalyst　and　water　as　the　solvent,　this　environmentally　benign　protocol　shows　broad　substitution　tolerance　and　high　efficiency.