Carbon　nitride　nanosheets　have　shown　a　great　promise　for　photocatalytic　water　splitting　among　numerous　photocatalysts　due　to　the　versatile　advantages.　The　crucial　issues　of　the　weak　visible-light　absorption　and　the　separation　of　photo-generated　carrier　remain　a　matter　of　serious　concern.　Herein,　we　report　a　facile　calcination-solvothermal-calcination　method　to　prepare　nitrogen-deficient　carbon　nitride　nanosheets　(DCNS)　for　the　first　time,　which　leads　to　the　simultaneous　introduction　of　nitrogen　defects　and　formation　of　a　fragmented　few-layer　nanosheet　structure.　The　fragmented　few-layer　nanosheet　structure　is　known　to　possess　a　high　specific　surface　area　and　abundant　interfacial　reaction　sites,　contributing　to　the　rapid　consumption　of　photo-generated　carrier.　The　nitrogen　defects　are　responsible　for　further　boosting　the　photocatalytic　performance　by　regulating　the　band　structure　and　optical　properties　as　well　as　improving　the　separation　efficiency　of　photo-generated　carrier.　The　optimized　DCNS-120　delivers　a　superior　H2　production　rate　of　5375　μmol·g−1·h−1,　considerably　higher　than　that　of　bulk　carbon　nitride　(164　μmol·g−1·h−1).　We　anticipate　that　this　work　may　pave　a　new　pathway　to　engineering　carbon　nitride　with　a　matched　structure　to　achieve　the　desired　efficient　photocatalytic　H2　production　under　visible-light　irradiation.　©　2020　Elsevier　B.V.