In　this　paper,　two　types　of　conjugated,　triazine-based　covalent　organic　frameworks　(COFs)　with　different　connected　linkages　(imine　bond　and　sp2-carbon-CN　bond)　are　presented.　The　insignificant　difference　in　the　linkages　creates　a　remarkable　difference　in　their　performance　in　visible-light-driven　hydrogen　generation.　The　fully　π-conjugated　two-dimensional　(2D)　COF　with　sp2-carbon-CN　linkages　showed　an　external　quantum　efficiency　of　13.48%　at　450　nm,　which　is　an　unprecedented　result　for　COF　photocatalysts.　In　contrast,　the　imine-linked　2D　COF　displayed　almost　no　photoactivity.　Further　photoelectrochemical　and　quantum　chemical　studies　provide　an　in-depth　understanding　of　the　catalytic　mechanism.　This　finding　provides　new　insight　into　preparing　high-performance　organic　photocatalysts　for　solar　energy　conversion.　[Figure　not　available:　see　fulltext.].　©　2023,　Science　China　Press.