The　diverse　nature　of　organic　precursors　offers　a　versatile　platform　for　precisely　tailoring　the　electronic　properties　of　semiconducting　polymers.　In　this　study,　three　fully　conjugated　sp2　carbon-linked　polymers　have　been　designed　and　synthesized　for　photocatalytic　hydrogen　evolution　under　visible-light　illumination,　by　copolymerizing　different　C3-symmetric　aromatic　aldehydes　as　knots　with　the　1,4-phenylene　diacetonitrile　(PDAN)　linker　through　a　C=C　condensation　reaction.　The　hydrogen　evolution　(HER)　is　achieved　at　a　maximum　rate　of　30.2　mmol　g−1　h−1　over　a　polymer　based　on　2,4,6-triphenyl-1,3,5-triazine　units　linked　by　cyano-substituted　phenylene,　with　an　apparent　quantum　yield　(AQY)　of　7.20　%　at　420　nm.　Increasing　the　degree　of　conjugation　and　planarity　not　only　extends　visible-light　absorption,　but　also　stabilizes　the　fully　conjugated　sp2-carbon-linked　donor–acceptor　(D–A)　polymer.　Incorporating　additional　electron-withdrawing　triazine　units　into　the　D–A　polymer　to　form　multiple　electron　donors　and　acceptors　can　greatly　promote　exciton　separation　and　charge　transfer,　thus　significantly　enhancing　the　photocatalytic　activity.　©　2019　Wiley-VCH　Verlag　GmbH　&　Co.　KGaA,　Weinheim