Supramolecular　pre-assembly　by　design　is　an　effective　strategy　to　adapt　the　physicochemical　properties　of　polymeric　carbon　nitrides　(PCNs)　to　improve　their　solar　conversion　performance.　A　new　supramolecular　preorganization　protocol,　which　employs　H2O　as　the　self-assembly　medium　and　sodium　persulfate　as　a　modifier,　is　proposed　to　modulate　the　textural　and　photoelectronic　features　of　PCNs　for　efficient　visible-light　H2　evolution.　Sodium　persulfate　is　revealed　to　precisely　tailor　the　final　carbon　nitride　polymers　with　unusual　porous　layered　structures　and　promoted　charge　separation　and　migration　kinetics.　As　a　result,　the　modulated　PCNs　with　optimized　structures　show　a　greatly　enriched　activity　for　photocatalytic　H2　generation　compared　to　the　analogous　materials　derived　from　melamine　without　the　modifier.　©　2019　Wiley-VCH　Verlag　GmbH　&　Co.　KGaA,　Weinheim