Metal-free　heterostructure　photocatalysts　composed　of　black　phosphorus　(BP)　and　polymeric　carbon　nitride　(CN)　are　successfully　synthesized　via　a　one-step　liquid　exfoliation　method　assisted　by　sonication.　The　combination　of　BP　with　CN　strengthens　the　visible-light　harvesting　ability,　facilitates　the　charge　separation　in　the　photocatalytic　process,　and　renders　promoted　activity　of　photoinduced　molecular　oxygen　activation,　such　as　superoxide　radicals　(·O2−)　evolution　and　H2O2　production.　This　work　highlights　that　coupling　semiconductors　with　well-matched　band　levels　provide　a　flexible　route　to　enhance　the　performance　of　photocatalysts　for　producing　reactive　oxygen　species,　and　gives　ideas　for　the　design　of　highly　active　and　metal-free　materials　toward　sustainable　solar-to-chemical　energy　conversion　and　environmental　remediation.　©　2018　WILEY-VCH　Verlag　GmbH　&　Co.　KGaA,　Weinheim