Aerogel　structures　have　attracted　increasing　research　interest　in　energy　storage　and　conversion　owing　to　their　unique　structural　features,　and　a　variety　of　materials　have　been　engineered　into　aerogels,　including　carbon-based　materials,　metal　oxides,　linear　polymers　and　even　metal　chalcogenides.　However,　manufacture　of　aerogels　from　nitride-based　materials,　particularly　the　emerging　light-weight　carbon　nitride　(CN)　semiconductors　is　rarely　reported.　Here,　we　develop　a　facile　method　based　on　self-assembly　to　produce　self-supported　CN　aerogels,　without　using　any　cross-linking　agents.　The　combination　of　large　surface　area,　incorporated　functional　groups　and　three-dimensional　(3D)　network　structure,　endows　the　resulting　freestanding　aerogels　with　high　photocatalytic　activity　for　hydrogen　evolution　and　H2O2　production　under　visible　light　irradiation.　This　work　presents　a　simple　colloid　chemistry　strategy　to　construct　3D　CN　aerogel　networks　that　shows　great　potential　for　solar-to-chemical　energy　conversion　by　artificial　photosynthesis.　©　2017　Wiley-VCH　Verlag　GmbH　&　Co.　KGaA,　Weinheim