We　report　the　facile　and　environmental-friendly　synthesis　of　an　efficient　carbon　nitride　photocatalyst　for　hydrogen　production　and　dyes　degradation　by　using　a　unique　supramolecular　assembly　with　an　element　gradient　as　the　reactant.　The　element　gradient　is　acquired　through　the　selective　removal　of　barbituric　acid　from　the　surface　of　a　supramolecular　assembly　that　comprises　barbituric　acid,　melamine,　and　cyanucric　acid,　using　hydrochloric　acid　as　a　surface　modifier.　The　tailored　design　of　the　supramolecular　aggregate　results　in　inner　and　outer　parts,　which　have　carbon-rich　and　carbon-poor　domains,　respectively.　Structural　and　optical　investigations　of　the　new　assemblies　reveal　that　the　hydrogen-chlorine　interaction　generates　a　carbon　gradient　through　the　starting　supramolecular　assembly　and　to　a　better　packing　and　structural　alignment　of　the　supramolecular　units.　Detailed　X-ray　photoelectron　spectroscopy　and　photophysical　studies　of　the　final　carbon　nitride-like　materials　after　calcination　at　550　°C　indicate　that　the　element　gradient　across　the　starting　precursor　directly　projects　on　the　final　carbon　nitride　chemical　and　element　composition,　as　well　as　on　its　optical　and　photocatalytic　properties.　The　spatial　arrangement　of　the　starting　monomers　leads　to　the　formation　of　a　unique　energy-level　structure　in　the　final　material,　which　is　intended　to　improve　the　efficiency　of　charge　separation　under　illumination　and,　thereby,　result　in　a　strong　enhancement　of　photocatalytic　activity　toward　a　high　hydrogen　production　and　fast　dyes　degradation.　This　work　provides　new　opportunities　for　the　rational　design　of　carbon　nitride　and　other　metal-free　materials　with　unique　and　controllable　chemical,　optical,　and　catalytic　properties　for　sustainable　energy-related　applications.　©　2017　American　Chemical　Society.