Polymeric　carbon　nitride　(CN)　is　a　promising　material　for　photocatalytic　water　splitting.　However,　CN　in　its　pristine　form　tends　to　show　moderate　activity　due　to　fast　recombination　of　the　charge　carriers.　The　design　of　efficient　photocatalytic　system　is　therefore　highly　desired,　but　it　still　remains　a　great　challenge　in　chemistry.　In　this　work,　a　pyrene-based　polymer　able　to　serve　as　an　electron　donor　to　accelerate　the　interface　charge　carrier　transfer　of　CN　is　presented.　The　construction　of　donor-acceptor　(D–A)　heterojunction　was　confirmed　to　significantly　restrain　the　charge　recombination　and,　thus,　improve　the　proton　reduction　process.　This　study　provides　a　promising　strategy　to　achieve　solar　H2　production　in　an　efficient　and　low-cost　manner.　©　2019　Wiley-VCH　Verlag　GmbH　&　Co.　KGaA,　Weinheim