Here,　we　show　for　the　first　time　that　the　photocatalytic　activity　of　covalent　triazine-based　frameworks　(CTFs)　can　be　efficiently　improved　using　a　facile　sulfur-doping　approach.　The　sulfur-doped　CTFs　show　superior　photocatalytic　activity　and　stability　in　hydrogen　evolution　from　water　under　visible　light　irradiation　over　pristine　CTFs　and　g-C3N4.　The　significantly　improved　catalytic　efficiency　was　attributed　to　sulfur-doping　in　the　frameworks,　which　results　in　enhanced　adsorption　of　visible　light,　reduced　recombination　of　free　charge　carriers,　and　rapid　separation　and　transportation　of　photogenerated　electron-holes.　©　2016　The　Royal　Society　of　Chemistry.