A　novel　organic　semiconductor　photocatalyst　mimicking　natural　light-harvesting　antenna　complexes　in　photosynthetic　organisms,　a　disulfide　(-S-S-)　bridged　C3N3S3　polymer,　was　designed　and　developed　to　generate　hydrogen　from　water　under　visible　light　irradiation.　The　artificial　conjugated　polymer　shows　high　H2-producing　activity　from　the　half-reaction　of　water　splitting　without　the　aid　of　a　sacrificial　electron　donor.　The　H2-producing　efficiency　and　photo-stability　of　the　catalyst　could　be　improved　greatly　using　Ru　and　single-wall　carbon　nanotubes　as　cocatalysts　or　by　adding　a　sacrificial　donor.　The　results　represent　a　potential　and　prospective　application　of　the　C3N3S　3　polymer　in　solar　energy　conversion　and　offer　significant　guidance　to　develop　more　stable　and　efficient　photocatalytic　systems　based　on　organic　semiconductors.　©　The　Royal　Society　of　Chemistry　2011.