Effective photocatalytic systems are constructed by using a semiconducting and chelating pi-conjugated poly-(2,2’-bipyridine-5,5’-diyl) (PBpy) and Pt compounds. A photoreaction catalyzed by a mixture of PBpy and [Pt(bpy)(2)](NO3)(2) evolves H-2 corresponding to a large turnover number (H-2/[Pt(bpy)(2)](2+)) of 490 in an aqueous solution of NEt3. Colorimetry and X-ray fluorometry (EDX) analysis reveal that added [Pt(bpy)(2)](2+) releases one bpy ligand, and coordinatively unsaturated [Pt(bpy)](2+) thus formed is fixed on the surface of particles of PBpy. PBpy bearing the Pt(bpy) complex maintains its catalytic activity in repeated photocatalytic reactions. The PBpy catalyst is also active for photoevolution of H? from an aqueous solution containing disodium ethylenediaminetetraacetate as the sacrificial reagent. X-ray photoelectron spectroscopy analysis indicates that Pt fixed on PBpy is in an electronic state similar to that of Pt fixed by TiO2.