Two photocatalytic systems consisting of spatially organized electron donor/photosensitizer/oxide semiconductor/catalyst assemblies are described. The first consists of an aluminosilicate zeolite (mordenite or zeolite L) containing Pt clusters, methylviologen, and titanium oxide within the linear channels, together with a size-excluded photosensitizer RuL3
2+ (L = 4, 4-dicarboxy-2, 2-bipyridine) adsorbed at the TiO2 surface. The kinetics of photochemical charge separation and hydrogen evolution in the presence of sacrificial electron donors are reported. In the second system, a layered oxide semiconductor, K4−xHxNb6O17·nH2O, replaces the zeolite/TiO2/MV2+ composite. Using adsorbed RuL3 and visible light excitation, this material decomposes acidic iodide solutions into H2 and I3
− with a quantum efficiency of 0.3 %.