Devices capable of the solar-driven splitting of water into molecular oxygen and hydrogen offer the potential of an unlimited renewable fuel. Such devices would need to combine a photoanode, where light driven water oxidation occurs, with a cathode, where protons are reduced to hydrogen. There is general consensus that one of the most challenging barriers to the generation of renewable energy from water is the oxygen-evolving half reaction. We have developed a bioinspired molecular catalyst comprised of a cubical [Mn4O4]7+ core which when suspended within the aqueous nanosized pores of a proton-conducting Nafion-membrane sustains the light driven oxidation of water for several days, with little loss in activity. Further, we have coupled the Mn water oxidation catalyst to a dye sensitizer and have shown that this assembly achieves light driven water oxidation without the application of a bias.