Photosynthesis is the basis for life on earth and involves the transformation of carbon dioxide to sugars with the help of sunlight. There is considerable interest in developing artificial photosynthetic assemblies, that can use sunlight to generate useful chemical compounds, e.g. generation of hydrogen and oxygen from water. Choice of molecules in this study include polypyridyl complex of  Ru as sensitizers and electron donors and bypyridinium-based systems as electron acceptors. The nanometer size cage and channels of aluminosilicate zeolite membranes are being used to anchor the photochemical moieties as well as the catalysts necessary for generation of hydrogen and oxygen from water.

          In the photosynthetic process in plants, chloroplasts absorb solar energy and drive a “biological machine” that results in conversion of water and carbon dioxide to oxygen and carbohydrates, the molecular building blocks for complex macroscopic structures. This process makes possible life on earth. The eventual conversion of small, plentiful molecules to useful chemicals including fuel, polymers, drugs etc. with the help of solar energy is an attractive paradigm for long-term space exploration and inhabitation. In the proposed research program, we provide a plan for assembly of an artificial photosynthetic system using the light driven conversion of water to hydrogen and oxygen as a model reaction. Based on a crude mimic of the natural photosynthetic apparatus, we propose the use of ordered microporous aluminosilicate (zeolite) membranes assembled from nanoscale building blocks as the template for light absorbing sensitizers (electron donors), electron acceptors and catalyst systems. Strategies for slowing the energy wasting back electron transfer, charge propagation through nanochannels, and efficient catalyst incorporation is proposed. The fundamental photochemical units are polypyridyl complexes of ruthenium, Ru(bpy)₃²⁺ (where bpy = bipyridine), which upon visible light excitation leads to a photoexcited state, Ru(bpy)₃^{2+ *} that undergoes electron transfer with bipyridinium ions.  Metal oxides will be used for the multi-electron catalysis involving Ru(bpy)₃³⁺ and bipyridinium radical ions in splitting of water. Use of the zeolite membrane allows for spatial separation of the hole and electron chemistry, thereby minimizing energy wasting recombination processes The strategy we propose here for assembly of complex, multifunctioning units into a device relies heavily on the ordered nanostructure of synthetic aluminosilicate zeolites and should be extendable to more complex photosynthetic reactions.