Artificial Photosynthesis Model: Photochemical Reaction System with Efficient Light-Harvesting Function on Inorganic Nanosheets

In natural photosynthesis system, its complicated photofunctions are achieved with high efficiency through precise arrangements of dye molecules in proteins. However, it is difficult to imitate such reaction systems artificially because of the complexity of the protein structures. As the way to approach this issue, we suggest the self-assembling behavior of photofunctional dyes on inorganic nanosheets. In this study, photochemical reaction system with a light-harvesting function was newly constructed on a clay nanosheet as an artificial photosynthesis system model by using a metalloporphyrin as a photocatalyst and a subporphyrin as a photoanntena. Under the condition of their co-adsorption on the nanosheet, efficient energy transfer from the subporphyrin to the metalloporphyrin of up to 98% was achieved in the case of donor/acceptor ratio of 1:1. By utilizing such dye–clay complexes, the metalloporphyrin photocatalyst could catalyze the photochemical conversion of cyclohexene by the excitation of both the subporphyrin photoantenna and itself. This light-harvesting system enabled the photocatalytic reaction to use a wider range of visible region without any energy loss because of suppression of unexpected other deactivation processes by precise arrangement of dyes in contrast to general co-adsorption systems. These results would be useful in constructing various types of artificial photosynthesis systems using self-assembling behavior