A Hybrid Catalyst for Light-Driven Green Molecular Transformations

This Minireview is focused on the development of hybrid catalysts composed of photosensitizers and a metal complex, especially vitaminB(12) derivatives. The semiconductor-metal complex composites are effective photocatalysts for molecular transformations due to the synergistic effect between the two components. The design of a B-12 complex for the hybridization with TiO2 was simple and straightforwardcobyrinic acid, having seven carboxylic groups derived from naturally occurring B-12 is stably immobilized on the TiO2. By using the hybrid catalysts as mimics of B-12-dependent enzymes, light-driven reactions such as the dechlorination of organic halide pollutants, and radical-mediated isomerization proceeded catalytically. In addition to the enzyme-mimicking reactions, bioinspired reactions were also developed with the hybrid catalyst. The B-12-TiO2 hybrid catalyst was used for hydrogen evolution and alkene reduction by UV light irradiation, and the cobalt-hydrogen complex (Co-H complex) was considered to be a putative intermediate of the reactions. The multidisciplinary concept for the design of a hybrid catalyst is described in this Minireview.