Applications of Sensitized Semiconductors as Heterogeneous Visible-Light Photocatalysts in Organic Synthesis

The industrial transition to more-sustainable chemical manufacturing requires the development of a variety of high-performance heterogeneous catalysts. Recently, new classes of heterogeneous and recyclable catalysts that exploit visible-light activation have emerged in the field of organic synthesis. Among these systems, sensitized semiconductors occupy a strategic place as they are able to initiate single electron transfer processes under heterogeneous conditions and using medium-to-low energy light activation. This technology can promote a range of synthetically useful reactions, such as oxidations, reductions, or additions, including C–C bond formation, under very mild conditions and with high selectivity. Sensitized semiconductors have been known for decades in solar cell technologies (the so-called “Dye-Sensitized Solar Cells”) but applications in organic synthesis are only very recent. This Review provides a comprehensive overview of the mechanisms, reactivity, and scope of this technology, with a focus on their new and promising synthetic applications.