Sunlight might be used in the future to drive organic syntheses for pharmaceuticals and agrochemicals, Timothy Noël of Eindhoven University of Technology told his audience at yesterday’s plenary lecture.
Over the last decade, Noël’s research group has shown that flow reactors equipped with special light collectors can achieve good yields and selectivity in reactions that normally require aggressive reagents and high temperatures. As an example, he gave the oxidation of cyclohexane.
Traditional photochemistry requires ultraviolet light, which can damage complex organic molecules. A technique known as photoredox catalysis uses visible light instead, but the problem remains that incident light penetrates less than 1 mm into the reaction mixture. Noël’s solution is to combine narrow-bore (0.5 mm) flow reactors with luminescent solar concentrators (LSCs). Made from transparent plastic doped with dye, LSCs have a dual function. First, they convert the broad spectrum of sunlight to the ideal wavelength for the reaction.
Second, they act as waveguides to boost the amount of light collected. The final step is to control the reagent flow so as to maintain conversion in cloudy weather.
The combination of photomicroreactors (PMs) with LSCs uses sunlight and mild reaction conditions to create a truly green solution for organic chemistry. At the event, Noël received the 2017 Dechema Prize for his work.