Continuous-flow photochemistry in microreactors receives a lot of attention from researchers in academia and industry as this technology provides reduced reaction times, higher selectivities, straightforward scalability, and the possibility to safely use hazardous intermediates and gaseous reactants. In this review, an up-to-date overview is given of photochemical transformations in continuous-flow reactors, including applications in organic synthesis, material science, and water treatment. In addition, the advantages of continuous-flow photochemistry are pointed out and a thorough comparison with batch processing is presented.
The use of solar light to promote chemical reactions holds significant potential with regard to sustainable energy solutions. While the number of visible light-induced transformations has increased significantly, the use of abundant solar light has been extremely limited. We report a leaf-inspired photomicroreactor that constitutes a merger between luminescent solar concentrators (LSCs) and flow photochemistry to enable green and efficient reactions powered by solar irradiation. This device based on fluorescent dye-doped polydimethylsiloxane collects sunlight, focuses the energy to a narrow wavelength region, and then transports that energy to embedded microchannels where the flowing reactants are converted.
The sun is the most sustainable light source available on our planet, therefore the direct use of sunlight for photochemistry is extremely appealing. Demonstrated here, for the first time, is that a diverse set of photon‐driven transformations can be efficiently powered by solar irradiation with the use of solvent‐resistant and cheap luminescent solar concentrator based photomicroreactors. Blue, green, and red reactors can accommodate both homogeneous and multiphase reaction conditions, including photochemical oxidations, photocatalytic trifluoromethylation chemistry, and metallaphotoredox transformations, thus spanning applications over the entire visible‐light spectrum. To further illustrate the efficacy of these novel solar reactors, medicinally relevant molecules, such as ascaridole and an intermediate of artemisinin, were prepared as well.
The
use of solar energy to power chemical reactions is a long-standing
dream of the chemical community. Recently, visible-light-mediated
photoredox catalysis has been recognized as the ideal catalytic transformation
to convert solar energy into chemical bonds. However, scaling photochemical
transformations has been extremely challenging due to Bouguer–Lambert–Beer
law. Recently, we have pioneered the development of luminescent solar
concentrator photomicroreactors (LSC-PMs), which display an excellent
energy efficiency. These devices harvest solar energy, convert the
broad solar energy spectrum to a narrow-wavelength region, and subsequently
waveguide the re-emitted photons to the reaction channels. Herein,
we report on the scalability of such LSC-PMs via a numbering-up strategy.
Paramount in our work was the use of molds that were fabricated via
3D printing. This allowed us to rapidly produce many different prototypes
and to optimize experimentally key design aspects in a time-efficient
fashion. Reactors up to 32 parallel channels have been fabricated
that display an excellent flow distribution using a bifurcated flow
distributor (standard deviations below 10%). This excellent flow distribution
was crucial to scale up a model reaction efficiently, displaying yields
comparable to those obtained in a single-channel device. We also found
that interchannel spacing is an important and unique design parameter
for numbered-up LSC-PMs, which influences greatly the photon flux
experienced within the reaction channels.
A simple and inexpensive reaction control system mitigates the impact of solar irradiance fluctuations on the conversion of a sunlight-powered photochemical reaction, affording constant product quality.
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