Continuous Flow Photo-oxidations Using Supported Photocatalysts on Silica

The immobilization of soluble photocatalysts, or photosensitizers, has the potential to reduce the environmental footprint as well as the costs associated with visible-light photochemical processes. We report here on the straightforward preparation of photocatalysts non-covalently supported on silica using electrostatic interactions and compare the activities of these new photocatalytic systems in the photo-oxidation of 1,5-dihydroxynaphthalene to juglone in batch and in a fixed-bed flow reactor. This study demonstrates that simple immobilization strategies can produce stable heterogeneous photocatalysts and provide promising processing options with an up to 24-fold improvement in productivity in flow relative to batch.