Recent advances toward sustainable flow photochemistry

Although flow photochemistry has significant potential in advancing sustainable processing, there are substantial hurdles to attaining this. Development in three key areas over the past 3 years are discussed here: 1) light source technology; 2) reactor design; and 3) process understanding and intensification. A small number of illustrative examples provide an insight on the benefits that can be accessed through advances in these areas. More in-depth knowledge and experimentation around wavelength dependence can enhance efficiency and selectivity in transformations. Reactors capable of handling solid–liquid reactions can allow reliable processing of metal-free and recyclable catalyst systems. Concentrating and accelerating transition-metal/photoredox coupling methodologies make these processes increasingly attractive. Continuation of these trends will undoubtedly lead to future large-scale applications, carried out in a sustainable manner.