MARCUS BAUMANN
School of Chemistry, University College Dublin, Science Centre South, Belfield, Ireland

Abstract

The union of continuous flow processing and photochemistry has enabled the effective generation of target molecules of ever-increasing complexity and with growing selectivity. Inherent benefits of flow reactors are thereby exploited for better heat and mass transfer, containment of high energy light as well as scalability irrespective of reactor footprint. This short perspective article evaluates the advances of continuous flow photochemistry towards greener chemical synthesis and highlights remaining challenges that will need to be resolved to meet our sustainability goals.

INTRODUCTION
Performing chemical reactions under photochemical conditions is considered an inherently sustainable means to generate target structures of interest. The ability to trigger a vast variety of transformations photochemically, whereby selectivity arises from finetuning the wavelength and intensity of light, offers great control over a given process. Moreover, photons are seen as traceless reagent equivalents that could replace stoichiometric reagents or act in tandem with bespoke photocatalysts to bring about the green synthesis of drug-like target structures and important chemical building blocks alike (1).

Over a century ago, the pioneering work of Ciamician, who is rightly considered as one of the pioneers of synthetic photochemistry, laid the foundations for modern photochemistry by showcasing how many new chemical transformations can be achieved using light. In his 1912 landmark paper on the future of photochemistry, Ciamician outlines how this technology holds the potential to establish chemical synthesis independent of fossil sources of energy and related organic building blocks (2). Despite this vision photochemist ...