A Laser Driven Flow Chemistry Platform for Scaling Photochemical Reactions with Visible Light

Abstract

Visible-light-promoted organic reactions can offer increased reactivity and selectivity via unique reaction pathways to address a multitude of practical synthetic problems, yet few practical solutions exist to employ these reactions for multikilogram production. We have developed a simple and versatile continuous stirred tank reactor (CSTR) equipped with a high-intensity laser to drive photochemical reactions at unprecedented rates in continuous flow, achieving kg/day throughput using a 100 mL reactor. Our approach to flow reactor design uses the Beer–Lambert law as a guideline to optimize catalyst concentration and reactor depth for maximum throughput. This laser CSTR platform coupled with the rationale for design can be applied to a breadth of photochemical reactions.

An oscillatory plug flow photoreactor facilitates semi-heterogeneous dual nickel/carbon nitride photocatalytic C–N couplings

“…This corresponds to an exceptionally high productivity of 2.67 g h −1 (15 mmol h −1 ), a value to our knowledge only surpassed by some homogeneous Ir-or Ru-based photoredox catalyzed C-N couplings. 6,26 It is noteworthy that the larger version of the HANU™ reactor (150 mL volume, 10× scale up) maintains all of its process characteristics (e.g. channel dimensions, mass-, heat-, and light transfer capacities, RTD), thus allows for straightforward scale-up of such procedures.…”

Reactivity control of a photocatalytic system by changing the light intensity

“…Catalytic cycles comprising the consecutive absorption of two photons with an excited state as intermediate (i.e., without converting the excited state into a long-lived radical anion) 23,24 were realized under continuous wave (cw) excitation conditions only very recently. 25 The feasibility of this new kind of two-photon chemistry on the preparative scale with an inexpensive blue diode laser, 26 whose acquisition costs are practically identical to those of comparable ready-to-use high-power LEDs, inspired the reactivity control approach presented herein. As we will show, the excitation of our recently developed water-soluble catalyst Irsppy 27 (see Scheme 1 for its structure) with a single blue photon can initiate several dehalogenation and isomerization reactions, but when a second photon is absorbed within the lifetime of its excited triplet state ( 3 Irsppy) using higher light intensities per irradiation area, highly aggressive hydrated electrons (e aq c À ) that react with the same substrates via a completely different pathway are produced, thereby allowing a fundamentally new reactivity control strategy and its application to selective photo(redox) applications.…”

Beyond electrolysis: old challenges and new concepts of electricity-driven chemical reactors

“…Recently, a continuous-flow stirred-tank photoreactor with a fiber-coupled, high-powered diode laser as the light source has been investigated. 50 The reactor utilizes an adjustable beam expander to ensure uniform illumination of the liquid surface ( Fig. 4).…”

“…Continuous stirred-tank photo reactor with fiber-coupled laser diode as the light source. Reprinted from Harper et al,50 with permission from ACS.…”