Sustainable Photooxidation using a Subpart-per-million Heavy-Metal-Free Red-Light Photocatalyst

Abstract

Photochemical activation using red or near-infrared light has recently emerged as a potential remedy for solving fundamental issues in photochemistry such as selectivity and scale up. However, this is particularly challenging in the case of photooxidation chemistry due to the low resistance to photobleaching and poor solubility of photocatalysts absorbing in this region of the electromagnetic spectrum. In this study, we report the use of commercially available Si-phthalocyanines as a robust and environmentally friendly class of soluble photosensitizers activated under red light. Interestingly, while Si-phthalocyanines exhibit lower singlet oxygen generation (ϕΔ) quantum yields compared to classical photosensitizers, their high stability enables us to achieve comparable efficiencies at ultralow catalytic loadings (ppb range). This unique feature provides high catalytic performances in a range of photooxidative processes and under high substrate concentrations ultimately leading to safe and efficient solvent-free continuous flow processes applied to multigram-scale synthesis.

Photo Microreactor with Luminescent Fluid Mediating Solar Photochemical Synthesis

“…As early as in 1834, solar light was used to activate photochemical reactions . To date, with the emergence of visible-light photocatalysis, solar photochemical synthesis has exhibited good prospects for practical application. , Meanwhile, new discoveries or concepts in photocatalysis, e.g., photocatalysts absorbing red light that afford high efficiency at ppb loadings and three-phase flow to enable continuous recycling of the photocatalyst, are continually springing up, which will aid in enhancing the sustainability of solar photochemical synthesis. Also, with regard to new technologies, the application of microreactor technology provides a more photon-efficient and scalable way to conduct solar photochemical synthesis, and the luminescent solar concentrator photo microreactor (LSC-PM) stands out among the current solar photochemical reactors for converting the photons of higher energy to those that can match the wavelength demands of photoreactions and exhibiting the potential of using sunlight as the sole energy source …”