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 (ϕ Δ ) 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.