Covalent Organic Frameworks toward Diverse Photocatalytic Aerobic Oxidations

Photoactive two-dimensional covalent organic frameworks (2D-COFs) have become promising heterogenous photocatalysts in visible-light-driven organic transformations. Herein, a visible-light-driven selective aerobic oxidation of various small organic molecules by using 2D-COFs as the photocatalyst was developed. In this protocol, due to the remarkable photocatalytic capability of hydrazone-based 2D-COF-1 on molecular oxygen activation, a wide range of amides, quinolones, heterocyclic compounds, and sulfoxides were obtained with high efficiency and excellent functional group tolerance under very mild reaction conditions. Furthermore, benefiting from the inherent advantage of heterogenous photocatalysis, prominent sustainability and easy photocatalyst recyclability, a drug molecule (modafinil) and an oxidized mustard gas simulant (2-chloroethyl ethyl sulfoxide) were selectively and easily obtained in scale-up reactions. Mechanistic investigations were conducted using radical quenching experiments and in situ ESR spectroscopy, all corroborating the proposed role of 2D-COF-1 in photocatalytic cycle.

Automated summary

This study demonstrates the potential of photoactive two-dimensional covalent organic frameworks (2D-COFs) as heterogeneous photocatalysts in visible-light-driven organic transformations. Using 2D-COFs as the photocatalyst enables efficient oxidation of various small organic molecules under mild reaction conditions, leading to high yields and excellent functional group tolerance in the obtained products. Additionally, the inherent advantages of heterogeneous photocatalysis, sustainability, and easy recyclability of the photocatalyst were highlighted through selective and easy scale-up reactions to obtain specific drug molecules and simulant of oxidized mustard gas.