Designed polymeric conjugation motivates tunable activation of molecular oxygen in heterogeneous organic photosynthesis

Abstract

Photocatalytic oxidative organic reactions are important synthetic transformations, and research on reaction selectivity by reactive oxygen species (ROS) is significant. To date, however, there has rarely been any focus on the directed generation of ROSs. Herein, we report the first identification of tunable molecular oxygen activation induced by polymeric conjugation in nonmetallic conjugated microporous polymers (CMP). The conjugation between these can be achieved by the introduction of alkynyl groups. CMP-A with an alkynyl bridge facilitates the intramolecular charge mobility while CMP-D, lacking an alkynyl group enhances the photoexcited carrier build-up on the surface from diffusion. These different processes dominate the directed ROS generation of the superoxide radical (O₂^-) and singlet oxygen (¹O₂), respectively. This theory is substantiated by the different performances of these CMPs in the aerobic oxidation of sulfides and the dehydrogenative coupling of amines, and could provide insight into the rational design of CMPs for various heterogeneous organic photosynthesis.

Keywords: Aerobic oxidation; Conjugated polymers; Molecular oxygen activation; Photocatalysis; Polymeric conjugation.