Dye molecule-containing polymeric photosensitizer as a high-performance photocatalyst for aerobic chemical conversion†

Visible light-catalyzed chemical transformations represent one of the most environmentally benign pathways towards achieving sustainable development. However, most visible light-mediated systems currently employ expensive noble metals (e.g. Ru, Ir) and difficult-to-recycle small-molecule organic dyes. In this work, two novel, cost-effective, and easily separable polymeric photosensitizers were successfully synthesized and employed as metal-free heterogeneous photocatalysts for the α-oxidation of N-aryltetrahydroisoquinolines (model reaction 1) and methylation of quinoxalin-2(1H)-ones (model reaction 2), respectively. All reactions proceeded smoothly upon irradiation with an LED under aerobic conditions at room temperature and were easily scaled up. The photocatalysts can be readily recovered and reused (up to 10 cycles) without significant loss of catalytic activity, indicating a very promising potential for practical applications. Mechanism studies indicated that only the superoxide radical anion was involved in the above model reactions.