Building a Pyrazole-Benzothiadiazole-Pyrazole Photosensitizer into Metal-Organic Frameworks for Photocatalytic Aerobic Oxidation

Charge separation plays a crucial role in regulating photochemical properties and therefore warrants consideration in designing photocatalysts. Metal-organic frameworks (MOFs) are emerging as promising candidates for heterogeneous photocatalysis due to their structural designability and tunability of photon absorption. Herein, we report the design of a pyrazole-benzothiadiazole-pyrazole organic molecule bearing a donor-acceptor-donor conjugated pi-system for fast charge separation. Further attempts to integrate such a photosensitizer into MOFs afford a more effective heterogeneous photocatalyst (JNU-204). Under visible-light irradiation, three aerobic oxidation reactions involving different oxygenation pathways were achieved on JNU-204. Recycling experiments were conducted to demonstrate the stability and reusability of JNU-204 as a robust heterogeneous photocatalyst. Furthermore, we illustrate its applications in the facile synthesis of pyrrolo[2,1-a]isoquinoline-containing heterocycles, core skeletons of a family of marine natural products. JNU-204 is an exemplary MOF platform with good photon absorption, suitable band gap, fast charge separation, and extraordinary chemical stability for proceeding with aerobic oxidation reactions under visible-light irradiation.

Automated summary

Charge separation is crucial in regulating photochemical properties in photocatalysts design. Metal-organic frameworks (MOFs) are promising candidates for heterogeneous photocatalysis due to their designability and photon absorption tunability. A pyrazole-benzothiadiazole-pyrazole organic molecule with a donor-acceptor-donor conjugated pi-system was designed for fast charge separation, resulting in a more effective heterogeneous photocatalyst JNU-204, which demonstrated stability and reusability in aerobic oxidation reactions under visible-light irradiation. JNU-204 also showed applications in the synthesis of marine natural product core skeletons.