Thiadiazole-functionalized metal-organic frameworks for photocatalytic C-N and C-C coupling reactions: tuning the ROS generation efficiency via cobalt introduction

Heterogeneous photocatalytic organic transformations have attracted widespread attention due to their high efficiency, eco-friendliness, and atom economy. Herein, we report a cobalt-based metal-organic framework (JNU-207) constructed using a thiadiazole-functionalized photosensitizing ligand. The introduction of the cobalt cluster endows JNU-207 with an extended visible-light absorption, suppressed electron-hole recombination, an enhanced ROS (reactive oxygen species) generation efficiency, a lowered lowest unoccupied molecular orbital (LUMO) energy level, and reduced bandgaps. Its improved electrochemical and photochemical properties were further manifested in the efficient photocatalysis of the oxidative coupling of benzylamines and the oxidative coupling of tertiary anilines with maleimides. In each reaction, the photocatalytic performance of JNU-207 was superior to that of the zinc-based isostructural JNU-204 MOF. In addition, JNU-207 shows excellent chemical stability and can be recovered easily through filtration and re-used without special treatment or activation. This work demonstrates a viable strategy for building robust metal-organic frameworks and addressing the challenges of light absorption, the ROS generation efficiency, and the charge-separation efficiency in photocatalysis.