Indolo[3,2-b]carbazole-based MOF for oxidative coupling of amines powered by blue light

Abstract

The development of photocatalysts via the introduction of novel photoactive groups represents a significant and promising direction in the field of photocatalysis, holding immense potential and importance for advancements in organic synthesis. Herein, a new photoactive ligand, which is based on indolo[3,2-b]carbazoles with four carboxyl groups, was synthesized, and then a new polynuclear metal–organic framework (MOF, NUT-121) with a rare 4,8-connected topological structure was constructed. Photoelectric characterizations revealed that the strong light-harvesting properties of the ligand are retained in NUT-121, which was employed for the photocatalytic oxidation of amines to imines under blue light, affording 100% conversion with 94% selectivity. Furthermore, high efficiency, excellent recyclability, and broad substrate scope toward benzylamine derivatives were consequently demonstrated. Both quenching experiments and electron paramagnetic resonance (EPR) studies indicate that the formation of imines originates from singlet oxygen (¹O₂). This research presents ICz-based MOFs for efficient heterogeneous catalytic conversion of benzylamine.