Ionic porous porphyrin cage as a superior catalyst for photocatalytic oxidization

Abstract

Aggregation-induced deactivation has long been a challenge in the field of photocatalysis based on molecular porphyrin derivative-based photocatalysts. The development of polyhedral porphyrin cage-based heterogeneous catalysts has shown promise in addressing this issue by preventing intermolecular face-to-face packing. However, this shift towards heterogeneous catalysis comes at the cost of catalytic activity. Herein, we report the design and synthesis of an ionic porphyrin cage, TPPCage·8I, characterized with a high charge density within the skeleton. This strategy effectively circumvents spontaneous aggregation by harnessing the electrostatic repulsion that naturally occurs between adjacent cage hosts. Furthermore, the strategic incorporation of hydrophilic iodine counteranions surrounding the cage not only modulates their solubility, making them uniformly dispersed in the solvent, but also imparts an additional heavy-atom effect. These modifications lead to substantial enhancement in photophysical properties, resulting in extraordinary catalytic activity in the photocatalytic oxidation coupling reaction of benzylamines, with a remarkable conversion rate exceeding 99% and a record turnover frequency (TOF) of 1980.0 h⁻¹, coupled with excellent stability. In addition, the current homogeneous photocatalyst offers ease of recycling through a straightforward exchange process with a robust hydrophobic anion (sodium dodecyl sulfate, SDS).