Perfluoroarene–arene interaction cocrystal of perfluorocarbazoles toward IEF-enhanced photocatalysis

Abstract

The photocatalytic generation of highly reactive oxygen species (ROS) such as H₂O₂ and ˙OH, using molecular oxygen without sacrificial reagents or metal catalysts, is a significant challenge. To address this, we introduce a novel approach by adding a second perfluoroarene layer to arene–perfluoroarene cocrystals, which enhances the dipoles between the π-hole and π-donor layers, thereby increasing the internal electric field (IEF) and improving charge separation. We successfully synthesized a series of perfluorocarbazole derivatives through a Pd-catalyzed C–Br/C–F amination reaction. Three cocrystals, Pe–FPC (1 : 2), Pe–FMC (1 : 2), and TP–FPC (1 : 1) were synthesized, with Pe–FPC (1 : 2) exhibiting exceptional photocatalytic activity. Pe–FPC (1 : 2) effectively degrades RhB, MB, and Eosin B in a short time period under air, demonstrating excellent stability over seven cycles. It also catalyzes the oxidation of aromatic and aliphatic aldehydes to carboxylic acids, outperforming small-molecule catalysts in aqueous-phase reactions. Mechanistic studies show that h⁺, ˙O₂⁻, ˙OH, ¹O₂, and H₂O₂ synergistically contribute to the photoinduced oxidation process. The Pe–FPC (1 : 2) cocrystal also shows a high H₂O₂ production yield (2640 μmol h⁻¹ g⁻¹), with enhanced surface potential and a lower photoluminescence lifetime, confirming the improved IEF and charge separation. This work validates our hypothesis that introducing a second perfluoroarene layer enhances photocatalytic efficiency, opening new avenues for the design of high-performance photocatalysts for energy and environmental applications.