Molecular Design of Perylene Diimide Derivatives for Photocatalysis

Perylene diimides (PDIs) and their derivatives represent a kind of most promising photocatalytic materials due to their strong visible light absorption, ease of functionalization, excellent thermal/photostability, as well as tunable electronic structures and energy levels. However, several challenges persist in the development of PDI photocatalysts, including low electron–hole separation efficiency, slow charge transfer, and rapid carrier recombination. In this perspective, we focus on enhancing the performance of PDI photocatalysts through a molecular design. We provide a comprehensive overview of various improvement strategies: (1) precise modulation of molecular dipole moments by altering the polarity of side chains to strengthen the built-in electric field, (2) utilization of steric hindrance and noncovalent interactions of side chains to construct nanoscale, highly ordered supramolecular nanostructures, (3) modification of the perylene core to adjust molecular energy levels and increase the number of active sites, (4) integration of PDI with various semiconductors or metals to form composite systems that enhance the interfacial built-in electric field or create extensive delocalized charge channels, and (5) selection of suitable linker groups to build polymer photocatalysts with large dipole moments. These strategies can facilitate the separation and migration of photogenerated carriers in PDI photocatalysts, eventually boosting their photocatalytic efficiency. The relationship between molecular structure and photocatalytic performance, particularly in the context of photocatalytic degradation and water splitting, is examined in detail. Finally, the future prospects and challenges of PDI photocatalysts are thoroughly discussed.