Perylenediimide Halogen Substitution-Modulated Photochromism and Photocatalytic Activity in Metal−Organic Frameworks

Abstract

Perylenediimides (PDIs), which feature strong visible-light absorption, π-electron-deficient planes, and photochemical characteristics, offer a versatile platform for developing tunable and efficient metal−organic framework (MOF) materials through modulation of their bay-substituent groups. Herein, we report ‌two structurally modified MOFs, MOF-Cl4 and MOF-Br2, whose PDI components feature different halogen substitution patterns in their bay regions, imparting differential halogen-controlled photochromism. Notably, MOF-Cl4 exhibited high photosensitivity, whereas MOF-Br2 was found to be almost photochemically inert. Furthermore, both MOFs could be readily photoexcited to generate their respective excited states or radical anions. Interestingly, experimental and theoretical calculations revealed that these excited states or radical anions demonstrated halogen-controlled photocatalytic activities in the oxysulfonylation of alkynes and the aerobic oxidation of enamines. The photocatalytic performance of MOF-Cl4 proved superior to that of MOF-Br2, a difference primarily attributed to the divergent SOMO-1 and optical bandgap of the PDI ligands and MOF materials, induced by the halogen substitution patterns.