Visible-Light-Responsive Anthraquinone Functionalized Covalent Organic Frameworks for Metal-Free Selective Oxidation of Sulfides: Effects of Morphology and Structure

Visible-light-responsive covalent organic frameworks (COFs) as photocatalysts for metal-free organic reactions are highly desirable due to their structural controllability and molecular functionality. In this study, we describe the fabrication of an anthraquinone functionalized COF linked by beta-ketoenamines (AQ-COF), which presents a noodle-like nanofiber structure with staggered AB stacking mode. The as-resultant AQ-COF was efficiently utilized as a metal-free heterogeneous catalyst for selective aerobic oxidation of sulfides under visible-light irradiation. Compared with the precedential AQ-COFDMF with spherical particles, the proposed AQ-COF presents a higher photocatalytic activity with high selectivity to sulfoxides and chemical stability. Further characterization techniques revealed that the unique morphology and structure can greatly enhance charge transfer and separation efficiency of photogenerated electron-hole pairs, thus giving rise to the improvement of photocatalytic activity.