Modulating Quinoline-Linked Covalent Organic Frameworks via Fluorination for Boosting the Photocatalytic Air Reductive H₂O₂ Production

The intrinsic reversibility and strong polarization of imine linkages limit the application of imine-based covalent organic frameworks (COFs) in photocatalysis. Herein, inspired by the aza-Diels–Alder cycloaddition reaction, two quinoline-linked fluorinated COFs (termed TTB-TTA-Ph-F and TTB-TTA-Ph-3F) are developed based on postsynthetic modification of an imine-linked COF (TTB-TTA). The simultaneous reversibility-to-irreversibility bond transformation and fluorination endow the resultant COFs with improved robustness, extended structural conjugation, and intriguing optoelectronic properties. The introduced fluorine groups change the local electronic structures of the COFs and improve charge separation and transfer. Benefiting from the rational design on the COF skeleton, TTB-TTA-Ph-3F exhibits excellent activity, giving a 3496.9 μmol g–1 h–1 of photocatalytic H2O2 production rate from water and air after optimizing by fluorine modulation.