Engineering electron acceptors in fluorinated covalent organic frameworks toward high-efficiency photocatalytic hydrogen peroxide production and cancer therapy.

Covalent organic frameworks (COFs) are promising for metal-free, sustainable photocatalytic hydrogen peroxide (H2O2) production from water and oxygen. However, their current photocatalytic efficiency remains hampered by insufficient charge separation and migration, limiting practical applications. To tackle this issue, we developed three donor-acceptor (D-A) COFs with hcb topology by incorporating fluorine-containing groups into the acceptor units, thereby enhancing the electron-transfer capability within the D-A conjugated system. Photochemical characterization and theoretical calculations revealed a significant charge difference between the adjacent benzene rings of the donor and acceptor in the non-fluorinated D-A COF (TAPB-TPA COF), indicating that the D-A structure itself facilitates the migration of photogenerated electrons. In the fluorinated TFTA-TPA COF, the charge difference between adjacent benzene rings was further increased, which not only promoted efficient carrier migration but also optimized the oxygen reduction reaction (ORR) pathway. Notably, a production rate of 5785.2 μmol·g-1·h-1 for H2O2 was achieved by TFTA-TPA COF under sacrificial-agent-free conditions in pure water, significantly surpassing the performance of TAPB-TPA COF. Furthermore, TFTA-TPA COF was applied to tumor therapy, where its in-situ generated H2O2 induced cell death with good biocompatibility and therapeutic efficacy. This work offers a fresh perspective on the utility of COF materials, bridging photocatalysis and biomedicine.