Electron-Deficient Single-Molecule-Junction Sites in COFs Enable H₂O₂ Photosynthesis via Precision Charge Delivery and Oxygen Adsorption.

Abstract

Covalent organic frameworks (COFs) have emerged as a promising platform for photocatalytic H₂O₂ production, a key reaction in artificial photosynthesis. However, the practical application of conventional benzene-rich COF skeletons is often limited by their weak oxygen adsorption capacity and inefficient charge carrier transport. To address these challenges, we report a universal post-synthetic strategy that incorporates local, electron-deficient polar single-molecule junctions into the COF framework via a straightforward one-step modification. These engineered junctions play a dual role: the localized electron-deficient sites strongly anchor and activate oxygen molecules, while the in-built polarity establishes directional channels for the migration of photogenerated charge carriers, ensuring their precise delivery to active sites. This synergistic mechanism leads to a marked enhancement in superoxide radical generation and the subsequent synthesis of H₂O₂. Under acidic conditions (pH = 3), the H₂O₂ generation rate of the monomolecularly-linked COF reached 4354 µmol g^-1 h^-1, significantly higher than the 1655 µmol g^-1 h^-1 of the pristine COF. The broad applicability of this design principle was firmly established through the successful implementation of a series of tailor-made analogous molecules across several distinct COF platforms.