Azobenzene‐bridged Covalent Organic Frameworks Boosting Photocatalytic Hydrogen Peroxide Production from Alkaline Water: One Atom Makes a Significant Improvement

Covalent organic frameworks (COFs) have been demonstrated as promising photocatalysts for hydrogen peroxide (H 2 O 2 ) production. However, the construction of COFs with new active sites, high photoactivity, and wide‐range light absorption for efficient H 2 O 2 production remains challenging. Herein, we present the synthesis of a novel azobenzene‐bridged 2D COF (COF‐TPT‐Azo) with excellent performance on photocatalytic H 2 O 2 production under alkaline conditions. Notably, although COF‐TPT‐Azo differs by only one atom (−N=N− vs. −C=N−) from its corresponding imine‐linked counterpart (COF‐TPT‐TPA), COF‐TPT‐Azo exhibits a significantly narrower band gap, enhanced charge transport, and prompted photoactivity. Remarkably, when employed as a metal‐free photocatalyst, COF‐TPT‐Azo achieves a high photocatalytic H 2 O 2 production rate up to 1498 μmol g −1 h −1 at pH = 11, which is 7.9 times higher than that of COF‐TPT‐TPA. Further density functional theory (DFT) calculations reveal that the −N=N− linkages are the active sites for photocatalysis. This work provides new prospects for developing high‐performance COF‐based photocatalysts.