Fused‐Ring Acceptor–π–Acceptor Architecture Enables Near‐Infrared‐Absorbing Mesoporous Covalent Organic Frameworks for Enhanced H ₂ O ₂ Photosynthesis

Abstract

ABSTRACT Covalent organic frameworks (COFs) featuring donor–acceptor architectures have shown great promise as photocatalysts. However, their performance is often hindered by limitations such as narrow absorbance ranges and restricted electron delocalization, which are inherent to traditional imine linkages. Herein, we introduce a fused‐ring acceptor–π–acceptor (FRA–π–A) architecture for near‐infrared‐absorbing COFs, enabled via in situ COF‐to‐COF transformation that replaces imine linkages with FRA‐derived benzodithiazoles (or benzodioxazoles). Comprehensive structural characterizations confirm their mesoporous crystalline structure, featuring pore size distribution of 2.16–2.39 nm and broad light absorption extending to near‐infrared region. Property investigations demonstrate that the rigid backbones derived from the FRA–π–A architecture significantly enhance long‐range in‐plane electron delocalization, thereby improving the separation and transport of photogenerated charge carriers. Crucially, the accelerated carrier migration preferentially directs photogenerated electrons to the FRAs, promoting the formation of •O 2 − radicals and accelerating the rate‐limiting step of the oxygen reduction reaction. These synergistic structural and optoelectronic properties endow the FRA–π–A COFs with an outstanding photocatalytic H 2 O 2 production rate of 6.8 mmol g − 1 h − 1 without sacrificial agents, exceeding the vast majority of conjugated linkage‐based COFs. This study highlights the immense potential of FRA–π–A COFs as high‐performance photocatalysts.