Synergistic Optimization of Optical Absorption and Charge Separation via Linker Engineering in Covalent Organic Frameworks

ABSTRACT Covalent organic frameworks (COFs) with tunable porous architectures, extended π ‐conjugation, and adjustable electronic structures have emerged as promising platforms for optoelectronic applications. While most studies have focused on tuning topological architectures, linkage chemistries, and interfacial hydrophilicity, direct modulation of intrinsic light‐harvesting properties through molecular‐level design remains underexplored. Herein, we present a linker functionalization strategy based on a fully π ‐conjugated skeleton, in which specific molecular units are incorporated along the pore walls to induce resonance and conjugation effects. This approach precisely tailors the electronic structure and enhances π ‐delocalization, thereby broadening light absorption and promoting charge‐carrier separation to improve overall photophysical performance. Consequently, methoxy‐functionalized COF exhibits significantly higher photocatalytic activity than hydrogen‐anchored skeleton, achieving nearly a three‐fold increase in hydrogen peroxide production under visible‐light irradiation, along with excellent long‐term stability and durability. These findings demonstrate that linker functionalization is an effective molecular design strategy for developing high‐performance COF‐based photocatalysts.