Flexible Hydrazone‐Linked Covalent Organic Frameworks With Enhanced Emission and Selective Nitroaromatic Sensing Performance

Covalent organic frameworks (COFs), with their highly ordered and extended π‐conjugated architectures, offer great promise for the development of efficient solid‐state luminescent materials. However, their photoluminescence is often hindered by aggregation‐caused quenching (ACQ), limiting practical applications. To address this issue, we rationally designed and synthesized two novel hydrazone‐linked COFs incorporating flexible vertex units into the backbone, thereby introducing structural flexibility. These COFs exhibit strong green emission in the solid state with high quantum yields approaching 20%, effectively mitigating ACQ effects. Moreover, the incorporation of abundant heteroatoms within the frameworks enables strong noncovalent interactions with electron‐deficient nitroaromatic compounds, particularly 2,4,6‐trinitrophenol (TNP), resulting in highly sensitive and selective fluorescence‐based detection. This study demonstrates a viable strategy for enhancing the luminescent performance of COFs and expands their potential utility in chemical sensing and optoelectronic applications.