Thermal alkyne–azide cycloaddition enables the fabrication of fluorescent COF thin films for sensitive chemical warfare agent sensing

Abstract

The development of efficient and reliable detection materials for toxic chemical warfare agents (CWAs) has garnered significant attention, given the severe threat these substances pose to human health and public safety. Fluorescent porous thin films represent a highly promising platform for achieving high-performance CWA sensing. However, achieving both high luminescence efficiency and a porous thin film morphology concurrently remains a major challenge for sensing films. In this work, we report the fabrication of fluorescent covalent organic framework (COF) thin films by incorporating fluorescent porphyrin guest molecules into COFs via thermal alkyne–azide cycloaddition, and demonstrate their application in the detection of the CWA simulant diethyl chlorophosphate (DCP). Owing to the intrinsic porosity of the COFs, the resulting thin film exhibits an ultralow limit of detection (0.21 ppb) and a rapid response time (2.4 s), ranking among the most sensitive DCP sensors reported to date. Furthermore, the fluorescent COF shows nearly tenfold higher DCP adsorption capacity (619 mg g⁻¹) compared to the porphyrin guest molecules (66 mg g⁻¹) alone. This study not only establishes a generalizable synthetic strategy for the preparation of fluorescent COF thin films, but also underscores their great potential for high-performance sensing of CWAs.