A novel thiazole-based covalent organic framework as turn-off fluorescent sensor for detection of aniline and triethylamine in liquid and vapor phase

Due to the diverse chemical structures and varying basicity of amines, the development of rapid, portable, and reversible methods for the selective recognition of trace organic amines in the environment remains a challenge. Herein, a novel recyclable and selective turn-off fluorescent sensor for organic amines detection based on covalent organic framework (COF) was developed. As-synthesized COF, TAPB-BTDD exhibits good crystallinity, high chemical stability and strong fluorescence, which can selectively recognize triethylamine (TEA) and aniline in both liquid and vapor phase. The COF material demonstrates impressively low LOD values for aniline and triethylamine in solution, estimated to be 27 nM and 170 nM, respectively. Moreover, when detecting aniline and triethylamine vapors, the calculated LOD values are 20.1 ppb and 106.4 ppb, respectively. In addition, TAPB-BTDD showed basically unchanged emission intensities and rapid response to the amines after ten recycling tests, suggesting that the COF has high stable recycle repeatability. The combination of experimental analysis and density functional theory (DFT) calculations demonstrates that the unique fluorescence-quenching response of TAPB-BTDA can be attributed to the photoinduced electron transfer (PET) between the amines and the COF. This COF-based sensor offers a promising solution for the accurate and reliable detection of organic amines in various environmental settings.