Fabrication of covalent organic frameworks and its selective extraction of fluoronitrobenzenes from environmental samples.

ABSTRACT

In this study, porous covalent organic frameworks (COFs, named as COFs-SWMU) were synthesized for the first time via a facile approach by using 4,4',4''-methylidynetri-anilin and 2,5-dihydroxy-1,4-benzenedicarboxaldehyde as precursors under ambient temperature. The COFs-SWMU were characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy, thermogravimetric analysis, etc. The COFs-SWMU exhibited a relatively high specific surface area and desirable thermal stability. The adsorption performance of COFs-SWMU towards fluoronitrobenzenes (FNBs, including 1-fluoro-2-nitrobenzene, 1-fluoro-3-nitrobenzene, 1-fluoro-4-nitrobenzene, 2,4-difluoronitrobenzene, 3,4-difluoronitrobenzene, and 3,4-dinitrofluorobenzene) was investigated on the basis of adsorption capacity and partition coefficient (PC). The adsorption kinetics and isotherm of COFs-SWMU for FNBs were studied in detail. Further, a simple, fast and sensitive method which combined COFs-SWMU based extraction with high-performance liquid chromatography-diode array detection, was proposed for the analysis of FNBs in environmental samples. Desirable linearity (R2>0.9998) in the range of 0.1-100 µg•mL-1, low limits of detection (LODs; 0.1‒0.15 µg•mL‒1), low limits of quantitation (LOQs; 0.28‒0.40 µg•mL‒1), and desirable precision (RSDs, 0.24-2.83% for intraday and 1.13-6.92% for interday) are obtained. Finally, the COFs-SWMU were applied to the effective extraction of FNBs from environmental samples, and desirable recovery results were obtained.