Tunable ABC-stacked fluorescent covalent organic frameworks for nitroaromatic detection

By precisely controlling the solvent type and ratio, a kagome ABC stacking fluorescent covalent organic framework ET-BF-COF was synthesized. This framework exhibits significant fluorescence sensing properties upon NACs, as well as superior selectivity and sensitivity. • A fluorescent covalent organic framework (ET-BF-COF) with high crystallinity has been synthesized. • The stacking mode of COF can be regulated, and a kagome ABC stacking ET-BF-COF was achieved. • ET-BF-COF exhibits remarkable fluorescence sensing properties, selectivity and sensitivity towards NACs. A kagome ABC stacking fluorescent covalent organic framework (ET-BF-COF) has been synthesized by precisely controlling the solvent type and ratio, using 4,4′,4′’,4′’’-(ethene-1,1,2,2-tetrayl)tetraaniline (ETTA) and 9,10-bis(4-formylphenyl)anthracene (BFA) as raw materials. ET-BF-COF demonstrates a large specific surface area, excellent crystallinity and thermal stability. The potential application of ET-BF-COF in fluorescent sensing was systematically investigated. ET-BF-COF possesses significant fluorescence quenching properties toward nitroaromatic compounds (NACs), particularly p-nitrophenol (4-NP) and o-nitrophenol (2-NP), exhibiting high selectivity and sensitivity. The Stern-Volmer quenching constant ( K sv ) of 4-NP and 2-NP was determined to be 1.76 × 10 5 and 7.23 × 10 4 M −1 , with a detection limit of 0.23 and 0.36 μM, respectively. Density functional theory (DFT) calculations indicate that the fluorescence quenching behavior of ET-BF-COF towards NACs is primarily governed by the donor photoinduced electron transfer（d-PET）mechanism. This study not only achieved controlled stacking of Covalent Organic Frameworks (COFs) through precise regulation of solvents and their ratios but also prepared a fluorescent chemical sensor with high sensitivity and selectivity for the detection of nitroaromatic compounds (NACs).