Porous Organic Frameworks Constructed by the Synergetic Effect of Covalent Bonds and Hydrogen Bonds for the Selective Identification and Detection of Explosives
Chao Zhang, Fuxing Sun, Yi He
Abstract
Covalent organic frameworks (COFs) and hydrogen-bonded organic frameworks (HOFs) have emerged as novel platforms for material design and functional explorations. Here, we report an unconventional structural organic framework (named CHOF-1) combined with 1,3,5-tris(4-aminophenyl)benzene (TAPB) and 5-hydroxyisophthalaldehyde (HP) through the synergetic effect of covalent bonds and hydrogen bonds. CHOF-1 contains two different pores and is an eclipsed AA-stacking model with high thermal stability. It exhibits selective “turn-off” and red shift fluorescence responses toward 4-nitrophenol (4-NP) and 2,4,6-trinitrophenol (TNP) in ethanol, respectively, and the low detection limit was 8.78 μM for 4-NP and 11.1 μM for TNP. It has satisfactory recovery in the detection of 4-NP and TNP in practical water samples. The fluorescence quenching of CHOF-1 caused by 4-NP is attributed to the absorption competition quenching (ACQ) mechanism. In the structure of CHOF-1, the hydroxyl of TNP has strong acidity and can form strong hydrogen bonds with the unreacted NH 2 . Then, the crystalline structure of CHOF-1 decomposed and the electron structure of the photophore changed; thus, the fluorescence spectra red-shifted. This is a novel example of a covalent bond and hydrogen bonds combined organic framework (CHOF). This work not only demonstrates a synthesis strategy of the first novel structural organic framework through the synergetic effect of covalent bonds and hydrogen bonds but also provides a fluorescent sensing material for the detection of explosives 4-NP and TNP with high selectivity and sensitivity.