Highly crystalline covalent organic frameworks for ratiometric fluorescent sensing of trace water in honey and N2 gas

The detection of trace water (H 2 O) content is important and challenging in food and food-related industries. Herein, highly crystalline two-dimensional covalent organic frameworks (TAPT-BTCA-COF) with yellow-green fluorescence were prepared by using 1,3,5-tris(4-aminophenyl)triazine (TAPT) and 1,3,5-benzenetricarboxaldehyde (BTCA) as precursors. The fluorescence of TAPT-BTCA-COF is sensitive to the solvent polarity due to the intermolecular charge transfer (ICT) effect and can be quenched by trace H 2 O due to the block of ICT effect by H 2 O. On this base, TAPT-BTCA-COF is applied for sensing of trace H 2 O in common organic solvents such as DMF, acetonitrile , THF and acetone with fast response and high sensitivity. The limits of detection for H 2 O in DMF, acetonitrile, THF and acetone are 0.082 wt%, 0.0053 wt%, 0.0091 wt% and 0.0061 wt%, respectively. Furthermore, a ratiometric fluorescent sensor is proposed by using TAPT-BTCA-COF as the signal probe and red fluorescent tris(2,2′-bipyridyl)ruthenium(II) dichloride as the reference and successfully applied for quantitatively and semi-quantitatively sensing of trace H 2 O in honey sample and the moisture in N 2 gas.