The construction of the flexible covalent organic frameworks with phenyl sulfide as linkers used for adsorping iodine and fluorescence sensing picric acid

The efficient capture of radioactive iodine and sensitive detection of picric acid are very important to environmental protection. Herein, we synthesized two new flexible 4,4′-thiodianiline (TDA)-based covalent organic frameworks (TTDA and HTDA) by using simple Schiff-base polycondensation reactions with flexible 4,4′-thiodianiline (TDA) and 2,4,6-tris(4-formylphenoxy)-1,3,5-triazine (TPT − 3 − CHO) and hexa(4-formyl-phenoxy)cyclotriphosphazene (NOP − 6 − CHO). The flexible TDA-based COFs are porous, crystalline, and show high thermal stability and good chemical stability. Due to the high content of heteroatoms, abundant aromatic rings, and orderly network, it is conducive to electron transfer, the as-prepared flexible TDA-based COFs show outstanding dual properties of iodine adsorption and fluorescence sensing. The maximum iodine capacities of TTDA and HTDA are as high as 3.34 and 4.38 g g−1, respectively. The flexible TDA-based COFs can be used for sensing picric acid with low limits of detection (LODs) of 1.25 × 10−9 and 1.67 × 10−9 mol L−1 and high quenching constants (KSV) of 6.00 × 104 and 4.88 × 104 L mol−1, respectively. •Two new flexible TDA-based COFs with dual functions of iodine adsorption and fluorescence sensing PA were synthesized by Schiff base reaction.