Novel imine-linked covalent organic frameworks: preparation, characterization and application

Covalent organic frameworks (COFs) have attracted considerable interest over the past few years, but the available type of monomers is still limited. Herein, two novel imine-linked COFs (TaDAP and TaDA) were constructed by the condensation of 1,3,5-tris-(4-aminophenyl) triazine with 2,6-diformylpyridine (forming TaDAP) and 1,3-benzenedialdehyde (forming TaDA) under solvothermal conditions. The structures of the COFs were confirmed and characterized by solid state C-13 NMR, FT-IR, PXRD, TGA, SEM, TEM and nitrogen sorption isotherms. They appear as regular spherical particles and possess excellent thermal stability. It was also found that their dispersions emit strong fluorescence, and display quick response to certain metal ions. In particular, TaDAP can detect Fe3+ with sensitivity and selectivity. Moreover, both the COFs present excellent catalytic activity towards the Knoevenagel reaction. Accordingly, this study not only provides a new way to enrich the family of COFs, but also develops their potential applications in metal ion detection.