Fabrication of high-crystallinity covalent organic framework and its nylon based membrane: Application in the enrichment and interception of dyes

Because of their high carcinogenicity and mutagenicity, dyes pose a great threat to the environment and humans, and the development of highly efficient dye removal methods is of great significance. Herein, a novel fluorine-rich COF (TPTF-COF) with high crystallinity was synthesized by connecting 1,3,5-tris(4-aminophenyl) benzene (TPB) and 1,3,5-tri(3-fluoro-4-formylphenyl) benzene (TF) at room temperature using acetonitrile as solvent. Owing to its large specific surface area (1084.61 m(2)center dot g(-1)), high crystallinity, high thermal stability, and rich functional group properties, TPTF-COF showed good adsorption capacities (20.63-386.30 m(2)center dot g(-1)) for six selected dyes. Based on TPTF-COF, a six-well plate assisted in-situ assembly method that can achieve the simultaneous synthesis of six sheets of TPTF-COF-based nylon membranes at a relatively low temperature (40 degree celsius) and within a short reaction time (48 h) was developed using aminodized nylon membrane as supports. The membrane with good uniformity showed high adsorption for the selected dyes, and thus showed good rejection, especially for Congo red (rejection >94%). Owing to the large gap between the aminodized nylon membranes, the TPTF-COF-based nylon membrane also exhibited superior water flux. The results of experimental and computational studies revealed that the pore size selectivity of TPTF-COF, pi-pi interaction, hydrogen bond and electrostatic interactions between TPTF-COF and dyes led to these selective adsorption effects. In this study, a new six-well plate assisted in-situ synthesis strategy for the preparation of imine-linked COF-based nylon membranes for dye removal, was developed. This approach may establish a viable route for the high-throughput and gentle fabrication of COF-based membranes for various applications.