Efficient removal of phenanthrene by covalent organic frameworks: An experimental combined with theoretical analysis

It is essential to find a green, efficient, and economical way to deal with polycyclic aromatic hydrocarbons (PAHs) that have a significant impact on human health and the ecosystem. In this study, two covalent organic frameworks (COFs) were prepared by using the Schiff base reaction for the effective removal of phenanthrene (PHE). The COFs were characterized by XRD, FT-IR, SEM, TEM, BET, and XPS. Meanwhile, the effects of pH, contact time, and different ionic strengths on the adsorption process were investigated. The results showed that the COFs had good adsorption performance on PHE. The most favorable bonding modes between the two COFs and PHE molecules were calculated and analyzed by Density Functional Theory, and the mechanism was explored in combination with XPS and FT-IR. This work reveals the potential of COFs as efficient adsorbents for the removal of organic pollutants from polluted water and provides further insight into the interactions present in the adsorption process. In addition, with the help of vacuum self-assembly, a simple and scalable strategy to construct assembled COFs membranes (PES@COFs), it was shown that PES@COFs membranes have good retention of PHE present in water and show the advantages of easy handling, better stability, reduced risk of secondary contamination of samples and good reusability. This work highlights the great application potential of COFs for the removal of PHE and demonstrates that the preparation of COFs monolithic materials by vacuum self-assembly is a simple and easy strategy to promote COFs in practical applications.