A Triazine-Based Cationic Covalent Organic Framework as a Robust Adsorbent for Removal of Methyl Orange

Abstract

In comparison with neutral covalent organic frameworks (COFs), few studies have been conducted on the synthesis and applications of ionic COFs. In this work, a novel cationic covalent organic framework (CCOF) with high porosity and crystallinity is synthesized by reacting ionic tris-aldehyde with 4,4'-oxydianiline through the catalyst-free Schiff’s base reaction. The structural properties of cationic COF were characterized by Fourier-transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HR-TEM), Atomic force microscopy (AFM), thermogravimetric analysis (TGA), and Brunauer-Emmett-Teller (BET) surface area analysis. Application of this cationic COF as an adsorbent for selective removal of anionic dyes with sustainability concerns is investigated. The synthesized cationic COF exhibited good removal efficiency (95%) for methyl orange. The adsorption process was exothermic and fitted perfectly with the Langmuir isotherm with a high correlation coefficient (R² = 0.9737) and maximum adsorption capacity (196.08 mg/g) and pseudo-second-order kinetic model.

Graphical Abstract

Keywords:

• Cationic covalent organic framework
• water treatment
• anionic dyes removal
• azo dyes
• ion exchange
• adsorption

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Data availability statement

The spectroscopic data including FT-IR, ¹H- NMR and ¹³C-NMR spectra for all compounds, that supports the findings of this study, are available in the supplementary material.

Additional information

Funding

We gratefully acknowledge the financial support of this work by the research council of Arak University.