A bisimidazolium-based cationic covalent triazine framework for CO2 capture and dye adsorption

In this work, an aromatic nitrile containing the pyrimidine moiety and bisimidazolium cations (PyImCl) was synthesized and subsequently employed to prepare a bisimidazolium-based cationic covalent triazine framework (PyImCl-cCTF) through the ionothermal trimerization reaction. The chemical composition and structure of PyImCl-cCTF were carefully revealed by a series of techniques. As examined by N-2 sorption isotherms at 77 K, PyImCl-cCTF exhibited large surface area and abundant microporous structures. Together with the high content of imidazolium cations derived from the bisimidazolium-based monomer, PyImCl-cCTF showed high CO2 uptake capacity of 235 and 133 mg/g at 1 bar under 273 and 298 K, respectively, superior to the previously reported cCTFs. The dye adsorption performance of PyImCl-cCTF was performed for commonly used dyes. Surprisingly, PyImCl-cCTF exhibited a certain removal effect on both anionic and cationic dyes. Moreover, PyImCl-cCTF with the positively charged skeleton can quickly remove anionic dyes through electrostatic interactions, showing almost 100% removal efficiency within 20 min. These results demonstrate that PyImCl-cCTF can behave as an efficient adsorbent for both CO2 capture and dye removal to solve environmental problems.