Preparation of covalent triazine-based framework for efficient Cr(VI) removal from water

Abstract

To overcome problems associated with heavy metal pollution, lots of new functional materials have been used. As potential emerging environmental materials, covalent triazine frameworks (CTFs) have received extensive attention because of their high nitrogen content and the feature of pre-design to obtain the required molecular framework for specific applications. In this study, three CTFs were synthesized by terephthalonitrile (TPA) with the catalyzer of ZnCl2 under different temperatures from 300 °C to 500 °C. Preparation temperature significantly affected the adsorption kinetics and capacity of CTFs. The CTF prepared under 500 °C (CTF500) showed the highest Cr(VI) adsorption capacity of 97.84 mg g−1. The CTF500 was characterized with three different types of N, including pyrrolic N, pyridinic N, and quaternary N, thus providing support for the efficient adsorption of Cr(VI) from water. The mechanism of Cr(VI) removal was verified by a strong ion exchange interaction driving with the structure of quaternary N on CTF500. In addition, CTF500 also showed a stable Cr(VI) removal rate under a high ionic strength surrounding. In this study, CTFs with pre-designed functional groups could efficiently remove Cr(VI) by controlling their synthesis progress and showed great potential in future environmental applications.