Thiosemicarbazide-Linked Covalent Organic Framework: Preparation, Properties and Applications

With the unique advantages in structure and property, covalent organic frameworks have been widely employed for separation and enrichment. In this work, the thiosemicarbazide-linked covalent organic framework (TpTc) was prepared by using 1,3,5-triformylphloroglucinol and non-rigid thiosemicarbazide as building blocks for the first time. The as-prepared TpTc COF was fully characterized, presenting an agaric-like structure, large specific surface area (63.5 m(2) g(-1)), uniform pore size distribution (1.36 nm), inherent porosity and ordered crystallinity. The potential of TpTc as adsorbent for metal ions capture was investigated by static batch adsorption experiment using the one-factor procedure. The maximum adsorption capacities of 73.50, 56.53 and 94.13 mg g(-1) were obtained for Cu (II), Pb (II) and Cd (II) at natural pH, respectively. The anchoring of three metal ions onto TpTc is a multi-layer sorption involving chemical adsorption, and obeys the Freundlich and pseudo-second-order model. According to XPS analysis, the adsorption mechanism may be attributed to the coordination and electrostatic interaction between metal ions and N, O and S atoms on TpTc COF. This work not only provides a candidate for the application of COFs in metal ions capture, but also a reference for exploring functional design of COFs.