One-step synthesis of a benzothiadiazole-based nonbranching functionalized covalent organic framework and its application in efficient removal of Hg2+

Abstract

In recent years, a variety of adsorbents have been developed for Hg²⁺ removal. However, these adsorbents are unsatisfactory for adsorption due to narrow and irregular pore channels or poor adsorption capacity and low stability. Therefore, it is worth exploring a porous Hg²⁺ adsorbent material with high adsorption performance and stability. In this study, a benzothiadiazole-based nonbranching functionalized covalent organic framework (COF) material (TPS-COF) by one-step synthesis was reported, which exhibited a high specific surface area of 1564 m² g⁻¹, high crystallinity and stability attributed to its high conjugated linkage structure of benzothiadiazole. In addition, due to the rich S and N elements of the benzothiadiazole unit, it exhibited excellent adsorption performance on Hg²⁺, including excellent adsorption amount (1040 mg g⁻¹), high initial adsorption rate (448 mg g⁻¹ min⁻¹) and very short adsorption equilibrium time (10 min), with an efficient removal rate of Hg²⁺ in the pH range of 2–8. After desorption, the TPS-COF still retained good pore stability, adsorption capacity, and reusability. Such a one-step synthetic unbranched functionalization strategy provides further insights to achieve a good balance between the high crystallinity, functionality and stability of COFs.