Controllable preparation of amino-functionalized ZIF-8: A functionalized MOF material for adsorbing Congo Red and Eriochrome Black T in aqueous solution

Zeolitic imidazolate framework (ZIF) was a new class of MOF with metal ions and imidazole ligands and had a series of practical applications in the water environment. In-depth study of amino-functionalized ZIF-8 to adsorb organic dyes is valuable in aqueous solutions. In this study, two-solvent strategy of methanol and ammonia was used to synthesize four different ZIF-8s (denoted as ZIF-8-A, ZIF-8-B, ZIF-8-C, ZIF-8-D) with different particle sizes. The synthesized ZIF-8 were characterized by FT-IR, XRD, SEM etc. By comparing the difference in removal effect of four different particle size ZIF-8 materials on Congo Red (CR) and Eriochrome Black T (EBT) solutions, a high-efficiency adsorbent (ZIF-8-D) was selected for the subsequent research. Further the modified Stöber method was used to modify ZIF-8-D with amino-functionalization. The research result showed that the adsorption capacity of NH2-ZIF-8-D for CR may be as high as 653.59 ​mg ​g-1, which effectively increased the adsorption efficiency by 27.5% compared with ZIF-8-D. At the same time, NH2-ZIF-8-D also showed an adsorption capacity of 279.32 ​mg ​g-1 for EBT. And the fifth repetitive utilization rate of the functionalized material for adsorbing the two dye solutions is kept above 84%. Therefore, the new NH2-ZIF-8-D material has excellent efficiency and reusability and showed great potential for removing organic dyes from water.