Xiao-Zhen Kang¹, Zheng-Wei Song², Qi Shi^1,* and Jin-Xiang Dong^1,*

¹Research Institute of Special Chemicals, Taiyuan University of Technology, Taiyuan 030024, Shanxi Province, P.R. China

²Department of Coal Chemical, Yili Institute of Technician Training, Yili 835000, Xinjiang Province, P.R. China

*Corresponding authors: Tel./Fax: +86 351 611178; E-mail: shiqi594@163.com; dongjinxiangwork@hotmail.com

In this work, we have described the adsorption of dye acid blue 40 and methylene blue from aqueous solution onto isotypic zeolite imidazolate frameworks (ZIFs) such as ZIF-8 [Zn(mim)₂] and ZIF-67 [Co(mim)₂]. The results suggested that the charged sites at the external surface of zeolite imidazolate frameworks play a key role in dye adsorption. A similar adsorption capacity is observed for the uptake cationic dye methylene blue between ZIF-8 and ZIF-67, involving electrostatic interactions between the same N-extremities (belonging to mim linkers) and positively charged methylene blue. For anionic dye acid blue 40, the adsorption capacity for ZIF-67 is nearly three times higher than that of ZIF-8, involving electrostatic interactions between low-coordinated metal cations of zeolite imidazolate frameworks and negatively charged groups of acid blue 40 and Co cations in ZIF-67 have higher affinity with the SO₃^– groups of acid blue 40.

Adsorbent, Dye, Liquid phase adsorption, Metal-organic frameworks, External surface.