A cationic metal-organic framework for dye adsorption and separation based on column-chromatography

Dyes that are considered to be poisonous exist everywhere in our daily life. The most urgent task is to remove such dye molecules from effluents. In the present work, a cationic metal-organic framework, [Cd2(tib)(btb)(H2O)2]∙NO3∙2DMF (Cd-MOF), where charge neutrality is balanced by NO3−, was first synthesized to investigate its ability in the adsorption and separation of ionic dye molecules. It is found that anionic dye molecules can be efficiently adsorbed with a diverse adsorption rate, while neutral and cationic dye molecules cannot be adsorbed according to the color changes of Cd-MOF. Meanwhile, Cd-MOF serves as a column-chromatographic filler to adsorb and separate specific anionic dye molecules with visible effects. Furthermore, anionic dye molecules can be released gradually, and the release rate is faster in the presence of NaCl. It should be noted that Cd-MOF remains stable even after 6 cycles of adsorption and separation of ionic dye molecules, which implies that MOFs can be considered potential materials for dye adsorption and selective separation with the merits of convenience, rapidity and environmental friendliness.