A functional anionic metal–organic framework for selective adsorption and separation of organic dyes

A 3D porous anionic MOF, {[(CH3)2NH2][Zn6(μ3-OH)(μ4-O)(NSBPDC)5(H2O)2]·DMF·12H2O}n (Zn-1) (H2NSBPDC = 6-nitro-2,2′-sulfone-4,4′-dicarboxylic acid), has been synthesized and characterized. Zn-1 exhibits a rare 5-connected ‘sqp’ net and contains large 3D intersecting channels modified with functional groups. Notably, Zn-1 can adsorb cationic dyes selectively and effectively, even for large molecules including Rhodamine B and Crystal Violet. The influences of the constant time and initial concentration of MB on the adsorption capacity of Zn-1 have been studied in detail. Furthermore, the kinetic research indicates that the adsorption of MB matches well with the pseudo second-order model. In addition, the material of Zn-1 is reusable, and the adsorbed dye (MB) can be released in saturated DMF/ethanol solution of LiNO3.