A mesoporous metal-organic framework: Potential advances in selective dye adsorption

A new metal-organic framework based on manganous (II) ions and a paddle wheel ligand, H3[Mn3O3(BTB)] (Mn-BTB, HBTB = 1,3,5-tris(4-carboxyphenyl)benzene acid), was synthesized and structurally characterized. Mn-BTB was formed via self-assembly of one-dimensional (1D) helical chains interconnected through the carboxyl groups of the tripodal ligand HBTB to generate a 3D, extended network with a nanotube-like architecture and aperture size of 18.22 A × 16.40 A. The 2-fold self-interpenetration significantly enhanced the stability of the framework, although it minimized the empty space to some extent. Mn-BTB contains an accessible volume of 3143.6 A3 with a 47.1% porosity, which allowed the adsorption of large dye molecules. Cationic dyes (methylene blue (MB) and rhodamine B (RhB)) and an anionic dye (methyl orange (MO)) were examined for selective dye adsorption on Mn-BTB. Mn-BTB with an anionic skeleton was beneficial for the selective adsorption of cationic dyes.