A porous anionic zinc(ii) metal–organic framework for gas adsorption, selective uptake of dyes and sensing of Fe3+ by Tb3+ ion encapsulation

Abstract

A three-dimensional (3D) metal–organic framework [(CH₃)₂NH₂][Zn₂(DMTDC)₂(3-mtz)]·4DMF·3H₂O (Zn-MOF) has been solvothermally synthesized by using mixed ligands of 3-methyl-1,2,4-triazole (3-Hmtz) and a thiophene-functionalized dicarboxylate ligand, 3,4-dimethylthieno[2,3-b]thiophene-2,5-dicarboxylic acid (H₂DMTDC). Zn-MOF exhibits a uninodal 6-connected pcu α-Po topology structure and possesses an anionic framework with large 1D-trapezoidal channels. Gas adsorption studies reveal that the activated Zn-MOF-a displays selective adsorption of CO₂ over N₂ at 273 K and 298 K as well as a high isosteric heat of CO₂ adsorption. Moreover, Zn-MOF shows selective adsorption of the cationic dyes over the anionic and neutral dyes, and can be used as a fast-response and sensitive probe for the detection of Fe³⁺ by fluorescence quenching after encapsulation of Tb³⁺ into the pores by postsynthetic cation exchange.