Highly effective and fast removal of anionic carcinogenic dyes via an In3-cluster-based cationic metal–organic framework with nitrogen-rich ligand

Abstract

In this work, highly effective and rapid removal of anionic carcinogenic organic dye molecules is achieved through the use of a novel cationic metal–organic framework (MOF). The MOF is constructed using a nitrogen-rich triangular organic ligand, 4,4′,4′′-s-triazine-1,3,5-triyltri-p-aminobenzoate (H₃TATAB), and trinuclear 6-connected In₃-cluster secondary building units (SBUs), [In₃O(TATAB)₂(H₂O)₃](NO₃)·(DMA)₁₅ (In-TATAB), which gives a structure exhibiting a new topology. As the formula indicates, In-TATAB is inherently cationic due to the [In₃O(COO⁻)₆]⁺ units, which thus favors interaction with anionic guests. Several organic dye molecules of varying charge and size, such as acid chrome blue K, acid red 26, congo red, direct black 38 and, orange II, were used to test the sequestration potential of the MOF material. In addition to electrostatic attraction, it is shown that hydrogen-bonding originating from the highly functional bridging ligand and terminal H₂O ligands enhance the interactions between the framework and guest dye molecules, suggesting its potential use for the removal of anionic organic pollutants.