Acid and alkalinity stable pillared-layer and fluorescent zinc(II) metal–organic framework for selective sensing of Fe3+ ions in aqueous solution

The pillared-layer Metal–Organic Framework (MOF) enjoys good tunability and rich functionality, yet highly relies on rational combination of mixed ligands. A new MOF formulated as [Zn2(trz)2(btdb)]·4DMF (1, trz = 1,2,4-triazole, H2btdb = 4,4′-(benzo[c][1,2,5]thiadiazole-4,7-diyl) dibenzoic acid) is constructed from a [Zn2] node based (4,4)-grid layer that pillared by inclined a highly fluorescent dicarboxylate linkers. The rigid [Zn2(trz)2] layer coupled with hydrogen bonding encompassed Zn-carboxyl linkage endow the MOF desired high stability. The crystalline structure of 1 maintains well in harsh conditions including pH = 3 HCl and pH = 12 NaOH aqueous solution for more than 24 h. With high void fraction of 42.7%, the interconnected 3D channels sized at 4.0–8.8 Å guarantee sufficient exposure of thiadiazole in the pillar ligand as potential sensing site. With bright fluorescence of 1, Fe3+ ions can be selectively and specifically detected in both aqueous and non-aqueous solution through quenching mechanism, given a detection limit of 3.1 and 17.0 μM in methanol and H2O solution, respectively.