A porous zinc(II) metal–organic framework exhibiting high sensing ability for ferric and nitroaromatics as well as photocatalytic degradation activities against organic dyes

A NbO-type Zn(II) metal–organic framework of {[Zn₂(HL)(H₂O)₂]∙H₂O}_n (1) has been developed using a pentacarboxylate 2,5-bis(3′,5′-dicarboxylphenyl)-benzoic acid (H₅L) ligand and characterized. The single-crystal X-ray diffraction studies indicate that 1 comprises free –COOH groups and Zn(II) centers bridged by four carboxylate groups to form a paddle wheel SBU which is further connected by L⁵⁻ ligands to build a 3-D porous network with two types of cages. The chemically stable MOF 1 behaves as a highly selective and sensitive fluorescent chemosensor for the detection of Fe³⁺ ions, 2,4,6-trinitrophenol (TNP), which is known to be an extremely hazardous and strong explosive. Furthermore, the photocatalytic properties of 1 for degradation of methyl violet (MV) and Rhodamine B (RhB) have been explored. The possible emission quenching mechanism in the presence of nitro-aromatics (NACs) has been addressed by theoretical calculations and photocatalytic activity of 1 against organic dyes has been supported using density of states (DOS) calculations.