A Fluorescent Anionic MOF with Zn₄(trz)₂ Chain for Highly Selective Visual Sensing of Contaminants: Cr(III) Ion and TNP

Abstract

Heavy-metal ions and nitroaromatic substances are highly toxic and harmful to human health and the ecological environment. It is an urgent issue to selectively detect and capture these toxic substances. By introducing the triazole ligand to the π-conjugated aromatic carboxylate system and borrowing the organic template open framework idea, a stable fluorescent framework [Me₂NH₂]₄[Zn₆(qptc)₃(trz)₄]·6H₂O (1) (H₄qptc = terphenyl-2,5,2'5'-tetracarboxylic acid, trz = 1,2,4-triazole) has been successfully synthesized, which features Zn₄(trz)₂ chain-based 3D anionic structure with channels filled by [Me₂NH₂]⁺ cations. It is worth noting that the material exhibits selective adsorption and recyclable detection of heavy-metal Cr³⁺ ion in aqueous solutions, which may be the synergy from the metal charge, bond ability of metal ions to carboxylate oxygen atom, and soft-hard acid-base properties. Furthermore, it can selectively sense of 2,4,6-trinitrophenol with a large quenching coefficient K_sv of 2.08 × 10⁶ M^-1.