Zr(IV)-Based Metal-Organic Framework with T‑Shaped Ligand: Unique Structure, High Stability, Selective Detection, and Rapid Adsorption of Cr2O72– in Water

Dichromate is known for severe health impairments to organisms. New and valid strategies have been developed to rapidly detect and efficiently remove this pollutant. Constructing stable luminescent metal-organic frameworks (MOFs) for dichromate recognition and removal from aqueous solution could provide a feasible resolution to this problem. Herein, a new luminescent Zr­(IV)-MOF, Zr6O4(OH)7(H2O)3(BTBA)3 (BUT-39, BUT = Beijing University of Technology) was constructed through the reaction of a newly designed functionalized T-shaped ligand 4,4′,4″-(1H-benzo­[d]­imidazole-2,4,7-triyl)­tribenzoic acid (H3BTBA) with zirconium salt. BUT-39 has a unique porous framework structure, in which Zr6 cluster acts as a rare low-symmetric 9-connected node and BTBA3– as a T-shaped 3-connected linker. As far as we know, this represents the first case of a (3,9)-connected Zr­(IV)-MOF. BUT-39 could retain its framework integrity in boiling water, 2 M HCl aqueous solution, and pH 12 NaOH aqueous solution. Due to its good water stability and strong fluorescent emission, BUT-39 is then employed in fluorescence sensing for various ions in aqueous solution and shows good performance toward Cr2O72– selectively, at a low concentration and a short response time (2O72– (within 1 min) with a high uptake up to 1 mmol g–1. Taking advantage of its excellent stability, sensitive and selective sensing, as well as rapid and high adsorption, BUT-39 is expected to be useful in Cr2O72– detection in and removal from water.