Zr(IV)-Based Metal-Organic Framework with T-Shaped Ligand: Unique Structure, High Stability, Selective Detection, and...

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″-(1 H-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 BTBA^3- 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 Cr₂O₇^2- selectively, at a low concentration and a short response time (<1 min). Simultaneously, it also exhibits excellent capacity to rapidly capture Cr₂O₇^2- (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 Cr₂O₇^2- detection in and removal from water.