Highly sensitive and selective detection of chromate and dichromate by a luminescent thorium metal-organic framework

Abstract

The rapid detection of the aqueous chromates and dichromates is necessary because of their chemical toxicity and the potential threat to the environment. Luminescent metal–organic frameworks have been developed to detect a variety of ions, but the chemical stability of most MOFs is not enough to remain intact in aqueous solution. Herein, a solvothermal reaction based on thorium salt and tetraphenylethene-functionalized ligand (E)-4,4′-(1,2-diphenylethene-1,2-diyl)dibenzoic acid (H2BCTPE) produces a new porous metal–organic framework with the formula [Th6(μ3-OH)4(μ3-O)4(BCTPE)6(H2O)6]·(DMF)15(H2O)29 (Th-BCTPE). It was characterized by SC-XRD, PXRD, TGA, nitrogen adsorption, and fluorescence spectrum. Bearing with high chemical stability as well as high photoluminescence quantum yields, Th-BCTPE exhibited sensitive and selective detection towards Cr(VI) oxyanions via fluorescence quenching. The KSV towards chromate and dichromate are 9.6(3) × 104 M−1 and 1.67(4) × 105 M−1, while the limits of detection are low to 131.8 nM (linear range: 0 to 20 μM) and 75.7 nM (linear range: 0 to 27 μM), respectively. Particularly, the response time of Th-BCTPE@PVDF membrane towards both of the Cr(VI) oxyanions is less than 5 s. Our findings demonstrate that Th-MOFs is a promising luminescent sensor on account of its chemical stability, excellent detection efficiency and quick response.