Efficient Luminescence Detection of Phenylglyoxylic Acid over Two Novel Zinc-Based MOFs Constructed by Aromatic Tetracarboxylic Acids

Phenylglyoxylic acid (PGA), the metabolite of styrene after its invasion into the human body, must be monitored conveniently and accurately. Herein, two zinc-based metal–organic frameworks {[Zn(H2L)bimb]}n (Zn-1) and {[Zn2(H2L)2bipd]}n (Zn-2) [H4L = 1,2,4,5-tetrakis(4-carboxyphenyl)-3,6-dimethyl-benzene, bimb = 1,1-(1,4-butanediyl)bis(imidazole), and bipd = 3,5-bis(1-imidazole)pyridine] had been obtained by the solvothermal method and could be used for selective detection of PGA with an extremely low detection limit. Single-crystal X-ray diffraction analyses revealed that Zn-1 exhibits a 2D topological framework with the point symbol (66), whereas Zn-2 shows a 2D framework with a (324.436.56) topology. Fluorescence detection proved that Zn-1 and Zn-2 had obvious quenching effects on PGA, the metabolite of styrene after its invasion into the human body. Impressively, Zn-1 and Zn-2 not only gave short response times (less than 5 s) but also exhibited relatively low limit of detections for PGA in water and simulated urine (1.44, 0.50 and 1.63, 1.14 μM, respectively). Meanwhile, Zn-1 and Zn-2 exhibited high stability, excellent anti-interference ability, and recyclability, making them promising sensors for the practical detection of PGA. Moreover, density functional theory calculation showed the photoinduced electron transfer mechanism, resulting in the fluorescence quenching; meanwhile, the photocompetitive absorption processes of ligands and PGA can also affect the emission of Zn-1 and Zn-2.