Two novel zinc-based MOFs as luminescence sensors to detect phenylglyoxylic acid

Automobile exhaust gases, plastic pollutants, smoking, and other harmful substances can cause serious harm to human beings and the environment. Styrene, as a common airborne toxin, enters the human body through breathing or the skin and is discharged in the form of phenylglyoxylic acid (PGA). Therefore, specific, sensitive and trace detection of PGA is particularly important. Here, two zinc-based metal-organic frameworks {[Zn₂L₁(DMF)₂H₂O](DMF)₂H₂O}, {[Zn₄(L₂)₂(DMF)₂(H₂O)₃](DMF)₈} (L₁ = 2,5-bis((3-carboxylphenyl)amino)terephthalic acid, L₂ = 2,5-bis((4-carboxyphenyl)amino)terephthalic acid) have been reported as 1 and 2, respectively. Both 1 and 2 present 3D structures, which can both be simplified as 4,4,4-c net topology. It is worth mentioning that 2 has two different kinds of Zn SBUs as connecting nodes in the structure. Besides, compared with the other materials for the detection of PGA, 1 and 2 exhibit relatively low detection limits (LODs), both in water and in urine (where the LODs for 1 in water and urine were 0.33 μM and 0.43 μM in the range of 0-0.39 mM, and those for 2 were 0.28 μM and 0.49 μM in the range of 0-0.59 mM, respectively). In addition, the sensors have excellent anti-interference ability, high stability, rapid response, and can easily distinguish between different concentrations of PGA with the naked eye. The developed paper probes were suitable for practical sensing applications for portable detection of PGA in urine.