Evaluation of the Potential of a Ratiometric Fluorescence Sensor for Sensitively Recognizing 1-Hydroxypyrene in Real Urine Samples Based on a Stable Zn-MOF

In the work, a 3D Zn-based MOF, [CH₃(NH₂)₂][Zn₂(obdb)(OH)]·DMF (compound 1) has been formed successfully through the self-assembly of Zn(II) ion and organic linker H₄obdb (4',4‴-oxybis[1,1'-biphenyl]-3,5-dicarboxylic acid, a high-symmetrical tetra-carboxylate ligand) under solvothermal conditions. In the structure of compound 1, Zn and the symmetry-generated ones constitute a tetra-nuclear cluster [Zn₄(μ₂-COO)₈(μ₃-OH)₂], and then by the coordination of tetra-nuclear clusters and the organic linkers, a 3D stair-like framework containing a 1D rectangular channel with the porosity of 47.3% is generated. Interestingly, compound 1 is confirmed to possess striking air and pH stability. Noteworthily, the results of detecting studies certify that compound 1 can serve as a prospective ratiometric fluorescence sensor for selectively recognizing 1-hydroxypyrene (1-HP) among diverse urine components and a promising fluorescence probe for Asp from other 11 kinds of amino acids depended on "turn-off" effects decorated with high quenching efficiencies (97.5% for 1-HP and 94.3% for Asp) and outstanding sensitivity with K_sv values of 1.84 × 10⁵ M^-1 for 1-HP and 1.41 × 10⁴ M^-1 for Asp in a DMF-H₂O binary system. Amazingly, the sensing capacities of compound 1 maintain similar levels in fresh human urine compared with those in the DMF-H₂O binary system, giving the K_sv values of 5.79 × 10⁴ M^-1 for 1-HP and 1.72 × 10⁴ M^-1 for Asp.