Construction And Recognition Performance Of Framework-based Fluorescent Sensing Materials

In response to the urgent need for rapid and sensitive detection of environmental pollutants as well as early diagnosis and routine monitoring of diseases.This study utilizes the diverse structures,large surface area,and modifiable pore characteristics of metal-organic framework（MOF）materials to construct five fluorescent sensing materials via a solvent-thermal method.The prepared materials were characterized for their structure,stability,and fluorescence sensing capabilities towards anions,antibiotics,and bioactive molecules.In addition,this thesis also investigated the structure-activity relationship and recognition mechanism of MOF-based fluorescent sensing materials,which will provide theoretical guidance for the directed synthesis and development of MOF-based fluorescent sensors.The main contents of this thesis are as follows:（I）The two MOFs{[Co（TPTC）_0.5（BIBP）]?H₂O}_n（Co MOF）and{（Me₂NH₂）[Zn（NH₂-TCB）]}_n（Zn MOF）with novel structures were designed and synthesized through organic aromatic ligands（[1,1’:4’,1’’-terphenyl]-2’,3,3’’,5’-tetracarboxylic acid（H₄TPTC）,2-amino-1,3,5-benzenetricarboxylic acid（NH₂-H₃TCB））and nitrogen-containing ligand（4,4’-biphenylimidazole（BIBP））self-assembly with metal ions under hydrothermal conditions.Structural analysis showed that Co MOF is a three-dimensional columnar layer structure constructed based on a binuclear{Co₂（COO）₂}substructure unit,while Zn MOF exhibits a nanocage-based（7.89×11.72×14.79?³）three-dimensional framework structure with a porosity of 42.9%.Fluorescence recognition tests showed that Co MOF as a fluorescence sensor can achieve highly sensitive and rapid recognition of Cr（VI）ions in the aqueous solution with low detection limits based on the fluorescence quenching response caused by the internal filtration effect.The amino-functionalized nanocage in the Zn MOF,on the other hand,endowed the material with excellent selectivity for the recognition of Cr（VI）ions and nitro antibiotics in the aqueous solution.Mechanistic studies suggested that in addition to the internal filtration effect,photoinduced electron transfer also played an important role in the fluorescence quenching response mentioned above.（II）During the aforementioned research process,single-signal fluorescence sensors demonstrated poor reliability and weak anti-interference ability in practical detection.Literature research suggested that the introduction of a luminescent guest can effectively solve this problem.This thesis successfully prepared{[Ni（TPTC）（bimb）·2H₂O]·2diox}_n（NiMOF）using H₄TPTC,1,4-bis[（1H-imidazol-1-yl）methyl]benzene（bimb）,and Ni（II）ions via a solvothermal method.Based on high porosity and uncoordinated carboxyl active sites of NiMOF,this thesis successfully functionalized it with rare earths and prepared two types of fluorescent sensing materials with dual emission centers,Tb³⁺@NiMOF and Eu³⁺@NiMOF.They can achieve rapid and sensitive sensing of epinephrine and hippuric acid in serum and urine,showing ultra-high reliability and anti-interference ability.The sensing mechanism studies showed that the fluorescence quenching response of the above rare earth functionalized sensing materials to target molecules is mainly attributed to the synergistic effects of internal filtration effect,energy competition absorption and host-guest interaction.While the fluorescence enhancement response is based on the enhanced structural rigidity caused by the host-guest interaction and photoinduced electron transfer effect.In addition,this thesis further improved the practicality and convenience of both rare earth functionalized sensing materials by constructing a combined logic gate intelligent detection system to match the concentration-controlled color change under UV lamp irradiation with a series of standard color card images preset in a smartphone.