Fluorescence Sensing And Photocatalytic Properties Of Metal-Organic Framework Materials Based On Polycarboxylic Acid Ligands

Metal-organic frameworks（MOFs）,also known as porous coordination polymers（PCPs）,are an emerging and rapidly developing class of porous materials consisting of metal-containing nodes（also known as secondary building blocks,or SBUs）and organic ligands that are interconnected by self-assembly to form a class of porous crystalline materials with unique structures and functions.PCPs are an emerging and rapidly developing class of porous crystalline materials with unique structures and functions formed by interconnecting metal-containing nodes（also known as secondary building units,or SBUs）and organic ligands through self-assembly.MOFs have become one of the fastest growing fields in the field of new porous materials due to their geometry,pore size,and tunability of function.In addition,MOFs have excellent properties in luminescence,sensing,and photocatalysis,which have received a lot of attention from researchers.This thesis is divided into three parts:the first part of the content of the organic ligand 1,3,5-tris（carboxymethoxy）benzene（H₃tcmb）and terbium ions were selected to construct an Tb（Ⅲ）based MOFs{[Tb（tcmb）（H₂O）₂]·3H₂O}_n（1）by solvothermal method,which was used as an effective fluorescent probe due to its good luminescent properties for the identification of metal anions and cations in water.In the second part,the organic ligands2,5-di（2’,4’-dicarboxyphenyl）pyridine（H₄ddpp）and europium and gadolinium ions were chosen to construct two isostructural rare earth-based MOFs{[Eu（ddpp）（H₂O）]·CH₃CN}_n（1-Eu）,{[Gd（ddpp）（H₂O）]·CH₃CN}_n（1-Gd）,which by Fluorescence spectroscopy analysis,the fluorescence spectrum of the complex 1-Eu contains characteristic emission peaks of both ligand and europium ions.The ligand was also used to effectively identify antibiotic contaminants in water because of the supramolecular recognition site provided by the naked pyridine nitrogen group in the ligand.In the third part,the organic ligand2,5-di（2’,4’-dicarboxyphenyl）-1,4-difluorobenzene（H₄ddpd）and the auxiliary ligand4,4’-bipyridine（4,4’-bipy）were chosen to construct an zinc-based MOF containing halogen bond functionalization with zinc ions{[Zn（ddpd）_0.5（bipy）_0.5]·H₂O]}_n（1-Zn）,the stability of the complexes was enhanced by the introduction of C-F bonds,which gave the ligands high stability and antioxidant properties.In addition,the conduction band potential（CB）of the complex 1-Zn was finally calculated by XPS and UV-Vis DRS analysis.The valence band（VB）of complex 1-Zn is larger than the potential potential required for the production of hydroxyl radicals,while the conduction band（CB）potential is smaller than the potential required for the production of superoxide radicals,indicating that complex1-Zn can produce both superoxide radicals and hydroxyl radicals during the excitation of visible light to accelerate the photocatalytic degradation process.Finally,the experimental results showed that complex 1-Zn degraded rhodamine B,methyl blue and methyl orange with an efficiency of more than 95%within 40 min under visible light.