Preparation And Properties Of MOFs With Pyridine Carboxylic Ligand

Metal-organic framework materials?MOFs?have developed rapidly in recent years because of their porosity,large specific surface area and unsaturated metal sites,which have potential for gas storage,environmental management,industrial catalysis,etc.application prospects.Since the pyridine carboxylic acid compound contains a carboxyl functional group and a nitrogen heterocyclic ring,it can be assembled into a different structure of MOFs with different metal ions,and attention has been paid in recent years.?1?In this paper,five metal organic framework materials were synthesized by using transition metal salt and pyridine carboxylic acid ligand at a molar ratio of 1:1 at 160⁰C underhydrothermalconditions.[Mn₂??-H₂O??4,3-pybz?₄]_n?1?,[Co₂??-H₂O??4,3-pybz?₄]_n?2?,[Cu₂??-H₂O??4,3-pybz?₄]_n?3?,[Zn?IN?₂·2H₂O]_n?4?,[Cd₂??-H₂O??4,3-pybz?₄]_n?5?.The complexes were characterized by FT-IR,XRD,TG,SEM,BET,fluorescence spectroscopy and UV-visible absorption spectroscopy.?2?Select three kinds of cationic dyes,Rhodamine B?Rh.B?,basic fuchsin?FB?and methylene blue?MB?,and use the anionic dye methyl orange?MO?as a reference to utilize the metal organic framework material?1?-?5?Test experiments on adsorption performance were carried out.The experimental results show that all the five complexes show good cationic dye adsorption properties,but almost no adsorption?but not zero?for anionic dyes.We have preliminary speculation on the adsorption mechanism,which may be due to the high specific surface area of the complex,the sample surface is easy to carry more negative charges,thus showing better adsorption to cationic dyes,indicating such complexes The adsorption of dye molecules may be related to electrostatic interactions,while the small adsorption of anionic dyes is due to the porous channel properties inherent in them.?3?Six kinds of metal ion solutions such as Pb²⁺,Fe³⁺,Cu²⁺,Mn²⁺,Cd²⁺and Zn²⁺were selected to simulate sewage,and the adsorption properties of heavy metal ions of metal organic framework materials?1?-?5?were tested.The experimental results show that the five complexes showed certain adsorption capacity for these metal ions.Co-MOF2 and Cd-MOF 5 showed excellent adsorption performance for Fe³⁺.Under the experimental conditions,the adsorption effects reached 86.95%and At 89.83%,we suspect that this may be due to the higher positive valence state of Fe³⁺compared to other metal ions,and the electrostatic interaction with MOFs carrying a large amount of negative charge.?4?The fluorescence effects of Co-MOF 2 and Cd-MOF 5 on Ce³⁺,Pb²⁺,Tb³⁺,Sr²⁺,Ca²⁺,Sm³⁺,Na⁺,Eu³⁺,Cd²⁺,K⁺,Co²⁺,Bi²⁺,Mg²⁺,Ni²⁺,Cu²⁺,Ag⁺,Zn²⁺and Fe³⁺were tested.And selected the petroleum ether,n-butyl alcohol,benzene,DMF,ethyl acetate and cyclohexane,methanol,chloroform,formaldehyde,acetic acid,dimethyl sulfoxide,isopropyl alcohol,n-hexane,N-methyl-2-pyrrolidone,acetone and other 15 kinds of organic solvent,and S^2-,HPO₄^2-,C₂O₄^2-,Cl^-,SO₄^2-,PO₄^3-,CH₃COO^-,I^-,Br^-,CO₃^2-,SCN^-,ClO^4-,H₂PO₄^-,NO₃^-,Cr₂O₇^2-15 kinds of anion,Then the selective fluorescence and sensitive fluorescence of Cd-MOF 5 to them were tested.The experimental results showed that Co-MOF 2 showed a certain fluorescence reduction effect on Fe³⁺,while Cd-MOF 5 showed an obvious selective fluorescence quenching response to acetone,Cr₂O₇^2-and Fe³⁺,respectively.It has a certain application potential in monitoring specific organic pollutants,heavy metal ions and toxic anions in sewage.