Metal-organic Frameworks And Their Properties Based On 1-(4-Carboxyphenyl)-1H-Pyrazole-3-Carboxylic Acid Ligand

Metal-Organic Frameworks（MOFs）,also known as Coordination Polymers（CPs）,have become leading edge materials due to their unique porous organic-inorganic periodic structures and functional diversity.The topology of MOFs can be adjusted and a variety of structures can be obtained by carefully selecting metal nodes and organic linkers.Besides,MOFs with required chemical and physical properties can be produced,such as suitable porosity,specific surface area,and luminescence ability.MOFs have become current research hotspot due to their unique structures and numerous potential applications,such as adsorption properties,catalytic conversion,and fluorescence detection.In this work,we chose 1-（4-carboxyphenyl）-1H-pyrazole-3-carboxylic acid（H₂L）ligand containing pyrazole dicarboxylic acid group to construct multifunctional MOFs.The two carboxylic acid groups in the H₂L provide the flexible coordination modes,and the nitrogen atom in the pyrazole group can form the chelating coordination mode with the adjacent carboxyl group,also serve as an active site to optimize the properties of targeted MOFs.Eight MOFs were synthesized by solvothermal method using the H₂L and different metal salts,and the single crystal structures were obtained on the single crystal X-ray diffractometer.In addition,the complexes were basically characterized and further functionally explored.The following is the specific content:1.The research progress,design synthesis and related application fields of MOFs were expounded,and the significance of the topic and the current research progress were also introduced.2.Three isomorphic complexes[Ln₂（L）₃（H₂O）₅]_n（Ln=Eu（1-Eu）,Tb（2-Tb）,Dy（3-Dy））were synthesized using the H₂L ligand and lanthanide ions.The complexes 1-Eu and 2-Tb emitting strong red and green fluorescence,respectively.1-Eu_xTb_1-x with continuous color changes from red,orange-red,yellow to yellow-green and green were obtained by fine-tuning the ratio of Eu³⁺and Tb³⁺ions.And 1-Eu as the luminescent probe can selectively recognize and detect nitrobenzene molecules,and the detection limit is 2.51×10^-4 M.In addition,1-Eu can be used as the unique barcode for anti-counterfeiting of commodity goods,according to the particularity of the Ln-MOFs spectrum.3.Two Cd-MOFs with different structures were synthesized by using the H₂L and the Cd²⁺ion,which are{[Cd（L）（H₂O）₂]·H₂O}_n（4-Cd）with two-dimensional layered structure and{[Cd（L）（H₂O）]·4H₂O}_n（5-Cd）with three-dimensional structure,respectively.And based on the fluorescence properties of the complex 4-Cd,the near white light emitting material Eu³⁺/Tb³⁺@4-Cd with the CIE coordinate（0.33,0.34）was obtained by doping lanthanide ions post-synthesis.In addition,5-Cd exhibits great selective adsorption performance for malachite green dye based on the large porosity（48.2%）,and the adsorption value reached16.3 mg/g.Catalytic experiments show that 5-Cd has good catalytic ability for CO₂cycloaddition reaction,among which,the catalytic efficiency for epichlorohydrin is as high as 97.6%.4.Three MOFs were synthesized using H₂L ligands with Ni²⁺,Co²⁺and Zn²⁺ions,which are[Ni（L）（4,4’-bipy）H₂O]_n（6-Ni）,{[Ni_1-xCo_x（L）（4,4’-bipy）H₂O]_n（x=1/4,7-Ni/Co）and{[Zn（L）（4,4’-bipy）_0.5]3H₂O}_n（8-Zn）,where 6-Ni and 7-Ni/Co are isostructural complexes.Compared with the structure of 6-Ni,about 1/4 of the Ni²⁺ions in 7-Ni/Co are occupied by Co²⁺.In addition,8-Zn can be used as a fluorescent probe material for efficiently detecting antibiotics NZF,MDZ and pesticide DCN in water,with detection limits of 9.32×10^-6 M,1.05×10^-5 M and 2.78×10^-5 M,respectively.