Bifunctional metal-organic frameworks based on pyridine tetracarboxylic acid ligands, methods of making and applications

Abstract

This invention discloses a bifunctional metal-organic framework material based on pyridine tetracarboxylic acid ligands, its preparation method, and its applications. It belongs to the field of crystalline materials, and its chemical formula is {[Zn2(L)(5-ATZ)]·1.5DMF·H2O}. n L 4‑ The deprotonated organic ligand (2,5-di-(3,5-dicarboxyphenyl))pyridine is prepared by a solvothermal reaction of the organic ligand (2,5-di-(3,5-dicarboxyphenyl))pyridine with aminotetrazole and zinc nitrate hexahydrate in a mixed solution of N,N-dimethylformamide and nitric acid to obtain colorless crystals. It can be used as a material for CO2 / CH4 and C2H2 / CO2 adsorption and separation or for Fe in aqueous solutions. 3+ Cr2O7 2‑ and CrO4 2‑ This high-sensitivity fluorescent detection material exhibits excellent stability and demonstrates superior performance in gas adsorption and separation, as well as heavy metal ion fluorescence detection.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of crystalline materials, and particularly relates to a bifunctional metal-organic framework material based on a pyridine tetracarboxylic acid ligand. The present application also relates to a preparation method of the bifunctional metal-organic framework material based on the pyridine tetracarboxylic acid ligand. The present application further relates to an application of the bifunctional metal-organic framework material based on the pyridine tetracarboxylic acid ligand. BACKGROUND

[0002] Acetylene (C2H2) is a very important chemical raw material, which can be used as welding fuel due to its large amount of heat released during combustion. The main source of C2H2 in industry is the thermal decomposition of natural gas, which inevitably produces carbon dioxide (CO2). Therefore, it is necessary to separate the mixture of C2H2 and CO2 to obtain high-purity C2H2. In addition, the presence of CO2 in CH4 not only sharply reduces the combustion heat value, but also causes serious corrosion to the delivery pipeline. Therefore, removing CO2 from natural gas has important industrial application value. Compared with inorganic porous materials, metal-organic frameworks (MOFs) are considered to be promising gas adsorption and separation materials due to their large specific surface area and adjustable pore size.

[0003] On the other hand, with the progress of society, water pollution has also become a topic of increasing concern. For example, the wastewater discharged in the production of metallurgy and paint industries usually contains heavy metal ions such as Cr2O7 2- , CrO4 2- and Fe 3+ , which can affect human health and the environment. At present, some methods for detecting heavy metal ions have been developed, including gas chromatography, atomic absorption spectrometry and spectrophotometry. However, these methods are expensive and not easy to carry, and cannot be used for real-time detection. Therefore, it is necessary to develop a detection method that is simple to operate and fast in response. In recent years, it has been found that metal-organic frameworks can be used as fluorescent sensors to solve the problems existing in traditional detection methods.

[0004] Therefore, pyridine tetracarboxylic acid (2,5-di-(3,5-dicarboxyphenyl))pyridine (H4L) is selected as an organic ligand, wherein the polycarboxylic acid can provide more coordination sites and form more coordination modes, which is conducive to the composition of novel structures, and the pyridine ring can make the formed structure more stable, thereby exhibiting excellent gas adsorption and separation and heavy metal ion detection performance. SUMMARY

[0005] The present application aims to provide a bifunctional metal-organic framework material based on a pyridine tetracarboxylic acid ligand, which has excellent stability and can exhibit excellent gas adsorption and separation and heavy metal ion fluorescence detection performance.

[0006] Another object of the present application is to provide a preparation method of the bifunctional metal-organic framework material based on the pyridine tetracarboxylic acid ligand.

[0007] Still another object of the present application is to provide an application of the bifunctional metal-organic framework material based on the pyridine tetracarboxylic acid ligand.

[0008] The first technical solution adopted by the present application is: a bifunctional metal-organic framework material based on a pyridine tetracarboxylic acid ligand, with a chemical molecular formula of {[Zn2(L)(5-ATZ)]·1.5DMF·H2O} n , L 4- is a deprotonated organic ligand (2,5-di-(3,5-dicarboxyphenyl))pyridine.

[0009] The bifunctional metal-organic framework material based on the pyridine tetracarboxylic acid ligand has the following characteristics:

[0010] {[Zn2(L)(5-ATZ)]·1.5DMF·H2O} n The crystal structure of the bifunctional metal-organic framework material based on the pyridine tetracarboxylic acid ligand belongs to an orthorhombic system, Imma with a space group, and cell parameters of: a = 19.038(14) Å, b = 26.520(19) Å, c = 17.040(12) Å, α = β = gamma = 90°.

[0011] {[Zn2(L)(5-ATZ)]·1.5DMF·H2O} n One asymmetric unit of the bifunctional metal-organic framework material based on the pyridine tetracarboxylic acid ligand includes one Zn 2+ ion, half of a ligand, and half of an aminotetrazole; Zn1 forms a five-coordinated square pyramid geometry with four oxygen atoms from three L 4- ligands and one nitrogen atom on the aminotetrazole; the carboxylic oxygen atoms in the L 4- ligand exist in two coordination modes, which are μ1-η 1 and μ1-η 2 ; two Zn1(Ⅱ) ions form a binuclear structural unit, and each L 4- ligand connects four adjacent binuclear structural units to form a three-dimensional framework structure with channels.

[0012] The organic ligand (2,5-di-(3,5-dicarboxyphenyl))pyridine is a rigid linear structure, containing four carboxylic functional groups and one pyridine nitrogen atom, and the four carboxylic groups are located at the meta positions of the outer benzene rings.

[0013] The chemical structural formula of the organic ligand (2,5-bis-(3,5-dicarboxyphenyl))pyridine is as follows:

[0014] .

[0015] The second technical solution adopted in this invention is: a method for preparing bifunctional metal-organic framework materials based on pyridine tetracarboxylic acid ligands, wherein under sealed conditions, the organic ligand (2,5-di-(3,5-dicarboxyphenyl))pyridine reacts with aminotetrazole and zinc nitrate hexahydrate in a mixed solution of N,N-dimethylformamide and nitric acid to obtain colorless crystals through a solvothermal reaction.

[0016] The second technical solution of the present invention is further characterized in that,

[0017] The molar ratio of the organic ligand (2,5-di-(3,5-dicarboxyphenyl))pyridine, aminotetrazole, and zinc nitrate hexahydrate is 3:5:8. Each 0.04 mmol of zinc nitrate hexahydrate corresponds to 2–4 mL of N,N-dimethylformamide and 1–4 mL of nitric acid, wherein the nitric acid concentration is 1 mL of HNO3 dissolved in 10 mL of distilled water.

[0018] The temperature of the solvothermal reaction is 90–130 °C, and the time is 24–60 hours.

[0019] The third technical solution adopted in this invention is: the application of bifunctional metal-organic framework materials based on pyridine tetracarboxylic acid ligands, using these materials as materials for CO2 / CH4 and C2H2 / CO2 adsorption and separation, or as materials for Fe in aqueous solutions. 3+ Cr2O7 2- and CrO4 2- High-sensitivity fluorescence detection materials.

[0020] The beneficial effects of this invention are: the bifunctional metal-organic framework material based on pyridine tetracarboxylic acid ligands, its preparation method, and its application exhibit excellent stability and demonstrate superior gas adsorption and separation, as well as fluorescence detection performance for heavy metal ions. The separation ratios for C2H2 / CO2 and CO2 / CH4 mixed gases are 5.32 and 17.2, respectively, and for Fe... 3+ Cr2O7 2- and CrO4 2- The detection limit reaches 10 -4 M surpasses that of most existing MOF materials. This invention opens up new design and synthesis prospects for novel linear pyridine tetracarboxylic acid ligand-based functional metal-organic frameworks, and has practical applications in gaseous and water pollution. Attached Figure Description

[0021] Figure 1 is a plot of the Zn(II) ion coordination environment of the metal-organic framework of the present invention;

[0022] Figure 2 is a plot of the coordination geometry of the metal cluster and Zn(II) ion in the metal-organic framework of the present invention;

[0023] Figure 3 is a plot of the coordination mode of L 4- in the metal-organic framework of the present invention;

[0024] Figure 4 is a three-dimensional plot of the metal-organic framework of the present invention;

[0025] Figure 5 is the N2adsorption isotherm of the metal-organic framework of the present invention at 77 K (inset shows the pore size distribution);

[0026] Figure 6 is the C2H2, CO2and CH4adsorption isotherms of the metal-organic framework of the present invention at 273 K and 298 K;

[0027] Figure 7 is the separation ratio curves of CO2 / CH4and C2H2 / CO2of the metal-organic framework of the present invention at 298 K;

[0028] Figure 8 is a bar plot of the luminescence intensity of the metal-organic framework of the present invention in different cation solutions;

[0029] Figure 9 is a plot of the luminescence intensity of the metal-organic framework of the present invention under different concentrations of Fe 3+ solution conditions;

[0030] Figure 10 is a Stern-Volmer fitting plot of the Fe 3+ solution titration;

[0031] Figure 11 is a bar plot of the luminescence intensity of the metal-organic framework of the present invention in different anion solutions;

[0032] Figure 12 is a plot of the luminescence intensity of the metal-organic framework of the present invention under different concentrations of Cr2O7 2- solution conditions;

[0033] Figure 13 is a plot of the luminescence intensity of the metal-organic framework of the present invention under different concentrations of CrO4 2- solution conditions;

[0034] Figure 14 is a Cr2O7 2-Stern-Volmer fitting plot of solution titration;

[0035] Figure 15 is CrO4 2- Stern-Volmer fitting plot of solution titration. DETAILED DESCRIPTION

[0036] The application will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] The application provides a linear pyridine tetracarboxylic acid ligand Zn(II) based metal-organic framework material, chemical molecular formula {[Zn2(L)(5-ATZ)]·1.5DMF·H2O} n , L 4- is a deprotonated organic ligand (2,5-di-(3,5-dicarboxyphenyl))pyridine (H4L).

[0038] {[Zn2(L)(5-ATZ)]·1.5DMF·H2O} n The crystal structure of the {[Zn2(L)(5-ATZ)]·1.5DMF·H2O} belongs to the orthorhombic system, Imma the space group, and the unit cell parameters are: a = 19.038(14) Å, b = 26.520(19) Å, c = 17.040(12) Å, α = β = gamma = 90°.

[0039] {[Zn2(L)(5-ATZ)]·1.5DMF·H2O} n One asymmetric unit of the {[Zn2(L)(5-ATZ)]·1.5DMF·H2O} includes one Zn 2+ ion, half of a ligand, and half of an amino tetrazole. The Zn1 forms a five-coordinated square pyramidal geometry with four oxygen atoms from three L 4- ligands and one nitrogen atom on the amino tetrazole. There are two coordination modes of the carboxylic oxygen atoms in the L 4- ligand, which are μ1-η 1 and μ1-η 2 , respectively. Two Zn1(II) ions form a dinuclear building unit, and each L 4- ligand connects four adjacent dinuclear building units to form a three-dimensional framework structure with channels.

[0040] The organic ligand is a rigid pyridine tetracarboxylic acid ligand (2,5-di-(3,5-dicarboxyphenyl))pyridine (H4L), and the chemical structure is as follows:

[0041]

[0042] The ligand has a rigid linear structure containing four carboxylic acid functional groups and one pyridine nitrogen atom, with the four carboxylic acids located in the meta position on the outer benzene ring.

[0043] This invention provides a method for preparing Zn(II)-based metal-organic framework materials based on pyridine tetracarboxylic acid ligands, specifically implemented as follows:

[0044] Under sealed conditions, the organic ligand (2,5-di-(3,5-dicarboxyphenyl))pyridine (H4L) reacts with the auxiliary ligands aminotetrazole CH3N5 (5-ATZ) and zinc nitrate Zn(NO3)2·6H2O in a mixed solution of N,N-dimethylformamide (DMF) and HNO3 via a solvothermal reaction to yield colorless crystals.

[0045] The molar ratio of the organic ligand (2,5-bis-(3,5-dicarboxyphenyl))pyridine, the auxiliary ligand aminotetrazole, and zinc nitrate Zn(NO3)2·6H2O is 3:5:8. Each 0.04 mmol of zinc nitrate corresponds to 2–6 mL of DMF and 1–4 mL of HNO3 (1 mL of HNO3 dissolved in 10 mL of distilled water). The solvothermal reaction is carried out at 90–130 °C for 24–60 hours.

[0046] This invention provides the application of linear pyridine tetracarboxylic acid ligand-based metal-organic frameworks in gas adsorption and separation and fluorescence detection of heavy metal ions.

[0047] This invention relates to bifunctional metal-organic framework materials based on pyridine tetracarboxylic acid ligands, their preparation methods, and applications. These materials exhibit excellent stability and demonstrate superior gas adsorption and separation, as well as fluorescence detection performance for heavy metal ions. The separation ratios for C2H2 / CO2 and CO2 / CH4 mixed gases are 5.32 and 17.2, respectively. For Fe... 3+ Cr2O7 2- and CrO4 2- The detection limit reaches 10 -4 M surpasses that of most existing MOF materials. This invention opens up new design and synthesis prospects for novel linear pyridine tetracarboxylic acid ligand-based functional metal-organic frameworks, and has practical applications in gaseous and water pollution.

[0048] Example 1

[0049] Ligand H4L (6 mg, 0.015 mmol), Zn(NO3)3-6H2O (12 mg, 0.04 mmol), 5-ATZ (1.7 mg, 0.025 mmol) were weighed into a 25 mL glass vial, DMF (2 mL) and HNO3 (1 mL) (1 mL HNO3 in 10 mL distilled water) were added and sonicated for 30 min to ensure complete dissolution. The vial was then placed in a 90 °C oven for 24 h. The vial was then allowed to cool to room temperature at 10 °C / h, colourless crystals were obtained which were washed with DMF and collected by filtration.

[0050] Example 2

[0051] Ligand H4L (6 mg, 0.015 mmol), Zn(NO3)3-6H2O (12 mg, 0.04 mmol), 5-ATZ (1.7 mg, 0.025 mmol) were weighed into a 25 mL glass vial, DMF (3.5 mL) and HNO3 (2.5 mL) (1 mL HNO3 in 10 mL distilled water) were added and sonicated for 30 min to ensure complete dissolution. The vial was then placed in a 110 °C oven for 36 h. The vial was then allowed to cool to room temperature at 10 °C / h, colourless crystals were obtained which were washed with DMF and collected by filtration.

[0052] Example 3

[0053] Ligand H4L (6 mg, 0.015 mmol), Zn(NO3)3-6H2O (12 mg, 0.04 mmol), 5-ATZ (1.7 mg, 0.02 mmol) were weighed into a 25 mL glass vial, DMF (6 mL) and HNO3 (4 mL) (1 mL HNO3 in 10 mL distilled water) were added and sonicated for 30 min to ensure complete dissolution. The vial was then placed in a 130 °C oven for 60 h. The vial was then allowed to cool to room temperature at 10 °C / h, colourless crystals were obtained which were washed with DMF and collected by filtration.

[0054] Example 4

[0055] Ligand H4L (6 mg, 0.015 mmol), Zn(NO3)3·6H2O (12 mg, 0.04 mmol), 5-ATZ (1.7 mg, 0.02 mmol) were weighed into a 25 mL vial, DMF (4 mL) and HNO3 (1.5 mL) (1 mL HNO3 was dissolved in 10 mL distilled water) were added, and the mixture was sonicated for 30 min to make it completely dissolved. Then it was put into a 100 °C oven, and the reaction time was 30 hours. Then it was cooled to room temperature at a rate of 10 °C / h, and colorless crystals were obtained. The crystals were washed with DMF solution and collected by filtration.

[0056] Example 5

[0057] Ligand H4L (6 mg, 0.015 mmol), Zn(NO3)3·6H2O (12 mg, 0.04 mmol), 5-ATZ (1.7 mg, 0.02 mmol) were weighed into a 25 mL vial, DMF (5 mL) and HNO3 (2 mL) (1 mL HNO3 was dissolved in 10 mL distilled water) were added, and the mixture was sonicated for 30 min to make it completely dissolved. Then it was put into a 120 °C oven, and the reaction time was 40 hours. Then it was cooled to room temperature at a rate of 10 °C / h, and colorless crystals were obtained. The crystals were washed with DMF solution and collected by filtration.

[0058] Example 6

[0059] Ligand H4L (6 mg, 0.015 mmol), Zn(NO3)3·6H2O (12 mg, 0.04 mmol), 5-ATZ (1.7 mg, 0.02 mmol) were weighed into a 25 mL vial, DMF (5.5 mL) and HNO3 (3 mL) (1 mL HNO3 was dissolved in 10 mL distilled water) were added, and the mixture was sonicated for 30 min to make it completely dissolved. Then it was put into a 115 °C oven, and the reaction time was 50 hours. Then it was cooled to room temperature at a rate of 10 °C / h, and colorless crystals were obtained. The crystals were washed with DMF solution and collected by filtration.

[0060] The test results of the products obtained in Examples 1-6 are the same, and are shown below:

[0061] (1) Determination of crystal structure:

[0062] Suitable crystals were selected and placed on a single crystal diffractometer, and the crystal diffraction data were collected by using Mo-Ka light source (λ = 1.149 Å). Then the data were refined by using SHELXTL-2014 software to obtain the structure of the crystal. The structure diagram is shown in Figures 1 to 4 . The crystallographic data are shown in Table 1. The property test diagram is shown in Figures 5 to 15 .

[0063] Table 1. Crystallographic data of metal-organic framework materials

[0064]

[0065] like Figure 1 As shown, an asymmetric unit cell of a metal-organic framework material includes a Zn atom. 2+ Ions, half a ligand and half an aminotetrazole.

[0066] like Figure 2 As shown, Zn1 and Zn1 from three L 4- The four oxygen atoms of the ligand and one nitrogen atom on the aminotetrazole form a five-coordinate tetragonal pyramidal geometry. Two Zn1(II) ions form a binuclear structural unit.

[0067] like Figure 3 As shown, in the metal-organic framework, a portion of L 4- The four carboxyl groups in the ligand lose four protons and connect with four Zn(II) ions in a bidentate chelate manner, while the other part L 4- The four carboxyl groups in the ligand lose four protons and are connected to eight Zn(II) ions in a monodentate bridging manner.

[0068] like Figure 4 As shown, each L in the metal-organic framework 4- The ligands form a three-dimensional framework structure with channels by connecting four nearby dual-core structural units.

[0069] like Figure 5 As shown, the adsorption performance of the metal-organic framework (MOF) at 77 K was tested. The figure shows the N2 adsorption isotherm of the MOF (the inset shows the pore size distribution). It can be seen that the adsorption isotherm type is reversible micropore (type I), and the maximum N2 adsorption capacity is 80.71 cm⁻¹. 3 / g. As can be seen from the pore size distribution curve in the inset, the pore size is mainly distributed at 7.33 Å.

[0070] like Figure 6 The figure shows the adsorption performance of metal-organic frameworks (MOFs) for C2H2, CO2, and CH4 at 273 K and 298 K. The figure includes the adsorption isotherms for C2H2, CO2, and CH4 of the MOFs at 273 K and 298 K. It can be seen that at 1 atm, 273 K, and 298 K, the adsorption capacity of the MOFs for C2H2 is 47.64 cm⁻¹. 3 / g and 35.89 cm 3 / g; the CO2 adsorption capacity was 43.35 cm⁻¹.3 / g and 28.37 cm 3 / g; the adsorption amounts of CH4 were 17.43 cm 3 / g and 8.11 cm 3 / g, respectively. It showed that there were differences in the adsorption of C2H2, CO2 and CH4 for the metal-organic framework.

[0071] As shown in Figure 7 , the separation ratios of CO2 / CH4 and C2H2 / CO2 of the metal-organic framework at 298 K, as shown in the figure is a curve graph of the separation ratios of CO2 / CH4 and C2H2 / CO2 of the metal-organic framework at 298 K. It can be seen that when the molar ratio of the mixed gas C2H2 / CO2, CO2 / CH4 is 50:50, the separation ratios are 5.32 and 17.2, respectively, which shows that the separation effect is good.

[0072] As shown in Figure 8 , the fluorescence performance test of the metal-organic framework in different cation solutions with a concentration of 0.01 mol / L, as shown in the figure is a column chart of the fluorescence intensity of the metal-organic framework in different metal ion solutions with a concentration of 0.01 mol / L. It can be seen that K + , Al 3+ , compared with the blank group, the fluorescence intensity has little change, Ca 2+ , Li + , Mg 2+ , Na + , Zn 2+ , Ni 2+ , the fluorescence intensity of the suspension thereof has different degrees of reduction, and Fe 3+ has a significant quenching phenomenon, which shows that the metal-organic framework material can selectively recognize and detect Fe 3+ .

[0073] As shown in Figure 9 , the titration experiment test of the metal-organic framework in Fe 3+ solution with a concentration of 0.01 mol / L, as shown in the figure is a graph of the emission peak light intensity of the metal-organic framework under different concentrations of Fe 3+ ion solution. It can be seen that with the increase of the concentration of Fe 3+ , the fluorescence intensity in the solution gradually decreases. When the concentration of Fe 3+ reaches 120 μL (0.38 mM), the fluorescence of the metal-organic framework is quenched, and the quenching rate reaches 96%, which has a good quenching effect.

[0074] As shown in Figure 10 , the relative fluorescence intensity of the metal-organic framework under low concentration of Fe 3+ solution and Fe3+ The concentration relationship diagram, as shown in the figure, represents the metal-organic framework in Fe. 3+ Relative fluorescence intensity of Fe under low concentration conditions 3+ The concentration-to-solution (Stern-Volmer) plot shows the relationship between the concentration and the relative fluorescence intensity of the metal-organic framework. It can be seen that at lower concentrations, the relative fluorescence intensity of the solution is related to the Fe... 3+ The concentration exhibits a good linear relationship, but some deviation occurs at higher concentrations, indicating that quenching is a process involving both static and dynamic processes. K can be obtained. sv The value is 2.94 × 10 4 M -1 For Fe 3+ The detection limit is 1.67 × 10⁻⁶. -4 M, with a low detection limit, indicates that this metal-organic framework material is effective against Fe. 3+ The detection has high sensitivity.

[0075] like Figure 11 As shown, the fluorescence performance of metal-organic frameworks in 0.01 mol / L solutions with different anion concentrations was tested. The figure shows a bar chart of fluorescence intensity of the metal-organic frameworks in 0.01 mol / L solutions with different anion concentrations. It can be seen that SO42-... 2- Cl - CO3 2- It has almost no effect on fluorescence intensity, Br - I - C2O4 2- The fluorescence of Cr2O7 is reduced. 2- CrO4 2- The obvious quenching phenomenon of its fluorescence indicates that this metal-organic framework material can selectively recognize and detect Cr2O7. 2- and CrO4 2- .

[0076] like Figure 12 As shown, metal-organic frameworks in Cr2O7 2- Titration experiments were conducted at a solution concentration of 0.01 mol / L. The figure shows the metal-organic framework at different concentrations of Cr2O7. 2- The luminescence intensity diagram of the emission peak under ionic solution conditions. It can be seen that with the increase of Cr2O7... 2- As the concentration of Cr2O7 increases dropwise, the fluorescence intensity gradually decreases. 2 When the concentration reached 120 μL (0.38 mM), fluorescence quenching occurred with a quenching rate of 96%, indicating a good quenching effect.

[0077] like Figure 13 As shown, metal-organic frameworks in CrO4 2-Titration experiments were conducted at a solution concentration of 0.01 mol / L. The figure shows the metal-organic framework at different concentrations of CrO4. 2- The luminescence intensity diagram of the emission peak under ionic solution conditions. It can be seen that with the increase of CrO4... 2- As the concentration of CrO4 is increased dropwise, the fluorescence intensity gradually decreases. 2- When the concentration reached 240 μL (0.74 mM), fluorescence quenching occurred with a quenching rate of 95.3%, indicating a good quenching effect.

[0078] like Figure 14 As shown, metal-organic frameworks in Cr2O7 2- Relative fluorescence intensity of Cr2O7 under low concentration conditions 2- Concentration relationship graph, as shown in the figure, represents the metal-organic framework in Cr2O7. 2- Relative fluorescence intensity of Cr2O7 under low concentration conditions 2- The concentration-to-solution (Stern-Volmer) plot shows the relationship between the concentration and the relative fluorescence intensity of the metal-organic framework. It can be seen that at lower concentrations, the relative fluorescence intensity of the solution is related to the Fe... 3+ The concentration of K exhibits a good linear relationship. sv The value is 2.17 × 10 4 M -1 For Cr2O7 2- The detection limit is 4×10 -4 M, with a low detection limit, indicates that this metal-organic framework material has a low detection limit for Cr2O7. 2- The detection has high sensitivity.

[0079] like Figure 15 As shown, metal-organic frameworks in CrO4 2- Relative fluorescence intensity of CrO4 solution under low concentration conditions 2- Concentration relationship graph, as shown in the figure, represents the metal-organic framework in CrO4 2- Relative fluorescence intensity of CrO4 solution under low concentration conditions 2- The concentration-to-solution (Stern-Volmer) plot shows the relationship between the concentration and the relative fluorescence intensity of the metal-organic framework. It can be seen that at lower concentrations, the relative fluorescence intensity of the solution is related to the Fe... 3+ The concentration of K showed a good linear correlation. sv The value is 7.36 × 10 3 M -1 For CrO4 2- The detection limit is 6.3 × 10⁻⁶. -4 The low detection limit of M indicates that this metal-organic framework material has a low detection limit for CrO4. 2- The detection has high sensitivity.

Claims

1. A bifunctional metal-organic framework material based on a pyridine tetracarboxylic acid ligand, characterized in that, The chemical formula is {[Zn2(L)(5-ATZ)]·1.5DMF·H2O} n , L 4- is a deprotonated organic ligand (2,5-di-(3,5-dicarboxyphenyl)pyridine).

2. The bifunctional metal-organic framework based on pyridine tetracarboxylic acid ligand of claim 1, wherein, {[Zn2(L)(5-ATZ)]·1.5DMF·H2O} n The crystal structure of the compound belongs to the orthorhombic system, Imma space group, with the cell parameters of: a = 19.038(14) Å, b = 26.520(19) Å, c = 17.040(12) Å, α = β = γ = 90°.

3. The bifunctional metal-organic framework based on pyridine tetracarboxylic acid ligand of claim 1, wherein, {[Zn2(L)(5-ATZ)]·1.5DMF·H2O} n One asymmetric unit includes one Zn 2+ ion, half of a ligand and half of an amino tetrazole; Zn1is five-coordinated in a square pyramidal geometry with four oxygen atoms from three L 4- ligands and one nitrogen atom from the amino tetrazole; L 4- ligands exist in two coordination modes, μ1-η 1 and μ1-η 2 ; two Zn1(Ⅱ) ions form a dinuclear building unit, each L 4- ligand links four neighboring dinuclear building units to form a three-dimensional framework structure with channels.

4. The bifunctional metal-organic framework based on pyridine tetracarboxylic acid ligand of claim 1, wherein, The organic ligand (2,5-di-(3,5-dicarboxyphenyl))pyridine is a rigid linear structure, containing four carboxylic acid functional groups and one pyridine nitrogen atom, and the four carboxylic acids are located at the meta position of the outer benzene ring.

5. The bifunctional metal-organic framework based on pyridine tetracarboxylic acid ligand of claim 4, wherein, The chemical structural formula of the organic ligand (2,5-di-(3,5-dicarboxyphenyl))pyridine is: 。 6. The method of preparing bifunctional metal-organic frameworks based on pyridine tetracarboxylic acid ligands according to claim 1, wherein, Under sealed conditions, the organic ligand (2,5-di-(3,5-dicarboxyphenyl))pyridine, aminotetrazole and zinc nitrate hexahydrate are reacted by a solvothermal method in a mixed solution of N,N-dimethylformamide and nitric acid to obtain colorless crystals.

7. The method of producing a bifunctional metal-organic framework material based on a pyridine tetracarboxylic acid ligand according to claim 6, wherein The molar ratio of the organic ligand (2,5-di-(3,5-dicarboxyphenyl))pyridine, aminotetrazole and zinc nitrate hexahydrate is 3:5:8, and 2-4 mL of N,N-dimethylformamide and 1-4 mL of nitric acid are used for every 0.04 mmol of zinc nitrate hexahydrate, wherein the concentration of nitric acid is 1 mL of HNO3 dissolved in 10 mL of distilled water.

8. The method of preparing bifunctional metal-organic frameworks based on pyridine tetracarboxylic acid ligands according to claim 6, wherein, The temperature of the solvothermal reaction is 90-130 ℃, and the time is 24-60 hours.

9. Use of a bifunctional metal-organic framework material based on a pyridine tetracarboxylic acid ligand, characterized in that, The bifunctional metal-organic framework material based on the pyridine tetracarboxylic acid ligand in any one of claims 1-8 is used as a material for CO2 / CH4 and C2H2 / CO2 adsorption separation.

10. Use of a bifunctional metal-organic framework material based on a pyridine tetracarboxylic acid ligand, characterized in that, The bifunctional metal-organic framework material based on pyridine tetracarboxylic acid ligand in any one of claims 1-8 is used as a high-sensitivity fluorescent detection material for Fe 3+ , Cr2O7 2- , and CrO4 2- in aqueous solution.

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