A multi-imidazole ligand-based metal organic framework material, a preparation method and application thereof

Abstract

The present application relates to the technical field of catalytic degradation of organic pollutants and metal organic framework, and particularly relates to a metal organic framework material based on multi-imidazole ligand and a preparation method and application thereof.The metal organic framework material based on multi-imidazole ligand provided by the present application has good peroxidase-like catalytic performance, and the degradation rate of methylene blue reaches 93.7% within 120 min, and can quickly and efficiently remove organic dye pollutants in water.In addition, the metal organic framework material based on multi-imidazole ligand provided by the present application has high structural stability and thermal stability, and can still maintain good catalytic activity after multiple cycles;and can still maintain stable catalytic activity in a wide pH range and complex water environment, and has strong environmental interference resistance, and therefore has good application prospect.

Description

Technical Field

[0001] This invention relates to the fields of catalytic degradation of organic pollutants and metal-organic frameworks, specifically to a metal-organic framework material based on domizole ligands, its preparation method, and its application. Background Technology

[0002] Methylene blue, a thiazide dye, is frequently used industrially for dyeing cotton, silk, and paper. It is also used for coloring bamboo and wood, and in the manufacture of inks and lakes. While relatively stable in air, it is readily soluble in water, ethanol, and chloroform. It is a representative pollutant in dye wastewater. If discharged directly without treatment, the dye will circulate and accumulate in the wastewater. Concentrations of methylene blue exceeding a certain level can damage the gastrointestinal tract, kidneys, cardiovascular system, and central nervous system in humans. High concentrations can cause poisoning and death in animals. Therefore, there is an urgent need to develop effective methods for removing methylene blue from wastewater.

[0003] Enzymatic degradation, as a green and efficient treatment technology, has gradually attracted attention. Peroxidases (such as horseradish peroxidase) can effectively catalyze the degradation of various organic dyes. However, natural enzymes typically suffer from poor stability, easy inactivation, high preparation costs, and difficulty in reusability, limiting their widespread application in practical engineering. In contrast, peroxidase-like nanomaterials (nanozymes) have become a research hotspot due to their advantages such as structural stability, low cost, ease of preparation, and reusability. Metal-organic frameworks (MOFs) are ideal materials for designing bio-enzyme mimicry systems due to their high specific surface area, porosity, uniform porosity, good chemical stability, and thermal stability. However, MOFs, as peroxidase-like materials, exhibit poor stability and low catalytic activity in the degradation of methylene blue, limiting their application in the degradation of organic dyes. Summary of the Invention

[0004] To overcome the above problems, this invention provides a metal-organic framework material based on domizole ligands, its preparation method, and its application.

[0005] To achieve the above technical objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a metal-organic framework material based on doimidazole ligands, with the structure shown in formula (I) as the structural repeating unit;

[0006] Equation (Ⅰ).

[0007] The chemical formula of the metal-organic framework material based on doimidazole ligand is [Ni(dip)4(H2O)2]n·2(NO3), where dip is a doimidazole ligand, and its structural formula is shown in formula (II).

[0008]

[0009] Formula (II).

[0010] Each asymmetric unit contains several Ni metal centers. Each Ni(II) center forms an octahedral geometry with four nitrogen atoms from four domizole ligands and two oxygen atoms from two coordinated water molecules, thereby forming an infinitely extended "-Ni(II)-dip-Ni(II)-dip-" chain structure. The chain structure is arranged in parallel to form a two-dimensional layer, and a three-dimensional metal-organic framework crystal structure is constructed through intermolecular hydrogen bonds and π-π stacking interactions between coordinated water molecules and free nitrate anions.

[0011] Metal-organic frameworks based on doimidazole ligands belong to the triclinic crystal system, with space group P-1— and cell parameters a = 8.0592(19) Å, b = 9.076(3) Å, c = 10.091(2) Å, α = 71.941(10) °, β = 70.600(2) °, and γ = 69.579(10) °.

[0012] A second aspect of the present invention provides a method for preparing the metal-organic framework material based on doimidazole ligands as described in the first aspect, comprising the following steps: Domidine ligands and nickel salts were dispersed in an alkaline mixed solvent and subjected to a solvothermal reaction to obtain metal-organic framework materials based on domidine ligands.

[0013] A third aspect of the present invention provides the application of the metal-organic framework material based on doimidazole ligands described in the first aspect or the metal-organic framework material based on doimidazole ligands prepared by the preparation method described in the second aspect as a catalyst.

[0014] The beneficial effects of this invention are as follows: The metal-organic framework material based on doimidazole ligands provided by this invention exhibits excellent peroxidase-like catalytic performance, achieving a 93.7% degradation rate of methylene blue within 120 min, thus enabling rapid and efficient removal of organic dye pollutants from water. Furthermore, the metal-organic framework material based on doimidazole ligands provided by this invention possesses high structural and thermal stability, maintaining good catalytic activity even after multiple cycles of use; it also maintains stable catalytic activity over a wide pH range and in complex aquatic environments, demonstrating strong resistance to environmental interference, thus showing promising application prospects. Attached Figure Description

[0015] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0016] Figure 1 This is a schematic diagram of a metal-organic framework material based on doimidazole ligands; Figure 2 This is a schematic diagram of an infinitely extended chain structure formed by the interconnection of asymmetric units in the crystal structure of a metal-organic framework material based on domizole ligands. Figure 3 A schematic diagram of a two-dimensional layer formed by parallel chain-like structures; Figure 4 This is a schematic diagram of the three-dimensional packing state in a metal-organic framework crystal structure based on domizole ligands; Figure 5 Powder X-ray diffraction (PXRD) pattern of metal-organic framework materials based on domizole ligands; Figure 6 Morphology analysis of metal-organic framework materials based on domizole ligands, where a is a SEM image and b is an elemental mapping map of energy dispersive X-ray spectroscopy (EDX). Figure 7 Thermogravimetric analysis (TGA) of metal-organic framework materials based on doimidazole ligands; Figure 8 The activity curves of peroxidase-like enzymes based on domizole ligand metal-organic frames are shown. Figure 9 The image shows the UV-absorbing spectra of the metal-organic framework catalytic degradation of methylene blue and methyl violet based on domizole ligands; the insets are images of the actual samples. Figure 10 The graph shows the degradation rate of methylene blue catalyzed by metal-organic frames based on domizole ligands. Figure 11 This is a graph showing the degradation rate during multiple cycles; Figure 12 Powder X-ray diffraction (PXRD) patterns of metal-organic framework materials based on domizole ligands after multiple cycles of degradation; Figure 13 The degradation rate of MB by domizazole-based metal-organic framework materials under different pH conditions; Figure 14 The effect of domizole ligand-based metal-organic frameworks on the degradation of MB in real aquatic matrices is given by a, where a is the degradation rate and b is the degradation rate constant. Detailed Implementation

[0017] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0018] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0019] Currently, the main methods for treating dye wastewater include flocculation, membrane filtration, ion exchange, and electrolytic precipitation. However, these methods all have their limitations, such as the disposal of large amounts of sludge generated by flocculation and electrolytic precipitation, and the high cost of membrane filtration and ion exchange. Therefore, the treatment cost of these methods for dye wastewater is relatively high. Enzymatic degradation, as a green and efficient treatment technology, is gradually gaining attention. Peroxidases (such as horseradish peroxidase) can effectively catalyze the degradation reaction of various organic dyes. However, natural enzymes usually have drawbacks such as poor stability, easy inactivation, high preparation cost, and difficulty in reusing, which limits their widespread application in practical engineering.

[0020] Enzymatic degradation, as a green and efficient treatment technology, has gradually attracted attention. Among them, peroxidases (such as horseradish peroxidase) can effectively catalyze the degradation reaction of various organic dyes. However, natural enzymes usually have drawbacks such as poor stability, easy inactivation, high preparation cost, and difficulty in reusing, which limit their widespread application in practical engineering.

[0021] In contrast, peroxidase-like nanomaterials (nanozymes) have become a research hotspot for replacing natural enzymes due to their advantages such as structural stability, low cost, ease of preparation, and reusability. Metal-organic frameworks (MOFs) are ideal materials for designing bio-enzyme mimicry systems due to their high specific surface area, porosity and uniform porosity, good chemical stability, and thermal stability. However, MOFs as peroxidase-like materials suffer from poor stability and low catalytic activity in the degradation of methylene blue, limiting their application in the degradation of organic dyes.

[0022] To overcome the above problems, this invention provides a metal-organic framework material based on domizole ligands, its preparation method, and its application.

[0023] The metal-organic framework material based on doimidazole ligands provided by this invention exhibits excellent peroxidase-like catalytic performance. It catalyzes the decomposition of H₂O₂ through a "Fenton-like reaction," generating highly active hydroxyl radicals (·OH). These ·OH radicals, acting as strong oxidants, attack the chromophores (such as sulfur-containing aromatic heterocycles) in the methylene blue molecule, disrupting its chemical structure, causing it to lose its color and be completely decomposed. The doimidazole ligand-based metal-organic framework material provided by this invention achieves a 93.7% degradation rate of methylene blue within 120 min, enabling rapid and efficient removal of organic dye pollutants from water. Furthermore, the doimidazole ligand-based metal-organic framework material provided by this invention exhibits high structural and thermal stability, maintaining good catalytic activity even after multiple cycles of use. It also maintains stable catalytic activity over a wide pH range and in complex aquatic environments, demonstrating strong resistance to environmental interference, thus showing promising application prospects.

[0024] A first typical embodiment of the present invention provides a metal-organic framework material based on domizole ligands, with the structure shown in formula (I) as the structural repeating unit;

[0025] Equation (Ⅰ).

[0026] A second typical embodiment of the present invention provides a method for preparing the metal-organic framework material based on doimidazole ligands as described in the first aspect, comprising the following steps: Domidine ligands and nickel salts were dispersed in an alkaline mixed solvent and subjected to a solvothermal reaction to obtain metal-organic framework materials based on domidine ligands.

[0027] In one or more embodiments, the nickel salt includes nickel nitrate.

[0028] In one or more embodiments, the molar ratio of domizole ligand to nickel salt is (0.9~1.1):1, preferably 1:1.

[0029] In one or more embodiments, the alkaline mixed solvent is composed of N,N-dimethylformamide (DMF), methanol, and water, and the alkalinity of the mixed solvent is adjusted using sodium hydroxide. Under alkaline conditions, the hydroxide ions (OH-) in NaOH... - It can neutralize the carboxyl group (-COOH) on the ligand, "deprotonating" it to convert it into a carboxylate anion (-COO). - This transformation can significantly improve the solubility of ligands in solution and enhance their reactivity in coordination with metal ions, which is a prerequisite for the successful construction of the MOF framework.

[0030] Preferably, the volume ratio of N,N-dimethylformamide (DMF), methanol and water is (0.8~1.2):(1~2):(4~6), and more preferably 1:1.5:5.

[0031] Preferably, the pH of the alkaline mixed solvent is 9-11, and more preferably 10.

[0032] In one or more embodiments, the concentration of the nickel salt in the alkaline mixed solvent is 0.015~0.02 mol / L, preferably 0.0176 mol / L.

[0033] In one or more embodiments, the temperature of the solvothermal reaction is 100~120°C, and the time of the solvothermal reaction is 70~80 h.

[0034] A third aspect of the present invention provides the application of the metal-organic framework material based on doimidazole ligands described in the first aspect or the metal-organic framework material based on doimidazole ligands prepared by the preparation method described in the second aspect as a catalyst.

[0035] In one or more embodiments, the application includes the degradation of organic pollutants; Preferably, the organic pollutant includes methylene blue.

[0036] More preferably, the pH of the solution is 3-10 when degrading methylene blue.

[0037] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0038] Example 1 Domidine ligands and nickel salts were dispersed in an alkaline mixed solvent and subjected to a solvothermal reaction to obtain metal-organic framework materials based on domidine ligands.

[0039] Domizazole ligand (30 mg, 0.15 mmol) and Ni(NO3)2·6H2O (43.6 mg, 0.15 mmol) were dissolved in DMF (1 mL), methanol (1.5 mL), and ultrapure water (5 mL). Sodium hydroxide solution (0.1 mol / L, 1 mL) was added to adjust the mixed solution to alkaline (pH=10). The mixture was ultrasonically mixed (40 kHz, 15 min) until homogeneous, and then transferred to a stainless steel autoclave lined with a polytetrafluoroethylene reactor. After sealing, the autoclave was placed in a constant temperature oven and reacted at 110 °C for 72 h. The reaction was then slowly cooled to room temperature at a rate of 5 °C / h. The solid was collected, filtered, thoroughly washed with DMF, and vacuum dried to obtain green rhomboid block crystals, which are the metal-organic framework materials based on domizazole ligand.

[0040] Figure 1 This is a schematic diagram of a metal-organic framework material based on doimidazole ligands. Figure 1 As can be seen, each asymmetric unit contains several Ni metal centers, and each Ni(II) center forms an octahedral geometry with four nitrogen atoms from four domizole ligands and two oxygen atoms from two coordinated water molecules.

[0041] Table 1 shows the crystallographic parameters of the metal-organic framework material based on doimidazole ligands. As can be seen from Table 1, the metal-organic framework material based on doimidazole ligands belongs to the triclinic crystal system, with space group P-1— and cell parameters a = 8.0592(19) Å, b = 9.076(3) Å, c = 10.091(2) Å, α = 71.941(10) °, β = 70.60(10) °, and γ = 69.579(10) °.

[0042] Table 1 Crystallographic parameters of metal-organic frameworks based on doimidazole ligands

[0043] Figure 2 This is a schematic diagram illustrating the infinitely extending chain-like structure formed by the interconnection of asymmetric units in the crystal structure of a metal-organic framework material based on domizole ligands. Figure 2 As can be seen, based on each asymmetric unit, an infinitely expanding "-Ni(II)-dip-Ni(II)-dip-" chain structure is formed; the parallel arrangement of the chain structures forms a two-dimensional layer ( Figure 3 And, through intermolecular hydrogen bonds formed between coordinated water molecules and free nitrate anions, as well as π-π stacking interactions, a three-dimensional metal-organic framework crystal structure is constructed. Figure 4 ).

[0044] Figure 5 The powder X-ray diffraction (PXRD) patterns of metal-organic framework materials based on domizole ligands are shown below. Figure 5 As can be seen from the data, the characteristic peaks of the metal-organic framework material based on doimidazole ligands are in good agreement with the simulated spectrum, indicating the successful preparation of the metal-organic framework material based on doimidazole ligands.

[0045] Figure 6 For morphology analysis of metal-organic framework materials based on doimidazole ligands, such as Figure 6 As shown in Figure a, the SEM image of the metal-organic framework material based on doimidazole ligands reveals that the material has a layered microstructure with stacked surface structures, confirming the existence of sufficient proton transport pathways in the catalytic system, thereby providing more catalytic active sites and improving its catalytic performance. Figure 6As shown in Figure b, energy-dispersive X-ray spectroscopy (EDX) elemental mapping confirmed the uniform spatial distribution of C, N, O, and Ni throughout the structural framework. Table 1 shows that EDX measurements of the domimidazole ligand-based metal-organic framework material indicate the presence of C, N, O, and Ni elements. The elemental composition observed in the domimidazole ligand-based metal-organic framework material is as follows: C > N > O > Ni. The results show that C and O have a high proportion, while Ni has the lowest proportion. The elemental composition in the EDX measurements indicates that the domimidazole ligand-based metal-organic framework material has been successfully synthesized.

[0046] Figure 7 Thermogravimetric analysis (TGA) of metal-organic framework materials based on doimidazole ligands, from Figure 7 It can be seen that the metal-organic framework material based on domizole ligands maintains structural stability and high thermal stability up to 320℃.

[0047] Example 2 Peroxidase-like activity of metal-organic framework materials based on doimidazole ligands: A peroxidase-mimicking experiment was conducted using a metal-organic framework (MOF) with domizole ligands, employing the traditional peroxidase substrate TMB. Three experimental groups were designed, with two control groups without catalyst material. The absorbance differences among the three groups at 652 nm were measured. Figure 8 As shown in the figure. The results indicate that, according to the analysis, when metal-organic framework materials based on doimidazole ligands and H2O2 are present simultaneously, they can catalyze the oxidation of TMB to produce a blue reaction.

[0048] Example 3 Metal-organic frameworks based on doimidazole ligands catalyze the degradation of methylene blue: 6 mg of the organic dye methylene blue was dispersed in 100 mL of water and mixed thoroughly to obtain a concentration of 6 mg·L⁻¹. -1 An aqueous solution of the organic dye methylene blue was prepared, and then H2O2 (50 mmol / L) and TMB (1.2 mmol / L) were added, and the pH was adjusted to 6.0 to obtain an aqueous solution of the organic dye methylene blue to be degraded.

[0049] Take 20 mg of the solid powder sample of the metal-organic framework material based on domizole ligand prepared in Example 1, add it to 100 mL of the methylene blue aqueous solution of the organic dye to be degraded, adjust the system temperature to 40 °C, take samples (5 mL) every 15 min, centrifuge, take the supernatant and measure it in the wavelength range of 200~800 nm using a UV-2550 ultraviolet spectrometer, and the catalytic time is 120~135 min.

[0050] like Figure 9As shown, the trend of the UV spectrum of the reaction solution over time is used to describe the catalytic activity of the metal-organic framework material based on domizole ligands. The intensity of the UV absorption peak of methylene blue decreases significantly with increasing reaction time.

[0051] A degradation rate curve can be obtained by plotting the reaction time and relative concentration, which can more intuitively reflect the degradation effect. Figure 10 As shown, the metal-organic framework material based on doimidazole ligands achieved a degradation rate of 93.7% for methylene blue within 120 min. This demonstrates that the metal-organic framework based on doimidazole ligands of the present invention exhibits extremely high catalytic degradation ability for the organic dye methylene blue.

[0052] The metal-organic framework material based on doimidazole ligands after the first degradation was recovered and subjected to cyclic degradation experiments. The degradation rate curves during multiple cycles are shown in the figure below. Figure 11 As shown, the powder X-ray diffraction (PXRD) patterns of the metal-organic framework material based on doimidazole ligands after multiple cycles of degradation are as follows. Figure 12 As shown, from Figure 11 and Figure 12 As can be seen, the metal-organic framework material based on domizole ligands can still maintain more than 90% of the methylene blue degradation after multiple cycles, and the structure remains intact, thus proving that it has good structural stability.

[0053] Example 4 To further evaluate the adaptability of the degradation system, the effect of pH value of the reaction system on MB removal efficiency was analyzed. Figure 13 As shown, the system can maintain a relatively high degradation rate of MB within the pH range of 3 to 10.

[0054] Example 5 To evaluate the degradation efficiency of the degradation system for MB in real aquatic substrates, degradation experiments were conducted using environmental water samples collected from Jiaozhou Bay and the Dagu River, with MB incorporated into these substrates prior to the experiments. Figure 14 The MB degradation rate constant K observed in seawater and river water samples is shown. obs They were 0.0216 min respectively. -1 and 0.0205 min -1 This indicates that metal-organic framework materials based on doimidazole ligands still have good degradation effects on MB in real aquatic matrices.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A metal-organic framework material based on doimidazole ligands, characterized in that, The structure shown in equation (Ⅰ) is used as the structural repeating unit; Equation (Ⅰ).

2. The method for preparing the metal-organic framework material based on doimidazole ligands according to claim 1, characterized in that, Includes the following steps: Domizazole ligands and nickel salts were dispersed in an alkaline mixed solvent and subjected to a solvothermal reaction to obtain metal-organic framework materials based on domizazole ligands; The structural formula of the domizole ligand is shown in formula (II); Formula (II).

3. The preparation method according to claim 2, characterized in that, The nickel salt includes nickel nitrate.

4. The preparation method according to claim 2, characterized in that, The molar ratio of domizole ligand to nickel salt is (0.9~1.1):

1.

5. The preparation method according to claim 4, characterized in that, The molar ratio of domizole ligand to nickel salt is 1:

1.

6. The preparation method according to claim 2, characterized in that, The alkaline mixed solvent is composed of N,N-dimethylformamide (DMF), methanol, and water, and sodium hydroxide is used to adjust the alkalinity of the mixed solvent.

7. The preparation method according to claim 6, characterized in that, The volume ratio of N,N-dimethylformamide (DMF), methanol, and water is (0.8~1.2):(1~2):(4~6). Alternatively, the pH of the alkaline mixed solvent is 9-11.

8. The preparation method according to claim 7, characterized in that, The volume ratio of N,N-dimethylformamide (DMF), methanol, and water is 1:1.5:

5.

9. The preparation method according to claim 7, characterized in that, The pH of the alkaline mixed solvent is 10.

10. The preparation method according to claim 2, characterized in that, The concentration of nickel salt in alkaline mixed solvent is 0.015~0.02 mol / L.

11. The preparation method according to claim 10, characterized in that, The concentration of nickel salt in the alkaline mixed solvent is 0.0176 mol / L.

12. The preparation method according to claim 2, characterized in that, The temperature of the solvothermal reaction is 100~120℃, and the reaction time is 70~80 h.

13. The application of the metal-organic framework material based on doimidazole ligands according to claim 1 or the metal-organic framework material based on doimidazole ligands prepared by any one of claims 2 to 12 as a catalyst.

14. The application as described in claim 13, characterized in that, The applications include the degradation of organic pollutants.

15. The application as described in claim 14, characterized in that, The organic pollutant includes methylene blue.

16. The application as described in claim 15, characterized in that, The pH of the solution is 3-10 when degrading methylene blue.

Images