A dual-site heterometallic MOF material for NO adsorption and its preparation method and application

Abstract

This invention discloses a dual-site heterovalent metal MOF material for NO adsorption, its preparation method, and its application, belonging to the field of gas adsorption materials. The chemical formula of this material is [Cu]. Ⅰ (Cu Ⅱ )4(2-TPY)2(IA ‑ )3(NO3 ‑ )2I ‑ O 2‑ ]·(NO3 ‑ The material was prepared by a solvothermal method using the reaction of bis(terpyridine), isonicotinic acid, and cuprous iodide. This material possesses a three-dimensional structure and Cu... Ⅰ / Cu Ⅱ The bimetallic active sites exhibit excellent thermal stability, high specific surface area, and highly selective adsorption capacity for NO. This invention solves the problems of low NO adsorption capacity and poor selectivity of traditional adsorbents in complex flue gas, and can efficiently achieve NO / CO separation. It is suitable for the deep removal and resource utilization of NO in industrial waste gas, and has good cycle stability and application prospects.

Description

Technical Field

[0001] This invention belongs to the field of gas adsorption materials technology, and particularly relates to a dual-site heterovalent metal MOF material for NO adsorption, its preparation method and application. Background Technology

[0002] Nitric oxide (NO), a typical air pollutant, mainly originates from coal-fired flue gas, vehicle exhaust, and high-temperature combustion in industrial processes. It not only causes environmental problems such as acid rain and photochemical smog, disrupting the balance of ecosystems, but also directly harms the human respiratory system, exacerbates smog formation, and threatens public health. With increasingly stringent environmental regulations, the efficient removal of NO from industrial waste gas has become an urgent need in the field of environmental governance.

[0003] Currently, traditional NO adsorption materials such as activated carbon and molecular sieves are widely used, but they generally suffer from drawbacks such as low adsorption capacity, poor selectivity, susceptibility to moisture and carbon dioxide interference, and weak cycle stability. Especially in complex flue gas compositions, these materials struggle to achieve deep NO removal and resource utilization. In recent years, metal-organic frameworks (MOFs) have shown great potential in gas adsorption and separation due to their ultra-high specific surface area, tunable pore structure, and abundant active sites. However, existing single-metal MOF materials often rely solely on the interaction between a single valence state metal site and NO, resulting in limited adsorption affinity and low efficiency in capturing low-concentration NO, failing to meet the practical industrial demand for efficient and highly selective NO removal.

[0004] Therefore, there is an urgent need to develop a novel MOF material with a dual-site heterovalent metal synergistic effect, which will become a key technological breakthrough for improving NO adsorption performance. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a dual-site heterovalent metal MOF material for NO adsorption, its preparation method, and its application.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A dual-site heterovalent metal MOF material for NO adsorption has a heterovalent metal structure comprising n (n is a positive integer) repeating units, the chemical structural formula of which is [Cu Ⅰ (Cu Ⅱ )4(2-TPY)2(IA - )3(NO3 - )2I - O 2- ]·(NO3 - ); Among them, 2-TPY is a bis-terpyridine, IA -For deprotonated isonicotinic acid, the structure of 2-TPY is shown in Formula I, IA - The structure is shown in Equation II: .

[0007] Optionally, the dual-site heterovalent metal MOF material belongs to the monoclinic crystal system, with space group P21 / n, and cell parameters a=14.8299(8) Å, b=38.467(2) Å, c=22.1982(12) Å, α=90(0)°, β=107.919(2)°, γ=90(0)°, V=12048.9(12) Å. 3 .

[0008] The preparation method of the above-mentioned dual-site heterovalent metal MOF material includes the following steps: A reaction system is formed by mixing bis(terpyridine), isonicotinic acid, and cuprous iodide in a solvent. Nitric acid is then added to the reaction system and sonicated. The mixture is then subjected to a solvothermal reaction, cooling, washing, and drying to obtain the final product.

[0009] Optionally, the molar ratio of the bis(terpyridine), isonicotinic acid, and cuprous iodide is 2:3:5.

[0010] Optionally, the solvent is a mixture of N,N-dimethylformamide (DMF) and methanol in a volume ratio of 2:1.

[0011] Optionally, the conditions for the ultrasonic treatment are: ultrasonic power of 300W and ultrasonic time of 3min.

[0012] Optionally, the solvothermal reaction conditions are: reaction at 90°C for 36 hours.

[0013] Optionally, the washing process involves first washing with DMF solution and then washing with methanol.

[0014] Optionally, the drying conditions are: vacuum drying at 25–50°C for 4–6 hours.

[0015] The above-mentioned dual-site heterovalent metal MOF materials are used for the removal and separation of NO from coal-fired flue gas, motor vehicle exhaust gas and industrial waste gas.

[0016] Compared with the prior art, the present invention has the following advantages and technical effects: (1) This invention utilizes a two-site heterovalent metal (Cu) Ⅰ / Cu Ⅱ Coordinated regulation and precise control of metal valence state and coordination environment to construct Cu Ⅰ Cu Ⅱ-MOF materials significantly improve NO adsorption capacity and selectivity; heterovalent Cu Ⅰ / Cu Ⅱ The introduction of ions replaces the traditional single metal sites and introduces unsaturated bimetallic active centers with stronger coordination affinity for NO, thereby achieving preferential adsorption and efficient capture of NO, and thus achieving efficient separation of NO / CO. (2) This invention synthesizes dual-site heterovalent metal Cu in one step via a solvothermal method. Ⅰ Cu Ⅱ -MOF adsorbents are easy to prepare under mild conditions, are easy to mass-produce, and have excellent structural stability and recyclability. They have good prospects for industrial applications, especially suitable for the efficient removal and resource utilization of NO in coal-fired flue gas, motor vehicle exhaust gas and industrial waste gas, achieving efficient NO capture and separation. Attached Figure Description

[0017] 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 undue limitation of the invention. In the drawings: Figure 1 The dual-site heterovalent metal Cu prepared in Example 1 of this invention Ⅰ Cu Ⅱ -Analytical diagram of a single crystal of MOF material; Figure 2 The dual-site heterovalent metal Cu prepared in Example 1 of this invention Ⅰ Cu Ⅱ Comparison of characteristic peaks between X-ray powder diffraction test results and single-crystal simulation results of MOF materials; Figure 3 The dual-site heterovalent metal Cu prepared in Example 1 of this invention Ⅰ Cu Ⅱ -Fourier transform infrared image of MOF material; Figure 4 The dual-site heterovalent metal Cu prepared in Example 1 of this invention Ⅰ Cu Ⅱ -Thermogravimetric spectrum of MOF materials; Figure 5 The dual-site heterovalent metal Cu prepared in Example 1 of this invention Ⅰ Cu Ⅱ XPS spectra of MOF materials; Figure 6 The dual-site heterovalent metal Cu prepared in Example 1 of this invention Ⅰ Cu Ⅱ -Irothermal adsorption-desorption experimental spectrum of nitrogen gas in MOF materials; Figure 7The dual-site heterovalent metal Cu prepared in Example 1 of this invention Ⅰ Cu Ⅱ -NO adsorption and separation experiment of MOF materials; Figure 8 This is a structural diagram of the material prepared in Comparative Example 1; Figure 9 The single-crystal analytical structure of the material prepared in Comparative Example 1 is shown. Figure 10 The PXRD pattern of the material prepared in Comparative Example 1; Figure 11 The infrared spectrum of the material prepared in Comparative Example 1; Figure 12 Thermogravimetric spectrum of the material prepared in Comparative Example 1; Figure 13 XPS spectra of the material prepared in Comparative Example 1; Figure 14 The nitrogen isothermal adsorption-desorption experimental curves of the material prepared in Comparative Example 1 are shown. Figure 15 The gas separation curve is shown for the material prepared in Comparative Example 1. Detailed Implementation

[0018] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0019] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0020] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0021] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This specification and embodiments are merely exemplary.

[0022] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0023] The bimetallic MOF provided by this invention is a MOF material with a heterovalent metal structure containing copper sites of different valence states. The metal centers are connected by organic ligands, resulting in a regular and stable structure. The chemical structural formula of the bimetallic MOF material is [Cu]. Ⅰ (Cu Ⅱ )4(2-TPY)2(IA - )3(NO3 - )2I - O 2- ]·(NO3 - ), named Cu Ⅰ Cu Ⅱ -MOF.

[0024] This dual-site heterovalent metallic MOF material belongs to the monoclinic crystal system, with space group P21 / n and cell parameters: a=14.8299(8) Å, b=38.467(2) Å, c=22.1982(12) Å, α=90(0)°, β=107.919(2)°, γ=90(0)°, V=12048.9(12) Å. 3 In the chemical structure of dual-site heterovalent metal MOF materials, 2-TPY represents bis-terpyridine, and IA... - For deprotonated isonicotinic acid, the structure of 2-TPY is shown in Formula I, IA - The structure is shown in Equation II.

[0025] The crystal structure of this dual-site heterovalent metal MOF material includes several repeating units, each of which consists of a Cu... Ⅰ Four Cu Ⅱ Two 2-TPY, three IA - Two NO3 - , an I - An O 2- And a free NO3 - Composition, in which Cu ⅡThe five-coordinate environment is formed by the three nitrogen atoms of the terpyridine ligand, the carboxyl group on the deprotonated isonicotinic acid, and the nitrate group. Cu Ⅰ It is a four-coordinate environment formed by the coordination of two deprotonated isonicotinic acid pyridine N atoms, one I atom, and one oxygen atom. Ⅰ With Cu Ⅱ The elements are linked by deprotonated isonicotinic acid, forming the simplest element, as shown in Equation III. The simplest elements are linked by nitrate groups and arranged in an alternating spatial arrangement to form a three-dimensional MOF structure.

[0026] Formula III This invention provides a method for preparing the aforementioned dual-site heterovalent metal MOF material, using bis(terpyridine), isonicotinic acid, and cuprous iodide as raw materials, and a mixed solution of N,N-dimethylformamide and nitric acid as solvent, prepared by a solvothermal method. The preparation process is simple and the reaction conditions are mild.

[0027] The specific preparation process is as follows: Step 1: Mix bis(terpyridine), isonicotinic acid, and cuprous iodide separately in the solvent to form a reaction system. The molar ratio of bis(terpyridine), isonicotinic acid, and cuprous iodide is 2:3:5. In the solvent, the volume ratio of N,N-dimethylformamide (DMF) to methanol is 2:1. The volume ratio of cuprous iodide to solvent is 5 mmol: (7-9.5) mL.

[0028] Step 2: Then, at room temperature, add 50 μL of nitric acid to the reaction system, sonicate the reaction system for 3 min, and place it in a sealed reaction vessel.

[0029] Step 3: Then, the sealed container is placed at 90°C for 36 hours to react. Finally, it is naturally cooled, filtered, washed, and dried to obtain a bulk crystal, which is the dual-site heterovalent metal MOF material.

[0030] In some optional embodiments, the washing in step 3 involves first washing with DMF solution, followed by washing with methanol; the drying is performed under vacuum at 25–50°C for 4–6 hours to obtain the dual-site heterovalent metal Cu. Ⅰ Cu Ⅱ -MOF materials.

[0031] This invention also discloses that the dual-site heterovalent metal MOF material can be applied to NO adsorption and flue gas purification. It has been demonstrated that the dual-site heterovalent metal MOF material exhibits good adsorption efficiency and good cycle stability for the adsorption and separation of NO in flue gas and industrial waste gas at room temperature.

[0032] Unless otherwise specified, "room temperature" in this invention refers to 20-30℃.

[0033] All raw materials used in this invention were purchased from the market.

[0034] The technical solution of the present invention will be further illustrated by the following embodiments.

[0035] Example 1 A method for preparing a dual-site heterovalent metal MOF material includes the following steps: Step 1: Mix 2 mmol of bis(terpyridine), 3 mmol of isonicotinic acid, and 5 mmol of cuprous iodide in 9 mL of solvent to form a reaction system; The solvent is a mixture of N,N-dimethylformamide (DMF) and methanol in a volume ratio of 2:1.

[0036] Step 2: Then, at room temperature, add 50 μL of nitric acid to the reaction system, sonicate the reaction system for 3 min (sonication power of 300 W), and place it in a sealed reaction vessel.

[0037] Step 3: Then, place the sealed container at 90°C for 36 hours to react. Finally, allow it to cool naturally, filter, wash with DMF solution first and then with methanol, and then vacuum dry at 40°C for 4 hours to obtain a bulk crystal, which is the dual-site heterovalent metal MOF material.

[0038] Figure 1 The dual-site heterovalent metal Cu prepared in Example 1 of this invention Ⅰ Cu Ⅱ - Single-crystal analytical diagram of MOF material. From the diagram, it can be seen that Cu in this material... Ⅰ With Cu Ⅱ Ions are linked by deprotonated isonicotinic acid ligands to form basic units, and nitrate ions are arranged in a spatially staggered manner to form a three-dimensional MOF structure, which intuitively shows the coordination environment of the heterovalent bimetallic active center.

[0039] Figure 2 The dual-site heterovalent metal Cu prepared in Example 1 of this invention Ⅰ Cu Ⅱ - A comparison of characteristic peaks from X-ray powder diffraction (PXRD) tests and single-crystal simulations of MOF materials. The figure shows that the experimentally measured diffraction peaks highly coincide with the diffraction peaks simulated based on the single-crystal structure, and the peaks are sharp, indicating that the synthesized crystal sample has high purity and good crystallinity, and that the experimental sample is consistent with the theoretical structure.

[0040] Figure 3 The dual-site heterovalent metal Cu prepared in Example 1 of this invention Ⅰ Cu ⅡThe Fourier transform infrared (FT-IR) spectrum of the MOF material shows characteristic absorption peaks at specific wavenumbers, attributed to the C=N stretching vibration of the 2-TPY ligand, the C=O stretching vibration of the carboxyl group in the isonicotinic acid ligand, and the nitrate ion. This demonstrates the successful coordination of the organic ligand with the metal center and the formation of the target MOF material.

[0041] Figure 4 The dual-site heterovalent metal Cu prepared in Example 1 of this invention Ⅰ Cu Ⅱ The thermogravimetric (TGA) spectrum of the MOF material shows that the weight loss is minimal in the range of room temperature to 300℃, mainly due to solvent molecule desorption. The framework decomposition temperature is above 350℃, indicating that the Cu... Ⅰ Cu Ⅱ -MOF materials have excellent thermal stability and can meet the temperature requirements of industrial flue gas treatment.

[0042] Figure 5 The dual-site heterovalent metal Cu prepared in Example 1 of this invention Ⅰ Cu Ⅱ - X-ray photoelectron spectroscopy (XPS) spectrum of MOF material. The image shows the presence of Cu in the spectrum. Ⅰ (Cu(II)) and Cu Ⅱ The characteristic binding energy peak of (copper ions) confirms the presence of a two-site heterovalent metal (Cu) in the material. Ⅰ / Cu Ⅱ The successful introduction and coexistence of heterovalent metal structures validates the design of heterovalent metal structures.

[0043] Figure 6 The dual-site heterovalent metal Cu prepared in Example 1 of this invention Ⅰ Cu Ⅱ -The nitrogen isothermal adsorption-desorption experimental spectrum of the MOF material shows that the material has a high specific surface area and abundant pore structure, which is conducive to the diffusion, adsorption and storage of gas molecules.

[0044] Figure 7 The dual-site heterovalent metal Cu prepared in Example 1 of this invention Ⅰ Cu Ⅱ- The NO and CO adsorption separation breakthrough test curves of the MOF material (the test conditions were: 0.2g of the material prepared in Example 1 was added under the conditions of 480ppm NO, 1200ppm CO, and a total flow rate of 200mL / min, and the NO and CO adsorption separation breakthrough test was carried out at 150℃. The test conditions of the following comparative examples were the same). It can be seen from the figure that the breakthrough time of NO gas is significantly longer than that of CO gas, and NO is preferentially adsorbed and retained in the column in the mixed gas flow. This indicates that the material has extremely high adsorption affinity and selectivity for NO and can achieve efficient separation of NO / CO.

[0045] Comparative Example 1 A method for preparing a metallic MOF material includes the following steps: Step 1: Mix 1 mmol of bis(terpyridine), 2 mmol of 4-pyridin-4-ylbenzoic acid, and 2 mmol of cuprous iodide in a solvent to form a reaction system, and then place it in a sealed container; The molar ratio of bis(terpyridine), 4-pyridin-4-ylbenzoic acid, and cuprous iodide is 1:2:2; The solvent is a mixture of N,N-dimethylformamide (DMF) and methanol in a volume ratio of 2:1.

[0046] Step 2: Place the sealed container at 90°C for 72 hours to react. Finally, allow it to cool naturally, filter, wash, and dry to obtain bulk crystals, which is the metal MOF material.

[0047] The chemical structural formula of the metal MOF material prepared in Comparative Example 1 is [(Cu Ⅱ )2(2-TPY)(4-PBA - )2], named Cu Ⅱ -MOF. This metallic MOF material belongs to the monoclinic crystal system, space group C2 / c, and its cell parameters are: a=30.416(2) Å, b=28.1130(19) Å, c=221.4262(14) Å, α=90(0)°, β=113.268(3)°, γ=90(0)°, V=12048.9(12) Å. 3 In the chemical structural formula, 2-TPY is bis-terpyridine, and 4-PBA... - It is deprotonated 4-pyridin-4-ylbenzoic acid.

[0048] The crystal structure of this metallic MOF material consists of several repeating units, each of which is composed of two Cu atoms. Ⅱ One 2-TPY and two 4-PBA - Composition, in which Cu ⅡThe MOF structure is a five-coordinate environment formed by the three nitrogen atoms of the terpyridine ligand, the carboxyl group of the deprotonated 4-pyridine-4-ylbenzoic acid, and the nitrogen atom of the pyridine. Each repeating unit is connected by a protonated 4-pyridine-4-ylbenzoic acid atom and is arranged in an alternating spatial arrangement to form a three-dimensional MOF structure.

[0049] Figure 8 The single-metal MOF material (Cu) prepared for Comparative Example 1 Ⅱ The chemical structure diagram of the -MOF shows that the material contains only Cu in a single valence state. Ⅱ Metal center, lacking Cu Ⅰ / Cu Ⅱ Heterovalent bimetallic synergistic active sites.

[0050] Figure 9 The figure shows the single-crystal analytical structure of the material prepared in Comparative Example 1. It can be seen from the figure that the copper ions in this material only exhibit a five-coordinate environment, and no cuprous iodide or low-valent copper was observed to be introduced. Structurally, it is similar to the Cu of the present invention. Ⅰ Cu Ⅱ - There are significant differences in MOF.

[0051] Figure 10 The PXRD pattern of the material prepared in Comparative Example 1 shows the positions of its diffraction peaks compared to... Figure 2 The materials prepared in Example 1 of this invention are completely different, proving that the comparative material has a different crystal structure and relatively poor crystallinity.

[0052] Figure 11 The infrared spectrum of the material prepared in Comparative Example 1 shows that it lacks certain characteristic peaks of the specific isonicotinic acid and bis-terpyridine co-coordination in the material of this invention, indicating that its chemical composition and coordination mode are different from those of the embodiments of this invention.

[0053] Figure 12 The thermogravimetric spectrum of the material prepared in Comparative Example 1 shows that the thermal decomposition initiation temperature of this material is lower than that of the material of the present invention, the skeleton stability is poor, and it is prone to collapse under high temperature environment.

[0054] Figure 13 The XPS spectrum of the material prepared in Comparative Example 1 shows that only Cu is present. Ⅱ The characteristic peaks indicate that it is a metal-organic framework material with a single valence state.

[0055] Figure 14 The figure shows the nitrogen isothermal adsorption-desorption experimental curve of the material prepared in Comparative Example 1. It can be seen from the figure that its nitrogen adsorption capacity is lower than that of the present invention, and its specific surface area and porosity are smaller, which is not conducive to efficient gas adsorption.

[0056] Figure 15 The figure shows the gas separation curve of the material prepared in Comparative Example 1. It can be seen from the figure that the difference in breakthrough time between NO and CO is small, the separation effect is not obvious, and the adsorption capacity and selectivity are far lower than those of the dual-site heterovalent metal MOF material prepared in Example 1 of this invention.

[0057] In summary, Comparative Example 1 uses only Cu in a single valence state. Ⅱ The ions and single ligands have relatively simple structures and lack synergistic effects between heterovalent metals, resulting in low overall crystallinity, thermal stability, and specific surface area of ​​the material. In contrast, Example 1 innovatively introduces Cu. Ⅰ / Cu Ⅱ A heterovalent bimetallic system was constructed, assembled with a dual ligand of 2-TPY and deprotonated isonicotinic acid (IA⁻). This unique structural design not only successfully created a dual-site synergistic active center containing two copper ions with different valence states, but also significantly improved the physical properties of the material by optimizing the three-dimensional pore structure, giving it excellent thermal stability and a higher specific surface area, providing an ideal material basis for the efficient adsorption and diffusion of gas molecules.

[0058] Based on the aforementioned structural advantages, Example 1 demonstrates technical effects in practical applications that Comparative Example 1 cannot match. Benefiting from Cu Ⅰ / Cu Ⅱ Due to the difference in electronic structure and synergistic regulation of the two adsorption sites, Example 1 exhibited extremely strong adsorption affinity and high selectivity for NO molecules. In the gas separation breakthrough experiment, Example 1 significantly prolonged the breakthrough time of NO, achieving efficient and precise separation of NO and CO; while Comparative Example 1, lacking specific strong adsorption sites, showed only a slight difference in adsorption capacity for NO and CO, making it difficult to meet the industrial requirements for deep NO removal.

[0059] In summary, Example 1, through the synergistic design of heterovalent bimetals and dual ligands, fundamentally solves the problems of low adsorption capacity and poor selectivity of traditional single-metal materials, and has extremely high application value in complex flue gas environments.

[0060] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A dual-site heterovalent metal MOF material for NO adsorption, characterized in that, comprising n repeating units, the chemical structural formula of the repeating unit is [Cu Ⅰ (Cu Ⅱ )4(2-TPY)2(IA - )3(NO3 - )2I - O 2- ]·(NO3 - ); n is a positive integer; Among them, 2-TPY is a bis-terpyridine, IA - For deprotonated isonicotinic acid, the structure of 2-TPY is shown in Formula I, IA - The structure is shown in Equation II: 。 2. The dual-site heterovalent metal MOF material for NO adsorption according to claim 1, characterized in that, The dual-site heterovalent metallic MOF material belongs to the monoclinic crystal system, space group P21 / n, and has the following cell parameters: a = 14.8299(8) Å, b = 38.467(2) Å, c = 22.1982(12) Å, α = 90(0)°, β = 107.919(2)°, γ = 90(0)°, V = 12048.9(12) Å. 3 .

3. A method for preparing a dual-site heterovalent metal MOF material as described in claim 1 or 2, characterized in that, Includes the following steps: A reaction system is formed by mixing bis(terpyridine), isonicotinic acid, and cuprous iodide in a solvent. Nitric acid is then added to the reaction system and sonicated. The mixture is then subjected to a solvothermal reaction, cooling, washing, and drying to obtain the final product.

4. The method for preparing a dual-site heterovalent metal MOF material according to claim 3, characterized in that, The molar ratio of the bis(terpyridine), isonicotinic acid, and cuprous iodide is 2:3:

5.

5. The method for preparing a dual-site heterovalent metal MOF material according to claim 3, characterized in that, The solvent is a mixture of N,N-dimethylformamide and methanol, with a volume ratio of 2:

1.

6. The method for preparing a dual-site heterovalent metal MOF material according to claim 3, characterized in that, The conditions for the ultrasonic treatment are: ultrasonic power of 300W and ultrasonic time of 3min.

7. The method for preparing a dual-site heterovalent metal MOF material according to claim 3, characterized in that, The conditions for the solvothermal reaction are: reaction at 90°C for 36 hours.

8. The method for preparing a dual-site heterovalent metal MOF material according to claim 3, characterized in that, The washing process involves first washing with DMF solution, followed by washing with methanol.

9. The method for preparing a dual-site heterovalent metal MOF material according to claim 3, characterized in that, The drying conditions are: vacuum drying at 25–50°C for 4–6 hours.

10. The application of the dual-site heterovalent metal MOF material as described in claim 1 or 2 in the removal and separation of NO from coal-fired flue gas, motor vehicle exhaust gas and industrial waste gas.

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