Preparation method of copper-based metal organic framework material for realizing gas capture based on thienyl tetracarboxylic acid ligand

Abstract

The invention discloses a preparation method of a copper-based metal organic framework material for realizing gas capture based on a thienyl tetracarboxylic acid ligand. The material realizes efficient capture of target gas through structural design. According to the preparation method disclosed by the invention, thiophene groups with electron-rich characteristics and sulfur heteroatoms are creatively used as key functional units to be introduced into tetracarboxylic acid ligand design and preparation of a copper-based metal organic framework material, so that the MOF material with strong electron donating capability and unique polarity is successfully prepared, and excellent adsorption capability on target gas is realized.

Description

Technical Field

[0001] This invention belongs to the fields of materials science and environmental engineering, particularly the design and application of metal-organic frameworks (MOFs). Specifically, it relates to a method for preparing copper-based metal-organic frameworks based on thienyltetracarboxylic acid ligands for gas capture. Background Technology

[0002] With the continuous expansion of global energy infrastructure and the acceleration of high-voltage electrification, the safe operation of power equipment and the control of environmental emissions have become critical issues. Sulfur hexafluoride (SF6), due to its excellent insulation and arc-quenching properties, is widely used in high-voltage equipment such as gas-insulated switchgear (GIS). However, when partial discharge, overheating, or arcing faults occur inside the equipment, SF6 decomposes, producing a variety of characteristic gases, including sulfur dioxide (SO2), carbon tetrafluoride (CF4), and carbon dioxide (CO2). These gaseous components are not only corrosive and toxic, significantly reducing the strength of insulating media and accelerating the aging of solid insulating materials, thus threatening the reliability of power grid operation; furthermore, perfluorocarbons such as CF4 have extremely high global warming potential. Therefore, developing novel adsorbent materials capable of efficiently capturing and selectively separating key components (especially SO2, CF4, and CO2) from the SF6 fault decomposition mixture is of urgent practical significance for promoting online monitoring of power equipment status, fault early warning, purification and recovery of insulating gases, and achieving environmentally friendly power grid operation and maintenance.

[0003] Metal-organic frameworks (MOFs), with their precisely customizable pore structures, high specific surface areas, and functionalizable internal surface chemistry, provide an ideal platform for the adsorption and separation of multi-component gases. Existing research largely focuses on enhancing the adsorption of single gases (such as SO2) by introducing nitrogen-containing basic sites or open metal sites. However, in complex mixed systems such as SF6 decomposition gas, which contains polar molecules (SO2), weakly polar molecules (CF4), and linear molecules (CO2), traditional MOFs often face problems such as insufficient adsorption selectivity, unclear competitive adsorption mechanisms between different components, and rapid degradation of adsorption performance under actual operating conditions. In particular, the lack of comprehensive functional sites and suitable pore environments capable of synergistically recognizing and differentially adsorbing SO2, CF4, and CO2 restricts their practical application in complex gas handling scenarios in the power industry. Summary of the Invention

[0004] To address the aforementioned challenges, this study designed and synthesized a novel sulfur-containing functionalized copper-based MOF material (Cu-L1). This material is constructed by coordination self-assembly of an organic ligand with a rigid π-conjugated structure and multiple carboxylic acid coordination sites, 4,4',4",4'"-(thieno[3,2-b]thiophene-2,3,5,6-tetrayl)tetrabenzoic acid 4,4',4'',4'''-(thieno[3,2-b]thiophene-2,3,5,6-tetrayl)tetrabenzoic acid (H4L-1), and a copper cluster unit. Its innovation lies in the fact that, compared with the simple thiophene dicarboxylic acid or ligands containing thiophene carboxyl groups in the prior art, the 4,4',4'',4'''-(thieno[3,2-b]thiophene-2,3,5,6-tetramethyl)tetrabenzoic acid (H4L-1) used in this invention has significant advantages in ligand structure: its core is a rigid, more planar thiophene dithiophene unit, extending to four carboxylic acid groups, forming a multidentate, highly conjugated extended ligand system. This structure not only enhances the rigidity and symmetry of the ligand, which is beneficial for constructing stable and regular three-dimensional channels, but more importantly, it introduces a higher density of electron-rich sulfur sites, and the sulfur atoms are in a more concentrated π-conjugated environment, thereby generating stronger S···O dipole interactions and charge transfer effects with SO2 molecules. In contrast, the simple ligands used in existing technologies, such as 2,5-thiophene dicarboxylic acid, have low sulfur atom electron cloud density and few coordination sites, resulting in MOF structures that are generally less stable and lack the ability to recognize multiple gases collaboratively. Experimental data show that the Cu-L1 prepared in this invention exhibits an adsorption capacity of up to 8.0 mmol·g⁻¹ for SO₂ at 298 K and 1 bar. -1 This is significantly higher than that of most reported MOF materials (such as DUT-67, which has an SO2 adsorption capacity of ~7.3 mmol·g). -1The material exhibits excellent comprehensive capture and selective separation capabilities in SO2 / CO2 / SF6 / CF4 mixed gases (IAST > 20). In summary, the inherent thiophene-thiophene units within the framework provide electron-rich sulfur (S) sites, enabling specific and strong interactions with SO2 molecules (such as S···O dipole interactions and charge transfer), thus achieving efficient and highly selective capture. Simultaneously, the material possesses well-defined and appropriately sized nanoscale channels, which, through the synergistic effect of pore size sieving and surface polarity, effectively physi-adsorb and differentially accommodate coexisting gases such as CO2. This study aims to systematically investigate the comprehensive adsorption performance and separation selectivity of Cu-L1 for SF6 / SO2 / CF4 / CO2 mixed gases, elucidating the synergistic mechanism of sulfur sites and pore structure in multi-component competitive adsorption. This work not only provides a novel molecular design strategy and material example for developing highly efficient adsorbents for SF6 failure decomposition characteristic gases, but also lays an important material foundation for the synergistic removal and resource recovery technologies of multiple target pollutants in complex industrial waste gases.

[0005] The purpose of this invention is to provide a method for preparing copper-based metal-organic framework materials for gas capture based on thieno[3,2-b]thiophene-2,3,5,6-tetrayl)tetrabenzoic acid ligand 4,4',4'',4'''-(thieno[3,2-b]thiophene-2,3,5,6-tetrayl)tetrabenzoic acid (H4L-1) ligand with Cu 2+ By effectively coordinating and constructing metal clusters and synthesizing framework materials through rational design, copper-based metal-organic framework materials with good SO2 and CO2 gas capture capabilities were successfully prepared.

[0006] To achieve the above objectives, the present invention provides a method for preparing a copper-based metal-organic framework material for gas trapping based on thienyltetracarboxylic acid ligands, comprising the following steps: 4,4',4'',4'''-(thieno[3,2-b]thiophene-2,3,5,6-tetramethyl)tetrabenzoic acid (H4L-1) and copper nitrate trihydrate (Cu(NO3)2·3H2O) were added to DMF to obtain a mixed solution. Acetonitrile and concentrated nitric acid were added to the mixed solution, and the mixture was ultrasonically treated. After ultrasonic treatment, the mixture was heated to obtain blue hexagonal block crystals. The obtained crystals were washed by centrifugation with DMF and ethanol to obtain the copper-based metal-organic framework material.

[0007] As a further optimization of the preparation method of the copper-based metal-organic framework material for gas capture based on thieno[3,2-b]thiophene-2,3,5,6-tetrayl)tetrabenzoic acid, the structural formula of 4,4',4'',4'''-(thieno[3,2-b]thiophene-2,3,5,6-tetrayl)tetrabenzoic acid is as follows: As a further optimization of the preparation method of a copper-based metal-organic framework material for gas capture based on thienyltetracarboxylic acid ligand of the present invention, the molar ratio of H4L-1 and Cu(NO3)2·3H2O is 1:2.

[0008] As a further optimization of the preparation method of a copper-based metal-organic framework material based on thienyltetracarboxylic acid ligand for gas capture according to the present invention: the amount of DMF solvent added in the step is 5.0 mL, the amount of acetonitrile solvent added is (5.0 mL), and the volume ratio of DMF solvent to acetonitrile solvent is 1:1.

[0009] As a further optimization of the preparation method of the copper-based metal-organic framework material for gas capture based on thienyltetracarboxylic acid ligand of the present invention: the amount of concentrated nitric acid added in the step is 200 µL.

[0010] As a further optimization of the preparation method of a copper-based metal-organic framework material based on thienyltetracarboxylic acid ligand for gas capture according to the present invention: the power of water bath ultrasound is 200-300 W, and the cumulative ultrasound time is 15-20 min.

[0011] As a further optimization of the preparation method of the copper-based metal-organic framework material based on thienyltetracarboxylic acid ligand for gas capture according to the present invention: the oven heating temperature is 90 °C and the heating time is 72 h.

[0012] As a further optimization of the preparation method of the copper-based metal-organic framework material of the present invention, which captures the decomposition products of SF6 insulating gas by introducing electron-rich sulfur (S) sites and a suitable cavity environment: the centrifugation speed in the above step is 8000-10000 r·min. -1 Centrifuge for 4-5 minutes, and perform centrifugation and washing at least 5 times.

[0013] As a further optimization of the preparation method of the copper-based metal-organic framework material for gas capture based on thienyltetracarboxylic acid ligand of the present invention: the mass of Cu-L1 powder used for SO2, CO2, SF6 and CF4 adsorption tests after drying is not less than 100 mg.

[0014] Application: The copper-based metal-organic framework material is used in the adsorption of SO2 or CO2 gases.

[0015] Application: The copper-based metal-organic framework material is used for capturing the decomposition products of SF6 insulating gas.

[0016] Furthermore, the copper-based metal-organic framework material is used in the comprehensive adsorption of SF6 / SO2 / CF4 / CO2 mixed gases and the selective separation of SO2 and CO2 gases.

[0017] The copper-based metal-organic framework material for gas capture based on thienyltetracarboxylic acid ligands, as described in this invention, is prepared by the above-described method. Overall, compared with existing technologies, the above-described technical solution conceived by this invention has the following beneficial effects: 1. This invention uses a solvothermal method, which only requires dissolving and mixing the ligand and metal salt in a solvent, then sonicating the mixture to homogenize it and transferring it to a glass bottle. The reaction can then be carried out in an oven for the required time. The reaction conditions are relatively simple and do not involve overly complicated steps, resulting in strong repeatability. The yield is high, and increasing the amount of ligand can produce more Cu-L1 materials. The equipment required for this invention is simple and the cost is low.

[0018] 2. The introduction of electron-rich sulfur (S) sites and a suitable pore environment can effectively regulate the chemical microenvironment of MOF materials, enabling them to form strong interactions with SO2 and CO2, thus significantly improving the material's ability to capture SO2 and CO2. Specifically, Cu-L-FA exhibits a maximum SO2 and CO2 adsorption capacity of 8.0 mmol·g⁻¹ at 298 K / bar. -1 and 2.8 mmol·g -1 . Attached Figure Description

[0019] Figure 1 This is an optical microscope image of Cu-L1 prepared in Example 1; Figure 2 The images are scanning electron microscope (SEM) image (a) and energy dispersive spectroscopy (EDS) image (b) of Cu-L1 prepared in Example 1. Figure 3 The XRD pattern of Cu-L1 prepared in Example 1 is shown. Figure 4 The adsorption of SO2, CO2, SF6 and CF4 by Cu-L1 prepared in Example 1 at temperatures of 273 K (a) and 298 K (b) is shown. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other. The invention will be further described in detail below with reference to specific embodiments.

[0021] <Example 1> The following description uses the preparation method of Cu-L with SO2 capture capability as an example. The preparation method includes the following steps: (1) Preparation of the mixture: 4,4',4",4'"-(thieno[3,2-b]thiophene-2,3,5,6-tetrayl)tetrabenzoic acid 4,4',4'',4'''-(thieno[3,2-b]thiophene-2,3,5,6-tetrayl)tetrabenzoic acid (H4L-1) (20 mg) and copper nitrate trihydrate (Cu(NO3)2·3H2O) (40 mg) were added to 5 mL of DMF. Then, acetonitrile (5 mL) and 68 wt% concentrated nitric acid solution (200 µL) were added to the solution to obtain a mixed solution.

[0022] (2) Preparation of Cu-L1 crystals The above mixture was subjected to ultrasonic treatment (ultrasonic power 200W, time 15 minutes). After ultrasonication, the mixture was placed in a high-temperature resistant glass bottle and heated in an oven at 90 ℃ for 72 h. After the reaction, the resulting blue hexagonal blocky single crystals were washed repeatedly by centrifugation with DMF and ethanol at a speed of 8000 r·min. -1 The centrifugation time was approximately 5 minutes, and the centrifugation and washing operation was performed no less than 5 times to finally obtain Cu-L1 metal-organic framework material.

[0023] (3) Cu-L1 material pretreatment Cu-L single crystal powder was placed in a vacuum drying oven at 120 °C for 12 hours to remove moisture and volatile substances. The dried sample was then cooled to room temperature under an inert gas atmosphere.

[0024] (4) Adsorption tests for SO2, CO2, SF6, and CF4 Purge the test system with inert gas (N2) for 15 - 30 minutes to ensure that there is no impurity gas in the equipment. Place the pretreated Cu-L single crystal powder evenly in the sample chamber of the adsorption test equipment to ensure good dispersion. Slowly introduce known concentrations of SO2, CO2, SF6, CF4 gases (1000 ppm) into the test equipment, ensure stable gas flow, set the test temperatures (0 °C and 25 °C) respectively, keep the temperature constant, and record the data.

[0025] <Morphology and Structure Characterization of Cu-L1> A. Morphology Characterization Take 1 mL of the dispersion of the material prepared in Example 1 and add it to centrifuge tubes respectively. Add 6 mL of ethanol for dilution, take 15 μL and drop it onto a glass slide, and observe it under an optical microscope.

[0026] As Figure 1 shown, it can be seen from the optical microscope photos that the morphology of Cu-L presents uniform hexagonal blocks.

[0027] Take 1 mL of the dispersion of the material prepared in Example 1 and add it to centrifuge tubes respectively. Add 6 mL of ethanol for dilution, take 6 μL and drop it onto a silicon wafer, and observe it under a scanning electron microscope.

[0028] As Figure 2 shown in a, it can be seen from the scanning electron microscope (SEM) photos that the morphology of Cu-L presents uniform hexagonal blocks. As Figure 2 shown in b, it can be seen from the energy spectrum diagram (EDS) photos that C, O, Cu, and S elements are evenly distributed in the crystal.

[0029] B. Structure Characterization Take 10 mg of the Cu-L1 material prepared in Example 1 for XRD testing.

[0030] As Figure 3 shown, the powder XRD pattern of the copper-based metal-organic framework material prepared in this invention has sharp and narrow diffraction peaks, indicating good crystallinity of the material, which shows that the compound prepared in this invention has good crystallinity and is a pure phase, and at the same time has the characteristic peaks of MOF materials.

[0031] <SO2, CO2, SF6, CF4 Adsorption Performance of Cu-L1 Material> Take 100 mg of the Cu-L1 material prepared in Example 1 for SO2, CO2, SF6, CF4 gas adsorption testing.

[0032] The specific gas adsorption process is as follows: First, Cu-L1 powder is placed in a vacuum drying oven at 120℃ and dried for 12 hours to remove moisture and volatile substances. Then, the dried sample is cooled to room temperature under an inert gas atmosphere. The adsorption test system is purged with inert gas (N2) for 15-30 minutes to ensure the absence of impurity gases. The pretreated Cu-L1 powder is then evenly placed in the sample chamber of the adsorption test equipment, ensuring good dispersion.

[0033] After the sample is placed, slowly introduce 1000 ppm of test gas, then set the flow rate to the desired value (e.g., 50 mL / min). -1 The sample is continuously introduced for 4-6 hours to ensure sufficient contact with the test gas. A gas analyzer is used to monitor the SO2 concentration changes within the sample chamber in real time, recording the initial concentration and concentration data at different time points during adsorption, every 10 minutes until adsorption equilibrium is reached.

[0034] like Figure 4 As shown, at 298 K and 1 bar, the maximum SO2 and CO2 adsorption capacities of Cu-L1 were 8.0 mmol·g, respectively. -1 and 2.8 mmol·g -1 Cu-L1 exhibited higher SO2 adsorption capacity at 298 K and 1 bar than previously reported MOF materials such as KAUST-8, SIFSIX-3-Ni, KAUST-7, CPL-1-NH2, and NPC-1. Adsorption tests on other gases (such as SF6 and CF4) were also conducted on the samples. The results showed that, among various gases, Cu-L1 achieved maximum SF6 and CF4 adsorption capacities of 0.5 mmol·g⁻¹ at 298 K and 1 bar, respectively. -1 and 0.9 mmol·g -1 As can be seen, the sample exhibits the highest adsorption capacity for SO2 gas. Simultaneously, the material demonstrates a high adsorption selectivity (IAST) for SO2 / CO2, approximately 40, indicating that it possesses excellent gas capture capability and adsorption selectivity for SO2 gas.

[0035] It is understood that the embodiments of the system described above are merely illustrative, and the units described as separate components may or may not be physically separated; they may be located in one place or distributed across different network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any inventive effort.

[0036] Furthermore, those skilled in the art should understand that in the application documents of this invention, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0037] Numerous specific details are set forth in the specification of embodiments of the present invention. However, it should be understood that embodiments of the present invention can be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification. Similarly, it should be understood that, in order to streamline the disclosure of embodiments of the present invention and aid in the understanding of one or more of the various inventive aspects, various features of the embodiments of the present invention are sometimes grouped together in a single embodiment, figure, or description thereof in the above description of exemplary embodiments of the present invention. However, this method of disclosure should not be construed as reflecting an intention that the claimed embodiments of the present invention require more features than those expressly recited in each claim. Rather, as reflected in the claims, inventive aspects lie in fewer than all features of a single foregoingly disclosed embodiment. Therefore, the claims following the detailed description are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of the present invention.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the embodiments of the present invention, and are not intended to limit them. Although the embodiments of the present invention have been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a copper-based metal-organic framework material for gas capture based on a thiophene-based tetracarboxylic acid ligand, characterized by: A copper-based metal-organic framework material with excellent capture capacity for SO2 and CO2 components is successfully prepared by coordination self-assembly of 4,4',4'',4'''-(thieno[3,2-b]thiophene-2,3,5,6-tetrayl) tetrabenzoic acid ligand and Cu 2+ A copper-based metal-organic framework material with excellent capture capacity for SO2 and CO2 components is successfully prepared by coordination self-assembly of 4,4',4'',4'''-(thieno[3,2-b]thiophene-2,3,5,6-tetrayl) tetrabenzoic acid ligand and Cu 2. The method according to claim 1, wherein the method is characterized by: Specifically comprising the following steps: 4,4',4'',4'''-(thieno[3,2-b]thiophene-2,3,5,6-tetrayl) tetrabenzoic acid and copper nitrate trihydrate are added into DMF to obtain a mixed solution, acetonitrile and concentrated nitric acid are added into the mixed solution, the mixed solution is subjected to ultrasonic treatment, after the ultrasonic treatment is completed, the mixed solution is subjected to heating treatment to obtain blue hexagonal block crystals, the obtained crystals are centrifugally washed with DMF and ethanol to obtain the copper-based metal organic framework material.

3. The method for preparing a copper-based metal organic framework material for gas capture based on thiophene-based tetracarboxylic acid ligand according to claim 2, characterized in that: The molar ratio of the added amounts of 4,4',4'',4'''-(thieno[3,2-b]thiophene-2,3,5,6-tetrayl) tetrabenzoic acid and copper nitrate trihydrate is 1:

2.

4. The method for preparing a copper-based metal organic framework material for gas capture based on thiophene-based tetracarboxylic acid ligand according to claim 2, wherein: The volume ratio of the DMF solvent and the acetonitrile solvent is 1:

1.

5. The method for preparing a copper-based metal organic framework material for gas capture based on thiophene-based tetracarboxylic acid ligand according to claim 2, characterized in that: The added amount of the concentrated nitric acid is 200 µL.

6. The method of claim 2, wherein the method of preparing a copper-based metal organic framework material for gas capture based on a thiophene-based tetracarboxylic acid ligand is characterized by: The ultrasonic power is 200-300 W, and the cumulative ultrasonic time is 15-20 min.

7. The method for preparing a copper-based metal organic framework material for gas capture based on thiophene-based tetracarboxylic acid ligand according to claim 2, wherein: The heating temperature is 90 ℃, and the heating time is 72 h.

8. The method for preparing a copper-based metal organic framework material for gas capture based on thiophene-based tetracarboxylic acid ligand according to claim 2, characterized in that: The centrifugal speed is 8000-10000 r·min -1 The centrifugal time is 4-5 min, and the centrifugal washing operation is not less than 5 times.

9. The copper-based metal organic framework material prepared by the preparation method in any one of claims 1-8.

10. Application of the copper-based metal organic framework material in claim 9 in comprehensive adsorption of SF6 / SO2 / CF4 / CO2 mixed gas and selective separation of SO2 and CO2 gas.

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