Zirconium-based MOF composite filter cloth and preparation method and application thereof

Abstract

The invention relates to the technical field of gas adsorption composite materials, in particular to zirconium-based MOF composite filter cloth and a preparation method and application thereof. The preparation method comprises the following steps: by taking a polyester non-woven fabric as a flexible carrier, sequentially carrying out alkali liquor activation and epoxy silane surface treatment to construct an active interface layer rich in epoxy groups; synthesizing a difunctional organic ligand simultaneously containing carboxylic acid and thioether functional groups by adopting a one-pot condensation reaction; in-situ self-assembly of zirconium metal clusters and bifunctional ligands is realized through a solvothermal-hot pressing synergistic process, oriented growth of MOF crystals on the surfaces of fibers and covalent interface connection formed through epoxy-carboxyl ring-opening reaction of a silane coupling agent are synchronously completed, and the MOF composite filter cloth is obtained. According to the zirconium-based MOF composite filter cloth disclosed by the invention, the efficient and high-selectivity capture of trace SOs is realized by utilizing the synergistic effect of thioether groups in ligands and unsaturated sites of metal clusters, and the regeneration is realized to a certain extent.

Description

Technical Field

[0001] This invention relates to the field of gas adsorption composite materials technology, and in particular to a zirconium-based MOF composite filter cloth, its preparation method and application. Background Technology

[0002] Sulfur dioxide (SO2) is one of the major air pollutants. Its harmful effects on the environment and human health are significant, not only contributing to acid rain and ecosystem damage but also triggering respiratory diseases. In the semiconductor integrated circuit and high-end display panel manufacturing industries, the control of trace gaseous pollutants in the wafer and glass substrate processing environment is directly related to product yield. Sulfur dioxide (SO2), as a typical acidic gaseous molecule, readily reacts chemically with metal interconnect layers, leading to corrosion of copper and aluminum wires and increased resistance. Furthermore, in the presence of humidity, it generates sulfurous acid, causing irreversible damage to the surfaces of precision optical components and sensitive devices.

[0003] Current mainstream air molecular pollutant (AMC) purification solutions generally employ chemical filtration systems, where the performance of the core adsorption material is crucial. While traditional activated carbon filter cloths possess a high specific surface area (typically exceeding 800 m² / g), their surface chemistry is non-specific, relying on physical adsorption, resulting in insufficient selectivity and adsorption strength for polar SO2 molecules. In practical use, these filter cloths commonly face the risk of desorption and secondary release, especially under conditions of temperature or airflow fluctuations, where adsorbed pollutants are easily re-released, causing secondary pollution. Furthermore, activated carbon filter cloths have limited mechanical strength, making them prone to fiber breakage during long-term high-speed operation, leading to carbon powder leakage and contamination of downstream process equipment. Metal oxide-loaded filter cloths (such as calcium oxide and zinc oxide impregnated filter media) can capture SO2 through chemical binding, but they generally suffer from low specific surface area and few effective active sites. More seriously, the sulfates generated from the reaction of metal oxides with SO2 cause filter cloth structural expansion and pore blockage, leading to a sharp increase in pressure drop, significantly shortening service life, and making it difficult to meet ppb-level purification requirements (e.g., patent CN108686629A). Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a zirconium-based MOF composite filter cloth, its preparation method and application, which can achieve efficient and highly selective capture of trace SO2 and has excellent regeneration performance.

[0005] The following is a summary of this disclosure to provide a basic understanding of some aspects. This summary is not intended to identify key or important elements, nor is it intended to limit the implementation or any aspects of the claims. Furthermore, this summary provides a simplified overview of some aspects that may be described in more detail in other parts of this disclosure.

[0006] The present invention solves the above-mentioned technical problems through the following technical means:

[0007] The first aspect of this invention provides a method for preparing a zirconium-based MOF composite filter cloth, the method being as follows:

[0008] 2-Methyl-4-(methylthio)benzoic acid and ZrOCl2·8H2O were added to N,N-dimethylformamide and stirred until completely dissolved. Glacial acetic acid was added and stirred for 30-60 min to obtain the precursor solution.

[0009] The activated and silanized pretreated nonwoven fabric is placed in a reaction vessel, and a precursor solution is added to completely immerse the nonwoven fabric. After reacting at 100–130°C for 8–24 hours, the wet nonwoven fabric is removed at 60–80°C and placed between two smooth polyimide films. It is then placed in a hot press and hot-pressed at 0.4–0.6 MPa and 90–110°C for 4–6 minutes. After naturally cooling to room temperature, it is soaked and washed with N,N-dimethylformamide to obtain a wet filter cloth. This wet filter cloth is then vacuum activated at 110–130°C for 6–8 hours to obtain a zirconium-based MOF composite filter cloth.

[0010] The second aspect of the present invention provides a zirconium-based MOF composite filter cloth, which is prepared by the preparation method described in the first aspect.

[0011] The third aspect of this invention provides the application of the zirconium-based MOF composite filter cloth described in the second aspect in SO2 adsorption filter cloth.

[0012] The method for preparing the zirconium-based MOF composite filter cloth of the present invention uses polyester nonwoven fabric as a flexible carrier, which is successively activated by alkaline solution and surface treated with epoxy silane to construct an active interface layer rich in epoxy groups. A one-pot condensation reaction is used to synthesize a bifunctional organic ligand (MTBC, methylthio-terephthalic acid) containing both carboxylic acid and thioether functional groups. Through a solvothermal-hot-press synergistic process, the in-situ self-assembly of zirconium metal clusters and bifunctional ligands is achieved under mild conditions, simultaneously completing the directional growth of MOF crystals on the fiber surface and the covalent interface connection formed by the epoxy-carboxyl ring-opening reaction through a silane coupling agent, ultimately obtaining a structurally integrated MOF composite filter cloth. The zirconium-based MOF composite filter cloth of the present invention avoids material detachment during use due to a stable chemically bonded interface, and utilizes the synergistic effect of the thioether groups in the ligands and the unsaturated sites of the metal clusters to achieve efficient and highly selective capture of trace SO2, and also achieves a certain degree of renewability.

[0013] Tests have shown that the zirconium-based MOF composite filter cloth of this invention has a high surface area and pore volume, with a specific surface area as high as 1465 m². 2 / g, with a pore volume as high as 0.80 cm³3 / g; at the same time, it exhibits high-efficiency adsorption performance for SO2, with an adsorption capacity of up to 981mg / g for SO2; it also exhibits excellent reversible regeneration performance for SO2, and still has a stable adsorption effect after 10 adsorption-desorption cycles. Attached Figure Description

[0014] Figure 1 The graph shows the dynamic adsorption curves of SO2 on the zirconium-based MOF composite filter cloths prepared in Examples 1-3.

[0015] Figure 2 This is a dynamic adsorption capacity diagram of SO2 for the zirconium-based MOF composite filter cloth prepared in Examples 1-3;

[0016] Figure 3 This is a distribution diagram of the repeated adsorption capacity of SO2 for the MOF-3 filter cloth prepared in Example 3. Detailed Implementation

[0017] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0018] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0019] The present invention discloses a method for preparing a zirconium-based MOF composite filter cloth. Using polyester nonwoven fabric as a flexible carrier, the fabric undergoes sequential alkaline activation and epoxy silane surface treatment to construct an active interface layer rich in epoxy groups. A one-pot condensation reaction is used to synthesize a bifunctional organic ligand (MTBC, methylthio-terephthalic acid) containing both carboxylic acid and thioether functional groups. Through a solvothermal-hot-press synergistic process, in-situ self-assembly of the zirconium metal cluster and the bifunctional ligand is achieved under mild conditions. Simultaneously, the directional growth of MOF crystals on the fiber surface and the covalent interface connection formed by the epoxy-carboxyl ring-opening reaction through a silane coupling agent are completed, ultimately yielding a structurally integrated MOF composite filter cloth. This filter cloth avoids material detachment during use due to a stable chemically bonded interface and utilizes the synergistic effect of the thioether groups in the ligand and the unsaturated sites of the metal cluster to achieve efficient and highly selective capture of trace SO2, while also achieving a degree of renewability.

[0020] Specifically, the preparation method of the zirconium-based MOF composite filter cloth of the present invention includes the following steps:

[0021] S1. Pretreatment of nonwoven fabrics

[0022] (1) Alkali activation: Immerse PET nonwoven fabric in 1.0-2.0 mol / L NaOH solution, stir at 70-90°C for 1-2 h, remove the nonwoven fabric and wash it repeatedly with deionized water until neutral, and vacuum dry at 50-75°C to hydrolyze the ester bonds on the PET surface to generate carboxyl and hydroxyl groups, increase the surface roughness and reactive sites, and obtain activated nonwoven fabric.

[0023] (2) Silanization treatment: The activated nonwoven fabric was immersed in a (3-glycidylpropoxy)trimethoxysilane / ethanol solution (volume ratio of (3-glycidylpropoxy)trimethoxysilane to ethanol 2:98) and reacted with shaking at room temperature for 6-18 h. The nonwoven fabric was then removed and thoroughly washed with ethanol to remove the physically adsorbed silane, and cured at 75-90°C for 1-2 h to graft epoxy functional groups onto the fiber surface, providing a reaction interface for subsequent covalent bonding with MOF, thus obtaining the silanized nonwoven fabric.

[0024] S2. Synthesis of 2-methylthioterephthalic acid (H2MTBC)

[0025] (1) Sandmeyer reaction: Under ice-water bath conditions of 0-5°C, 5.0-10.0 g of 2-methyl-4-aminobenzoic acid was dissolved in 100 mL of 10% sulfuric acid solution, stirred vigorously, and 4 mol / L NaNO2 solution was slowly added dropwise, with the temperature controlled at 0-5°C. After the addition was complete, the reaction was continued at 0-5°C for 0.5-1 h to obtain a clear diazonium salt solution. KI was weighed and dissolved in water to obtain a KI solution. The KI solution was added in batches to the diazonium salt solution, and the reaction was stirred at room temperature for 1-3 h. A large amount of solid precipitated out. The solid was then filtered, and the crude product was collected, washed three times with water, and dried under vacuum. The resulting pale yellow solid was recrystallized from a water / ethanol (volume ratio 1:1) mixed solvent to obtain white needle-like crystals, namely 2-methyl-4-iodobenzoic acid. The molar ratio of 2-methyl-4-aminobenzoic acid, NaNO2, and KI is 1:(1.1-1.3):(1.5-1.7).

[0026] (2) Sonogashira coupling: In a dry double-necked flask, 2-methyl-4-iodobenzoic acid, CuI and PdCl2(PPh3)2 were added, and the gas was evacuated three times. Anhydrous DMF and triethylamine were added through a syringe. The system was placed in an ice-water bath, and acetylene gas was slowly introduced until saturation. The ice bath was removed, and the reaction was stirred at room temperature for 6-8 h. Then, NaSCH3 was added directly to the reaction system, the temperature was raised to 55-65°C, and the reaction was continued for 3-6 h. The resulting reaction solution was poured into ice water, the pH was adjusted to 2-3 with dilute hydrochloric acid, and then extracted with ethyl acetate. The organic phases were combined, washed with saturated brine, dried with anhydrous sodium sulfate, filtered, and the solvent was removed by rotary evaporation to obtain a brownish-yellow oily crude product. The product was purified by silica gel column chromatography (eluent: petroleum ether / ethyl acetate = 5:1, v / v) to obtain a pale yellow liquid, namely methyl 2-methyl-4-((methylthio)ethynyl)benzoate. The mass ratio of 2-methyl-4-iodobenzoic acid, CuI, PdCl2(PPh3)2, and NaSCH3 is 100:(4.5-5.5):(8.5-9.5):(65.0-70.0).

[0027] (3) Methyl 2-methyl-4-((methylthio)ethynyl)benzoate was dissolved in methanol, and 3.5 mol / L KOH solution was added. The mixture was heated to reflux and stirred for 4–6 h. After the reaction was complete, most of the methanol was removed by rotary evaporation. The remaining reaction solution was carefully acidified with dilute hydrochloric acid to pH 2–3, and a large amount of white solid precipitated out. After cooling in an ice-water bath, the solid was filtered and washed thoroughly with water until the filtrate was neutral. The crude product was dissolved in hot methanol at 45–60 °C, filtered while hot, slowly cooled to room temperature, and then placed in a refrigerator to crystallize. The crystals were filtered, washed with methanol, and dried under vacuum to obtain 2-methyl-4-(methylthio)benzoic acid (H2MTBC).

[0028] S3. Hot-pressed synthesized zirconium-based MOF composite filter cloth

[0029] 2-Methyl-4-(methylthio)benzoic acid and ZrOCl2·8H2O were added to N,N-dimethylformamide and stirred until completely dissolved. Glacial acetic acid was added and stirring was continued for 30–60 min to obtain a homogeneous and clear precursor solution.

[0030] Silanized PET nonwoven fabric was placed in a high-pressure reactor, and the precursor solution was poured into the reactor to ensure that the nonwoven fabric was completely submerged. The reactor was sealed and placed in an oven at 100–130°C for 8–24 hours. After the reaction, the wet nonwoven fabric with MOF seed crystals was taken out while still hot at 60–80°C and immediately placed between two smooth polyimide films. It was then placed in a hot press and hot-pressed at 0.4–0.6 MPa and 90–110°C for 4–6 minutes. After that, it was naturally cooled to room temperature and then soaked and washed three times (1 hour each time) with DMF solvent to remove unreacted guest molecules in the pores. The resulting wet filter cloth was then vacuum activated at 110–130°C for 6–8 hours to completely remove solvent molecules in the pores, resulting in activated zirconium-based MOF composite filter cloth. The molar ratio of ZrOCl2·8H2O, 2-methyl-4-(methylthio)benzoic acid, and glacial acetic acid is 1:(1.0~1.2):(40~60).

[0031] In the specific implementation:

[0032] Example 1

[0033] The preparation method of the zirconium-based MOF composite filter cloth in this embodiment is as follows:

[0034] S1. Pretreatment of nonwoven fabrics

[0035] (1) Alkali activation: Immerse the PET nonwoven fabric in a 1.0 mol / L NaOH solution and stir at 80°C for 1 h. Then take out the nonwoven fabric and wash it repeatedly with deionized water until neutral. Dry it under vacuum at 60°C to obtain the activated nonwoven fabric.

[0036] (2) Silanization treatment: The activated nonwoven fabric was immersed in a (3-glycidylpropoxy)trimethoxysilane / ethanol solution (volume ratio of (3-glycidylpropoxy)trimethoxysilane to ethanol 2:98) and reacted with shaking at room temperature for 12 h. The nonwoven fabric was then removed and thoroughly washed with ethanol to remove the physically adsorbed silane, and then cured at 80°C for 1 h to obtain the silanized nonwoven fabric.

[0037] S2. Synthesis of 2-methylthioterephthalic acid (H2MTBC)

[0038] (1) Sandmeyer reaction: Under 0°C ice-water bath conditions, 10.0 g of 2-methyl-4-aminobenzoic acid was dissolved in 100 mL of 10% sulfuric acid solution, stirred vigorously, and 20 mL of 4 mol / L NaNO2 solution was slowly added dropwise, with the temperature controlled at 0°C. After the addition was complete, the reaction was continued at 0°C for 0.5 h to obtain a clear diazonium salt solution. 16.4 g of KI was dissolved in 50 mL of water to obtain a KI solution. The KI solution was added in portions to the diazonium salt solution, and the reaction was stirred at room temperature for 2 h. A large amount of solid precipitated out. The solid was then filtered, and the crude product was collected, washed three times with water, and dried under vacuum. The resulting pale yellow solid was recrystallized from a water / ethanol (volume ratio 1:1) mixed solvent to obtain white needle-like crystals, namely 2-methyl-4-iodobenzoic acid.

[0039] (2) Sonogashira coupling: In a dry two-necked flask, add 10.0 g of 2-methyl-4-iodobenzoic acid, 0.5 g of CuI and 0.9 g of PdCl2(PPh3)2, evacuate the gas three times, and add 150 mL of anhydrous DMF and 50 mL of triethylamine through a syringe. Place the system in an ice-water bath and slowly introduce acetylene gas until saturation. Remove the ice bath and stir the reaction at room temperature for 6 hours. Then, add 6.96 g of NaSCH3 directly to the reaction system, heat to 60°C, and continue the reaction for 4 hours. Pour the resulting reaction solution into 500 mL of ice water, adjust the pH to 3 with dilute hydrochloric acid, and then extract with ethyl acetate. Combine the organic phases, wash with saturated brine, dry with anhydrous sodium sulfate, filter, and remove the solvent by rotary evaporation to obtain a brownish-yellow oily crude product. Purify by silica gel column chromatography (eluent: petroleum ether / ethyl acetate = 5:1, v / v) to obtain a pale yellow liquid, namely methyl 2-methyl-4-((methylthio)ethynyl)benzoate.

[0040] (3) Dissolve 6.5 g of methyl 2-methyl-4-((methylthio)ethynyl)benzoate in 50 mL of methanol, add 50 mL of 3.5 mol / L KOH solution, heat to reflux, and stir for 6 h. After the reaction is complete, remove most of the methanol by rotary evaporation. Carefully acidify the remaining reaction solution with dilute hydrochloric acid to pH=3, and a large amount of white solid precipitates. After cooling in an ice-water bath, filter and wash the solid thoroughly with water until the filtrate is neutral. Dissolve the obtained crude product in hot methanol at 50 °C, filter while hot, slowly cool to room temperature, and then place in a refrigerator to crystallize. Filter, wash with methanol, and dry under vacuum to obtain 2-methyl-4-(methylthio)benzoic acid (H2MTBC).

[0041] S3. Hot-pressed synthesized zirconium-based MOF composite filter cloth

[0042] 1.31 g of 2-methyl-4-(methylthio)benzoic acid and 2.0 g of ZrOCl2·8H2O were added to 80 mL of N,N-dimethylformamide and stirred until completely dissolved. Then, 18 mL of glacial acetic acid was added and the mixture was stirred for another 30 min to obtain a homogeneous and clear precursor solution.

[0043] Silanized PET nonwoven fabric was placed in a high-pressure reactor, and the precursor solution was poured into the reactor to ensure that the nonwoven fabric was completely submerged. The reactor was sealed and placed in an oven at 120°C for 12 hours. After the reaction, the wet nonwoven fabric with MOF seed crystals was taken out while still hot at 60°C and immediately placed between two smooth polyimide films. It was then placed in a hot press and hot-pressed at 0.5 MPa and 100°C for 5 minutes. After that, it was naturally cooled to room temperature and then soaked and washed three times (1 hour each time) with DMF solvent to remove unreacted guest molecules in the pores. The resulting wet filter cloth was then vacuum activated at 120°C for 6 hours to completely remove solvent molecules in the pores, resulting in an activated zirconium-based MOF composite filter cloth, labeled MOF-1.

[0044] Example 2

[0045] In this embodiment, the amount of 2-methyl-4-(methylthio)benzoic acid in step S3 of Example 1 was replaced with 1.44g, while other steps and conditions remained unchanged. The resulting zirconium-based MOF composite filter cloth was labeled as MOF-2.

[0046] Example 3

[0047] In this embodiment, the amount of 2-methyl-4-(methylthio)benzoic acid in step S3 of Example 1 was replaced with 1.57g, while other steps and conditions remained unchanged. The resulting zirconium-based MOF composite filter cloth was labeled as MOF-3.

[0048] Example 4

[0049] The preparation method of the zirconium-based MOF composite filter cloth in this embodiment is as follows:

[0050] S1. Pretreatment of nonwoven fabrics

[0051] (1) Alkali activation: Immerse the PET nonwoven fabric in a 2.0 mol / L NaOH solution and stir at 70°C for 2 hours. Then take out the nonwoven fabric and wash it repeatedly with deionized water until neutral. Dry it under vacuum at 50°C to obtain the activated nonwoven fabric.

[0052] (2) Silanization treatment: The activated nonwoven fabric was immersed in a (3-glycidylpropoxy)trimethoxysilane / ethanol solution (volume ratio of (3-glycidylpropoxy)trimethoxysilane to ethanol 2:98) and reacted with shaking at room temperature for 6 h. The nonwoven fabric was then removed and thoroughly washed with ethanol to remove the physically adsorbed silane, and cured at 75°C for 2 h to obtain the silanized nonwoven fabric.

[0053] S2. Synthesis of 2-methylthioterephthalic acid (H2MTBC)

[0054] (1) Sandmeyer reaction: Under 3°C ice-water bath conditions, 10.0 g of 2-methyl-4-aminobenzoic acid was dissolved in 100 mL of 10% sulfuric acid solution, stirred vigorously, and 19 mL of 4 mol / L NaNO2 solution was slowly added dropwise, with the temperature controlled at 3°C. After the addition was complete, the reaction was continued at 3°C ​​for 1 h to obtain a clear diazonium salt solution. 15.5 g of KI was dissolved in 50 mL of water to obtain a KI solution. The KI solution was added in portions to the diazonium salt solution, and the reaction was stirred at room temperature for 1 h. A large amount of solid precipitated out. The solid was then filtered, and the crude product was collected, washed three times with water, and dried under vacuum. The resulting pale yellow solid was recrystallized from a water / ethanol (volume ratio 1:1) mixed solvent to obtain white needle-like crystals, namely 2-methyl-4-iodobenzoic acid.

[0055] (2) Sonogashira coupling: In a dry two-necked flask, add 10.0 g of 2-methyl-4-iodobenzoic acid, 0.45 g of CuI and 0.85 g of PdCl2(PPh3)2, evacuate the gas three times, and add 150 mL of anhydrous DMF and 50 mL of triethylamine through a syringe. Place the system in an ice-water bath and slowly introduce acetylene gas until saturation. Remove the ice bath and stir the reaction at room temperature for 7 hours. Then, add 6.50 g of NaSCH3 directly to the reaction system, heat to 55°C, and continue the reaction for 3 hours. Pour the resulting reaction solution into 500 mL of ice water, adjust the pH to 2 with dilute hydrochloric acid, and extract with ethyl acetate. Combine the organic phases, wash with saturated brine, dry with anhydrous sodium sulfate, filter, and remove the solvent by rotary evaporation to obtain a brownish-yellow oily crude product. Purify by silica gel column chromatography (eluent: petroleum ether / ethyl acetate = 5:1, v / v) to obtain a pale yellow liquid, namely methyl 2-methyl-4-((methylthio)ethynyl)benzoate.

[0056] (3) Dissolve 6.5 g of methyl 2-methyl-4-((methylthio)ethynyl)benzoate in 50 mL of methanol, add 50 mL of 3.5 mol / L KOH solution, heat to reflux, and stir for 4 h. After the reaction is complete, remove most of the methanol by rotary evaporation. Carefully acidify the remaining reaction solution with dilute hydrochloric acid to pH=2, and a large amount of white solid precipitates. After cooling in an ice-water bath, filter and wash the solid thoroughly with water until the filtrate is neutral. Dissolve the obtained crude product in hot methanol at 45 °C, filter while hot, slowly cool to room temperature, and then place in a refrigerator to crystallize. Filter, wash with methanol, and dry under vacuum to obtain 2-methyl-4-(methylthio)benzoic acid (H2MTBC).

[0057] S3. Hot-pressed synthesized zirconium-based MOF composite filter cloth

[0058] 1.44 g of 2-methyl-4-(methylthio)benzoic acid and 2.0 g of ZrOCl2·8H2O were added to 80 mL of N,N-dimethylformamide and stirred until completely dissolved. Then, 14.2 mL of glacial acetic acid was added and the mixture was stirred for another 40 min to obtain a homogeneous and clear precursor solution.

[0059] Silanized PET nonwoven fabric was placed in a high-pressure reactor, and the precursor solution was poured into the reactor to ensure that the nonwoven fabric was completely submerged. The reactor was sealed and placed in an oven at 100°C for 8 hours. After the reaction, the wet nonwoven fabric with MOF seed crystals was taken out while still hot at 70°C and immediately placed between two smooth polyimide films. It was then placed in a hot press and hot-pressed at 0.4 MPa and 90°C for 6 minutes. After that, it was naturally cooled to room temperature and then soaked and washed three times (1 hour each time) with DMF solvent to remove unreacted guest molecules in the pores. The resulting wet filter cloth was then vacuum activated at 110°C for 8 hours to completely remove solvent molecules in the pores, resulting in an activated zirconium-based MOF composite filter cloth, labeled MOF-4.

[0060] Example 5

[0061] The preparation method of the zirconium-based MOF composite filter cloth in this embodiment is as follows:

[0062] S1. Pretreatment of nonwoven fabrics

[0063] (1) Alkali activation: Immerse the PET nonwoven fabric in a 1.0 mol / L NaOH solution and stir at 90°C for 2 hours. Then take out the nonwoven fabric and wash it repeatedly with deionized water until neutral. Dry it under vacuum at 75°C to obtain the activated nonwoven fabric.

[0064] (2) Silanization treatment: The activated nonwoven fabric was immersed in a (3-glycidylpropoxy)trimethoxysilane / ethanol solution (volume ratio of (3-glycidylpropoxy)trimethoxysilane to ethanol 2:98) and reacted with shaking at room temperature for 18 h. The nonwoven fabric was then removed and thoroughly washed with ethanol to remove the physically adsorbed silane, and then cured at 90°C for 1 h to obtain the silanized nonwoven fabric.

[0065] S2. Synthesis of 2-methylthioterephthalic acid (H2MTBC)

[0066] (1) Sandmeyer reaction: Under 5°C ice-water bath conditions, 10.0 g of 2-methyl-4-aminobenzoic acid was dissolved in 100 mL of 10% sulfuric acid solution, stirred vigorously, and 21 mL of 4 mol / L NaNO2 solution was slowly added dropwise, with the temperature controlled at 5°C. After the addition was complete, the reaction was continued at 5°C for 1 h to obtain a clear diazonium salt solution. 17.0 g of KI was dissolved in 50 mL of water to obtain a KI solution. The KI solution was added in portions to the diazonium salt solution, and the reaction was stirred at room temperature for 3 h. A large amount of solid precipitated out. The solid was then filtered, and the crude product was collected, washed three times with water, and dried under vacuum. The resulting pale yellow solid was recrystallized from a water / ethanol (volume ratio 1:1) mixed solvent to obtain white needle-like crystals, namely 2-methyl-4-iodobenzoic acid.

[0067] (2) Sonogashira coupling: In a dry two-necked flask, add 10.0 g of 2-methyl-4-iodobenzoic acid, 0.55 g of CuI and 0.95 g of PdCl2(PPh3)2, evacuate the gas three times, and add 150 mL of anhydrous DMF and 50 mL of triethylamine through a syringe. Place the system in an ice-water bath and slowly introduce acetylene gas until saturation. Remove the ice bath and stir the reaction at room temperature for 8 hours. Then, add 7.0 g of NaSCH3 directly to the reaction system, heat to 65°C, and continue the reaction for 6 hours. Pour the resulting reaction solution into 500 mL of ice water, adjust the pH to 3 with dilute hydrochloric acid, and extract with ethyl acetate. Combine the organic phases, wash with saturated brine, dry with anhydrous sodium sulfate, filter, and remove the solvent by rotary evaporation to obtain a brownish-yellow oily crude product. Purify by silica gel column chromatography (eluent: petroleum ether / ethyl acetate = 5:1, v / v) to obtain a pale yellow liquid, namely methyl 2-methyl-4-((methylthio)ethynyl)benzoate.

[0068] (3) Dissolve 6.5 g of methyl 2-methyl-4-((methylthio)ethynyl)benzoate in 50 mL of methanol, add 50 mL of 3.5 mol / L KOH solution, heat to reflux, and stir for 5 h. After the reaction is complete, remove most of the methanol by rotary evaporation. Carefully acidify the remaining reaction solution with dilute hydrochloric acid to pH=3, and a large amount of white solid precipitates. After cooling in an ice-water bath, filter and wash the solid thoroughly with water until the filtrate is neutral. Dissolve the obtained crude product in hot methanol at 60 °C, filter while hot, slowly cool to room temperature, and then place in a refrigerator to crystallize. Filter, wash with methanol, and dry under vacuum to obtain 2-methyl-4-(methylthio)benzoic acid (H2MTBC).

[0069] S3. Hot-pressed synthesized zirconium-based MOF composite filter cloth

[0070] 14.4 g of 2-methyl-4-(methylthio)benzoic acid and 2.0 g of ZrOCl2·8H2O were added to 80 mL of N,N-dimethylformamide and stirred until completely dissolved. Then, 21.2 mL of glacial acetic acid was added and the mixture was stirred for another 60 min to obtain a homogeneous and clear precursor solution.

[0071] Silanized PET nonwoven fabric was placed in a high-pressure reactor, and the precursor solution was poured into the reactor to ensure that the nonwoven fabric was completely submerged. The reactor was sealed and placed in an oven at 130°C for 24 hours. After the reaction was completed, the wet nonwoven fabric with MOF seed crystals was taken out while still hot at 80°C and immediately placed between two smooth polyimide films. It was then placed in a hot press and hot-pressed at 0.6 MPa and 110°C for 4 minutes. After that, it was naturally cooled to room temperature and then soaked and washed three times (1 hour each time) with DMF solvent to remove unreacted guest molecules in the pores. The resulting wet filter cloth was then vacuum activated at 130°C for 6 hours to completely remove solvent molecules in the pores, resulting in an activated zirconium-based MOF composite filter cloth, labeled MOF-5.

[0072] Structural characterization and performance testing:

[0073] (1) Specific surface area and pore size test analysis

[0074] Using the zirconium-based MOF composite filter cloths prepared in Examples 1-5 as samples, the BET surface area and pore structure of the materials were tested using a Belserp MAX II analyzer at -195°C using N2 adsorption and desorption. The total surface area was determined using the Brunol-Emmett-Taylor (BET) equation. The results are shown in Table 1.

[0075] Table 1. Specific surface area and pore volume of the samples

[0076] sample <![CDATA[BET(m 2 / g)]]> <![CDATA[Pore volume (cm 3 / g)]]> Example 1 (MOF-1) 1232 0.61 Example 2 (MOF-2) 1377 0.72 Example 3 (MOF-3) 1465 0.80 Example 4 (MOF-4) 1350 0.69 Example 5 (MOF-5) 1383 0.74

[0077] The data in Table 1 show that the zirconium-based MOF composite filter cloth prepared in this invention has a high surface area and pore volume.

[0078] (2) Dynamic adsorption performance test

[0079] Using the zirconium-based MOF composite filter cloths prepared in Examples 1-3 as samples, SO2 adsorption tests were conducted on the materials using a UTEST static adsorption apparatus. Initial efficiency: test airflow (12 L / min), test resistance (100 Pa), and test concentration (10000 ppb) were controlled; dirt holding capacity: test airflow (15 L / min), test resistance (100 Pa), and test concentration (10 ppm) were controlled. The adsorption capacity was calculated by integrating the breakthrough curve, using the following formula:

[0080]

[0081] In the formula, q (g / g) is the maximum adsorption capacity, F (mL / min) is the total gas flow rate, and C0 and C (mg / m³) are also present. 3 ) represent the inlet and outlet concentrations of SO2, respectively; m(g) represents the weight of the adsorbent; t represents the total concentration of SO2. s (min) represents the adsorption time. The dynamic adsorption curves of SO2 on the zirconium-based MOF composite filter cloths prepared in Examples 1-3 are shown below. Figure 1 As shown, the dynamic adsorption capacity diagram of SO2 for the zirconium-based MOF composite filter cloths prepared in Examples 1-3 is as follows. Figure 2 As shown.

[0082] Combination Figure 1 and Figure 2 It can be seen that the zirconium-based MOF composite filter cloth of the present invention exhibits high adsorption performance for SO2. The SO2 adsorption breakthrough time of the three groups of samples in Examples 1, 2 and 3 is successively delayed, and the adsorption capacity for SO2 reaches 353 mg / g, 776 mg / g and 981 mg / g, respectively.

[0083] (3) Reversible adsorption performance test

[0084] MOF-3 filter cloth saturated with SO2 adsorption was purged in circulating hot nitrogen (purity ≥99.99%) at 80°C for 60 minutes. The heat provided energy to disrupt the interaction between SO2 and the adsorption sites. The flowing nitrogen promptly carried the desorbed SO2 molecules away from the filter cloth, preventing re-adsorption. The dynamic adsorption performance of the desorbed filter cloth was then repeated. The resulting repeat adsorption capacity distribution of SO2 on the MOF-3 filter cloth is shown in the figure below. Figure 3 As shown.

[0085] Figure 3The data show that the zirconium-based MOF composite filter cloth of the present invention exhibits excellent reversible performance for SO2. MOF-3 adsorbs SO2 and desorbs it multiple times, and still has a stable adsorption effect after 10 repetitions.

[0086] In summary, the zirconium-based MOF composite filter cloth of the present invention exhibits high adsorption performance for SO2 and excellent reversible cycling performance. Therefore, the zirconium-based MOF composite filter cloth of the present invention can be used in SO2 adsorption filter cloths.

[0087] The foregoing description includes examples from this specification. Of course, for the purposes of describing this specification, it is impossible to describe every conceivable combination of components or methods; however, those skilled in the art will understand that many other combinations and arrangements are possible. Therefore, this specification is intended to cover all such changes, modifications, and variations that fall within the spirit and scope of the appended claims. Furthermore, with regard to the use of the term "comprising" in the detailed description or claims, the term is intended to be inclusive in a manner similar to the term "including," as interpreted when "comprising" is used as a transitional word in the claims.

[0088] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a zirconium-based MOF composite filter cloth, characterized in that, The preparation method is as follows: 2-Methyl-4-(methylthio)benzoic acid and ZrOCl2·8H2O were added to N,N-dimethylformamide and stirred until completely dissolved. Glacial acetic acid was added and stirred for 30-60 min to obtain the precursor solution. The activated and silanized pretreated nonwoven fabric is placed in a reaction vessel, and a precursor solution is added to completely immerse the nonwoven fabric. After reacting at 100–130°C for 8–24 hours, the wet nonwoven fabric is removed at 60–80°C and placed between two smooth polyimide films. It is then placed in a hot press and hot-pressed at 0.4–0.6 MPa and 90–110°C for 4–6 minutes. After naturally cooling to room temperature, it is soaked and washed with N,N-dimethylformamide to obtain a wet filter cloth. This wet filter cloth is then vacuum activated at 110–130°C for 6–8 hours to obtain a zirconium-based MOF composite filter cloth.

2. The method for preparing zirconium-based MOF composite filter cloth according to claim 1, wherein, The molar ratio of ZrOCl2·8H2O, 2-methyl-4-(methylthio)benzoic acid, and glacial acetic acid is 1:(1.0-1.2):(40-60).

3. The method for preparing zirconium-based MOF composite filter cloth according to claim 1, wherein, The pretreatment of the nonwoven fabric is as follows: The nonwoven fabric is immersed in NaOH solution and stirred at a constant temperature of 70-90°C for 1-2 hours. After that, the nonwoven fabric is taken out and washed repeatedly with deionized water until neutral. It is then dried under vacuum at 50-75°C to obtain the activated nonwoven fabric. The activated nonwoven fabric is immersed in an ethanol solution containing (3-glycidylpropoxy)trimethoxysilane and reacted with shaking at room temperature for 6–18 h. The nonwoven fabric is then removed, thoroughly washed with ethanol, and cured at 75–90°C for 1–2 h to obtain a silanized nonwoven fabric.

4. The method for preparing zirconium-based MOF composite filter cloth according to claim 3, wherein, The concentration of the NaOH solution is 1.0–2.0 mol / L; and / or, The volume concentration of (3-glycidylpropoxy)trimethoxysilane in the ethanol solution containing (3-glycidylpropoxy)trimethoxysilane is 2%.

5. The method for preparing zirconium-based MOF composite filter cloth according to claim 1, wherein, The preparation method of the 2-methyl-4-(methylthio)benzoic acid is as follows: 2-Methyl-4-((methylthio)ethynyl)benzoate was weighed and dissolved in methanol. 3.5 mol / L KOH solution was added, and the mixture was heated to reflux and stirred for 4–6 h. After the reaction was complete, the mixture was rotary evaporated. The remaining reaction solution was acidified with dilute hydrochloric acid to pH 2–3, precipitating a solid. The solid was cooled in an ice-water bath and then filtered. The solid was washed until the filtrate was neutral. The crude product was dissolved in methanol at 45–60 °C, filtered while hot, cooled to room temperature, and then placed in a refrigerator to crystallize. The crystals were filtered, washed with methanol, and dried under vacuum to obtain 2-methyl-4-(methylthio)benzoic acid.

6. The method for preparing zirconium-based MOF composite filter cloth according to claim 5, wherein, The preparation method of the methyl 2-methyl-4-((methylthio)ethynyl)benzoate is as follows: In a container, 2-methyl-4-iodobenzoic acid, CuI, and PdCl2(PPh3)2 were mixed, followed by the addition of N,N-dimethylformamide and triethylamine. The mixture was placed in an ice-water bath, and acetylene gas was introduced until saturation. The mixture was stirred at room temperature for 6–8 hours. Subsequently, NaSCH3 was added, and the temperature was raised to 55–65°C. The reaction was continued for 3–6 hours. The resulting reaction solution was poured into ice water, and the pH was adjusted to 2–3 with dilute hydrochloric acid. The solution was then extracted with ethyl acetate. The organic phases were combined, washed with saturated brine, dried over anhydrous sodium sulfate, filtered, and the solvent was removed by rotary evaporation. The solution was then purified by silica gel column chromatography to obtain methyl 2-methyl-4-((methylthio)ethynyl)benzoate.

7. The method for preparing zirconium-based MOF composite filter cloth according to claim 6, wherein, The mass ratio of 2-methyl-4-iodobenzoic acid, CuI, PdCl2(PPh3)2, and NaSCH3 is 100:(4.5-5.5):(8.5-9.5):(65.0-70.0).

8. The method for preparing zirconium-based MOF composite filter cloth according to claim 6, wherein, The preparation method of the 2-methyl-4-iodobenzoic acid is as follows: Under ice-water bath conditions, 2-methyl-4-aminobenzoic acid was added to a 10 wt% sulfuric acid solution and stirred to dissolve. 4 mol / L NaNO₂ solution was then added dropwise while maintaining the temperature at 0–5°C. After the addition was complete, the reaction was continued at 0–5°C for 0.5–1 h to obtain a diazonium salt solution. KI aqueous solution was added to the diazonium salt solution, and the reaction was stirred at room temperature for 1–3 h. The mixture was filtered, the crude solid product was collected, washed, and dried to obtain 2-methyl-4-iodobenzoic acid. The molar ratio of 2-methyl-4-aminobenzoic acid, NaNO2, and KI is 1:(1.1-1.3):(1.5-1.7).

9. The zirconium-based MOF composite filter cloth prepared by the preparation method according to any one of claims 1-8.

10. The application of the zirconium-based MOF composite filter cloth according to claim 9 in SO2 adsorption filter cloth.

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