Covalent organic framework in-situ cross-linked crystalline state ultra-membrane for deeply purifying PM and SO2 and preparation method of covalent organic framework in-situ cross-linked crystalline state ultra-membrane

Abstract

The invention provides a covalent organic framework in-situ cross-linked crystalline state ultra-membrane for deep purification of PM and SO2 and a preparation method thereof, the method comprises the following steps: step S1, reacting a carbon nanotube with a coupling agent in an organic reagent to prepare an aminated carbon nanotube; s2, dispersing the aminated carbon nanotube obtained in the step S1, an aldehyde ligand, an amino ligand and a catalyst in a reaction solvent, and preparing a covalent organic framework composite material by using a microwave-assisted method; and step S3, cleaning, purifying and processing the composite material obtained in the step S2 to prepare the covalent organic framework in-situ cross-linked crystalline state super-membrane for deeply purifying PM and SO2. The prepared crystalline state super-membrane has the remarkable advantages of being excellent in pore property, unique in core-shell structure, high in dust interception efficiency, good in sulfur dioxide adsorption capacity and the like, has the characteristics of rapidness and low energy consumption, is simple in preparation process and mild in condition, and is a dust and toxic gas purification membrane material with excellent performance.

Description

Technical Field

[0001] The present invention relates to the technical field of dust and toxic gas purification membrane materials, and in particular to a method for deeply purifying PM and SO 2 Covalent organic framework in-situ cross-linked crystalline supermembrane and preparation method thereof. Background Art

[0002] Sulfur dioxide (SO 2 ) is a corrosive, colorless, non-flammable gas with a pungent odor, which is listed by the World Health Organization as a chemical substance that is highly toxic to humans. 2 It is easily absorbed by the skin and respiratory system. Exposure to more than 100 ppm SO 2 Even at concentrations below 100 ppm, SO 2 It can also cause bronchoconstriction and impair lung function. For example, exposure to 1.5 ppm SO 2 A few minutes will cause temporary breathing difficulties. 2 When the concentration is higher than 1.5 ppm, healthy people may suffer from chronic bronchitis, pharyngitis and severe respiratory infections. Therefore, air quality guidelines recommend that human exposure to SO 2 The concentration limit is 500 micrograms (175 ppb) for 10 minutes and 20 micrograms (8 ppb) for a daily average.

[0003] At the same time, SO 2 It is also the precursor of particulate matter (PM), which is also extremely harmful to the human body. 2 It is highly soluble in water, forming sulfurous acid, which can be further oxidized into sulfuric acid, which is the main cause of acid rain. Acid rain damages the aquatic environment and hinders the growth of forests and crops. In urban areas, acid rain accelerates metal corrosion and deteriorates materials such as limestone, marble and plaster. Therefore, at this stage, it is necessary not only to reduce SO 2 Emissions or increases in SO 2 Capture to improve air quality and reduce the PM and SO 2 The simultaneous in-depth treatment of the airflow environment under the presence of SO is essential to avoid serious health effects on people working in various urban environments. 2 The adsorption capture technology currently used to capture SO is mainly focused on improving the adsorption capacity of toxic gases through measures such as upgrading the scrubber (based on alkaline aqueous solution and wet sulfuric acid process). However, its disadvantages are obvious, including the generation of large amounts of wastewater, pipeline corrosion, and high operating and recovery costs. 2Solid materials such as metal oxides and zeolites have problems such as high activation temperature (above 250 °C) and reduced porosity after multiple cycles. Therefore, there is an urgent need to develop purification materials that can efficiently intercept harmful PM and have good SO 2 adsorption capacity and chemical stability.

[0004] Porous materials, especially metal-organic frameworks (MOFs), have attracted much attention in SO 2 capture and PM interception due to their high porosity. Existing research results show that even under humid conditions, the capture effect of MOFs on SO 2 is very significant. However, most MOFs have relatively poor chemical stability against SO 2 / water and cannot meet the requirements of long-term stable capture and continuous recycling. In contrast, covalent organic frameworks (COFs) are a class of emerging porous materials synthesized by covalently connecting ligands containing light elements (such as carbon, hydrogen, oxygen, nitrogen, and boron) through reticular chemistry. Their inherent stability stems from the nature of covalent bonds, making their structures more rigid, thus improving thermal stability and chemical stability and enabling them to adapt to various harsh and complex environments. In addition to high stability, the functional diversity and structural tunability of COFs have important applications in many fields, including gas storage and separation, heterogeneous catalysis, drug delivery, and electronic devices. Summary of the Invention

[0005] The purpose of the present invention is to prepare a covalently organic framework in-situ cross-linked crystalline ultrafilm for deep purification of PM and SO 2 to meet the demand for synchronous deep treatment of PM and SO 2 in complex environments.

[0006] To achieve the above purpose, the present invention provides a covalently organic framework in-situ cross-linked crystalline ultrafilm for deep purification of PM and SO 2 and its preparation method. Specifically, an amino-functional group is grafted onto the surface of carbon nanotubes by the silane coupling agent method to prepare amino-functionalized carbon nanotubes, which are then fully dispersed with amine ligands, aldehyde ligands, and a catalyst in a reaction solvent. The covalent organic framework is coated on the surface of the carbon nanotubes by microwave assistance to prepare a covalent organic framework composite material. Further, through cleaning, purification, and processing and forming techniques, a covalently organic framework in-situ cross-linked crystalline ultrafilm for deep purification of PM and SO 2 with excellent pore properties is prepared (the ultrafilm is a film with high crystallinity and nanoscale thickness).

[0007] According to the first aspect of the present invention, a covalently organic framework in-situ cross-linked crystalline ultrafilm for deep purification of PM and SO 2Preparation method of covalently organic framework in-situ cross-linked crystalline ultrafilm, comprising the following steps: Step S1, dispersing carbon nanotubes and a coupling agent in an organic reagent for mixing to obtain a mixed solution, adjusting the pH value of the mixed solution through a pH regulator, and then using the silane coupling agent method to prepare amino-functionalized carbon nanotubes; Step S2, dispersing the amino-functionalized carbon nanotubes obtained in Step S1, an aldehyde ligand, an amine ligand and a catalyst in a reaction solvent, and using microwave-assisted method to prepare a covalently organic framework composite material; Step S3, cleaning and purifying the covalently organic framework composite material obtained in Step S2, and preparing a deep purification PM and SO through a processing and forming technology 2 Covalently organic framework in-situ cross-linked crystalline ultrafilm

[0008] Preferably, in Step S1, the carbon nanotubes are one or more of single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes, the coupling agent is one or more of methyltriethoxysilane, vinyltriethoxysilane, isopropenyltriethoxysilane, γ-aminopropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-glycidylethoxypropyltrimethoxysilane, and the mass ratio of the carbon nanotubes to the coupling agent is 2:1 to 1:2

[0009] Preferably, in Step S1, the organic reagent is one or more of methanol, ethanol, isopropanol, toluene, dichloromethane, chloroform, tetrahydrofuran, dioxane, acetone, and the mass ratio of the carbon nanotubes to the organic reagent is 1:5 to 1:15

[0010] Preferably, in Step S1, the pH regulator is one or more of acetic acid, hydrochloric acid, sulfuric acid, and the pH value range of the mixed solution obtained after adjustment is 3 to 6

[0011] Preferably, in Step S1, the reaction conditions of the silane coupling agent method are that the reaction temperature is 60 to 90 °C and the reaction time is 6 to 12 h

[0012] Preferably, in Step S2, the aldehyde ligand is one or more of pyromellitic dianhydride, 1,2,4,5-benzenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, terephthalaldehyde, 1,3,5-benzenetricarboxaldehyde, 4,4'-biphenyldicarboxaldehyde, the amine ligand is one or more of tris(4-aminophenyl)methane, tetrakis(4-aminophenyl)methane, 4-aminophenyltrimethylsilane, N-aryldiphenylketimine, ethylenediamine, and the molar ratio of the functional groups of the amine ligand to the aldehyde ligand is 2:1 to 1:2

[0013] Preferably, in step S2, the reaction solvent is one or more of m-cresol, acetonitrile, deionized water, n-butanol, N,N-dimethylformamide, and dimethyl sulfoxide, and the catalyst is one or more of isoquinoline, acetic acid, p-toluenesulfonic acid, metal trifluoromethanesulfonate, and piperidine. The volume ratio of the catalyst to the reaction solvent is 1:5 to 1:20.

[0014] Preferably, in step S2, the reaction temperature for microwave-assisted synthesis is 60 to 150 °C, the reaction time is 0.5 to 6 h, and the microwave power is 250 to 500 W.

[0015] Preferably, in step S3, the processing and forming technology is one or more of vacuum filtration, coating, solution casting, and layer-by-layer self-assembly.

[0016] Preferably, in step S3, the processing and forming method is vacuum filtration, the vacuum degree is -0.05 to -0.09 MPa, the pressure holding time is 1 to 30 min, and the filtration rate is 1 to 10 mL / min.

[0017] Preferably, in step S3, the processing and forming method is coating, the substrate roughness is 1 to 10 μm, the substrate size is 10 to 100 cm 2 , and the coating speed is 1 to 10 mm / s. The slurry solvent is one or more of toluene, chloroform, and N,N-dimethylformamide.

[0018] Preferably, in step S3, the processing and forming method is solution casting, the solute mass fraction is 10 to 40%, the mold size is 25 to 100 cm 2 , and the casting speed is 1 to 10 mL / min. The casting temperature is 20 to 60 °C.

[0019] Preferably, in step S3, the processing and forming method is layer-by-layer self-assembly. The solution of the soluble polyelectrolyte is a mixture of one or more of N,N-dimethylformamide, dimethyl sulfoxide, and buffer solution and water. The volume ratio of water to the organic solvent is 1:1 to 3:1, the pH value is 3 to 9, and the adsorption time for each layer is 5 to 30 min.

[0020] To achieve the above object, according to the second aspect of the present invention, the present invention also provides a covalent organic framework in-situ cross-linked crystalline ultrafilm obtained by the foregoing preparation method.

[0021] Preferably, the obtained covalent organic framework in-situ cross-linked crystalline ultrafilm has a high specific surface area (612 m 2 / g - 787 m 2 / g), small pore size (1.09 nm - 1.55 nm), and high efficient dust interception efficiency (PM 0.3-2.5≥97.4%) and good adsorption capacity for toxic gases (SO 2 The adsorption capacity is higher than 5.4 mmol / g).

[0022] The beneficial effects of the present invention are as follows: (1) The surface of carbon nanotubes is aminated to promote the in-situ crosslinking of covalent organic frameworks on the surface of carbon nanotubes, forming a unique core-shell microstructure; (2) While retaining the three-dimensional network structure of carbon nanotubes, covalent organic frameworks with a large specific surface area and rich microporous structures are introduced. This crystalline ultrafilm has both good gas permeability and adsorption capacity for dust and toxic gases; (3) Microwave-assisted synthesis is used to prepare the composite material, making the growth of covalent organic frameworks more uniform and continuous, while reducing the reaction time and energy consumption; (4) Through the optimization of the synthesis process, the prepared crystalline ultrafilm not only has excellent pore properties, a unique core-shell structure, high dust interception efficiency and good SO 2 adsorption capacity and other significant advantages, but also has the characteristics of fast speed and low energy consumption. The preparation process is simple and the conditions are mild. It is an excellent dust and toxic gas purification membrane material.

[0023] The technical solution proposed by the present invention enables the covalent organic framework in-situ crosslinked crystalline ultrafilm to have a high specific surface area, small pore size, high dust interception efficiency and good SO 2 adsorption capacity. The design of this material aims to meet the requirements for the synchronous in-depth treatment of PM and SO in complex environments 2 and has broad application potential and market prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0025] Figure 1 It is a scanning electron microscope image of the covalent organic framework in-situ crosslinked crystalline ultrafilm in Example 1.

[0026] Figure 2 It is a transmission electron microscope image of the covalent organic framework in-situ crosslinked crystalline ultrafilm in Example 1.

[0027] Figure 3 It is a scanning electron microscope image of the covalent organic framework in-situ crosslinked crystalline ultrafilm in Example 2.

[0028] Figure 4 It is a transmission electron microscope image of the covalent organic framework in-situ crosslinked crystalline ultrafilm in Example 2.

[0029] Figure 5 It is a scanning electron microscope image of the covalently organic framework in-situ crosslinked crystalline ultrafilm in Example 3.

[0030] Figure 6 It is a transmission electron microscope image of the covalently organic framework in-situ crosslinked crystalline ultrafilm in Example 3.

[0031] Figure 7 It is a scanning electron microscope image of the covalently organic framework in-situ crosslinked crystalline ultrafilm in Example 4.

[0032] Figure 8 It is a transmission electron microscope image of the covalently organic framework in-situ crosslinked crystalline ultrafilm in Example 4.

[0033] Figure 9 It is a schematic diagram of the method flow of the present invention. Detailed implementation manners

[0034] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be described in detail below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other implementation manners obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope protected by the present invention. The present invention will be described in detail below with reference to the embodiments.

[0035] As Figure 9 shown, Embodiment 1 of the present invention provides a method for preparing a covalently organic framework in-situ crosslinked crystalline ultrafilm, including the following steps: Step S11, preparing amino-functionalized carbon nanotubes: dissolving single-walled carbon nanotubes and methyltriethoxysilane (the mass ratio of carbon nanotubes to methyltriethoxysilane is 1:1) in toluene (the mass ratio of carbon nanotubes to toluene is 1:10), adjusting the pH value to 5 with acetic acid, and reacting at 80 °C for 8 hours using the silane coupling agent method to prepare amino-functionalized carbon nanotubes; Step S12, preparing a covalently organic framework composite material: dispersing the amino-functionalized carbon nanotubes obtained in Step S11, 1,3,5-tris(4-aminophenyl)benzene, pyromellitic dianhydride (the molar ratio of functional groups is 1:1), and isoquinoline in m-cresol (the volume ratio of isoquinoline to m-cresol is 1:10), and using microwave-assisted synthesis (the reaction temperature is 120 °C, the reaction time is 3 hours, and the microwave power is 400 W) to prepare a covalently organic framework composite material; Step S13, preparing a covalently organic framework in-situ crosslinked crystalline ultrafilm: preparing a covalently organic framework in-situ crosslinked crystalline ultrafilm with excellent pore properties through washing, purification, and vacuum filtration (the vacuum degree is -0.07 MPa, the pressure holding time is 5 minutes, and the filtration rate is 3 mL / min), with a specific surface area of 787 m 2 / g and an average pore diameter of 1.09 nm.

[0036] As shown Figure 1 in the figure, the scanning electron microscope image of the covalently organic framework in-situ cross-linked crystalline ultrafilm obtained in Example 1 of the present invention shows that the material is a three-dimensional woven structure in which the covalently organic framework uniformly coats the surface of the carbon nanotubes.

[0037] As shown Figure 2 in the figure, the transmission electron microscope image of the covalently organic framework in-situ cross-linked crystalline ultrafilm obtained in Example 1 of the present invention shows that a thin layer of two-dimensional covalently organic framework is in-situ cross-linked on the surface of the carbon nanotubes.

[0038] Example 2 of the present invention provides a method for preparing a covalently organic framework in-situ cross-linked crystalline ultrafilm, which includes the following steps: Step S21, preparing amino-functionalized carbon nanotubes: Dissolve double-walled carbon nanotubes and vinyltriethoxysilane (the mass ratio of carbon nanotubes to vinyltriethoxysilane is 1:2) in dichloromethane (the mass ratio of carbon nanotubes to dichloromethane is 1:15), adjust the pH value to 4 with acetic acid, and react at 90 °C for 6 hours using the silane coupling agent method to prepare amino-functionalized carbon nanotubes; Step S22, preparing a covalently organic framework composite material: Disperse the amino-functionalized carbon nanotubes obtained in Step S21, 4,4'-aminophenylmethane, terephthalaldehyde (the molar ratio of functional groups is 1:2), and acetic acid in acetonitrile (the volume ratio of acetic acid to acetonitrile is 1:20), and use microwave-assisted synthesis (the reaction temperature is 150 °C, the reaction time is 1 hour, and the microwave power is 500 W) to prepare a covalently organic framework composite material; Step S23, preparing a covalently organic framework in-situ cross-linked crystalline ultrafilm: Clean and purify the composite material obtained in S22 and use the coating method (the substrate roughness is 1 μm, the substrate size is 50 cm 2 , the coating speed is 5 mm / s, and the slurry solvent is N,N-dimethylformamide) to prepare a covalently organic framework in-situ cross-linked crystalline ultrafilm with excellent pore properties, with a specific surface area of 733 m 2 / g and an average pore diameter of 1.23 nm.

[0039] As shown Figure 3 in the figure, the scanning electron microscope image of the covalently organic framework in-situ cross-linked crystalline ultrafilm obtained in Example 2 of the present invention shows that the material is a three-dimensional woven structure in which the covalently organic framework uniformly coats the surface of the carbon nanotubes.

[0040] As shown Figure 4 in the figure, the transmission electron microscope image of the covalently organic framework in-situ cross-linked crystalline ultrafilm obtained in Example 2 of the present invention shows that a thin layer of two-dimensional covalently organic framework is in-situ cross-linked on the surface of the carbon nanotubes.

[0041] Example 3 of the present invention provides a method for preparing a covalently organic framework in-situ cross-linked crystalline ultrafilm, including the following steps: Step S31, preparing amino-functionalized carbon nanotubes: Dissolve multi-walled carbon nanotubes and isopropenyltriethoxysilane (the mass ratio of carbon nanotubes to isopropenyltriethoxysilane is 2:1) in tetrahydrofuran (the mass ratio of carbon nanotubes to tetrahydrofuran is 1:5), adjust the pH value to 3 with acetic acid, and react at 60 °C for 12 hours using the silane coupling agent method to prepare amino-functionalized carbon nanotubes; Step S32, preparing a covalently organic framework composite material: Disperse the amino-functionalized carbon nanotubes obtained in Step S31, 4-aminophenyltrimethylsilane, 1,2,4,5-benzenetetracarboxylic dianhydride (the molar ratio of functional groups is 2:1), and p-toluenesulfonic acid in N,N-dimethylformamide (the volume ratio of p-toluenesulfonic acid to N,N-dimethylformamide is 1:5), and use microwave-assisted synthesis (the reaction temperature is 100 °C, the reaction time is 4 hours, and the microwave power is 300 W) to prepare a covalently organic framework composite material; Step S33, preparing a covalently organic framework in-situ cross-linked crystalline ultrafilm: Pass the composite material obtained in S32 through cleaning and purification and the solution casting method (the solute mass fraction is 20%, the mold size is 100 cm 2 , the casting speed is 3 mL / min, and the casting temperature is 40 °C) to prepare a covalently organic framework in-situ cross-linked crystalline ultrafilm with excellent pore properties, having a specific surface area of 681 m 2 / g and an average pore diameter of 1.37 nm.

[0042] As Figure 5 shown, the scanning electron microscopy image of the covalently organic framework in-situ cross-linked crystalline ultrafilm obtained in Example 3 of the present invention shows that the material is a three-dimensional woven structure with the covalently organic framework uniformly wrapped on the surface of the carbon nanotubes.

[0043] As Figure 6 shown, the transmission electron microscopy image of the covalently organic framework in-situ cross-linked crystalline ultrafilm obtained in Example 3 of the present invention shows that a thin layer of two-dimensional covalently organic framework is in-situ cross-linked on the surface of the carbon nanotubes.

[0044] Example 4 of the present invention provides a method for preparing a covalently organic framework in-situ crosslinked crystalline ultrafilm, comprising the following steps: Step S41, preparing amino-functionalized carbon nanotubes: Dissolve single-walled carbon nanotubes and γ-methacryloxypropyltrimethoxysilane (the mass ratio of carbon nanotubes to γ-methacryloxypropyltrimethoxysilane is 3:2) in acetone (the mass ratio of carbon nanotubes to acetone is 1:12), adjust the pH value to 4.5 with acetic acid, and react at a temperature of 70 °C for 10 hours using the silane coupling agent method to prepare amino-functionalized carbon nanotubes; Step S42, preparing a covalently organic framework composite material: Disperse the amino-functionalized carbon nanotubes obtained in Step S41, ethylenediamine, 4,4'-biphenyldialdehyde (the molar ratio of functional groups is 3:2), and piperidine in dimethyl sulfoxide (the volume ratio of piperidine to dimethyl sulfoxide is 1:15), and use microwave-assisted synthesis (the reaction temperature is 80 °C, the reaction time is 5 hours, and the microwave power is 300 W) to prepare a covalently organic framework composite material; Step S43, preparing a covalently organic framework in-situ crosslinked crystalline ultrafilm: Pass the composite material obtained in S42 through cleaning and purification and the layer-by-layer self-assembly method (the solution of the soluble polyelectrolyte is a mixture of N,N-dimethylformamide and water with a volume ratio of 2:1 and a pH value of 6, and the adsorption time for each layer is 5 minutes) to prepare a covalently organic framework in-situ crosslinked crystalline ultrafilm with excellent pore properties, having a specific surface area of 612 m 2 / g and an average pore diameter of 1.55 nm.

[0045] As Figure 7 shown, the scanning electron microscope image of the covalently organic framework in-situ crosslinked crystalline ultrafilm obtained in Example 4 of the present invention shows that the material is a three-dimensional woven structure in which the covalently organic framework uniformly coats the surface of the carbon nanotubes.

[0046] As Figure 8 shown, the transmission electron microscope image of the covalently organic framework in-situ crosslinked crystalline ultrafilm obtained in Example 4 of the present invention shows that a thin layer of two-dimensional covalently organic framework is in-situ crosslinked on the surface of the carbon nanotubes.

[0047] Comparative Example 1 of the present invention provides a method for preparing a covalently organic framework in-situ crosslinked crystalline ultrafilm, which basically uses the method of Example 1 to prepare a fast and low-energy-consuming covalently organic framework material. The difference is that in this example, carbon nanotubes are not used as a flexible substrate template to synthesize the covalently organic framework material. Specifically, tris(4-aminophenyl)methane, pyromellitic dianhydride (functional group molar ratio of 1:1), and isoquinoline are dispersed in m-cresol (isoquinoline to m-cresol volume ratio of 1:10), and microwave-assisted synthesis is used (reaction temperature is 120 °C, reaction time is 3 hours, microwave power is 400 W) to prepare a covalently organic framework composite material; the obtained composite material is prepared into a covalently organic framework material with excellent pore properties through washing, purification, and vacuum filtration (vacuum degree is -0.07 MPa, pressure holding time is 5 minutes, filtration speed is 3 mL / min), and the specific surface area is 248 m 2 / g, and the average pore diameter is 2.21 nm.

[0048] Comparative Example 2 of the present invention provides a method for preparing a covalently organic framework in-situ crosslinked crystalline ultrafilm, which basically uses the method of Example 2 to prepare a fast and low-energy-consuming covalently organic framework crystalline ultrafilm. The difference is that in this example, unaminated carbon nanotubes are used to prepare the covalently organic framework composite membrane. Specifically, double-walled carbon nanotubes, tetrakis(4-aminophenyl)methane, terephthalaldehyde (functional group molar ratio of 1:2), and acetic acid are dispersed in acetonitrile (acetic acid to acetonitrile volume ratio of 1:20), and microwave-assisted synthesis is used (reaction temperature is 150 °C, reaction time is 1 hour, microwave power is 500 W) to prepare a covalently organic framework composite material; the obtained composite material is prepared into a covalently organic framework in-situ crosslinked crystalline ultrafilm with excellent pore properties through washing, purification, and coating (substrate roughness is 1 μm, substrate size is 50 cm 2 , coating speed is 5 mm / s, and the slurry solvent is N,N-dimethylformamide), and the specific surface area is 314 m 2 / g, and the average pore diameter is 2.52 nm.

[0049] Comparative Example 3 of the present invention provides a method for preparing a covalently organic framework in-situ crosslinked crystalline ultrafilmmembrane, which basically adopts the method of Example 3 to prepare a fast and low-energy-consumption covalently organic framework crystalline ultrafilmmembrane. The difference is that in this example, the solvothermal method is used to prepare the covalently organic framework in-situ crosslinked crystalline ultrafilmmembrane. Specifically, multi-walled carbon nanotubes and isopropenyltriethoxysilane (the mass ratio of carbon nanotubes to isopropenyltriethoxysilane is 2:1) are dissolved in tetrahydrofuran (the mass ratio of carbon nanotubes to tetrahydrofuran is 1:5), the pH value is adjusted to 3 by acetic acid, and the reaction is carried out at 60 °C for 12 hours by the silane coupling agent method to prepare amino-functionalized carbon nanotubes; the obtained amino-functionalized carbon nanotubes, 4-aminophenyltrimethylsilane, 1,2,4,5-benzenetetracarboxylic dianhydride (the molar ratio of functional groups is 2:1), and p-toluenesulfonic acid are dispersed in N,N-dimethylformamide (the volume ratio of p-toluenesulfonic acid to N,N-dimethylformamide is 1:5), and the covalently organic framework composite material is prepared by the solvothermal method (the reaction temperature is 100 °C and the reaction time is 72 hours); the obtained composite material is prepared into a covalently organic framework in-situ crosslinked crystalline ultrafilmmembrane with excellent pore properties by cleaning and purification and the solution casting method (the mass fraction of the solute is 20%, the mold size is 100 cm 2 , the casting speed is 3 mL / min, and the casting temperature is 40 °C), and the specific surface area is 355 m 2 / g, and the average pore diameter is 2.43 nm.

[0050] The structure characterization and performance test are as follows.

[0051] Scanning electron microscope observation: The microstructure of the covalently organic framework in-situ crosslinked crystalline ultrafilmmembrane was observed by a field emission scanning electron microscope (model JSM-7900F, JEOL, Japan) ( Figure 1 , Figure 3 , Figure 5 , Figure 7 ).

[0052] Transmission electron microscope observation: The microstructure of the covalently organic framework in-situ crosslinked crystalline ultrafilmmembrane was observed by a field emission transmission electron microscope (model TECNI G2 TF20, FEI Company, Netherlands) ( Figure 2 , Figure 4 , Figure 6 , Figure 8 ).

[0053] Filtration performance test: The air filtration performance of the covalently organic framework in-situ crosslinked crystalline ultrafilmmembrane (area 25 cm 2 ) was tested by a CLJ-3016 type laser dust particle counter (Shenzhen Huashengchang Machinery Experiment Co., Ltd.), and the gas flow rate was set to 85 L / min. Each group of filter membranes was tested at least at 3 different positions, and the results were averaged.

[0054] Hydrogen sulfide adsorption performance test: A gas sorption analyzer (ASAP 2020, Micromeritics, USA) was used to adsorb SO 2 . High-purity gas SO 2 (99.999%) was used for adsorption measurement, while the free space was measured with helium gas (99.999%). Isothermal adsorption was carried out at 273 K (ice-water bath) and 298 K (water bath).

[0055] Experimental results: As shown in Figure 1 , Figure 3 , Figure 5 and Figure 7 , the original carbon nanotubes clearly exhibited a hollow tubular structure, which was consistent with their common structural characteristics. The three-dimensional tubular structure was conducive to the realization of functions such as air flow entry and gas transport. For the covalently organic framework in-situ cross-linked crystalline ultrafilm, it presented a thicker tubular morphology than the original carbon nanotubes. As can be seen from the electron microscopy images, this was due to the successful coating of a two-dimensional covalently organic framework layer on the surface of the carbon nanotubes, and the covalently organic framework layer was tightly combined with the carbon nanotubes. This unique structure played a key role in the applications of the material in dust interception and poisonous gas adsorption.

[0056] As shown in Figure 2 , Figure 4 , Figure 6 , Figure 8 , the typical hollow tubular structure of the original carbon nanotubes could be observed, with a clear tube wall and uniform tube diameter. This structural characteristic enabled them to act as a good support framework and growth template in the composite material. The transmission electron microscopy images of the covalently organic framework in-situ cross-linked crystalline ultrafilm clearly showed the two-dimensional covalently organic framework thin layer covalently grafted on the surface of the carbon nanotubes. The covalently organic framework thin layer was tightly connected to the carbon nanotubes, forming a unique core-shell structure.

[0057] Table 1 compares the specific surface area, average pore size, dust interception efficiency, and SO 2 adsorption amount results of the covalently organic framework in-situ cross-linked crystalline ultrafilms obtained in the examples and comparative examples.

[0058] Table 1

[0059] Examples 1-4 had a relatively high specific surface area (612 m 2 / g - 787 m 2 / g) and a relatively small pore size (1.09 nm - 1.55 nm) because the covalently organic framework grew uniformly and orderly on the surface of the amino-functionalized carbon nanotubes, thus fully exposing the excellent pore properties of the covalently organic framework. The specific surface areas of Comparative Examples 1-3 were only 248 - 355 m2 / g, with an average pore size of 2.21 - 2.52 nm. This is because the growth process and growth mode of the covalent organic framework on the surface of the carbon nanotubes were not controlled, resulting in the disordered growth and close packing of the covalent organic framework.

[0060] The interception and adsorption capabilities of dust and poisonous gases are closely related to the specific surface area and pore size. The PM of Examples 1 - 4 with a large specific surface area and a small pore size 0.3 - 2.5 interception efficiency is all above 97.4%, and the SO 2 adsorption capacity is all above 5.4 mmol / g, showing good dust and poisonous gas adsorption capabilities. Among them, Example 1 with the highest specific surface area and the smallest pore size performs the best in the interception and adsorption of dust and poisonous gases. The PM 0.3 - 2.5 interception efficiency is higher than 99.6%, and the SO 2 adsorption capacity is 7.2 mmol / g, far higher than that of Comparative Example 1 with a low specific surface area and a large pore size (SO 2 adsorption capacity is 1.9 mmol / g).

[0061] The present invention provides a high - yield and low - energy - consumption deep purification PM and SO 2 covalent organic framework in - situ cross - linked crystalline ultra - film and its preparation method. There are many specific methods and ways to implement this technical solution. The above - mentioned is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and retouches can be made, and these improvements and retouches should also be regarded as the protection scope of the present invention. Each component not clearly defined in this embodiment can be realized by the prior art.

Claims

1. A method for preparing a covalent organic framework in-situ cross-linked crystalline super membrane for deep purification of PM and SO2, characterized in that: The following steps are involved: Step S1, dispersing carbon nanotubes and a coupling agent in an organic reagent to obtain a mixed solution, adjusting the pH value of the mixed solution, and then using a silane coupling agent method to prepare amino carbon nanotubes; Step S2, dispersing the aldehyde ligand, the amine ligand and the catalyst and the amino carbon nanotubes obtained in step S1 in a reaction solvent, and preparing a covalent organic framework composite material by a microwave-assisted method; Step S3, cleaning and purifying the covalent organic framework composite material obtained in step S2, and preparing a covalent organic framework in-situ cross-linked crystalline super membrane for deep purification of PM and SO2 through processing and molding technology.

2. The method for preparing the covalent organic framework in-situ cross-linked crystalline super membrane for deep purification of PM and SO2 according to claim 1, characterized in that: In step S1, the carbon nanotubes are one or more of single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes, the coupling agent is one or more of methyltriethoxysilane, vinyltriethoxysilane, isopropenyltriethoxysilane, γ-aminopropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ-glycidyloxypropyltrimethoxysilane, and the mass ratio of the carbon nanotubes to the coupling agent is 2:1~1:

2.

3. The method for preparing the covalent organic framework in-situ cross-linked crystalline super membrane for deep purification of PM and SO2 according to claim 1, characterized in that: In step S1, the organic reagent is one or more of methanol, ethanol, isopropanol, toluene, dichloromethane, chloroform, tetrahydrofuran, dioxane, and acetone, and the mass ratio of carbon nanotubes to the organic reagent is 1:5-1:

15.

4. The method for preparing a covalent organic framework in-situ cross-linked crystalline super membrane for deep purification of PM and SO2 according to claim 1, characterized in that: The method for adjusting the pH value of the mixed solution in step S1 is to add a pH adjusting agent to the mixed solution, wherein the pH adjusting agent is one or more of acetic acid, hydrochloric acid, and sulfuric acid, and the pH value of the mixed solution after adjustment is in the range of 3 to 6.

5. The method for preparing the covalent organic framework in-situ cross-linked crystalline super membrane for deep purification of PM and SO2 according to claim 1, characterized in that: The reaction temperature of the silane coupling agent method in step S1 is 60-90° C., and the reaction time is 6-12 h.

6. The method for preparing a covalent organic framework in-situ cross-linked crystalline super membrane for deep purification of PM and SO2 according to claim 1, characterized in that: In step S2, the aldehyde ligand is one or more of pyromellitic anhydride, 1,2,4,5-benzenetetracarboxylic anhydride, 2,3,6,7-naphthalenetetracarboxylic anhydride, 1,4,5,8-naphthalenetetracarboxylic anhydride, terephthalaldehyde, 1,3,5-benzenetricarboxaldehyde, and 4,4'-biphenyldicarboxaldehyde; the amine ligand is one or more of tris-4-aminophenylmethane, tetrakis-4-aminophenylmethane, 4-aminophenyltrimethylsilane, N-aryl dibenzophenone imine, and ethylenediamine; and the functional group molar ratio of the amine ligand to the aldehyde ligand is 2:1~1:

2.

7. The method for preparing a covalent organic framework in-situ cross-linked crystalline super membrane for deep purification of PM and SO2 according to claim 1, characterized in that: In step S2, the reaction solvent is one or more of m-cresol, acetonitrile, water, n-butanol, N,N-dimethylformamide, and dimethyl sulfoxide; the catalyst is one or more of isoquinoline, acetic acid, p-toluenesulfonic acid, metal trifluoromethanesulfonate, and piperidine; and the volume ratio of the catalyst to the reaction solvent is 1:5 to 1:

20.

8. The method for preparing a covalent organic framework in-situ cross-linked crystalline super membrane for deep purification of PM and SO2 according to claim 1, characterized in that: The reaction temperature of the microwave-assisted method in step S2 is 60-150° C., the reaction time is 0.5-6 h, and the microwave power is 250-500 W.

9. The method for preparing a covalent organic framework in-situ cross-linked crystalline super membrane for deep purification of PM and SO2 according to claim 1, characterized in that: The processing and forming technology in step S3 is one or more of vacuum filtration, coating, solution casting, and layer-by-layer self-assembly.

10. A covalent organic framework in-situ cross-linked crystalline supermembrane prepared by the method for preparing a covalent organic framework in-situ cross-linked crystalline supermembrane for deep purification of PM and SO2 as described in any one of claims 1 to 9.

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