CN111205475A - Porous COFs block and application thereof in isomer separation - Google Patents
Porous COFs block and application thereof in isomer separation Download PDFInfo
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- 238000000034 method Methods 0.000 claims description 10
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Images
Classifications
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G83/00—Macromolecular compounds not provided for in groups C08G2/00 - C08G81/00
- C08G83/008—Supramolecular polymers
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D59/00—Separation of different isotopes of the same chemical element
- B01D59/22—Separation by extracting
- B01D59/26—Separation by extracting by sorption, i.e. absorption, adsorption, persorption
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/22—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material
- B01J20/223—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material containing metals, e.g. organo-metallic compounds, coordination complexes
- B01J20/226—Coordination polymers, e.g. metal-organic frameworks [MOF], zeolitic imidazolate frameworks [ZIF]
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C201/00—Preparation of esters of nitric or nitrous acid or of compounds containing nitro or nitroso groups bound to a carbon skeleton
- C07C201/06—Preparation of nitro compounds
- C07C201/16—Separation; Purification; Stabilisation; Use of additives
Abstract
The invention discloses a porous COFs block material and application thereof in isomer separation, wherein 2,4, 6-tri (4-aminophenyl) -1,3, 5-triazine (TAPT) and diformaldehyde monomers are firstly subjected to Shiff-base reaction to prepare amphiphilic COFs particles, then the amphiphilic COFs particles are used as a surfactant to prepare O/W type Pickering emulsion, and then the Pickering emulsion is used as a template to prepare the porous COFs block material through freeze drying. The porous COFs block material has good chemical stability and thermal stability, adjustable porosity and controllable density, has good mechanical property, can be cut into materials with different geometric shapes, can realize effective separation of 2-nitrotoluene, 4-nitrotoluene, 2-chloronitrobenzene, 4-chloronitrobenzene and other isomeric forms, has separation and recovery efficiency of about 80 percent, and can be recycled.
Description
Technical Field
The invention belongs to the technical field of materials, and particularly relates to a porous COFs block material and application of the material in the aspect of high-efficiency separation of isomers.
Background
The porous material has the characteristics of large specific surface area, low density, light weight, various structures and the like, so that the porous material plays more and more important roles in the fields of catalysis, separation, new energy sources, health technology and the like. With the progress of human society and the development of scientific technology, new requirements are continuously imposed on porous materials to meet the needs of human beings. The porous material has undergone the development process from natural acquisition to artificial synthesis, from inorganic porous to organic inorganic doped porous to porous organic material. Covalent Organic Frameworks (COFs) are ordered crystalline porous materials formed by linking light elements C, O, N and B through reversible covalent bonds. COFs can adjust channel size, channel structure, and surface chemistry through molecular design of monomers. The catalyst has the advantages of high chemical stability, high specific surface area, high order and the like, so the catalyst has excellent application prospect in the fields of gas storage, photoelectricity, catalysis and the like. This field has been rapidly developing since the first reports of COFs by the Yaghi project group in 2005. COFs are generally produced by reacting structurally rigid monomers, so that the resulting product is predominantly in powder form. However, the COFs powders have very low solubility, which makes subsequent processing difficult. It is therefore of particular importance how to prepare COFs and process them into an applicable material form.
Isomers tend to have the same or similar chemical properties due to the same molecular formula and the same chemical bonds, and are in a very large number in organic compounds, but when used as synthetic intermediates or functional molecules, the isomers need a definite molecular structure, so that the separation of the compounds faces more difficulties and challenges. The traditional method comprises a common rectification method, a melting crystallization method, a freezing point method and a gas chromatography method, but the problems of high energy consumption and unsatisfactory separation effect are often encountered. For example, 2-nitrotoluene, 4-nitrotoluene, 2-chloronitrobenzene, 4-chloronitrobenzene and other isomers are important organic synthesis intermediates, and have wide application in the fields of synthetic medicines, pesticides, dyes and the like. At present, the separation of the compounds mainly takes rectification with high energy consumption as a main means, so that the development of high-efficiency and green separation of the isomers of the compounds has important research significance.
Disclosure of Invention
In order to overcome the drawbacks of the prior art described above, it is an object of the present invention to provide a porous COFs bulk material and its use for the high efficiency separation of isomers.
In order to achieve the above object, the porous COFs bulk material of the present invention is prepared by the following method:
1. preparation of amphiphilic COFs particles
Taking 1, 2-dichlorobenzene and mesitylene as a mixed solvent, standing and reacting 2,4, 6-tris (4-aminophenyl) -1,3, 5-triazine and a diformaldehyde monomer shown in a formula I at 100-130 ℃ for 5-7 days under anhydrous and oxygen-free conditions, centrifugally separating precipitates, washing with anhydrous tetrahydrofuran, extracting by a Soxhlet extractor, and drying products in vacuum to obtain amphiphilic COFs particles with structural units shown in a formula II;
in the formulae I and II, R represents H or C1～C3An alkyl group.
2. Preparation of O/W type Pickering emulsion
Under the condition of room temperature, taking mesitylene containing amphiphilic cholesterol as an oil phase, taking a polyvinyl alcohol water solution with the mass concentration of 1% -3% as a water phase, and taking the amphiphilic COFs particles prepared in the step 1 as a surfactant to prepare O/W type Pickering emulsion, wherein the volume content of the water phase in the O/W type Pickering emulsion is 30% -70%, the content of the amphiphilic COFs particles is 0.02-0.05 g/mL, and the content of the amphiphilic cholesterol is 0.006-0.009 g/mL; wherein the structural formula of the amphiphilic cholesterol is shown as follows:
wherein n is an integer of 4 to 10.
3. Preparation of porous COFs bulk Material
And (3) freeze-drying the O/W type Pickering emulsion prepared in the step (2), washing the obtained block material with ethanol and dichloromethane in sequence, drying the block material at 40-50 ℃ for 5-8 hours, and then drying the block material at room temperature to constant weight to obtain the porous COFs block material.
The porous COFs block material prepared by the method is of a multi-level pore structure, has elasticity, can be cut at will, and has the density of 0.040-0.065 g/cm3The pore size distribution is 400 nm-2 μm, and the porosity is 30% -74%.
In the step 1, the molar ratio of the 2,4, 6-tri (4-aminophenyl) -1,3, 5-triazine to the diformaldehyde monomer is preferably 1: 2-5.
In the step 2, the O/W type Pickering emulsion preferably has a water phase volume content of 40-50%, amphiphilic COFs particles content of 0.03-0.04 g/mL, and amphiphilic cholesterol content of 0.006-0.009 g/mL.
The porous COFs block material can be used for separating isomeride 2-nitrotoluene and 4-nitrotoluene or isomeride 2-chloronitrobenzene and 4-chloronitrobenzene.
The preparation method comprises the steps of firstly preparing amphiphilic COFs particles by Shiff-base reaction of 2,4, 6-tri (4-aminophenyl) -1,3, 5-triazine (TAPT) and dimethyl aldehyde monomers, then preparing O/W type Pickering emulsion by using the amphiphilic COFs particles as a surfactant, and then preparing the porous COFs bulk material by using the O/W type Pickering emulsion as a template and freeze drying. Compared with the prior art, the invention has the following beneficial effects:
1. compared with the traditional COFs insoluble powder or film, the porous COFs block material not only has good chemical stability and thermal stability of the traditional COFs material, but also has a multi-level pore structure of the traditional block material, shows good elasticity, can be cut at will, has adjustable density and lays a foundation for post-processing preparation of the COFs material.
2. The preparation method of the porous COFs block material is simple to operate, mild in reaction condition, low in equipment requirement and suitable for large-scale production. The O/W type Pickering emulsion adopted in the preparation process of the porous COFs block material is stable and can be stable for half a year at normal temperature, and thus, the preparation method provides guarantee for preparing materials by an emulsion template method. And the porous COFs bulk material with adjustable porosity and controllable density can be obtained by adjusting the content of the water phase in the Pickering emulsion system. The preparation of COFs bulk materials by freezing and drying the Pickering emulsion avoids uncontrolled evaporation of the oil phase, so that the material with low shrinkage and stable structure is obtained, and the preparation method is simple to operate and is suitable for preparing larger bulk materials.
3. The porous COFs block can be prepared into COFs cake column chromatography for isomer separation by cutting, so that the isomers of 2-nitrotoluene, 4-nitrotoluene, 2-chloronitrobenzene and 4-chloronitrobenzene are efficiently separated, and the recovery rate is about 80%; and the COFs blocks can be recycled after the separation is finished. The height dimension of the COFs cake column chromatogram is smaller than that of porous COFs block materials and other reported separation devices, the diameter of the COFs cake column chromatogram is 5-10 mm, the height of the COFs cake column chromatogram is 1-5 mm, and a new thought is provided for application of materials. The separation process of the porous COFs block material on the isomer is simple and convenient to operate, the condition is mild, and the industrial application is expected to be realized.
Drawings
FIG. 1 is a photograph of contact angles of amphiphilic COFs particles prepared in example 1.
FIG. 2 is a scanning electron micrograph of the amphiphilic COFs particles prepared in example 1.
FIG. 3 is a photograph of an O/W type Pickering emulsion having a water content of 40% obtained in example 1.
FIG. 4 is a visual photograph of an O/W type Pickering emulsion having a water content of 40% obtained in example 1, observed over time.
FIG. 5 is a scanning electron microscope image of porous COFs bulk material prepared from O/W type Pickering emulsion with 40% water content in example 1.
FIG. 6 is a high-resolution TEM image of porous COFs bulk material prepared from an O/W type Pickering emulsion with a water content of 40% in example 1.
FIG. 7 is a graph showing the pore size distribution of porous COFs bulk material prepared from the O/W type Pickering emulsion having a water content of 40% in example 1.
FIG. 8 is a thermogram of porous COFs bulk made from O/W type Pickering emulsion with 40% water content in example 1.
FIG. 9 is a photograph of the compression and recovery of porous COFs bulk material prepared from the O/W type Pickering emulsion of example 1 with a water content of 40%.
FIG. 10 is a photograph of an O/W type Pickering emulsion having a water content of 30% obtained in example 2.
FIG. 11 is a scanning electron micrograph of porous COFs bulk material prepared from O/W type Pickering emulsion having a water content of 30% in example 2.
FIG. 12 is a photograph of an O/W type Pickering emulsion having a water content of 70% obtained in example 5.
FIG. 13 is a scanning electron micrograph of porous COFs bulk material prepared from O/W type Pickering emulsion with 70% water content in example 5.
FIG. 14 is a plot of the concentration of the isomers 2-nitrotoluene, 4-nitrotoluene separated by COFs cake column over time for various test times in example 7.
FIG. 15 is a graph of the separation concentration of the COFs cake column over time at various test times after 5 reuses of the COFs cake column in example 7.
FIG. 16 is a graph of the concentration of the isomers 2-chloronitrobenzene and 4-chloronitrobenzene separated by COFs cake column at different test times as a function of time in example 8.
FIG. 17 is a graph of the separation concentration of the COFs cake column over time at various test times after 5 reuses of the column in example 8.
Detailed Description
The invention will be further described in detail with reference to the following figures and examples, but the scope of the invention is not limited to these examples.
Example 1
1. Preparation of amphiphilic COFs particles
0.708g (2mmol) of 2,4, 6-tris (4-aminophenyl) -1,3, 5-triazine and 0.134g (1mmol) of terephthalaldehyde were added to a mixed solvent of 20mL1, 2-dichlorobenzene and 20mL mesitylene, and degassing treatment was carried out by three freeze-pump-thaw cycles, after which the mixture was allowed to stand in an oil bath at 120 ℃ for 7 days, after which the precipitate was centrifuged, washed with anhydrous tetrahydrofuran, extracted by a Soxhlet extractor for 24 hours, and vacuum-dried at 80 ℃ for 24 hours to give yellow amphiphilic COFs particles having the structural unit of formula II (R ═ H).
Scanning electron microscope test observation is carried out on the obtained yellow amphiphilic COFs particles, and the result is shown in figure 1, the microscopic morphology of the particles is of a spherical structure, and the size distribution of the particles is 5-15 microns. Meanwhile, the contact angle test analysis of the obtained yellow powder was performed, and the test result is shown in fig. 2, the contact angle of the COFs particles was about 59.2 °, and the COFs particles had hydrophilicity and lipophilicity because the COFs particles have hydrophobic aromatic rings as main components, but have hydrophilicity due to high nitrogen content.
2. Preparation of Pickering emulsion
Under the condition of room temperature and at the stirring speed of 11400rpm, 17.5mg of amphiphilic COFs particles are uniformly dispersed in 200 mu L of 2 mass percent polyvinyl alcohol aqueous solution, then the polyvinyl alcohol aqueous solution is added into 300 mu L of mesitylene containing 4mg of amphiphilic cholesterol (n ═ 8), the obtained mixed solution is fully and uniformly mixed at the constant speed of 11400rpm until a stable O/W type Pickering emulsion is formed, the volume content of an aqueous phase in the Pickering emulsion is 40%, the content of the amphiphilic COFs particles is 0.035g/mL, and the content of the amphiphilic cholesterol is 0.008 g/mL. As can be seen from fig. 3, the resulting Pickering emulsion droplets were densely distributed, and no phase separation occurred after three weeks of observation with continued standing (see fig. 4).
3. Preparation of porous COFs bulk Material
And (3) freeze-drying the Pickering emulsion prepared in the step (2) for 12 hours to generate an independent COFs block material, washing the obtained block material with ethanol for four times, then washing with dichloromethane for three times, drying in an oven at 40 ℃ for 8 hours, and finally drying at room temperature to constant weight to obtain the porous COFs block material.
The obtained bulk was characterized by using a table scanning electron microscope model TM 3030 manufactured by Hitachi and a field emission transmission electron microscope model Tecnaig2F20 manufactured by FEI, and the results are shown in FIGS. 5 and 6. As can be seen from FIG. 5, the interior of the obtained block is a distinct porous structure, and the internal structure is relatively regular. As can be seen from FIG. 6, the obtained bulk had a distinct polycrystalline diffraction ring.
The pore size distribution of the obtained block was characterized by using an AUTOPORE 9500 mercury porosimeter, and the results are shown in fig. 7. As can be seen, the mean pore size distribution is 1.69 μm, the porosity was determined to be 45.32%, within error of 40% of the theoretical porosity. The density of the product is 0.058g/cm3。
The obtained block is tested by adopting a Q1000DSC + LNCS + FACS Q600SDT type thermal analysis system produced by American TA company, the test result is shown in figure 8, and when the temperature reaches 900 ℃, the weight loss rate is still lower than 31 wt%, which indicates that the obtained porous COFs block has good thermal stability. As can be seen from fig. 9, the obtained block can be restored to a certain degree after being compressed by a strong force, which indicates a certain elasticity.
Example 2
In step 2 of this example, 17.5mg of amphiphilic COFs particles were uniformly dispersed in 150 μ L of a 2% aqueous solution of polyvinyl alcohol at a stirring speed of 11400rpm and then added to 350 μ L of mesitylene containing 4mg of amphiphilic cholesterol (n ═ 8), and the resulting mixed solution was sufficiently and uniformly mixed at a constant speed of 11400rpm until a stable O/W type Pickering emulsion was formed, in which the volume content of the aqueous phase was 30% (see fig. 10), the content of the amphiphilic COFs particles was 0.035g/mL, and the content of the amphiphilic cholesterol was 0.008 g/mL. The other steps were the same as in example 1, to obtain a porous COFs block (see FIG. 11).
Example 3
In step 2 of this example, 17.5mg of amphiphilic COFs particles were uniformly dispersed in 250 μ L of a 2% aqueous solution of polyvinyl alcohol at room temperature and a stirring speed of 11400rpm, and then added to 250 μ L of mesitylene containing 4mg of amphiphilic cholesterol (n ═ 8), and the resulting mixed solution was sufficiently and uniformly mixed at a constant speed of 11400rpm until a stable O/W type Pickering emulsion was formed, in which the volume content of the aqueous phase was 50%, the content of the amphiphilic COFs particles was 0.035g/mL, and the content of the amphiphilic cholesterol was 0.008 g/mL. The other steps were the same as in example 1 to obtain porous COFs bulk materials.
Example 4
In step 2 of this example, under room temperature conditions, at a stirring speed of 11400rpm, 17.5mg of amphiphilic COFs particles were uniformly dispersed in 300 μ L of a 2% polyvinyl alcohol aqueous solution, and then added to 200 μ L of mesitylene containing 4mg of amphiphilic cholesterol (n ═ 8), and the resulting mixed solution was sufficiently and uniformly mixed at a constant speed of 11400rpm until a stable O/W type Pickering emulsion was formed, in which the volume content of the aqueous phase was 60%, the content of the amphiphilic COFs particles was 0.035g/mL, and the content of the amphiphilic cholesterol was 0.008 g/mL. The other steps were the same as in example 1 to obtain porous COFs bulk materials.
Example 5
In step 2 of this example, 17.5mg of amphiphilic COFs particles were uniformly dispersed in 350 μ L of a 2% by mass aqueous solution of polyvinyl alcohol at room temperature and a stirring speed of 11400rpm, and then added to 150 μ L of mesitylene containing 4mg of amphiphilic cholesterol (n ═ 8), and the resulting mixed solution was sufficiently mixed at a constant speed of 11400rpm until a stable O/W type Pickering emulsion (see fig. 12) was formed, in which the volume content of the aqueous phase in the Pickering emulsion was 70%, the content of the amphiphilic COFs particles was 0.035g/mL, and the content of the amphiphilic cholesterol was 0.008 g/mL. The other steps were the same as in example 1, to obtain a porous COFs block (see FIG. 13).
Example 6
0.708g (2mmol) of 2,4, 6-tris (4-aminophenyl) -1,3, 5-triazine and 0.164g (1mmol) of 2, 5-dimethyl-terephthaldehyde are added to a mixed solvent of 20mL of 1, 2-dichlorobenzene and 20mL of mesitylene, and degassing treatment is carried out by three freeze-pump-thaw cycles, and after the degassing treatment, the mixture is allowed to stand in an oil bath at 120 ℃ for 7 days, and after the reaction, the precipitate is centrifugally separated, washed with anhydrous tetrahydrofuran, extracted by a Soxhlet extractor for 24 hours, and vacuum-dried at 80 ℃ for 24 hours to obtain a structural unit represented by formula II (R ═CH3) Yellow amphiphilic COFs particles of (1). Other steps were the same as in example 1 to obtain porous COFs bulk materials.
Example 7
Separation of isomers 2-nitrotoluene and 4-nitrotoluene from porous COFs bulk prepared in example 1
The porous COFs bulk prepared in example 1 was cut into COFs cake columns having a diameter of 10mm and a height of 5mm, and the COFs cake column material was put into a syringe having the same diameter to prepare COFs cake column chromatography. The COFs cake column chromatography was connected to a peristaltic pump and 10. mu.L, 2.92X 10-4mol/L acetonitrile solution of 2-nitrotoluene and 10. mu.L of 2.92X 10-4And uniformly mixing the acetonitrile solution of mol/L4-nitrotoluene, adding the mixture into COFs (chemical oxygen demand Fs) cake column chromatography, and performing cake column chromatographic separation by taking a mixed solution of ethanol and acetonitrile in a volume ratio of 1:4 as a mobile phase at a flow rate of 20 mL/min. Detecting the product separated by the column per minute by using an ultraviolet visible spectrophotometer (the ultraviolet detection wavelength of the 2-nitrotoluene is 265nm, the ultraviolet detection wavelength of the 4-nitrotoluene is 210nm), comparing the ultraviolet spectrograms with the ultraviolet spectrograms of the 2-nitrotoluene and the 4-nitrotoluene to determine the attribution of the separated product, and then converting the standard curves of different isomers into the concentrations of the product at different test time, thereby drawing a time relation graph of the separation concentration of the cake column at different test time shown in figure 14. The results in FIG. 14 show that the separation of 4-nitrotoluene is completed in 30 minutes, and the product separated in 30-60 minutes is 2-nitrotoluene. After the separation, the COFs cake column used for the column separation is reused, and the results in FIG. 15 show that the same separation effect is achieved for 2-nitrotoluene and 4-nitrotoluene isomers after the COFs cake column is reused for 5 times.
Example 8
Separation of isomers 2-chloronitrobenzene and 4-chloronitrobenzene from porous COFs bulk prepared in example 1
The porous COFs bulk prepared in example 1 was cut into COFs cake columns having a diameter of 10mm and a height of 5mm, and the COFs cake column material was put into a syringe having the same diameter to prepare COFs cake column chromatography. The COFs cake column chromatography was connected to a peristaltic pump and 10. mu.L of 2.54X 10-4mol/L acetonitrile solution of 2-chloronitrobenzene and 10 mu L of 2.54 multiplied by 10-4And uniformly mixing the acetonitrile solution of the mol/L4-chloronitrobenzene, adding the mixture into COFs (chemical oxygen demand Fs) cake column chromatography, and carrying out cake column chromatographic separation by taking acetonitrile as a mobile phase at the flow rate of 20 mL/min. Detecting the product separated by passing through the column every minute by using an ultraviolet visible spectrophotometer (the ultraviolet detection wavelength is 210nm), comparing the ultraviolet spectrograms with 2-chloronitrobenzene and 4-chloronitrobenzene to determine the attribution of the separated product, then converting the standard curves of different isomers into the concentrations of the product at different test times, and drawing a time relation graph of the cake column separation concentration at different test times shown in figure 16, wherein the result shown in figure 16 shows that the separation of the 4-chloronitrobenzene is finished within 30 minutes, and the separated product is the 2-chloronitrobenzene within 30-70 minutes. After the separation is finished, the COFs cake column used for column separation is reused, and the results in FIG. 17 show that the same separation effect is achieved on 2-chloronitrobenzene and 4-chloronitrobenzene isomers after the COFs cake column is reused for 5 times.
Claims (6)
1. A porous COFs block material is characterized by being prepared by the following method:
(1) preparation of amphiphilic COFs particles
Taking 1, 2-dichlorobenzene and mesitylene as a mixed solvent, standing and reacting 2,4, 6-tris (4-aminophenyl) -1,3, 5-triazine and a diformaldehyde monomer shown in a formula I at 100-130 ℃ for 5-7 days under anhydrous and oxygen-free conditions, centrifugally separating precipitates, washing with anhydrous tetrahydrofuran, extracting by a Soxhlet extractor, and drying products in vacuum to obtain amphiphilic COFs particles with structural units shown in a formula II;
in the formulae I and II, R represents H or C1～C3An alkyl group;
(2) preparation of O/W type Pickering emulsion
Under the condition of room temperature, taking mesitylene containing amphiphilic cholesterol as an oil phase, taking a polyvinyl alcohol water solution with the mass concentration of 1% -3% as a water phase, taking the amphiphilic COFs particles prepared in the step (1) as a surfactant, and preparing an O/W-type Pickering emulsion, wherein the volume content of the water phase in the O/W-type Pickering emulsion is 30% -70%, the content of the amphiphilic COFs particles is 0.02-0.05 g/mL, and the content of the amphiphilic cholesterol is 0.006-0.009 g/mL;
the structural formula of the amphiphilic cholesterol is shown as follows:
wherein n is an integer of 4-10;
(3) preparation of porous COFs bulk Material
And (3) freeze-drying the O/W type Pickering emulsion prepared in the step (2), washing the obtained block material with ethanol and dichloromethane in sequence, drying the block material at 40-50 ℃ for 5-8 hours, and then drying the block material at room temperature to constant weight to obtain the porous COFs block material.
2. The porous COFs block according to claim 1, wherein: the porous COFs block material is of a multi-level pore structure, has elasticity and can be cut at will, and the density of the porous COFs block material is 0.040-0.065 g/cm3The pore size distribution is 400 nm-2 μm, and the porosity is 30% -74%.
3. The porous COFs block according to claim 1, wherein: in the step (1), the molar ratio of the 2,4, 6-tri (4-aminophenyl) -1,3, 5-triazine to the dimethyl aldehyde monomer is 1: 2-5.
4. The porous COFs block according to claim 1, wherein: in the step (2), the volume content of the water phase in the O/W type Pickering emulsion is 40-50%, the content of amphiphilic COFs particles is 0.03-0.04 g/mL, and the content of amphiphilic cholesterol is 0.006-0.009 g/mL.
5. Use of porous COFs bulk material according to claim 1 for the separation of the isomers 2-nitrotoluene and 4-nitrotoluene.
6. Use of porous COFs bulk material according to claim 1 for the separation of the isomers 2-chloronitrobenzene and 4-chloronitrobenzene.
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