A hierarchical porphyrin-based covalent organic framework material and a preparation method and application thereof

Abstract

The present application relates to the technical field of covalent organic framework material, in particular to a hierarchical pore alkenyl covalent organic framework material and a preparation method and application thereof.The present application comprises the following steps: preparing a dense packing structure microsphere solid, adding a ligand of a covalent organic framework into the microsphere solid, obtaining a microsphere solid-covalent organic framework composite by controlling reaction conditions, removing the microsphere solid in the composite to form a pore, and obtaining the hierarchical pore alkenyl covalent organic framework material.The covalent organic framework material itself has a nanoscale pore, and the dense packing structure microsphere solid is introduced to divide the ligand of the covalent organic framework to form the smallest ligand of the covalent organic framework, which is more conducive to forming the hierarchical pore.The microsphere solid in the microsphere solid-covalent organic framework composite occupies most of the space, and a large number of cavities are left after the microsphere solid is removed, and a mesopore is formed at the connection between the macropore and the micropore, so that the alkenyl covalent organic framework material with the hierarchical pore structure is finally obtained.

Description

Technical Field

[0001] This invention relates to the field of covalent organic framework materials technology, and particularly to a hierarchical porous alkenyl covalent organic framework material, its preparation method, and its applications. Background Technology

[0002] Covalent organic frameworks (COFs) are a new type of crystalline porous materials with well-defined and highly designable structures. They are characterized by low density, high specific surface area, and ease of modification, and have therefore received widespread attention and research in recent years.

[0003] Due to their highly customizable structures, covalent organic frameworks (COFrames) have a range of potential applications in chemistry and chemical engineering, including advanced uses such as photoelectrochemical response, catalysis, adsorption, filtration, separation, and drug delivery. As a special type of porous material, the topological characteristics of COFrames, particularly the pore size and uniformity in each dimension, are key factors determining their suitability for specific applications. However, the rational development of high-stability COFrames with low cost and hierarchical pore structures remains a significant challenge. Summary of the Invention

[0004] To achieve the above objectives, the present invention provides a method for preparing a hierarchical porous alkenyl-based covalent organic framework material, comprising:

[0005] Preparation of close-packed microsphere solids;

[0006] A covalent organic framework ligand and a catalyst are added to a reaction vessel containing the microsphere solid, and the reaction vessel is then sealed and subjected to vacuum treatment. The covalent organic framework ligand has micropores, and the size of the microsphere is larger than the size of the micropores.

[0007] The reaction vessel, after being vacuum treated, is first preheated and then continuously heated. The preheating causes the ligands of the covalent organic framework to form a molten state and immerse themselves in the gaps between the microspheres. The continuous heating then causes the ligands of the covalent organic framework to gradually polymerize and crystallize, thereby obtaining a microsphere solid-covalent organic framework complex.

[0008] An etchant is added to the microsphere solid-covalent organic framework composite to remove the microsphere solid and form pores, thereby obtaining an alkenyl covalent organic framework material with a hierarchical pore structure.

[0009] Optionally, the step of preparing the microsphere solid with a close-packed structure includes:

[0010] Microspheres of the same order of magnitude are uniformly dispersed in a first solvent to obtain a microsphere suspension;

[0011] The microsphere suspension was centrifuged and allowed to settle.

[0012] After removing the excess first solvent from centrifugation sedimentation, dry, close-packed microsphere solids are obtained.

[0013] Optionally, the first solvent includes one of methanol, ethanol, acetone, and tetrahydrofuran.

[0014] Optionally, the particle size range of the microspheres is 100nm-1000nm, and the microspheres include one of titanium dioxide microspheres, silicon microspheres, and silica microspheres.

[0015] Optionally, the ligands of the covalent organic framework include one or more of the following: 2,4,6-trimethyl-1,3,5-triazine, 2,4,6-trimethylpyridine, 2,4,6-trimethylpyrimidine, 1,3,5-tribenzylnitrile, terephthalaldehyde, biphenyl dicarboxaldehyde, bipyridine dicarboxaldehyde, and p-terephenyl dicarboxaldehyde; the catalyst includes one of benzoic anhydride or benzoic acid.

[0016] Optionally, the reaction vessel is preheated and continuously heated in an oven. The preheating temperature range is 50℃-130℃, the preheating time range is 5min-30min, the continuous heating temperature range is 160℃-220℃, and the continuous heating time range is 2 days-7 days.

[0017] Optionally, the etching agent includes one of hydrofluoric acid, ammonium fluoride solution, and strong alkaline solution, wherein the strong alkaline solution includes one of potassium hydroxide aqueous solution, sodium hydroxide aqueous solution, and lithium hydroxide aqueous solution.

[0018] Optionally, it further includes: grinding the microsphere solid-covalent organic framework composite into covalent organic framework composite powder, and then using an etchant to remove the microsphere solid in the microsphere solid-covalent organic framework composite powder to form pores.

[0019] Optionally, before obtaining the microsphere solid-covalent organic framework composite, the ligands of the crystallized covalent organic framework are further subjected to a second washing and a second drying. The second washing agent includes one of methanol and ethanol, and the second washing method includes one of Soxhlet extraction washing and filtration washing. The temperature range of the second drying is 60℃-120℃.

[0020] Optionally, the hierarchical pores include macropores, mesopores, and micropores, wherein the macropore diameter ranges from 100nm to 500nm, the mesopore diameter ranges from 2nm to 3nm, and the micropore diameter ranges from 1nm to 2nm.

[0021] This invention also provides a hierarchical porous alkenyl covalent organic framework material, prepared by any of the above-described preparation methods.

[0022] This invention also provides an application of the hierarchical porous alkenyl covalent organic framework material described above in the photocatalytic hydrogen evolution reaction.

[0023] In summary, the advantages and beneficial effects of the present invention are as follows:

[0024] This invention provides a hierarchical porous alkenyl covalent organic framework material, its preparation method, and its application, comprising: preparing a close-packed microsphere solid; adding a covalent organic framework ligand and a catalyst to a reaction vessel containing the microsphere solid, wherein the size of the microsphere is larger than the micropore size; sealing and vacuum-treating the reaction vessel; preheating the vacuum-treated reaction vessel and then continuously heating it to obtain a microsphere solid-covalent organic framework composite; preparing the microsphere solid-covalent organic framework composite into a covalent organic framework composite powder, adding an etchant to remove the microsphere solid and form pores, thereby obtaining an alkenyl covalent organic framework material with a hierarchical porous structure.

[0025] Covalent organic frameworks (COFs) are a class of chemical materials with inherently regular one-dimensional nanoscale pores. This invention introduces closely packed microspheres into which the COF is dispersed. By controlling reaction conditions, an intermediate product of the microsphere-COF composite is obtained. The microspheres are then removed from the intermediate product, ultimately yielding an alkenyl COF with hierarchical pores. On one hand, due to the low porosity between the closely packed microspheres, the addition of COF ligands to the microspheres results in uniform dispersion of the ligands within the microspheres. This allows the COF ligands to be segmented by the microspheres, forming the smallest possible COF ligands, which is more conducive to hierarchical pore formation. On the other hand, the microspheres occupy most of the space in the COF composite, making etching away the closely packed microspheres more effective. Subsequently, a large number of voids are left between the ligands of the covalent organic framework. At the same time, since the size of the close-packed microsphere solid is larger than the size of the micropores of the ligands of the covalent organic framework, the size of the voids is larger than the size of the micropores of the ligands of the covalent organic framework. Under the synergistic effect, mesopores are formed at the connection between macropores and micropores, and finally an alkenyl covalent organic framework material with macropores, mesopores and micropores is obtained, that is, an alkenyl covalent organic framework material with a hierarchical pore structure is obtained, which is more conducive to the diffusion of substances between the ligands of the covalent organic framework.

[0026] Meanwhile, this invention grinds the silica microsphere solid-covalent organic framework composite into powder. Since the macropores (hundreds of nanometers) prepared in this invention differ by several orders of magnitude from the particle size (hundreds of micrometers) of the silica microsphere solid-covalent organic framework composite powder formed after grinding, the subsequent grinding process does not affect the microscopic pore structure. Furthermore, the rigid structure of the covalent organic framework ensures that the rigid framework will not collapse after the removal of the densely packed microsphere solids. Moreover, the similar order of magnitude of the size of each microsphere results in a regular arrangement of hierarchical pores in the final alkenyl covalent organic framework material, which is more conducive to the diffusion of substances between ligands within the covalent organic framework. This avoids stress unevenness caused by disordered large and small pores, preventing the alkenyl covalent organic framework material from breaking or collapsing, affecting its uniformity, and improving its application under specific conditions. Attached Figure Description

[0027] Figure 1 The diagram shown is a flowchart illustrating a method for preparing a hierarchical porous alkenyl-based covalent organic framework material according to an embodiment of the present invention.

[0028] Figure 2 The image shown is an XRD pattern of a graded porous alkenyl-based covalent organic framework material according to Example 1 of the present invention;

[0029] Figure 3 The image shown is a scanning electron microscope (SEM) image of a bulk material of a graded porous alkenyl-based covalent organic framework according to Embodiment 1 of the present invention.

[0030] Figure 4 The image shown is a transmission electron microscope (TEM) image of the interior of a graded porous alkenyl-based covalent organic framework material according to Example 1 of the present invention.

[0031] like Figure 5 The image shown is an XRD pattern of a graded porous alkenyl-based covalent organic framework material according to Example 2 of the present invention;

[0032] like Figure 6 The image shown is a scanning electron microscope (SEM) image of a hierarchical porous alkenyl covalent organic framework material in Embodiment 2 of the present invention.

[0033] like Figure 7 The image shown is an XRD pattern of a hierarchical porous alkenyl-based covalent organic framework material according to Example 3 of the present invention;

[0034] like Figure 8 The figure shown is a schematic diagram of the photocatalytic hydrogen evolution test kinetic curves of the alkenyl covalent organic framework materials obtained by the preparation method of the alkenyl covalent organic framework material in Example 1 and Comparative Example 1 of the present invention. Detailed Implementation

[0035] Covalent organic frameworks (COFs) contain only nanoscale pores (micropores or near-micropores), but the one-dimensional nature of these pores hinders diffusion and mass transfer, significantly limiting their application in diffusion processes, particularly in mass-transfer-dependent applications such as catalysis, adsorption, and separation. This invention reduces mass transfer resistance and improves the accessibility of micropores within COFs by introducing mesopores and macropores into COFs to form hierarchical pore structures.

[0036] To facilitate understanding by those skilled in the art, the present invention will be further described in detail below with reference to specific embodiments.

[0037] This invention provides a method for preparing hierarchical porous alkenyl-based covalent organic framework materials, such as... Figure 1 As shown, it includes:

[0038] Step S100: Prepare close-packed microsphere solids;

[0039] Step S200: Add a covalent organic framework ligand and a catalyst to a reaction vessel containing the microsphere solid, then seal the reaction vessel and vacuum it. The covalent organic framework ligand has micropores, and the size of the microsphere is larger than the size of the micropore.

[0040] Step S300: The reaction vessel after vacuum treatment is preheated and then continuously heated. The preheating causes the ligands of the covalent organic framework to form a molten state and immerse themselves in the gaps between the microsphere solids. Then, the continuous heating causes the ligands of the covalent organic framework to gradually polymerize and crystallize, thereby obtaining a microsphere solid-covalent organic framework composite.

[0041] Step S400: An etchant is added to the microsphere solid-covalent organic framework composite to remove the microsphere solid in the microsphere solid-covalent organic framework composite and form pores, thereby obtaining an alkenyl covalent organic framework material with a hierarchical pore structure.

[0042] Specifically, step S100 is performed to prepare densely packed microsphere solids.

[0043] The fact that all the microspheres are of the same order of magnitude ensures that the hierarchical pores of the resulting alkenyl covalent organic framework material are arranged in a regular manner, which is more conducive to the diffusion of substances between the ligands of the covalent organic framework. This avoids the stress unevenness caused by the disordered large and small pores, which could lead to the fracture and collapse of the alkenyl covalent organic framework material, affecting the uniformity of the alkenyl covalent organic framework material and its application under specific conditions.

[0044] In this embodiment of the invention, the step of preparing microsphere solids with a close-packed structure includes:

[0045] Step S101: Microspheres of the same order of magnitude size are uniformly dispersed in a first solvent to obtain a microsphere suspension;

[0046] Step S102: Centrifuge and settle the microsphere suspension;

[0047] Step S103: Remove excess first solvent after centrifugation and sedimentation to obtain dry, densely packed microsphere solids.

[0048] In this embodiment of the invention, the particle size range of the microspheres is 100nm-1000nm, and the microspheres are silica microspheres. In other embodiments, the microspheres are either titanium dioxide microspheres or silicon microspheres.

[0049] Since the subsequent preparation of covalent organic framework materials requires the use of highly polar organic solvents such as methanol or ethanol to remove the catalyst, and the harsh synthesis conditions of high temperature (120℃-220℃), high pressure (1-10 atmospheres), and long reaction time (3-7 days), the selection of highly stable silica microspheres as the close-packed microsphere solids can effectively avoid the dissolution and corrosion of the microsphere solids by long-term, highly polar organic solvents, the deformation or even melting of the close-packed microsphere solids caused by high temperature, and the deformation of the close-packed microsphere solids caused by high pressure.

[0050] Meanwhile, the rigid structure of the covalent organic framework ensures that the rigid framework will not collapse after the removal of the close-packed microsphere solids. Furthermore, the fact that the sizes of the microspheres are all on the same order of magnitude results in a regular arrangement of hierarchical pores in the final alkenyl covalent organic framework material. This arrangement is more conducive to the diffusion of matter and the study of its principles, avoiding the stress unevenness caused by disordered large and small pores, which could lead to the fracture and collapse of the alkenyl covalent organic framework material, affecting its uniformity and improving its application under specific conditions.

[0051] In this embodiment of the invention, the first solvent includes one of methanol, ethanol, acetone, and tetrahydrofuran.

[0052] In this embodiment of the invention, the microspheres are uniformly dispersed in a first solvent by ultrasonic treatment; and the microspheres are centrifuged and settled at the bottom of the reaction vessel using a centrifuge.

[0053] Because of the high density of the microspheres, when centrifuged and settled in a centrifuge, the microspheres form a densely packed microsphere solid within the reaction vessel. The porosity of the densely packed microsphere solid is minimal, accounting for only 26% of the total porosity. This makes it easier to form hierarchical pores when the ligands of the covalent organic framework are subsequently divided into the smallest possible covalent organic framework ligands by the densely packed microsphere solid.

[0054] In this embodiment of the invention, the method for removing the excess first solvent includes one or more of the following: extracting the first solvent, evaporating the first solvent, or drying in an oven.

[0055] In step S200, a covalent organic framework ligand and a catalyst are added to a reaction vessel containing the microsphere solid, and then the reaction vessel is sealed and subjected to vacuum treatment. The covalent organic framework ligand has micropores, and the size of the microsphere is larger than the size of the micropores.

[0056] In this embodiment of the invention, the ligand of the covalent organic framework is one or more of 2,4,6-trimethyl-1,3,5-triazine, 2,4,6-trimethylpyridine, 2,4,6-trimethylpyrimidine, 1,3,5-tribenzylnitrile, terephthalaldehyde, biphenyl dicarboxaldehyde, bipyridine dicarboxaldehyde, and p-terephenyl dicarboxaldehyde.

[0057] In this embodiment of the invention, the catalyst is benzoic anhydride; in other embodiments, the catalyst is benzoic acid.

[0058] The catalyst accelerates the polymerization and crystallization rate of the ligands of the covalent organic framework, while also enabling the ligands of the covalent organic framework to better penetrate into the voids of the close-packed microsphere solid.

[0059] In this embodiment of the invention, before sealing and vacuuming the reaction vessel, the reaction vessel is further cooled with liquid nitrogen.

[0060] In step S300, the reaction vessel after vacuum treatment is preheated and then continuously heated. The preheating causes the ligands of the covalent organic framework to form a molten state and immerse themselves in the gaps between the microspheres. The continuous heating then causes the ligands of the covalent organic framework to gradually polymerize and crystallize, thereby obtaining a microsphere solid-covalent organic framework composite.

[0061] In this embodiment of the invention, the reaction vessel is preheated and continuously heated by an oven. The preheating temperature range is 50℃-130℃, the preheating time range is 5min-30min, the continuous heating temperature range is 160℃-220℃, and the continuous heating time range is 2 days-7 days.

[0062] The ligands of the covalent organic framework form a molten precursor during preheating. Under vacuum, the molten precursor is more fully immersed into the voids of the microsphere solid with the close-packed structure. During the subsequent continuous heating, a chemical reaction occurs, and the precursor gradually crystallizes to form a covalent organic framework. After the reaction is completed, a microsphere solid-covalent organic framework complex is obtained.

[0063] In this embodiment of the invention, before obtaining the microsphere solid-covalent organic framework complex, the ligands of the crystallized covalent organic framework are further subjected to a second washing and a second drying. The second washing agent is methanol, and the second washing method includes Soxhlet extraction washing for 6-12 hours or filtration washing for more than 3 times. The temperature range of the second drying is 60℃-120℃.

[0064] In other embodiments, the second detergent is ethanol.

[0065] In an embodiment of the invention, the catalyst, which is added together with the ligand of the covalent organic framework, is removed using the second detergent.

[0066] In this embodiment of the invention, the method further includes: grinding the microsphere solid-covalent organic framework composite into covalent organic framework composite powder, and then using an etchant to remove the microsphere solid in the microsphere solid-covalent organic framework composite powder to form pores.

[0067] In other embodiments, the silica microsphere solid-covalent organic framework composite is first ground to form silica microsphere solid-covalent organic framework composite powder, and then the silica microsphere solid-covalent organic framework composite powder is subjected to a second washing.

[0068] After grinding the silica microsphere solid-covalent organic framework composite, the silica microsphere solid-covalent organic framework composite becomes a powder, which makes the surface area of ​​the silica microsphere solid-covalent organic framework composite larger, which is more conducive to the subsequent removal of catalyst and the close-packed structure microsphere solid, and improves the removal rate of catalyst and close-packed structure microsphere solid.

[0069] The macropores (hundreds of nanometers) prepared in this invention are several orders of magnitude smaller than the particle size (hundreds of micrometers) of the silica microsphere solid-covalent organic framework composite powder formed after grinding. Therefore, the subsequent grinding process into powder will not affect the microscopic pore structure.

[0070] In step S400, an etchant is added to the microsphere solid-covalent organic framework composite to remove the microsphere solid in the microsphere solid-covalent organic framework composite and form pores, thereby obtaining an alkenyl covalent organic framework material with a hierarchical pore structure.

[0071] In this embodiment of the invention, an excess of etchant is provided, the etchant comprising one of hydrofluoric acid, ammonium fluoride solution, and strong alkaline solution.

[0072] In this embodiment of the invention, the strong alkaline solution includes one of potassium hydroxide aqueous solution, sodium hydroxide aqueous solution, and lithium hydroxide aqueous solution.

[0073] In this embodiment of the invention, obtaining the alkenyl covalent organic framework material with hierarchical pore structure further includes performing a third washing and a third drying on the silica-covalent organic framework composite powder after the etching process. The detergent for the third washing includes water, and the temperature range for the third drying is 60°C-120°C.

[0074] Example 1:

[0075] Step S100: Prepare silica microspheres with a close-packed structure, wherein each silica microsphere has the same order of magnitude.

[0076] In this embodiment of the invention, the steps for preparing the microsphere solid with the close-packed structure include:

[0077] Step S101: 300 mg of silica microspheres with a particle size of 300 nm are dispersed in 3 mL of methanol solvent and ultrasonically treated for 20 min to obtain a silica microsphere suspension.

[0078] In step S102, the silica microsphere suspension is transferred to a reaction vessel and placed in a centrifuge for sedimentation. The centrifuge is centrifuged at a rate of 7000 r / min for 5 min, so that the silica microspheres settle to the bottom of the reaction vessel.

[0079] In step S103, excess methanol solvent in the reaction vessel after sedimentation is first removed, and then the reaction vessel is placed in an oven and dried at 70°C for 30 minutes to completely remove the methanol solution and obtain dry silica microspheres with a close-packed structure.

[0080] The silica microspheres are precisely sized, employ diverse and environmentally friendly digestion methods, and exhibit high rigidity, making them resistant to deformation at high temperatures and in organic solvents. They are also resistant to harsh reaction environments. Furthermore, silica exhibits good chemical stability, making it less prone to side reactions with reactants and easier to control, resulting in a purer alkenyl covalent organic framework material with a hierarchical pore structure.

[0081] In step S200, 62 mg of 2,4,6-trimethyl-1,3,5-triazine, 101 mg of terephthalaldehyde, and 200 mg of benzoic anhydride as a catalyst are added to a reaction vessel containing the silica microsphere solids. The reaction vessel is then sealed and subjected to vacuum treatment.

[0082] Step S300: The reaction vessel after vacuum treatment is preheated and then continuously heated. The preheating temperature is 120°C and the preheating time is 3 hours. Then, it is continuously heated at 200°C for 3 days, so that the ligands of the covalent organic framework form a molten state and are immersed in the gaps between the silica microspheres, gradually polymerizing and crystallizing to obtain a silica microsphere solid-covalent organic framework composite.

[0083] Step S400: The silica microsphere solid-covalent organic framework composite is prepared into silica microsphere solid-covalent organic framework composite powder by grinding.

[0084] In this embodiment of the invention, before grinding the silica microsphere solid-covalent organic framework composite into powder, the silica microsphere solid-covalent organic framework composite is first washed with methanol solution using a Soxhlet extractor and then dried in an oven at 80°C for 12 hours. After that, the washed silica microsphere solid-covalent organic framework composite is ground to obtain silica microsphere solid-covalent organic framework composite powder.

[0085] In other embodiments, the silica microsphere solid-covalent organic framework composite is first ground to form silica microsphere solid-covalent organic framework composite powder, and then the silica microsphere solid-covalent organic framework composite powder is washed.

[0086] After grinding the silica microsphere solid-covalent organic framework composite, the silica microsphere solid-covalent organic framework composite becomes a powder, which makes the surface area of ​​the silica microsphere solid-covalent organic framework composite larger, which is more conducive to the subsequent removal of catalyst and the close-packed structure microsphere solid, and improves the removal rate of catalyst and close-packed structure microsphere solid.

[0087] In step S500, 10 mL of 10% hydrofluoric acid is added to the silica microsphere solid-covalent organic framework composite powder and stirred for 12 h to remove the silica microsphere solid from the silica microsphere solid-covalent organic framework composite and form pores, finally obtaining the alkenyl covalent organic framework material HVCOF-TMTPA (alkenyl covalent organic framework material with hierarchical pore structure).

[0088] In this embodiment of the invention, the silica microsphere solid-covalent organic framework composite powder etched with hydrofluoric acid is washed with 30 mL of methanol and 30 mL of tetrahydrofuran, and then dried in an oven at 80 °C for 12 h to finally obtain an alkenyl covalent organic framework material with a hierarchical pore structure.

[0089] like Figure 2 The image shown is the XRD (X-ray diffraction) pattern of the hierarchical porous alkenyl-based covalent organic framework material of Example 1 of this invention. Figure 2 It can be seen that the obtained hierarchical porous alkenyl covalent organic framework material HVCOF-TMTPA has a good crystal form.

[0090] like Figure 3 The image shown is a scanning electron microscope image of the hierarchical porous alkenyl covalent organic framework material bulk of Example 1 of the present invention. The obtained hierarchical porous alkenyl covalent organic framework material HVCOF-TMTPA bulk has regular macropores with a macropore size of 300 nm.

[0091] like Figure 4 The image shown is a transmission electron microscope (TEM) image of the interior of the hierarchical porous alkenyl covalent organic framework material of Example 1 of the present invention. The obtained hierarchical porous alkenyl covalent organic framework material HVCOF-TMTPA also has a regularly arranged and interconnected macroporous structure.

[0092] Scanning electron microscopy (SEM) images reveal regular voids on the surface of the alkenyl covalent organic framework material with hierarchical pores obtained in this invention. Transmission electron microscopy (TEM) also shows that the morphology of the voids inside the alkenyl covalent organic framework material with hierarchical pores is regular. This indicates that these regular voids are not only present on the surface of the alkenyl covalent organic framework material with hierarchical pores, but are present throughout the entire alkenyl covalent organic framework material with hierarchical pores. This demonstrates that the alkenyl covalent organic framework material with hierarchical pores obtained in this invention has a stable hierarchical pore structure.

[0093] Example 2:

[0094] Step S100: Prepare silica microspheres with a close-packed structure, wherein each silica microsphere has the same order of magnitude.

[0095] In this embodiment of the invention, the steps for preparing the microsphere solid with the close-packed structure include:

[0096] Step S101: 300 mg of silica microspheres with a particle size of 500 nm are dispersed in 3 mL of methanol solvent and ultrasonically treated for 20 min to obtain a silica microsphere suspension.

[0097] In step S102, the silica microsphere suspension is transferred to a reaction vessel and placed in a centrifuge for sedimentation. The centrifuge is centrifuged at a rate of 7000 r / min for 5 min, so that the silica microspheres settle to the bottom of the reaction vessel.

[0098] In step S103, excess methanol solvent in the reaction vessel after sedimentation is first removed, and then the reaction vessel is placed in an oven and dried at 70°C for 30 minutes to completely remove the methanol solution and obtain dry silica microspheres with a close-packed structure.

[0099] In step S200, 62 mg of 2,4,6-trimethyl-1,3,5-triazine, 101 mg of terephthalaldehyde, and 200 mg of benzoic anhydride as a catalyst are added to a reaction vessel containing the silica microsphere solids. The reaction vessel is then sealed and subjected to vacuum treatment.

[0100] Step S300: The reaction vessel after vacuum treatment is preheated and then continuously heated. The preheating temperature is 120°C and the preheating time is 3 hours. Then, it is continuously heated at 200°C for 3 days, so that the ligands of the covalent organic framework form a molten state and are immersed in the gaps between the silica microspheres, gradually polymerizing and crystallizing to obtain a silica microsphere solid-covalent organic framework composite.

[0101] Step S400: The silica microsphere solid-covalent organic framework composite is prepared into silica microsphere solid-covalent organic framework composite powder by grinding.

[0102] In this embodiment of the invention, the ligands of the covalent organic framework, which are ground into powder, are washed with methanol solution using a Soxhlet extractor and then dried in an oven at 80°C for 12 hours to obtain silica microsphere solid-covalent organic framework composite powder.

[0103] In step S500, 10 mL of 10% hydrofluoric acid is added to the silica microsphere solid-covalent organic framework composite powder and stirred for 12 h to remove the silica microsphere solid in the silica microsphere solid-covalent organic framework composite and form voids, finally obtaining an alkenyl covalent organic framework material with a hierarchical pore structure.

[0104] In this embodiment of the invention, the silica microsphere solid-covalent organic framework composite powder etched with hydrofluoric acid is washed with 30 mL of methanol and 30 mL of tetrahydrofuran, and then dried in an oven at 80 °C for 12 h to finally obtain an alkenyl covalent organic framework material with a hierarchical pore structure.

[0105] like Figure 5 The image shown is the XRD pattern of the hierarchical porous alkenyl covalent organic framework material of Example 2 of the present invention. Figure 5 It can be seen that the obtained hierarchical porous alkenyl covalent organic framework material HVCOF-TMTPA has a good crystal form.

[0106] like Figure 6 The image shown is a scanning electron microscope image of the hierarchical porous alkenyl covalent organic framework material block of Example 2 of the present invention. The obtained hierarchical porous alkenyl covalent organic framework material block has regular macropores with a macropore size of 500 nm.

[0107] Example 3:

[0108] Step S100: Prepare silica microspheres with a close-packed structure, wherein each silica microsphere has the same order of magnitude.

[0109] In this embodiment of the invention, the steps for preparing the microsphere solid with the close-packed structure include:

[0110] Step S101: 300 mg of silica microspheres with a particle size of 300 nm are dispersed in 3 mL of methanol solvent and ultrasonically treated for 20 min to obtain a silica microsphere suspension.

[0111] In step S102, the silica microsphere suspension is transferred to a reaction vessel and placed in a centrifuge for sedimentation. The centrifuge is centrifuged at a rate of 7000 r / min for 5 min, so that the silica microspheres settle to the bottom of the reaction vessel.

[0112] In step S103, excess methanol solvent in the reaction vessel after sedimentation is first removed, and then the reaction vessel is placed in an oven and dried at 70°C for 30 minutes to completely remove the methanol solution and obtain dry silica microspheres with a close-packed structure.

[0113] In step S200, 60 mg of 2,4,6-trimethyl-1,3,5-triazine, 101 mg of terephthalaldehyde, and 200 mg of benzoic anhydride as a catalyst are added to a reaction vessel containing the silica microsphere solids. The reaction vessel is then sealed and subjected to vacuum treatment.

[0114] Step S300: The reaction vessel after vacuum treatment is preheated and then continuously heated. The preheating temperature is 120°C and the preheating time is 3 hours. Then, it is continuously heated at 200°C for 3 days, so that the ligands of the covalent organic framework form a molten state and are immersed in the gaps between the silica microspheres, gradually polymerizing and crystallizing to obtain a silica microsphere solid-covalent organic framework composite.

[0115] Step S400: The silica microsphere solid-covalent organic framework composite is prepared into silica microsphere solid-covalent organic framework composite powder by grinding.

[0116] In this embodiment of the invention, the ligands of the covalent organic framework, which are ground into powder, are washed with methanol solution using a Soxhlet extractor and then dried in an oven at 80°C for 12 hours to obtain silica microsphere solid-covalent organic framework composite powder.

[0117] In step S500, 10 mL of 10% hydrofluoric acid is added to the silica microsphere solid-covalent organic framework composite powder and stirred for 12 h to remove the silica microsphere solid in the silica microsphere solid-covalent organic framework composite and form voids, finally obtaining an alkenyl covalent organic framework material with a hierarchical pore structure.

[0118] In this embodiment of the invention, the silica microsphere solid-covalent organic framework composite powder etched with hydrofluoric acid is washed with 30 mL of methanol and 30 mL of tetrahydrofuran, and then dried in an oven at 80 °C for 12 h to finally obtain an alkenyl covalent organic framework material with a hierarchical pore structure.

[0119] like Figure 7 The image shown is the XRD pattern of the hierarchical porous alkenyl covalent organic framework material of Example 3 of the present invention. Figure 7 It can be seen that the obtained hierarchical porous alkenyl covalent organic framework material has a good crystal form.

[0120] Comparative Example 1:

[0121] A method for preparing an alkenyl covalent organic framework material includes:

[0122] Step S10: 62 mg of 2,4,6-trimethyl-1,3,5-triazine, 101 mg of terephthalaldehyde, and 200 mg of benzoic anhydride are added to the reaction vessel as catalysts. The reaction vessel is then evacuated and sealed.

[0123] Step S20: The vacuum-sealed reaction vessel is placed in an oven and heated at 200°C for 3 days to obtain a solid product.

[0124] Step S30: Grind the solid product into powder;

[0125] Step S40: The powder is washed with methanol solution using a Soxhlet extractor, and the washed powder is placed in an oven and dried at 80°C for 12 hours to obtain the alkenyl covalent organic framework material VCOF-TMTPA.

[0126] Comparative Example 1: An alkenyl covalent organic framework material prepared by a method does not possess hierarchical pores; the alkenyl covalent organic framework material is an irregular bulk material.

[0127] Figure 8 This is a schematic diagram of the photocatalytic hydrogen evolution kinetic curves of the alkenyl covalent organic framework materials obtained by the preparation method of alkenyl covalent organic framework materials in Example 1 and Comparative Example 1 of the present invention. Figure 8 It can be seen that the photocatalytic performance of the HVCOF-TMTPA with hierarchical pore structure obtained in Example 1 of the present invention is significantly higher than that of the VCOF-TMTPA without hierarchical pore structure obtained in Comparative Example 1.

[0128] The comparison between Example 1 and Comparative Example 1 demonstrates that HVCOF-TMTPA with hierarchical pores exhibits better photocatalytic performance than COF without hierarchical pore structure, illustrating the significant advantages of the alkenyl covalent organic framework material described in this invention in photocatalysis.

[0129] This invention also provides a hierarchical porous alkenyl covalent organic framework material, prepared according to any one of the above preparation methods.

[0130] This invention also provides an application of a graded porous alkenyl covalent organic framework material as described above in the photocatalytic hydrogen evolution reaction.

[0131] In other embodiments, the hierarchical porous alkenyl covalent organic framework material is used in photoelectrocatalysis, pollutant adsorption and degradation, batteries, and sensing.

[0132] Finally, it should be noted that any modification or equivalent substitution of some or all of the technical features based on the device structure and the technical solutions of the embodiments of the present invention, without departing from the corresponding technical solutions of the present invention, shall fall within the patent scope of the device structure and the embodiments of the present invention.

Claims

1. A method for preparing a hierarchical porous alkenyl-based covalent organic framework material, characterized in that, include: Close-packed microspheres were prepared by centrifugal sedimentation. A covalent organic framework ligand and a catalyst are added to a reaction vessel containing the microsphere solid, and the reaction vessel is then sealed and vacuum-treated. The covalent organic framework ligand has micropores, and the size of the microsphere is larger than the size of the micropore. The covalent organic framework ligand is 2,4,6-trimethyl-1,3,5-triazine and terephthalaldehyde. The reaction vessel, after being vacuum treated, is first preheated and then continuously heated. The preheating causes the ligands of the covalent organic framework to form a molten state and immerse themselves in the gaps between the microspheres. The continuous heating then causes the ligands of the covalent organic framework to gradually polymerize and crystallize, thereby obtaining a microsphere solid-covalent organic framework complex. An etchant is added to the microsphere solid-covalent organic framework composite to remove the microsphere solid and form pores, thereby obtaining an alkenyl covalent organic framework material with a hierarchical pore structure. The step of preparing the microsphere solid with a close-packed structure includes: uniformly dispersing microspheres of the same order of magnitude size in a first solvent to obtain a microsphere suspension; centrifuging the microsphere suspension; and removing excess first solvent after centrifugation to obtain a dry, close-packed microsphere solid. The particle size range of the microspheres is 100 nm-1000 nm, and the microspheres are silica microspheres.

2. The method for preparing a hierarchical porous alkenyl covalent organic framework material as described in claim 1, characterized in that, The first solvent includes one of methanol, ethanol, acetone, and tetrahydrofuran.

3. The method for preparing a hierarchical porous alkenyl covalent organic framework material as described in claim 1, characterized in that, The catalyst includes either benzoic anhydride or benzoic acid.

4. The method for preparing a hierarchical porous alkenyl covalent organic framework material as described in claim 1, characterized in that, The reaction vessel is preheated and continuously heated in an oven. The preheating temperature range is 50℃-130℃, and the preheating time range is 5min-30min. The continuous heating temperature range is 160℃-220℃, and the continuous heating time range is 2 days-7 days.

5. The method for preparing a hierarchical porous alkenyl covalent organic framework material as described in claim 1, characterized in that, The etching agent includes one of hydrofluoric acid, ammonium fluoride solution, and strong alkaline solution, wherein the strong alkaline solution includes one of potassium hydroxide aqueous solution, sodium hydroxide aqueous solution, and lithium hydroxide aqueous solution.

6. The method for preparing a hierarchical porous alkenyl covalent organic framework material as described in claim 1, characterized in that, Also includes: The microsphere solid-covalent organic framework composite is ground into covalent organic framework composite powder, and then the microsphere solid in the microsphere solid-covalent organic framework composite powder is removed by an etchant to form pores.

7. The method for preparing a hierarchical porous alkenyl covalent organic framework material as described in claim 1, characterized in that, Before obtaining the microsphere solid-covalent organic framework complex, the ligands of the crystallized covalent organic framework are further subjected to a second washing and a second drying. The second washing agent includes one of methanol and ethanol, and the second washing method includes one of Soxhlet extraction washing and filtration washing. The temperature range of the second drying is 60℃-120℃.

8. The method for preparing a hierarchical porous alkenyl covalent organic framework material as described in claim 1, characterized in that, The pore size range includes macropores, mesopores, and micropores, wherein the macropore diameter ranges from 100nm to 500nm, the mesopore diameter ranges from 2nm to 3nm, and the micropore diameter ranges from 1nm to 2nm.

9. A hierarchical porous alkenyl-based covalent organic framework material, characterized in that, Prepared by the preparation method according to any one of claims 1 to 8.

10. The application of a hierarchical porous alkenyl covalent organic framework material as described in claim 9 in the photocatalytic hydrogen evolution reaction.

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