Method for green and rapid preparation of covalent organic framework nanosheets based on single-water phase and application thereof
By introducing alkaline auxiliaries through a single-aqueous phase method to regulate the synthesis of covalent organic framework nanosheets, the problems of low efficiency and environmental unfriendliness of traditional methods have been solved. This has enabled the rapid preparation and large-scale production of highly crystalline nanosheets, which can be applied to the construction of high-performance separation membranes.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HAINAN UNIV
- Filing Date
- 2026-04-03
- Publication Date
- 2026-06-30
AI Technical Summary
Existing technologies struggle to rapidly and environmentally prepare highly crystalline covalent organic framework nanosheets at room temperature and pressure. Furthermore, traditional methods are inefficient, environmentally unfriendly, and difficult to scale up.
A single-phase aqueous method was used to introduce alkaline additives to construct an alkaline aqueous homogeneous reaction system. By controlling the monomer dissolution and polymerization kinetics through alkaline additives, the rapid synthesis of covalent organic framework nanosheets was achieved. The obtained nanosheets exhibited good dispersibility and high crystallinity.
Highly crystalline COF nanosheets were efficiently and rapidly prepared under ambient temperature and pressure, exhibiting excellent solution processing performance and scalable production. The prepared nanosheets were used to construct high-performance separation membranes, demonstrating high pure water flux and high rejection rate.
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Figure CN122302308A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of porous two-dimensional materials, and specifically relates to a method for the rapid preparation of covalent organic framework nanosheets based on a single aqueous phase, and the application of the thin film formed therefrom in dye separation. Background Technology
[0002] Covalent organic frameworks (COFs), as a new class of crystalline porous organic polymers, have shown broad application prospects in gas adsorption and separation, sensing, catalysis, energy storage, and membrane separation due to their inherent regular pore structure, high specific surface area, excellent chemical and thermal stability, and pre-designable framework and pore functions. Processing COFs into nanosheet morphology can further expose their active sites, shorten mass transfer pathways, and endow them with excellent solution processing properties, which is of great significance for promoting the practical application of COFs.
[0003] However, the controllable preparation of COF nanosheets still faces significant challenges. COF synthesized by traditional solvothermal methods is usually an insoluble and infusible microcrystalline powder, making it difficult to directly exfoliate to obtain high-quality nanosheets. To address this issue, researchers have developed various strategies such as interfacial synthesis, mechanical exfoliation, and chemical exfoliation. However, existing methods generally suffer from the following shortcomings: (1) they rely on organic solvents or high-temperature and high-pressure conditions, resulting in high energy consumption and environmental unfriendliness; (2) the synthesis cycle is long, usually requiring several hours to several days, leading to low efficiency; (3) the reaction process is difficult to control, resulting in nanosheets with low crystallinity or non-uniform size; and (4) they are difficult to scale up, limiting them to the laboratory research stage. These problems have led to a long-standing contradiction between "high performance" and "green manufacturing," "precise structure" and "rapid preparation," and "excellent samples" and "large-scale preparation," severely restricting the further application of COF nanosheets.
[0004] Therefore, developing a simple, mild, environmentally friendly, and rapid method for preparing highly crystalline COF nanosheets is of significant scientific and practical value. Summary of the Invention
[0005] To address the shortcomings of existing technologies, this invention aims to provide a simple and rapid method for preparing covalent organic framework nanosheets using a single aqueous phase approach. This invention constructs an alkaline aqueous homogeneous reaction system by introducing an alkaline auxiliary agent. Utilizing the synergistic regulatory effect of the alkaline auxiliary agent on monomer dissolution and polymerization kinetics, highly crystalline COF nanosheets are rapidly synthesized under ambient temperature and pressure aqueous phase conditions. The resulting nanosheets exhibit good dispersibility, high crystallinity, and excellent solution processing properties.
[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for rapid, green preparation of covalent organic framework nanosheets based on a single aqueous phase includes the following steps: Step 1: Weigh a certain amount of alkaline additive, add a certain amount of deionized water, and dissolve by sonication to obtain an aqueous solution of alkaline additive, denoted as solution A; Step 2: Weigh a certain amount of aldehyde monomer, mix it with solution A, and sonicate until completely dissolved. This solution is then called solution B. Step 3: Weigh a certain amount of amine monomer, add a certain amount of deionized water, and sonicate until completely dissolved. Record this as solution C. Step 4: Under stirring conditions, mix solution C with solution B and continue stirring to allow them to react fully, to obtain a homogeneous dispersion of covalent organic framework nanosheets, denoted as solution D; Furthermore, the alkaline auxiliary agent is at least one of an organic base or an inorganic base.
[0007] Furthermore, the organic base is selected from at least one of 2-methylimidazole, 2-ethylimidazole, 2-propylimidazole, diethylamine, triethylamine, pyridine, 4-dimethylaminopyridine, piperazine, piperidine, pyrrolidine, 1-methylpyrrolidine, 2-methylpyrrolidine, sodium formate, sodium oxalate, sodium acetate, potassium oxalate, and potassium acetate.
[0008] Furthermore, the inorganic base is selected from at least one of sodium carbonate, sodium bicarbonate, sodium phosphate, disodium hydrogen phosphate, sodium sulfite, sodium hydroxide, potassium hydroxide, potassium carbonate, potassium bicarbonate, potassium phosphate, lithium carbonate, lithium phosphate, and ammonia water.
[0009] Further, the aldehyde monomer includes pyromellitic methyl methacrylate, 2-hydroxy-1,3,5-benzenetriformaldehyde, 1,3-dihydroxy-2,4,6-trialdehydebenzene, trialdehyde-resorcinol, 1,3,5-tris(p-formylphenyl)benzene, 3,4',5-trialdehyde-1,1-biphenyl, 1,3,5-tris(3'-aldehyde-4'-hydroxybenzene)benzene, 5'-(4-formyl-3-hydroxyphenyl)-3,3''-dihydroxy-[1,1':3',1''-triphenyl]-4,4''-diformaldehyde, 2,5-dihydroxyterephthalaldehyde, 2,3-dihydroxyterephthalaldehyde, 2,5-diformylphenol, 3 At least one of 3'-dihydroxy-[1,1'-biphenyl]-4,4'-dicarboxaldehyde, 4,4'-biphenyldicarboxaldehyde, 5-hydroxy-isophthalaldehyde, 2-hydroxy-isophthalaldehyde, 4-hydroxy-isophthalaldehyde, 4,6-dihydroxy-5-methyl-1,3-dicarboxyphenyl, 5-tert-butyl-4-hydroxyphenyl-1,3-dicarboxaldehyde, 2-methoxy-4,6-dialdehyde phenol, 2,4-dihydroxy-isophthalaldehyde, 2-hydroxy-5-methoxy-1,4-benzenedialdehyde, 2,4,6-trihydroxy-isophthalaldehyde, 2,5-dihydroxy-isophthalaldehyde, and 4,5,6-trihydroxy-1,3-benzenedialdehyde.
[0010] Furthermore, the amine monomer includes at least one of p-phenylenediamine, m-phenylenediamine, triaminoguanidine hydrochloride, 2,5-diaminotoluene, p-phenylenediamine sulfonic acid, p-phenylenediamine-2,5-disulfonic acid, 4,4'-diamino-3,3'-biphenyl disulfonic acid and 2,2'-disulfonic acid benzidine, 2,4,6-triaminophloroglucinol, 1,3,5-triaminobenzene trihydrochloride, 1,3,5-phenyltrimethylamine hydrochloride, 1,3,5-phenyltrimethylamine, (2,4,6-trimethoxybenzene-1,3,5-triyl)trimethylamine, (2,4,6-trimethoxybenzene-1,3,5-triyl)trimethylamine, and 2,4,6-trimethyl-1,3,5-phenyltrimethylamine.
[0011] Furthermore, the concentration of the alkaline auxiliary agent in the alkaline aqueous solution in step 1 is 0.01 mol / L to 10 mol / L; the molar ratio of the aldehyde monomer to the amine monomer in step 4 is 1:0.67 to 1.5.
[0012] Furthermore, the stirring reaction described in step 4 is carried out at room temperature and pressure, with a reaction time of 0.1–24 hours and a stirring speed of 100–1200 r / min. -1 .
[0013] An application of covalent organic framework nanosheets, using covalent organic framework nanosheets prepared by any of the methods described above as membrane building units to construct nanofiltration membranes for water treatment.
[0014] Furthermore, the nanofiltration membrane prepared from nanosheets exhibited a pure water flux of 305 L / m³ at 25 °C and 2 bar. -2 h -1 bar -1 The rejection rates for Chrome Black T, Alixin Blue 8GX, Direct Red 80, Congo Red, and Direct Black 19 were all above 99%.
[0015] Compared with the prior art, the beneficial effects of the present invention are: This invention, based on a novel paradigm of "single-phase aqueous homogeneous reaction," fundamentally overturns the traditional technical route of COF material synthesis relying on multiphase interfaces. By introducing alkaline auxiliaries to precisely control the dissolution and polymerization processes, it resolves the core contradictions that have long existed between "high performance" and "green manufacturing," "precise structure" and "rapid preparation," and "excellent samples" and "large-scale preparation." Its beneficial effects include achieving, for the first time, an order-of-magnitude increase in synthesis speed in a pure aqueous system; the prepared COF nanosheets possess both high crystallinity and excellent dispersibility, while also exhibiting comprehensive technical advantages of being "fast, good, and economical": synthesis time is shortened to the minute level, reaction conditions are mild (room temperature and pressure), no organic solvents are required, and green chemistry principles are applied from the outset; the resulting nanosheets have high crystallinity, uniform size, and excellent solution processing performance; the method is simple to operate, low in cost, and verifies the feasibility of high-concentration, large-volume synthesis, breaking through the bottleneck of large-scale preparation. Furthermore, this invention clarifies the regulatory mechanism of alkaline auxiliaries on the crystallization process in a homogeneous aqueous system, providing not only a scalable green synthesis methodology for high-performance COF nanosheets but also demonstrating the universal potential of this paradigm in the preparation of crystalline organic nanomaterials. Using the COF nanosheets prepared by this invention as building blocks, high-performance separation membranes can be further fabricated via vacuum-assisted self-assembly. The resulting membrane material exhibits a pure water flux of up to 305 L / m³ at an operating pressure of 2 bar. -2 h -1 bar -1 It achieves a retention rate of over 99% for various dye molecules, demonstrating promising application prospects. Attached Figure Description
[0016] Figure 1 This is a digital photograph of the covalent organic framework nanosheet dispersion prepared in Example 1 of the present invention.
[0017] Figure 2 This is a scanning electron microscope image of the covalent organic framework nanosheets prepared in Example 1 of the present invention.
[0018] Figure 3 An atomic force microscope image of the covalent organic framework nanosheets prepared in Example 1 of this invention.
[0019] Figure 4 The X-ray diffraction pattern is shown for the covalent organic framework nanosheets prepared in Example 1 of this invention.
[0020] Figure 5 This is a nanofiltration performance diagram of the covalent organic framework nanosheet membrane prepared in Example 1 of the present invention.
[0021] Figure 6 This is a digital photograph of the covalent organic framework nanosheet dispersion prepared in a magnified embodiment of the present invention. Detailed Implementation
[0022] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are for illustrative purposes only and should not be considered as any limitation on the present invention.
[0023] Example 1
[0024] This embodiment presents a method for the green and rapid preparation of covalent organic framework nanosheets based on a single aqueous phase method, comprising the following steps: Step 1: Weigh 240 mg of 2-methylimidazole and dissolve it in 10 mL of deionized water by sonication to obtain solution A; wherein the sonication time is 10 min.
[0025] Step 2: Weigh 63 mg of trialdehyde phloroglucinol, mix it with solution A, and dissolve it by sonication to obtain solution B; wherein the sonication time is 10 min.
[0026] Step 3: Weigh 49 mg of p-phenylenediamine and dissolve it in 20 mL of deionized water by sonication to obtain solution C; wherein the sonication time is 10 min.
[0027] Step 4: Mix solution B with solution C and incubate at 1200 rpm at room temperature. -1 After stirring for 6 min, a solution of highly crystalline covalent organic framework nanosheets was obtained, denoted as solution D. Figure 1 As shown.
[0028] The covalent organic framework nanosheets prepared in this embodiment were characterized: the resulting dispersion exhibited a uniform colloidal state (e.g., Figure 1 As shown); scanning electron microscopy and atomic force microscopy revealed that it has a nanosheet morphology with a thickness of approximately 2.32 nm (as shown). Figure 2 , Figure 3 As shown); X-ray diffraction patterns show that it has good crystallinity (e.g. Figure 4 (As shown).
[0029] Application Example 1 0.65 mL of solution D prepared in Example 1 was deposited onto the surface of a polyacrylonitrile ultrafiltration membrane using a vacuum-assisted self-assembly method. After drying, a covalent organic framework membrane was obtained. Its separation performance was tested at 25°C and 2 bar. The results showed that the pure water flux of this membrane was 305 L / m³. -2 h -1 bar -1 The retention rates of five dye molecules—Chrome Black T, Alcian Blue 8GX, Direct Red 80, Congo Red, and Direct Black 19—all reached over 99%.
[0030] Step 5: Take 0.65 mL of solution D and deposit the dispersion onto the surface of the porous support membrane using a vacuum-assisted self-assembly method to obtain a covalent organic framework membrane.
[0031] The pure water flux and the rejection rates of dye molecules such as Chrome Black T, Alcian Blue 8GX, Direct Red 80, Congo Red, and Direct Black 19 were tested under conditions of 25 °C and 2 bar. The pure water flux was 305 L / m³. - 2 h -1 bar -1 The rejection rates for Chrome Black T, Alixin Blue 8GX, Direct Red 80, Congo Red, and Direct Black 19 were all above 99%.
[0032] Example 2
[0033] Step 1: Weigh 322 mg of 2-propylimidazole and dissolve it in 10 mL of deionized water by sonication to obtain solution A; wherein the sonication time is 10 min.
[0034] Step 2: Weigh 63 mg of trialdehyde phloroglucinol, mix it with solution A, and dissolve it by sonication to obtain solution B; wherein the sonication time is 10 min.
[0035] Step 3: Weigh 49 mg of p-phenylenediamine and dissolve it in 20 mL of deionized water by sonication to obtain solution C; wherein the sonication time is 10 min.
[0036] Step 4: Mix solution B with solution C and incubate at room temperature for 100 rpm. -1 Stirring for 24 h yielded a solution of highly crystalline covalent organic framework nanosheets, denoted as solution D.
[0037] Application Example 2 0.65 mL of solution D prepared in Example 2 was deposited onto the surface of a polyacrylonitrile ultrafiltration membrane using a vacuum-assisted self-assembly method. After drying, a covalent organic framework membrane was obtained. Its separation performance was tested at 25°C and 2 bar. The results showed that the pure water flux of the membrane was 283.18 L / m³. -2 h -1 bar -1 The retention rates of five dye molecules—Chrome Black T, Alcian Blue 8GX, Direct Red 80, Congo Red, and Direct Black 19—all reached over 99%.
[0038] Step 5: Take 0.65 mL of solution D and deposit the dispersion onto the surface of the porous support membrane using a vacuum-assisted self-assembly method to obtain a covalent organic framework membrane.
[0039] The pure water flux and the rejection rates of dye molecules such as Chrome Black T, Alcian Blue 8GX, Direct Red 80, Congo Red, and Direct Black 19 were measured under the conditions of 25 °C and 2 bar. The pure water flux was 283.18 Lm. -2 h -1 bar -1 The rejection rates for Chrome Black T, Alixin Blue 8GX, Direct Red 80, Congo Red, and Direct Black 19 were all above 99%.
[0040] Scaled-up example
[0041] Step 1: Weigh 64.37g of methylimidazole and dissolve it in 2.7L of deionized water by sonication to obtain solution A; wherein the sonication time is 10 min.
[0042] Step 2: Weigh 16.38 g of trialdehyde phloroglucinol, mix it with solution A, and dissolve it by sonication to obtain solution B; wherein the sonication time is 10 min.
[0043] Step 3: Weigh 12.74 g of p-phenylenediamine and dissolve it in 5.3 L of deionized water by sonication to obtain solution C; wherein the sonication time is 10 min.
[0044] Step 4: Mix solution B with solution C and incubate at room temperature for 1000 rpm. -1 Stir for 10 min to obtain a solution of highly crystalline covalent organic framework nanosheets (8 L), denoted as solution D.
[0045] The covalent organic framework nanosheet dispersions prepared in the scaled-up examples exhibited a uniform colloidal state and displayed a significant Tyndall effect (e.g., Figure 6 (As shown).
[0046] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art can make various improvements and modifications without departing from the spirit and principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for rapid, green preparation of covalent organic framework nanosheets based on a single aqueous phase, characterized in that, Includes the following steps: Step 1: Weigh a certain amount of alkaline additive, add a certain amount of deionized water, and dissolve by sonication to obtain an aqueous solution of alkaline additive, denoted as solution A; Step 2: Weigh a certain amount of aldehyde monomer, mix it with solution A, and sonicate until completely dissolved. This solution is then called solution B. Step 3: Weigh a certain amount of amine monomer, add a certain amount of deionized water, and sonicate until completely dissolved. Record this as solution C. Step 4: Under stirring conditions, mix solution C with solution B and continue stirring to allow them to react fully, resulting in a homogeneous dispersion of covalent organic framework nanosheets, denoted as solution D.
2. The method according to claim 1, characterized in that, The alkaline additive is at least one of an organic base or an inorganic base.
3. The method according to claim 2, characterized in that, The organic base is selected from at least one of 2-methylimidazolium, 2-ethylimidazolium, 2-propylimidazolium, diethylamine, triethylamine, pyridine, 4-dimethylaminopyridine, piperazine, piperidine, pyrrolidine, 1-methylpyrrolidine, 2-methylpyrrolidine, sodium formate, sodium oxalate, sodium acetate, potassium oxalate, and potassium acetate.
4. The method according to claim 1, characterized in that, The inorganic base is selected from at least one of sodium carbonate, sodium bicarbonate, sodium phosphate, disodium hydrogen phosphate, sodium sulfite, sodium hydroxide, potassium hydroxide, potassium carbonate, potassium bicarbonate, potassium phosphate, lithium carbonate, lithium phosphate, and ammonia water.
5. The method according to claim 1, characterized in that, The aldehyde monomers include pyromellitic methyl methacrylate (PMMA), 2-hydroxy-1,3,5-phenyltrimethyl methyl methacrylate (PMMA), 1,3-dihydroxy-2,4,6-trialdehydebenzene, trialdehyde-phloroglucinol, 1,3,5-tris(p-formylphenyl)benzene, 3,4',5-trialdehyde-1,1-biphenyl, 1,3,5-tris(3'-aldehyde-4'-hydroxybenzene)benzene, 5'-(4-formyl-3-hydroxyphenyl)-3,3''-dihydroxy-[1,1':3',1''-triphenyl]-4,4''-dicarboxaldehyde, 2,5-dihydroxy-terephthalaldehyde, 2,3-dihydroxy-terephthalaldehyde, 2,5-diformylphenol, and 3,3'-dihydroxy-[1,1'-biphenyl]. At least one of the following: -4,4'-dicarboxaldehyde, 4,4'-biphenylcarboxaldehyde, 5-hydroxy-isophthalaldehyde, 2-hydroxy-isophthalaldehyde, 4-hydroxy-isophthalaldehyde, 4,6-dihydroxy-5-methyl-1,3-dicarboxyphenyl, 5-tert-butyl-4-hydroxybenzene-1,3-dicarboxaldehyde, 2-methoxy-4,6-dialdehyde-phenol, 2,4-dihydroxy-isophthalaldehyde, 2-hydroxy-5-methoxy-1,4-phenylcarboxaldehyde, 2,4,6-trihydroxy-isophthalaldehyde, 2,5-dihydroxy-isophthalaldehyde, and 4,5,6-trihydroxy-1,3-phenylcarboxaldehyde.
6. The method according to claim 1, characterized in that, The amine monomers include at least one of p-phenylenediamine, m-phenylenediamine, triaminoguanidine hydrochloride, 2,5-diaminotoluene, p-phenylenediamine sulfonic acid, p-phenylenediamine-2,5-disulfonic acid, 4,4'-diamino-3,3'-biphenyl disulfonic acid and 2,2'-disulfonic acid benzidine, 2,4,6-triaminophloroglucinol, 1,3,5-triaminobenzene trihydrochloride, 1,3,5-phenyltrimethylamine hydrochloride, 1,3,5-phenyltrimethylamine, (2,4,6-trimethoxybenzene-1,3,5-triyl)trimethylamine, (2,4,6-trimethoxybenzene-1,3,5-triyl)trimethylamine, and 2,4,6-trimethyl-1,3,5-phenyltrimethylamine.
7. The method according to claim 1. Characterized by, characterized in that, The concentration of the alkaline auxiliary agent in the alkaline aqueous solution in step 1 is 0.01 mol / L to 10 mol / L; the molar ratio of the aldehyde monomer to the amine monomer in step 4 is 1:0.67 to 1.
5.
8. The method according to claim 1, characterized in that, The stirring reaction described in step 4 is carried out at room temperature and pressure for a reaction time of 0.1–24 hours and a stirring speed of 100–1200 r / min. -1 .
9. An application of a covalent organic framework nanosheet, characterized in that, Using covalent organic framework nanosheets prepared according to any one of claims 1-8 as membrane building units, a nanofiltration membrane for water treatment is constructed.
10. The application according to claim 9, characterized in that: The nanofiltration membrane prepared from nanosheets exhibited a pure water flux of 305 L / m³ at 25°C and 2 bar. -2 h -1 bar -1 The rejection rates for Chrome Black T, Alixin Blue 8GX, Direct Red 80, Congo Red, and Direct Black 19 were all above 99%.