A porous covalent organic framework oil storage microcapsule and a preparation method and application thereof

Abstract

The present application relates to the field of oil storage microcapsules, and discloses a porous covalent organic framework oil storage microcapsule and a preparation method and application thereof. The present application promotes condensation reaction of 4,4',4''-(1,3,5-triazine-2,4,6-triazinyl) triphenylamine and tri-aldehyde phloroglucinol monomers in a repeated shaking process under catalysis of p-toluenesulfonic acid, and 4,4',4''-(1,3,5-triazine-2,4,6-triazinyl) triphenylamine covalent organic framework is prepared after purification of the product. The periodic pore structure of the covalent organic framework is used to adsorb and store lubricating oil, and the lubricating oil can be controlled to be released to provide lubrication during work, so that high-performance self-lubricating effect can be realized. In addition, the covalent organic framework is doped into a polymer matrix as a hard particle to modify the polymer matrix, which can greatly enhance the wear resistance of the polymer matrix, thereby improving the performance of the self-lubricating bearing material.

Description

Technical Field

[0001] This invention relates to the field of oil storage microcapsules, and particularly to a porous covalent organic framework oil storage microcapsule, its preparation method, and its application. Background Technology

[0002] Self-lubricating bearings, also known as oil-free bearings, are sliding bearings that do not require additional lubricant during operation. They possess numerous advantages, including high load-bearing capacity, high-temperature resistance, maintenance-free operation, and low coefficient of friction, making them particularly suitable for the extreme working conditions faced by heavy machinery in aerospace equipment and deep-sea vessels. Oil-storing microcapsules, a newly emerging type of self-lubricating material in recent years, store lubricant through their porous structure when not in operation. During operation, under the stimulation of friction, they release lubricating oil to provide lubrication. This approach leverages both the lubricating efficiency of the internally stored lubricant and the load-bearing advantages of solid materials, offering advantages such as strong environmental adaptability and wide application range. It is a crucial solution for the development of high-end self-lubricating bearings. Currently reported oil-storing microcapsules are mostly hollow carbon spheres or core-shell silicon spheres, possessing only a single channel for storing lubricating oil. Once the outer shell ruptures, the internal lubricating oil leaks out uncontrollably, failing to provide a continuous and stable lubrication supply. This significantly impacts the use of self-lubricating bearing materials, failing to guarantee stable lubrication performance and greatly reducing equipment lifespan.

[0003] It is evident that existing technologies still need improvement and enhancement. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a porous covalent organic framework oil storage microcapsule, its preparation method and application. By using the prepared covalent organic framework as a microcapsule to store lubricating oil, and doping it into a polymer to enhance and modify it, on the one hand, the periodic pore structure of the covalent organic framework can be used to adsorb and store the lubricating oil, and it can be controlled to precipitate and provide lubrication during operation, thus achieving a high-performance self-lubricating effect; on the other hand, the covalent organic framework, as a hard particle, can be doped into the polymer matrix to modify it, which can greatly enhance its wear resistance and improve the performance stability of the self-lubricating bearing material.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for preparing porous covalent organic framework oil-storing microcapsules includes the following steps:

[0007] S1. Weigh 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine and p-toluenesulfonic acid and add them to water, mix well; add trialdehyde phloroglucinol to the well mixed solution, and shake the resulting solution repeatedly to achieve the preliminary synthesis of covalent organic framework;

[0008] S2. Heating and drying the mixed solution promotes the layer-by-layer stacking of the initially synthesized covalent organic framework to construct a three-dimensional spatial skeleton, thereby realizing the construction of the periodic pore structure of the organic covalent framework and obtaining a solid.

[0009] S3. Remove p-toluenesulfonic acid from the above solid; purify the solid with an organic solvent to obtain a solid product; dry the solid product to obtain 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine covalent organic framework powder;

[0010] S4. Mix and impregnate 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine covalent organic framework powder with an excess of lubricating oil; remove the residual lubricating oil from the surface of the 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine covalent organic framework powder and then dry it to obtain 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine covalent organic framework oil storage microcapsules.

[0011] The method for preparing the porous covalent organic framework oil storage microcapsules, wherein step S1 specifically involves: weighing 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine and p-toluenesulfonic acid, adding them to water, stirring and mixing, and then mixing by oscillation in a grinder for 10-20 minutes; adding trialdehyde-resorcinol to the uniformly mixed solution, and then mixing the resulting mixed solution again by oscillation in a grinder for 30-40 minutes.

[0012] The method for preparing the porous covalent organic framework oil-storing microcapsules, wherein in step S1, 0.04–0.08 mmol of 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine is added per milliliter of water; the molar ratio of 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine to p-toluenesulfonic acid is 1:(8–10).

[0013] The method for preparing porous covalent organic framework oil storage microcapsules, wherein in step S1, the molar ratio of 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine to trialdehyde-resorcinol is 1:(0.9-1.1).

[0014] The method for preparing porous covalent organic framework oil-storing microcapsules, wherein step S2 specifically involves: placing the mixed solution in an open container, letting it stand overnight at room temperature to evaporate and remove moisture from the mixed solution; then placing the open container and the mixed solution in an oven at a temperature of 120–140°C to dry for 20–30 hours to obtain a solid with moisture removed.

[0015] The method for preparing porous covalent organic framework oil-storing microcapsules, wherein step S3 specifically involves: rinsing the solid material after removing moisture with a large amount of hot water, and repeatedly vacuum filtering until residual p-toluenesulfonic acid is removed; washing with tetrahydrofuran vacuum filtration to obtain a solid product; and drying the solid product overnight in an oven at 80–90°C to obtain 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine covalent organic framework powder.

[0016] The method for preparing the porous covalent organic framework oil-storing microcapsules, wherein step S4 specifically involves: mixing and impregnating 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine covalent organic framework powder with an excess of lubricating oil to obtain a product; washing and centrifuging the product with methanol and water to remove residual lubricating oil from the surface of the 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine covalent organic framework powder; and drying the product overnight in an oven at 100-120°C to obtain 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine covalent organic framework oil-storing microcapsules.

[0017] A porous covalent organic framework oil-storing microcapsule is prepared by the above-described method for preparing porous covalent organic framework oil-storing microcapsules.

[0018] An application of porous covalent organic framework oil-storing microcapsules involves physically blending the aforementioned porous covalent organic framework oil-storing microcapsules into a polymer substrate to prepare a self-lubricating and reinforced modified polymer composite material of 4,4',4''-(1,3,5-triazine-2,4,6-trimethyl)triphenylamine covalent organic framework oil-storing microcapsules; the polymer substrate includes one of ultra-high molecular weight polyethylene, phenolic resin, polyurethane, and epoxy resin.

[0019] In the application of the porous covalent organic framework oil-storing microcapsules, the mass fraction of the 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine covalent organic framework oil-storing microcapsules in the self-lubricating and reinforcing modified polymer composite material is 0.2-0.8%.

[0020] Beneficial effects:

[0021] This invention provides a porous covalent organic framework for oil storage microcapsules, its preparation method, and its application. The method involves promoting the condensation reaction of 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine and trialdehyde-based phloroglucinol monomers under repeated shaking catalysis with p-toluenesulfonic acid. The product is purified to obtain the 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine covalent organic framework. This framework is used as a microcapsule for storing lubricating oil. It is further enhanced by incorporating it into polymers. On one hand, the periodic pore structure of the covalent organic framework allows for the adsorption and storage of lubricating oil, enabling controlled precipitation during operation to provide lubrication and achieve a high-performance self-lubricating effect. On the other hand, the covalent organic framework, as a hard particle, is incorporated into the polymer matrix to modify its wear resistance. Furthermore, as an all-organic framework structure material, covalent organic frameworks exhibit better compatibility with organic polymer matrices compared to metal-based and silicon-based microcapsules, which is of great advantage for further improving the performance stability of self-lubricating bearing materials. Attached Figure Description

[0022] Figure 1 This is a schematic flowchart of a method for preparing porous covalent organic framework oil-storing microcapsules provided by the present invention.

[0023] Figure 2 The images show the crystallization type, chemical structure, and porosity characteristics of the COF-Tta powder in Example 1.

[0024] Figure 3 This is a schematic diagram illustrating the confirmation of the lubricating oil content in COF-Tta@Oil through thermogravimetric analysis and porosity characterization in Example 1. Detailed Implementation

[0025] This invention provides a porous covalent organic framework oil-storing microcapsule, its preparation method, and its application. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the scope of protection of the invention.

[0026] Please see Figure 1 This invention provides a method for preparing porous covalent organic framework oil-storing microcapsules, comprising the following steps:

[0027] S1. Weigh 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine (Tta) and p-toluenesulfonic acid (PTSA), add them to an appropriate amount of purified water, stir and mix, then mix by oscillation in a grinder for 10-20 minutes. This oscillation mixing method not only achieves physical uniform dispersion but also allows for sufficient contact between Tta and PTSA through mechanical action, ensuring that Tta and PTSA are fully dispersed and uniformly mixed in water. Tta is one of the monomers for synthesizing covalent organic frameworks (COFs), and PTSA acts as a catalyst; a uniform mixing state ensures the smooth progress of subsequent reactions.

[0028] Specifically, the amount of 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine added is 0.04–0.08 mmol per milliliter of water. This amount of Tta ensures uniform dispersion of the reactants in water, preventing localized aggregation due to excessively high Tta concentrations, which could affect the uniformity of subsequent polymerization reactions. If the Tta concentration exceeds this range, Tta may form localized aggregates in water due to solubility limitations, leading to uneven contact with the subsequently added TFP and PTSA catalyst, resulting in incomplete polymerization, incomplete covalent organic framework structures, or crystal defects. Conversely, too low a concentration may reduce reaction efficiency and increase preparation costs. Therefore, this ratio balances dispersion and reaction efficiency.

[0029] Specifically, the molar ratio of 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine to p-toluenesulfonic acid is 1:(8-10). PTSA, as a catalyst for the condensation reaction, directly affects the synthesis efficiency of COF when compared to Tta. Insufficient PTSA leads to incomplete reaction, preventing the formation of a complete COF framework structure and affecting its crystallinity and porosity. Excessive PTSA may leave excessive impurities, interfering with the crystal form and porous structure of COF, adversely affecting subsequent oil storage performance and self-lubricating effects. The above ratio range ensures the catalyst functions fully, promoting a complete condensation reaction between Tta and the subsequently added trialdehyde phloroglucinol (TFP), forming a structurally complete and stable COF-Tta powder.

[0030] Then, trialdehyde phloroglucinol (TFP) is added to the well-mixed solution, and the resulting mixture is repeatedly shaken and mixed in a grinder for 30–40 minutes. TFP is another key monomer in the synthesis of covalent organic frameworks. Repeated shaking and mixing can ensure that TFP comes into full contact with Tta and PTSA in the solution, and can also provide energy for the condensation reaction. The mechanical energy generated during the shaking process can promote the interaction between monomer molecules, activate reaction sites, accelerate the initiation of the condensation reaction between Tta and TFP, help improve reaction efficiency, and initially realize the synthesis of monolayer or few-layer covalent organic frameworks, ensuring the subsequent formation of a complete and ordered periodic porous COF framework.

[0031] Specifically, the molar ratio of 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine to trialdehyde-resorcinol is 1:(0.9–1.1). This near-1:1 ratio ensures that both monomers fully participate in the reaction, reducing the residue of unreacted monomers and thus guaranteeing the crystallinity and pore integrity of the COF. If the ratio deviates too much, such as an excess of one monomer, unreacted monomer residues will remain, disrupting the ordered structure and porous properties of the COF, thereby affecting subsequent oil storage performance such as oil retention rate and controllable lubricant precipitation, as well as the final self-lubricating effect of the composite material.

[0032] S2. Place the mixed solution in an open container and let it stand overnight at room temperature to evaporate and remove the water. Then, place the open container and the mixed solution in an oven at 120–140°C and dry for 20–30 hours to obtain a solid with the water removed. Using natural evaporation followed by heating to remove water avoids the rapid evaporation of water in the mixed solution during direct oven drying, which could lead to a sudden increase in local concentration, causing monomer aggregation and disrupting the homogeneity of the reaction system. Standing at room temperature overnight allows for slow and uniform evaporation, removing most of the free water, reducing local concentration imbalances caused by rapid water loss, and lowering the intensity of water evaporation during subsequent high-temperature drying, preventing damage to the COF framework or defects. Subsequent high-temperature oven drying, with most of the water removed, utilizes high temperatures to promote the stacking of single-layer or few-layer polymers to construct a three-dimensional spatial framework, ensuring sufficient crystallization of the COF framework, i.e., achieving the construction of a periodic pore structure during the heating and drying process.

[0033] Specifically, high-temperature heating at 120–140℃ promotes the condensation reaction between Tta and TFP. Too low a temperature results in a slow and incomplete reaction, failing to form a complete framework structure; too high a temperature may lead to monomer decomposition or collapse of the COF framework structure. Drying time should be controlled at 20–30 hours to ensure the reaction proceeds fully and the COF framework crystallizes completely; insufficient time will result in an incomplete framework structure.

[0034] S3. Rinse the solid material after removing moisture with plenty of hot water and perform multiple vacuum filtrations until residual p-toluenesulfonic acid is removed. PTSA has completed its function after the COF-Tta framework is formed, but its residue can affect product purity and subsequent properties, such as crystal stability and porous structure integrity. Hot water can dissolve PTSA, and repeated rinsing and vacuum filtration can thoroughly remove residual catalyst, preventing it from interfering with the chemical structure and physical properties of COF-Tta.

[0035] Multiple vacuum filtration and washing processes using tetrahydrofuran (THF) remove unreacted monomers and impurities, purifying the product to obtain a solid. THF, as an organic solvent, dissolves incompletely reacted Tta or TFP monomers and other organic impurities. Multiple vacuum filtration and washing processes further purify the product, removing residual organic impurities and ensuring that the final COF-Tta powder possesses a pure chemical composition and a complete framework structure.

[0036] Finally, the solid product was dried in an oven at 80–90°C overnight to obtain COF-Tta powder. The purpose of drying was to remove residual moisture and tetrahydrofuran from the washing process. The temperature of 80–90°C effectively evaporated the solvent while avoiding the collapse of the COF-Tta framework structure or the destruction of its crystal form due to high temperatures.

[0037] S4. The COF-Tta powder is mixed with an excess of lubricating oil and impregnated under vacuum at room temperature overnight to fully remove air from the COF-Tta micropores, allowing the lubricating oil to fully penetrate the internal channels of the COF-Tta, thus obtaining the product. The product is then washed with methanol and water, centrifuged to remove residual lubricating oil from the COF-Tta surface, and dried overnight in an oven at 100–120°C to remove residual methanol and moisture while preventing excessive temperature from causing lubricating oil evaporation, ensuring the stability of the oil-storing microcapsules, thus obtaining COF-Tta@Oil oil-storing microcapsules. Specifically, the lubricating oil includes PAO2, PAO4, PAO6, PAO8, and PAO10, all of which are low-viscosity lubricating oils capable of impregnating the pore structure of COF-Tta.

[0038] The present invention also provides a porous covalent organic framework oil storage microcapsule, which is prepared by the above-described method for preparing porous covalent organic framework oil storage microcapsules.

[0039] This invention also provides an application of porous covalent organic framework (COF-Tta@Oil) oil-storing microcapsules. These microcapsules are incorporated into a polymer matrix via physical blending to prepare a COF-Tta@Oil oil-storing microcapsule self-lubricating reinforced modified polymer composite material. The polymer matrix comprises one of ultra-high molecular weight polyethylene, phenolic resin, polyurethane, and epoxy resin. This composite material improves self-lubricating performance primarily in the following ways: Firstly, COF-Tta possesses a periodic porous structure, enabling stable adsorption and storage of lubricating oil. During operation, under frictional stimulation, lubricating oil can be controllably exuded from the pores, forming a lubricating film at the friction interface, reducing the coefficient of friction. Furthermore, its porous structure avoids the problem of uncontrolled lubricating oil leakage after the shell of traditional single-channel microcapsules ruptures, ensuring continuous lubrication stability. Secondly, COF-Tta, as a hard particle incorporated into the polymer matrix, enhances the polymer's wear resistance, reduces wear during friction, and indirectly ensures the self-lubricating effect. Meanwhile, as an all-organic framework material, COF-Tta has better compatibility with organic polymer substrates than metal-based or silicon-based microcapsules, reducing interface defects and avoiding performance fluctuations caused by interface peeling during friction, thus ensuring that the composite material maintains stable self-lubricating properties over a long period of time.

[0040] Specifically, the mass fraction of COF-Tta@Oil oil-storing microcapsules in the COF-Tta@Oil oil-storing microcapsule self-lubricating reinforced modified polymer composite material is 0.2%–0.8%. Appropriate addition of oil-storing microcapsules ensures that sufficient lubricating oil can be controllably precipitated from the microcapsule channels during friction, forming a stable lubricating film at the friction interface and effectively reducing the coefficient of friction. Simultaneously, this proportion avoids agglomeration problems caused by excessive microcapsules. Excessive doping may disrupt the continuity of the polymer matrix, increasing stress concentration during friction and leading to an increased wear rate.

[0041] To further illustrate the porous covalent organic framework oil storage microcapsule, its preparation method, and its application provided by the present invention, the following embodiments are provided.

[0042] Example 1

[0043] A method for preparing porous covalent organic framework oil-storing microcapsules includes the following steps:

[0044] S1. Weigh out Tta and PTSA and add them to an appropriate amount of purified water. Stir and mix, then mix by shaking in a grinder for 10 minutes. Specifically, add 0.06 mmol of Tta per milliliter of water. The molar ratio of Tta to PTSA is 1:8.

[0045] Then, TFP is added to the well-mixed solution, and the resulting mixture is again shaken and mixed in a grinder for 30–40 minutes. The molar ratio of Tta to TFP is 1:1.

[0046] S2. Place the mixed solution in an open container and let it stand at room temperature overnight; then place the open container and the mixed solution in an oven at 140°C and dry for 20 hours to obtain a solid with the moisture removed.

[0047] S3. Rinse the dehydrated solid with plenty of hot water, then vacuum filter, repeating three times. Perform three vacuum filtrations and washings with THF to obtain the solid product. Finally, dry the solid product in an oven at 80°C overnight to obtain COF-Tta powder.

[0048] S4. COF-Tta powder was mixed with an excess of lubricating oil (PAO6) and impregnated. The mixture was stirred under vacuum overnight at room temperature to obtain the product. The product was then washed with methanol and water, centrifuged, and dried overnight in an oven at 120°C to obtain COF-Tta@Oil oil storage microcapsules.

[0049] S5. COF-Tta@Oil oil storage microcapsules are incorporated into ultra-high molecular weight polyethylene polymer matrix by physical blending to obtain COF-Tta@Oil oil storage microcapsule self-lubricating reinforced modified polymer composite material.

[0050] Performance test of Example 1:

[0051] 1. The COF-Tta powder obtained in step S3 was characterized for its crystallinity, chemical structure, and porosity (see [reference]). Figure 2 The chemical and crystal structures of COF-Tta can be confirmed. Infrared spectroscopy (b) confirms the successful synthesis of COF-Tta via the condensation reaction of Tta and TFP through the appearance of characteristic peaks. Powder X-ray characterization (a) shows that COF-Tta has high crystallinity and a very high matching with the simulated crystal structure, indicating the formation of an ordered periodic framework structure. Nitrogen adsorption-desorption testing (c) shows that COF-Tta has a high specific surface area, reaching 861 m². 2 g -1 It also has uniform micropores (d) of 1.1 nm.

[0052] 2. The COF-Tta@Oil oil-storing microcapsules obtained in step S4 were subjected to thermogravimetric analysis and porosity analysis (see [link to relevant documentation]). Figure 3Thermogravimetric analysis (a) showed that the oil content in the COF-Tta@Oil oil-storing microcapsules was 50%, clarifying the oil storage capacity of the microcapsules. Porosity analysis (b) showed that after storing lubricating oil, the specific surface area of ​​the COF-Tta@Oil oil-storing microcapsules increased from 861 m². 2 g -1 It dropped to 22 m 2 g -1 This directly demonstrates that the micropores of COF-Tta are fully filled with lubricating oil, verifying its effectiveness as an oil storage carrier.

[0053] The COF-Tta@Oil oil-storing microcapsules obtained in step S4 were incorporated into the ultra-high molecular weight polyethylene polymer matrix by physical blending at the mass fractions shown in Table 1. The resulting COF-Tta@Oil oil-storing microcapsule self-lubricating reinforced modified polymer composite material was subjected to self-lubricating tribological testing. The testing equipment was Rtec (model MFT2000), and the testing conditions were as follows: stainless steel balls were used as the friction pair, friction was conducted through a ball-disc, the friction mode was reciprocating friction, no lubricating medium was added, and the linear velocity was 0.02 m / s. The test results are shown in Table 1.

[0054] Table 1. Friction coefficient and wear rate of UHMWPE composites with different COF-Tta@Oil microcapsule contents

[0055]

[0056] Example 2

[0057] A method for preparing porous covalent organic framework oil-storing microcapsules includes the following steps:

[0058] S1. Weigh out Tta and PTSA and add them to an appropriate amount of purified water. Stir and mix, then mix by shaking in a grinder for 15 minutes. Specifically, add 0.08 mmol / mL of Tta per milliliter of water. The molar ratio of Tta to PTSA is 1:10.

[0059] Then, TFP was added to the well-mixed solution, and the resulting mixture was again shaken and mixed in a grinder for 30–40 minutes. The molar ratio of Tta to TFP was 1:0.9.

[0060] S2. Place the mixed solution in an open container and let it stand at room temperature overnight; then place the open container and the mixed solution in an oven at 130°C and dry for 24 hours to obtain a solid with the moisture removed.

[0061] S3. The solid material after removing moisture is washed with a large amount of hot water and vacuum filtered, repeated three times. Three vacuum filtrations and washings are performed using THF to obtain the solid product. Finally, the solid product is dried in an oven at 85°C overnight to obtain COF-Tta powder.

[0062] S4. COF-Tta powder was mixed with an excess of lubricating oil (PAO10) and impregnated. The mixture was stirred under vacuum overnight at room temperature to obtain the product. The product was then washed with methanol and water, centrifuged, and dried overnight in an oven at 110°C to obtain COF-Tta@Oil oil-storing microcapsules.

[0063] S5. COF-Tta@Oil oil storage microcapsules were incorporated into a phenolic resin polymer matrix at a mass fraction of 0.6% by physical blending to obtain a COF-Tta@Oil oil storage microcapsule self-lubricating reinforced modified polymer composite material.

[0064] Performance testing: The coefficient of friction of the COF-Tta@Oil oil-storing microcapsule self-lubricating reinforced modified polymer composite material prepared in Example 2 was 0.072, and the wear rate was 2.5 × 10⁻⁶. -6 mm 3 / Nm.

[0065] Example 3

[0066] A method for preparing porous covalent organic framework oil-storing microcapsules includes the following steps:

[0067] S1. Weigh out Tta and PTSA and add them to an appropriate amount of purified water. Stir and mix, then mix by shaking in a grinder for 20 minutes. Specifically, add 0.05 mmol of Tta per milliliter of water. The molar ratio of Tta to PTSA is 1:9.

[0068] Then, TFP was added to the well-mixed solution, and the resulting mixture was again shaken and mixed in a grinder for 30–40 minutes. The molar ratio of Tta to TFP was 1:1.1.

[0069] S2. Place the mixed solution in an open container and let it stand at room temperature overnight; then place the open container and the mixed solution in an oven at 120°C and dry for 30 hours to obtain a solid with the moisture removed.

[0070] S3. The solid material after removing moisture is washed with a large amount of hot water and vacuum filtered, repeated three times. Three vacuum filtrations and washings are performed using THF to obtain the solid product. Finally, the solid product is dried in an oven at 90°C overnight to obtain COF-Tta powder.

[0071] S4. COF-Tta powder was mixed with an excess of lubricating oil (PAO4) and impregnated. The mixture was stirred under vacuum overnight at room temperature to obtain the product. The product was then washed with methanol and water, centrifuged, and dried overnight in an oven at 100°C to obtain COF-Tta@Oil oil storage microcapsules.

[0072] S5. COF-Tta@Oil oil storage microcapsules were incorporated into an epoxy resin polymer matrix at a mass fraction of 0.6% by physical blending to obtain a COF-Tta@Oil oil storage microcapsule self-lubricating reinforced modified polymer composite material.

[0073] Performance testing: The coefficient of friction of the COF-Tta@Oil oil-storing microcapsule self-lubricating reinforced modified polymer composite material prepared in Example 3 was 0.071, and the wear rate was 2.5 × 10⁻⁶. -6 mm 3 / Nm.

[0074] Comparative Example 2

[0075] The preparation method of the porous covalent organic framework oil-storing microcapsules in Comparative Example 2 is basically the same as that in Example 1, except that the molar ratio of Tta to TFP in step S1 is 1:0.7. The mass fraction of the COF-Tta@Oil oil-storing microcapsules is also 0.6%.

[0076] Performance testing: The specific surface area of ​​COF-Tta powder in Comparative Example 2 was 220 m². 2 g -1 The coefficient of friction of the ultra-high molecular weight polyethylene polymer composite material is 0.11, and the wear rate is 3.6 × 10⁻⁶. -6 mm 3 / Nm.

[0077] The significant difference in the proportions of the two reactants in Comparative Example 2 affected the polymerization rate, making it difficult to achieve a complete polymerization reaction. This, in turn, affected the crystallinity and porosity of the product COF-Tta, resulting in defects such as uneven pore distribution and decreased specific surface area in its porous structure. This directly impacted the oil storage capacity of COF-Tta, leading to a reduction in lubricating oil impregnation. When this defective COF-Tta@Oil oil-storing microcapsule was incorporated into UHMWPE at a mass fraction of 0.6%, the microcapsule itself had insufficient oil storage capacity and unstable pore structure, making it difficult to continuously release sufficient lubricating oil to form an effective lubricating film during friction. This resulted in an increase in the friction coefficient of the composite material. Simultaneously, the incomplete COF-Tta structure weakened its reinforcing effect on the polymer as a hard particle, leading to a decrease in the wear resistance of the composite material and an increase in the wear rate.

[0078] In summary, this invention utilizes covalent organic frameworks (COFs) as microencapsulated lubricating oil, and then incorporates them into polymers for enhancement and modification. On one hand, the periodic porous structure of the COFs allows for the adsorption and storage of lubricating oil, enabling controlled release during operation to provide lubrication and achieve a high-performance self-lubricating effect. On the other hand, the incorporation of COFs as hard particles into the polymer matrix significantly enhances its wear resistance. Furthermore, as an all-organic framework structure material, COFs exhibit better compatibility with organic polymer matrices compared to metal-based and silicon-based microencapsulations, offering significant advantages for further improving the performance stability of self-lubricating bearing materials. This invention provides important reference value for the development of high-performance self-lubricating bearings.

[0079] It is understood that those skilled in the art can make equivalent substitutions or changes to the technical solution and inventive concept of the present invention, and all such changes or substitutions should fall within the protection scope of the present invention.

Claims

1. A method for preparing porous covalent organic framework oil storage microcapsules, characterized in that, Comprise the following steps: S1, take 4, 4', 4''-(1, 3, 5-triazine-2, 4, 6-triyl) triphenylamine and p-toluenesulfonic acid added to water, mixed evenly; to the mixed solution is added to the mixed solution is repeatedly shaken again, realize the preliminary synthesis of covalent organic framework; wherein, 4, 4', 4''-(1, 3, 5-triazine-2, 4, 6-triyl) triphenylamine and p-toluenesulfonic acid molar ratio is 1∶ (8~10); 4, 4', 4''-(1, 3, 5-triazine-2, 4, 6-triyl) triphenylamine and tri-aldehyde m-phenol molar ratio is 1∶ (0.9~1.1); S2, heated mixed solution, promote the preliminary synthesis of covalent organic framework layer by layer stacking structure three-dimensional space skeleton, realize the construction of organic covalent framework periodic pore structure, and get solid material; S3, remove the solid material in the above p-toluenesulfonic acid; using organic solvent purification solid material, get solid product; the solid product is dried to obtain 4, 4', 4''-(1, 3, 5-triazine-2, 4, 6-triyl) triphenylamine covalent organic framework powder; S4, 4, 4', 4''-(1, 3, 5-triazine-2, 4, 6-triyl) triphenylamine covalent organic framework powder and excess lubricating oil mixed with impregnation; remove the residual lubricating oil on the surface of 4, 4', 4''-(1, 3, 5-triazine-2, 4, 6-triyl) triphenylamine covalent organic framework powder after drying, get 4, 4', 4''-(1, 3, 5-triazine-2, 4, 6-triyl) triphenylamine covalent organic framework oil microcapsule.

2. The method for preparing porous covalent organic framework oil-storing microcapsules according to claim 1, characterized in that, The specific operation of step S1 is: take 4, 4', 4''-(1, 3, 5-triazine-2, 4, 6-triyl) triphenylamine and p-toluenesulfonic acid added to water, stirring mixed, mixed by grinding instrument vibration 10~20 minutes; to the mixed solution is added to the mixed solution is again mixed by grinding instrument vibration 30~40 minutes.

3. The method of claim 1, wherein the porous covalent organic framework oil storage microcapsules are prepared by the steps of: 0.04~0.08 mmol of 4, 4', 4''-(1, 3, 5-triazine-2, 4, 6-triyl) triphenylamine is added to each milliliter of water in step S1.

4. The method of claim 1, wherein the porous covalent organic framework oil storage microcapsules are prepared by the steps of: The specific operation of step S2 is: the mixed solution is placed in an open container, room temperature overnight, evaporation to remove water in the mixed solution; again the open container and mixed solution is placed in the oven at a temperature of 120~140℃ drying 20~30h, get the solid material of removing water.

5. The method for preparing porous covalent organic framework oil-storing microcapsules according to claim 1, characterized in that, The specific operation of step S3 is: the solid material after removing water is washed with a large amount of hot water, multiple vacuum filtration, until the residual p-toluenesulfonic acid is removed; using tetrahydrofuran vacuum filtration washing, get solid product; the solid product is placed in the oven at 80~90℃ drying overnight to obtain 4, 4', 4''-(1, 3, 5-triazine-2, 4, 6-triyl) triphenylamine covalent organic framework powder. The specific operation of step S3 is: the solid material after removing water is washed with a large amount of hot water, multiple vacuum filtration, until the residual p-toluenesulfonic acid is removed; using tetrahydrofuran vacuum filtration washing, get solid product; the solid product is placed in the oven at 80~90℃ drying overnight to obtain 4, 4', 4''-(1, 3, 5-triazine-2, 4, 6-triyl) triphenylamine covalent organic framework powder.

6. The method for preparing porous covalent organic framework oil-storing microcapsules according to claim 1, characterized in that, The specific operation of step S4 is: mixing and impregnating the 4,4',4''-(1,3,5-triazine-2,4,6-triyl) triphenylamine covalent organic framework powder with excess lubricating oil to obtain a product; washing and centrifuging the product with methanol and water to remove the residual lubricating oil on the surface of the 4,4',4''-(1,3,5-triazine-2,4,6-triyl) triphenylamine covalent organic framework powder, and drying the product in an oven at a temperature of 100-120℃ overnight to obtain 4,4',4''-(1,3,5-triazine-2,4,6-triyl) triphenylamine covalent organic framework oil storage microcapsules.

7. A porous covalent organic framework oil storage microcapsule characterized in that, The 4,4',4''-(1,3,5-triazine-2,4,6-triyl) triphenylamine covalent organic framework oil storage microcapsules are prepared by the method of any one of claims 1-6.

8. Use of a porous covalent organic framework oil storage microcapsule characterized in that, The porous covalent organic framework oil storage microcapsules as claimed in claim 7 are doped into a polymer matrix by physical blending to prepare 4,4',4''-(1,3,5-triazine-2,4,6-triyl) triphenylamine covalent organic framework oil storage microcapsule self-lubricating reinforced modified polymer composites; the polymer matrix includes one of ultrahigh molecular weight polyethylene, phenolic resin, polyurethane, and epoxy resin.

9. Use of the porous covalent organic framework oil storage microcapsules according to claim 8, characterized in that, The mass fraction of the 4,4',4''-(1,3,5-triazine-2,4,6-triyl) triphenylamine covalent organic framework oil storage microcapsules in the 4,4',4''-(1,3,5-triazine-2,4,6-triyl) triphenylamine covalent organic framework oil storage microcapsule self-lubricating reinforced modified polymer composites is 0.2-0.8%. The specific operation of step S4 is: mixing and impregnating the 4,4',4''-(1,3,5-triazine-2,4,6-triyl) triphenylamine covalent organic framework powder with excess lubricating oil to obtain a product; washing and centrifuging the product with methanol and water to remove the residual lubricating oil on the surface of the 4,4',4''-(1,3,5-triazine-2,4,6-triyl) triphenylamine covalent organic framework powder, and drying the product in an oven at a temperature of 100-120℃ overnight to obtain 4,4',4''-(1,3,5-triazine-2,4,6-triyl) triphenylamine covalent organic framework oil storage microcapsules.

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