A metal-organic framework composite coating based on confinement effect and a preparation method and application thereof

Abstract

This invention provides a metal-organic framework (MOF) composite coating based on the confinement effect, its preparation method, and its application, belonging to the field of composite coating technology. This invention achieves effective shielding of water vapor and hydrogen by precisely controlling the structural parameters of MOFs and utilizing confinement and shape-selective effects. The maximum pore size of the water- and hydrogen-blocking MOF material is smaller than the aerodynamic diameter of hydrogen molecules; the confinement and shape-selective effects achieve the effect of water and hydrogen barrier. Its low porosity (≤40%) allows for the formation of a dense MOF surface coating. This invention obtains a layer-by-layer self-assembled MOF composite coating on the substrate surface through a repeated heating-impregnation-drying process using an in-situ growth method. The strong adhesion of the coating to the substrate surface ensures a continuous and defect-free coating. The layer-by-layer self-assembly method provides capillary and covalent bonds between the MOF composite coating layers, enhancing the structural stability of the MOF material.

Description

Technical Field

[0001] This invention relates to the field of composite coating technology, and in particular to a metal-organic framework composite coating based on confinement effect, its preparation method, and its application. Background Technology

[0002] Liquefied Natural Gas (LNG) is a liquid formed from natural gas after purification and cooling to below -162°C. Its main component is methane, making it a very clean energy source. LNG onboard cylinders are a core component of LNG supply modules in commercial vehicles, and leakage in the vacuum jacket of these cylinders has been a persistent problem affecting their lifespan. Since the leakage originates from the container metal and the insulating composite winding material, the gas mainly consists of hydrogen released from the metal and water vapor released from the insulation material. Furthermore, leakage at the weld seals is difficult to avoid in onboard cylinders. Therefore, the current common practice is to place adsorbents in the jacket to maintain the vacuum life of the cryogenic container.

[0003] Currently, conventional vacuum sandwich adsorbents include palladium oxide and molecular sieves. Palladium oxide adsorbs released hydrogen through a chemical reaction, while molecular sieves adsorb other gases such as water vapor through physical adsorption. In practical applications, the adsorption efficiency of these two adsorbents is closely related to the amount and placement method of the adsorbent. Therefore, under vehicle conditions, changes in placement will reduce the adsorption efficiency. Furthermore, palladium oxide is expensive, resulting in high costs; and the excessive use of molecular sieves is detrimental to the lightweight design of LNG vehicle containers. Therefore, there is an urgent need to develop a vacuum sandwich adsorption technology that is water-barrier and hydrogen-blocking, low-cost, lightweight, and suitable for vehicle vibration conditions to meet practical industrial needs. Summary of the Invention

[0004] In view of this, the present invention aims to provide a metal-organic framework composite coating based on the confinement effect, its preparation method, and its application. The metal-organic framework composite coating provided by the present invention can effectively isolate water vapor and hydrogen in the vacuum interlayer, maintain the high vacuum level of the container, and thus significantly improve the vacuum life of the container.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing a metal-organic framework composite coating based on the confinement effect, comprising the following steps:

[0007] Provide water-barrier and hydrogen-barrier MOFs materials; the maximum pore size of the water-barrier and hydrogen-barrier MOFs materials And the porosity is ≤40%;

[0008] The water-barrier and hydrogen-barrier MOFs material is ultrasonically mixed with resin and adhesive to obtain MOFs composite resin.

[0009] The MOFs composite resin is mixed with an organic solvent to obtain an impregnation solution;

[0010] The substrate is placed in the impregnation solution, and the heating impregnation-drying process is repeated to form a metal-organic framework composite coating based on the confinement effect on the substrate surface.

[0011] Preferably, the water-barrier and hydrogen-barrier MOFs material is one or more of ICAVEP, YAFGAP, IDAZEU, IQUNAJ, WENSIS, CUFJUK, IQUNAJ01, EKIJEP, ORUHAM, and SOPPOD, and the name of the water-barrier and hydrogen-barrier MOFs material comes from the CoRE-MOFs database.

[0012] Preferably, the resin is one or more of polyester resin, polyamide resin and acrylic resin;

[0013] The adhesive is one or more of acrylate, butadiene, and polyurethane.

[0014] Preferably, the MOFs composite resin comprises, by weight parts:

[0015] 5-10 parts of water-resistant and hydrogen-barrier MOF material:

[0016] 40-50 parts of resin;

[0017] 5 to 10 parts of adhesive.

[0018] Preferably, the substrate is a container metal of a liquefied natural gas vehicle-mounted cylinder vacuum jacket and a heat-insulating composite winding material.

[0019] Preferably, the mass ratio of the MOFs composite resin to the organic solvent is 1:8 to 10.

[0020] Preferably, the temperature for each heating and impregnation is independently 120–150°C, and the time is independently 24–36 h;

[0021] The process of repeated heating, impregnation, and drying is repeated 2 to 3 times.

[0022] This invention provides a metal-organic framework composite coating based on the confinement effect prepared by the above preparation method.

[0023] This invention provides the application of the above-mentioned metal-organic framework composite coating based on confinement effect in liquefied natural gas vehicle cylinders.

[0024] Preferably, the metal-organic framework composite coating based on the confinement effect is applied to the surface of the container metal and the thermal insulation composite winding material of the vacuum jacket;

[0025] The thickness of the metal-organic framework composite coating based on the confinement effect is 450–600 μm.

[0026] This invention provides a method for preparing a metal-organic framework composite coating based on the confinement effect, comprising the following steps: providing a water-barrier and hydrogen-barrier MOF material; the maximum pore size of the water-barrier and hydrogen-barrier MOF material... Furthermore, the porosity is ≤40%. The water-resistant and hydrogen-barrier MOFs material is ultrasonically mixed with resin and adhesive to obtain a MOFs composite resin. The MOFs composite resin is mixed with an organic solvent to obtain an impregnation solution. The substrate is placed in the impregnation solution, and the heating impregnation-drying process is repeated to form a metal-organic framework composite coating based on the confinement effect on the substrate surface. Metal-organic framework (MOFs) materials are crystalline materials self-assembled from metal ions and organic ligands, possessing advantages such as high specific surface area, large porosity, and tunable pore structure. This invention, through precise control of the structural parameters of MOFs, achieves the maximum pore size of the MOFs material. Furthermore, with a porosity ≤40%, MOFs can effectively shield water vapor and hydrogen gas by utilizing confinement and shape-selective effects. Specifically, the maximum pore size of the water- and hydrogen-barrier MOF material is smaller than the aerodynamic diameter of a hydrogen molecule. The confinement and shape-selective effects achieve water and hydrogen barrier properties; the low porosity (≤40%) allows for the formation of a dense MOF surface coating. This invention utilizes an in-situ growth method to obtain a layer-by-layer self-assembled MOF composite coating on the substrate surface through repeated heating-impregnation-drying processes. The strong adhesion of the coating to the substrate surface ensures a continuous and defect-free coating. The layer-by-layer self-assembly method provides capillary and covalent bonds between the MOF composite coating layers, enhancing the structural stability of the MOF material.

[0027] The beneficial effects of this invention are as follows:

[0028] 1. MOFs composite coatings effectively solve the problems of high raw material prices, difficulty in lightweighting, and safety risks in traditional methods for dealing with leakage and venting in vacuum interlayers. They achieve the functional requirements of water isolation and hydrogen barrier through confinement effect and shape selection effect.

[0029] 2. The MOFs composite coating prepared by this invention has good leveling properties, corrosion resistance, water and hydrogen barrier functions, pressure resistance, and stability during long-term operation. Moreover, it is cheaper than palladium oxide materials and achieves lightweight design compared to molecular sieve materials, making it widely applicable in the low-temperature vacuum industry.

[0030] Furthermore, the water-barrier and hydrogen-barrier MOFs material used in this invention has a simple synthesis method, which facilitates subsequent industrialization; the raw materials used in the synthesis are highly commercialized and inexpensive; it has good water and thermal stability, which is convenient for long-term use; and it has strong repeatability, which enables the coating properties to be consistent and stable. Attached Figure Description

[0031] Figure 1 3D image of the ICAVEP monolithic structure;

[0032] Figure 2 3D image of the YAFGAP monolithic structure;

[0033] Figure 3 3D image of the IDAZEU monolithic structure;

[0034] Figure 4 3D image of the IQUNAJ monolithic structure;

[0035] Figure 5 3D image of the WENSIS monolithic structure;

[0036] Figure 6 3D image of the CUFJUK monolithic structure;

[0037] Figure 7 3D image of the IQUNAJ01 monolithic structure;

[0038] Figure 8 3D image of the EKIJEP monolithic structure;

[0039] Figure 9 3D image of the ORUHAM monolithic structure;

[0040] Figure 10 3D image of the SOPPOD single-unit structure;

[0041] Figure 11 A schematic diagram illustrating the principle of using a metal-organic framework composite coating to isolate gas in the vacuum interlayer of an LNG cylinder;

[0042] Figure 12 Flowchart of in-situ growth impregnation operation for metal-organic framework composite coatings;

[0043] Figure 13 A schematic diagram of a metal-organic framework composite coating applied to the metal surface of a vacuum jacketed container;

[0044] Figure 14 The results of the corrosion resistance test of the MOFs composite resin material obtained in Example 1 in acid solution;

[0045] Figure 15 The leakage rate test results of the MOFs composite coating obtained in Example 1 during actual operation;

[0046] Figure 16 The leakage rate test results of the MOFs composite coating obtained in Example 2 during actual operation;

[0047] Figure 17 The leakage rate test results of the MOFs composite coating obtained in Example 3 during actual operation are shown. Detailed Implementation

[0048] This invention provides a method for preparing a metal-organic framework composite coating based on the confinement effect, comprising the following steps:

[0049] Provide water-barrier and hydrogen-barrier MOFs materials; the maximum pore size of the water-barrier and hydrogen-barrier MOFs materials And the porosity is ≤40%;

[0050] The water-barrier and hydrogen-barrier MOFs material is ultrasonically mixed with resin and adhesive to obtain MOFs composite resin.

[0051] The MOFs composite resin is mixed with an organic solvent to obtain an impregnation solution;

[0052] The substrate is placed in the impregnation solution, and the heating impregnation-drying process is repeated to form a metal-organic framework composite coating based on the confinement effect on the substrate surface.

[0053] This invention provides a water-barrier and hydrogen-barrier MOF material; the maximum pore size of the water-barrier and hydrogen-barrier MOF material is... Furthermore, the porosity is ≤40%. In this invention, the water-barrier and hydrogen-barrier MOFs material is preferably one or more of ICAVEP, YAFGAP, IDAZEU, IQUNAJ, WENSIS, CUFJUK, IQUNAJ01, EKIJEP, ORUHAM, and SOPPOD. The names of the water-barrier and hydrogen-barrier MOFs materials are derived from the CoRE-MOFs database (website: https: / / www.ccdc.cam.ac.uk / structures / ).

[0054] In this invention, the properties of the water-barrier and hydrogen-barrier MOFs material are shown in Table 1.

[0055] Table 1 Properties of water-barrier and hydrogen-barrier MOFs materials

[0056]

[0057] This invention does not have specific requirements regarding the source of the water-barrier and hydrogen-barrier MOFs material; commercially available water-barrier and hydrogen-barrier MOFs materials or self-prepared materials can be used. When self-prepared, the water-barrier and hydrogen-barrier MOFs material is preferably prepared by a solvothermal method. The preparation method for each type of water-barrier and hydrogen-barrier MOFs material is as follows:

[0058] (1) ICAEP chemical formula [Zn5Eu(OH)(H2O)3(mip)6·H2O] n

[0059] Synthesis method: A mixture of zinc acetylacetonate hydrate (1.5 mmol), ammonia (7.5 mmol), Eu2(SO4)3·8H2O (7.5 mmol), and 5-methylisophthalic acid (2.5 mmol) was stirred in 20 mL of H2O for 10 min, and then the mixture was transferred to a 40 mL Teflon-lined stainless steel container. The resulting mixture was subjected to self-pressure heating at 210 °C for 5 days. After the reaction mixture was slowly cooled to room temperature, a pale yellow powder was obtained, which was washed with distilled water and dried in air.

[0060] 3D image of ICAVEP monolithic structure as follows Figure 1 As shown.

[0061] (2) YAFGAP chemical formula [KLu(C2O4)2(H2O)4] n

[0062] Synthetic method: Lu(NO3)3·6H2O (14.07 mg, 0.03 mmol) and potassium 1,3,5-triazine-2,4,6-tricarboxylate (9.8 mg, 0.03 mmol) were dissolved in 15 mL of water. The solution was stirred at room temperature for 0.5 h and allowed to stand for one week; colorless blocky crystals were obtained in 40% yield.

[0063] 3D image of YAFGAP monolithic structure as shown below Figure 2 As shown.

[0064] (3) IDAZEU chemical formula [KLu(C2O4)2(H2O)4] n

[0065] Synthesis method: Lu(NO3) 3.6 H₂O (14.07 mg, 0.03 mmol) and potassium 1,3,5-triazine-2,4,6-tricarboxylate (9.8 mg, 0.03 mmol) were dissolved in 15 mL of water. The solution was stirred at room temperature for 0.5 h and allowed to stand for one week; colorless blocky crystals were obtained in 40% yield.

[0066] Note: IDAZEU has the same chemical formula and synthesis method as IDAZEU, but different structures. IDAZEU is a byproduct of the reaction of IDAZEU.

[0067] 3D image of the IDAZEU monolithic structure, as shown below Figure 3 As shown.

[0068] (4) IQUNAJ chemical formula YK(C2O4)2·4H2O

[0069] Synthesis method: 2 mmol of yttrium nitrate pentahydrate and 4 mmol of oxalic acid dihydrate were mixed and 20 mL of concentrated nitric acid was added at room temperature. Then, 34% concentrated potassium hydroxide was gradually added until precipitation was complete and the pH of the solution was close to neutral. During this stage, the temperature was 50 °C. The precipitate was filtered and dried at room temperature.

[0070] 3D image of the IQUNAJ monolithic structure as shown below Figure 4 As shown.

[0071] (5) WENSIS chemical formula [CdK2Zr(C2O4)4(H2O)8] n

[0072] Synthesis method: ZrOCl2·H2O (0.80 g, 2.5 mmol), oxalic acid (1.0 g, 8 mmol), and calcium chloride (0.05 g, 0.5 mmol) were dissolved in 50 mL of water. Potassium hydroxide was added dropwise to the solution until the pH reached 2. The clear solution was placed at 323 K for 15 days, and crystals were isolated in 5% yield.

[0073] 3D image of the WENSIS monolithic structure, as shown below Figure 5 As shown.

[0074] (6) CUFJUK Chemical formula Co3(OH)2(tpta)

[0075] Synthesis method: Co(NO3)2 (0.116 g, 0.40 mmol), H4tpta (0.042 g, 0.10 mmol), HClO4 (0.15 mL, 0.45 mmol), DMF (3 mL), and H2O (4 mL) were mixed and then sealed in a 15 mL polytetrafluoroethylene-lined stainless steel autoclave at 150 °C for 4 days. The resulting solid was washed and dried.

[0076] Note: H4tpta is terphenyl-3,2”,5”,3'-tetracarboxyate.

[0077] 3D image of CUFJUK monolithic structure as shown Figure 6 As shown.

[0078] (7) IQUNAJ01 Chemical formula YK(C2O4)2·1.64H2O

[0079] Synthesis method: 2 mmol of yttrium nitrate pentahydrate and 4 mmol of oxalic acid dihydrate were mixed and 20 mL of concentrated nitric acid was added at room temperature. Then, 34% concentrated potassium hydroxide was gradually added until precipitation was complete and the pH of the solution was close to neutral. During this stage, the temperature was 50 °C. The precipitate was filtered and dried at room temperature.

[0080] Note: IQUNAJ01 is a byproduct of (4).

[0081] 3D image of the IQUNAJ01 single-unit structure as shown below Figure 7 As shown.

[0082] (8) EKIJEP chemical formula [Co3(TPTA)(OH)2(H2O)4] n

[0083] Synthesis method: Co(NO3)2·6H2O (72.8 mg, 0.25 mmol) and H4TPTA (20.3 mg, 0.05 mmol) were dissolved in 20 mL of water and heated at 160 °C for 3 days in a polytetrafluoroethylene liner. After washing and drying, pink blocky crystals were obtained.

[0084] Note: H4TPTA stands for [1,1':4',1”-terphenyl]-2',3,3”,5'-tetracarboxylic acid.

[0085] 3D image of EKIJEP monolithic structure as shown Figure 8 As shown.

[0086] (9) ORUHAM chemical formula [Cd(4-pzpt)2] n

[0087] Synthesis method: CdCl2·2.5H2O (0.0228 g, 0.1 mmol) and 4-Hpzpt (0.0112 g, 0.05 mmol) were dissolved in a mixed solution of 9 mL LDM and 1 mL water. The solution was placed in a polytetrafluoroethylene liner and heated at 160 °C for 3 days. After cooling, washing and drying, pale yellow crystals were obtained.

[0088] Note: 4-Hpzpt is 3-(pyridin-4-yl)-5-(pyrazin-2-yl)-1H-1,2,4-triazole.

[0089] 3D image of the ORUHAM monomer structure as shown below Figure 9 As shown.

[0090] (10) SOPPOD chemical formula [Nd(C2O4)1.5(H2O)3]·2H2O

[0091] Synthesis method: Nd(NO3)3·6H2O (0.30 g, 0.66 mmol), oxalic acid (0.13 g, 1 mmol), and water (15 mL) were sealed in a reaction vessel lined with Teflon (25 mL). The pH was adjusted to 4–6 with an aqueous potassium hydroxide solution. The mixture was heated at 180 °C under autogenous pressure for 4 days, and then cooled to room temperature to obtain light purple crystals.

[0092] 3D image of the SOPPOD single-unit structure, as shown below Figure 10 As shown.

[0093] In this invention, the water-barrier and hydrogen-barrier MOFs material is preferably ground to obtain water-barrier and hydrogen-barrier MOFs material powder. In this invention, the particle size of the water-barrier and hydrogen-barrier MOFs material powder is preferably 80 mesh.

[0094] This invention involves ultrasonically mixing the aforementioned water-resistant and hydrogen-barrier MOFs material with resin and adhesive to obtain a MOFs composite resin. In this invention, the resin is preferably one or more of polyester resin, polyamide resin, and acrylic resin. In this invention, the resin serves as the base material for the composite material, possessing strong adsorption and adhesion, thus improving the coating's adhesion. The aforementioned resin imparts excellent water-resistant properties to the coating.

[0095] The adhesive is preferably one or more of acrylate, butadiene, and polyurethane.

[0096] In this invention, the MOFs composite resin preferably comprises, by mass fraction:

[0097] 5 to 10 parts of water-resistant and hydrogen-barrier MOFs material, more preferably 6 to 8 parts;

[0098] 40-50 parts of resin, more preferably 42-48 parts;

[0099] The adhesive comprises 5 to 10 parts, more preferably 6 to 8 parts.

[0100] In this invention, the frequency of the ultrasonic mixing is preferably 80-100 kHz, and the time is preferably 2-4 h, more preferably 3 h.

[0101] After obtaining the MOFs composite resin, the present invention mixes the MOFs composite resin with an organic solvent to obtain an impregnation solution. In the present invention, the organic solvent is preferably one or more of N,N-dimethylformamide, acetone, and dimethyl sulfoxide. In the present invention, the mass ratio of the MOFs composite resin to the organic solvent is preferably 1:8 to 10, more preferably 1:9.

[0102] After obtaining the impregnation solution, the present invention places the substrate in the impregnation solution and repeats the heating impregnation-drying process to form a metal-organic framework composite coating based on the confinement effect on the substrate surface. In the present invention, the substrate is preferably the container metal of the liquefied natural gas vehicle cylinder vacuum jacket and the thermal insulation composite winding material.

[0103] The present invention preferably performs the heating and impregnation in a reaction vessel. Specifically, the present invention places the MOF composite resin in a reaction vessel, adds an organic solvent, and then vertically places the pretreated vacuum-jacketed container metal and the heat-insulating composite winding material in the reaction vessel. After tightening the reaction vessel, it is placed in a constant-temperature forced-air drying oven for heating and impregnation. In the present invention, the pretreatment method preferably includes one or more of cleaning, polishing, and oxide removal.

[0104] In this invention, during the heating and impregnation process, the reaction vessel is preferably rotated.

[0105] In this invention, the temperature for each heating and impregnation is preferably 120-150°C, more preferably 130-140°C; and the time is preferably 24-36 hours, more preferably 28-32 hours.

[0106] In this invention, the drying method is preferably air drying; the drying time is preferably 24 to 36 hours, more preferably 28 to 32 hours.

[0107] The number of repetitions of the heating-impregnation-drying process is preferably 2 to 3 times.

[0108] In this invention, the thickness of the metal-organic framework composite coating formed by a single heating impregnation-drying process is preferably 150-200 μm, more preferably 160-180 μm; the thickness of the multilayer metal-organic framework composite coating obtained after repeated heating impregnation-drying is preferably 450-600 μm, more preferably 500-550 μm.

[0109] In this invention, the schematic diagram of the metal-organic framework composite coating isolating the gas in the vacuum interlayer of the LNG cylinder is shown below. Figure 11 As shown. Figure 11In the process, when hydrogen gas released from the metal in the vehicle-mounted bottle and water vapor released from the insulation material reach the boundary of the vacuum interlayer through the thermal motion of molecules, they will first encounter the metal-organic framework composite coating on the vacuum interlayer. The dense MOF material on the coating can effectively shield and isolate water vapor and hydrogen gas by utilizing the confinement effect and shape selection effect. The preferred resin material can also play a certain auxiliary role in water isolation.

[0110] The in-situ growth impregnation process flow chart for metal-organic framework composite coatings is as follows: Figure 12 As shown.

[0111] A schematic diagram of a metal-organic framework composite coating applied to the metal surface of a vacuum jacketed container is shown below. Figure 13 As shown.

[0112] This invention utilizes an in-situ growth method to obtain a layer-by-layer self-assembled MOFs composite coating on a substrate surface through a repeated heating-impregnation-drying process. The self-inhibition process ensures a continuous and defect-free MOFs composite coating. The layer-by-layer self-assembly method provides capillary and covalent bonds between the MOFs composite coating layers, enhancing the structural stability of the MOFs material. This invention coats the outer surface of the container metal and the insulating composite winding material in a vacuum jacket, effectively solving the problem of leakage in the vacuum jacket of vehicle-mounted bottles. It effectively isolates water vapor and hydrogen in the vacuum jacket, maintaining a high vacuum level in the container, thereby significantly improving the container's vacuum life. This invention has broad application value in the cryogenic vacuum industry.

[0113] The present invention provides a metal-organic framework composite coating based on confinement effect prepared by the above preparation method, wherein the metal-organic framework composite coating comprises a resin matrix and water-repellent and hydrogen-blocking MOFs material dispersed in the resin matrix.

[0114] In this invention, the resin matrix comprises resin and binder; the maximum pore size of the water-barrier and hydrogen-barrier MOFs material is... And the porosity is ≤40%.

[0115] This invention provides the application of the aforementioned confinement effect-based metal-organic framework composite coating in liquefied natural gas (LNG) vehicle cylinders. In this invention, the confinement effect-based metal-organic framework composite coating is preferably applied to the surface of the container metal and the insulating composite winding material within a vacuum jacket.

[0116] In this invention, the thickness of the metal-organic framework composite coating based on the confinement effect is preferably 450-600 μm, more preferably 500-550 μm.

[0117] The following detailed description, in conjunction with embodiments, illustrates the metal-organic framework composite coating based on confinement effect, its preparation method, and its application, but these should not be construed as limiting the scope of protection of this invention.

[0118] Example 1

[0119] The preparation method of metal-organic framework composite coatings based on confinement effect includes the following steps:

[0120] ZrOCl2·H2O (0.80 g, 2.5 mmol), oxalic acid (1.0 g, 8 mmol), and calcium chloride (0.05 g, 0.5 mmol) were dissolved in 50 mL of water. Potassium hydroxide was gradually added dropwise to the resulting solution until the pH reached 2. After standing at 323 K for 10 days, MOFs (Identifier: WENSIS) crystal powder was obtained.

[0121] The MOFs crystal powders were added to polyester resin according to the mass fraction, with a MOFs powder to resin ratio of 1:10. The mixture was ultrasonicated for 2 hours using an 80kHz ultrasonic device. Then, 10% acrylate binder was added, and the mixture was ultrasonicated again at 80kHz for 1 hour to obtain the MOFs composite resin material.

[0122] MOFs composite resin material was placed in a reactor, and N,N-dimethylformamide with a mass ratio of 1:9 to the resin was added. The pretreated vacuum-jacketed container metal and the heat-insulating composite winding material were then placed vertically in the reactor. After tightening the reactor, it was placed in a constant temperature drying oven at 150°C for 24 hours. After removal, it was air-dried for 24 hours. The above operation was repeated 3 times to form a three-level MOFs composite coating on the outer surface of the vacuum-jacketed container metal and the heat-insulating composite winding material.

[0123] Example 2

[0124] A mixture of zinc acetylacetonate hydrate (1.5 mmol), ammonia (7.5 mmol), Eu2(SO4)3·8H2O (7.5 mmol) and 5-methylisophthalic acid (2.5 mmol) was stirred in 20 mL of H2O for 10 min, transferred to the liner of a reaction vessel, and heated under pressure at 210 °C for 5 days. After washing and drying, a pale yellow MOFs (Identifier: ICAVEP) powder was obtained.

[0125] The MOFs crystal powders were added to acrylic resin according to the mass fraction, with a MOFs powder to resin ratio of 1:5. The mixture was sonicated for 2 hours using an 80kHz ultrasonic device. Then, 10% butadiene ester binder was added, and the mixture was sonicated at 100kHz for 1 hour to obtain the MOFs composite resin material.

[0126] MOFs composite resin material was placed in a reactor, and N,N-dimethylformamide with a mass ratio of 1:9 to the resin was added. The pretreated vacuum-jacketed container metal and the thermal insulation composite winding material were placed vertically in the reactor. After tightening the reactor, it was placed in a constant temperature drying oven at 120°C for 36 hours. After removal, it was air-dried for 36 hours. The above operation was repeated 3 times to form a three-level MOFs composite coating on the outer surface of the vacuum-jacketed container metal and the thermal insulation composite winding material.

[0127] Example 3

[0128] 14.07 mg (0.03 mmol) of lutetium nitrate hexahydrate and 9.8 mg (0.03 mmol) of potassium 1,3,5-triazine-2,4,6-tricarboxylate were dissolved in 15 mL of water and stirred evenly at room temperature. The solution was allowed to stand for one week to obtain colorless blocky crystals. After washing, drying and grinding, MOFs (Identifier: IDAZEU) crystal powder was obtained.

[0129] The MOFs crystal powders were added to polyamide resin according to the mass fraction, with a MOFs powder to resin ratio of 1:8. The mixture was sonicated for 2 hours using an 80kHz ultrasonic device. Then, 10% polyurethane binder was added, and the mixture was sonicated again at 100kHz for 1 hour to obtain the MOFs composite resin material.

[0130] MOFs composite resin material was placed in a reactor, and dimethyl sulfoxide was added in a mass ratio of 1:9 to the resin. The pretreated vacuum-jacketed container metal and the thermal insulation composite winding material were placed vertically in the reactor. After tightening the reactor, it was placed in a constant temperature drying oven at 150°C for 24 hours. After removal, it was air-dried for 24 hours. The above operation was repeated 3 times to form a three-level MOFs composite coating on the outer surface of the vacuum-jacketed container metal and the thermal insulation composite winding material.

[0131] Performance testing

[0132] (1) The corrosion resistance test results of the MOFs composite resin material obtained in Example 1 in 1 mol / L hydrochloric acid solution (room temperature) are as follows: Figure 14 As shown.

[0133] Depend on Figure 14 It can be seen that the MOFs composite resin material still maintains a quality retention rate of over 97.5% after 60 hours, indicating that the MOFs composite resin material has strong corrosion resistance.

[0134] (2) The leakage rate of the MOFs composite coatings obtained in Examples 1-3 was detected using a helium mass spectrometer vacuum leak detector. The leakage rate test results of the MOFs composite coating obtained in Example 1 during actual operation are as follows: Figure 15 As shown. The leakage rate test results of the MOFs composite coating obtained in Example 2 during actual operation are as follows. Figure 16 As shown. The leakage rate test results of the MOFs composite coating obtained in Example 3 during actual operation are as follows. Figure 17 As shown.

[0135] It can be seen that the leakage rate of the MOFs composite coating obtained by this invention is less than 2×10⁻⁶ during a three-month long-term operation. -9 Pa·m 3 / s indicates that the MOFs composite resin material has good water and hydrogen barrier properties, which can ensure that the container has a long vacuum life and meet the requirements of actual use.

[0136] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. Application of metal-organic framework composite coatings based on confinement effect in liquefied natural gas vehicle cylinders; The method for preparing the metal-organic framework composite coating based on the confinement effect includes the following steps: A water- and hydrogen-barrier MOFs material is provided; the maximum pore size of the water- and hydrogen-barrier MOFs material is <2.89 Å, and the porosity is ≤40%; The water-barrier and hydrogen-barrier MOFs material is ultrasonically mixed with resin and adhesive to obtain MOFs composite resin. The MOFs composite resin is mixed with an organic solvent to obtain an impregnation solution; The substrate is placed in the impregnation solution, and the heating impregnation-drying process is repeated to form a metal-organic framework composite coating based on the confinement effect on the substrate surface. The resin is one or more of polyester resin, polyamide resin and acrylic resin; By mass fraction, the MOFs composite resin comprises: 5-10 parts of water-resistant and hydrogen-barrier MOF material: 40-50 parts of resin; 5-10 parts adhesive; Each heating and impregnation session was conducted at an independent temperature of 120-150°C and for an independent time of 24-36 hours. The heating, impregnation, and drying process is repeated 2 to 3 times. The substrate is a container metal and a heat-insulating composite winding material for a liquefied natural gas vehicle-mounted cylinder vacuum jacket.

2. The application according to claim 1, characterized in that, The thickness of the metal-organic framework composite coating based on the confinement effect is 450~600 μm.

3. The application according to claim 1, characterized in that, The water-barrier and hydrogen-barrier MOFs material is one or more of ICAVEP, YAFGAP, IDAZEU, IQUNAJ, WENSIS, CUFJUK, IQUNAJ01, EKIJEP, ORUHAM, and SOPPOD, and the name of the water-barrier and hydrogen-barrier MOFs material comes from the CoRE-MOFs database.

4. The application according to claim 1, characterized in that, The adhesive is one or both of acrylate and polyurethane.

5. The application according to claim 1, characterized in that, The mass ratio of the MOFs composite resin to the organic solvent is 1:8~10.

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