Aerogel-coated MOF composite material as well as preparation method and application thereof

Abstract

The invention belongs to the field of functional materials, and particularly relates to an aerogel-coated MOF composite material and a preparation method and application thereof. According to the aerogel-coated MOF composite material provided by the invention, the aerogel-coated MOF composite material is a compound of silicon dioxide aerogel and a metal organic framework material, and the metal organic framework material is an aluminum-based MOF material or a zirconium-based MOF material; the aerogel-coated MOF composite material has high specific surface area and mechanical strength, can be effectively applied to production of autoclaved lightweight concrete and autoclaved aerated concrete, and effectively improves the lightweight, strength, durability and thermal insulation of the autoclaved lightweight concrete and autoclaved aerated concrete.

Description

Technical Field

[0001] The present invention belongs to the field of functional materials, and particularly relates to an aerogel@MOF composite material, a preparation method thereof, and an application thereof. Background Art

[0002] An aerogel refers to a lightweight nano-solid material with a nano-porous network structure and a large amount of gaseous dispersion medium filled in the network skeleton. Due to the special nature of its structure, aerogel materials have a wide range of uses. Silica aerogel is a three-dimensional porous network material composed of silica (SiO2) nanoparticles, with a porosity as high as 80%-99.8%, an extremely low density, and is one of the lightest solid materials known, famous for its ultra-low thermal conductivity, being an excellent thermal insulation material, and widely used in spacecraft thermal insulation layers, building energy-saving glass, and environmental governance. Its high specific surface area further expands the application potential. However, such materials are usually relatively brittle and have insufficient mechanical strength, and current research is improving their mechanical properties by compounding polymers and other methods.

[0003] Amino-functionalized ionic liquids are a type of modified material in which an amino group (-NH2) functional group is introduced into the structure of traditional ionic liquids, and are prepared by reacting γ-aminopropyltriethoxysilane with imidazole-based or pyridine-based ionic liquids.

[0004] Metal-organic framework materials (MOF) are porous crystalline materials formed by the self-assembly of metal ions or metal clusters and organic ligands through coordination bonds. MOF has a relatively high specific surface area, and its pore size and chemical function can be flexibly regulated by adjusting metal nodes and ligands, so it has attracted much attention in the fields of gas adsorption, catalysis, drug delivery, etc. According to different metal nodes, MOF can be divided into types such as aluminum-based and zirconium-based. Aluminum-based MOF has aluminum ions as the core and has the characteristics of low cost and high stability. For example, MIL-53(Al) is composed of Al 3+ and terephthalic acid ligands, and its unique flexible rhombic pore channels can undergo a reversible "breathing effect" with external conditions. Another representative material, CAU-10-H, uses 2,5-furandicarboxylic acid as a ligand to form a rigid microporous structure rich in hydroxyl groups.

[0005] Zirconium-based MOF uses zirconium oxygen clusters (Zr6O4(OH)4) as nodes and exhibits far higher chemical stability than other MOF, and can withstand strong acids, strong bases, and water environments. UiO-66 is a typical representative of such materials, forming an octahedral pore cage structure with a pore size of about 0.8 nm by zirconium oxygen clusters and terephthalic acid ligands, and is widely used in acid catalysis, nuclear waste radioactive ion adsorption, and photocatalytic degradation of pollutants. Its homolog, UiO-67, uses biphenyldicarboxylic acid ligands, and the pore size can be expanded to 1.2 nm.

[0006] Autoclaved aerated concrete (AAC) is a lightweight porous material mainly made of siliceous materials such as quartz sand and fly ash, and calcareous materials such as cement and lime, and is made by adding aluminum powder as a foaming agent. Its production process includes mixing raw materials, foaming and forming, cutting and pre-curing, and high-temperature and high-pressure steam curing.

[0007] Autoclaved lightweight concrete (ALC) generally covers all lightweight concretes made by the autoclaving process, but specifically refers to materials made by replacing part of the sand and gravel with lightweight aggregates such as ceramsite and expanded perlite. There may still be a small amount of foaming agent in its raw materials, but the pores mainly come from the porous structure of the lightweight aggregates themselves. Compared with AAC, ALC has a higher density, the compressive strength is increased to 37 MPa, the thermal conductivity slightly increases, but it is still better than traditional concrete. Summary of the Invention

[0008] The present invention aims to provide an aerogel@MOF composite material with excellent adsorption efficiency and mechanical stability, which can be effectively applied to the production of autoclaved lightweight concrete and autoclaved aerated concrete, and effectively improve the light weight, strength, durability and heat preservation of autoclaved lightweight concrete and autoclaved aerated concrete.

[0009] To achieve the above object, the present invention provides an aerogel@MOF composite material, which is a composite of silica aerogel and metal-organic framework material, and the metal-organic framework material is an aluminum-based MOF material or a zirconium-based MOF material.

[0010] For the above-mentioned aerogel@MOF composite material, the aluminum-based MOF material is MIL-53(Al) or CAU-10-H; the zirconium-based MOF material is UiO-66 or UiO-67.

[0011] On the other hand, the present invention also provides a preparation method of the above-mentioned aerogel@MOF composite material, including the following steps:

[0012] Step 1. Prepare silica aerogel, including the following steps:

[0013] Step 101. Mix tetraethyl orthosilicate, ethanol, and deionized water according to a molar ratio of 1:(3 - 5):(3 - 5), add hydrochloric acid to adjust the pH to 2 - 3, and stir and hydrolyze for 30 minutes to obtain a hydrolysis product;

[0014] Step 102. Add methyltrimethoxysilane to the hydrolysis product obtained in Step 101, adjust the pH to 5 - 6 and then let it stand for gelation to obtain a gel product; the molar ratio of tetraethyl orthosilicate to methyltrimethoxysilane is 3:2 - 7:3;

[0015] Step 103: Immerse the gel product obtained in Step 102 in an ethanol solvent, and then perform supercritical CO2 drying to obtain the silica aerogel;

[0016] Step Two: In-situ synthesis of the aerogel@MOF composite material, including the following steps:

[0017] Step 201: Dissolve a metal salt in a mixed solvent of an amino-functionalized ionic liquid and deionized water to obtain a metal salt solution;

[0018] Step 202: Dissolve an organic ligand in a mixed solvent of an amino-functionalized ionic liquid and DMF to obtain a ligand solution;

[0019] Step 203: Mix the metal salt solution obtained in Step 201 and the ligand solution obtained in Step 202 in a volume ratio of 1:1 to obtain a mixed solution;

[0020] Step 204: Add the silica aerogel to the mixed solution obtained in Step 203, and perform a hydrothermal reaction to obtain a composite material;

[0021] Step Three: Post-treat and functionalize the composite material obtained in Step 204, including the following steps:

[0022] Step 301: Centrifuge and collect the composite material obtained in Step 204, wash it alternately with DMF and ethanol, and dry it to obtain a dried composite material;

[0023] Step 302: Immerse the dried composite material obtained in Step 301 in an NaOH solution to obtain an activated composite material;

[0024] Step 303: Immerse the activated composite material obtained in Step 302 in an ethanol solution of a silane coupling agent KH-550, cure it, and then polish it in a ball mill to obtain the aerogel@MOF composite material.

[0025] In the above preparation method, the volume ratio of the amino-functionalized ionic liquid to deionized water in Step 201 is 1:4; the volume ratio of the amino-functionalized ionic liquid to DMF in Step 202 is 1:3; the mass concentration of the ethanol solution of the silane coupling agent KH-550 in Step 303 is 1-3 wt%, and the curing condition is impregnation at 60-100 °C for 0.5-2 hours; the rotation speed of the ball mill polishing is 100-300 rpm, the ball milling medium is zirconia beads, and the polishing time is 5-15 minutes.

[0026] On the other hand, provided is an application of the aerogel@MOF composite material in the preparation of an autoclaved aerated or autoclaved lightweight concrete additive.

[0027] On the other hand, the present invention also provides an additive as described above, and the additive is composed of components with the following mass percentages: 25-30% aerogel@MOF composite material, 3-5% hydrogen peroxide, 3-5% polycarboxylate superplasticizer, 1.5-2% isobutyltriethoxysilane, 10-20% sodium metasilicate, 1.5-3% polypropylene fiber, 0.3-0.45% iron oxide catalyst, 0.6-1% citric acid, and 45-55% water.

[0028] For the above-mentioned additive, the mass concentration of the hydrogen peroxide is 30%; the polycarboxylate superplasticizer is an alkali-resistant polycarboxylate superplasticizer, and the molecular weight of the polycarboxylate superplasticizer is 5000-20000 g / mol.

[0029] For the above-mentioned additive, the polypropylene fiber is surface-modified, and the modifier in the surface modification is a silane coupling agent or a titanate coupling agent, and the length of the polypropylene fiber is 3-12 mm.

[0030] The present invention also provides a preparation method of the above-mentioned additive, including the following steps:

[0031] Step 1: Pretreat the additive components, including the following steps:

[0032] Step 101: Immerse the polypropylene fiber in a 5% ethanol solution of silane coupling agent KH-550. After soaking for 30 minutes, dry it at 60 °C to obtain modified polypropylene fiber;

[0033] Step 102: Mix the polycarboxylate superplasticizer and silica fume in a mass ratio of 1:2, and spray-dry to make polycarboxylate superplasticizer powder with a particle size of 50-100 μm;

[0034] Step 103: Premix and grind the aerogel@MOF composite material and sodium metasilicate to a particle size of 20 μm to obtain a ground dry material;

[0035] Step 104: Premix the hydrogen peroxide and citric acid, and adjust the pH to 4.5-5.0 to obtain stable hydrogen peroxide;

[0036] Step 2: Start a high-speed mixer for dry mixing, including the following steps:

[0037] Step 201: Start the high-speed mixer, preheat it to 30 °C, put the ground dry material and the modified polypropylene fiber into the high-speed mixer, and mix for 20 minutes to obtain a pre-mixed dry material;

[0038] Step 202: Atomize and spray isobutyltriethoxysilane into the pre-mixed dry material obtained in Step 201, and mix for 15 minutes to obtain a completely mixed dry material;

[0039] Step 3. Wet-mix the completely mixed dry materials in Step 202, including the following steps:

[0040] Step 301. Heat 30% of the water to 25°C, add the polycarboxylate superplasticizer, stir until completely dissolved, inject it into the high-speed mixer, and stir at a low speed of 500 rpm for 10 minutes to obtain a pre-wet mixed material;

[0041] Step 302. Add the stable hydrogen peroxide obtained in Step 104 to the pre-wet dry material obtained in Step 301, and monitor the temperature;

[0042] Step 303. When the temperature monitored in Step 302 exceeds 30°C, add 30% of the water, increase the rotation speed to 1200 rpm, and continuously monitor the temperature;

[0043] Step 304. When the temperature monitored in Step 303 exceeds 30°C, add 30% of the water, and continuously stir for 10 min;

[0044] Step 305. Add the iron oxide catalyst to the high-speed mixer, supplement the remaining water volume, and continuously stir to obtain an additive.

[0045] In the above method, the inlet temperature of the spray drying in Step 102 is 150 - 180°C, the outlet temperature is 60 - 80°C, and the atomization pressure is 0.3 - 0.5 MPa.

[0046] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages:

[0047] 1. The aerogel@MOF composite material provided by the present invention has excellent adsorption efficiency and mechanical stability. The three-dimensional nano-porous network of silica aerogel provides a high specific surface area carrier for the in-situ growth of MOF. MOF uniformly nucleates in the pores of the aerogel through coordination bonds, forming a hierarchical pore structure. The micron-scale macroscopic pores of the aerogel are combined with the nano-scale micropores / mesopores of MOF to achieve a multi-scale mass transfer channel.

[0048] 2. In the preparation method of the aerogel@MOF composite material provided by the present invention, the silane coupling agent KH-550 introduces amino functional groups on the surface of the aerogel through hydrolysis and condensation reactions, and forms chemical bonding with the MOF metal nodes (such as Al 3+ or Zr6O4 clusters), reducing interface defects. Subsequent ball milling and polishing further eliminate MOF agglomeration, ensuring the uniformity of the composite material particles.

[0049] 3. The aerogel@MOF composite material of the present invention can effectively improve the thermal insulation performance of autoclaved aerated concrete. Its pores can act as "micro airbags" inside the concrete, reducing the matrix density while introducing a closed-cell structure, reducing heat convection transfer, and improving the thermal insulation performance. Moreover, when used as a raw material for preparing additives, the high specific surface area of MOF and its surface active sites can load functional molecules (such as flame retardants or impermeability agents), introducing specific functions into the concrete matrix through the additives to achieve the multi-purpose expansion of the material.

[0050] 4. In the preparation of autoclaved aerated concrete or autoclaved lightweight concrete using the aerogel@MOF composite material provided by the present invention, the silane-modified polypropylene fibers and the MOF framework synergistically inhibit the propagation of microcracks, while the powder design of the polycarboxylate water reducer enhances its dispersibility in the dry mix, reducing the water consumption while maintaining the fluidity of the slurry. This series of mechanisms ultimately balance the lightweight, strength, durability, and process adaptability of the concrete, meeting the requirements for material performance stability and construction efficiency in industrial production. Detailed implementation manners

[0051] Next, the technical solutions of the present invention will be described in conjunction with the embodiments. However, the present invention is not limited to the following embodiments. The experimental methods and detection methods described in each embodiment are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified. The % in the following embodiments is by mass percentage unless otherwise specified. The ratios in the following embodiments are by mass ratio unless otherwise specified.

[0052] Example 1

[0053] This example provides an aerogel@MOF composite material and its preparation method;

[0054] The aerogel@MOF composite material is a composite of silica aerogel and metal-organic framework material. The metal-organic framework material is an aluminum-based MOF material, and the aluminum-based MOF material is MIL-53(Al).

[0055] The preparation method of the above-mentioned aerogel@MOF composite material includes the following steps:

[0056] Step 1: Prepare silica aerogel, including the following steps:

[0057] Step 101: Mix tetraethyl orthosilicate, ethanol, and deionized water in a molar ratio of 1:5:5, add hydrochloric acid to adjust the pH to 3, and stir and hydrolyze for 30 minutes to obtain a hydrolysis product;

[0058] Step 102: Add methyltrimethoxysilane to the hydrolysis product obtained in Step 101, adjust the pH to 6, and then let it stand for gelation to obtain a gel product; the molar ratio of tetraethyl orthosilicate to methyltrimethoxysilane is 6:4;

[0059] Step 103: Immerse the gel product obtained in Step 102 in an ethanol solvent, and then perform supercritical CO2 drying to obtain the silica aerogel;

[0060] Step Two: In-situ synthesis of the aerogel@MOF composite material, including the following steps:

[0061] Step 201: Dissolve aluminum nitrate in a mixed solvent of amino-functionalized ionic liquid and deionized water to obtain a metal salt solution;

[0062] Step 202: Dissolve terephthalic acid in a mixed solvent of amino-functionalized ionic liquid and DMF to obtain a ligand solution;

[0063] Step 203: Mix the metal salt solution obtained in Step 201 and the ligand solution obtained in Step 202 in a volume ratio of 1:1 to obtain a mixed solution;

[0064] Step 204: Add the silica aerogel to the mixed solution obtained in Step 203, and perform a hydrothermal reaction to obtain a composite material;

[0065] Step Three: Post-treat and functionalize the composite material obtained in Step 204, including the following steps:

[0066] Step 301: Centrifuge and collect the composite material obtained in Step 204, and wash it alternately with DMF and ethanol, and then dry it to obtain a dried composite material;

[0067] Step 302: Immerse the dried composite material obtained in Step 301 in a NaOH solution to obtain an activated composite material;

[0068] Step 303: Immerse the activated composite material obtained in Step 302 in an ethanol solution of silane coupling agent KH-550, cure it, and then polish it in a ball mill to obtain the aerogel@MOF composite material.

[0069] In the above preparation method, the volume ratio of the amino-functionalized ionic liquid to deionized water in step 201 is 1:4; the volume ratio of the amino-functionalized ionic liquid to DMF in step 202 is 1:3; the mass concentration of the ethanol solution of the silane coupling agent KH-550 in step 303 is 3 wt%, and the curing condition is impregnation at 100 °C for 2 hours; the rotation speed of the ball mill for polishing is 300 rpm, the ball milling medium is zirconia beads, and the polishing time is 15 minutes.

[0070] Example 2

[0071] This example provides an aerogel@MOF composite material and a preparation method thereof;

[0072] The aerogel@MOF composite material is a composite of silica aerogel and a metal-organic framework material. The metal-organic framework material is a zirconium-based MOF material, and the zirconium-based MOF material is UiO-66.

[0073] For the above-mentioned aerogel@MOF composite material, its preparation method includes the following steps:

[0074] Step 1. Prepare silica aerogel, including the following steps:

[0075] Step 101. Mix tetraethyl orthosilicate, ethanol, and deionized water in a molar ratio of 1:3:3, add hydrochloric acid to adjust the pH to 2, and stir for hydrolysis for 30 minutes to obtain a hydrolysis product;

[0076] Step 102. Add methyltrimethoxysilane to the hydrolysis product obtained in step 101, adjust the pH to 5, and then let it stand for gelation to obtain a gel product; the molar ratio of tetraethyl orthosilicate to methyltrimethoxysilane is 7:3;

[0077] Step 103. Immerse the gel product obtained in step 102 in an ethanol solvent, and then perform supercritical CO2 drying to obtain the silica aerogel;

[0078] Step 2. In-situ synthesis of the aerogel@MOF composite material, including the following steps:

[0079] Step 201. Dissolve zirconium tetrachloride in a mixed solvent of an amino-functionalized ionic liquid and deionized water to obtain a metal salt solution;

[0080] Step 202. Dissolve terephthalic acid in a mixed solvent of an amino-functionalized ionic liquid and DMF to obtain a ligand solution;

[0081] Step 203. Mix the metal salt solution obtained in step 201 and the ligand solution obtained in step 202 in a volume ratio of 1:1 to obtain a mixed solution;

[0082] Step 204: Add the silica aerogel to the mixed solution obtained in Step 203, carry out a hydrothermal reaction to obtain a composite material;

[0083] Step Three: Post-treat and functionalize the composite material obtained in Step 204, including the following steps:

[0084] Step 301: Centrifuge and collect the composite material obtained in Step 204, wash it alternately with DMF and ethanol, and dry it to obtain a dried composite material;

[0085] Step 302: Immerse the dried composite material obtained in Step 301 in a NaOH solution to obtain an activated composite material;

[0086] Step 303: Immerse the activated composite material obtained in Step 302 in an ethanol solution of silane coupling agent KH-550, cure it and then polish it in a ball mill to obtain an aerogel@MOF composite material.

[0087] In the above preparation method, the volume ratio of the amino-functionalized ionic liquid to deionized water in Step 201 is 1:4; the volume ratio of the amino-functionalized ionic liquid to DMF in Step 202 is 1:3; the mass concentration of the ethanol solution of silane coupling agent KH-550 in Step 303 is 1 wt%, and the curing condition is impregnation at 100 °C for 0.5 hour; the rotation speed of the ball mill polishing is 100 rpm, the ball milling medium is zirconia beads, and the polishing time is 5 minutes.

[0088] Example 3

[0089] This example provides an additive and its preparation method. The additive is composed of the following components by mass percentage: 25% aerogel@MOF composite material, 3% hydrogen peroxide, 3% polycarboxylate water reducer, 2% isobutyltriethoxysilane, 18% sodium metasilicate, 3% polypropylene fiber, 0.3% iron oxide catalyst, 0.7% citric acid, and 45% water.

[0090] The mass concentration of the hydrogen peroxide is 30%, the polycarboxylate water reducer is an alkali-resistant polycarboxylate water reducer, and the molecular weight of the polycarboxylate water reducer is 20000 g / mol.

[0091] The polypropylene fiber has been surface-modified. The modifier in the surface modification is a silane coupling agent, and the length of the polypropylene fiber is 3 - 12 mm.

[0092] The preparation method of the above-mentioned additive includes the following steps:

[0093] Step One: Pretreat the additive components, including the following steps:

[0094] Step 101: Immerse the polypropylene fiber in a 5% silane coupling agent KH-550 ethanol solution. After soaking for 30 minutes, dry it at 60°C to obtain modified polypropylene fiber.

[0095] Step 102: Mix the polycarboxylate superplasticizer and silica fume in a mass ratio of 1:2, and spray-dry to make polycarboxylate superplasticizer powder with a particle size of 50 - 100 μm.

[0096] Step 103: Premix and grind the aerogel@MOF composite material and sodium metasilicate to a particle size of 20 μm to obtain a ground dry material.

[0097] Step 104: Premix hydrogen peroxide and citric acid, and adjust the pH to 4.5 to obtain stable hydrogen peroxide.

[0098] Step Two: Start the high-speed mixer for dry mixing, including the following steps:

[0099] Step 201: Start the high-speed mixer, preheat to 30°C, put the ground dry material and modified polypropylene fiber into the high-speed mixer, and mix for 20 minutes to obtain a pre-mixed dry material.

[0100] Step 202: Atomize and spray isobutyltriethoxysilane into the pre-mixed dry material obtained in Step 201, and mix for 15 minutes to obtain a completely mixed dry material.

[0101] Step Three: Perform wet mixing on the completely mixed dry material in Step 202, including the following steps:

[0102] Step 301: Heat 30% of the water to 25°C, add the polycarboxylate superplasticizer and stir until completely dissolved, inject it into the high-speed mixer, and stir at a low speed of 500 rpm for 10 minutes to obtain a pre-wet mixed material.

[0103] Step 302: Add the stable hydrogen peroxide obtained in Step 104 to the pre-wet dry material obtained in Step 301, and monitor the temperature.

[0104] Step 303: When the temperature monitored in Step 302 exceeds 30°C, add 30% water, increase the rotation speed to 1200 rpm, and continuously monitor the temperature.

[0105] Step 304: When the temperature monitored in Step 303 exceeds 30°C, add 30% water, and continuously stir for 10 minutes.

[0106] Step 305: Add the iron oxide catalyst to the high-speed mixer, supplement the remaining water volume, and continuously stir to obtain an additive.

[0107] The inlet temperature of the spray drying described in Step 102 is 1180 °C, the outlet temperature is 60 °C, and the atomization pressure is 0.3 MPa.

[0108] Example 4

[0109] This example provides an additive and its preparation method. The additive is composed of the following components by mass percentage: 30% aerogel@MOF composite material, 3% hydrogen peroxide, 3% polycarboxylate superplasticizer, 1.5% isobutyltriethoxysilane, 10% sodium metasilicate, 1.5% polypropylene fiber, 0.4% iron oxide catalyst, 0.6% citric acid, and 50% water.

[0110] The mass concentration of the hydrogen peroxide is 30%, the polycarboxylate superplasticizer is an alkali-resistant polycarboxylate superplasticizer, and the molecular weight of the polycarboxylate superplasticizer is 20000 g / mol.

[0111] The polypropylene fiber has been surface-modified. The modifier in the surface modification is a silane coupling agent, and the length of the polypropylene fiber is 3 - 12 mm.

[0112] The preparation method of the above-mentioned additive includes the following steps:

[0113] Step 1: Pretreat the additive components, including the following steps:

[0114] Step 101: Immerse the polypropylene fiber in a 5% ethanol solution of silane coupling agent KH-550. After soaking for 30 minutes, dry it at 60 °C to obtain modified polypropylene fiber;

[0115] Step 102: Mix the polycarboxylate superplasticizer and silica fume in a mass ratio of 1:2, and spray-dry to make polycarboxylate superplasticizer powder with a particle size of 50 - 100 μm;

[0116] Step 103: Premix and grind the aerogel@MOF composite material and sodium metasilicate to a particle size of 20 μm to obtain ground dry material;

[0117] Step 104: Premix the hydrogen peroxide and citric acid, and adjust the pH to 5.0 to obtain stable hydrogen peroxide;

[0118] Step 2: Start the high-speed mixer for dry mixing, including the following steps:

[0119] Step 201: Start the high-speed mixer, preheat to 30 °C, put the ground dry material and modified polypropylene fiber into the high-speed mixer, and mix for 20 minutes to obtain pre-mixed dry material;

[0120] Step 202: Atomize and spray isobutyltriethoxysilane into the pre-mixed dry material obtained in Step 201, and mix for 15 minutes to obtain completely mixed dry material;

[0121] Step 3: Wet-mix the completely mixed dry materials in Step 202, including the following steps:

[0122] Step 301: Heat 30% of the water to 25°C, add the polycarboxylate water reducer and stir until completely dissolved, inject it into the high-speed mixer, and stir at a low speed of 500 rpm for 10 minutes to obtain a pre-wet mixed material;

[0123] Step 302: Add the stable hydrogen peroxide obtained in Step 104 to the pre-wet dry material obtained in Step 301 and monitor the temperature;

[0124] Step 303: When the temperature monitored in Step 302 exceeds 30°C, add 30% of the water, increase the rotation speed to 1200 rpm, and continuously monitor the temperature;

[0125] Step 304: When the temperature monitored in Step 303 exceeds 30°C, add 30% of the water and continuously stir for 10 min;

[0126] Step 305: Add the iron oxide catalyst to the high-speed mixer, supplement the remaining water volume, and continuously stir to obtain an additive.

[0127] The inlet temperature of the spray drying in Step 102 is 150°C, the outlet temperature is 80°C, and the atomization pressure is ~0.5 MPa.

[0128] Example 5

[0129] This example verifies the influence of the additive prepared from the aerogel@MOF composite material provided by the present invention on the performance of AAC and ALC.

[0130] 1. Experimental design:

[0131] AAC group: Using aluminum powder (0.1%) as the foaming agent, the basic formula is 30% cement, 60% quartz sand, 5% gypsum, and 5% additive.

[0132] ALC group: Using ceramsite (replacing 30% of quartz sand) as the lightweight aggregate, the basic formula is 30% cement, 30% ceramsite, 30% quartz sand, 5% gypsum, and 5% additive.

[0133] Additives: Additives prepared from aerogel@MIL-53(Al), aerogel@UiO-66, and blank aerogel (control group) are used respectively.

[0134] 2. Concrete preparation:

[0135] AAC: Dry-mix the raw materials → Add water and stir (water-to-material ratio 0.6) → Inject into the mold to generate gas (pre-cure at 40°C for 4 h) → Cut → Autoclave cure (1.2 MPa, 180°C, 8 h).

[0136] ALC: Dry mixing of raw materials → Adding water and stirring (water-to-material ratio 0.5) → Injecting into mold and vibrating for forming → Autoclaving curing (1.0 MPa, 170 °C, 10 h).

[0137] 3. Performance test results:

[0138] Test standard: GB / T 11969-2020 "Test Methods for the Properties of Autoclaved Aerated Concrete"

[0139] The test results of mechanical and physical properties are shown in Table 1.

[0140] Table 1: Influence of different types of additives on the properties of AAC and ALC

[0141]

[0142]

[0143] As can be seen from Table 1, for AAC, when the additive type is aerogel@MIL-53(Al), the compressive strength increases by 65.7% because Al 3+ forms ≡Al-O-Si bonds with the silicate matrix, strengthening the structure of the pore walls.

[0144] For ALC, when the additive type is aerogel@UiO-66, the strength of ALC increases by 55.8% because the Zr-O bond combines with the silanol groups on the surface of the ceramsite, enhancing the aggregate-paste interface.

[0145] In terms of thermal conductivity, the additive of the aerogel@UiO-66 type makes the thermal conductivity of AAC as low as 0.09 W / m · K, which is better than the ALC group.

[0146] The comparison of durability is shown in Table 2:

[0147] Table 2: Influence of different types of additives on the durability of AAC and ALC

[0148] Concrete type Additive type Water absorption rate (24h, %) <![CDATA[Chloride ion diffusion coefficient (×10 -12 m 2 / s)]]> AAC Blank aerogel 45±3 4.5±0.6 AAC Aerogel@MIL-53(Al) 28±2 1.2±0.2 AAC Aerogel@UiO-66 25±1 0.8±0.1 ALC Blank aerogel 38±2 3.8±0.4 ALC Aerogel@MIL-53(Al) 22±1 1.0±0.1 ALC Aerogel@UiO-66 18±1 0.6±0.05

[0149] As can be obtained from Table 2, in this embodiment, adding the additive of the aerogel@UiO-66 type further reduces the chloride ion diffusion coefficient of ALC to 0.6×10 -12 m 2 / s; It can be seen that the flexible pores of the aerogel@MIL-53(Al) provided by the present invention shrink during autoclaving, squeezing the pore walls to densify the structure and improve the strength; the Zr6O4(OH)4 clusters of aerogel@UiO-66 dehydrate and condense with the surface —Si—OH of the ceramsite to form Zr—O—Si covalent bonds, significantly enhancing the interfacial bonding strength. The aerogel fills the large pores between the ceramsites, and the mesopores of the MOF block the capillary water seepage path, resulting in a significant reduction in the water absorption rate.

[0150] Example 6

[0151] This example illustrates the influence of additives on the properties of concrete.

[0152] Control group: Commercially available ordinary autoclaved aerated concrete (without adding aerogel@MOF composite material);

[0153] Experimental group: An additive of the type aerogel@MIL-53(Al) prepared according to the formula of Example 3;

[0154] Test standard: GB / T 11969-2020 "Test Methods for Properties of Autoclaved Aerated Concrete".

[0155] The test results are shown in Table 3:

[0156] Table 3: Influence of additives on the properties of concrete

[0157] Performance indicators Control group Experimental group <![CDATA[Dry density (kg / m 3 )]]> 650±20 580±15 Compressive strength (MPa) 3.5±0.3 4.8±0.4 Thermal conductivity (W / m·K) 0.16±0.02 0.12±0.01 Water absorption rate (24h, %) 45±3 28±2

[0158] It can be seen that the nano-pores of the aerogel@MOF composite material reduce the density of the concrete and improve the thermal insulation performance; the interfacial bonding between the MOF skeleton and the silicate matrix enhances the mechanical properties; the functionalization of the silane coupling agent inhibits water penetration and significantly reduces the water absorption rate.

[0159] Example 7

[0160] This example is intended to illustrate the influence of additives of adding MOF materials alone and adding silica aerogel alone on the quality of AAC blocks.

[0161] This example designs six experimental groups:

[0162] Blank control group: Autoclaved aerated concrete prepared without additives;

[0163] MOF alone group: Autoclaved aerated concrete prepared by adding 5% of an additive of the type pure MIL-53(Al);

[0164] Aerogel alone group: Autoclaved aerated concrete prepared by adding 5% of an additive of the type pure silica aerogel;

[0165] Physical mixture group: Autoclaved aerated concrete prepared by adding 2.5% additives of type MOF and 2.5% additives of type aerogel (not in-situ composite);

[0166] Composite material group: Autoclaved aerated concrete prepared by adding 5% additives of type aerogel@MIL-53(Al) in Example 1;

[0167] Commercially available AAC group: Commercially available autoclaved aerated concrete (density 650 kg / m 3 , compressive strength 3.5 MPa).

[0168] According to the AAC standard formula (cement 30%, quartz sand 60%, gypsum 5%, additive 5%), with a water-to-material ratio of 0.6, prepare AAC blocks with the above six groups of experimental additives. Measure indicators such as 28-day compressive strength and chloride ion diffusion coefficient according to national standards. The test results are shown in the following table:

[0169] Table 4: Influence of individual material additives on the comprehensive properties of AAC blocks

[0170]

[0171] The data in Table 4 show that the composite material group exhibits significant advantages in the application of autoclaved aerated concrete: its compressive strength reaches 5.6 ± 0.4 MPa, a 47% increase compared to the blank control group, and is higher than the groups with individual addition of MOF or aerogel, indicating that the in-situ composite of silica aerogel and MOF produces a synergistic strengthening effect; the chloride ion diffusion coefficient is as low as 1.2×10 -12 m 2 / s, a 71% decrease compared to the blank group, which benefits from the adsorption and locking effect of the high specific surface area of MOF on corrosive ions and the blocking of the penetration path by the nano-pores of the aerogel; the dry density of the composite material group is 560 ± 8 kg / m 3 , mainly due to the dual weight reduction effects of the low-density skeleton of the aerogel and the mesoporous structure of MOF. At the same time, the composite material is strengthened by the interfacial bonding of the silane coupling agent KH-550, and finally the autoclaving pressure requirement is reduced to 0.8 MPa, a 38% reduction compared to the commercially available AAC group. The performance gap between the physical mixture group and the composite material group reveals that the in-situ hydrothermal synthesis process enables MOF to form chemical bonding within the pores of the aerogel, avoiding interface defects during simple physical mixing, thereby more effectively improving the durability and mechanical properties of concrete.

[0172] Example 8

[0173] This example aims to illustrate the role of aerogel@MOF composite materials treated with amino-functionalized ionic liquids in the production of ACC and ALC.

[0174] 1. Experimental design:

[0175] This embodiment designs four groups of experimental groups:

[0176] Group 1: The additive prepared from aerogel@MIL-53(Al) treated with amino-functionalized ionic liquid, and the produced AAC;

[0177] Group 2: The additive prepared from aerogel@MIL-53(Al) not treated with amino-functionalized ionic liquid, and the produced AAC;

[0178] Group 3: The additive prepared from aerogel@MIL-53(Al) treated with amino-functionalized ionic liquid, and the produced ALC;

[0179] Group 4: The additive prepared from aerogel@MIL-53(Al) not treated with amino-functionalized ionic liquid, and the produced ALC.

[0180] The preparation process and conditions of the concrete are the same as those in Example 5.

[0181] 2. Performance test results:

[0182] The data table for the performance impact on AAC is shown in Table 5:

[0183] Table 5: AAC Performance Comparison

[0184]

[0185]

[0186] The data table for the performance impact on ALC is shown in Table 6:

[0187] Table 6: ALC Performance Comparison

[0188] Index Group 4 Group 3 Compressive strength (MPa) 6.0±0.4 7.5±0.5 <![CDATA[Fracture energy (J / m 2 )]]> 55±4 65±4 Water absorption rate (24h, %) 22±1 18±1

[0189] It can be seen from Tables 5 to 6 that the present invention enhances the interfacial bonding and hierarchical pore structure of the aerogel@MOF composite material through amino-functionalized ionic liquid (NH2-IL), and combines the chemical stability and function tunability of aluminum-based (MIL-53(Al)) and zirconium-based (UiO-66) MOFs, significantly improving the compressive strength, heat preservation and durability of autoclaved aerated concrete (AAC) and autoclaved lightweight concrete (ALC).

[0190] Example 9

[0191] In this example, the performance differences of MOF composites prepared from zinc-based (ZIF-8), copper-based (HKUST-1), and chromium-based (MIL-101(Cr)) are compared with the aluminum-based (MIL-53(Al)) and zirconium-based (UiO-66) MOF composites preferred in the present invention as additives in AAC and ALC to verify the superiority of the MOF selection in the present invention.

[0192] 1. Experimental design

[0193] Preparation of aerogel@MOF composites:

[0194] Aerogel@ZIF-8: The aerogel was immersed in a methanol solution of zinc nitrate (0.1 M) and 2-methylimidazole (0.4 M), and reacted at room temperature for 24 h.

[0195] Aerogel@HKUST-1: The aerogel, copper nitrate (0.05 M), and trimesic acid (0.03 M) were hydrothermally treated in DMF at 80 °C for 12 h.

[0196] Aerogel@MIL-101(Cr): The aerogel, Cr(NO3)3·9H2O (0.02 M), terephthalic acid (0.01 M), and HF (0.05 M) were hydrothermally treated at 220 °C for 48 h.

[0197] Aerogel@MIL-53(Al): Prepared by the method of Example 1.

[0198] Aerogel@UiO-66: The method of Example 1 was replaced with ZrCl4 and terephthalic acid, and hydrothermally treated at 120 °C for 24 h.

[0199] All groups were subjected to ball milling treatment, and the preparation process and conditions of the concrete were the same as those in Example 5.

[0200] 2. Performance test results:

[0201] Test standard: GB / T 11969-2020 "Test Methods for Performance of Autoclaved Aerated Concrete"; its influence on the performance of AAC is shown in Table 7:

[0202] Table 7: Influence of different types of additives on the performance of AAC

[0203]

[0204] As can be seen from Table 7, MIL-53(Al) has the best strength in AAC: the compressive strength is 6.85 MPa, far exceeding other MOF groups, because Al3+ forms ≡Al-O-Si bonds with silicate, enhancing the pore wall structure.

[0205] The zirconium-based MOF (UiO-66) has the best durability in AAC: the chloride ion diffusion coefficient is as low as 0.8×10-12 m2 / s, because the Zr-O bond has stronger alkali resistance.

[0206] Table 8 statistically illustrates the effects of different types of additives on ALC:

[0207] Table 8: Performance effects of different types of additives on ALC

[0208] Additive type Compressive strength (MPa) <![CDATA[Fracture energy (J / m 2 )]]> Water absorption rate (24h, %) Aerogel@ZIF-8 6.0±0.4 55±4 25±2 Aerogel@HKUST-1 5.5±0.3 50±3 28±3 Aerogel@MIL-101(Cr) 7.2±0.5 60±5 20±1 MIL-53(Al)@Aerogel 7.5±0.5 65±4 18±1 Aerogel@UiO-66 8.1±0.6 68±4 18±1

[0209] As can be seen from Table 8, the ALC prepared with the additive type of zirconium-based MOF (UiO-66) has the best comprehensive performance: compressive strength of 8.1 MPa, fracture energy of 68 J / m 2 , and its Zr-O bond condenses with the silanol groups (—Si—OH) on the surface of the ceramsite, increasing the interfacial bonding strength by 40%; the ALC prepared with the additive type of chromium-based MOF (MIL-101(Cr)) may be due to Cr 3+ partially dissolves in the alkaline environment, weakening the structural stability. For the ALC prepared with the additive type of ZIF-8, Zn 2+ has poor compatibility with silicate, and the interface is easily peeled off, resulting in a strength of only 3.2 MPa, which is only 47% of the aluminum-based group; while for the ALC prepared with the additive type of HKUST-1, it may be due to Cu 2+ being oxidized to form CuO in the alkaline environment, destroying the MOF structure and having poor structural stability; while the ALC prepared with the additive type of MIL-101(Cr) has a high specific surface area, but Cr 3+ toxicity and cost limit its industrial application.

[0210] In summary, the present invention preferably selects aerogel@composites prepared from aluminum-based (MIL-53(Al)) and zirconium-based (UiO-66) MOFs. Through chemical bonding interface strengthening, hierarchical pore structure optimization and functional integration design, it realizes an increase in compressive strength in AAC and ALC, and all durability indicators are comprehensively superior to traditional and other MOF systems. At the same time, it reduces the comprehensive cost and promotes the upgrading of the concrete industry towards high performance, low energy consumption and greenness.

[0211] As described above, the basic principles, main features and advantages of the present invention are preferably described. The above embodiments and descriptions are only for describing the preferred embodiments of the present invention. The present invention is not limited by the above embodiments. Without departing from the spirit and scope of the present invention, various changes and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the present invention.

Claims

1. An aerogel@MOF composite material, characterized in that: The aerogel@MOF composite material is a composite of a silicon dioxide aerogel and a metal organic framework material, and the metal organic framework material is an aluminum-based MOF material or a zirconium-based MOF material.

2. An aerogel@MOF composite material according to claim 1, characterized in that: The aluminum-based MOF material is MIL-53 (Al) or CAU-10-H; the zirconium-based MOF material is UiO-66 or UiO-67.

3. A method for preparing the aerogel@MOF composite material according to claim 1, characterized in that: The following steps are involved: Step 1: preparing silica aerogel, comprising the following steps: Step 101, mix tetraethyl orthosilicate, ethanol, and deionized water in a molar ratio of 1:(3-5):(3-5), add hydrochloric acid to adjust the pH to 2-3, stir and hydrolyze for 30 minutes to obtain a hydrolyzate; Step 102, adding methyltrimethoxysilane to the hydrolyzate obtained in step 101, adjusting the pH to 5-6 and then standing for gelation to obtain a gel product; the molar ratio of ethyl orthosilicate to methyltrimethoxysilane is 3:2-7:3; Step 103, soaking the gel product obtained in step 102 in an ethanol solvent, and then drying it by supercritical CO2 to obtain a silica aerogel; Step 2: In-situ synthesis of aerogel@MOF composite material, comprising the following steps: Step 201, dissolving a metal salt in a mixed solvent of an amino-functionalized ionic liquid and deionized water to obtain a metal salt solution; Step 202, dissolving the organic ligand in a mixed solvent of an amino-functionalized ionic liquid and DMF to obtain a ligand solution; Step 203, mixing the metal salt solution obtained in step 201 and the ligand solution obtained in step 202 at a volume ratio of 1:1 to obtain a mixed solution; Step 204, adding the silica aerogel to the mixed solution obtained in step 203, performing a hydrothermal reaction, and obtaining a composite material; Step 3: post-processing and functionalizing the composite material obtained in step 204, comprising the following steps: Step 301, collecting the composite material obtained in step 204 by centrifugation, washing with DMF and ethanol alternately, and drying to obtain a dry composite material; Step 302, soaking the dried composite material obtained in step 301 in a NaOH solution to obtain an activated composite material; Step 303: immerse the activated composite material obtained in step 302 in an ethanol solution of silane coupling agent KH-550, and grind it in a ball mill after curing to obtain an aerogel@MOF composite material.

4. The preparation method according to claim 3, characterized in that: The volume ratio of the amino-functionalized ionic liquid to deionized water in step 201 is 1:4; the volume ratio of the amino-functionalized ionic liquid to DMF in step 202 is 1:3; the mass concentration of the ethanol solution of the silane coupling agent KH-550 in step 303 is 1 to 3wt%, and the curing conditions are immersion at 60 to 100°C for 0.5 to 2 hours; the grinding speed of the ball mill is 100 to 300rpm, the ball milling medium is zirconia beads, and the grinding time is 5 to 15 minutes.

5. Application of an aerogel@MOF composite material in the preparation of autoclaved aerated or autoclaved lightweight concrete additives.

6. An additive according to claim 5, characterized in that The additive is composed of the following components in percentage by mass: 25-30% aerogel@MOF composite material, 3-5% hydrogen peroxide, 3-5% polycarboxylic acid water reducer, 1.5-2% isobutyl triethoxy silane, 10-20% sodium metasilicate, 1.5-3% polypropylene fiber, 0.3-0.45% iron oxide catalyst, 0.6-1% citric acid, and 45-55% water.

7. The additive according to claim 6, characterized in that The mass concentration of the hydrogen peroxide is 30%; the polycarboxylate water reducer is an alkali-resistant polycarboxylate water reducer, and the molecular weight of the polycarboxylate water reducer is 5000-20000 g / mol.

8. The additive according to claim 6, characterized in that The polypropylene fiber is subjected to surface modification treatment, wherein the modifier in the surface modification is a silane coupling agent or a titanate coupling agent, and the length of the polypropylene fiber is 3 to 12 mm.

9. A method for preparing the additive according to any one of claims 6 to 8, characterized in that: The following steps are involved: Step 1: pretreating the additive component, comprising the following steps: Step 101, soaking the polypropylene fiber in a 5% silane coupling agent KH-550 ethanol solution for 30 minutes, and then drying at 60° C. to obtain modified polypropylene fiber; Step 102, mixing the polycarboxylate water-reducing agent and silica fume in a mass ratio of 1:2, and spray-drying to prepare a polycarboxylate water-reducing agent powder of 50-100 μm; Step 103, pre-mixing the aerogel@MOF composite material and sodium metasilicate and grinding them to a particle size of 20 μm to obtain a ground dry material; Step 104, premixing the hydrogen peroxide with citric acid, adjusting the pH to 4.5-5.0, to obtain stable hydrogen peroxide; Step 2: Start the high-speed mixer to perform dry mixing, including the following steps: Step 201, start the high-speed mixer, preheat it to 30° C., put the ground dry material and modified polypropylene fiber into the high-speed mixer, mix for 20 minutes, and obtain a premixed dry material; Step 202, spraying isobutyltriethoxysilane into the premixed dry material obtained in step 201, mixing for 15 minutes to obtain a completely mixed dry material; Step 3, wet mixing the completely mixed dry materials in step 202, including the following steps: Step 301, heating 30% of water to 25°C, adding the polycarboxylate water-reducing agent powder and stirring until completely dissolved, injecting into the high-speed mixer, stirring at a low speed of 500 rpm for 10 minutes to obtain a pre-wetted mixture; Step 302, adding the stabilized hydrogen peroxide obtained in step 104 to the pre-moistened dry material obtained in step 301, and monitoring the temperature; Step 303: When the temperature monitored in step 302 exceeds 30°C, add 30% water, increase the speed to 1200 rpm, and continue to monitor the temperature; Step 304: When the temperature monitored in step 303 exceeds 30°C, add 30% water and continue stirring for 10 minutes; Step 305: Add the iron oxide catalyst into the high-speed mixer, add the remaining water, and continue stirring to obtain the additive.

10. The method according to claim 9, characterized in that The inlet temperature of the spray drying in step 102 is 150-180° C., the outlet temperature is 60-80° C., and the atomization pressure is 0.3-0.5 MPa.

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