Cement-based composite material based on in-situ growth of Ca-MOF and preparation method thereof

Abstract

The present invention discloses a cement-based composite material based on in-situ growth of Ca-MOF and a preparation method thereof, and belongs to the technical field of preparation of cement-based materials. The preparation method comprises the following steps: mixing a calcium source solution with an organic ligand solution to obtain a MOF pre-assembly solution; adding the MOF pre-assembly solution into a cement-based material, stirring evenly, and then curing and forming to obtain a cement-based composite material based on in-situ growth of Ca-MOF. The present invention combines the in-situ generation of MOF materials in a cement environment with cement hydration. The generation of hydration products not only provides physical support for MOF assembly, but also creates a suitable alkaline environment to promote the in-situ growth of MOF. The cement-based composite material prepared by the present invention has high mechanical strength. The preparation process of the present invention is green and low-carbon, significantly reduces cost and energy consumption, realizes the beneficial combination of metals, inorganic substances and organic substances, and shows excellent application potential and development prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of preparation of cement-based materials, and in particular to a cement-based composite material based on in-situ growth of Ca-MOF and a preparation method thereof. Background Art

[0002] In recent years, nano- and micron-sized particles have been used as cement reinforcement materials and have attracted much attention because they can significantly improve the key properties of cement-based composites. The size of these particles usually ranges from nanometers to micrometers. Due to their high specific surface area and high surface energy, nanomaterials can effectively improve the mechanical strength of cement-based materials at low concentrations. As early as 1964, studies have shown that silica fume particles can promote the hydration reaction of aluminate cement and the consumption of sulfate. With the deepening of research, it was found that the addition of ultrafine particles such as silicon, aluminum oxide, iron oxide, titanium oxide, graphene and carbon nanotubes to cement or concrete can further improve the application performance of the material. In addition, adding larger particle size powders such as waste glass powder, carbonized peanut shells, coal fly ash and other industrial by-products to cement-based materials at a higher proportion (usually more than 10%) can not only enhance the application performance of cement-based materials, but also reduce manufacturing costs. The reinforcing effects of these micron / nanoparticles on cement-based composites are mainly reflected in the following aspects: first, they provide nucleation sites for the growth of hydration products and promote the dissolution of cement particles; second, particles with pozzolanic activity can generate more cement phase; finally, these particles can fill the voids in the hardened slurry, connect the various components, reduce the porosity, and thus enhance the overall strength of the cement-based material.

[0003] Patent CN117843280A (publication date: April 9, 2024) reports a concrete early strength agent and its preparation method. The method uses saponin extract and catechin to prepare the concrete early strength agent. The formula is simple and can increase the one-day compressive strength of concrete by more than 29.6%. The effect of improving the early strength of concrete is significant, and the application range of saponin extract and catechin is broadened. However, saponin extract and catechin are more expensive than traditional early strength agent raw materials, which greatly increases the production cost of the concrete early strength agent. In addition, the process of extracting saponin and catechin will have a certain impact on the environment, and it is difficult to ensure the sustainable production and application of the early strength agent.

[0004] Patent CN117126341A (publication date: November 28, 2023) reports a concrete early strength agent and its preparation method. The method utilizes phosphine-terminated hyperbranched polyether, polyethylene glycol and carboxylic acid condensation product, unsaturated sulfonic acid monomer, unsaturated amide monomer, unsaturated acid anhydride, soluble calcium source, dispersant, pH regulator, initiator and water to significantly improve the early strength of concrete and also has the effect of reducing water. The synthesis process is not complicated, the cost is low, and the practicality is strong. However, the organic matter in the raw materials is of various types and the synthesis steps are cumbersome, which is not conducive to subsequent production applications.

[0005] Patent CN115611578A (publication date: September 19, 2023) reports an early-strength, low-shrinkage MOF dry-mix mortar and its preparation method. This method utilizes agricultural solid waste, natural sand, MOF materials, fibers, water reducers and other materials, and coordinates the various components. Compared with traditional mortar, the mortar prepared by this method has significantly improved early strength, while also further reducing the shrinkage performance of the mortar and improving its carbonization resistance. However, this method requires too many and complex raw materials, is costly, and has limited use conditions. It is not applicable to concrete. In addition, the MOF materials need to be synthesized separately, the overall process is cumbersome, and the preparation cycle is long.

[0006] The early strength agent mentioned in the above patent has shown certain effects in reducing the shrinkage and carbonization resistance of cement-based materials. However, the preparation method of its early strength agent and its application in concrete still have shortcomings. In the process of seeking excellent early strength effects, the operating methods adopted by current researchers are relatively complicated, which is not conducive to large-scale promotion and application. At the same time, its research and development ideas are still limited to coordinating the proportions of various components, or introducing organic substances such as polyethers and polycarboxylic acids, and innovations in molecular structure design and other aspects need to be broken through. In addition, in terms of innovative design of early strength mechanisms, most researchers are still limited to adding materials such as fibers and solid wastes, and increasing nucleation sites through physical effects to achieve early strength effects; or using organic substances such as polycarboxylic acids, polyethers, and unsaturated anhydrides to promote the dispersion of cement particles in cement hydration, participate in the chemical reaction of cement hydration, thereby accelerating the hydration reaction of cement and achieving the effect of improving early strength. In recent years, metal-organic frameworks (MOFs) have gained increasing attention for their application in cementitious materials due to their excellent adsorption properties and high specific surface area. However, current researchers have only managed to improve the performance of cementitious materials by adjusting the ratio of MOF materials to their respective components. Furthermore, these complex methods hinder large-scale promotion and application, and thus fail to fully realize the potential of MOF materials. Therefore, finding simple ways to enhance the performance of MOF materials on cementitious materials is a current research priority for those skilled in the art. Summary of the Invention

[0007] The present invention aims to provide a cement-based composite material based on in-situ growth of Ca-MOF and a preparation method thereof to address the problems existing in the above-mentioned prior art. The preparation method mainly uses an organic ligand, a calcium source, and a paste, mortar, or concrete as raw materials. First, the calcium source and the organic ligand are fully dissolved and mixed to form a MOF pre-assembled solution. Then, the MOF pre-assembled solution is incorporated into freshly mixed paste, mortar, or concrete and cured and formed to obtain a cement-based composite material based on in-situ growth of Ca-MOF.

[0008] To achieve the above object, the present invention provides the following solutions:

[0009] One of the technical solutions of the present invention: a method for preparing a cement-based composite material based on in-situ growth of Ca-MOF, comprising the following steps:

[0010] A calcium source solution and an organic ligand solution are mixed to obtain a MOF pre-assembly solution; the MOF pre-assembly solution is added to a cement-based material, stirred evenly, and then cured and formed to obtain the cement-based composite material based on in-situ growth of Ca-MOF.

[0011] Based on the in-situ generation preparation concept, the present invention combines the self-assembly of MOF materials with the cement hydration process. After cement and water are mixed, minerals such as silicates and aluminates in the cement clinker begin to react with water to form hydration products such as calcium silicate hydrate and calcium aluminate hydrate. These hydration products not only provide physical support for the cement-based composite material but also create an alkaline chemical environment, which provides ideal conditions for the self-assembly of MOF materials. In this alkaline environment, pre-dispersed metal ions and organic ligands, under the action of free water, form the primary structural units of MOFs through coordination bonds. Subsequently, under the interaction of intermolecular hydrogen bonds, π-π stacking, and van der Waals forces, they gradually grow and assemble into MOF materials with highly ordered porous structures. These MOF materials grow on the surface or between the layers of cement hydration products. Due to their high specific surface area and other properties, they not only provide new nucleation sites for the hydration products, but also possess the adsorption properties of MOF materials, achieving a "clustering effect" on pore fluid ions, thereby accelerating the hydration process. As cement hydration and MOF self-assembly proceed, the in-situ generated MOF nanoparticles are evenly dispersed within the cementitious composite matrix and exert their effects, effectively enhancing the early-life strength of the cementitious composite. This approach demonstrates a more innovative design concept than traditional cementitious materials, resulting in superior early-life strength and a greener development prospect.

[0012] Furthermore, the step of preparing the calcium source solution includes: mixing a calcium source and water and stirring for 5-15 minutes to obtain the calcium source solution;

[0013] And / or, the step of preparing the organic ligand solution includes: mixing the organic ligand and a co-solvent to obtain the organic ligand solution.

[0014] Furthermore, the calcium source is calcium nitrate tetrahydrate, calcium acetate or calcium chloride;

[0015] And / or, the mass ratio of the calcium source to water is 1:10-40.

[0016] Furthermore, the mixing and stirring of the calcium source and water for 5-15 minutes includes: the mixing and stirring is performed at room temperature.

[0017] Furthermore, the preparation step of the cosolvent comprises: mixing one or both of the alkaline substance and the organic solvent with water and stirring for 10-20 minutes to obtain the cosolvent;

[0018] and / or, the alkaline substance is sodium hydroxide, potassium hydroxide, sodium bicarbonate, sodium carbonate, potassium carbonate or ammonia water;

[0019] And / or, the organic solvent is anhydrous ethanol, N,N-dimethylacetamide, methanol or isopropanol.

[0020] Furthermore, the concentration of the ammonia water is 25-28 wt%.

[0021] Furthermore, when the alkaline substance is mixed with water and stirred for 10-20 minutes to obtain a cosolvent, the mass ratio of the alkaline substance to water is 1-20:80;

[0022] When the organic solvent and water are mixed and stirred for 10-20 minutes to obtain a cosolvent, the mass ratio of the organic solvent to water is 5-10:40;

[0023] When the alkaline substance, the organic solvent and water are mixed and stirred for 10-20 minutes to obtain a cosolvent, the mass ratio of the alkaline substance, the organic solvent and the water is 0.2-20:5-20:30-90.

[0024] Furthermore, the mixing and stirring of the alkaline substance, the organic solvent and the water for 10-20 minutes includes: the mixing and stirring is performed at 30-50°C.

[0025] Furthermore, the mixing of the organic ligand and the cosolvent to obtain the organic ligand solution comprises: mixing the organic ligand and the cosolvent and stirring for 15-30 minutes to obtain the organic ligand solution;

[0026] and / or, the organic ligand is 1,4-benzenedicarboxylic acid, trimesic acid, gallic acid, phenylboronic acid, 9-fluorenone-2,7-dicarboxylic acid, fumaric acid, squaric acid or 1,4-naphthalene dicarboxylic acid;

[0027] And / or, the mass ratio of the organic ligand to the cosolvent is 1:50-100.

[0028] Furthermore, the mixing and stirring of the organic ligand and the co-solvent for 15-30 minutes includes: the mixing and stirring is carried out at 25-40°C.

[0029] Furthermore, the mixing of the calcium source solution and the organic ligand solution to obtain the MOF pre-assembly solution comprises: mixing the calcium source solution and the organic ligand solution and stirring for 3-15 minutes, and then ultrasonically treating for 5-10 minutes to obtain the MOF pre-assembly solution;

[0030] And / or, the molar ratio of the organic ligand contained in the organic ligand solution to the calcium source contained in the calcium source solution is 0.3-1:1.

[0031] Furthermore, the mixing and stirring of the calcium source solution and the organic ligand solution for 3-15 minutes includes: the mixing and stirring is performed at room temperature.

[0032] Furthermore, the cement-based material includes paste, mortar or concrete.

[0033] Furthermore, the adding of the MOF pre-assembly solution into the cement-based material comprises: the ratio of the mass of the MOF pre-assembly solution to the mass of the gelling material contained in the cement-based material is 1:10-20.

[0034] Furthermore, the raw materials of the mortar include a cementitious material, a water reducing agent, sand and water, and the cementitious material is cement, fly ash and mineral powder;

[0035] Alternatively, the raw materials of the concrete include cementitious materials, water reducing agent, sand, gravel and water, and the cementitious materials are cement, fly ash and mineral powder.

[0036] Furthermore, the cement-based material is mortar, and the MOF pre-assembly solution is added to the cement-based material, stirred evenly, and then cured and formed to obtain a cement-based composite material based on in-situ growth of Ca-MOF, including: mixing a portion of the MOF pre-assembly solution, a water reducer, cement, and a portion of water to obtain a mixture A; mixing the remaining MOF pre-assembly solution, fly ash, mineral powder, and the remaining water to obtain a mixture B; mixing the mixture A, mixture B, and sand at room temperature for 20-40 minutes, and then curing and forming;

[0037] Alternatively, the cement-based material is concrete, and the MOF pre-assembled solution is added to the cement-based material, stirred evenly, and then cured and formed to obtain a cement-based composite material based on in-situ growth of Ca-MOF, including: mixing part of the MOF pre-assembled solution, a water reducer, cement, and part of the water to obtain a mixture A; mixing the remaining MOF pre-assembled solution, fly ash, mineral powder, and the remaining water to obtain a mixture B; mixing the mixture A, mixture B, sand, and gravel at room temperature for 20-40 minutes, and then curing and forming.

[0038] Furthermore, the water reducer is a polycarboxylate water reducer.

[0039] Furthermore, the mass of the MOF pre-assembled solution in the mixture A is 3-10% of the mass of the cement;

[0040] And / or, the mass of the MOF pre-assembly solution in the mixture B is 5-15% of the sum of the mass of the fly ash and the mineral powder.

[0041] Furthermore, the mass of the polycarboxylate water-reducing agent in the mixture A is 0.6% of the mass of the cement, and the mass of water is 15-30% of the mass of the cement;

[0042] And / or, the mass of water in the mixture B is 20-40% of the sum of the mass of fly ash and mineral powder.

[0043] Furthermore, the sum of the masses of the cementitious materials in the mixture A and the mixture B is 30-50% of the mass of the sand.

[0044] And / or, the sum of the masses of the cementitious materials in the mixture A and the mixture B is 40-80% of the mass of the gravel.

[0045] Furthermore, the curing and molding process selects conventional curing methods and conditions for cement-based composite materials in the art according to the application site of the cement-based composite material based on in-situ growth of Ca-MOF and the performance requirements of the molded product.

[0046] Furthermore, the preparation method of the cement-based composite material based on in-situ growth of Ca-MOF more specifically comprises the following steps:

[0047] (1) Preparation of calcium source solution: Mix the calcium source and water at room temperature and stir for 5-15 minutes to obtain a calcium source solution;

[0048] (2) Preparation of a cosolvent: mixing an alkaline substance, an organic solvent, and water at 30-50° C. and stirring for 10-20 minutes to obtain a cosolvent;

[0049] (3) Preparation of an organic ligand solution: mixing the organic ligand and the cosolvent obtained in step (2) at 25-40° C. and stirring for 15-30 minutes to obtain an organic ligand solution;

[0050] (4) Preparation of MOF preassembly solution: The calcium source solution obtained in step (1) and the organic ligand solution obtained in step (3) were mixed and stirred at room temperature for 3-15 minutes, and then ultrasonically treated for 5-10 minutes to obtain a MOF preassembly solution;

[0051] (5) Preparation of cement-based composite materials based on in-situ growth of Ca-MOF: After obtaining the MOF pre-assembly solution, the MOF pre-assembly solution and the cement-based material are immediately mixed and stirred at room temperature for 20-40 minutes, and then cured and formed to obtain a cement-based composite material based on in-situ growth of Ca-MOF.

[0052] The specific mixing order can improve the MOF conversion rate and reduce the probability of side reactions after mixing the MOF pre-assembled solution with cement-based materials.

[0053] Furthermore, the structure of the Ca-MOF in the cement-based composite material based on in-situ growth of Ca-MOF (i.e., the coordination relationship between calcium ions and organic ligands) is as shown in Formula I or Formula II:

[0054]

[0055] Among them, R is C, R1 is R' is

[0056] The second technical solution of the present invention: a cement-based composite material based on in-situ growth of Ca-MOF prepared according to the above preparation method.

[0057] The present invention proposes a novel method for preparing cement-based composites, namely, in situ generation of MOF materials during the cement hydration process. This reduces the number and quantity of raw materials, especially organic matter, significantly improving raw material utilization, significantly simplifying the preparation process, and reducing costs. Because MOFs grow in situ in a solution environment within the cement pores, they achieve excellent bonding with the cement-based material, significantly improving the overall performance (such as mechanical properties) of the cement-based composite. During the preparation process, a MOF pre-assembled solution is mixed with freshly mixed paste, mortar, or concrete, and MOF self-assembly and cement hydration occur simultaneously. MOF self-assembly is a coordinated bonding between metal ions and organic ligands. The formation of Ca(OH)2 during cement hydration provides an alkaline environment for MOF self-assembly, meeting the pH and other conditions required for MOF assembly. Furthermore, as cement hydration proceeds, the heat released can meet the temperature and energy requirements for MOF assembly. Furthermore, water is used as a solvent during the preparation and curing of the cement-based composite, providing a suitable solvent for MOF assembly. Therefore, cement-based composites prepared using in-situ Ca-MOF growth can demonstrate excellent early strength, fully demonstrating process advantages, performance advantages, and cost advantages. This preparation method is simple, convenient, low-cost, and has excellent performance, with broad development prospects and significant application potential. However, research in this area has rarely been reported domestically or internationally.

[0058] The present invention discloses the following technical effects:

[0059] (1) The present invention is based on an in-situ generation strategy that integrates the self-assembly of MOF materials with the hydration process of cement. After cement is mixed with water, the silicon phase and aluminum phase minerals in the cement begin to undergo hydration reactions to generate hydration products such as hydrated calcium silicate and hydrated calcium aluminate. These products not only construct a physical framework, but also create an alkaline environment, providing suitable chemical conditions for the self-assembly and in-situ growth of MOF. In this alkaline environment, pre-dispersed metal ions and organic ligands, with the assistance of free water, form the basic structural units of MOF through coordination. These structural units then gradually expand and self-assemble into highly ordered porous MOF structures through interactions such as intermolecular hydrogen bonds, electrostatic forces, π-π stacking, and van der Waals forces. The nanoparticles of these MOF materials grow on the surface or between the layers of the cement hydration products. As the cement hydration and MOF self-assembly continue, the in-situ generated MOF nanoparticles are evenly distributed in the cement-based composite matrix, thereby obtaining a new type of cement-based composite material with excellent early strength and late strength based on the in-situ growth of Ca-MOF.

[0060] (2) The present invention utilizes the high specific surface area and large pore structure of MOF materials to enable them to effectively contact and interact with ions in the cement pore solution. By changing the type of organic ligands, the pore size and shape of MOF materials can be adjusted. The metal ions and organic ligands in MOF materials can form strong physical adsorption effects with ions in the cement pore solution, such as van der Waals forces, electrostatic effects, or hydrogen bonds. In addition, some metal sites in MOF materials are not completely surrounded by organic ligands. These open metal sites can serve as adsorption sites and form strong interactions with various free ions. The pore structure and chemical properties of MOF materials can be customized as needed, so that they exhibit selective adsorption effects on specific substances. Therefore, by in situ generation of Ca-MOF, its pore size can effectively adsorb various ions in the pore solution, accelerate the aggregation of ions, and increase the ion saturation in specific areas. This not only can quickly promote the dissolution-precipitation process of cement particles, thereby improving the early strength of cement-based materials, but also provides a new direction for the application expansion of MOF.

[0061] (3) The present invention also gives full play to the stability and durability advantages of MOF materials, significantly improving the application performance of cement-based composite materials. MOF materials grow in situ in the chemical environment of cement paste. In the initial stage, the assembled MOF can not only optimize the microstructure of cement-based composite materials, but the free metal ions and organic ligands can also realize specific chemical reactions or catalytic processes, induce the formation of amorphous hydrated calcium silicate products, and enhance the interfacial bonding strength between hydration products and aggregates. In addition, the formed MOF microparticles can promote the dissolution and precipitation process of cement particles and accelerate the hydration process. The high specific surface area and porous nature of MOF materials can provide nucleation sites, promote the formation and growth of hydration products, accelerate the cement hydration process, and promote the formation of hydration products. Nano- and micro-nano-scale MOF particles fill the pores of cement-based materials, reduce the macroporosity, increase the density, and thus improve the early strength of cement-based materials. During the curing process, the in-situ generated MOF partially decomposes, releasing organic ligands that form new coordination bonds with free calcium ions in the cement paste, forming new Ca-MOFs that act as a reinforcing phase, further enhancing the early strength of cement-based composites. The presence of MOFs also optimizes the type, morphology, and distribution of cement hydration products, which is crucial for improving the performance of cement-based composites. Therefore, different organic ligands can achieve fine-tuned control of the early strength of cement-based composites.

[0062] (4) Compared with the production process of chemical admixtures for cement concrete, the in situ generation of Ca-MOF is achieved by utilizing the chemical environment of cement during the hydration process of cement. The reaction raw materials are simple, and the preparation process is simple and controllable, which greatly reduces the additional synthesis steps and material waste. At the same time, no other ions are introduced during the self-assembly and in situ growth of MOF materials, and the organic ligands that fail to participate in the assembly can also undergo chelation with the free calcium ions in cement to form new Ca-MOF. Therefore, no by-products that affect the strength of cement-based materials are produced during the entire in situ generation process. This provides a new type of reinforcing material for cement-based composite materials and also provides innovative ideas for the development of new high-strength concrete.

[0063] (5) In engineering applications, the early strength of cement-based composites can be significantly improved by in-situ generation of Ca-MOF in cement-based composites. This new preparation process is not only energy-efficient, but also green and low-carbon, with high safety and significant application effects, thereby greatly improving the quality of construction projects. This method of in-situ generation of Ca-MOF can be applied to various freshly mixed pastes, mortars and concretes to achieve a beneficial combination of metals, inorganic substances and organic substances. This is an innovative achievement of the cross-integration of materials science, chemical engineering and civil engineering, and provides important ideas for the design, development and promotion of new building materials. It not only provides feasibility for improving the early strength, late strength and all-round functionalization of cement-based composites, but also promotes the breakthrough development of building functional materials, significantly improving economic benefits, social benefits and environmental benefits, and has huge market potential and promotion and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0065] Figure 1 These are infrared spectra of the cement-based composite material samples obtained after curing for 6 h and 24 h in Example 1 and Comparative Example 1, respectively. DETAILED DESCRIPTION

[0066] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0067] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0068] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0069] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0070] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0071] It should be pointed out that the matters not described in detail in the present invention are conventional operating means in this field and are not the focus of the present invention.

[0072] The room temperature involved in the specific implementation manner of the present invention specifically refers to 15-25°C.

[0073] The raw materials used in the following examples and comparative examples of the present invention are all common commercially available products, among which the polycarboxylate water reducer is purchased from China Building Materials Zhongyan Technology Co., Ltd., the cement is PO·42.5 ordinary Portland cement, the fly ash is first-class fly ash, the mineral powder is S105 mineral powder, the particle size of the stone is ≤5 mm, and the concentration of the ammonia water is 25 wt%.

[0074] The mass of Ca-MOF that can be generated after in-situ growth of the MOF pre-assembly solution involved in the following embodiments of the present invention is calculated based on the Ca-MOF conversion rate of the MOF pre-assembly solution of each embodiment (mass of Ca-MOF that can be generated after in-situ growth = mass of MOF pre-assembly solution × Ca-MOF conversion rate). The Ca-MOF conversion rate is obtained by the following method:

[0075] The MOF preassembly solution was heated and stirred at 50° C. until no more precipitate (i.e., Ca-MOF) was generated. The precipitate was separated and dried to obtain the mass of the generated Ca-MOF. The Ca-MOF conversion rate was calculated according to the formula: Ca-MOF conversion rate = mass of generated Ca-MOF / MOF preassembly solution × 100%.

[0076] Example 1

[0077] A method for preparing a cement-based composite material based on in-situ growth of Ca-MOF, comprising the following steps:

[0078] (1) Preparation of calcium source solution: 1.89 g (8.01 mmol) of calcium nitrate tetrahydrate and 20 g of deionized water were mixed and stirred at room temperature for 5 min to obtain a calcium source solution;

[0079] (2) Preparation of cosolvent: 0.4 g of sodium carbonate, 10 g of anhydrous ethanol, and 40 g of deionized water were mixed and stirred at 30°C for 15 min to obtain a cosolvent;

[0080] (3) Preparation of organic ligand solution: 0.88 g (7.22 mmol) of phenylboronic acid and the entire cosolvent obtained in step (2) were mixed and stirred at 30° C. for 15 min to obtain an organic ligand solution;

[0081] (4) Preparation of MOF preassembly solution: The entire calcium source solution obtained in step (1) and the entire organic ligand solution obtained in step (3) were mixed and stirred at room temperature for 15 minutes, and then ultrasonically treated for 10 minutes to obtain a MOF preassembly solution;

[0082] (5) Preparation of cement-based composites based on in-situ growth of Ca-MOF: After obtaining the MOF pre-assembled solution, 22.9 g of MOF pre-assembled solution (which can generate 0.25 g of Ca-MOF after in-situ growth), 2.7 g of polycarboxylate water reducer, 450 g of cement and 95 g of deionized water were immediately mixed to obtain mixture A. 18.3 g of MOF pre-assembled solution (which can generate 0.2 g of Ca-MOF after in-situ growth) was mixed with 18.3 g of MOF pre-assembled solution (which can generate 0.2 g of Ca-MOF after in-situ growth). Ca-MOF), 93g fly ash, 93g mineral powder and 62g deionized water were mixed to obtain mixture B; then, mixture A, mixture B and 1350g standard sand were immediately mixed and stirred at room temperature for 30min (the water-cement ratio of the final mixed system was calculated to be 0.3, wherein water was calculated as the sum of the mass of the deionized water contained in the MOF pre-assembly solution and the additionally added deionized water, and the glue was calculated as the sum of the mass of cement, fly ash and mineral powder) to obtain a mixture; according to the requirements of subsequent mechanical properties testing, the mixture was cured in a standard cement curing box (temperature of 20°C, humidity of 98-99%) for 24h using a mold of corresponding size to form it, and then immersed in a water tank at room temperature for 6 days or 27 days to obtain cement-based composite materials based on in situ growth of Ca-MOF with different curing times (referred to as mortar-based samples based on in situ growth of Ca-MOF). In addition, the mixture was cured in a standard cement curing box (temperature of 20° C., humidity of 98-99%) for 6 h or 24 h, and then taken out to obtain cement-based composite material samples for infrared testing.

[0083] Example 2

[0084] A method for preparing a cement-based composite material based on in-situ growth of Ca-MOF, comprising the following steps:

[0085] (1) Preparation of calcium source solution: 1.88 g (11.89 mmol) of calcium acetate and 30 g of deionized water were mixed and stirred at room temperature for 5 min to obtain a calcium source solution;

[0086] (2) Preparation of cosolvent: 18 g of ammonia water and 80 g of deionized water were mixed and stirred at 30° C. for 20 min to obtain a cosolvent;

[0087] (3) Preparation of organic ligand solution: 0.98 g (3.65 mmol) of 9-fluorenone-2,7-dicarboxylic acid and all the cosolvents obtained in step (2) were mixed and stirred at 30° C. for 20 min to obtain an organic ligand solution;

[0088] (4) Preparation of MOF preassembly solution: The entire calcium source solution obtained in step (1) and the entire organic ligand solution obtained in step (3) were mixed and stirred at room temperature for 10 minutes, and then ultrasonically treated for 10 minutes to obtain a MOF preassembly solution;

[0089] (5) Preparation of cement-based composites based on in-situ growth of Ca-MOF: After obtaining the MOF pre-assembled solution, 32.7 g of MOF pre-assembled solution (which can generate 0.25 g of Ca-MOF after in-situ growth), 2.7 g of polycarboxylate water reducer, 450 g of cement and 95 g of deionized water were immediately mixed to obtain mixture A. 26.2 g of MOF pre-assembled solution (which can generate 0.2 g of Ca-MOF after in-situ growth) was mixed with water. Ca-MOF), 93g fly ash, 93g mineral powder and 40.2g deionized water were mixed to obtain mixture B; then, mixture A, mixture B and 1350g standard sand were immediately mixed and stirred at room temperature for 30min (the water-cement ratio of the final mixed system was calculated to be 0.3) to obtain a mixture; according to the requirements of subsequent mechanical properties testing, the mixture was cured in a standard cement curing box (temperature of 20°C and humidity of 98-99%) for 24h using a mold of corresponding size to form it, and then immersed in a water tank at room temperature for 6 days or 27 days to obtain cement-based composite materials based on in situ growth of Ca-MOF with different curing times (recorded as mortar-based samples based on in situ growth of Ca-MOF).

[0090] Example 3

[0091] A method for preparing a cement-based composite material based on in-situ growth of Ca-MOF, comprising the following steps:

[0092] (1) Preparation of calcium source solution: 1.76 g (15.86 mmol) of calcium chloride and 20 g of deionized water were mixed and stirred at room temperature for 5 min to obtain a calcium source solution;

[0093] (2) Preparation of cosolvent: 0.71 g of sodium carbonate, 10 g of N,N-dimethylformamide, and 40 g of deionized water were mixed and stirred at 30° C. for 10 min to obtain a cosolvent;

[0094] (3) Preparation of organic ligand solution: 0.78 g (6.72 mmol) of fumaric acid and all the cosolvent obtained in step (2) were mixed and stirred at 30° C. for 15 min to obtain an organic ligand solution;

[0095] (4) Preparation of MOF preassembly solution: The entire calcium source solution obtained in step (1) and the entire organic ligand solution obtained in step (3) were mixed and stirred at room temperature for 10 minutes, and then ultrasonically treated for 10 minutes to obtain a MOF preassembly solution;

[0096] (5) Preparation of cement-based composites based on in-situ growth of Ca-MOF: After obtaining the MOF pre-assembled solution, 20.3 g of MOF pre-assembled solution (which can generate 0.25 g of Ca-MOF after in-situ growth), 2.7 g of polycarboxylate water reducer, 450 g of cement and 95 g of deionized water were immediately mixed to obtain mixture A. 16.3 g of MOF pre-assembled solution (which can generate 0.2 g of Ca-MOF after in-situ growth) was mixed with 100 g of cement and 100 g of deionized water. Ca-MOF), 93g fly ash, 93g mineral powder and 65.8g deionized water were mixed to obtain mixture B; then, mixture A, mixture B and 1350g standard sand were immediately mixed and stirred at room temperature for 30min (the water-cement ratio of the final mixed system was calculated to be 0.3) to obtain a mixture; according to the requirements of subsequent mechanical properties testing, the mixture was cured in a standard cement curing box (temperature of 20°C and humidity of 98-99%) for 24h using a mold of corresponding size to form it, and then immersed in a water tank at room temperature for 6 days or 27 days to obtain cement-based composite materials based on in situ growth of Ca-MOF with different curing times (recorded as mortar-based samples based on in situ growth of Ca-MOF).

[0097] Example 4

[0098] A method for preparing a cement-based composite material based on in-situ growth of Ca-MOF, comprising the following steps:

[0099] (1) Preparation of calcium source solution: 1.89 g of calcium nitrate tetrahydrate and 20 g of deionized water were mixed and stirred at room temperature for 5 min to obtain a calcium source solution;

[0100] (2) Preparation of cosolvent: 0.4 g of sodium carbonate, 10 g of anhydrous ethanol, and 40 g of deionized water were mixed and stirred at 30°C for 15 min to obtain a cosolvent;

[0101] (3) Preparation of organic ligand solution: 0.88 g of phenylboronic acid and all the cosolvents obtained in step (2) were mixed and stirred at 30° C. for 15 min to obtain an organic ligand solution;

[0102] (4) Preparation of MOF preassembly solution: The entire calcium source solution obtained in step (1) and the entire organic ligand solution obtained in step (3) were mixed and stirred at room temperature for 15 minutes, and then ultrasonically treated for 10 minutes to obtain a MOF preassembly solution;

[0103] (5) Preparation of cement-based composites based on in-situ growth of Ca-MOF: After obtaining the MOF pre-assembled solution, 22.9 g of MOF pre-assembled solution, 2.7 g of polycarboxylate water reducer, 450 g of cement and 95 g of deionized water were immediately mixed to obtain mixture A. 18.3 g of The MOF pre-assembly solution, 93 g of fly ash, 93 g of mineral powder and 62 g of deionized water were mixed to obtain mixture B; then, mixture A, mixture B, 1350 g of standard sand and 1016 g of gravel were immediately mixed and stirred at room temperature for 30 min (the water-cement ratio of the final mixed system was calculated to be 0.3) to obtain a mixture; according to the requirements of subsequent mechanical properties testing, the mixture was cured for 24 h in a standard cement curing box (temperature of 20°C and humidity of 98-99%) using a mold of corresponding size to form it, and then immersed in a water tank at room temperature for 6 days or 27 days to obtain cement-based composite materials based on in situ growth of Ca-MOF with different curing times (referred to as concrete-based samples based on in situ growth of Ca-MOF).

[0104] Example 5

[0105] A method for preparing a cement-based composite material based on in-situ growth of Ca-MOF, comprising the following steps:

[0106] (1) Preparation of calcium source solution: 1.88 g of calcium acetate and 30 g of deionized water were mixed and stirred at room temperature for 5 min to obtain a calcium source solution;

[0107] (2) Preparation of cosolvent: 18 g of ammonia water and 80 g of deionized water were mixed and stirred at 30° C. for 20 min to obtain a cosolvent;

[0108] (3) Preparation of organic ligand solution: 0.98 g of 9-fluorenone-2,7-dicarboxylic acid and all the cosolvents obtained in step (2) were mixed and stirred at 30° C. for 20 min to obtain an organic ligand solution;

[0109] (4) Preparation of MOF preassembly solution: The entire calcium source solution obtained in step (1) and the entire organic ligand solution obtained in step (3) were mixed and stirred at room temperature for 10 minutes, and then ultrasonically treated for 10 minutes to obtain a MOF preassembly solution;

[0110] (5) Preparation of cement-based composites based on in-situ growth of Ca-MOF: After obtaining the MOF pre-assembled solution, 32.7 g of MOF pre-assembled solution, 2.7 g of polycarboxylate water reducer, 450 g of cement and 95 g of deionized water were immediately mixed to obtain mixture A. 26.2 g of The MOF pre-assembly solution, 93 g of fly ash, 93 g of mineral powder and 40.2 g of deionized water were mixed to obtain mixture B; then, mixture A, mixture B, 1350 g of standard sand and 1016 g of gravel were immediately mixed and stirred at room temperature for 30 min (the water-cement ratio of the final mixed system was calculated to be 0.3) to obtain a mixture; according to the subsequent test requirements, the mixture was cured for 24 h in a standard cement curing box (temperature of 20°C and humidity of 98-99%) using a mold of corresponding size to form it, and then immersed in a water tank at room temperature for 6 days or 27 days to obtain cement-based composite materials based on in-situ growth of Ca-MOF with different curing times (referred to as concrete-based samples based on in-situ growth of Ca-MOF).

[0111] Example 6

[0112] A method for preparing a cement-based composite material based on in-situ growth of Ca-MOF, comprising the following steps:

[0113] (1) Preparation of calcium source solution: 1.76 g of calcium chloride and 20 g of deionized water were mixed and stirred at room temperature for 5 min to obtain a calcium source solution;

[0114] (2) Preparation of cosolvent: 0.71 g of sodium carbonate, 10 g of N,N-dimethylformamide, and 40 g of deionized water were mixed and stirred at 30° C. for 10 min to obtain a cosolvent;

[0115] (3) Preparation of organic ligand solution: 0.78 g of fumaric acid and all the cosolvents obtained in step (2) were mixed and stirred at 30° C. for 15 min to obtain an organic ligand solution;

[0116] (4) Preparation of MOF preassembly solution: The entire calcium source solution obtained in step (1) and the entire organic ligand solution obtained in step (3) were mixed and stirred at room temperature for 10 minutes, and then ultrasonically treated for 10 minutes to obtain a MOF preassembly solution;

[0117] (5) Preparation of cement-based composites based on in-situ growth of Ca-MOF: After obtaining the MOF pre-assembled solution, 20.3 g of MOF pre-assembled solution, 2.7 g of polycarboxylate water reducer, 450 g of cement and 95 g of deionized water were immediately mixed to obtain mixture A. 16.3 g of The MOF pre-assembly solution, 93 g of fly ash, 93 g of mineral powder and 65.8 g of deionized water were mixed to obtain mixture B; then, mixture A, mixture B, 1350 g of standard sand and 1016 g of gravel were immediately mixed and stirred at room temperature for 30 minutes (the water-cement ratio of the final mixed system was calculated to be 0.3) to obtain a mixture; according to the requirements of subsequent tests, the mixture was cured in a standard cement curing box (temperature of 20°C and humidity of 98-99%) for 24 hours using a mold of corresponding size to form it, and then immersed in a water tank at room temperature for 6 days or 27 days to obtain cement-based composite materials based on in-situ growth of Ca-MOF with different curing times (referred to as concrete-based samples based on in-situ growth of Ca-MOF).

[0118] Comparative Example 1

[0119] 450g of cement, 2.7g of polycarboxylate water reducer, 1350g of standard sand, 93g of fly ash, 93g of mineral powder, and 190.8g of deionized water (calculated to have a water-cement ratio of 0.3) were mixed and stirred at room temperature for 30 minutes to obtain a mixture. According to the requirements of subsequent mechanical properties testing, the mixture was cured for 24 hours in a standard cement curing box (temperature 20°C, humidity 98-99%) using a mold of corresponding size to form the mixture. The mixture was then immersed in a water tank at room temperature for 6 or 27 days to obtain cement-based composite material samples with different curing times (referred to as ordinary mortar-based samples). In addition, the mixture was cured in a standard cement curing box (temperature 20°C, humidity 98-99%) for 6 or 24 hours, and then removed to obtain cement-based composite material samples for infrared testing.

[0120] Comparative Example 2

[0121] 450 g of cement, 2.7 g of polycarboxylate water reducer, 1350 g of standard sand, 93 g of fly ash, 93 g of mineral powder, 1784 g of gravel and 190.8 g of deionized water (the water-cement ratio of the mixed system is calculated to be 0.3) are mixed and stirred at room temperature for 30 minutes to obtain a mixture; according to the requirements of subsequent tests, the mixture is cured in a standard cement curing box (temperature of 20°C and humidity of 98-99%) for 24 hours using a mold of corresponding size to form a shape, and then immersed in a water tank at room temperature for 6 days or 27 days to obtain cement-based composite material samples with different curing times (referred to as ordinary concrete-based samples).

[0122] Comparative Example 3

[0123] 0.384 g of NaOH was weighed and dissolved in 60 mL of an ethanol / water mixed solvent (volume ratio of 1:1), and then 1.17 g of phenylboric acid was added. After the phenylboric acid was completely dissolved, the mixed solution was heated to 50° C. under constant temperature magnetic stirring conditions, and then 25 mL of a 0.31 M Ca(NO 3 ) 2 · 4H 2 O solution was added dropwise. After the addition was complete, stirring was continued for 2 hours, and the precipitated product was then separated by high-speed centrifugation and dried in a vacuum oven at 60° C. for 24 hours to obtain a calcium phenylborate MOF (i.e., Ca-MOF, the same as the in situ grown Ca-MOF in Example 1);

[0124] 450 g of cement, 0.45 g of calcium phenylborate MOF, 2.7 g of polycarboxylate water reducer, 1350 g of standard sand, 93 g of fly ash, 93 g of mineral powder and 190.8 g of deionized water (the water-cement ratio of the mixed system is calculated to be 0.3) were mixed and stirred at room temperature for 30 min to obtain a mixture; according to the requirements of subsequent mechanical properties testing, the mixture was cured in a standard cement curing box (temperature of 20°C, humidity of 98-99%) for 24 h using a mold of corresponding size to form a shape, and then immersed in a water tank at room temperature for 6 days or 27 days to obtain cement-based composite material samples with different curing times (referred to as mortar-based samples with direct addition of Ca-MOF).

[0125] Comparative Example 4

[0126] 0.384 g of NaOH was weighed and dissolved in 60 mL of an ethanol / water mixed solvent (volume ratio of 1:1), and then 1.17 g of phenylboric acid was added. After the phenylboric acid was completely dissolved, the mixed solution was heated to 50° C. under constant temperature magnetic stirring conditions, and then 25 mL of a 0.31 M Ca(NO 3 ) 2 · 4H 2 O solution was added dropwise. After the addition was complete, stirring was continued for 2 hours, and the precipitated product was then separated by high-speed centrifugation and dried in a vacuum oven at 60° C. for 24 hours to obtain a calcium phenylborate MOF (i.e., Ca-MOF, the same as the in situ grown Ca-MOF in Example 1);

[0127] 450 g of cement, 0.45 g of calcium phenylborate MOF, 2.7 g of polycarboxylate water reducer, 1350 g of standard sand, 93 g of fly ash, 93 g of mineral powder, 1784 g of gravel and 190.8 g of deionized water (the water-cement ratio of the mixed system is calculated to be 0.3) were mixed and stirred at room temperature for 30 min to obtain a mixture; according to the requirements of subsequent tests, the mixture was cured in a standard cement curing box (temperature of 20°C, humidity of 98-99%) for 24 h using a mold of corresponding size to form a shape, and then immersed in a water tank at room temperature for 6 days or 27 days to obtain cement-based composite material samples with different curing times (referred to as concrete-based samples with direct addition of Ca-MOF).

[0128] Effect verification

[0129] 1. Growth of Ca-MOF in situ growth to prepare cement-based composites

[0130] Figure 1 The infrared spectra of the cement-based composite material samples obtained after curing for 6 hours and 24 hours in Example 1 and Comparative Example 1, respectively, are shown in FIG. Figure 1 It can be seen that in Ca-MOF materials, 1500-1700cm -1 The stretching vibration peaks corresponding to the deprotonation of the carboxylic acid group and its bonding with the divalent metal are 667 cm-1 and 667 cm-2, respectively, at both 6 h and 24 h. -1 、1415cm -1 、1670cm -1 The corresponding characteristic peaks appeared, corresponding to the stretching vibration of the coordination bond (Ca-O) and the symmetric and asymmetric vibration of the carboxyl group (-COOH), and as the age increases, the characteristic peaks become more obvious, while the comparative example 1 does not have characteristic peaks at these positions, which explains the Ca-O bonding in the Ca-MOF in Example 1 and proves the in-situ growth of Ca-MOF in the matrix. In addition, the two different ages of Example 1 at 2364cm -1 The characteristic peak of the carbonyl stretching vibration caused by the hydrogen bond in the organic ligand participating in MOF assembly appeared at 945 cm -1 The vibration peak of Si-O in the CSH skeleton appeared, which, combined with the above five characteristic peaks, indicated the in-situ synthesis of Ca-MOF, and did not affect the basic structure of the cement-based material during its in-situ synthesis process.

[0131] 2. 7d and 28d mechanical strength test of mortar-based samples

[0132] Mortar-based specimens cured for the corresponding number of days in Examples 1-3, Comparative Example 1, and Comparative Example 3 were tested for mechanical strength at 7 and 28 days according to GB / T 17671-2021, "Test Method for Strength of Cement Mortar (ISO Method)." Each mortar-based specimen had a water-cement ratio of 0.3 and a water-reducing agent content of 0.2% (in terms of solids) of the mass of the cementitious material. The test results are shown in Tables 1 and 2.

[0133] Table 1 Compressive strength test results of mortar-based samples

[0134]

[0135] Table 2 Test results of flexural strength of mortar-based samples

[0136]

[0137] It can be seen from Table 1 and Table 2 that the compressive strength and flexural strength of the mortar-based samples prepared based on the in-situ growth of Ca-MOF in Examples 1-3 at different curing ages are significantly higher than those of the ordinary mortar sample of Comparative Example 1 and the mortar-based sample with direct addition of Ca-MOF of Comparative Example 3. The early strength and late strength of the mortar-based samples prepared based on the in-situ growth of Ca-MOF are significantly improved, indicating that the mortar-based samples prepared based on the in-situ growth of Ca-MOF in the present invention have higher early strength and do not affect the late strength.

[0138] 3. 7d and 28d mechanical strength test of concrete specimens

[0139] Concrete-based specimens from Examples 4-6, Comparative Examples 2, and Comparative Example 4, cured for the corresponding number of days, were tested for mechanical strength at 7 and 28 days according to GB / T50081-2019, "Test Methods for Physical and Mechanical Properties of Concrete." Each concrete-based specimen had a water-cement ratio of 0.3 and a water-reducing agent dosage of 0.2% (total solids) of the cementitious material. The test results are shown in Tables 3 and 4.

[0140] Table 3 Compressive strength test results of concrete base specimens

[0141]

[0142] Table 4 Test results of flexural strength of concrete base specimens

[0143]

[0144] As can be seen from Tables 3 and 4, the compressive and flexural strengths of the concrete-based specimens prepared based on the in-situ growth of Ca-MOF in Examples 4-6 at different curing ages are significantly higher than those of the ordinary concrete specimens in Comparative Example 2 and the concrete-based specimens with direct addition of Ca-MOF in Comparative Example 4. The early and late strengths of the concrete-based specimens prepared based on the in-situ growth of Ca-MOF are significantly improved, indicating that the concrete-based specimens prepared based on the in-situ growth of Ca-MOF in the present invention have higher early strength without affecting the late strength.

[0145] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing a cement-based composite material based on in-situ growth of Ca-MOF, characterized in that: The following steps are involved: A calcium source solution and an organic ligand solution are mixed to obtain a MOF pre-assembly solution; the MOF pre-assembly solution is added to a cement-based material, stirred evenly, and then cured and formed to obtain the cement-based composite material based on in-situ growth of Ca-MOF.

2. The method for preparing a cement-based composite material based on in-situ growth of Ca-MOF according to claim 1, wherein: The preparation step of the calcium source solution comprises: mixing a calcium source and water and stirring for 5-15 minutes to obtain the calcium source solution; And / or, the step of preparing the organic ligand solution includes: mixing the organic ligand and a co-solvent to obtain the organic ligand solution.

3. The method for preparing a cement-based composite material based on in-situ growth of Ca-MOF according to claim 2, wherein: The calcium source is calcium nitrate tetrahydrate, calcium acetate or calcium chloride; And / or, the mass ratio of the calcium source to water is 1:10-40.

4. The method for preparing a cement-based composite material based on in-situ growth of Ca-MOF according to claim 2, wherein: The preparation step of the cosolvent comprises: mixing one or both of an alkaline substance and an organic solvent with water and stirring for 10-20 minutes to obtain the cosolvent; and / or, the alkaline substance is sodium hydroxide, potassium hydroxide, sodium bicarbonate, sodium carbonate, potassium carbonate or ammonia water; And / or, the organic solvent is anhydrous ethanol, N,N-dimethylacetamide, methanol or isopropanol.

5. The method for preparing a cement-based composite material based on in-situ growth of Ca-MOF according to claim 2, wherein: The step of mixing the organic ligand and the cosolvent to obtain the organic ligand solution comprises: mixing the organic ligand and the cosolvent and stirring for 15-30 minutes to obtain the organic ligand solution; and / or, the organic ligand is 1,4-benzenedicarboxylic acid, trimesic acid, gallic acid, phenylboronic acid, 9-fluorenone-2,7-dicarboxylic acid, fumaric acid, squaric acid or 1,4-naphthalene dicarboxylic acid; And / or, the mass ratio of the organic ligand to the cosolvent is 1:50-100.

6. The method for preparing a cement-based composite material based on in-situ growth of Ca-MOF according to claim 1, wherein: The step of mixing the calcium source solution with the organic ligand solution to obtain the MOF pre-assembly solution comprises: mixing the calcium source solution and the organic ligand solution and stirring for 3-15 minutes, and then ultrasonically treating for 5-10 minutes to obtain the MOF pre-assembly solution; And / or, the molar ratio of the organic ligand contained in the organic ligand solution to the calcium source contained in the calcium source solution is 0.3-1:

1.

7. The method for preparing a cement-based composite material based on in-situ growth of Ca-MOF according to claim 1, wherein: The cement-based material includes paste, mortar or concrete.

8. The method for preparing a cement-based composite material based on in-situ growth of Ca-MOF according to claim 1, wherein: The step of adding the MOF pre-assembly solution to the cement-based material comprises: the ratio of the mass of the MOF pre-assembly solution to the mass of the gelling material contained in the cement-based material is 1:10-20.

9. The method for preparing a cement-based composite material based on in-situ growth of Ca-MOF according to claim 7, wherein: The raw materials of the mortar include cementitious materials, water reducing agent, sand and water, and the cementitious materials are cement, fly ash and mineral powder; Alternatively, the raw materials of the concrete include cementitious materials, water reducing agent, sand, gravel and water, and the cementitious materials are cement, fly ash and mineral powder.

10. A cement-based composite material based on in-situ growth of Ca-MOF prepared according to the preparation method according to any one of claims 1 to 9.

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