A method for preparing a MOFs-based polymer material capable of simultaneously adsorbing liquid water and gaseous water

Abstract

The application discloses a preparation method of MOFs-based polymer material capable of simultaneously adsorbing liquid water and gaseous water, and utilizes reaction of vinyl-containing organic molecules (acrylic anhydride, acrylic acid, methacrylic acid, methacrylic anhydride, maleic acid and maleic anhydride) with metal organic framework MOFs (metal is aluminum, magnesium, iron or chromium) to obtain vinyl-containing metal organic framework (CHR=CH-CO-NH-MOFs, R=CH3 or H), namely functional monomer F-MOFs. The polymer material has the functions of simultaneously collecting liquid water (SAP) and gaseous water (MOFs), can not only adsorb liquid water, but also adsorb water vapor. Compared with pure soil-based anti-evaporation material, the polymer material reduces evaporation loss of 6.1% of soil, and improves water resource utilization efficiency. The synthesized F-MOFs can be used as polymerization monomer and stereoscopic crosslinking agent, the material has simple synthesis process, is convenient to operate, good controllability, and is convenient for large-scale industrial production, and can be widely applied to farmland and desertification prevention and control.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of polymer materials and water collection and water saving technology, and relates to a MOFs-based polymer material, in particular to a preparation method of a MOFs-based polymer material capable of simultaneously adsorbing liquid water and gaseous water. BACKGROUND

[0002] The hydrogel is a natural or synthetic polymer with slight crosslinking. The MOFs material has a three-dimensional structure, a large saturated adsorption capacity, easy desorption, and an S-shaped adsorption and desorption isotherm characteristic, and thus has a wide application prospect in various fields. Meanwhile, the molecular chain of the hydrogel has a large number of hydrophilic groups (such as -OH, -COOH, -SO3H, -CONH), which can produce strong hydration on liquid water or water vapor under a certain humidity. The monomers and crosslinking agents commonly used for preparing the hydrogel are one-dimensional organic molecules, which are single in variety and have few size selections. The size, water absorption rate and water retention of the hydrogel network synthesized from the one-dimensional monomers are limited. The hydrogel can absorb liquid water, but has weak adsorption on gaseous water, and the water saving effect is severely limited.

[0003] Therefore, the application greatly improves the water absorption rate and water vapor capturing capacity of the material by using the MOFs with a three-dimensional network structure as a functionalized three-dimensional crosslinking agent, introducing polysaccharides or monomers with hydrophilic groups, and constructing a three-dimensional controllable network polymer through free radical copolymerization, so as to alleviate the crisis of fresh water resources. SUMMARY

[0004] The application aims to provide a preparation method of a MOFs-based polymer material capable of simultaneously adsorbing liquid water and gaseous water.

[0005] In order to achieve the above-mentioned purpose, the technical scheme adopted by the application is as follows:

[0006] I. Preparation of the MOFs-based polymer material

[0007] The preparation method of the MOFs-based polymer material capable of simultaneously adsorbing liquid water and gaseous water comprises the following steps:

[0008] Step (1) Preparation of MOF:

[0009] Dissolve the metal salt and 2-amino terephthalic acid in 50-80 mL of N,N-dimethylformamide or distilled water, transfer the solution to a polytetrafluoroethylene autoclave, react at 120-150 DEG C for 8-24 h, centrifugal separation, wash with N,N-dimethylformamide and anhydrous methanol respectively, and vacuum dry at 60-100 DEG C.

[0010] Step (2) preparation of functional crosslinking agent: the product synthesized in step (1) is mixed with vinyl organic molecules uniformly and dissolved in CH2Cl2, after being closed and stored for 24-72 h, washed with CH2Cl2, and dried under vacuum at 40-60℃ to obtain the functional stereoscopic crosslinking agent;

[0011] Step (3) preparation of MOFs-based polymer material:

[0012] The functional stereoscopic crosslinking agent is dispersed in distilled water, heated to 60-80℃ and kept for 35-60 min, then cooled to 40-60℃, and ammonium persulfate aqueous solution is added as an initiator, and activated for 15-30 min, then a mixture of acrylic acid and vinyl organic monomers with a certain neutralization degree is added, heated to 60-80℃, and reacted at constant temperature for 2-4 h, and the obtained product is dried at 60-80℃ to constant weight to obtain the product. The whole reaction is carried out under nitrogen protection.

[0013] Preferably, in step (1), the metal salt is one of zirconium chloride, chromium nitrate nonahydrate, aluminum chloride hexahydrate, ferric chloride, and magnesium chloride.

[0014] Preferably, in step (1), the molar ratio of the metal salt to 2-amino terephthalic acid is 1:1-3:1.

[0015] Preferably, in step (1), the vinyl organic molecule is one of acrylic anhydride, acrylic acid, methacrylic acid, methacrylic anhydride, maleic acid, and maleic anhydride.

[0016] Preferably, the synthesized MOF is mixed with the vinyl organic molecule uniformly at a mass ratio of 1:0.5-1:2.0, and dissolved in 40-100 mL of CH2Cl2.

[0017] Preferably, in step (2), the neutralization degree of the acrylic acid is 50-90%.

[0018] Preferably, in step (2), the vinyl organic monomer is one of acrylamide, 2-acrylamido-2-methyl 1-propane sulfonic acid, dimethyl diallyl ammonium chloride, N-isopropyl acrylamide, hydroxyethyl acrylate, hydroxymethyl acrylate, vinyl acetate, N-hydroxyethyl acrylamide, hydroxymethyl acrylamide, N-vinyl pyrrolidone, allyloxy hydroxypropyl sulfonic acid sodium, and bis-acetone acrylamide.

[0019] Preferably, in step (2), the amount of the vinyl organic monomer is 5-40 wt% of the acrylic acid with a neutralization degree of 50-90%.

[0020] Preferably, in step (2), the functionalized stereocrosslinking agent is one of the following: functionalized MIL-101-NH2 (Cr), MIL-101-NH2 (Al), MIL-53-NH2, UIO-66-NH2, MIL-125-NH2, MIL-101(Fe)-NH2, MIL-53(Fe)-NH2, CAU-1-NH2 (Al), MIL-125(Ti)-NH2, or MIL-53(Fe)-NH2. The amount of the functionalized stereocrosslinking agent is 0.5 to 10 wt% of acrylic acid. This type of MOF has the characteristics of three-dimensional spatial structure, unique microstructure, porosity, and ease of functionalization. When introduced into the construction of polymer materials, it forms a three-dimensional network structure, thereby achieving dual adsorption of liquid water and water vapor.

[0021] II. Liquid water absorption ratio and water vapor adsorption performance of MOF-based polymer materials

[0022] Accurately weigh 0.05–0.5 g of dried sample and immerse it in distilled water, tap water, and 0.9 wt% sodium chloride aqueous solution, respectively. After the sample reaches adsorption equilibrium, remove excess water with a sieve, weigh it again, and calculate its water absorption ratio.

[0023] Take containers of the same size (9cm in diameter), weigh the same weight of MOFs-based polymer material using an electronic balance, place them in a constant temperature and humidity chamber at 25-50℃ and 50%-90%RH, weigh them every 2-4 hours, and calculate the amount of water vapor adsorbed.

[0024] Figure 1 Reaction mechanism diagram for the functionalization of metal-organic frameworks and the synthesis of MOF-based polymer materials

[0025] Figure 2 The water absorption ratio of the MIL-101-NH2(Cr)-based polymer material to liquid water is given. The swelling behavior of the samples at room temperature in distilled water, tap water, and 0.9% NaCl solution is as follows: Figure 1 As shown in the figure. The results indicate that the optimal reaction conditions for this sample are: 12 wt% of the mass of Artemisia argyi, 0.8 wt% of the mass of the initiator, and 1 wt% of the mass of the functional crosslinking agent, respectively. The reaction time is 3 hours, and the degree of neutralization of the acrylic acid is 70%. Under the optimal synthesis conditions, its maximum water absorption rate in distilled water is 2655 g / g. After functionalization, MIL-101-NH2(Cr) can be used as a crosslinking agent to prepare polymer materials. Its three-dimensional structure is rich in hydrophilic groups, providing large adsorption sites for water molecules. However, a high content of functional crosslinking agent will lead to an excessively high crosslinking density, resulting in a smaller pore size, thereby reducing the elasticity of the base polymer material and thus reducing its water (salt) absorption capacity.

[0026] Figure 3 The water absorption ratio of the MIL-53-NH2-based polymer material in liquid water is given, and the swelling behavior of the sample in tap water at room temperature is as follows: Figure 2 As shown in the figure. The results indicate that the optimal reaction conditions for this sample are: 12 wt% of the mass of Artemisia argyi, 0.8 wt% of the mass of the initiator, and 3 wt% of the mass of the functional crosslinking agent, respectively. The reaction time is 3 hours, and the degree of neutralization of the acrylic acid is 70%. Under the optimal synthesis conditions, its maximum water absorption rate in tap water is 367 g / g. After functionalization, MIL-53-NH2 can be used as a crosslinking agent to prepare polymer materials. Its three-dimensional structure is rich in hydrophilic groups, providing large adsorption sites for water molecules. However, a high content of functional crosslinking agent will lead to an excessively high crosslinking density, resulting in a smaller pore size, thereby reducing the elasticity of the polymer material and thus reducing its water (salt) absorption capacity.

[0027] Figure 4 The water vapor adsorption behavior of MIL-101-NH2(Cr), MIL-53-NH2, and UIO-66-NH2-based polymer materials was investigated within the range of 25℃ and RH values ​​of 50-90%. The hygroscopicity of MOF-based polymer materials increased with increasing relative humidity. Results showed that MIL-101-NH2(Cr) had a water absorption ratio of 2655 g / g in distilled water, and its water vapor adsorption capacity reached 85 mg / g at 25℃ and 50% RH. MIL-53-NH2 had a water absorption ratio of 367 g / g in tap water, and its water vapor adsorption capacity reached 370 mg / g at 25℃ and 70% RH. UIO-66-NH2-based polymer material rapidly absorbed water vapor at 70% relative humidity, reaching 785 mg / g after 3 hours. This is likely due to the three-dimensional structure of MOF-based polymer materials and the abundance of hydrophilic functional groups on their molecular chains, which enhance their water vapor capture capacity even in arid environments. Three-dimensional MOF-based polymer materials constructed using modified MOFs as functional crosslinking agents can continuously absorb water in humid environments, giving them high water retention. The polymer backbone functions as a water storage medium. The hydrophilic functional groups on the material surface capture the first layer of water molecules and use them as adsorption sites, enabling rapid adsorption of water vapor. This water is then stored within the polymer backbone. The stored water can be discharged from the polymer network in liquid form via solar energy or energy-driven power to obtain freshwater resources.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] 1. This invention discloses a method for preparing a polymer material containing both metal-organic framework (MOF) components and superabsorbent polymer (SAP) components in a polymer chain. The method employs a post-synthetic modification strategy to functionalize the polymer. First, functionalized MOFs are used as crosslinking agents to construct a MOF-based polymer material with a three-dimensional network. This is a novel functional crosslinking agent that can improve the material's water absorption ratio. This polymer material has the function of simultaneously accumulating liquid water (SAP) and gaseous water (MOFs), and can simultaneously adsorb both liquid and gaseous water. This reduces ineffective evaporation of soil moisture and improves the effective utilization rate of water resources. Compared with pure soil-based anti-evaporation materials, this polymer material reduces soil evaporation loss by 6.1%.

[0030] 2. The functionalized MOFs prepared by the method of the present invention can be used as novel crosslinking agents in the field of polymer materials, and can also be used as polymer monomers. The present invention uses a "one-pot method" to construct MOF-based polymer materials with three-dimensional structures. The synthesis process is simple, easy to operate, has good controllability, can be mass-produced, and can be widely used in the fields of agriculture, forestry and desertification control.

[0031] 3. The method for preparing MOFs-based polymer materials with dual functions of reducing soil moisture evaporation and water collection provided by the present invention expands the monomers and crosslinking agents that can be used in the field, and provides another way to regulate the function of materials. This method is of great significance for building an ecological security barrier in northern my country and realizing the prevention and control of wind and sand hazards and the ecological restoration of desertification. Attached Figure Description

[0032] Figure 1 The reaction mechanism for the functionalization of metal-organic frameworks and the synthesis of MOF-based polymer materials;

[0033] Figure 2 The water absorption ratio of the MIL-101-NH2(Cr)-based polymer material to liquid water;

[0034] Figure 3 The water absorption ratio of the MIL-53-NH2-based polymer material to liquid water; Figure 4 The water vapor adsorption behavior of MIL-101-NH2(Cr), MIL-53-NH2, and UIO-66-NH2-based polymer materials in the range of 25°C and RH value of 50-90% was studied. Detailed Implementation

[0035] The present invention will be further explained and described below with reference to the accompanying drawings and specific embodiments.

[0036] Example 1

[0037] Preparation method of MIL-101-NH2(Cr) based polymer material:

[0038] Step (1) Preparation of MIL-101-NH2(Cr): Chromium nitrate nonahydrate and 2-aminoterephthalic acid were dissolved in 50-80 mL of distilled water. The solution was transferred to a polytetrafluoroethylene autoclave and reacted at 120-150 °C for 8-24 hours. The resulting powder was separated by centrifugation, washed with N,N-dimethylformamide and anhydrous methanol, and dried under vacuum at 60-100 °C.

[0039] Step (2) Preparation of functionalized crosslinking agent: The product obtained in step (1) is mixed evenly with acrylic anhydride and dissolved in CH2Cl2, and then sealed and stored in a solvent bottle for 24–72 hours. The resulting solid is washed multiple times with CH2Cl2 and dried under vacuum at 40–60°C.

[0040] Step (3) Preparation of MIL-101-NH2(Cr)-based polymer material: The functionalized crosslinking agent was stirred and dispersed evenly in distilled water, heated to 60-80℃ and maintained for 35-60 min, then cooled to 40-60℃, and ammonium persulfate aqueous solution was added as an initiator. Activation was continued for 15-30 min, and a mixture of acrylic acid and acrylamide with a certain degree of neutralization was added. The temperature was raised to 60-80℃ and the reaction was maintained at a constant temperature for 2-4 hours. The obtained product was dried to constant weight at 60-80℃, pulverized, granulated, and sieved to obtain the MIL-101-NH2(Cr)-based polymer material. The entire reaction was protected with nitrogen.

[0041] Tests on the liquid water absorption ratio and water vapor adsorption performance of MOF-based polymer materials:

[0042] (1) Accurately weigh 0.05–0.5 g of dried sample and immerse it in distilled water, tap water, and 0.9 wt% sodium chloride aqueous solution, respectively. After the sample reaches adsorption equilibrium, remove excess water with a sieve, weigh it again, and calculate its water absorption ratio. Figure 2 As shown, the results indicate that its water absorption ratio in distilled water is 2655 g / g.

[0043] (2) The prepared MIL-101-NH2(Cr)-based polymer material was placed in a constant temperature and humidity chamber at 25–50°C and 50%–90% RH. Weighing was performed every 2–4 hours, and the amount of water vapor adsorbed was calculated. Figure 4 As shown in the figure, the results indicate that its adsorption capacity for water vapor can reach 85 mg / g at 25℃ and 50% RH.

[0044] Example 2

[0045] Preparation method of MIL-53-NH2 based polymer materials:

[0046] Step (1) Preparation of MIL-53-NH2: Dissolve aluminum chloride hexahydrate and 2-aminoterephthalic acid in 50-80 mL of distilled water. Transfer the solution to a polytetrafluoroethylene autoclave and react at 120-150 °C for 8-24 hours. The resulting powder is separated by centrifugation, washed with N,N-dimethylformamide and anhydrous methanol, and dried under vacuum at 60-100 °C.

[0047] Step (2) Preparation of functionalized crosslinking agent: The product obtained in step (1) is mixed evenly with acrylic anhydride and dissolved in CH2Cl2, and then sealed and stored in a solvent bottle for 24–72 hours. The resulting solid is washed multiple times with CH2Cl2 and dried under vacuum at 40–60°C.

[0048] Step (3) Preparation of MIL-53-NH2-based polymer material: The functionalized crosslinking agent was stirred and dispersed evenly in distilled water, heated to 60-80℃ and maintained for 35-60 min, then cooled to 40-60℃, and ammonium persulfate aqueous solution was added as an initiator. Activation was continued for 15-30 min, and a mixture of acrylic acid and 2-acrylamido-2-methyl-1-propanesulfonic acid with a certain degree of neutralization was added. The temperature was raised to 60-80℃ and the reaction was maintained at a constant temperature for 2-4 hours. The obtained product was dried to constant weight at 60-80℃, pulverized, granulated, and sieved to obtain the MIL-53-NH2-based polymer material. The entire reaction was protected by nitrogen.

[0049] Tests on the liquid water absorption ratio and water vapor adsorption performance of MOF-based polymer materials:

[0050] (1) Accurately weigh 0.05–0.5 g of dried sample and immerse it in distilled water, tap water, and 0.9 wt% sodium chloride aqueous solution, respectively. After the sample reaches adsorption equilibrium, remove excess water with a sieve, weigh it again, and calculate its water absorption ratio. Figure 3 As shown in the figure, the results indicate that its water absorption ratio in tap water is 367 g / g.

[0051] (2) The prepared MIL-53-NH2-based polymer material was placed in a constant temperature and humidity chamber at 25–50°C and 50%–90% RH. Weighing was performed every 2–4 hours, and the amount of water vapor adsorbed was calculated. Figure 4 As shown in the figure, the adsorption capacity of water vapor can reach 370 mg / g at 25℃ and 70% RH.

[0052] Example 3

[0053] Preparation method of UIO-66-NH2 based polymer materials:

[0054] Step (1) Preparation of UIO-66-NH2: Zirconium chloride and 2-aminoterephthalic acid were dissolved in 50-80 mL of N,N-dimethylformamide. The solution was transferred to a polytetrafluoroethylene autoclave and reacted at 120-150 °C for 8-24 hours. The resulting powder was separated by centrifugation, washed with N,N-dimethylformamide and anhydrous methanol, and dried under vacuum at 60-100 °C.

[0055] Step (2) Preparation of functionalized crosslinking agent: The product obtained in step (1) is mixed evenly with acrylic anhydride and dissolved in CH2Cl2, and then sealed and stored in a solvent bottle for 24–72 hours. The resulting solid is washed multiple times with CH2Cl2 and dried under vacuum at 40–60°C.

[0056] Step (3) Preparation of UIO-66-NH2-based polymer material: The functionalized crosslinking agent was stirred and dispersed evenly in distilled water, heated to 60-80℃ and maintained for 35-60 min, then cooled to 40-60℃, and ammonium persulfate aqueous solution was added as an initiator. Activation was continued for 15-30 min, and a mixture of acrylic acid and dimethyl diallyl ammonium chloride with a certain degree of neutralization was added. The temperature was raised to 60-80℃ and the reaction was maintained at a constant temperature for 2-4 hours. The obtained product was dried to constant weight at 60-80℃, pulverized, granulated, and sieved to obtain the UIO-66-NH2-based polymer material. The entire reaction was protected by nitrogen.

[0057] Water vapor adsorption performance test of MOF-based polymer materials:

[0058] The prepared UIO-66-NH2-based polymer material was placed in a constant temperature and humidity chamber at 25–50°C and 50%–90% RH. Weighing was performed every 2–4 hours, and the amount of water vapor adsorbed was calculated. Figure 4 As shown, the results indicate that its adsorption capacity for water vapor can reach 1220 mg / g at 25℃ and 90% RH.

Claims

1. A method for preparing a MOFs-based polymer material capable of simultaneously adsorbing liquid water and gaseous water, characterized in that, Includes the following steps: Step (1) Preparation of MOF: Metal salt and 2-aminoterephthalic acid were dissolved in 50-80 mL of N,N-dimethylformamide or distilled water. The solution was transferred to a polytetrafluoroethylene autoclave and reacted at 120-150 °C for 8-24 h. After centrifugation, the mixture was washed with N,N-dimethylformamide and anhydrous methanol, respectively, and dried under vacuum at 60-100 °C to obtain MOF. Step (2) Preparation of functionalized crosslinking agent: The MOF synthesized in step (1) was mixed evenly with vinyl organic molecules and dissolved in CH2Cl2. After being sealed and stored for 24 to 72 hours, it was washed with CH2Cl2 and dried under vacuum at 40 to 60°C to obtain a functionalized stereocrosslinking agent. Step (3) Preparation of MOFs-based polymer materials: The functionalized stereocrosslinking agent was dispersed in distilled water, heated to 60-80℃ and held for 35-60 min, then cooled to 40-60℃. Ammonium persulfate aqueous solution was added as an initiator and activated for another 15-30 min. A mixture of organic monomers of acrylic acid and vinyl with a certain degree of neutralization was added, and the temperature was raised to 60-80℃ and reacted at a constant temperature for 2-4 h. The resulting product was dried at 60-80℃ to constant weight. The entire reaction was carried out under nitrogen protection. In step (1), the metal salt is one of zirconium chloride, chromium nitrate nonahydrate, aluminum chloride hexahydrate, ferric chloride, and magnesium chloride; In step (1), the molar ratio of the metal salt to 2-aminoterephthalic acid is 1:1 to 3:1; In step (2), the vinyl organic molecule is one of acrylic anhydride, acrylic acid, methacrylic acid, methacrylic anhydride, maleic acid, and maleic anhydride; In step (2), the synthesized MOF and vinyl organic molecules are mixed evenly at a mass ratio of 1:0.5 to 1:2.0 and dissolved in 40 mL to 100 mL of CH2Cl2; In step (3), the degree of neutralization of acrylic acid is 50-90%.

2. The method for preparing a MOFs-based polymer material capable of simultaneously adsorbing liquid water and gaseous water as described in claim 1, characterized in that, In step (3), the vinyl organic monomer is one of acrylamide, 2-acrylamido-2-methyl-1-propanesulfonic acid, dimethyl diallyl ammonium chloride, N-isopropylacrylamide, hydroxyethyl acrylate, hydroxymethyl acrylate, vinyl acetate, N-hydroxyethylacrylamide, hydroxymethylacrylamide, N-vinylpyrrolidone, sodium allyloxyhydroxypropanesulfonate, and diacetone acrylamide.

3. The method for preparing a MOFs-based polymer material capable of simultaneously adsorbing liquid water and gaseous water as described in claim 2, characterized in that, In step (3), the amount of vinyl organic monomer used is 5 to 40 wt% of acrylic acid with a neutralization degree of 50 to 90%.

4. The method for preparing a MOFs-based polymer material capable of simultaneously adsorbing liquid water and gaseous water as described in claim 3, characterized in that, In step (3), the amount of functionalized stereocrosslinking agent used is 0.5 to 10 wt% of acrylic acid.

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