A high-capacity water-absorbing ionic liquid functionalized metal-organic framework material and its preparation method

Abstract

This invention discloses an ionic liquid-functionalized metal-organic framework (MOF) material with high water absorption capacity and a preparation method thereof. This method employs a synthetic strategy in which ionic liquid structural units are implanted into the MOF framework. By pre-ionic liquidizing the ligands, a stable ionic liquid-functionalized MOF material is constructed to enhance its water adsorption capacity. The ionic liquid-functionalized MOF material prepared in this invention exhibits a water adsorption capacity of 0.88 to 2.44 g / g. Under optimal mixing conditions, the water adsorption capacity reaches as high as 2.44 g / g, exceeding the previously reported value by more than 25%.

Description

Technical Field

[0001] The invention belongs to the technical field of water or water vapor adsorption materials, and particularly relates to an ionic liquid functionalized metal organic framework material with high water absorption capacity and a preparation method thereof. Background Art

[0002] High-capacity water adsorbents hold significant application potential and value in areas such as air water collection, indoor air humidity control, natural gas dehydration, and industrial gas drying. For example, in industrial adsorption, separation, and catalysis applications, gaseous or liquid water molecules are inevitably present during material preparation, processing, storage, transportation, and production. Porous materials such as molecular sieves and activated carbon are often used for water storage or removal in these processes. However, these materials generally have low water adsorption capacities.

[0003] Metal-organic frameworks (MOFs) are porous crystalline materials with periodic network structures formed by the self-assembly of metal ions and organic ligands through coordination bonds. These materials typically possess advantages such as high specific surface area, structural diversity, ligand modifiability, and tunable pore properties, holding significant application potential and value in the field of adsorption and separation. Some water-stable MOFs have demonstrated excellent water adsorption properties. For example, Professor Yaghi's group reported the potential for MOFs to be used for water absorption and storage in desert regions. At 25°C, MOF-303(Al) exhibited a water adsorption capacity of 0.45 g / g. Subsequently, various strategies have been employed to investigate the water absorption and storage properties of MOFs, attempting to increase their water adsorption capacity. Currently, only a few MOFs have achieved water adsorption capacities exceeding 1 g / g at 25°C. For example, NU-1000(Zr) exhibits a water adsorption capacity of 1.32 g / g, and Ni2Cl2BTDD exhibits a water adsorption capacity of 1.07 g / g. By constructing a high-surface-area metal-organic framework (MOF) material, Cr-soc-MOF-1 achieved a water adsorption capacity of 1.95 g / g. Despite significant progress in this field, existing MOFs generally have low water adsorption capacities, necessitating the development of high-capacity water-adsorption MOFs.

[0004] Ionic liquids are a type of organic salt that generally have strong water absorption. Inspired by this, the present invention envisions that if ionic liquids can be introduced into metal-organic framework materials, it is possible to prepare ionic liquid-functionalized metal-organic framework materials with strong water absorption capacity. However, ionic liquids with strong water absorption are generally hydrophilic, and after absorbing water, there is a great possibility that the ionic liquid will be lost from the pores of the metal-organic framework, resulting in instability of the adsorbent material. In order to ensure the stability of ionic liquid-functionalized metal-organic framework materials to water, the present invention proposes a synthetic strategy of implanting the structural units of ionic liquids into the skeleton of metal-organic framework materials, and constructing stable ionic liquid-functionalized metal-organic framework materials through the pre-ionic liquidization of ligands, thereby effectively improving the adsorption capacity for water. However, there are currently no relevant reports in this regard. Summary of the Invention

[0005] In order to solve the technical problem of the generally low water absorption capacity of metal-organic framework materials in the prior art, the present invention provides an ionic liquid functionalized metal-organic framework material with high water absorption capacity and a preparation method thereof. The method adopts the pre-ionic liquidization of the ligand to prepare a polyhydroxy ionic liquid functionalized metal-organic framework material, which effectively improves the water adsorption capacity of the metal-organic framework material.

[0006] The present invention adopts the following technical solution to solve the above technical problems: an ionic liquid functionalized metal organic framework material with high water absorption capacity, characterized in that: the ionic liquid functionalized metal organic framework material is compounded by hydroxyl ionic liquid functionalized carboxylic acid ligand and 4,4-biphenyl dicarboxylic acid, and is prepared by a solvent thermal reaction with a metal zirconium salt. The ionic liquid functionalized metal organic framework material has a good crystalline structure, a high specific surface area, and contains abundant polar hydroxyl groups and chloride and bromide ion adsorption sites. The ionic liquid functionalized metal organic framework material has an adsorption capacity for water of 0.88 to 2.44 g / g and a storage density of 1.00 to 7.18 g / cm 3 , wherein the hydroxy ionic liquid functionalized carboxylic acid ligand is one or more of the following structural formulas:

[0007]

[0008] The preparation process of the ionic liquid functionalized metal organic framework material of the present invention is as follows: 4,4-biphenyldicarboxylic acid, a hydroxy ionic liquid functionalized carboxylic acid ligand and a metal zirconium salt are added to a solvent, a catalyst is added, and after uniform dispersion and mixing with ultrasonic assistance, the mixture is added to a stainless steel reactor lined with polytetrafluoroethylene, reacted at 80-200°C, cooled to room temperature after the reaction is completed, and the obtained white solid is washed with N,N-dimethylformamide and anhydrous ethanol multiple times, and then dried to obtain the ionic liquid functionalized metal organic framework material, wherein the catalyst is one or more of formic acid, glacial acetic acid, sulfuric acid, benzenesulfonic acid, p-toluenesulfonic acid or benzoic acid, preferably glacial acetic acid.

[0009] It is further defined that the hydroxy ionic liquid functionalized carboxylic acid ligand is preferably [H2BPDC-DMEA] + Cl - .

[0010] It is further defined that the molar ratio of the hydroxy ionic liquid functionalized carboxylic acid ligand to 4,4-biphenyldicarboxylic acid is 1:10 to 10:1.

[0011] It is further defined that the molar ratio of the hydroxyl ionic liquid functionalized carboxylic acid ligand to 4,4-biphenyldicarboxylic acid is 9:1.

[0012] It is further defined that the solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dioxane, ethanol, methanol, acetonitrile, tetrahydrofuran, mesitylene, chloroform or dichloromethane, preferably N,N-dimethylformamide.

[0013] It is further defined that the metal zirconium salt is one or more of ZrCl4, zirconyl chloride or zirconyl nitrate, preferably ZrCl4.

[0014] It is further defined that the preparation steps of the ionic liquid functionalized metal organic framework material are: 0.036mmol 4,4,-biphenyldicarboxylic acid, 0.324mmol hydroxy ionic liquid functionalized carboxylic acid ligand [H2BPDC-DMEA] + Cl - The reaction mixture was added with 0.36 mmol ZrCl4 into 15 mL N, N-dimethylformamide, and then 1.65 mL glacial acetic acid was added. After ultrasonic-assisted dispersion and mixing, the mixture was added into a 50 mL stainless steel reactor lined with polytetrafluoroethylene and reacted at 120 ° C for 24 h. After the reaction, it was cooled to room temperature. The obtained white solid was washed with N, N-dimethylformamide and anhydrous ethanol for multiple times, and then dried in vacuum at 120 ° C to obtain an ionic liquid functionalized metal organic framework material. The specific surface area of ​​the ionic liquid functionalized metal organic framework material is 484 m 2 ·g-1 , the pore volume is 0.34 cm 3 ·g -1 The pore size is 0.71nm. At 25.0℃, the adsorption capacity of the ionic liquid functionalized metal organic framework material for water is 2.44g / g, and the storage density of water reaches 7g / cm 3 above.

[0015] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0016] 1. The present invention uses a polyhydroxy ionic liquid functionalized ligand to compound with 4,4-biphenyldicarboxylic acid, and then reacts with a metal zirconium salt using a solvothermal method. The prepared ionic liquid functionalized metal-organic framework material has a water adsorption capacity of up to 0.88 to 2.44 g / g. Under the optimal ratio conditions, the water adsorption capacity is as high as 2.44 g / g, which is more than 25% higher than the record value reported in the literature (Cr-soc-MOF-1, 1.95 g / g).

[0017] 2. The ligand compounding method adopted in the present invention can avoid the synthesis of complex ligands and can regulate the water adsorption capacity of ionic liquid functionalized metal organic framework materials by adjusting the ligand compounding ratio. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is the PXRD pattern of the ionic liquid functionalized metal organic framework material prepared in Examples 1-6. It can be seen from the figure that this type of material has good crystallinity.

[0019] Figure 2 This is a nitrogen adsorption curve corresponding to the ionic liquid functionalized metal organic framework material prepared in Examples 1-6. It can be seen from the figure that this type of material has a typical microporous structure.

[0020] Figure 3 This is the pore size distribution diagram corresponding to the ionic liquid functionalized metal organic framework materials prepared in Examples 1-6. As can be seen from the figure, this type of material has a typical pore size of about 0.7 nm.

[0021] Figure 4 This is the water adsorption curve corresponding to the ionic liquid functionalized metal organic framework material prepared in Examples 1-6. As can be seen from the figure, the adsorption capacity of this type of material for water is as high as 0.88 to 2.44 g / g.

[0022] Figure 5 This is the XPS energy spectrum of carbon, chlorine, oxygen, nitrogen and other atoms of the ionic liquid functionalized metal organic framework material prepared in Example 1 before and after water absorption.

[0023] Figure 6This is the temperature-dependent infrared spectrum of the ionic liquid functionalized metal organic framework material prepared in Example 1 after absorbing water. DETAILED DESCRIPTION

[0024] The above contents of the present invention are further described in detail below through examples, but this should not be understood as limiting the scope of the above subject matter of the present invention to the following examples. All technologies implemented based on the above contents of the present invention fall within the scope of the present invention.

[0025] Example 1

[0026] 4,4-biphenyldicarboxylic acid (0.036 mmol), [H2BPDC-DMEA] + Cl - (0.324mmol) and ZrCl4 (0.36mmol) were added to 15mL N,N-dimethylformamide, and then 1.65mL glacial acetic acid was added. After ultrasonic-assisted dispersion and mixing, the mixture was added to a 50mL stainless steel reactor lined with polytetrafluoroethylene and reacted at 120℃ for 24h. After the reaction, it was cooled to room temperature. The obtained white solid was washed with N,N-dimethylformamide and anhydrous ethanol several times, and vacuum dried at 120℃ overnight to obtain an ionic liquid functionalized metal organic framework material. The specific surface area of ​​the ionic liquid functionalized metal organic framework material is 484m 2 ·g -1 , the pore volume is 0.34 cm 3 ·g -1 The pore size is 0.71 nm. At 25.0 ° C, the adsorption capacity of the ionic liquid functionalized metal organic framework material for water is 2.44 g / g, and the storage density of water is 7.18 g / cm 3 above.

[0027] Example 2

[0028] 4,4,-biphenyldicarboxylic acid (0.072 mmol), [H2BPDC-DMEA] + Cl - (0.288mmol) and ZrCl4 (0.36mmol) were added to 15mL N,N-dimethylformamide, and then 1.65mL glacial acetic acid was added. After ultrasonic-assisted dispersion and mixing, the mixture was added to a 50mL stainless steel reactor lined with polytetrafluoroethylene and reacted at 120℃ for 24h. After the reaction, it was cooled to room temperature. The obtained white solid was washed with N,N-dimethylformamide and anhydrous ethanol several times, and vacuum-dried at 120℃ overnight to obtain an ionic liquid functionalized metal organic framework material. The specific surface area of ​​the ionic liquid functionalized metal organic framework material is 843m 2 ·g -1, the pore volume is 0.51cm 3 ·g -1 The pore size is 0.72 nm. At 25.0 ° C, the adsorption capacity of the ionic liquid functionalized metal organic framework material for water is 1.72 g / g, and the water storage density is 3.37 g / cm 3 above.

[0029] Example 3

[0030] 4,4,-biphenyldicarboxylic acid (0.108 mmol), [H2BPDC-DMEA] + Cl - (0.252mmol) and ZrCl4 (0.36mmol) were added to 15mL N,N-dimethylformamide, and then 1.65mL glacial acetic acid was added. After ultrasonic-assisted dispersion and mixing, the mixture was added to a 50mL stainless steel reactor lined with polytetrafluoroethylene and reacted at 120℃ for 24h. After the reaction, it was cooled to room temperature. The obtained white solid was washed with N,N-dimethylformamide and anhydrous ethanol several times, and vacuum dried at 120℃ overnight to obtain an ionic liquid functionalized metal organic framework material. The specific surface area of ​​the ionic liquid functionalized metal organic framework material is 867m 2 ·g -1 , the pore volume is 0.54 cm 3 ·g -1 The pore size is 0.72 nm. At 25.0 ° C, the adsorption capacity of the ionic liquid functionalized metal organic framework material for water is 1.53 g / g, and the storage density of water is 2.83 g / cm 3 above.

[0031] Example 4

[0032] 4,4,-biphenyldicarboxylic acid (0.144 mmol), [H2BPDC-DMEA] + Cl - (0.216mmol) and ZrCl4 (0.36mmol) were added to 15mL N,N-dimethylformamide, and then 1.65mL glacial acetic acid was added. After ultrasonic-assisted dispersion and mixing, the mixture was added to a 50mL stainless steel reactor lined with polytetrafluoroethylene and reacted at 120℃ for 24h. After the reaction was completed, it was cooled to room temperature. The obtained white solid was washed with N,N-dimethylformamide and anhydrous ethanol several times, and vacuum dried at 120℃ overnight to obtain an ionic liquid functionalized metal organic framework material. The specific surface area of ​​the ionic liquid functionalized metal organic framework material is 1100m 2 ·g -1 , the pore volume is 0.61 cm 3 ·g -1The pore size is 0.72 nm. At 25.0 ° C, the adsorption capacity of the ionic liquid functionalized metal organic framework material for water is 1.35 g / g, and the storage density of water is 2.21 g / cm 3 above.

[0033] Example 5

[0034] 4,4,-biphenyldicarboxylic acid (0.180 mmol), [H2BPDC-DMEA] + Cl - (0.180mmol) and ZrCl4 (0.36mmol) were added to 15mL N,N-dimethylformamide, and then 1.65mL glacial acetic acid was added. After ultrasonic-assisted dispersion and mixing, the mixture was added to a 50mL stainless steel reactor lined with polytetrafluoroethylene and reacted at 120℃ for 24h. After the reaction, it was cooled to room temperature. The obtained white solid was washed with N,N-dimethylformamide and anhydrous ethanol several times, and vacuum dried at 120℃ overnight to obtain an ionic liquid functionalized metal organic framework material. The specific surface area of ​​the ionic liquid functionalized metal organic framework material is 1464m 2 ·g -1 , the pore volume is 0.78 cm 3 ·g -1 The pore size is 0.73 nm. At 25.0 ° C, the adsorption capacity of the ionic liquid functionalized metal organic framework material for water is 1.30 g / g, and the storage density of water is 1.67 g / cm 3 above.

[0035] Example 6

[0036] 4,4-biphenyldicarboxylic acid (0.216 mmol), [H2BPDC-DMEA] + Cl - (0.144mmol) and ZrCl4 (0.36mmol) were added to 15mL N,N-dimethylformamide, and then 1.65mL glacial acetic acid was added. After ultrasonic-assisted dispersion and mixing, the mixture was added to a 50mL stainless steel reactor lined with polytetrafluoroethylene and reacted at 120℃ for 24h. After the reaction, it was cooled to room temperature. The obtained white solid was washed with N,N-dimethylformamide and anhydrous ethanol several times, and vacuum dried at 120℃ overnight to obtain an ionic liquid functionalized metal organic framework material. The specific surface area of ​​the ionic liquid functionalized metal organic framework material is 1608m 2 ·g -1 , the pore volume is 0.88 cm 3 ·g -1The pore size is 0.74 nm. At 25.0 ° C, the adsorption capacity of the ionic liquid functionalized metal organic framework material for water is 0.88 g / g, and the storage density of water is 1.00 g / cm 3 above.

[0037] In order to study the adsorption mechanism of water by the ionic liquid functionalized metal organic framework material prepared in Example 1, the XPS spectra of carbon, chlorine, oxygen, nitrogen and other atoms before and after water adsorption were measured, and the interaction between the ionic liquid functionalized metal organic framework material and water was analyzed. The results are as follows: Figure 5 As shown. After water adsorption, the OC=O binding energy of the COOH ligand increased by 0.67eV, indicating that it interacted with water during the adsorption process. After water adsorption, the CN binding energy decreased by 0.25eV, the N binding energy increased by 0.44eV, and the Cl 2p 1 / 2 Reduced by 0.58eV, 2p 3 / 2 The decrease of 0.39 eV suggests that during the adsorption process, N can interact with the negatively charged "O" of H2O through electrostatic interaction, and Cl - The sites may interact with the positively charged "H" of H2O.

[0038] In order to further understand the mechanism of action of ionic liquid functionalized metal organic framework materials with water, the temperature-dependent infrared spectrum of the ionic liquid functionalized metal organic framework material obtained in Example 1 after water adsorption was measured, and combined with the infrared spectrum before water adsorption, it was found that (such as Figure 6 shown), 1725cm -1 The position corresponds to the asymmetric stretching vibration of C=O of the COOH group of the ligand, which shifts after adsorption of water. -1 The symmetrical stretching vibration of C=O of COOH of the ligand corresponds to this peak. After water adsorption, the sharp peak here becomes broadened. -1 The stretching vibration peak of CN at 1060cm disappears after adsorption of water. -1 The stretching vibration peak of CO in -CH2OH (primary alcohol) is shifted after water adsorption. 3000-3600cm -1 The stretching vibration peak of the -OH of the -CH2OH ligand is located at the bottom of the graphite, and after adsorption, a large and obvious broad peak is formed. These results indicate that multiple hydroxyl groups and anionic chloride have important contributions to the adsorption of water.

[0039] The above embodiments describe the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for illustrating the principles of the present invention. Without departing from the scope of the principles of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of protection of the present invention.

Claims

1. An ionic liquid functionalized metal-organic framework material with high water absorption capacity, characterized by: The ionic liquid-functionalized metal-organic framework material is prepared by compounding a hydroxyl ionic liquid-functionalized carboxylic acid ligand with 4,4-biphenyldicarboxylic acid and reacting it with a metal zirconium salt using a solvothermal method. The ionic liquid-functionalized metal-organic framework material has a good crystalline structure, a high specific surface area, and contains abundant polar hydroxyl groups and chloride and bromide ion adsorption sites. The water adsorption capacity of the ionic liquid-functionalized metal-organic framework material can reach 0.88-2.44 g / g, and the storage density is 1.00-7.18 g / cm 3 , wherein the hydroxy ionic liquid functionalized carboxylic acid ligand is one or more of the following structural formulas: ； The specific preparation process of the high-capacity water-absorbing ionic liquid functionalized metal-organic framework material is as follows: 4,4-biphenyldicarboxylic acid, hydroxyl ionic liquid functionalized carboxylic acid ligand and metal zirconium salt are added to a solvent, and then a catalyst is added. After ultrasonic-assisted dispersion and mixing, the mixture is added to a stainless steel reactor lined with polytetrafluoroethylene, reacted at 80-200°C, cooled to room temperature after the reaction, and the obtained white solid is washed with N,N-dimethylformamide and anhydrous ethanol multiple times, and then dried to obtain the ionic liquid functionalized metal-organic framework material, wherein the catalyst is one or more of formic acid, glacial acetic acid, sulfuric acid, benzenesulfonic acid, p-toluenesulfonic acid or benzoic acid; and the metal zirconium salt is one or more of ZrCl4, zirconyl chloride or zirconyl nitrate.

2. The ionic liquid functionalized metal organic framework material with high water absorption capacity according to claim 1, characterized in that: The molar ratio of the hydroxy ionic liquid functionalized carboxylic acid ligand to 4,4-biphenyldicarboxylic acid is 1:10 to 10:

1.

3. The ionic liquid functionalized metal organic framework material with high water absorption capacity according to claim 1, characterized in that: The molar ratio of the hydroxy ionic liquid functionalized carboxylic acid ligand to 4,4-biphenyldicarboxylic acid is 9:

1.

4. The ionic liquid functionalized metal-organic framework material with high water absorption capacity according to claim 1, characterized in that: The solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dioxane, ethanol, methanol, acetonitrile, tetrahydrofuran, mesitylene, chloroform or dichloromethane.

5. The ionic liquid functionalized metal organic framework material with high water absorption capacity according to claim 1, characterized in that The specific preparation steps of the ionic liquid functionalized metal organic framework material with high water absorption capacity are as follows: 0.036 mmol 4,4-biphenyldicarboxylic acid, 0.324 mmol hydroxy ionic liquid functionalized carboxylic acid ligand [H2BPDC-DMEA] + Cl - The reaction mixture was added with 0.36 mmol ZrCl4 into 15 mL N,N-dimethylformamide, and then 1.65 mL glacial acetic acid was added. After ultrasonic-assisted dispersion and mixing, the mixture was added into a 50 mL stainless steel reactor lined with polytetrafluoroethylene and reacted at 120 °C for 24 h. After the reaction, the reaction was cooled to room temperature. The obtained white solid was washed with N,N-dimethylformamide and anhydrous ethanol for several times, and then dried in vacuum at 120 °C to obtain an ionic liquid functionalized metal-organic framework material with a specific surface area of ​​484 m 2 ·g -1 , with a pore volume of 0.34 cm 3 ·g -1 The pore size is 0.71 nm. At 25.0℃, the adsorption capacity of the ionic liquid functionalized metal organic framework material for water is 2.44 g / g, and the storage density of water reaches 7 g / cm 3 above.

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