Metal-organic framework materials, preparation methods thereof, and applications in air water collection

Abstract

The present invention discloses a metal-organic framework (MOF) material, its preparation method, and its application in air water collection. The MOF material is formed by substitutional coordination between an organic ligand and a Zr6 metal cluster. The organic ligand has the following chemical structure: #imgabs0# The Zr6 metal cluster has the following chemical structure: #imgabs1# The preparation method of the present invention first synthesizes an organic ligand containing a five-membered sulfur heterocycle using 1,1,2,2-tetra(thiophene-2-yl)ethylene as a raw material under specific and appropriate conditions. The organic ligand is then reacted with the Zr6 metal cluster under specific and appropriate conditions to prepare a stable MOF material. The synthesis and preparation methods of the present invention are simple, easy to operate, and low-cost.

Description

Technical Field

[0001] The present invention relates to the field of new materials, and in particular to a metal organic framework material, a preparation method thereof, and an application thereof in air water collection. Background Art

[0002] Water scarcity is one of the major challenges facing the world today, and the severity of water stress is expected to continue to worsen in the foreseeable future. To alleviate this current water shortage, technologies such as seawater desalination and air water harvesting are being developed and applied. Seawater desalination has achieved some success, but it is only economically viable in coastal areas. For landlocked countries and regions, practical feasibility is low due to expensive water transport infrastructure. In contrast, atmospheric water harvesting is one of the key technologies for addressing water shortages in remote areas and offers attractive application prospects. Adsorbent-assisted atmospheric water capture offers the greatest feasibility, as water vapor is adsorbed and fixed in the pores of the adsorbent. It can then be desorbed and collected by varying temperature or pressure to produce pure drinking water. This technology reduces the sensible heat required to cool the air, making it suitable for arid conditions. It also eliminates time and regional limitations, broadening its application scope.

[0003] Metal-organic frameworks (MOFs) are crystalline porous materials composed of secondary structural units and organic ligands. They have the characteristics of high porosity and easy control, and have attracted increasing attention from researchers. Based on the design of appropriate metal clusters and linkers, functional groups can be introduced into MOFs and various topological structures can be achieved, which enables more effective adsorption and fixation of water molecules in the pores of MOFs. Therefore, MOFs have become promising adsorbents due to their tunability, skeleton rigidity and water stability. MOF-801, reported by Yaghi's group in 2014, is one of the earliest discovered water-collecting MOFs with high stability and capacity. In the past decade, there has been an increasing number of studies on atmospheric water collection based on MOFs, and some exciting results have been achieved. However, the design and development of MOFs with high water stability and large capacity for water collection remains the research focus of MOF-based adsorbents.

[0004] Patent specification CN115193403A discloses the preparation of a metal-organic framework material, ZPF-2-MX, and its application for enriching water in dry air. This metal-organic framework material is obtained by coordination between the organic ligand 2-hydroxy-5-halopyrimidine and a divalent metal ion. The metal-organic framework material obtained by this method has the characteristics of reversible adsorption and desorption of water vapor, low active humidity, a large specific surface area, and a regular and adjustable pore structure, which is conducive to the collection of liquid water in dry air. This metal-organic framework material can absorb water vapor in dry air at low temperatures and release it at high temperatures, thereby condensing and collecting it as liquid water.

[0005] Patent publication number CN113332959A discloses a novel, highly stable aluminum-based metal-organic framework (MOF) material, its preparation method, and its application in air water absorption. The aluminum-based MOFs material is a solid crystalline material with a three-dimensional network structure, with the general formula Al(OH)L, where L is a six-membered nitrogen-containing heterocyclic dicarboxylic acid organic ligand. The MOFs can be used as an adsorbent to absorb water vapor from air. The preparation process involves introducing nitrogen heteroatoms into the organic ligands to modify and alter the distribution of hydrophilic sites within the MOF pores, transforming the framework from flexible to rigid. This increases the material's water absorption capacity at low humidity and reduces the energy required for desorption. Summary of the Invention

[0006] In a first aspect, the present invention provides a metal-organic framework material with novel structure, simple synthesis, excellent properties, high water stability and high water vapor adsorption capacity, which can be used for water adsorption.

[0007] Specifically, the metal organic framework material is formed by substitution and coordination connection between organic ligands and Zr6 metal clusters. The formation process can be seen in Figure 1 .

[0008] The organic ligand has the chemical structure shown below:

[0009]

[0010] The Zr6 metal cluster has the chemical structure shown below:

[0011]

[0012] In the process of substitution coordination, the organic ligand forms a coordination connection with the Zr6 metal cluster by using its carboxyl group to replace OCO in the Zr6 metal cluster with the same structure.

[0013] In a second aspect, the present invention provides a method for preparing the metal organic framework material according to the first aspect, comprising the steps of:

[0014] (1) Under anhydrous and oxygen-free conditions, 1,1,2,2-tetra(thiophen-2-yl)ethylene is added to tetrahydrofuran, butyl lithium is added at -75 to -80°C, carbon dioxide gas is introduced at -75 to -80°C and stirred for a period of time after thorough mixing and reaction at -80°C to room temperature, the reaction is quenched with hydrochloric acid, and extracted with dichloromethane. The obtained organic phase is washed with saturated brine, dried over anhydrous sodium sulfate, and the organic solvent is dried to obtain the organic ligand;

[0015] (2) Adding the organic ligand and ZrOCl2 into a mixed solution of DMF (N,N-dimethylformamide) and FA (formic acid) to carry out a solvothermal reaction to obtain the metal organic framework material.

[0016] The present invention first designed and synthesized a novel organic ligand containing a five-membered sulfur heterocycle. Subsequently, under specific and appropriate conditions, a stable metal-organic framework (MOF) material was synthesized. This MOF material exhibits excellent stability in water and excellent reproducibility in multiple rounds of water adsorption testing. The MOF material, containing a five-membered sulfur heterocycle, exhibits stable structure and crystal form after long-term storage, allowing for long-term use.

[0017] In step (1), 1,1,2,2-tetra(thiophen-2-yl)ethylene is a material disclosed in the prior art, and has the chemical structure shown below:

[0018]

[0019] Specifically, 1,1,2,2-tetrakis(thiophen-2-yl)ethylene can be obtained by existing technology. For example, 1,1,2,2-tetrakis(thiophen-2-yl)ethylene can be prepared by referring to the existing technology document Chem.Sci., 2017, 8, 2629-2639.

[0020] In step (1), the ratio of 1,1,2,2-tetra(thiophen-2-yl)ethylene to tetrahydrofuran can be 0.5-1.5 g:100 mL.

[0021] In step (1), the molar ratio of 1,1,2,2-tetra(thiophen-2-yl)ethylene to butyl lithium may be 0.5 to 1.5:10.

[0022] In step (1), the butyl lithium can be added in the form of a butyl lithium n-hexane solution. Furthermore, the concentration of butyl lithium in the butyl lithium n-hexane solution can be 2 to 3 M.

[0023] In step (1), it is preferred to introduce an excess of carbon dioxide gas. For example, the amount of carbon dioxide introduced may be 100 equivalents.

[0024] In step (1), the reaction temperature can be -80°C to room temperature.

[0025] In one embodiment, in step (2), the mass ratio of ZrOCl2 to the organic ligand is not less than 2:1.

[0026] In step (2), the volume ratio of DMF to FA can be 1:0.2 to 0.4.

[0027] In step (2), the usage ratio of the organic ligand to DMF can be 30 mg:1-3 mL.

[0028] In one embodiment, in step (2), the temperature of the solvent thermal reaction is 125-135° C., and the time is 36-72 hours.

[0029] In step (2), after the solvothermal reaction is completed, the following post-treatment operation can be performed: the solid product is washed and soaked with DMF and then soaked with acetone, and then vacuum dried to obtain the metal organic framework material. Furthermore, the vacuum drying temperature can be 55-65°C.

[0030] The preparation method provided by the present invention first uses 1,1,2,2-tetrakis(thiophen-2-yl)ethylene as a raw material to synthesize an organic ligand containing a five-membered sulfur heterocycle under specific and appropriate conditions. This ligand is then combined with a Zr6 metal cluster under specific and appropriate conditions to prepare a stable metal-organic framework material. The synthesis and preparation methods of the present invention have a simple route, are easy to operate, and are low in cost.

[0031] In a third aspect, the present invention provides an application of the metal organic framework material described in the first aspect in air water collection.

[0032] In a fourth aspect, the present invention provides a method for collecting water from air, using the metal organic framework material described in the first aspect as an adsorbent to adsorb water vapor in the air to achieve air water collection.

[0033] In the third and fourth aspects, the metal organic framework material is preferably activated before being used for air water collection. The activation operation includes vacuum heating the metal organic framework material at 115-125°C for more than 2 hours, which is conducive to better adsorption of water vapor in the air.

[0034] At room temperature, the water vapor adsorption capacity of the metal organic framework material is 15.8 mmol g when P / P0=0.3. -1 When P / P0=0.9, the adsorption capacity of water vapor is 25.5mmol g -1 , and showed excellent reproducibility in three cycles of water adsorption experiments. This is because, on the one hand, the hydrophilicity of the heteroatoms in the structure allows for higher water adsorption at lower pressures; on the other hand, the stable MOF structure makes the material highly water-stable, with good reproducibility of water adsorption and stable properties, allowing for long-term use.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. The present invention creatively synthesizes a novel organic ligand containing a five-membered sulfur heterocycle.

[0037] 2. The preparation method of the organic ligand containing a five-membered sulfur heterocycle provided by the present invention has a simple route, easy operation, high yield and low cost.

[0038] 3. The preparation method of the metal organic framework material provided by the present invention is simple and suitable for large-scale synthesis.

[0039] 4. The metal organic framework material provided by the present invention has high water stability and high-capacity water vapor adsorption performance, and has practical application value in collecting water in the atmosphere.

[0040] 5. The metal organic framework material provided by the present invention has a stable structure and crystal form after long-term storage and can be used for a long time. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 Schematic diagram of the metal-organic framework material formed by substitutional coordination connection between the organic ligand of the present invention and the Zr6 metal cluster.

[0042] Figure 2 The powder X-ray diffraction (PXRD) patterns of Zr-TSS activated in water and acetone in Example 3 are measured, and the comparison with the simulated PXRD (Simulated line).

[0043] Figure 3 These are the nitrogen adsorption and desorption curves obtained when Zr-TSS was activated in water and acetone in Example 3.

[0044] Figure 4 Attached is a diagram showing three rounds of water absorption and desorption of sample A in Example 3. DETAILED DESCRIPTION

[0045] The present invention will be further described below with reference to the accompanying drawings and specific examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0046] Example 1

[0047] Synthesis method of organic ligand TSS containing five-membered sulfur heterocycle:

[0048]

[0049] 1 g of 1,1,2,2-tetra(thiophen-2-yl)ethylene was weighed into a 250 mL side-spout flask. The atmosphere was replaced with nitrogen and, under anhydrous and oxygen-free conditions, 100 mL of anhydrous tetrahydrofuran was introduced. The mixture was then placed in a -78°C cold bath. 11.2 mL of a 2.5 M butyllithium solution in n-hexane was slowly added dropwise. After the addition was complete, the mixture was stirred at -78°C for 30 minutes. The mixture was then transferred to room temperature and stirred for 3 hours to allow the lithiation reaction to complete, resulting in a turbid solution. The mixture was then transferred to -78°C again, and carbon dioxide (CO2) gas was continuously introduced. The refrigeration was turned off and the mixture was stirred overnight. The reaction was quenched with 2 M hydrochloric acid and extracted twice with dichloromethane. The combined organic phases were washed with saturated brine, dried over anhydrous sodium sulfate, and the organic solvent was evaporated to obtain the product, TSS (1.46 g, 98% yield). 1 H NMR (600MHz, DMSO-d6): δ13.31(s,4H),7.61(d,4H),7.01(d,4H).

[0050] Example 2

[0051] Synthesis method of metal-organic framework material Zr-TSS:

[0052] Take TSS (30 mg) and ZrOCl2 (60 mg) prepared in Example 1 and place them in a 15 mL Pyrex vial, then add 2 mL DMF and 0.6 mL FA. After ultrasonication until the solution is clear, place it in a 130°C oven for solvent thermal reaction for two days. After cooling to room temperature, centrifuge to remove the mother liquor and wash twice with new DMF. Then soak it in DMF for two days, replacing new DMF three times during this period, and then soak it in acetone for two days, replacing new acetone three times during this period. Vacuum drying at 60°C to obtain a metal organic framework material, named Zr-TSS, with a yield of 90%.

[0053] Example 3

[0054] The Zr-TSS obtained in Example 2 was heated and activated at 120°C in vacuum for 6 hours. The obtained sample was designated as sample A and used for PXRD test. Figure 2 The experimental line is basically consistent with the peak position of the simulated PXRD curve (Simulated line), indicating that the designed MOF was successfully prepared. Sample A was used for nitrogen adsorption and desorption test at 77K, and the results are shown in Figure 3 Sample A was used for three consecutive rounds of water vapor adsorption and desorption tests, and the results are shown in Figure 4 When P / P0=0.3, the adsorption capacity of sample A on water vapor is 15.8mmolg -1 When P / P0=0.9, the adsorption capacity of sample A on water vapor is 25.5mmol g -1, and the reproducibility was excellent in three rounds of cyclic water adsorption experiments.

[0055] The Zr-TSS obtained in Example 2 was soaked in water for 24 hours, then taken out and dried under vacuum at 60°C, and activated by heating at 120°C under vacuum for 6 hours. The obtained sample was designated as sample B and used for PXRD test. The results are shown in Figure 2 The activated from water line. Sample B was used for nitrogen adsorption and desorption test at 77K. The results are shown in Figure 3 .

[0056] from Figure 2 The PXRD patterns and Figure 3 From the adsorption-desorption test results, it can be seen that the PXRD curves of the samples (sample A and sample B) before and after water treatment are basically consistent with the adsorption-desorption curves, indicating that Zr-TSS maintains its crystal form and porous structure and has excellent water stability.

[0057] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A metal organic framework material, characterized in that The metal organic framework material is formed by substitution and coordination connection between organic ligands and Zr6 metal clusters; The organic ligand has the chemical structure shown below: The Zr6 metal cluster has the chemical structure shown below:

2. The method for preparing a metal organic framework material according to claim 1, wherein: Including steps: (1) Under anhydrous and oxygen-free conditions, 1,1,2,2-tetra(thiophen-2-yl)ethylene is added to tetrahydrofuran, butyl lithium is added at -75 to -80°C, carbon dioxide gas is introduced at -75 to -80°C and stirred for a period of time after thorough mixing and reaction at -80°C to room temperature, the reaction is quenched with hydrochloric acid, and extracted with dichloromethane. The obtained organic phase is washed with saturated brine, dried over anhydrous sodium sulfate, and the organic solvent is dried to obtain the organic ligand; (2) adding the organic ligand and ZrOCl2 into a mixed solution of DMF and FA to carry out a solvothermal reaction to obtain the metal organic framework material.

3. The preparation method according to claim 2, characterized in that In step (1), the ratio of 1,1,2,2-tetra(thiophen-2-yl)ethylene to tetrahydrofuran is 0.5-1.5 g:100 mL.

4. The preparation method according to claim 2, characterized in that In step (1): The molar ratio of 1,1,2,2-tetra(thiophen-2-yl)ethylene to butyl lithium is 0.5 to 1.5:10; The butyl lithium is added in the form of a butyl lithium n-hexane solution; The concentration of butyl lithium in the n-hexane solution of butyl lithium is 2-3M.

5. The preparation method according to claim 2, characterized in that In step (1), an excess amount of carbon dioxide gas is introduced.

6. The preparation method according to claim 2, characterized in that In step (2): The mass ratio of ZrOCl2 to the organic ligand is not less than 2:1; The volume ratio of DMF and FA is 1:0.2-0.4; The usage ratio of the organic ligand and DMF is 30 mg: 1-3 mL; The temperature of the solvent thermal reaction is 125-135° C., and the time is 36-72 hours.

7. The preparation method according to claim 2, characterized in that In step (2), after the solvothermal reaction is completed, the following post-treatment operation is further performed: the solid product is washed with DMF, soaked in acetone, and then vacuum-dried to obtain the metal organic framework material; The vacuum drying temperature is 55-65°C.

8. Use of the metal organic framework material according to claim 1 in air water collection.

9. A method for collecting water from air, characterized in that: The metal organic framework material according to claim 1 is used as an adsorbent to adsorb water vapor in the air to achieve air water collection.

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