Water-resistant metal organic framework material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of adsorption materials, and particularly relates to a water-resistant metal organic framework material as well as a preparation method and application thereof. The preparation method comprises the following steps: mixing magnesium salt, an organic ligand, inorganic alkali, water and low alcohol, and carrying out a co-precipitation reaction on the obtained mixed solution to obtain the water-resistant metal organic framework material, the organic ligands include 2, 5-dihydroxyterephthalic acid and a polycarboxylic acid chelating agent. The polycarboxylic acid chelating agent is introduced into an Mg-MOF-74 structure, the polycarboxylic acid chelating agent is coordinated with unsaturated metal sites in a framework, meanwhile, carboxyl carried by the polycarboxylic acid chelating agent provides rich water adsorption sites, water molecules form a stable network in pore channels through hydrogen bonds, the hydrogen bond network and CO2 molecules generate a synergistic adsorption effect, and the adsorption efficiency is improved. Therefore, the CO2 adsorption capacity is obviously improved under the condition of relatively high relative humidity. The material disclosed by the invention shows excellent adsorption capacity, selectivity and cycling stability in a high-humidity environment, and is suitable for adsorbing CO2 in a water-containing environment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of adsorption materials, and particularly relates to a water-resistant metal organic framework material and a preparation method and application thereof. BACKGROUND

[0002] Carbon dioxide (CO2) is one of the main greenhouse gases causing global climate change, and the flue gas emission of energy, chemical and metallurgical industries is the main emission source. Taking a coal-fired power plant as an example, the flue gas emitted by the coal-fired power plant usually contains 12-15% of CO2, 70-75% of nitrogen, 3-7% of water vapor and a small amount of impurity gas. With the CO2 emission characteristics of such high humidity, the traditional carbon emission reduction method has been difficult to meet the low energy consumption and sustainable carbon emission reduction demand. Therefore, developing a high-efficiency CO2 capture technology suitable for industrial flue gas has become an important way to realize the double carbon goal and cope with climate change.

[0003] At present, in view of the characteristics of large industrial flue gas emission, low CO2 content and a large amount of water vapor, the commonly used CO2 capture method is a solution absorption method and a solid adsorption method. Among them, the solid adsorption method has the advantages of simple process, mild operating conditions, low energy consumption, no equipment corrosion and the like, and is one of the most promising capture methods at present. Traditional carbon dioxide adsorption materials include activated carbon, zeolite molecular sieve, porous metal oxide and the like, but they still have certain limitations in structure, performance and application, for example, the specific surface area of activated carbon varies with different synthesis methods and raw materials, resulting in unstable adsorption performance; the adsorption capacity of zeolite molecular sieve is low at low partial pressure, and the CO2 adsorption capacity sharply decreases under the condition of containing water; for porous metal oxide, a dense film is easily formed on the surface, resulting in a decrease in CO2 adsorption performance.

[0004] Metal organic framework (MOFs) is a new type of organic-inorganic hybrid material composed of metal ions or metal clusters and organic ligands through coordination bonds. Compared with traditional porous materials, MOFs have a high specific surface area and pore volume, and also have unsaturated metal centers (OMS), which show unique advantages in adsorption and separation of carbon dioxide. Among them, Mg-MOF-74 has a high density of unsaturated metal sites, so that it has a strong adsorption capacity for CO2 and shows a high adsorption capacity, but the water resistance of Mg-MOF-74 is poor, and the CO2 adsorption capacity sharply decreases under humid conditions, which greatly limits the application of Mg-MOF-74 in flue gas carbon capture. SUMMARY

[0005] In view of this, the purpose of the present application is to provide a water-resistant metal organic framework material and a preparation method and application thereof. The metal organic framework adsorption material prepared by the present application has good water resistance.

[0006] The application provides a preparation method of a water-resistant metal organic framework material, comprising the following steps: The magnesium salt, the organic ligand, the inorganic base, water and the lower alcohol are mixed, and a co-precipitation reaction is performed on the obtained mixed solution, and solid-liquid separation is performed to obtain the water-resistant metal organic framework material. The organic ligand comprises 2,5-dihydroxyterephthalic acid and a polycarboxylic acid chelating agent, and the polycarboxylic acid chelating agent comprises one or more of ethyleneglycolbis(2-aminoethylether)tetraacetic acid, 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid and ethylenediaminetetraacetic acid.

[0007] Preferably, the molar ratio of the 2,5-dihydroxyterephthalic acid and the polycarboxylic acid chelating agent is 1:0.02-0.1.

[0008] Preferably, the magnesium salt comprises one or more of magnesium nitrate, magnesium acetate and magnesium chloride.

[0009] Preferably, the molar ratio of the magnesium salt and the organic ligand is 2-4:1.

[0010] Preferably, the inorganic base is sodium hydroxide, and the lower alcohol is methanol or ethanol.

[0011] Preferably, the mixing of the magnesium salt, the organic ligand, the inorganic base, water and the lower alcohol is as follows: the magnesium salt is dissolved in the lower alcohol to obtain a magnesium salt alcohol solution; the organic ligand is dissolved in an aqueous solution of the inorganic base to obtain a ligand alkali solution; and the ligand alkali solution is added dropwise into the magnesium salt alcohol solution.

[0012] Preferably, the temperature of the co-precipitation reaction is 20-35 DEG C, and the time is 12-36 h.

[0013] The application further provides the water-resistant metal organic framework material obtained by the preparation method.

[0014] The application further provides application of the water-resistant metal organic framework material in CO2 adsorption under high-humidity conditions.

[0015] Preferably, the CO2 adsorption is selective adsorption of CO2 from a mixed gas, and the mixed gas comprises CO2, N2 and H2O.

[0016] Compared with the prior art, the application has the following beneficial effects: The application provides a preparation method of a water-resistant metal organic framework material, in which a polycarboxylic acid chelating agent is introduced in situ in a one-step coprecipitation method during the synthesis of Mg-MOF-74, so that the polycarboxylic acid chelating agent forms a stable coordination with magnesium ions, the coordination structure not only maintains the original framework pore structure, but also constructs a stable hydrogen bond network in the material channel, and significantly improves the structural stability and CO2 adsorption capacity of the material under humid conditions.

[0017] In the preparation process of the water-resistant metal organic framework material, metal salt, 2,5-dihydroxyterephthalic acid ligand (H4DOBDC) and polycarboxylic acid chelating agent are mixed in a slow dropwise manner, the coordination reaction is optimized, and the controllability of the reaction is further enhanced in an alkaline environment at a low temperature (such as room temperature), which is specifically embodied as follows: in the first stage, the ligand alkali solution is slowly added to the magnesium salt alcohol solution under room temperature conditions, so as to avoid non-uniform distribution of metal sites and premature nucleation, and ensure efficient coordination between metal ions and ligands. In the second stage (during the room temperature coprecipitation reaction), the carboxyl oxygen atoms and phenolic hydroxyl oxygen atoms in H4DOBDC are coordinated with metal ions, and a chain structure is gradually formed under the connection of metal-oxygen coordination bonds. In this process, the polycarboxylic acid chelating agent is simultaneously coordinated with part of the magnesium ions, further promoting the crosslinking between the chain segments and the diversity of the internal chemical structure. This coordination reaction ensures uniform distribution of metal sites and avoids aggregation or disordered coordination of metal ions, and finally forms a water-resistant metal organic framework material.

[0018] The water-resistant metal organic framework material prepared by the application has rich microporous and mesoporous channels, small crystal grain size and large specific surface area, and provides more adsorption sites for gas molecules. At room temperature, the coordination of the chelating agent with H4DOBDC is competitive, and an asymmetric corrugated chain of Mg-O-Mg along the c-axis is formed through a mixed coordination mode of bidentate coordination and μ2 bridge coordination. This corrugated chain structure forms a highly ordered and stable metal-oxygen coordination network in the framework, effectively enhancing the structural stability of the material.

[0019] The water-resistant metal organic framework material prepared by the application avoids the problem of pore blockage caused by surface coating by introducing the chelating agent, thereby providing additional polar sites to interact with water molecules while keeping the original adsorption sites unchanged, weakening the competitive adsorption of CO2-H2O, which not only improves the selective adsorption of CO2 of the material, but also ensures that CO2 molecules can preferentially occupy the adsorption sites under high humidity conditions, thereby maintaining the high adsorption performance of the material in a humid environment.

[0020] The prepared water-resistant metal organic framework material shows a significant CO2 adsorption enhancement effect in a high humidity environment, and the effect is due to the synergistic effect of the captured hydrazine and CO2 formed by water molecules. Water molecules interact with the chelating agent in the framework through hydrogen bonds to form stable water adsorption sites, and these water molecules not only do not affect the stability of the structure, but also can promote the conversion of adsorbed CO2 to carbonic acid and bicarbonate, significantly enhancing the CO2 capture efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can also be obtained according to these drawings without creative labor for those skilled in the art.

[0022] Figure 1 XRD pattern of the MOF-4 sample in Example 4; Figure 2 SEM pattern of the MOF-4 sample in Example 4; Figure 3 The CO2 adsorption amount and the change amount of the relative dry flue gas of the adsorption material prepared in Examples 1-8 and Comparative Example 1 under the conditions of 41℃, normal pressure, 15CO2 / 85N2, RH=86%. DETAILED DESCRIPTION

[0023] The present application provides a preparation method of a water-resistant metal organic framework material, comprising the following steps: Mixing a magnesium salt, an organic ligand, an inorganic base, water and a lower alcohol, and performing a co-precipitation reaction on the obtained mixed solution, and then performing solid-liquid separation to obtain a water-resistant metal organic framework material; The organic ligand comprises 2,5-dihydroxyterephthalic acid and a polycarboxylic acid chelating agent, and the polycarboxylic acid chelating agent comprises one or more of ethylene glycol bis(2-aminoethylether)tetraacetic acid (EGTA), 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) and ethylenediaminetetraacetic acid (EDTA).

[0024] In the present application, the materials and equipment used are commercially available in the art unless otherwise specified.

[0025] In the present application, the molar ratio of 2,5-dihydroxyterephthalic acid and polycarboxylic chelating agent is preferably 1:0.02~0.1 (i.e. 10~50:1), and can be 10:1, 14:1, 20:1 or 50:1. The present application prepares Mg-MOF-74 containing polycarboxylic chelating agent by mixed ligand method, creates "CO2-H2O molecule" double adsorption sites, weakens the competitive adsorption of carbon dioxide and water vapor on metal active sites, and at the same time in the limited pore channel, H2O molecules can provide proton transfer and hydrogen bond network, promote CO2 to bicarbonate / carbonate conversion, and improve the CO2 adsorption capacity of metal organic framework material under high humidity conditions. The material prepared by the molar ratio of the present application shows excellent CO2 adsorption performance.

[0026] In the present application, the magnesium salt preferably includes one or more of magnesium nitrate, magnesium acetate and magnesium chloride, and can be specifically hexahydrate magnesium nitrate, tetrahydrate magnesium acetate or hexahydrate magnesium chloride. The molar ratio of the magnesium salt and the organic ligand is 2~4:1, and can be specifically 2:1.

[0027] In the present application, the inorganic base is preferably sodium hydroxide.

[0028] In the present application, the lower alcohol is preferably methanol or ethanol, and the water is preferably deionized water.

[0029] In the present application, the mixing of the magnesium salt, the organic ligand, the inorganic base, the water and the lower alcohol is preferably as follows: dissolving the magnesium salt in the lower alcohol to obtain a magnesium salt alcohol solution; dissolving the organic ligand in the aqueous solution of the inorganic base to obtain a ligand base solution; and adding the ligand base solution dropwise to the magnesium salt alcohol solution. The magnesium salt is dissolved in the lower alcohol under stirring, and the stirring time is preferably 10~30 min, and can be specifically 20 min; the concentration of the magnesium salt in the magnesium salt alcohol solution is preferably 0.5 mol / L. The aqueous solution of the inorganic base is obtained by mixing the inorganic base and water, and the concentration of the aqueous solution of the inorganic base is preferably 0.8~1.2 mol / L, and can be specifically 1 mol / L; the organic ligand is dissolved in the aqueous solution of the inorganic base under stirring, and the stirring time is preferably 10~30 min, and can be specifically 20 min; the concentration of the organic ligand in the ligand base solution is preferably 0.25 mol / L. The volume ratio of the ligand base solution and the magnesium salt alcohol solution is preferably 1:1; the dropwise adding process is preferably uniform dropwise adding, and the dropwise adding preferably uses a peristaltic pump, and the dropwise adding time is preferably 40~60 min, and can be specifically 50 min. The dropwise adding is preferably carried out at room temperature, and can be specifically 25℃.

[0030] In the present application, the temperature of the co-precipitation reaction is preferably 20-35℃, and can be specifically 25℃ (room temperature), and the time is preferably 12-36h, and can be specifically 24h. During the co-precipitation reaction, magnesium ions as the main metal center are coordinated with the carboxyl oxygen and phenolic hydroxyl oxygen atoms in the ligand 2,5-dihydroxyterephthalic acid (H4DOBDC), and at the same time, the polycarboxylate chelating agent is coordinated with part of the magnesium ions, gradually forming a chain structure with metal-oxygen coordination bonds as the connecting unit. With the progress of the reaction, different chain segments are further crosslinked to obtain the water-resistant metal organic framework material.

[0031] In the present application, after the solid-liquid separation, the obtained precipitated product is preferably sequentially washed and dried. The washing is preferably 6 times of washing with 40-50mL of methanol first, and 4-6 times of washing with a mixed solution of methanol and water, and can be specifically 5 times; the volume ratio of methanol to water in the mixed solution of methanol and water is preferably 0.8-1.5:1, and can be specifically 1:1; the washing liquid after washing is not obviously turbid; the drying is preferably vacuum drying, and the temperature of the vacuum drying is preferably 80℃, and the time is preferably overnight.

[0032] The preparation method provided by the present application can obtain a material with high CO2 adsorption capacity; the preparation method of the present application has the advantages of easy availability of raw materials, mild reaction conditions (room temperature conditions can be used for reaction), strong controllability, simple process, easy reaction scaling-up, good scalability and industrialization potential.

[0033] The present application also provides a water-resistant metal organic framework material obtained by the preparation method of the above technical solution, which is a polycarboxylate chelating agent modified Mg-MOF-74.

[0034] The water-resistant metal organic framework material provided by the present application uses magnesium as a metal source, 2,5-dihydroxyterephthalic acid as a main ligand (supporting framework), and a polycarboxylate chelating agent as an auxiliary ligand. The present application can improve the CO2 adsorption performance of the metal organic framework material Mg-MOF-74 under humid conditions by modifying the material with a polycarboxylate chelating agent, and the material exhibits excellent CO2 adsorption capacity under humid conditions. The water-resistant metal organic framework material of the present application is a MOF-based CO2 adsorbent with high adsorption capacity and good stability.

[0035] The present application also provides the application of the water-resistant metal organic framework material of the above technical solution in CO2 adsorption under high humidity conditions.

[0036] In the present application, the water-resistant metal organic framework material is preferably activated before use, the activation is preferably carried out in an inert atmosphere, preferably an argon atmosphere, the temperature of the activation is preferably 100-200℃, specifically 150℃, and the time is preferably 4-8h, specifically 6h; the activation is preferably carried out at normal pressure. The water-resistant metal organic framework material is preferably pressed into tablets and sieved before the activation, and the mesh number of the particles obtained after the pressing and sieving is preferably 40-60 mesh.

[0037] In the present application, the temperature of the CO2 adsorption is preferably 15-80℃, specifically 41℃, and the pressure is preferably 1atm (normal pressure). The relative humidity of the high humidity condition is preferably 30-90%.

[0038] In the present application, the CO2 adsorption is preferably selective adsorption of CO2 from a mixed gas; the mixed gas includes dry CO2 / N2 mixed gas or humid CO2 / N2 mixed gas; the dry CO2 / N2 mixed gas includes CO2 and N2; the humid CO2 / N2 mixed gas includes CO2, N2 and H2O; the volume fraction of CO2 in the mixed gas is preferably 10-15%, more preferably 13.95-15%, the volume fraction of N2 is preferably 78.85-85%, and the volume fraction of H2O is preferably 0-7.2%. The relative humidity of the humid CO2 / N2 mixed gas is preferably 30-90%, specifically 30%, 60% or 86%, and the relative humidity can be achieved by customizing the bubbler and air bath. The humid CO2 / N2 mixed gas of the present application is close to the real flue gas condition.

[0039] The water-resistant metal organic framework material of the present application can be recycled after desorption of CO2, the temperature of the desorption is preferably 180-250℃, specifically 200℃, and the time is preferably 4h.

[0040] The water-resistant metal organic framework material provided by the present application is suitable for CO2 capture in humid mixed gas, and can maintain its structure and physicochemical properties stable during the process. In the adsorption process, the water-resistant metal organic framework establishes double adsorption sites, decouples the adsorption paths of carbon dioxide and water vapor, and in the confined pore channel, water can provide proton transfer and hydrogen bond network, promote the conversion of CO2 to bicarbonate / carbonate, and improve the CO2 adsorption capacity of the metal organic framework under high humidity conditions.

[0041] The anti-water type metal organic framework material has excellent water resistance and can selectively separate and adsorb CO2 from a high-humidity CO2 and N2 mixed gas.

[0042] In order to further illustrate the present application, the anti-water type metal organic framework material, the preparation method and the application thereof provided by the present application are described in detail below in combination with the drawings and examples, but they should not be understood as limiting the protection scope of the present application.

[0043] Example 1 1) 2 g of 2,5-dihydroxyterephthalic acid was dissolved in 40 mL of sodium hydroxide solution (the concentration of the sodium hydroxide solution was 1 mol / L), and a certain amount of ethylenediamine tetraacetic acid (a polycarboxylic acid chelating agent) was added, so that the molar ratio of 2,5-dihydroxyterephthalic acid to the polycarboxylic acid chelating agent was 20:1, and the mixture was stirred for 20 min; 2) 5.18 g of magnesium nitrate hexahydrate (a magnesium salt) was dissolved in 40 mL of methanol and stirred for 20 min; 3) The two solutions were mixed (the ligand alkali solution was added dropwise into the magnesium salt alcohol solution), the dropwise adding time was 50 min, and the mixture was reacted at 25℃ for 24 h, then washed with methanol and water, first washed with methanol for 6 times, then washed with a mixed solution of methanol and water (the volume ratio was 1:1) for 5 times, filtered and dried in a vacuum oven (the temperature was 80℃) to obtain the anti-water type metal organic framework adsorption material, which was recorded as MOF-1.

[0044] Application Example 1 The anti-water type metal organic framework adsorption material (MOF-1) prepared in Example 1 was pressed into a tablet and sieved, and 0.4 g of the tablet was loaded into a quartz tube to perform an adsorption separation experiment on a multi-component adsorption breakthrough instrument.

[0045] Firstly, the adsorption material was activated at 150℃ under argon atmosphere for 6 h; then, the separation performance test (carbon dioxide adsorption capacity test) of CO2 / N2 (the volume ratio of CO2 to N2 in the mixed gas was 15% / 85%, recorded as 15CO2 / 85N2) was performed at 41℃ under normal pressure (dry), and the result was recorded as MOF-1-D.

[0046] Using the same experimental procedure, the carbon dioxide adsorption capacity test was performed at 41℃, normal pressure, 15CO2 / 85N2, different humidity (RH=30%, RH=60%, RH=86%), and the results were recorded as MOF-1-L (RH=30%), MOF-1-M (RH=60%), MOF-1-H (RH=86%), respectively.

[0047] The CO2 adsorption capacity and the amount of change with humidity are shown in Table 1.

[0048] Example 2 The difference from Example 1 is only that the polycarboxylic acid chelating agent in step 1) is replaced by 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid. The obtained water-resistant metal organic framework adsorbent material is recorded as MOF-2.

[0049] Example 3 The difference from Example 1 is only that the polycarboxylic acid chelating agent in step 1) is replaced by ethylenediaminetetraacetic acid, and the molar ratio of 2,5-dihydroxyterephthalic acid to polycarboxylic acid chelating agent is 50:1. The obtained water-resistant metal organic framework adsorbent material is recorded as MOF-3.

[0050] Example 4 The difference from Example 3 is only that the molar ratio of 2,5-dihydroxyterephthalic acid to polycarboxylic acid chelating agent in step 1) is 20:1. The obtained water-resistant metal organic framework adsorbent material is recorded as MOF-4.

[0051] Figure 1 is the XRD pattern of the MOF-4 sample in Example 4; Figure 2 is the SEM pattern of the MOF-4 sample in Example 4; it can be seen that the synthesized MOF has good crystallinity and regular morphology.

[0052] Example 5 The difference from Example 3 is only that the molar ratio of 2,5-dihydroxyterephthalic acid to polycarboxylic acid chelating agent in step 1) is 14:1. The obtained water-resistant metal organic framework adsorbent material is recorded as MOF-5.

[0053] Example 6 The difference from Example 3 is only that the molar ratio of 2,5-dihydroxyterephthalic acid to polycarboxylic acid chelating agent in step 1) is 10:1. The obtained water-resistant metal organic framework adsorbent material is recorded as MOF-6.

[0054] Example 7 The difference from Example 4 is only that the magnesium salt in step 2) is replaced by 4.51 g of magnesium acetate tetrahydrate. The obtained water-resistant metal-organic framework adsorbent material is denoted as MOF-7.

[0055] Example 8 The difference from Example 4 is only that the magnesium salt in step 2) is replaced by 4.27 g of magnesium chloride hexahydrate. The obtained water-resistant metal-organic framework adsorbent material is denoted as MOF-8.

[0056] Comparative Example 1 1) 2 g of 2,5-dihydroxyterephthalic acid was dissolved in 40 mL of sodium hydroxide solution (the concentration of the sodium hydroxide solution was 1 mol / L), and stirred for 20 min; 2) 5.18 g of magnesium nitrate hexahydrate was dissolved in 40 mL of methanol, and stirred for 20 min; 3) The above two solutions were mixed (the ligand alkali solution was added dropwise into the magnesium salt alcohol solution), the dropwise time was 50 min, and the reaction was carried out at 25°C for 24 h, and then washed with methanol and water, first washed with methanol for 6 times, and then washed with a mixed solution of methanol and water with a volume ratio of 1:1 for 5 times, filtered and placed in a vacuum oven (temperature was 80°C) for drying, to obtain a water-resistant metal-organic framework adsorbent material, denoted as MOF-0.

[0057] Application Examples 2-8 and Comparative Application Example 1 MOF-1 in Application Example 1 was replaced by MOF-2, and the results were denoted as MOF-2-D, MOF-2-L (RH=30%), MOF-2-M (RH=60%), and MOF-2-H (RH=86%) respectively.

[0058] MOF-1 in Application Example 1 was replaced by MOF-3, and the results were denoted as MOF-3-D, MOF-3-L (RH=30%), MOF-3-M (RH=60%), and MOF-3-H (RH=86%) respectively.

[0059] MOF-1 in Application Example 1 was replaced by MOF-4, and the results were denoted as MOF-4-D, MOF-4-L (RH=30%), MOF-4-M (RH=60%), and MOF-4-H (RH=86%) respectively.

[0060] MOF-1 in Application Example 1 was replaced by MOF-5, and the results were denoted as MOF-5-D, MOF-5-L (RH=30%), MOF-5-M (RH=60%), and MOF-5-H (RH=86%) respectively.

[0061] MOF-1 in Application Example 1 is replaced by MOF-6, and the results are recorded as MOF-6-D, MOF-6-L (RH = 30%), MOF-6-M (RH = 60%), and MOF-6-H (RH = 86%), respectively.

[0062] MOF-1 in Application Example 1 is replaced by MOF-7, and the results are recorded as MOF-7-D, MOF-7-L (RH = 30%), MOF-7-M (RH = 60%), and MOF-7-H (RH = 86%), respectively.

[0063] MOF-1 in Application Example 1 is replaced by MOF-8, and the results are recorded as MOF-8-D, MOF-8-L (RH = 30%), MOF-8-M (RH = 60%), and MOF-8-H (RH = 86%), respectively.

[0064] MOF-1 in Application Example 1 is replaced by MOF-0, and the results are recorded as MOF-0-D, MOF-0-L (RH = 30%), MOF-0-M (RH = 60%), and MOF-0-H (RH = 86%), respectively.

[0065] The CO2 adsorption capacity and humidity change amount are shown in Table 1.

[0066] Table 1 CO2 adsorption capacity and humidity change amount of Application Examples 1-8 and Comparative Application Example 1

[0067] The CO2 adsorption capacity and humidity change amount of the adsorbent materials prepared in Examples 1-8 and Comparative Example 1 under the conditions of 41℃, normal pressure, 15CO2 / 85N2, and RH = 86% are shown in Table 3. Figure 3 .

[0068] Separation cycle performance test: The adsorbent material MOF-4 prepared in Example 4 was also tested for its cycle performance under the conditions of 41℃, normal pressure, 15CO2 / 85N2, and RH = 86%. The desorption temperature was 200℃, and the desorption time was 4h. The CO2 adsorption performance of 6 adsorption / desorption cycles is shown in Table 2.

[0069] Table 2 Cycle separation performance of MOF-4

[0070] As shown in Table 1, compared to Comparative Example 1, the water-resistant metal-organic framework material of this invention maintains a high CO2 adsorption capacity in both dry and moist flue gas, exhibits a relatively stable CO2 adsorption capacity under different humidity levels, and demonstrates a significant water-promoted CO2 adsorption effect under high humidity conditions, indicating that the material has good water resistance. Figure 3 It can be seen that MOF-4 exhibits the highest CO2 adsorption capacity under high humidity conditions, indicating that appropriate EDTA incorporation can better enhance the material's moisture resistance. Table 2 shows that the synthesized MOF-4 adsorbent material possesses good cycling stability; after six adsorption-desorption cycles, the CO2 adsorption capacity showed no significant change. In summary, the design approach adopted in this invention differs from the existing approach of maintaining adsorption performance by repelling water molecules. Instead, it utilizes introduced polar functional groups to construct dual adsorption sites for H2O and CO2, thus achieving innovation in material structure design and adsorption mechanism construction.

[0071] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, not all embodiments. People can obtain other embodiments based on the present invention without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method of preparing a water-resistant metal-organic framework material, characterized in that, The method comprises the following steps: mixing a magnesium salt, an organic ligand, an inorganic base, water and a lower alcohol, performing a co-precipitation reaction on the obtained mixed solution, and performing solid-liquid separation to obtain a water-resistant metal organic framework material; the organic ligand comprises 2,5-dihydroxyterephthalic acid and a polycarboxylic acid chelating agent, and the polycarboxylic acid chelating agent comprises one or more of ethyleneglycolbis(2-aminoethylether)tetraacetic acid, 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid and ethylenediaminetetraacetic acid.

2. The production method according to claim 1, characterized by, The molar ratio of the 2,5-dihydroxyterephthalic acid and the polycarboxylic acid chelating agent is 1:0.02-0.

1.

3. The preparation method according to claim 1, characterized in that, The magnesium salt comprises one or more of magnesium nitrate, magnesium acetate and magnesium chloride.

4. The production method according to claim 1 or 3, characterized by, The molar ratio of the magnesium salt and the organic ligand is 2-4:

1.

5. The preparation method according to claim 1, characterized in that, The inorganic base is sodium hydroxide, and the lower alcohol is methanol or ethanol.

6. The method of claim 1, wherein, The mixing of the magnesium salt, the organic ligand, the inorganic base, the water and the lower alcohol is as follows: dissolving the magnesium salt in the lower alcohol to obtain a magnesium salt alcohol solution; dissolving the organic ligand in an aqueous solution of the inorganic base to obtain a ligand base solution; and adding the ligand base solution dropwise into the magnesium salt alcohol solution.

7. The preparation method according to claim 1, characterized in that, The co-precipitation reaction is performed at a temperature of 20-35℃ for 12-36 hours.

8. The water-resistant metal-organic framework material obtainable by the process according to any one of claims 1 to 7, characterized in that The water-resistant metal organic framework material is a polycarboxylic acid chelating agent modified Mg-MOF-74.

9. Use of the water-resistant metal organic framework material of claim 8 in CO2 adsorption under high humidity conditions.

10. Use according to claim 9, characterized in that, The CO2 adsorption is selective adsorption of CO2 from a mixed gas, and the mixed gas comprises CO2, N2 and H2O.

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