Mixed ligand MOFs (Metal-Organic Frameworks) material as well as preparation method and application thereof

Abstract

The invention relates to a mixed ligand MOFs material and a preparation method and application thereof, and the preparation method comprises the following steps: weighing H2PZDC, sequentially adding NaOH and hydroxy aluminum, mixing, carrying out a primary water bath reaction, rapidly adding FA, and carrying out a secondary water bath reaction; and centrifuging the product, washing, precipitating, drying and grinding to obtain the mixed ligand MOFs material. Compared with a traditional single-step synthesis method, the method has the advantages that controllable coordination of metal nodes and double organic ligands is realized through a staged ligand introduction strategy, the proportion of the double ligands in the material can be accurately regulated and controlled, and the material has an adjustable water adsorption working interval. Compared with a single-ligand MOF material, the mixed-ligand MOF material prepared by the method disclosed by the invention has the advantages that the water adsorption performance is enhanced (under the environment humidity), and the cost can be reduced by about 40%. The material shows remarkable application advantages in the fields of air humidity regulation, industrial drying systems, moisture prevention of precise instruments and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of porous materials, and in particular to a mixed-ligand MOFs material, a preparation method thereof and an application thereof. Background Art

[0002] Metal-organic Frameworks (MOFs) are a class of porous crystalline materials formed by the self-assembly coordination of metal centers and organic ligands. Due to their high porosity, large specific surface area and abundant active sites, they show significant application potential in the fields of gas adsorption and separation, catalysis and air water harvesting. Especially in the field of air water harvesting in low-humidity environments, MOFs materials can achieve efficient water capture through the synergistic effect of physical adsorption and capillary condensation, and their performance is significantly better than traditional adsorbents such as silica gel and zeolite. However, the water adsorption isotherms of existing single-component MOFs materials often show a fixed working range, facing technical bottlenecks such as insufficient environmental adaptability and excessive desorption energy consumption in practical applications.

[0003] The prior art mainly regulates the water adsorption performance of MOFs through three strategies: (1) bimetallic doping; (2) mixed-ligand co-assembly and (3) ligand exchange. The first two methods are to adjust the structure of the synthesized MOF by adding two metal sources or organic ligands. For example, by introducing heterogeneous metal nodes (such as Al / Fe bimetal), synthesizing aluminum fumarate / MIL-88A bimetallic MOFs, adjusting the pore channel electronic structure, hydrophilic-hydrophobic properties and their water adsorption performance; by replacing some of the original ligands after synthesis (such as replacing terephthalic acid in MIL-101(Cr) with ferrocene dicarboxylic acid), a photothermal response group can be introduced to improve the inherent water absorption and photothermal water release ability of MIL-101(Cr). Mixed-ligand co-assembly strategy: Using two or more organic ligands to synergistically construct metal-organic frameworks, and realizing the customization of adsorption sites through functional group combination, has become the current mainstream MOFs performance regulation scheme. Compared with single-ligand MOFs, mixed-ligand MOFs can regulate the water adsorption working range of single MOF materials in air water harvesting, and optimize the adsorption and condensation ability of the materials for water vapor.

[0004] Existing mixed-ligand MOFs mostly use isostructural network ligand combinations (such as trimesic acid and isophthalic acid) to ensure lattice compatibility. However, such isostructural functional ligands need to be custom-synthesized and are expensive (such as fluorine-containing ligands costing up to $500 / g), severely restricting large-scale applications. Therefore, developing low-cost and easily accessible heterogeneous ligand combinations to precisely regulate the hydrophilic-hydrophobic balance while ensuring the structural stability of MOFs has become the key technical challenge to break through the commercialization bottleneck of air water harvesting materials. Summary of the Invention

[0005] The object of the present invention is to provide a mixed-ligand MOFs material, a preparation method thereof and an application, so as to overcome the defects existing in the prior art.

[0006] In the present invention, by screening industrial-grade inexpensive ligands with specific structures, a mixed-ligand MOFs with gradient adsorption characteristics is innovatively constructed, effectively broadening its humidity response window and reducing the material cost by more than 40%, providing a core material solution for large-scale air water collection systems.

[0007] The object of the present invention can be achieved by the following technical solutions:

[0008] The technical solution of the present invention is to provide a preparation method of a mixed-ligand MOFs material, including the following steps:

[0009] ① Weigh H 2 PZDC, successively add NaOH and hydroxyaluminum for mixing, carry out a first water bath reaction, and then quickly add FA to carry out a second water bath reaction;

[0010] ② Centrifuge the product obtained in step ①, wash the precipitate and dry it, and grind it to obtain the mixed-ligand MOFs material.

[0011] In the present invention, the hydroxyaluminum is a polymeric hydroxyaluminum salt, referring to patent CN113461964A.

[0012] In the present invention, the polymeric hydroxyaluminum salt refers to an inorganic polymer formed by metal aluminum ions, hydroxyl groups and water molecules through coordination bonds and covalent bonds, which is a general term for the hydrolysis products of metal aluminum ions in an aqueous solution of metal aluminum ions after reaching hydrolysis equilibrium.

[0013] In some specific embodiments, in step ①, the molar ratio of H 2 PZDC, FA, Al 3+ in hydroxyaluminum, and NaOH ranges from (1 to 9):(1 to 9):2:1.

[0014] In some specific embodiments, in step ①, first dissolve H 2 PZDC and NaOH completely in water at 70 °C.

[0015] In some specific embodiments, in step ①, the temperature of the first water bath reaction is 70 to 90 °C, and the time of the first water bath reaction is 5 to 30 min.

[0016] In some specific embodiments, in step ①, the temperature of the second water bath reaction is 80 to 100 °C, and the time of the first water bath reaction is 1 to 1.5 h.

[0017] In some specific embodiments, in step ②, the washing is as follows: the precipitate after centrifugation is washed at least twice with deionized water and methanol respectively.

[0018] In some specific embodiments, in step ②, the drying temperature is 80 - 120 °C.

[0019] The second technical solution of the present invention is to provide a mixed - ligand MOFs material, which is obtained based on the preparation method described in the above - mentioned first technical solution.

[0020] The present invention uses a step - by - step synthesis method to prepare a mixed - ligand MOFs material, which can better achieve the accurate regulation of the ratio of the two ligands H 2 PZDC (3,5 - pyrazoledicarboxylic acid) and FA (fumaric acid) in the structure of the mixed - ligand MOFs material, effectively regulate the water absorption working range of the mixed - ligand MOFs material to meet the water adsorption requirements in different humidity environments, and further reduce the synthesis cost of the mixed - ligand MOFs material.

[0021] The third technical solution of the present invention is to provide an application of the mixed - ligand MOFs material described in the above - mentioned second technical solution, and the mixed - ligand MOFs material is used to prepare water adsorption products for different humidity environments.

[0022] In some specific embodiments, the humidity range in the humidity environment is RH10% - 80%.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The present invention uses a step - by - step synthesis method by adding ligands successively to prepare a mixed - ligand MOFs material. Compared with the traditional one - step synthesis method, the present invention realizes the controllable coordination of metal nodes and double organic ligands, effectively avoiding the problem that in the process of synthesizing a mixed - ligand MOF material by regulating the synthesis of existing mixed ligands, there is a certain gap between the ratio of the two ligands in the synthesized mixed - ligand MOFs material and the initially added ratio due to the certain competitive relationship between the ligands.

[0025] (2) The present invention can accurately regulate the ratio of the double ligands H 2 PZDC and FA, thereby effectively adjusting the water absorption range of the mixed - ligand MOFs material, and at the same time providing new possibilities for regulating price costs.

[0026] (3) Compared with single - ligand MOF materials, the mixed - ligand MOF material prepared by the present invention has enhanced water adsorption performance (under environmental humidity) and the cost can be reduced by about 40%. This material shows significant application advantages in fields such as air humidity regulation, industrial drying systems, and moisture protection of precision instruments. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 1H NMR (c, d) and XRD patterns (a, b) of the mixed ligand MOFs products synthesized in the examples and comparative examples.

[0028] Figure 2 Water vapor adsorption curves of the stepwise synthesized AlFum / MOF-303 mixed ligand material and comparison of adsorption amounts at various humidities.

[0029] Figure 3 Schematic flow chart for preparing the mixed ligand MOFs material of the present invention. Detailed implementation manners

[0030] As Figure 3 shown in the schematic flow chart for preparing the mixed ligand MOFs material, the present invention uses different molar masses of H 2 PZDC, adds 10 mL of deionized water, then adds 0.1 g of NaOH, stirs at 70 °C until completely dissolved, then adds 0.91 g of hydroxyaluminum, reacts in a 90 °C water bath for 5 minutes, and then quickly adds different molar masses of FA and continues to react in a 90 °C water bath for 1 h. The obtained product is centrifuged, the supernatant is removed, washed twice with deionized water and methanol respectively to remove unreacted aluminum salts and ligands, and finally dried in an 80 °C oven and ground to obtain a powdery product.

[0031] The hydroxyaluminum used in the following examples is polyhydroxyaluminum chloride, referring to patent CN113461964A.

[0032] Polyhydroxyaluminum chloride refers to an inorganic polymer formed by metal aluminum ions, hydroxyl groups and water molecules through coordination bonds and covalent bonds, and is a general term for the hydrolysis products of metal aluminum ions in an aqueous solution of metal aluminum ions after reaching hydrolysis equilibrium.

[0033] A preparation method of polyhydroxyaluminum chloride can be referred to the public literature: Study on the preparation of high-purity polyaluminum chloride from aluminum foil and its properties [J]. Chemistry & Bioengineering, 2009, 26(01): 18-21.

[0034] The basicity of the prepared polyhydroxyaluminum chloride is 73.2%, and the mass fraction of aluminum oxide (Al 2 O 3 ) is 29.8 ± 0.08 / %.

[0035] The stepwise synthesis method adopted by the present invention can better achieve the accurate regulation of the ligand ratio in the product structure, effectively regulate the water absorption working range of the material to meet the water adsorption requirements of different humidity environments, and further reduce the synthesis cost of the material.

[0036] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and gives detailed implementation manners and specific operation processes, but the protection scope of the present invention is not limited to the following embodiments.

[0037] In the following examples and comparative examples, unless otherwise specified, the raw materials or treatment techniques are all conventional commercially available raw material products or conventional treatment techniques in the art.

[0038] Example 1:

[0039] This example provides a method for stepwise synthesis of the mixed ligand AlFum / MOF-303, which includes the following steps:

[0040] Weigh 1 mmol of H 2 PZDC, add 10 mL of deionized water, then add 0.1 g of NaOH, and stir at 70 °C until completely dissolved. Then add 0.91 g of aluminum hydroxide, react in a 90 °C water bath for 5 minutes, then quickly add 4 mmol of FA, and then continue to react in a 90 °C water bath for 1 h. Centrifuge the obtained product, remove the supernatant, wash it twice with deionized water and methanol respectively to remove unreacted aluminum salts and ligands, and finally dry it in an 80 °C oven and grind it to obtain a powdery product, named FP82.

[0041] As can be seen from Figure 1 a, only the characteristic diffraction peaks of AlFum are observed in the XRD results of FP82, indicating that the product obtained under this synthesis condition is mainly AlFum. As can be seen from Figure 2 a, the water adsorption working range of FP82 is between the relative pressure P / P 0 i.e., the humidity RH is between 0.2 and 0.4.

[0042] Example 2:

[0043] This example provides a method for stepwise synthesis of the mixed ligand AlFum / MOF-303, which includes the following steps:

[0044] Weigh 2 mmol of H 2 PZDC, add 10 mL of deionized water, then add 0.1 g of NaOH, and stir at 70 °C until completely dissolved. Then add 0.91 g of aluminum hydroxide, react in a 90 °C water bath for 5 minutes, then quickly add 3 mmol of FA, and then continue to react in a 90 °C water bath for 1 h. Centrifuge the obtained product, remove the supernatant, wash it twice with deionized water and methanol respectively to remove unreacted aluminum salts and ligands, and finally dry it in an 80 °C oven and grind it to obtain a powdery product, named FP64.

[0045] As can be seen from Figure 1As can be seen from a, in the XRD results of FP64, the characteristic diffraction peaks of both AlFum and MOF-303 can be observed simultaneously, but the former is the main one, indicating that the product obtained under this synthesis condition is mainly AlFum. From Figure 2 As can be seen from a, the water adsorption working range of FP64 is at a relative pressure P / P 0 That is, between a humidity RH of 0.2 - 0.4.

[0046] Example 3:

[0047] This example provides a method for stepwise synthesis of the mixed ligand AlFum / MOF-303, including the following steps:

[0048] Weigh 2.5 mmol of H 2 PZDC, add 10 mL of deionized water, then add 0.1 g of NaOH, and stir at 70 °C until completely dissolved. Then add 0.91 g of aluminum hydroxide, react in a 90 °C water bath for 5 minutes, then quickly add 2.5 mmol of FA, and then continue to react in a 90 °C water bath for 1 h. Centrifuge the obtained product, remove the supernatant, wash it twice with deionized water and methanol respectively to remove unreacted aluminum salts and ligands, and finally dry it in an 80 °C oven and grind it to obtain a powdery product, named FP55.

[0049] From Figure 1 As can be seen from a, in the XRD results of FP55, the characteristic diffraction peaks of both AlFum and MOF-303 can be observed, indicating that the product obtained under this synthesis condition is mainly the mixed ligand material of AlFum / MOF-303. From Figure 2 As can be seen from a, the water adsorption working range of FP55 is at a relative pressure P / P 0 That is, between a humidity RH of 0.1 - 0.4.

[0050] Example 4:

[0051] This example provides a method for stepwise synthesis of the mixed ligand AlFum / MOF-303, including the following steps:

[0052] Weigh 3 mmol of H 2 PZDC, add 10 mL of deionized water, then add 0.1 g of NaOH, and stir at 70 °C until completely dissolved. Then add 0.91 g of aluminum hydroxide, react in a 90 °C water bath for 5 minutes, then quickly add 2 mmol of FA, and then continue to react in a 90 °C water bath for 1 h. Centrifuge the obtained product, remove the supernatant, wash it twice with deionized water and methanol respectively to remove unreacted aluminum salts and ligands, and finally dry it in an 80 °C oven and grind it to obtain a powdery product, named FP46.

[0053] FromFigure 1 As can be seen from a, the characteristic diffraction peaks of both AlFum and MOF-303 can be observed in the XRD results of FP46, indicating that the product obtained under this synthesis condition is mainly the mixed-ligand material of AlFum / MOF-303. From Figure 2 As can be seen from a, the water adsorption working range of FP46 is at a relative pressure of P / P 0 That is, between a humidity of RH 0.1 - 0.4.

[0054] Example 5:

[0055] This example provides a method for stepwise synthesizing the mixed-ligand AlFum / MOF-303, which includes the following steps:

[0056] Weigh 4 mmol of H 2 PZDC, add 10 mL of deionized water, then add 0.1 g of NaOH, and stir at 70 °C until completely dissolved. Then add 0.91 g of aluminum hydroxide, react in a 90 °C water bath for 5 minutes, then quickly add 1 mmol of FA, and then continue to react in a 90 °C water bath for 1 h. Centrifuge the obtained product, remove the supernatant, wash it twice with deionized water and methanol respectively to remove unreacted aluminum salts and ligands, and finally dry it in an 80 °C oven and grind it to obtain a powdery product, named FP28.

[0057] From Figure 1 As can be seen from a, only the characteristic diffraction peaks of MOF-303 are observed in the XRD results of FP28, indicating that the product obtained under this synthesis condition is mainly MOF-303. From Figure 2 As can be seen from a, the water adsorption working range of FP28 is at a relative pressure of P / P 0 That is, between a humidity of RH 0.05 - 0.2.

[0058] Comparative Example 1:

[0059] This comparative example uses a one-pot method to synthesize the mixed-ligand AlFum / MOF-303, which includes the following steps:

[0060] Weigh 1 mmol of H 2 PZDC and 4 mmol of FA, add 10 mL of deionized water, and stir at 70 °C until completely dissolved. Then add 0.91 g of aluminum hydroxide, react in a 90 °C water bath for 1 h. Centrifuge the obtained product, remove the supernatant, wash it twice with deionized water and methanol respectively to remove unreacted aluminum salts and ligands, and finally dry it in an 80 °C oven and grind it to obtain a powdery product, named FP82-HCA.

[0061] From Figure 1As can be seen from Fig. b, only the characteristic peaks of AlFum were observed for the product FP82-HCA, and the characteristic peaks shifted to a certain extent, indicating that the introduction of the second ligand during the synthesis process had a certain impact on the structure of the material.

[0062] As can be seen from Figure 1 Fig. a, only the characteristic diffraction peaks of AlFum were observed in the XRD results of FP82-HCA, indicating that the product obtained under this synthesis condition was mainly AlFum.

[0063] Comparative Example 2:

[0064] In this comparative example, a one-pot method was used to synthesize the mixed-ligand AlFum / MOF-303, which included the following steps:

[0065] Weigh 2 mmol of H 2 PZDC and 3 mmol of FA, add 10 mL of deionized water, and stir at 70 °C until completely dissolved. Then add 0.91 g of aluminum hydroxide, and react in a 90 °C water bath for 1 h. Centrifuge the obtained product, remove the supernatant, wash it twice with deionized water and methanol respectively to remove the unreacted aluminum salts and ligands, and finally dry it in an 80 °C oven and grind it to obtain a powdery product, named FP64-HCA.

[0066] As can be seen from Figure 1 Fig. b, only the characteristic diffraction peaks of AlFum were observed in the XRD results of FP64-HCA, indicating that the product obtained under this synthesis condition was mainly AlFum.

[0067] Comparative Example 3:

[0068] In this comparative example, a one-pot method was used to synthesize the mixed-ligand AlFum / MOF-303, which included the following steps:

[0069] Weigh 2.5 mmol of H 2 PZDC and 2.5 mmol of FA, add 10 mL of deionized water, and stir at 70 °C until completely dissolved. Then add 0.91 g of aluminum hydroxide, and react in a 90 °C water bath for 1 h. Centrifuge the obtained product, remove the supernatant, wash it twice with deionized water and methanol respectively to remove the unreacted aluminum salts and ligands, and finally dry it in an 80 °C oven and grind it to obtain a powdery product, named FP55-HCA.

[0070] As can be seen from Figure 1 Fig. b, the characteristic diffraction peaks of both AlFum and MOF-303 could be observed in the XRD results of FP55-HCA. Judging from the relative intensity of the diffraction peaks, the product obtained under this synthesis condition was still mainly AlFum.

[0071] Comparative Example 4:

[0072] In this comparative example, a one-pot method for synthesizing the mixed ligand AlFum / MOF-303 was adopted, which included the following steps:

[0073] Weigh 3 mmol of H 2 PZDC and 2 mmol of FA, add 10 mL of deionized water, stir at 70 °C until completely dissolved, then add 0.91 g of aluminum hydroxide, and react in a 90 °C water bath for 1 h. Centrifuge the obtained product, remove the supernatant, wash it twice with deionized water and methanol respectively to remove unreacted aluminum salts and ligands, and finally dry it in an 80 °C oven and grind it to obtain a powdery product, named FP46-HCA.

[0074] As can be seen from Figure 1 b, in the XRD results of FP46-HCA, the characteristic diffraction peaks of both AlFum and MOF-303 can be observed simultaneously, indicating that the product obtained under this synthesis condition is mainly the mixed ligand material of AlFum / MOF-303.

[0075] Comparative Example 5:

[0076] In this comparative example, a one-pot method for synthesizing the mixed ligand AlFum / MOF-303 was adopted, which included the following steps:

[0077] Weigh 4 mmol of H 2 PZDC and 1 mmol of FA, add 10 mL of deionized water, stir at 70 °C until completely dissolved, then add 0.91 g of aluminum hydroxide, and react in a 90 °C water bath for 1 h. Centrifuge the obtained product, remove the supernatant, wash it twice with deionized water and methanol respectively to remove unreacted aluminum salts and ligands, and finally dry it in an 80 °C oven and grind it to obtain a powdery product, named FP28-HCA.

[0078] As can be seen from Figure 1 b, in the XRD results of FP28-HCA, only the characteristic diffraction peaks of MOF-303 are observed, indicating that the product obtained under this synthesis condition is mainly MOF-303.

[0079] The above results show that: In the present invention, by introducing different ligands H 2PZDC (3,5-pyrazoledicarboxylic acid) and FA (fumaric acid) effectively circumvent the technical bottleneck of the synchronous competition of dual ligands for metal nodes. As in Examples 2-4, the stepwise method can obtain the AlFum / MOF-303 mixed ligand material (XRD double characteristic peaks of FP55 and FP46); while in Comparative Examples 2-4, only Comparative Example 4 can obtain the AlFum / MOF-303 mixed ligand material under the same ratio, and Comparative Examples 2-3 are all the main phase of AlFum. This indicates that there is an obvious competition phenomenon in the synthesis process of the mixed ligand. The ability of FA to coordinate with Al 3+ is significantly stronger than that of H 2 PZDC. Therefore, in the stepwise method, H 2 PZDC preferentially coordinates with the hydroxyaluminum precursor to form an aluminum-oxygen cluster in the first stage, creating thermodynamic conditions for the directional coordination of FA in the second stage. Compared with the one-pot synthesis method in the comparative examples, the stepwise method is more conducive to obtaining the mixed ligand MOF material.

[0080] By liquid 1 H NMR, the ligand ratios in the materials obtained by the two synthesis methods were quantitatively analyzed ( Figure 1 c-d), further revealing the advantages of the stepwise method in controlling the mixed ligand ratio: In Example 3 (FP55), the deviation between the actual ligand and the theoretical value (1:1) of the mixed ligand material synthesized by the stepwise method is about 5%. In Comparative Example 3 (FP55-HCA), although the theoretical feeding ratio of H 2 PZDC to FA is 1:1, the NMR integral results show that the actual ligand molar ratio is 17:83 (H 2 PZDC:FA), with a deviation of 66%. This is because the strong coordination competitiveness of FA causes it to preferentially combine with Al 3+ , resulting in a large amount of H 2 PZDC not participating in coordination and being eluted. The correlation analysis of XRD and NMR data shows that the reaction strategy of the stepwise method of the present invention effectively reduces the coordination competition and is more conducive to the formation of the mixed ligand MOF material.

[0081] The stepwise synthesis method of the present invention can effectively regulate the mixed ligand ratio, realizing the directional design and cost optimization of the water adsorption working range. By adjusting the feeding ratio of the two ligands, the water adsorption working range of the material can be continuously translated between the MOF-303 type (P / P 0 = 0.05 - 0.2) and the AlFum type (P / P 0 = 0.2 - 0.3) ( Figure 2 a). For example, the working range of the FP55 mixed ligand material is extended to P / P 0= 0.1 - 0.4, and its RH80 adsorption capacity is increased by 8 - 28% compared with the single-ligand materials (Alfum and MOF-303). In addition, in the low humidity range (RH10 - 30), this method reduces the proportion of the high-valence ligand H 2 PZDC (the unit price is 150 - 200 times that of FA), and significantly reduces the material cost on the premise of ensuring the adsorption performance. When the proportion of H 2 PZDC decreases from 100% (MOF-303) to 60% (FP46), the raw material cost is reduced by about 40%, and the water adsorption capacity of FP46 at RH20 still maintains more than 85% of the benchmark value (MOF-303). In the high humidity range (RH40 - 80), the water adsorption capacity of the mixed-ligand material F46 is significantly higher than that of MOF-303( Figure 2 e - f). This "proportion-performance-cost" linear regulation mechanism provides a theoretical model for customized material design, and can optimize material parameters for specific scenarios such as desert water extraction and industrial dehumidification, with both technological breakthrough and commercial feasibility.

[0082] The above description of the embodiments is to enable those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative efforts. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention should be within the protection scope of the present invention.

Claims

1. A method for preparing mixed ligand MOFs, characterized in that: The steps include: ① Weigh H2PZDC, add NaOH and hydroxyaluminum in sequence, mix, conduct a water bath reaction, then add FA, conduct a second water bath reaction; ② Centrifuge the product obtained in step ①, wash the precipitate and dry it, and grind it to obtain a mixed ligand MOFs material.

2. The preparation method according to claim 1, characterized in that: In step ①, the H2PZDC, FA, Al in hydroxyaluminum 3+ , and the molar ratio range of NaOH is (1~9):(1~9):2:

1.

3. The preparation method according to claim 1, characterized in that: In step ①, H2PZDC and NaOH are completely dissolved in water at 70°C.

4. The preparation method according to claim 1, characterized in that: In step ①, the temperature of a water bath reaction is 70-90° C., and the time of a water bath reaction is 5-30 min.

5. The preparation method according to claim 1, characterized in that: In step ①, the temperature of the secondary water bath reaction is 80-100° C., and the time of the secondary water bath reaction is 1-1.5 h.

6. The preparation method according to claim 1, characterized in that: In step ②, the washing is: washing the precipitate after centrifugation with deionized water and methanol at least twice respectively.

7. The preparation method according to claim 1, characterized in that: In step ②, the drying temperature is 80-120°C.

8. A mixed ligand MOFs material, characterized in that: Obtained based on the preparation method according to any one of claims 1 to 7.

9. An application of the mixed ligand MOFs material as claimed in claim 8, characterized in that: The mixed ligand MOFs material is used to prepare water adsorption products for different humidity environments.

10. The use according to claim 9, characterized in that: The humidity in the humidity environment ranges from RH10% to 80%.

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