1. A preparation method of a heteropoly acid modified metal organic framework compound is characterized by comprising the following steps:

s1, converting MOF-NH₂Dispersing in water to prepare a suspension, then adding heteropoly acid into the suspension to mix uniformly, and drying water to obtain uniformly dispersed MOF/heteropoly acid powder;

s2, mixing the powder at 100-130%^oAnd C, heating to 200-300 ℃, sintering for 3-6 hours, and cooling to obtain the heteropoly acid modified metal organic framework compound.

2. The method of claim 1, wherein: heteropolyacids with MOF-NH₂The mass ratio of (A) to (B) is 3: 1-9: 1.

3. The method of claim 1, wherein: and water used in the S1 is deionized water, and ultrasonic waves are used for mixing when the suspension is prepared in a dispersing manner, and the treatment is carried out for 1-5 hours.

4. The method of claim 1, wherein: adding heteropoly acid into S1, and stirring for over 24 h; the temperature for drying the moisture is 60-80 ℃, and the drying time is 24-48 h.

5. The method of claim 1, wherein: the heating pretreatment time in S2 is 12-16 h; the pretreatment temperature is 100-130 ℃; heating is carried out at a heating rate of 5-10 ℃/min, and the temperature is heated to 200-300 ℃.

6. The method of claim 1, wherein: and (S2) washing the heteropoly acid modified metal organic framework compound with water, and removing unreacted heteropoly acid to obtain a pure heteropoly acid modified metal organic framework compound.

7. The production method according to any one of claims 1 to 6, characterized in that: the MOF-NH₂Is MIL-53-NH₂，MIL-101-NH₂，UiO-66-NH₂，UiO-67-NH₂Or UiO-68-NH; the heteropoly acid is a heteropoly acid with a Keggin structure.

8. The application of the heteropoly acid modified metal organic framework compound obtained by the preparation method of any one of claims 1 to 7 in proton exchange membranes.

9. Use according to claim 8, characterized in that: adding the heteropoly acid modified metal organic framework compound into sulfonated polyether ether ketone for mixing, then adding the mixture into N, N-dimethylacetamide, heating to remove the solvent after uniformly mixing, and drying to obtain the composite proton exchange membrane.

10. The application of the heteropoly acid modified metal organic framework compound obtained by the preparation method of any one of claims 1 to 7 in a proton exchange membrane in the field of hydrogen production by water electrolysis.

Background

With the gradual reduction of the consumption of fossil energy, the demand of people on novel energy such as hydrogen energy is more urgent. Hydrogen energy is a safe, reliable and clean energy source. The hydrogen production by electrolyzing water by using renewable energy is an important technology in the field of hydrogen energy. As a core component of the electrolytic cell, the proton exchange membrane plays a role in separating the cathode and the anode and transferring protons in the electrolytic cell. The rate at which proton exchange membranes conduct protons, i.e., proton conductivity, is a key parameter affecting the performance of the electrolyzer. Most proton exchange membranes are affected by low proton conductivity, which limits the performance of the electrolyzer. Therefore, the research focus of proton exchange membranes is focused on improving the proton conductivity. One of the methods for improving the proton conductivity of the proton exchange membrane is to prepare an organic-inorganic nano composite membrane. Heteropolyacids are a class of polyoxometallates with high proton conductivity, and are of interest to researchers due to their characteristics of stable structure, low cost, and the like. However, its high solubility in water greatly limits its application in proton exchange membranes. In general, researchers will fix heteropoly acids on insoluble supports by hydrogen bonding or electrostatic interaction, etc., but the weak interaction between the two inevitably causes the loss of heteropoly acids. The metal organic framework is a porous material formed by combining a metal central atom and an organic ligand through a coordination bond, and is greatly concerned due to the advantages of easy modification, stable structure, high specific surface area and the like. The mode of combining heteropoly acid and metal organic framework by covalent bond is an effective method for improving the stability of heteropoly acid compound, but the preparation method of the material is still very rare. The traditional mode of combining the two by means of weak interaction forces such as electrostatic force and the like not only limits the loading capacity of the substrate to the heteropoly acid, but also inevitably leads to the loss of the heteropoly acid due to the higher solubility of the heteropoly acid in water.

In conclusion, the modification technology of the metal organic framework capable of meeting the use requirement of the proton exchange membrane is not only the research focus in the field, but also has very wide application prospect.

Disclosure of Invention

The invention provides a preparation method and application of a heteropoly acid modified metal organic framework compound.

The technical scheme of the invention is that the preparation method of the heteropoly acid modified metal organic framework compound comprises the following steps:

s1, converting MOF-NH₂Dispersing in water to prepare a suspension, then adding heteropoly acid into the suspension to mix uniformly, and drying water to obtain uniformly dispersed MOF/heteropoly acid powder;

s2, heating the powder at 100-130 ℃ for pretreatment, heating to 200-300 ℃, sintering for 3-6 hours, and cooling to obtain the heteropoly acid modified metal organic framework compound.

Further, heteropoly acids with MOF-NH₂In a mass ratio of 3:1 to 9: 1.

Further, water used in S1 is deionized water, and ultrasonic waves are used for mixing when the suspension is prepared in a dispersing mode, and the treatment lasts for 1-5 hours.

Further, adding heteropoly acid into S1, and stirring for over 24 hours; the temperature for drying the moisture is 60-80 ℃, and the drying time is 24-48 h.

Further, the heating pretreatment time in S2 is 12-16 h; the pretreatment temperature is 100-130 ℃; heating is carried out at a heating rate of 5-10 ℃/min, and the temperature is heated to 200-300 ℃.

Further, the heteropoly acid-modified metal-organic framework composite obtained in S2 is washed with water to remove unreacted heteropoly acid. Obtaining the pure heteropoly acid modified metal organic framework compound.

Further, the heteropoly acid is a heteropoly acid with a Keggin structure. The MOF-NH₂Is MIL-53-NH₂，MIL-101-NH₂，UiO-66-NH₂，UiO-67-NH₂Or UiO-68-NH;

the invention also relates to application of the heteropoly acid modified metal organic framework compound obtained by the preparation method in a proton exchange membrane.

And further adding the heteropoly acid modified metal organic framework compound into sulfonated polyether ether ketone for mixing, then adding the mixture into N, N-dimethylacetamide, heating to remove the solvent after uniformly mixing, and drying to obtain the composite proton exchange membrane. Preferably, the heteropoly acid modified metal organic framework composite powder is added into sulfonated polyether ether ketone (SPEEK), so that the powder accounts for 2-8 wt% of the total mass. Uniformly dispersing the mixture in N, N-dimethylacetamide (DMAc) to ensure that the mass ratio of the solid mixture to the DMAc is 1: 10-1: 20, respectively. And after ultrasonic treatment and stirring for 4-8 hours respectively, pouring the dispersion liquid into a square glass vessel, vacuumizing for 10-20 minutes, placing in an oven at 80-90 ℃ for 24-48 hours to remove the solvent, and then placing in the vacuum oven at 80-90 ℃ for 24-48 hours to obtain the composite proton exchange membrane. The proton conductivity of the composite proton exchange membrane is measured under low humidity (30% RH-70% RH), and the proton conductivity of the composite proton exchange membrane is more than 60 times of that of pure SPEEK under low humidity. The obtained sulfonated polyether ether ketone has the Ion Exchange Capacity (IEC) of 1.52meq/g and the proton conductivity of 0.041S/cm.

The invention also relates to application of the heteropoly acid modified metal organic framework compound obtained by the preparation method in a proton exchange membrane in the field of hydrogen production by water electrolysis.

The invention has the following beneficial effects:

the invention firstly prepares MOF-NH₂And the mixture and heteropoly acid are uniformly dispersed in deionized water to obtain stable suspension, and then the MOF/heteropoly acid mixture with uniform distribution is obtained by evaporation. And then, the MOF is connected with the heteropoly acid through a covalent bond in a sintering mode. The composite nano particles prepared by the invention have good stability. No loss of heteropoly acid is observed after soaking in water for more than 30 days. And the strong proton conduction capability of the heteropoly acid is utilized to provide a long-range ordered proton transmission path for the proton exchange membrane after being compounded with the MOF with a highly regular structure. The heteropolyacid is combined with amino functional groups on the MOF ligand through covalent bonds, so that the amount of the MOF supported heteropolyacid is greatly increased, and the heteropolyacid and MOF-NH can be maximally combined₂The mass ratio is improved to 9:1, much higher than bonding by direct compression or electrostatic force. Is MOF-NH₂The proton conductor is provided, and the problem of heteropolyacid loss is solved, so that the proton conductivity of the proton exchange membrane is improved.

After the composite material nano particles prepared by the invention are added into the SPEEK matrix, the conductivity of the composite proton exchange membrane in water is higher than that of pure SPEEK by more than 50%.

Drawings

FIG. 1 shows MIL-101-NH obtained in example 1₂Scanning electron microscope picture of phosphotungstic acid powder material.

FIG. 2 shows MIL-101-NH obtained in example 1₂X-ray diffraction pattern of phosphotungstic acid powder material.

Detailed Description

Embodiments of the present invention will be described in detail below with reference to examples, but those skilled in the art will appreciate that the following examples are only illustrative of the present invention and should not be construed as limiting the scope of the present invention.

Example 1:

1g of MIL-101-NH₂Performing ultrasonic treatment in deionized water for 1h to obtain a suspension, and then adding 5g of phosphotungstic acid into the evenly dispersed MIL-101-NH₂Stirring the suspension for more than 24 h. Then placing the suspension in an oven, and standing at 60 deg.C for 24 hr to completely remove water to obtain uniformly dispersed MIL-101-NH₂Phosphotungstic acid powder. Continuing to put the powder inIn the oven, the plate was first left at 100 ℃ for 12 hours and then heated to 275 ℃ at a rate of 5 ℃/min and held for 5 hours. When the muffle furnace is returned to room temperature, crude UiO-66-NH is collected₂Phosphotungstic acid powder.

Washing the obtained powder with water for several times to remove unreacted phosphotungstic acid to obtain pure MIL-101-NH₂Phosphotungstic acid powder. 0.018g of powder was added to Sulfonated Polyetheretherketone (SPEEK) to ensure a total mass of 0.3 g. Uniformly dispersing the mixture in N, N-dimethylacetamide (DMAc) to ensure that the mass ratio of the solid mixture to the DMAc is 1: 10. and after 8 hours of ultrasonic treatment and stirring, pouring the dispersion into a square glass dish, vacuumizing for 10 minutes, placing in an oven, standing at 80 ℃ for 28 hours to remove the solvent, and then placing in the vacuum oven at 80 ℃ for 48 hours to obtain the composite proton exchange membrane.

MIL-101-NH₂And MIL-101-NH₂The scanning electron microscope picture of the phosphotungstic acid material is shown in figure 1, the X-ray diffraction image is shown in figure 2, and the shape of the sintered powder and pure MIL-101-NH can be seen from figure 1₂The variation is small, indicating that the sintering process does not destroy the basic morphology of the MOF. As can be seen from FIG. 2, MIL-101-NH₂The crystal structure of phosphotungstic acid powder is matched with pure MIL-101-NH₂The change was large and the overall diffraction pattern was closer to that of heteropoly acid, but was also shifted compared to heteropoly acid, indicating that a new species had been formed. The powder diffraction pattern after sintering was found to be substantially identical to ammonium phosphotungstate (ICDD 50-0305), indicating that phosphotungstic acid and amino functional groups have been covalently bonded to each other.

Example 2:

1g of UiO-66-NH₂Ultrasonic treatment is carried out for 1h in deionized water, and then 5g of silicotungstic acid is added into the evenly dispersed UiO-66-NH₂Stirring the suspension for more than 24 h. Then placing the suspension in an oven, and standing at 60 deg.C for 24 hr to completely remove water to obtain uniformly dispersed UiO-66-NH₂Silicotungstic acid powder. The powder was further placed in an oven at 100 ℃ for 12 hours and then heated to 275 ℃ at a rate of 5 ℃/min and held for 5 hours. When the muffle furnace is returned to the room temperature, collectingTo crude UiO-66-NH₂Silicotungstic acid powder. Washing the obtained powder with water for several times to remove unreacted silicotungstic acid to obtain pure UiO-66-NH₂Silicotungstic acid powder.

0.018g of powder was added to Sulfonated Polyetheretherketone (SPEEK) to ensure a total mass of 0.3 g. Uniformly dispersing the mixture in N, N-dimethylacetamide (DMAc) to ensure that the mass ratio of the solid mixture to the DMAc is 1: 10. and after 8 hours of ultrasonic treatment and stirring, pouring the dispersion into a square glass dish, vacuumizing for 10 minutes, placing in an oven, standing at 80 ℃ for 28 hours to remove the solvent, and then placing in the vacuum oven at 80 ℃ for 48 hours to obtain the composite proton exchange membrane.

Example 3:

1g of UiO-66-NH₂Ultrasonic treatment is carried out for 1h in deionized water, and then 9g of phosphotungstic acid is added into the evenly dispersed UiO-66-NH₂Stirring the suspension for more than 24 h. Then placing the suspension in an oven, and standing at 60 deg.C for 24 hr to completely remove water to obtain uniformly dispersed UiO-66-NH₂Phosphotungstic acid powder. The powder was further placed in an oven at 100 ℃ for 12 hours and then heated to 275 ℃ at a rate of 5 ℃/min and held for 5 hours. When the muffle furnace is returned to room temperature, crude UiO-66-NH is collected₂Phosphotungstic acid powder. Washing the obtained powder with water for several times to remove unreacted phosphotungstic acid to obtain pure UiO-66-NH₂Phosphotungstic acid powder.

0.018g of powder was added to Sulfonated Polyetheretherketone (SPEEK) to ensure a total mass of 0.3 g. Uniformly dispersing the mixture in N, N-dimethylacetamide (DMAc) to ensure that the mass ratio of the solid mixture to the DMAc is 1: 10. and after 8 hours of ultrasonic treatment and stirring, pouring the dispersion into a square glass dish, vacuumizing for 10 minutes, placing in an oven, standing at 80 ℃ for 28 hours to remove the solvent, and then placing in the vacuum oven at 80 ℃ for 48 hours to obtain the composite proton exchange membrane.

Comparative example 1:

taking 0.3g of sulfonated polyether ether ketone (SPEEK), uniformly dispersing in N, N-dimethylacetamide (DMAc), and ensuring that the mass ratio of the SPEEK to the DMAc is 1: 10. and after 8 hours of ultrasonic treatment and stirring, pouring the dispersion into a square glass dish, vacuumizing for 10 minutes, placing in an oven, standing at 80 ℃ for 28 hours to remove the solvent, and then placing in the vacuum oven at 80 ℃ for 48 hours to obtain the composite proton exchange membrane.

Comparative example 2

1g of UiO-66-NH₂And (4) carrying out ultrasonic treatment in deionized water for 1h, and stirring for more than 24 h. The suspension was then placed in an oven at 60 ℃ for 24 hours to completely remove the water. The powder was further placed in an oven at 100 ℃ for 12 hours and then heated to 275 ℃ at a rate of 5 ℃/min and held for 5 hours. When the muffle furnace is returned to room temperature, the crude MOF powder is collected. The obtained powder was washed with water several times. 0.018g of powder was added to Sulfonated Polyetheretherketone (SPEEK) to ensure a total mass of 0.3 g. Uniformly dispersing the mixture in N, N-dimethylacetamide (DMAc) to ensure that the mass ratio of the solid mixture to the DMAc is 1: 10. and after 8 hours of ultrasonic treatment and stirring, pouring the dispersion into a square glass dish, vacuumizing for 10 minutes, placing in an oven, standing at 80 ℃ for 28 hours to remove the solvent, and then placing in the vacuum oven at 80 ℃ for 48 hours to obtain the composite proton exchange membrane.

Comparative example 3

5g of phosphotungstic acid is added into the evenly dispersed UiO-66-NH₂Stirring the suspension for more than 24 h. Then placing the solution in a drying oven, placing the solution at 60 ℃ for 24 hours to completely remove water, continuously placing the powder in the drying oven, firstly placing the powder at 100 ℃ for 12 hours, and directly collecting UiO-66-NH without sintering after the water is completely dried₂Phosphotungstic acid powder.

0.018g of powder was added to Sulfonated Polyetheretherketone (SPEEK) to ensure a total mass of 0.3 g. Uniformly dispersing the mixture in N, N-dimethylacetamide (DMAc) to ensure that the mass ratio of the solid mixture to the DMAc is 1: 10. and after 8 hours of ultrasonic treatment and stirring, pouring the dispersion into a square glass dish, vacuumizing for 10 minutes, placing in an oven, standing at 80 ℃ for 28 hours to remove the solvent, and then placing in the vacuum oven at 80 ℃ for 48 hours to obtain the composite proton exchange membrane.

Comparative example 4

1g of MIL-101-NH₂Performing ultrasonic treatment in deionized water for 1h, and then adding 5g of phosphotungstic acid into the evenly dispersed MIL-101-NH₂Stirring the suspension for more than 24 h. Then placing the suspension in an oven, and standing at 60 deg.C for 24 hr to completely remove water to obtain uniformly dispersed MIL-101-NH₂Phosphotungstic acid powder. The powder was kept in the oven and, without pretreatment, was heated directly to 275 ℃ at a rate of 5 ℃/min and held for 5 hours. After the muffle furnace returned to room temperature, crude MIL-101-NH was collected₂Phosphotungstic acid powder. Washing the obtained powder with water for several times to remove unreacted phosphotungstic acid to obtain pure MIL-101-NH₂Phosphotungstic acid powder.

0.018g of powder was added to Sulfonated Polyetheretherketone (SPEEK) to ensure a total mass of 0.3 g. Uniformly dispersing the mixture in N, N-dimethylacetamide (DMAc) to ensure that the mass ratio of the solid mixture to the DMAc is 1: 10. and after 8 hours of ultrasonic treatment and stirring, pouring the dispersion into a square glass dish, vacuumizing for 10 minutes, placing in an oven, standing at 80 ℃ for 28 hours to remove the solvent, and then placing in the vacuum oven at 80 ℃ for 48 hours to obtain the composite proton exchange membrane.

The composite proton exchange membranes obtained in the above examples 1-3 and comparative examples 1-4 were tested, and the specific data are shown in table 1 below.

TABLE 1 comparison of the properties of the examples with those of the comparative examples

From table 1, it can be seen that the modification method has a good effect on different MOFs having amino groups and different heteropolyacids having Keggin structures, and compared with common electrostatic action, the formation of covalent bonds enables the MOF/phosphotungstic acid to have high loading rate and stability. The pretreatment process before powder sintering has the function of activating the MOF, and compared with the MOF/phosphotungstic acid which is not subjected to pretreatment, the conductivity of the pretreated powder is higher.