Preparation method and application of NH2-UiO-66 encapsulated sulfamic acid

Abstract

The invention discloses a preparation method of NH2-UiO-66 encapsulated sulfamic acid and a proton conduction performance of the NH2-UiO-66 encapsulated sulfamic acid. The preparation method of the NH2-UiO-66 encapsulated sulfamic acid comprises the following steps: performing solvothermal reaction on zirconium tetrachloride and 2-aminoterephthalic acid, firstly synthesizing NH2-UiO-66, and then encapsulating the sulfamic acid into pores of the NH2-UiO-66 material by adopting a dynamic continuous concentration method. The preparation method provided by the invention is simple in preparation process, short in packaging time, obviously improved in proton conductivity of the material and high in cycling stability. More importantly, the interaction between the Lewis basic group on the MOF and the guest molecule is utilized, a significant number of two-property carriers are successfully introduced by a mild and rapid method, and the test performance can be kept for a long time.

Description

Technical Field

[0001] The invention belongs to the field of preparation of proton exchange membrane materials and relates to a preparation method of NH2-UiO-66 encapsulated aminosulfonic acid and its proton conduction performance. Background Art

[0002] Proton exchange membrane fuel cells (PEMFCs) are considered to be one of the most promising power sources for future electric vehicles due to their high conversion efficiency, significant power density, clean and sustainable development. As one of the core components of proton exchange membrane fuel cells (PEMFCs), proton exchange membranes play a vital role in proton transport and blocking the cathode and anode electrolytes. In recent years, metal organic frameworks (MOFs) materials have attracted extensive attention from researchers due to their high porosity, high specific surface area, structural adjustability and modifiability. Effective proton transfer within MOF materials can be achieved by encapsulating or grafting such as acids, bases, histamine, triazoles, imidazoles or ionic liquids, increasing proton carriers (acids / bases) in the pores of MOF materials to construct continuous hydrogen bond pathways or increase the proton concentration in the pores. Among the many MOFs materials, NH2-UiO-66 is a very representative amino MOF. It is derived from UiO-66 and is based on the connection between Zr-O cluster secondary building units (SBUs) and 2-aminoterephthalic acid. It has good chemical stability, thermal stability and ultra-high water stability. The different connection methods between the bridging ligand and the metal construct two triangular windows of 0.6nm and 1.0nm. The amino groups in the pores show weak alkalinity or electron donor properties, which means that NH2-UiO-66 has the ability to encapsulate acidic molecules or amphiphilic molecules to enhance proton transport.

[0003] With ultra-high proton conductivity (σ≥10 -1 S·cm-1), strongly acidic molecules such as H2SO4 and H3PO4 are confined in them to serve as proton sources and proton carriers. However, strongly acidic molecules will attack metal-ligand bonds / inorganic clusters, and the original structure of MOF is destroyed. Only a very small number of strong acid-resistant MOFs or covalent organic frameworks (COFs) meet this condition. Although the proton conductivity exhibited by confining weakly acidic guest molecules or functionalized groups in the pores of MOF is generally low, the MOF framework is not easily destroyed. Therefore, it is necessary to encapsulate as many guest molecules that are conducive to proton transport as possible, provided that the stability of the MOF material permits, in order to achieve the purpose of enhancing proton conductivity. Aminosulfonic acid (H2NSO3H, HSA) molecules with moderately strong acidity (pKa=1) are dipoles, usually expressed as + H3NSO3 - It also contains a proton donor (NH 3+ ) and proton acceptors (SO3- ), which is able to form an extensive hydrogen-bonding network with a water molecule or another aminosulfonic acid molecule for efficient proton transfer.

[0004] Encapsulating proton carriers by immersion is a simple and effective strategy to enhance the proton conductivity of MOF materials. Currently, MOF materials with excellent proton conductivity are mainly encapsulated with non-volatile acids with strong acidity. This method is only suitable for a small amount of MOF materials with high stability, and there are problems such as long immersion time and easy leakage of the guest. In order to solve this problem, exploring new methods of encapsulating guest molecules and new proton carriers plays an important role. Summary of the invention

[0005] The purpose of the present invention is to provide a preparation method of NH2-UiO-66 encapsulated aminosulfonic acid and a proton conductive material thereof. The NH2-UiO-66 material after encapsulating aminosulfonic acid has strong stability, high encapsulation efficiency, high proton conductivity and good cycle stability.

[0006] The invention provides a preparation method of NH2-UiO-66 encapsulated aminosulfonic acid and a proton conductive material thereof, wherein the composition and mass percentage content thereof are: 16-36% of NH2-UiO-66 and 64-84% of aminosulfonic acid.

[0007] The present invention provides a method for preparing NH2-UiO-66 encapsulated aminosulfonic acid, comprising the following steps: (1) Dissolving the zirconium salt and the ligand in a solvent, adding acetic acid and performing a solvothermal reaction to obtain NH2-UiO-66; (2) Dissolve aminosulfonic acid in anhydrous methanol, add NH2-UiO-66, stir at 40-50°C for 1 h to 3 h, and then continue stirring at room temperature for 18 h to 24 h. After filtering, activate the obtained product to obtain NH2-UiO-66 encapsulated aminosulfonic acid.

[0008] The zirconium salt in step (1) is selected from any one of zirconium tetrachloride, basic zirconium tetrachloride and zirconium nitrate. The organic ligand in the present invention is 2-aminoterephthalic acid.

[0009] In step (1), the solvent thermal reaction temperature is 120°C, the reaction time is 24-72 h, and vacuum drying is performed at 120°C for 24 h.

[0010] The mass percentage content in step (2) is: NH2-UiO-66 16~36%, aminosulfonic acid 64~84%.

[0011] The activation process in step (2) is carried out under vacuum conditions.

[0012] The activation temperature is 70-90℃ and the activation time is 10-15h Another technical solution of the present invention is to provide a proton conductive material, including NH2-UiO-66 encapsulated aminosulfonic acid prepared by the preparation method.

[0013] The present invention provides a method for testing the proton conductivity performance of NH2-UiO-66 encapsulated aminosulfonic acid, comprising the following steps: (1) Place the NH2-UiO-66 samples before and after soaking in aminosulfonic acid in a vacuum drying oven at 80°C for 12 h. Use a medicine spoon to take 5-10 mg of the dry sample and pour it into the tablet pressing chamber. Pressurize it to 0.38 Gpa and stabilize it for more than 20 seconds. After reducing the pressure, take out the sample and press it into tablets.

[0014] (2) Place the sheet on a glass slide, take a gold wire and cover the top of it, then fix the two ends with insulating glue, then apply conductive silver glue on the top of the sheet, let it stand for half a minute, wait for the conductive silver glue to dry completely, then turn the sheet over and repeat the operation. Wrap the ends of the two gold wires covering the top and bottom of the sheet with the conductive columns of the square test bench respectively, then place it in a constant temperature and humidity chamber, and connect it to the square test bench through a wire for AC impedance testing.

[0015] The beneficial effects of the present invention are: 1. The present invention provides an NH2-UiO-66 encapsulated aminosulfonic acid, which is encapsulated by a continuous dynamic concentration encapsulation method. Compared with conventional immersion encapsulation, the preparation process of this method is short, the synthesis conditions are mild, the encapsulation amount is high, and the proton conductivity of the material is significantly improved, and the cycle stability is good.

[0016] 2. The present invention provides an NH2-UiO-66 that encapsulates aminosulfonic acid, and the guest is not easy to leak. Compared with the MOFs material that encapsulates low-boiling point and highly acidic molecules, the retention time of the proton source guest is extended, and high conductivity can be maintained for a long time. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a PXRD comparison diagram of NH2-UiO-66 and simulation in Example 4.

[0018] Figure 2 This is a PXRD comparison diagram of NH2-UiO-66 in Example 4 after being immersed in aminosulfonic acid solutions of different concentrations.

[0019] Figure 3 This is a PXRD comparison chart of different heating times when NH2-UiO-66 is immersed in aminosulfonic acid solution in Example 4.

[0020] Figure 4 This is a physical comparison diagram of NH2-UiO-66 in Example 4 before and after being soaked in aminosulfonic acid solution.

[0021] Figure 5 This is an infrared comparison image of NH2-UiO-66 in Example 4 before and after being immersed in aminosulfonic acid solution.

[0022] Figure 6 This is a comparison chart of saturated N2 adsorption and desorption before and after NH2-UiO-66 is soaked in aminosulfonic acid solution in Example 4.

[0023] Figure 7 This is a schematic diagram of the pore distribution of NH2-UiO-66 before and after soaking in aminosulfonic acid solution in Example 4.

[0024] Figure 8 This is the proton conductivity diagram of NH2-UiO-66 in Example 4.

[0025] Fig. 9 This is the proton conductivity diagram of NH2-UiO-66 after soaking in aminosulfonic acid solution in Example 4.

[0026] Fig.10 This is the Arrhenius fitting diagram of NH2-UiO-66 after soaking in aminosulfonic acid solution in Example 4.

[0027] Fig.11 This is the 7-day cyclic conductivity diagram of NH2-UiO-66 after soaking in aminosulfonic acid solution in Example 4.

[0028] Fig.12 This is the Nyquist plot of NH2-UiO-66 in Example 4 measured after being immersed in aminosulfonic acid solution for 210 days. DETAILED DESCRIPTION

[0029] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings.

[0030] Example 1 (1) Dissolve ZrCl4 (0.5592 g, 2.4 mmol) and H2BDC-NH2 (0.4348 g, 2.4 mmol) in 60 ml DMF, slowly add 7.2 ml acetic acid, put the mixed solution into a polytetrafluoroethylene bottle, and keep it in an oven at 120°C for 72 h. After natural cooling, centrifuge, wash the sample with 5 ml pure water and 5 ml anhydrous methanol, and vacuum dry it at 120°C for 24 h to obtain the activated NH2-UiO-66 sample.

[0031] (2) Dissolve aminosulfonic acid (0.0291 g) in 20 ml of anhydrous methanol to prepare a 0.3 mol / L solution, add 100 mg of activated NH2-UiO-66, stir at 45°C for 2 h, turn off the heat, and continue stirring for 18 h to evaporate the anhydrous methanol. After encapsulation, filter it, wash it three times with 3 ml of ethanol, and activate it at 80°C under vacuum for 12 h to obtain aminosulfonic acid / NH2-UiO-66.

[0032] Example 2 (1) Dissolve ZrCl4 (0.5592 g, 2.4 mmol) and H2BDC-NH2 (0.4348 g, 2.4 mmol) in 60 ml DMF, slowly add 7.2 ml acetic acid, put the mixed solution into a polytetrafluoroethylene bottle, and keep it in an oven at 120°C for 48 h. After natural cooling, centrifuge, wash the sample with 5 ml pure water and 5 ml anhydrous methanol, and vacuum dry it at 120°C for 24 h to obtain the activated NH2-UiO-66 sample.

[0033] (2) Dissolve aminosulfonic acid (0.0291 g) in 20 ml of anhydrous methanol to prepare a 0.3 mol / L solution, add 100 mg of activated NH2-UiO-66, stir at 45°C for 2 h, turn off the heat, and continue stirring for 18 h to evaporate the anhydrous methanol. After encapsulation, filter it, wash it three times with 3 ml of ethanol, and activate it at 80°C under vacuum for 12 h to obtain aminosulfonic acid / NH2-UiO-66.

[0034] Example 3 (1) Dissolve ZrCl4 (0.2796 g, 1.2 mmol) and H2BDC-NH2 (0.2174 g, 1.2 mmol) in 30 ml DMF, slowly add 3.6 ml acetic acid, put the mixed solution into a polytetrafluoroethylene bottle, and keep it in an oven at 120°C for 24 h. After natural cooling, centrifuge, wash the sample with 5 ml pure water and 5 ml anhydrous methanol, and vacuum dry it at 120°C for 24 h to obtain the activated NH2-UiO-66 sample.

[0035] (2) Dissolve aminosulfonic acid (0.0291 g) in 20 ml of anhydrous methanol to prepare a 0.3 mol / L solution, add 100 mg of activated NH2-UiO-66, stir at 45°C for 1 h, 2 h, or 3 h, then turn off the heat and continue stirring for 18 h to evaporate the anhydrous methanol. After encapsulation, filter it, wash it three times with 3 ml of ethanol, and activate it at 80°C under vacuum for 12 h to obtain aminosulfonic acid / NH2-UiO-66.

[0036] Example 4 (1) Dissolve ZrCl4 (0.2796 g, 1.2 mmol) and H2BDC-NH2 (0.2174 g, 1.2 mmol) in 30 ml DMF, slowly add 3.6 ml acetic acid, put the mixed solution into a polytetrafluoroethylene bottle, and keep it in an oven at 120°C for 24 h. After natural cooling, centrifuge, wash the sample with 5 ml pure water and 5 ml anhydrous methanol, and vacuum dry it at 120°C for 24 h to obtain the activated NH2-UiO-66 sample.

[0037] (2) Dissolve aminosulfonic acid (0.0097 g, 0.0194 g, 0.0291 g, 0.0388 g, 0.0485 g) in 20 ml of anhydrous methanol to prepare 0.1 M, 0.2 M, 0.3 M, 0.4 M, and 0.5 M solutions in turn, add 100 mg of activated NH2-UiO-66, stir at 45 °C for 2 h, turn off the heat, and continue stirring for 18 h to evaporate the anhydrous methanol. After encapsulation, filter it, wash it three times with 3 ml of ethanol, and activate it at 80 °C for 12 h under vacuum to obtain aminosulfonic acid / NH2-UiO-66.

[0038] Performance testing: 1. Framework structure analysis The activated NH2-UiO-66 sample prepared by step (1) in Example 4 was continuously scanned using graphite monochromatized copper target X-rays (λ=1.5406 Å) in the range of 5° to 50° at a step length of 0.02° and a speed of 5° / min. The scanned results were compared with the single crystal simulated powder pattern on the Mercury software. Comparison of the two spectra shows that the peak position of the activated NH2-UiO-66 sample prepared by step (1) in Example 4 is completely consistent with that of the single crystal simulated powder diffraction pattern, and there are no unnecessary diffraction peaks, indicating that the activated NH2-UiO-66 sample synthesized in this step is pure NH2-UiO-66. The powder diffraction comparison pattern is shown in FIG. Figure 1 .

[0039] 2. Optimal encapsulation concentration analysis According to the specific steps in Example 4, aminosulfonic acid was encapsulated in aminosulfonic acid solutions of different concentrations. The diffraction spectrum obtained after testing was Figure 2 As can be seen from the figure, with the increase of the concentration of aminosulfonic acid, the crystallinity of activated NH2-UiO-66 gradually decreases, and the diffraction peaks appear when the concentration of aminosulfonic acid is greater than 0.3 mol / L. In order to maintain the stability and purity of the activated NH2-UiO-66 sample during the encapsulation of aminosulfonic acid, 0.3 mol / L was selected as the optimal encapsulation concentration.

[0040] 3. Optimal packaging time analysis According to the specific steps in Example 3, the effect of different heating times was investigated in a 0.3 mol / L aminosulfonic acid solution. The diffraction spectrum obtained after the test was Figure 3 It can be seen from the figure that as the heating time increases, mixed peaks appear in the powder diffraction spectrum, so it is appropriate to choose a heating time of 2h.

[0041] 4. Infrared analysis The two samples (such as Figure 4 ) was dried at 80℃ for 1 day and infrared test was performed. The infrared spectrum is as follows Figure 5 As shown, at 1002 cm -1 and 1064 cm -1 The stretching vibration peak of O=S=O is at 1215 cm -1 A new peak appears, which can be attributed to the vibration of CS bond. 3300 cm -1 The double peak absorption of primary amine is converted into the single peak absorption of secondary amine and blue-shifted to 3147 cm -1 It can be inferred that aminosulfonic acid successfully combines with the primary amine groups on the activated NH2-UiO-66 to form new chemical bonds and extensive hydrogen bonds.

[0042] 5.BET surface area analysis The specific surface area of ​​the sample is tested based on the adsorption and desorption experiment of saturated nitrogen. Before doing the gas adsorption experiment, the two samples of NH2-UiO-66 in Example 4 before and after soaking in 0.3 mol / L aminosulfonic acid solution are deeply activated: 100 mg of the sample is weighed and solvent exchanged with 10 ml of anhydrous methanol at room temperature for three days, and the solvent is replaced every 8 hours (10 ml×12 times), followed by centrifugation to remove the supernatant, and the obtained sample is placed in a 120°C vacuum drying oven for activation for 24 h, and finally activated again at 120°C on a BET test instrument for 6 h to completely remove the anhydrous methanol molecules in the sample. The fully activated sample is tested for its adsorption of saturated nitrogen at 77 K. The saturated nitrogen adsorption and desorption results are shown in the figure. Figure 6 , 7 As shown in the figure, at 77 K and 1 standard atmosphere, the saturated nitrogen adsorption capacity of the two samples of NH2-UiO-66 before and after soaking in aminosulfonic acid solution is 210.75 cm 3 / g and 301.61 cm 3 / g, and the surface areas of the two samples were evaluated by computer fitting of the adsorption and desorption results to be 642.23 m 2 / g and 899.54 m 2 / g. The total pore volumes of the two samples were 0.3277 cm 3 / g and 0.4690 cm3 / g. In contrast, the total amount of N2 adsorption, specific surface area, and pore volume of the sample after NH2-UiO-66 was soaked in aminosulfonic acid solution were significantly reduced, confirming that a large number of aminosulfonic acid molecules existed in the pores of the NH2-UiO-66 sample.

[0043] 6. AC impedance test analysis The level of sample impedance and proton conductivity are related to the amino groups on the framework, the aminosulfonic acid in the pores, the water molecules and the hydrogen bonds generated by the three. 20 mg of NH2-UiO-66 in Example 4, before and after soaking in 0.3 mol / L aminosulfonic acid solution, were placed in a micro tablet press for tableting. The sample tablets were then placed in an XK-CTS80Z constant temperature and humidity instrument and impedance analyzed using Solartron S1-1260 and S1-1296 EIS impedance analyzers. The analysis results are shown in the figure. Figure 8 , 9 As shown in Figure 2, the conductivity of the activated NH2-UiO-66 sample at 70 °C and 98% RH is 3.24×10 -5 The conductivity of the sample encapsulated with aminosulfonic acid in NH2-UiO-66 reached 0.172 S / cm at 90°C and 98% RH, which is 10 times that of the activated NH2-UiO-66 sample. 5 times. The activation energy obtained by least squares fitting is 0.38 eV, as shown in Fig.10 As shown. It is confirmed that a large number of aminosulfonic acid molecules and water molecules in the pores form a long-range ordered hydrogen bond network, which plays a very important role in the transport of protons. The samples of NH2-UiO-66 encapsulated with aminosulfonic acid in Example 1 and Example 2 were tested under the same conditions, and the conductivity was 0.168 S / cm and 0.170 S / cm, respectively.

[0044] 7. Stability analysis A good material should not only have outstanding performance, but also good stability and cyclability to ensure its long-term use and storage. The sample of NH2-UiO-66 soaked in 0.3 mol / L aminosulfonic acid solution in Example 4 was placed in a 98% and 90°C environment for continuous testing for 7 days. The test results are as follows: Fig.11 As shown, its conductivity only decreased by 2%, which is almost negligible. Then, the pressed sheet after the test was subjected to XRD diffraction, and it was found that the diffraction spectrum was basically consistent with that before the test, proving that the main frame was not damaged and the cycle performance was excellent. Subsequently, the NH2-UiO-66 in Experimental Example 4, which was placed in an open system at room temperature for 210 days, was immersed in 0.3 mol / L aminosulfonic acid solution and the sample was subjected to AC impedance test again. The test results are shown in Fig.12It was found that even though the sample was left open for 210 days, the proton conductivity could still reach 0.160 S / cm, proving that the material has excellent stability.

[0045] In summary, after NH2-UiO-66 is encapsulated with aminosulfonic acid by this method, it has very high proton conductivity, excellent cycle performance and stability. In addition, the preparation process is simple and easy to operate. The encapsulation time of aminosulfonic acid is short and the conductivity is significantly improved. It has great potential in the preparation of new proton exchange membranes.

[0046] The embodiments are preferred implementations of the present invention, but the present invention is not limited to the above-mentioned implementations. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essential content of the present invention belong to the protection scope of the present invention.

Claims

1. A method for preparing NH2-UiO-66 encapsulated aminosulfonic acid, characterized in that: The following steps are involved: (1) Dissolving the zirconium salt and the ligand in a solvent, adding acetic acid and performing a solvothermal reaction to obtain NH2-UiO-66; (2) Dissolve aminosulfonic acid in anhydrous methanol, add NH2-UiO-66, stir at 40-50°C for 1 h to 3 h, and then continue stirring at room temperature for 18 h to 24 h. After filtering, activate the obtained product to obtain NH2-UiO-66 encapsulated aminosulfonic acid.

2. The method for preparing NH2-UiO-66 encapsulated aminosulfonic acid according to claim 1, characterized in that: The zirconium salt described in step (1) is selected from any one of zirconium tetrachloride, basic zirconium tetrachloride and zirconium nitrate.

3. The method for preparing NH2-UiO-66 encapsulated aminosulfonic acid according to claim 1, characterized in that: In step (1), the solvent thermal reaction temperature is 120-140°C, the reaction time is 24-72 h, and vacuum drying is performed at 120°C for 12-24 h.

4. The method for preparing NH2-UiO-66 encapsulated aminosulfonic acid according to claim 1, characterized in that: The mass percentage content in step (2) is: NH2-UiO-66 16~36%, aminosulfonic acid 64~84%.

5. The method for preparing NH2-UiO-66 encapsulated aminosulfonic acid according to claim 1, characterized in that: The activation process in step (2) is carried out under vacuum conditions.

6. The method for preparing NH2-UiO-66 encapsulated aminosulfonic acid according to claim 1, characterized in that: In step (2), the activation temperature is 70-90°C and the activation time is 10-15h.

7. A proton conductive material, characterized in that: The method comprises preparing NH2-UiO-66 encapsulated aminosulfonic acid by the preparation method described in any one of claims 1 to 6.

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