Preparation method and application of hydrogen-bonded organic framework material with high proton conductivity constructed by carboxylic acid-amino guanidine

Abstract

This invention belongs to the field of fuel cell technology, specifically relating to a method for preparing and applying a hydrogen-bonded organic framework material with high proton conductivity constructed from carboxylic acid-aminoguanidine. The chemical formula of this organic framework material is [(CN4H7)(C 10 [O8H5], this organic framework material belongs to the triclinic crystal system. P Space group 1, cell parameters: a =7.9901(4)Å, b =9.6412(3)Å, c =9.6724(4)Å, α =96.322(3)°, β =113.876(4)°, c =93.633(3)°. The hydrogen-bonded organic framework material constructed by carboxylic acid-aminoguanidine and the composite film prepared therefrom have high proton conductivity and are highly promising proton conduction materials.

Description

Technical Field

[0001] This invention belongs to the field of fuel cell technology, specifically relating to a method for preparing and applying a hydrogen-bonded organic framework material with high proton conductivity constructed from carboxylic acid-aminoguanidine. Background Technology

[0002] Fuel cells directly convert renewable chemical energy into electrical energy, possessing high theoretical efficiency and power density, making them a very promising environmentally friendly power generation device. Current fuel cells mainly include: proton exchange membrane fuel cells (PEMFCs); phosphoric acid fuel cells (PAFCs); solid oxide fuel cells (SOFCs); and alkaline fuel cells (AFCs). Among them, proton exchange membrane fuel cells are considered the most promising candidate to replace traditional energy sources due to their outstanding advantages such as green efficiency, ultra-low emissions, high power density, and fast start-up speed. In a typical H2 / O2 proton exchange membrane fuel cell device, H2 is oxidized at the anode to produce H2O. + Protons are converted into electrons, which are then transferred to the cathode via an external circuit, generating an electric current. Simultaneously, hydrogen protons pass through a proton exchange membrane (PEM) to the cathode, converting chemical energy into electrical energy. Since the only byproduct is water, this conversion system is considered a clean and sustainable technology. In a proton exchange membrane fuel cell, the proton exchange membrane, as the core component of the entire system, needs to meet several conditions: high proton conductivity (>10). -2 Scm -1 It possesses good chemical and thermal stability; superior gas resistance; good membrane (thin film) mechanical properties and processing performance; good compatibility with other components such as bipolar plates and electrode materials; low cost; and ease of mass production. The first application in fuel cells was in 1960 with Nafion, a perfluorosulfonated polymer produced by DuPont. It exhibits excellent proton conductivity (10...). -1 -10 -2 S cm -1 However, its temperature range is limited; its proton conductivity is compromised above 80°C or below -5°C. Furthermore, its high cost and complex synthesis process further restrict its applications. On the other hand, as an amorphous material, it is difficult to investigate its proton conduction behavior and proton transport pathways. Therefore, developing novel, low-cost, and high-performance crystalline proton-conducting materials has become a hot research topic in the field of chemistry.

[0003] Hydrogen-bonded organic frameworks (HOFs), constructed from small organic monomers through self-assembly via hydrogen bonding, π-π stacking, and van der Waals interactions, are a novel type of crystalline porous material. Their large specific surface area, high porosity, low density, and high adsorption capacity have made them a promising branch of porous organic frameworks (POPs). Compared to metal-organic frameworks (MOFs) formed by connecting inorganic metals and organic units, HOFs avoid metal nodes, exhibiting lower density and larger theoretical void volume. Furthermore, compared to COFs, the weak interactions involved in HOF assembly facilitate the formation of larger single crystals. Detailed structural information of the compounds can be obtained through single-crystal X-ray diffraction analysis, enabling more kinetic analyses. The preparation of hydrogen-bonded organic frameworks is very simple, avoiding cumbersome synthetic procedures. Currently, only two reports exist of using hydrogen-bonded organic frameworks to modify Nafion films to improve their proton conductivity. Summary of the Invention

[0004] This invention proposes a method for preparing a hydrogen-bonded organic framework material with high proton conductivity constructed from carboxylic acid-aminoguanidine, and its application. The hydrogen-bonded organic framework material constructed from carboxylic acid-aminoguanidine and the composite film prepared therefrom exhibit high proton conductivity and are highly promising proton-conducting materials.

[0005] The present invention specifically adopts the following technical solution:

[0006] The hydrogen-bonded organic framework material constructed from carboxylic acid-aminoguanidine of the present invention has the chemical formula [(CN4H7)(C 10 [O8H5], this organic framework material belongs to the triclinic crystal system, space group P-1, and its unit cell parameters are: α=96.322(3)°, β=113.876(4)°, γ=93.633(3)°.

[0007] The aforementioned organic framework material has an asymmetric unit, which contains an aminoguanidine cation CN4H7. + and a carboxylic acid anion C 10 O8H5 - .

[0008] Each carboxylic acid anion C 10 O8H5 - All of them contain an intramolecular hydrogen bond of O3-H3···O2, and are connected to the neighboring carboxylic acid anion C through various intermolecular hydrogen bonds of OH···O and NH···O respectively. 10 O8H5 - and aminoguanidine cation CN4H7 +The layers connect to form a two-dimensional layered structure. The layers further extend into a three-dimensional hydrogen-bonded framework structure through intermolecular hydrogen bonds of NH...O. The carboxylic acid anion C in the two-dimensional layers... 10 O8H5 - The benzene rings also exhibit π-π stacking interactions, with the centroid spacing between the rings being [missing information]. and

[0009] The above-mentioned organic framework material [(CN4H7)(C 10 The preparation method of [O8H5] includes:

[0010] 1,2,4,5-Benzenetetracarboxylic acid and aminoguanidine hydrochloride were dissolved in methanol, and then the mixed solution was evaporated at room temperature. After filtration and drying, colorless strip-shaped crystals were obtained, which is the product. The molar ratio of 1,2,4,5-Benzenetetracarboxylic acid and aminoguanidine hydrochloride was 1:1.

[0011] This invention relates to organic framework materials [(CN4H7)(C 10 Powder proton conductivity tests were conducted on [(CN4H7)(C], and it was found that at 298 K, as the relative humidity increased from 55% to 98%, the proton conductivity of the compound [(CN4H7)(C] was increased. 10 The conductivity of O8H5)] continuously increases, from 1.44 × 10 -9 Scm -1 Up to 1.41×10 -4 S cm -1 This represents an increase of five orders of magnitude. When the relative humidity is 98% and the temperature is continuously increased to 358 K, the proton conductivity of the compound reaches 1.09 × 10⁻⁶. -2 S cm -1 It surpasses most of the previously reported metal-organic framework materials and hydrogen-bonded organic framework materials.

[0012] This invention will use compound [(CN4H7)(C 10 A sample-Nafion composite film was prepared by mixing O8H5) powder with Nafion, and proton conductivity was tested. The results showed that the composite film exhibited a proton conductivity of 2.14 × 10⁻⁶ at 298 K and 55% RH. -6 S cm -1 With increasing relative humidity, the proton conductivity reached 6.78 × 10⁻⁶ at 298 K and 98% RH. -3 S cm -1 This represents an increase of three orders of magnitude. When the temperature is raised to 358 K, the proton conductivity of the complex reaches 5.18 × 10⁻⁶. -2 S cm -1 It surpasses most of the composite membrane materials reported in the literature.

[0013] Therefore, the organic framework material of the present invention [(CN4H7)(C 10 O8H5)] and the composite membrane prepared therefrom are used to prepare proton-conducting materials.

[0014] The beneficial effects of this invention are as follows:

[0015] The [(CN4H7)(C) prepared by this invention 10 The powdered proton conductivity of the compound [O8H5] reached 1.09 × 10⁻⁶ at 358 K and 98% RH. -2 S cm -1 The proton conductivity of the composite membrane reaches 5.18 × 10⁻⁶. -2 S cm -1 The proton conductivity is higher than that of existing composite membranes based on hydrogen-bonded organic framework materials. This is mainly due to the synergistic effect of Nafion and the compound. Moreover, the compound has simple synthesis conditions and high yield, which helps to realize the large-scale commercial application of proton exchange membrane fuel cells. Attached Figure Description

[0016] Figure 1 (a) Compound [(CN4H7)(C 10 (a) the asymmetric unit of O8H5); (b) the two-dimensional layer structure of the compound; (c) the three-dimensional hydrogen bond network of the compound; (d) the topologically simplified structure of the compound.

[0017] Figure 2 Compound [(CN4H7)(C 10 XRD patterns of O8H5) under different humidity levels.

[0018] Figure 3 (a) Nyquist plots at 298 K and different relative humidities; (b) Nyquist plots at 98% RH and different temperatures; (c) ln(σT) vs 1000T -1 (d) PXRD patterns before and after proton conductivity test.

[0019] Figure 4 (a) Image of the composite membrane; (b) SEM image; (c) Infrared spectrum of the composite membrane; (d) XRD spectrum.

[0020] Figure 5 Composite membrane: (a) Nyquist plots at 298 K and different relative humidities; (b) Nyquist plots at different temperatures at 98% RH; (c) ln(σT) vs 1000T -1 curve.

[0021] Figure 6Comparison of proton conductivity of composite membrane and Nafion membrane at different temperatures. Detailed Implementation

[0022] The present invention will now be described in more detail through specific embodiments to facilitate understanding of the technical solution of the present invention, but this is not intended to limit the scope of protection of the present invention.

[0023] 1.[(CN4H7)(C 10 Synthesis method of O8H5):

[0024] 1,2,4,5-Benzenetetracarboxylic acid (0.2 mmol, 0.050 g) and aminoguanidine hydrochloride (0.2 mmol, 0.022 g) were dissolved in 4 mL of methanol. The mixture was then evaporated at room temperature, filtered, and dried to obtain colorless, strip-shaped crystals (yield: 52.3% based on 1,2,4,5-Benzenetetracarboxylic acid). Elemental analysis (%): Theoretical values: C 40.25, N 17.07, H 3.68; Found: C 40.16, N 16.98, H 3.83. Infrared spectral data (KBr, cm⁻¹) -1 ):3434(s),3352(w),3284(m),2760(w),2614(w),2508(w),1910(s),1684(w),1447(w),1275(m),1132(m),851(m),796(s),663(m),552(m). Among them: C 10 O8H6 (1,2,4,5-benzenetetracarboxylic acid), CN4H7Cl (aminoguanidine hydrochloride).

[0025] 2.[(CN4H7)(C 10 Determination of the structure of O8H5)]

[0026] A single crystal of appropriate size was selected and subjected to X-ray diffraction analysis on a ROD, Synergy Custom system, HyPix diffractometer at a test temperature of 293(2) K. GaKα rays were used. Crystal diffraction point data were collected, and the data were reduced and corrected for absorption using a direct method. The [(CN4H7)(C]0]0 diffraction pattern was analyzed using the SHELXS-2014 and SHELXL-2014 procedures. 10 The structure of compound [(CN4H7)(C] was analyzed and refined. The coordinates of non-hydrogen atoms in the structure were corrected for anisotropic temperature factors using the full matrix least squares method, and the coordinates of hydrogen atoms were obtained through difference Fourier synthesis. 10 The crystallographic data of O8H5) are shown in Table 1 below:

[0027] Table 1 Compounds [(CN4H7)(C10 Crystallographic data of O8H5)]

[0028]

[0029] 3.[(CN4H7)(C 10 Structural analysis of O8H5)]

[0030] X-ray single-crystal diffraction analysis showed that the compound [(CN4H7)(C 10 [O8H5] crystallizes in the triclinic system, space group P-1, and its asymmetric unit contains an aminoguanidine cation CN4H7. + and a carboxylic acid anion C 10 O8H5 - (like Figure 1 (as shown in a). For example... Figure 1 As shown in b, each carboxylic acid anion C 10 O8H5 - All of them contain an intramolecular hydrogen bond of O3-H3···O2, and are connected to the neighboring carboxylic acid anion C through various intermolecular hydrogen bonds of OH···O and NH···O respectively. 10 O8H5 - and aminoguanidine cation CN4H7 + The layers connect to form a two-dimensional layered structure. The layers further extend into a three-dimensional hydrogen-bonded framework structure through intermolecular hydrogen bonds of NH···O, as shown below. Figure 1 As shown in c, simultaneously, the carboxylic acid anion C in the two-dimensional layer 10 O8H5 - The benzene rings also exhibit π-π stacking interactions (along the a direction), and the centroid spacing between the rings is... and The formation of π-π stacking interactions helps to increase the stability of the three-dimensional structure of this compound.

[0031] Topological analysis of this compound [(CN4H7)(C 10 The hydrogen bond network in O8H5)], carboxylic acid anion C 10 O8H5 - and aminoguanidine cation CN4H7 + These can be viewed as 12-connection points and 8-connection points respectively. Therefore, the entire 3D skeleton simplifies to a two-node topology, with the topological notation {3}. 12 0.4 28 0.5 22 0.6 4}{3 6 0.4 20 0.5 2},like Figure 1 As shown in d.

[0032] 4. Compound [(CN4H7)(C 10 Powder proton conductivity test of O8H5)

[0033] Determination of compound [(CN4H7)(C 10 X-ray powder diffraction (PXRD) of O8H5 under a series of different humidity levels (55%, 65%, 75%, 85%, 98% RH) showed that its PXRD pattern was consistent with the theoretical value obtained by X-ray single-crystal diffraction. Figure 2 ), indicating that the compound [(CN4H7)(C 10 [O8H5] exhibits good stability under different humidity levels.

[0034] The compound [(CN4H7)(C 10 The crystals of [(CN4H5)] were ground into powder. A 10mg sample of the powder was placed on a tablet press mold with a diameter of 3mm and pressed for approximately two minutes using a pressure of 0.5MPa to obtain a disc with a thickness of 1.1mm. Conductive silver paste was uniformly coated onto the upper and lower cross-sections of the disc, and it was then fixed to the sample stage with gold wire for testing. The compound [(CN4H7)(C] 10 The AC impedance (O8H5) test was performed using a high-precision impedance-gain-phase analyzer (Solartron 1260 / 1296). The measurement frequency range was 0.01–10 MHz, the input voltage was 100 mV, the measurement temperature range was 298 K to 358 K, and the humidity range was 55% RH to 98% RH. Conductivity σ (S / cm) -1 The value is obtained by the formula σ = L / (RA), where L (cm) and A (cm) are the values ​​of RA and RA. 2 The values ​​represent the thickness and cross-sectional area of ​​the disc, respectively. R (Ω) is the resistance of the sample, obtained by simulating the impedance data in the Nyquist plot using the Zview equivalent circuit method. Activation energy (E) a Using Arrhenius's formula σT=σ o exp(-E a The value is obtained as / kT), where k is the Boltzmann constant (eV / k) and T(K) is the temperature.

[0035] like Figure 3 As shown in Figure a, at 298 K, as the relative humidity increases from 55% to 98%, the compound [(CN4H7)(C 10 The conductivity of O8H5)] continuously increases, from 1.44 × 10 -9 S cm -1 Up to 1.41×10 -4 S cm -1 This represents an increase of five orders of magnitude, indicating that humidity has a significant impact on proton conductivity testing. For example... Figure 3 As shown in b, when the relative humidity is 98% and the temperature is continuously increased to 358K, the proton conductivity of the compound reaches 1.09 × 10⁻⁶. -2 S cm -1 It surpasses most reported metal-organic framework materials and hydrogen-bonded organic framework materials, and is a proton-conducting material with great application potential.

[0036] To further investigate the proton transport mechanism, the proton conductivity under temperature changes was fitted using the Arrhenius equation, and [ln(σT)vs 1000T] was used. -1 ]Drawing ( Figure 3 c), the compound [(CN4H7)(C] was calculated to be... 10 The activation energy E of O8H5)] a The voltage was 0.57 eV, following a hybrid hopping and carrier transport mechanism. Furthermore, X-ray powder diffraction (XRD) was performed on the sample after the proton conductivity test, such as... Figure 3 As shown in d, the peak positions in the XRD pattern basically match the theoretical peak positions in the XRD pattern obtained from single-crystal data simulation, indicating that the compound [(CN4H7)(C 10 The structure of O8H5)] did not change.

[0037] 5. Preparation of composite membranes

[0038] 2 mL of 5 wt% Nafion solution was evaporated and concentrated to 1 mL at 50 °C, then 2 mL of DMF was added, and the solution was evaporated and concentrated to 1.5 mL at 60 °C. Subsequently, 0.1 g of the powdered compound [(CN4H7)(C 10 The O8H5)] was uniformly dispersed in 1.5 mL of the mixture and stirred for three hours. The mixture was then transferred to an evaporating dish with a diameter of 35 mm and placed in a vacuum drying oven at 60 °C to obtain the composite membrane. To remove impurities from the Nafion, the composite membrane was boiled in a 3 wt% H2O2 solution, then immersed in a 1 M H2SO4 solution, followed by washing with distilled water and drying at room temperature.

[0039] 6. Composite membrane proton conductivity test

[0040] Compound [(CN4H7)(C 10 The powder sample of O8H5) exhibits high proton conductivity at 358 K and 98% RH. To study its application performance, the method described in section 5 above, "Preparation of Composite Films," was used to prepare a sample-Nafion composite film (e.g., O8H5) Figure 4 (as shown in a). The composite membrane was tested by scanning electron microscopy (SEM), as shown in a). Figure 4As shown in figure b, the surface of the composite film is smooth, indicating that the compound [(CN4H7)(C 10 O8H5)] was uniformly dispersed in Nafion solution. Additionally, potassium bromide was used in tableting at 400–4000 cm⁻¹. -1 The infrared spectra of the compounds and composite films were measured within the specified range using a Bruker VERTEX-70 Fourier transform infrared spectrometer. Figure 4 As shown in Figure c, the composite membrane displays the infrared characteristic peaks of both the compound and Nafion, indicating successful preparation of the composite membrane. Similarly, comparing the XRD spectra of the compound and the composite membrane (e.g., ...) Figure 4 As shown in d), 2θ=17° represents the characteristic peak of Nafion, which further illustrates the successful preparation of the composite membrane.

[0041] This embodiment also performed a proton conductivity test on the composite film. For example... Figure 5 As shown in figure a, the composite membrane exhibits a proton conductivity of 2.14 × 10⁻⁶ under conditions of 298 K and 55% RH. -6 S cm -1 With increasing relative humidity, the proton conductivity reached 6.78 × 10⁻⁶ at 298 K and 98% RH. -3 S cm -1 This represents an increase of three orders of magnitude. For example... Figure 5 As shown in b, when the temperature rises to 358 K, the proton conductivity of the composite reaches 5.18 × 10⁻⁶. -2 S cm -1 It surpasses the Nafion membrane ( Figure 6 This includes HOF composite membrane materials reported in most literatures. The activation energy E of the composite membrane was obtained by fitting the Arrhenius equation. a 0.34 eV (e.g.) Figure 5 As shown in c), it follows a jump mechanism.

[0042] With the increasing severity of energy and environmental issues, the development of green, environmentally friendly, and efficient fuel cell technology is crucial. Proton exchange membrane fuel cells (PEMFCs) have attracted widespread attention from researchers due to their ultra-low emissions, high power density, and fast start-up speed. As the core component of PEMFCs, a primary characteristic of the proton exchange membrane is its high proton conductivity. The compound [(CN4H7)(C 10 The proton conductivity of the powder [O8H5] reached 1.09 × 10⁻⁶ under conditions of 358 K and 98% RH. -2 S cm -1 The proton conductivity of the composite membrane reaches 5.18 × 10⁻⁶. -2 S cm -1This compound surpasses most currently reported materials and is comparable to commercially available Nafion. Moreover, the compound has simple synthesis conditions, making it a highly promising proton-conducting material.

[0043] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Therefore, all equivalent changes or modifications made to the structure, features and principles described in the claims of the present invention should be included within the scope of the present invention.

Claims

1. A hydrogen-bonded organic framework material constructed from carboxylic acid-aminoguanidine, characterized in that, The chemical formula of this organic framework material is [(CN4H7)(C 10 [O8H5], this organic framework material belongs to the triclinic crystal system. P Space group 1, cell parameters: a =7.9901(4)Å, b =9.6412(3)Å, c =9.6724(4)Å, α =96.322(3) °, β =113.876(4) °, γ =93.633(3)°; The method for preparing the organic framework material includes: 1,2,4,5-Benzenetetracarboxylic acid and aminoguanidine hydrochloride were dissolved in methanol, and then the mixed solution was evaporated at room temperature. After filtration and drying, colorless strip-shaped crystals were obtained.

2. A composite membrane, characterized in that, The composite membrane is prepared from the organic framework material described in claim 1.

3. The method for preparing the composite membrane according to claim 2, characterized in that, The Nafion solution was concentrated and then mixed with DMF, concentrated again, and then [(CN4H7)(C 10 The O8H5)] powder is uniformly dispersed in the concentrated mixture, then coated on a plate to form a film structure, and dried at 60°C to obtain the composite film.

4. The preparation method according to claim 3, characterized in that, The [(CN4H7)(C] 10 The mass ratio of Nafion in the O8H5)] powder and 5wt% Nafion solution is 0.1:0.0875, and 2mL of DMF is added for every 2mL of Nafion solution sample.

5. The preparation method according to claim 3, characterized in that, The composite membrane was boiled in a 3 wt% H2O2 solution, then immersed in a 1 M H2SO4 solution, washed with distilled water, and dried at room temperature.

6. The application of the organic framework material according to claim 1 in the preparation of proton-conducting materials.

7. The application of the composite membrane according to claim 2 in the preparation of proton-conducting materials.

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