A redox-active metal-organic framework material, its preparation method and its application

Abstract

This invention discloses a redox-active metal-organic framework material, its preparation method, and its applications. The metal-organic framework material is prepared by a solvothermal method using bis(triphenylaminetetracarboxylic acid) and inorganic manganese compounds as raw materials, N,N-dimethylformamide, deionized water, and 1,4-dioxane as solvents, and hydrochloric acid as a catalyst. The metal-organic framework of this invention exhibits good crystallinity and thermal stability, and possesses reversible redox activity. Electrochromic devices prepared using this framework display three different color transitions.

Description

Technical Field

[0001] This invention belongs to the field of metal-organic frameworks technology, and relates to a metal-organic framework with redox activity, its preparation method, and its application in electrochromic devices. Background Technology

[0002] Electrochromic devices are functional devices that can reversibly change their optical properties under the influence of an applied electric field. Their core working principle utilizes the altered absorption or reflection characteristics of electrochromic materials in their oxidized or reduced states to dynamically control color or transparency. Electrochromic devices are not only a key technology for achieving "intelligent energy saving," but also an important bridge connecting energy, environment, and information interaction.

[0003] Electrochromic devices still face multiple challenges in practical applications: most organic or inorganic electrochromic materials are prone to structural degradation, interface changes, or dissolution of active substances during long-term electrochemical cycling, leading to a decrease in color contrast before and after color change and a gradual increase in response speed. Secondly, it is difficult to simultaneously achieve optimal response speed and coloring efficiency. In large-area devices, long ion migration paths and high diffusion resistance result in color-changing switching times ranging from tens of seconds to several minutes, thus affecting their dynamic response capabilities. Metal-organic frameworks provide an ideal material platform for solving the aforementioned problems faced by electrochromic devices.

[0004] Metal-organic frameworks (MOFs) are a class of porous crystalline materials with periodic network structures, formed by the self-assembly of inorganic metal ions (clusters) and organic ligands through coordination bonds. These materials combine the rigidity of inorganic materials with the designability of organic molecules, possessing ultra-high specific surface area, extremely high porosity, and structural diversity and tunability. Redox MOFs, due to their unique electron transfer capabilities and structural tunability, show significant promise for applications in electrochromic fields. However, current reports on this topic are relatively limited. Therefore, to address the current challenges, it is necessary to develop MOF materials with excellent stability and reversible redox activity. Summary of the Invention

[0005] One objective of this invention is to provide a metal-organic framework material with excellent stability and reversible redox activity. The metal-organic framework uses manganese as the metal center and bis(triphenylamine)tetracarboxylic acid as the ligand. The crystallographic formula of the metal-organic framework material is [Mn3(BTPPA)2(HCO2)]·(NH2Me2)3·(H2O)3.

[0006] The structural formula of the bis(triphenylamine)tetracarboxylic acid is as follows:

[0007]

[0008] In some embodiments of the present invention, from the perspective of framework connection construction, the crystal structure of the redox metal-organic framework material belongs to the triclinic crystal system and the P1̅ space group.

[0009] In some embodiments of the present invention, the smallest asymmetric unit of the metal-organic framework material contains 3 / 2 manganese ions, one bis(triarylamine)tetracarboxylic acid ligand, and one HCO3-. 2- Ions, 3 / 2 Me2H2N molecules, and 3 / 2 free water molecules.

[0010] The second objective of this invention is to provide a method for preparing a metal-organic framework material with excellent stability and reversible redox activity. The preparation method includes adding bis(triphenylamine)tetracarboxylic acid and an inorganic manganese compound into an organic mixed solution, placing them in a reaction vessel for reaction, and obtaining the metal-organic framework material.

[0011] In some embodiments of the present invention, the selected inorganic manganese compound is selected from one or more of manganese sulfate, manganese acetate, or Mn(NO3)2·4H2O.

[0012] In some embodiments of the present invention, the molar ratio of the selected bis(triphenylamine)tetracarboxylic acid ligand to the inorganic manganese compound is 1:(8~10).

[0013] In some embodiments of the present invention, the organic mixed solution is selected from one or more of DMF, DMSO, acetonitrile and 1,4-dioxane.

[0014] In some embodiments of the present invention, the volume ratio of the organic mixed solution to deionized water is (1 ~ 3):1.

[0015] In some embodiments of the present invention, the reaction temperature is 80 ~ 100°C.

[0016] In some embodiments of the present invention, the reaction time is 24 to 48 hours.

[0017] A third objective of this invention is to provide an application of a metal-organic framework material with redox activity as described above in the field of electrochromism.

[0018] Compared with existing materials, the present invention has the following advantages:

[0019] This invention utilizes bis(triphenylamine)tetracarboxylic acid to construct a redox-active metal-organic framework material for use in optical functional devices. This material exhibits excellent chemical stability and reversible redox activity, overcoming the stability and lifetime issues present in electrochromic devices and thus possessing industrial value. It provides a novel material for functional devices that reversibly alter optical properties and offers a feasible strategy for the directional design and fabrication of functionalized MOF materials. Attached Figure Description

[0020] Figure 1 The infrared spectrum of the redox metal-organic framework material of this invention;

[0021] Figure 2 This is a diagram of the minimum asymmetric unit cell of the redox metal-organic framework material of this invention;

[0022] Figure 3 This is the PXRD pattern of the redox metal-organic framework material of this invention;

[0023] Figure 4 This is a thermogravimetric curve of the redox metal-organic framework material of the present invention;

[0024] Figure 5 This is a cyclic voltammetry curve of the redox metal-organic framework material of the present invention;

[0025] Figure 6 This is a differential pulse voltammetry curve of the redox metal-organic framework material of the present invention.

[0026] Figure 7 Optical photographs of the electrochromic device prepared by the redox metal-organic framework material of the present invention at different voltages; Detailed Implementation

[0027] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings.

[0028] The bis(triphenylamine)tetracarboxylic acid used in the following examples was prepared according to the reference [J. Am. Chem. Soc. 2019, 141, 29, 11594–11602].

[0029] The first aspect of the present invention provides a metal-organic framework material with redox activity, the material having manganese metal as the center and bis(triphenylamine)tetracarboxylic acid as the ligand, the crystallographic formula of the material being [Mn3(BTPPA)2(HCO2)]·(NH2Me2)3·(H2O)3.

[0030] The redox-active metal-organic framework material provided by this invention, from the perspective of framework connection construction, has a triclinic crystal system with space group P1̅. The smallest asymmetric unit of the metal-organic framework material contains 3 / 2 manganese ions, one bis(triphenylamine)tetracarboxylic acid ligand, and one HCO3-. 2- The metal-organic framework material contains ions, 3 / 2 Me₂H₂N molecules, and 3 / 2 free water molecules. Crystallographically, the material exhibits two independent bis(triphenylamine)tetracarboxylic acid ligands and Mn. 2+ Ions. One of the bis(triphenylamine)tetracarboxylic acid ligands is in μ 8 -η 2 η 1 η 1 η 1 η 2 η 1 η 1 η 1 The coordination mode and eight Mn 2+ Ion coordination; another with μ 6 -η 1 η 1 η 1 η 1 η 1 η 1 The coordination mode and six Mn 2+ Ion coordination. The Mn-O bond lengths range from 2.083(14) Å to 2.371(14) Å. One of the Mn... 2+ The ion exhibits a six-coordinate configuration, with six carboxylate oxygen atoms coordinated to it; the other Mn 2+ The ion is also six-coordinated, but the coordination environment includes a chelated carboxylate ion, three monodentate carboxylate ions, and an HCO3- group. 2- Ions. Three Mn 2+ Ions are bridged by carboxylate ions to form trinuclear nodes, denoted as Mn3(COO)8. These trinuclear Mn3(COO)8 units are further linked by formate ions to form a one-dimensional chain structure, denoted as [Mn3(COO)9]. n Ultimately, the linear [Mn3(COO)9]... n The chain cross-links with the bis(triphenylamine)tetracarboxylic acid ligand, forming a tightly packed three-dimensional framework.

[0031] A second aspect of the present invention provides a method for preparing a metal-organic framework material with redox activity, the method comprising adding bis(triphenylamine)tetracarboxylic acid and an inorganic manganese compound to an organic mixed solution and reacting them in a reaction to obtain the metal-organic framework material.

[0032] In the method for preparing redox-active metal-organic framework materials provided by the present invention, the inorganic manganese compound used is selected from one or more of manganese sulfate, manganese acetate, or Mn(NO3)2·4H2O.

[0033] In the method for preparing a redox-active metal-organic framework material provided by the present invention, the molar ratio of the bis(triphenylamine)tetracarboxylic acid to the inorganic manganese compound is 1:(8~10), optionally 1:(8~10), preferably 1:10.

[0034] In the method for preparing a redox-active metal-organic framework material provided by the present invention, the organic mixed solution is selected from one or more of DMF, DMSO, acetonitrile and 1,4-dioxane, preferably a combination of DMF and 1,4-dioxane.

[0035] In the preparation method of the metal-organic framework material with redox activity provided by the present invention, the volume ratio of the organic mixed solution to deionized water is (1 ~ 3): 1, optionally (1 ~ 3): 1, preferably 3: 1.

[0036] In the method for preparing a metal-organic framework material with redox activity provided by the present invention, the reaction temperature is 80-100℃, optionally 90℃ or 100℃, preferably 80℃.

[0037] In the method for preparing a metal-organic framework material with redox activity provided by the present invention, the reaction time is 24 to 48 hours, preferably 24 hours, and more preferably 48 hours.

[0038] A third aspect of this invention provides the application of a redox-active metal-organic framework material in electrochromic devices. The application mechanism is as follows: within a voltage window of 0–1.4 V, the redox-active metal-organic framework material gradually loses two electrons to generate free radical cations from bis(triphenylamine)tetracarboxylic acid. Specifically, the device prepared with the metal-organic framework undergoes a process of changing from colorless to deep yellow, and then from deep yellow to green, within the 0–1.4 V voltage window.

[0039] In the following examples, unless otherwise stated, all reactants are commercially available products.

[0040] Example 1

[0041] Preparation of the metal-organic framework material

[0042] Bistriphenylaminetetracarboxylic acid and an inorganic manganese compound were dissolved in a mixed solution of N,N-dimethylformamide, H₂O, and 1,4-dioxane. HCl was then added to the mixture. The resulting solution was heated to 80 °C and maintained at this temperature for 48 hours. Afterward, the mixture was cooled to room temperature. Filtration yielded pale yellow rod-shaped crystals, which were then washed three times with DMF. FT-IR (cm⁻¹) -1 ): 1586 s, 1520 m, 1487 m, 1398 vs, 1315 m, 1260 s, 1181 w, 1106 w, 1021 w, 1001 w, 828 s, 781 s, 730 w, 707 w, 652 w, 548 w. (like Figure 1 (As shown)

[0043] Example 2

[0044] Crystal structure analysis of the metal-organic framework material

[0045] Structural analysis: The crystal structure of the metal-organic framework material belongs to the triclinic crystal system, with space group P1̅. The smallest asymmetric unit of the metal-organic framework material contains 3 / 2 manganese ions, one bis(triphenylamine)tetracarboxylic acid ligand, and one HCO3- ion. 2- Ions, 3 / 2 Me2H2N molecules and 3 / 2 free water molecules (such as Figure 2 (As shown). The metal-organic framework material exhibits two independent bis(triphenylamine)tetracarboxylic acid ligands and Mn in its crystallography. 2+ Ions. One of the bis(triphenylamine)tetracarboxylic acid ligands is in μ 8 -η 2 η 1 η 1 η 1 η 2 η 1 η 1 η 1 The coordination mode and eight Mn 2+ Ion coordination; another with μ 6 -η 1 η 1 η 1 η 1 η 1 η 1 The coordination mode and six Mn 2+ Ion coordination. The Mn-O bond lengths range from 2.083(14) Å to 2.371(14) Å. One of the Mn... 2+ The ion exhibits a six-coordinate configuration, with six carboxylate oxygen atoms coordinated to it; the other Mn 2+The ion is also six-coordinated, but the coordination environment includes a chelated carboxylate ion, three monodentate carboxylate ions, and an HCO3- group. 2- Ions. Three Mn 2+ Ions are bridged by carboxylate ions to form trinuclear nodes, denoted as Mn3(COO)8. These trinuclear Mn3(COO)8 units are further linked by formate ions to form a one-dimensional chain structure, denoted as [Mn3(COO)9]. n Ultimately, the linear [Mn3(COO)9]... n The chain cross-links with the bis(triphenylamine)tetracarboxylic acid ligand, forming a tightly packed three-dimensional framework.

[0046] Example 3

[0047] Thermal stability analysis and powder X-ray diffraction analysis of the metal-organic framework material

[0048] To investigate the stability of the metal-organic framework material at different temperatures, this embodiment tested the material from room temperature to 800°C. The specific procedure was as follows: 3-5 mg of sample was weighed using a spatula and placed in a ceramic crucible. The mass was recorded. The test was conducted after selecting a temperature range of 50°C to 800°C and a suitable heating rate. When the temperature reached 390°C, the mass loss was 10%, which could be attributed to the escape of residual solvent from the pores (e.g., Figure 3 As shown). When the temperature exceeds 450℃, the mass loss increases sharply, and the original frame collapses (as shown). Figure 3 (As shown). To investigate the physical properties of the metal-organic framework, its phase purity and structural integrity were studied using a PXRD analysis system. The results show that its diffraction peak positions agree well with the spectra simulated based on single-crystal data, confirming that it is a pure phase (as shown). Figure 4 (As shown).

[0049] Example 4

[0050] Redox Activity Analysis of the Metal-Organic Framework

[0051] To investigate the redox activity of the metal-organic framework material, cyclic voltammetry and differential pulse voltammetry were used in this embodiment. Measurements were performed in a three-electrode system, using a glassy carbon electrode as the working electrode, a platinum wire electrode as the counter electrode, and an Ag / AgCl electrode as the reference electrode. The metal-organic framework was ground and coated onto a glassy carbon electrode for testing, using a 0.1 M (C4H9)4N⁺PF6⁻ / DMF solution as the electrolyte. Cyclic voltammetry showed that the first pair of oxidation peak half-wave potentials of the metal-organic framework material corresponded to the process of the bis(triphenylamine) ligand losing one electron to form a bis(triphenylamine) monoradical cation; the second pair of oxidation peak half-wave potentials corresponded to the process of further losing one electron to form a bis(triphenylamine) diradical cation (e.g., ...). Figure 5 As shown). The differential pulse voltammetry curve is consistent with the cyclic voltammetry test results, confirming that it underwent two different electron transfer processes (as shown). Figure 6 (As shown).

[0052] Example 5

[0053] Testing of electrochromic devices fabricated from the metal-organic framework material

[0054] Based on the redox activity of the metal-organic framework, we constructed an electrochromic device using ITO conductive glass as the working electrode. The specific procedure was as follows: 2 mg of the metal-organic framework material was ground, and then 400 µL of water, 600 µL of ethanol, and 15 µL of Nafion were added. The mixture was sonicated for 30 minutes, followed by standing for 20 minutes. An ITO conductive glass substrate (2 × 1 cm) was sequentially immersed in petroleum ether, acetone, and ethanol, and ultrasonically cleaned for 20 minutes each time. The supernatant suspension was drop-coated onto the ITO conductive glass, dried at room temperature, and then tested. The electrolyte used was 0.1 M (C₂H₅)₄N. + PF6 - Cyclic voltammetry tests showed that the metal-organic framework material exhibited two pairs of reversible redox processes on ITO conductive glass. At a scan rate of 100 mV / s, the first pair of redox peaks appeared at 0.80 V (vs Ag / AgCl), corresponding to the generation of triphenylamine radical cations within the 0.6-1.0 V potential window, and its color changed from colorless to deep yellow (e.g., ...). Figure 7 (As shown); the second pair of redox peaks appears at 1.21 V (vs Ag / AgCl), corresponding to the formation of diradical cations within the 1.2-1.4 V potential window, and the color changes from deep yellow to green (as shown). Figure 7 (As shown).

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A redox-active metal-organic framework material, characterized in that, The crystallographic formula of the material is [Mn3(BTPPA)2(HCO2)]·(NH2Me2)3·(H2O)3.

2. The redox-active metal-organic framework material according to claim 1, characterized in that, The material has a triclinic crystal system and a space group of P1̅. The smallest asymmetric unit of the metal-organic framework material contains 3 / 2 manganese ions, one bis(triarylaminetetracarboxylic acid) ligand, and one HCO3- ion. 2- Ions, 3 / 2 Me2H2N molecules, and 3 / 2 free water molecules.

3. The method for preparing redox-active metal-organic frameworks according to claim 1, characterized in that, Includes the following steps: Bistriphenylaminetetracarboxylic acid and an inorganic manganese compound were dissolved in a mixed solution of N,N-dimethylformamide, H₂O, and 1,4-dioxane. HCl was then added to the mixture. The resulting solution was heated and maintained at this temperature for a certain period. The mixture was then cooled to room temperature. Filtration yielded pale yellow rod-shaped crystals, which were then washed three times with DMF. The structural formula of the bistriphenylaminetetracarboxylic acid is as follows: 。 4. The preparation method according to claim 2, characterized in that, The inorganic manganese compound is selected from one or more of manganese sulfate, manganese acetate, or Mn(NO3)2·4H2O.

5. The preparation method according to claim 2, characterized in that, The molar ratio of the bis(triphenylamine)tetracarboxylic acid ligand to the inorganic manganese compound is 1:(8~10).

6. The preparation method according to claim 2, characterized in that, The organic mixed solution is selected from one or more of DMF, DMSO, acetonitrile and 1,4-dioxane and HCl is added.

7. The preparation method according to claim 2, characterized in that, The volume ratio of the organic mixed solution to deionized water is (1 ~ 3):

1.

8. A metal-organic framework material with redox activity as described in claim 1 for use in electrochromic devices, characterized in that, Prepared by the following steps: An electrochromic device was constructed using ITO conductive glass as the working electrode. The specific procedure was as follows: 2 mg of metal-organic framework material was ground, and then 400 µL of water, 600 µL of ethanol, and 15 µL of Nafion were added. The mixture was sonicated for 30 minutes, followed by standing for 20 minutes. An ITO conductive glass substrate (2 × 1 cm) was sequentially immersed in petroleum ether, acetone, and ethanol, and ultrasonically cleaned for 20 minutes each time. The supernatant suspension was drop-coated onto the ITO conductive glass, dried at room temperature, and then tested. The electrolyte used was 0.1 M (C₂H₅)₄N. + PF6 - .

9. The application of the redox-active metal-organic framework material according to claim 1 in electrochromic devices.

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