A three-dimensional iron-based metal-organic framework material, its preparation method and application

Abstract

This invention belongs to the fields of coordination chemistry, molecular magnetic materials, and biofunctional materials. Specifically, it discloses a three-dimensional iron-based metal-organic framework material, its preparation method, and its applications. The chemical formula of the three-dimensional iron-based metal-organic framework material is: [Formula omitted for brevity]. Wherein, is a divalent iron ion, M is a metal ion capable of forming dicyano coordination units, CN is a cyano-bridging ligand, L is a neutral nitrogen-containing bridging ligand, and G is a guest molecule. The material of this invention employs strong coordination bonds to construct a robust three-dimensional framework structure. The Fe(II) center is multiple-coordinated and fixed within the rigid framework by multidentate nitrogen-containing ligands and cyano-bridging anions. After multiple temperature-induced spin-state transition tests, the material of this invention maintains good reversibility in both its crystal structure and functional signal, without structural collapse, guest molecule loss, or ligand detachment. The material of this invention exhibits excellent cycling stability and reusability, making it more suitable for long-term operation in practical devices.

Description

Technical Field

[0001] This invention belongs to the fields of coordination chemistry, molecular magnetic materials and biofunctional materials, and relates to a three-dimensional iron-based metal-organic framework material, its preparation method and application, specifically a three-dimensional iron-based metal-organic framework material with spin crossing, dielectric response and bioactivity, its preparation method and application. Background Technology

[0002] Hofmann-type coordination polymers are a class of multidimensional functional materials constructed through the self-assembly of transition metal ions with cyanide-bridged anions and neutral nitrogen-containing ligands. Due to their flexible structural design, tunable pore size, and diverse physicochemical properties, these materials have attracted widespread attention in fields such as molecular magnets, sensors, storage devices, switching materials, adsorption separation, and biomedical applications. Among them, Fe(II)-centered Hofmann-type coordination polymers typically exhibit significant spin crossover (SCO) behavior because Fe(II) in an octahedral coordination environment can undergo reversible transitions between high-spin (HS) and low-spin (LS) states. This spin-state transition is influenced by factors such as temperature, pressure, light, electric field, host-guest interactions, and lattice flexibility. It is often accompanied by synergistic changes in the material's magnetism, color, crystal structure, and dielectric properties, giving the material multiple external responsiveness capabilities. Among these, Hofmann-type materials centered on Fe(II) exhibit significant spin crossover (SCO) behavior due to the reversible transition between high-spin and low-spin states that can occur between Fe(II) ions in an octahedral coordination environment. This type of transition is influenced by temperature, pressure, light, electric field, host-guest interactions, and lattice flexibility, and is often accompanied by synergistic changes in magnetism, color, structure, and dielectric properties, thus enabling the material to possess multiple responsive capabilities.

[0003] In current research, studies on Hofmann-type iron-based spin-crossing materials mainly focus on magnetic transitions, structural phase transitions, and gas adsorption. Research on integrating dielectric response and bioactive functions into a single three-dimensional framework material is relatively limited. In particular, materials possessing the following characteristics are still lacking: a well-defined three-dimensional Hofmann-type coordination polymer network structure; significant spin-crossing behavior; detectable dielectric response or dielectric switching effect within a certain frequency and temperature range; and clear bioactivity towards target cells or microorganisms that can be detected via IC40. 50Numerical characterization performance. Therefore, there is an urgent need to develop a three-dimensional Hofmann-type Fe-based material that possesses the aforementioned multiple functional properties, and to establish its feasible preparation method and application pathways in related fields, in order to meet the needs of novel multifunctional molecular devices and biomedical materials.

[0004] In view of the above problems, this invention is proposed. Summary of the Invention

[0005] To overcome the aforementioned drawbacks, this invention provides an iron-based coordination material with a three-dimensional Hofmann-type framework structure. This material simultaneously possesses the following beneficial properties: spin-crossing properties, dielectric response properties, and bioactivity, and can be verified through IC50 in in vitro cell experiments. 50 Numerical values ​​are used to quantitatively evaluate the bioactivity of the material. This invention also provides a method for preparing the material, and its potential applications in molecular switches, dielectric devices, sensing, information storage, and biological inhibitors (e.g., antitumor drugs, antibacterial agents).

[0006] The first objective of this invention is to provide a three-dimensional iron-based metal-organic framework material, whose general chemical formula is: ;in, M is a divalent iron ion, CN is a metal ion that can form a dicyano coordination unit, L is a cyano-bridging ligand, G is a neutral nitrogen-containing bridging ligand, and G is a guest molecule.

[0007] Preferably, in the three-dimensional iron-based metal-organic framework material, Fe(II) is in a near-octahedral configuration with N6 coordination, and the linear dicyano coordination anion... As a bridge, Fe(II) ions are connected to form a one-dimensional chain structure. Adjacent chains are then connected by bidentate ligands L to construct a positively charged three-dimensional Hofmann-type framework structure.

[0008] Preferably, M is one or more of Ag and Au.

[0009] Preferably, L is one or more of 1,3-bis(1-imidazolyl)benzene, 2,6-bis(1-imidazolyl)pyridine, 3,5-bis(1-imidazolyl)pyridine, and 3,5-bis(4-pyridyl)benzene.

[0010] Preferably, X is tetrafluoroborate or perchlorate.

[0011] Preferably, G is one or more of methanol, ethanol, acetonitrile, and DMF.

[0012] Preferably, L is 1,3-bis(1-imidazolyl)benzene (Ibz), M is Ag(I), and X is... The object G is DMF.

[0013] The second objective of this invention is to provide a method for preparing the above-mentioned three-dimensional iron-based metal-organic framework material, which synthesizes single crystals of the target complex via solution diffusion, comprising the following steps: at room temperature, taking nitrogen-containing bridging ligand L (0.03 mmol) and Dissolve (M=Ag / Au) (0.06 mmol) in 2 mL of DMF / DMA solution, stir well, place on one side of tube H, and weigh out. (X = , Dissolve 0.03 mmol in 2 mL of DMF / DMA solution and place it on the other side of the H tube, with the middle section containing... As a buffer layer, the target product was obtained by sealing with sealing film and then standing at room temperature for about 3 weeks.

[0014] A third objective of this invention is to provide applications of the above-mentioned three-dimensional iron-based metal-organic framework material in the fields of molecular switches, dielectric devices, sensing, information storage, or biological inhibitors.

[0015] The beneficial effects of this invention are:

[0016] (1) Clear spin-crossing behavior and thermal hysteresis bistable characteristics: The Fe(II) centers of the material of this invention undergo a clear reversible transition between high-spin and low-spin states with temperature changes, and exhibit a thermal hysteresis width of about 7 K between a temperature drop of about 134 K and a temperature rise of about 141 K. This reversible bistable spin-crossing behavior means that the material has a stable state in both the low-temperature and high-temperature phases, which can produce a memory-like storage effect, and can maintain the original magnetic state without continuous energy maintenance after the external conditions change. Compared with spin-crossing systems with no hysteresis or extremely narrow hysteresis, this wide hysteresis characteristic significantly improves the stability of the material's state transition and its resistance to disturbances.

[0017] (2) Dielectric response characteristics and magnetoelectric coupling effect: The dielectric constant of the material of this invention exhibits a significant step-like response to spin state transitions and is tightly coupled with the synchronously occurring magnetic transitions. This magneto-dielectric coupling effect indicates that the material possesses multi-physical response characteristics at the molecular level, enabling the manipulation of magnetism through an electric field or the induction of dielectric changes using a magnetic field. Compared with traditional materials that only output a single signal, this multi-channel synergistic response provides new possibilities for the design of novel spintronic devices, sensors, and information storage elements.

[0018] (3) Stable structure and reversible and repeatable performance: The material of this invention employs strong coordination bonds to construct a robust three-dimensional framework structure, with the Fe(II) center being multiple-coordinated and fixed within the rigid framework by multidentate nitrogen-containing ligands and cyanide bridge anions. Thanks to this design, the material of this invention maintains good reversibility in both crystal structure and functional signal after multiple temperature-induced spin-state transition tests, without structural collapse, guest molecule loss, or ligand detachment. Compared to the performance degradation of some spin-crossover complexes after multiple cycles, the material of this invention exhibits excellent cycling stability and reusability, making it more suitable for long-term operation of practical devices.

[0019] (4) Significant biological activity: In vitro MTT cell assay results showed that the material of this invention inhibited the proliferation of human lung cancer A549 cells by half (IC50). 50 The concentration of α-nitrogen (α-nitrogen) is approximately 28 μmol / L, comparable to that of the commonly used chemotherapy drug cisplatin. This result indicates that the material of this invention possesses good antitumor activity. Furthermore, since the framework of the material of this invention contains metallic components such as Ag(I), it may also have inhibitory or bactericidal effects on certain pathogens (antibacterial activity), thereby further expanding its application potential in the biomedical field.

[0020] (5) Integration of multiple functions and superior overall performance: Existing materials often possess only a single function among magnetism, dielectricity, or bioactivity, lacking a system capable of simultaneously possessing multiple response characteristics. In contrast, the material of this invention integrates multiple functions such as spin crossing (magnetic switching), dielectric response, and bioactivity in a single system. This multifunctional integration overcomes the limitations of existing technologies in achieving multiple functions simultaneously, enabling the material to possess outstanding advantages such as structural stability, significant reversible signal switching, and good bioefficacy. Therefore, the overall performance of the material of this invention is significantly better than that of traditional single-function materials, and it has broader application prospects in fields such as molecular switches, information storage, multi-channel sensing, and biomedicine. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the crystal structure of the complex of the present invention, where (a) is the smallest asymmetric unit of the complex, and (b) is the three-dimensional framework structure of the complex (all hydrogen atoms are omitted in the figure for simplicity and clarity). Figure 1 In the diagram, each element is marked with a different color: Fe is light yellow, Ag is purple, B is dark green, F is green, O is dark pink, N is blue, and C is gray.

[0022] Figure 2 The graph shows the temperature-dependent magnetic susceptibility (χMT) curve of the complex of the present invention under an applied 1 kOe magnetic field (vertical axis is molar magnetic susceptibility multiplied by temperature, horizontal axis is temperature), illustrating the spin-dependent behavior of the complex.

[0023] Figure 3 The real dielectric constant ε' of the complex of the present invention varies with temperature.

[0024] Figure 4 The change in A549 cell viability with the concentration of the complex. Detailed Implementation

[0025] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0026] This invention provides the following technical solution:

[0027] A three-dimensional iron-based metal-organic framework material, with the following general chemical formula: ;in, M is a divalent iron ion, CN is a metal ion that can form a dicyano coordination unit, L is a cyano-bridging ligand, G is a neutral nitrogen-containing bridging ligand, and G is a guest molecule.

[0028] In some embodiments, the Fe(II) in the three-dimensional iron-based metal-organic framework material is in a near-octahedral configuration with N6 coordination, and the linear dicyano coordination anion... As a bridge, Fe(II) ions are connected to form a one-dimensional chain structure. Adjacent chains are then connected by bidentate ligands L to construct a positively charged three-dimensional Hofmann-type framework structure.

[0029] In some embodiments, M is one or more of Ag and Au.

[0030] In some embodiments, L is one or more of 1,3-bis(1-imidazolyl)benzene, 3,5-bis(1-imidazolyl)pyridine, and 3,5-bis(4-pyridyl)benzene.

[0031] In some embodiments, X is tetrafluoroborate or perchlorate.

[0032] In some embodiments, G is one or more of methanol, ethanol, acetonitrile, and DMF.

[0033] In some embodiments, L is 1,3-bis(1-imidazolyl)benzene (Ibz), M is Ag(I), and X is... The object G is DMF.

[0034] The preparation method of the above-mentioned three-dimensional iron-based metal-organic framework material includes the following steps: taking nitrogen-containing bridging ligand L (0.03 mmol) and Dissolve (M=Ag / Au) (0.06 mmol) in 2 mL of DMF / DMA solution, stir well, place on one side of tube H, and weigh out. (X = , Dissolve 0.03 mmol in 2 mL of DMF / DMA solution and place it on the other side of the H tube, with the middle section containing... As a buffer layer, the product was obtained by sealing with sealing film and allowing it to stand at room temperature for about 3 weeks. .

[0035] The aforementioned three-dimensional iron-based metal-organic framework materials have applications in the fields of molecular switches, dielectric devices, sensing, information storage, or biological inhibitors.

[0036] Example 1

[0037] Synthesis: Single crystals of the target complex were synthesized at room temperature via solution diffusion. The specific steps were as follows: 1,3-bis(1-imidazolyl)benzene (6.3 mg, 0.03 mmol) and... Dissolve (11.9 mg, 0.06 mmol) in 2 mL of DMF solution, stir well, place on one side of tube H, and weigh out. (10.1 mg, 0.03 mmol) dissolved in 2 mL of DMF solution, placed on the other side of tube H, with the middle... As a buffer layer, colorless blocky crystals were obtained by sealing with a sealing film and allowing to stand at room temperature for about 3 weeks. The yield was approximately 26%. Elemental analysis ( Theoretical values ​​(mass percentage %): C 41.19, H 3.67, N 18.01; Measured values: C 41.46, H 3.95, N 18.33. The analytical results indicate that the product composition is consistent with the target compound.

[0038] Example 2

[0039] Synthesis: Single crystals of the target complex were synthesized at room temperature via solution diffusion. The specific steps were as follows: 1,3-bis(1-imidazolyl)benzene (6.3 mg, 0.03 mmol) and... Dissolve (11.9 mg, 0.06 mmol) in 2 mL of DMF solution, stir well, place on one side of tube H, and weigh out. (10.19 mg, 0.03 mmol) dissolved in 2 mL of DMF solution, placed on the other side of tube H, with the middle... As a buffer layer, colorless blocky crystals were obtained by sealing with a sealing film and allowing to stand at room temperature for about 3 weeks. The yield was approximately 33%. Elemental analysis ( Theoretical values ​​(mass percentage %): C 43.58, H 3.89, N 19.06; Measured values: C 43.79, H 4.01, N 19.28. Analytical results indicate that the product composition is consistent with the target compound. The cyano building blocks and ligand structures are as follows:

[0040]

[0041] The product obtained in Example 1 The following experimental analysis was conducted:

[0042] Experimental Example 1: Crystal Structure Analysis

[0043] The crystal structure of the above-mentioned complex was determined by single-crystal X-ray diffraction. Figure 1 The results showed that the complex crystal belongs to the monoclinic system, space group C2 / c. The asymmetric unit contains 0.5 Fe(II) ions (occupying special positions) and 0.5 Fe(II) ions... The complex consists of an anion, one Ibz ligand, and 0.5 free ions. Counteracting anions. From linear... Anion-bridged Fe(II) ions form a one-dimensional chain structure, and adjacent chains are then connected by bidentate ligands Ibz, assembling into a positively charged three-dimensional porous framework structure (e.g., Figure 1 (As shown). In this three-dimensional framework, the Fe(II) ion is in an octahedral environment with N6 coordination: the equatorial plane of each Fe(II) is occupied by four imidazole nitrogen atoms of Ibz ligands, while the axial direction is coordinated by nitrogen atoms of two cyanide anions. To study the spin state change of this complex, the Fe–N bond lengths in the single crystal structure at different temperatures were measured and analyzed. The results showed that at a temperature of 200 K, the Fe–N bond lengths ranged from 2.149(5)–2.186(5) Å, with an average of about 2.170 Å; when the temperature was reduced to 100 K, the Fe–N bond lengths shortened to 1.937(6)–2.013(5) Å, with an average of about 1.972 Å, and the average difference between the two was about 0.198 Å. This significant bond length change indicates that the Fe(II) center changed from a high-spin state to a low-spin state during the cooling process, that is, thermally induced spin crossing occurred.

[0044] Experimental Example 2: Magnetic Characterization

[0045] The temperature-dependent magnetic susceptibility χ of the complexes of this invention was measured using the SQUID magnetic measurement system in a temperature range of 2–300 K and an applied magnetic field of 1 kOe. M T( Figure 2 At 300 K, the χ of the complex M T value at 3.6 cm 3 ·mol−1 Around K, it matches the spin value of the high-spin Fe(II). As the temperature decreases to approximately 150 K, χ M The T value remained essentially unchanged. As the temperature continued to decrease to 134 Kχ M The T value dropped rapidly to 0.56 cm. 3 ·mol -1 ·K(T) 1 / 2↓ = 134 K), indicating that Fe(II) has completely transformed into a low-spin state (S=0), which remains in a low-spin state in the range of 2–120 K. During the heating process of 2–120 K, χ M The T value is between 0.18 and 0.56 cm. 3 ·mol −1 Between K, as the temperature further increases, χ M The T value recovers to the initial state of 3.6 cm. 3 ·mol −1 K(T) 1 / 2↑ = 141 K). This temperature variation process shows that the complex underwent a reversible spin-crossing conversion and exhibited a thermal hysteresis width of approximately 7 K during cooling / heating. Therefore, the material of this invention exhibits bistable magnetic switching behavior in the range of approximately 134–141 K. The occurrence of this thermal hysteresis phenomenon may be related to the interaction between host and guest molecules within the framework: the interaction between the guest DMF molecules and the framework pore walls varies at different temperatures, causing lattice distortion and stress hysteresis, thus producing a significant hysteresis effect during the spin-crossing process.

[0046] Experimental Example 3: Dielectric Property Characterization

[0047] The material of this invention exhibits an unusual change in dielectric properties during the spin-state transition. After observing the bistable transition of the Fe(II) spin state in variable-temperature magnetic measurements, we tested the behavior of the dielectric constant (real part ε′) of the complex as a function of temperature. Figure 3As shown, the dielectric curves of this complex exhibit a step-like abrupt change around approximately 142 K at different test frequencies. This indicates that the polarization properties of the material change drastically when Fe(II) transitions from a high-spin state to a low-spin state. Generally, during cooling, the orientation polarization of molecular dipoles tends to increase due to reduced thermal motion, but at the same time, molecular reorientation becomes more difficult as the temperature decreases. This competitive interaction often leads to a peak-like change in the dielectric constant (the so-called "peak-shaped" switching behavior). In the material of this invention, these two factors are precisely balanced, resulting in a step-like switching of the dielectric constant, corresponding to a difference in electric dipole moment between the high-spin (HS) and low-spin (LS) states of Δε' ≈ 0.6. This dielectric anomaly is consistent with the aforementioned bistable transition temperature range of the magnetism, proving that the magnetic and dielectric properties of this material are coupled at the molecular level. This property makes the material a promising candidate for use in devices where magnetic and electric fields are cross-controlled, for example, by switching the dielectric and magnetic states of the material through temperature or field triggering.

[0048] Experimental Example 4: Cell Culture and Antitumor Activity Test

[0049] To evaluate the bioactivity of the complexes of this invention, we used the MTT assay to test their in vitro inhibitory effect on the human non-small cell lung cancer cell line A549. Specifically, A549 cells in logarithmic growth phase were inoculated at 5 × 10⁻⁶ cells / cells. 4 Cells were seeded at a density of [number] cells / mL in 96-well cell culture plates and cultured at 37°C and 5% CO2 for 24 h. Subsequently, except for the control group, culture medium containing different concentrations of the complex of this invention was added to each well, and the cells were cultured for another 24 h, followed by incubation with MTT reagent for approximately 4 h. After culture, the purple crystals formed in the cells were dissolved with dimethyl sulfoxide (DMSO), and the optical density (OD value) of each well was measured at 490 nm using a microplate reader. Cell viability was calculated, and a dose-response curve was plotted to obtain the half-maximal inhibitory concentration (IC50) of the complex on A549 cell proliferation. 50 Test results showed that the complex of this invention had an IC50 value against A549 tumor cells. 50 Approximately 28 μmol / L ( Figure 4 This activity level is comparable to the in vitro inhibitory effect of the commonly used chemotherapy drug cisplatin on this cell line. Therefore, the material of this invention can be considered to have good potential in inhibiting cancer cell growth and is expected to be developed as an anti-tumor drug or related biomedical material. In addition, since the complex framework contains metal components such as Ag(I), it may also have inhibitory or bactericidal effects on certain pathogens (antibacterial activity), which further expands its biomedical application prospects.

[0050] The material of this invention has the following advantages in terms of structure and performance:

[0051] (1) Clear spin-crossing behavior and thermal hysteresis bistable characteristics: The Fe(II) centers of the material of this invention undergo a clear reversible transition between high-spin and low-spin states with temperature changes, and exhibit a thermal hysteresis width of about 7 K between a temperature drop of about 134 K and a temperature rise of about 141 K. This reversible bistable spin-crossing behavior means that the material has a stable state in both the low-temperature and high-temperature phases, which can produce a memory-like storage effect, and can maintain the original magnetic state without continuous energy maintenance after the external conditions change. Compared with spin-crossing systems with no hysteresis or extremely narrow hysteresis, this wide hysteresis characteristic significantly improves the stability and disturbance resistance of the material's state transition.

[0052] (2) Dielectric response characteristics and magnetoelectric coupling effect: The dielectric constant of the material of this invention exhibits a significant step-like response to spin state transitions and is tightly coupled with the synchronously occurring magnetic transitions. This magneto-dielectric coupling effect indicates that the material possesses multi-physical response characteristics at the molecular level, enabling the manipulation of magnetism through an electric field or the induction of dielectric changes using a magnetic field. Compared with traditional materials that only output a single signal, this multi-channel synergistic response provides new possibilities for the design of novel spintronic devices, sensors, and information storage elements.

[0053] (3) Stable structure and reversible and repeatable performance: The material of this invention employs strong coordination bonds to construct a robust three-dimensional framework structure, with the Fe(II) center being multiple-coordinated and fixed within the rigid framework by multidentate nitrogen-containing ligands and cyanide bridge anions. Thanks to this design, the material of this invention maintains good reversibility in both crystal structure and functional signal after multiple temperature-induced spin-state transition tests, without structural collapse, guest molecule loss, or ligand detachment. Compared to the performance degradation of some spin-crossover complexes after multiple cycles, the material of this invention exhibits excellent cycling stability and reusability, making it more suitable for long-term operation of practical devices.

[0054] (4) Significant biological activity: In vitro MTT cell assay results showed that the material of this invention inhibited the proliferation of human lung cancer A549 cells by half (IC50). 50 The concentration of α-nitrogen (α-nitrogen) is approximately 28 μmol / L, comparable to that of the commonly used chemotherapy drug cisplatin. This result indicates that the material of this invention possesses good antitumor activity. Furthermore, since the framework of the material of this invention contains metallic components such as Ag(I), it may also have inhibitory or bactericidal effects on certain pathogens (antibacterial activity), thereby further expanding its application potential in the biomedical field.

[0055] (5) Integration of multiple functions and superior overall performance: Existing materials often possess only a single function among magnetism, dielectricity, or bioactivity, lacking a system capable of simultaneously possessing multiple response characteristics. In contrast, the material of this invention integrates multiple functions such as spin crossing (magnetic switching), dielectric response, and bioactivity in a single system. This multifunctional integration overcomes the limitations of existing technologies in achieving multiple functions simultaneously, enabling the material to possess outstanding advantages such as structural stability, significant reversible signal switching, and good bioefficacy. Therefore, the overall performance of the material of this invention is significantly better than that of traditional single-function materials, and it has broader application prospects in fields such as molecular switches, information storage, multi-channel sensing, and biomedicine.

[0056] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or basic characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0057] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A three-dimensional iron-based metal-organic framework material, characterized in that, Its general chemical formula is ;in, M is a divalent iron ion, CN is a metal ion that can form a dicyano coordination unit, L is a cyano-bridging ligand, G is a neutral nitrogen-containing bridging ligand, and G is a guest molecule.

2. The three-dimensional iron-based metal-organic framework material as described in claim 1, characterized in that, In the three-dimensional iron-based metal-organic framework material, Fe(II) is in a near-octahedral configuration with N6 coordination, and linear dicyano coordination anions... As a bridge, Fe(II) ions are connected to form a one-dimensional chain structure. Adjacent chains are then connected by bidentate ligands L to construct a positively charged three-dimensional Hofmann-type framework structure.

3. A three-dimensional iron-based metal-organic framework material as described in claim 1, characterized in that, M is one or more of Ag and Au.

4. A three-dimensional iron-based metal-organic framework material as described in claim 1, characterized in that, The L is one or more of 1,3-bis(1-imidazolyl)benzene, 2,6-bis(1-imidazolyl)pyridine, 3,5-bis(1-imidazolyl)pyridine, and 3,5-bis(4-pyridyl)benzene.

5. A three-dimensional iron-based metal-organic framework material as described in claim 1, characterized in that, X is tetrafluoroborate or perchlorate.

6. A three-dimensional iron-based metal-organic framework material as described in claim 1, characterized in that, G is one or more of methanol, ethanol, acetonitrile, and DMF.

7. A three-dimensional iron-based metal-organic framework material as described in claim 1, characterized in that, The L is 1,3-bis(1-imidazolyl)benzene (Ibz), M is Ag(I) or Au(I), and X is... or The object G is DMF, DMA or EtOH.

8. A method for preparing a three-dimensional iron-based metal-organic framework material as described in any one of claims 1-8, characterized in that, The procedure includes the following steps: at room temperature, take 0.03 mmol of nitrogen-containing bridging ligand L and 0.06 mmol of... Dissolve in 2 mL of DMF / DMA solution, stir well, place on one side of tube H, and weigh 0.03 mmol. Dissolve in 2 mL of DMF / DMA solution, place on the other side of tube H, and use in the middle As a buffer layer, the product was obtained by sealing and allowing it to stand at room temperature for 3 weeks.

9. An application of a three-dimensional iron-based metal-organic framework material as described in any one of claims 1-8, characterized in that, Applications in the fields of molecular switches, dielectric devices, sensing, information storage, or biological inhibitors.

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