Hofmann-type two-dimensional organic material, preparation method therefor, and use thereof

Abstract

Provided in the present application are a Hofmann-type two-dimensional organic material, a preparation method therefor, and the use thereof. The structural formula of the Hofmann-type two-dimensional organic material is M1(L)2[M2(CN)4], wherein M1 comprises at least one of Mn, Fe, Co, Ni, Cu or Zn, M2 comprises at least one of Ni, Cu, Pd or Pt, and L comprises at least one of N,N-dimethylformamide, dimethylacetamide or dimethyl sulfoxide. The present application uses a ligand exchange method to perform diffusion and substitution reactions of an organic ligand, and uses [M2(CN)4]2- (M2 = Ni, Cu, Pd or Pt) as a construction unit in cooperation with different transition metal ions (M1), so as to synthesize a series of metal organic framework Hofmann-type two-dimensional organic materials M1(L)2[M2(CN)4].

Description

Organic Hofmann-type two-dimensional materials and their preparation methods and applications Technical Field

[0001] The present application relates to the technical field of two-dimensional materials, and in particular to an organic Hofmann-type two-dimensional material and a preparation method and application thereof. Background Art

[0002] At present, two-dimensional materials refer to materials with a layered structure, extremely high specific surface area and atomic-scale thickness. Due to the atomic-scale thickness, the movement of electrons is limited to two-dimensional space, the quantum scale effect is obvious, and the internal chemical bond network is highly uniform and ordered, which reduces the influence of structural defects, giving two-dimensional materials broad application prospects in catalysis, energy storage, sensors, etc. In recent years, scientific researchers have attempted to construct two-dimensional materials containing both metal coordination structures and organic ligands, namely metal-organic frameworks (MOFs) two-dimensional materials, in order to achieve the synergistic advantages of inorganic and organic components and achieve multi-component composition and performance. However, there are still few metal-organic two-dimensional materials reported so far, and the design and preparation of new metal-organic two-dimensional materials are current research hotspots and difficulties.

[0003] Summary of the Invention

[0004] In view of this, the present application provides an organic Hofmann-type two-dimensional material and its preparation method and application.

[0005] To achieve the above-mentioned objectives, the present application provides an organic Hofmann-type two-dimensional material, the structural formula of which is M1(L)2[M2(CN)4], wherein M1 includes at least one of Mn, Fe, Co, Ni, Cu or Zn, M2 includes at least one of Ni, Cu, Pd or Pt, and L includes at least one of N,N-dimethylformamide, dimethylacetamide or dimethyl sulfoxide.

[0006] In some possible implementations, in M1(L)2[M2(CN)4], the mass percentage of L is 10 wt% to 40 wt%.

[0007] The present application also provides a method for preparing an organic Hofmann-type two-dimensional material, the preparation method comprising: dissolving a tetracyanometallate in water to obtain a tetracyanometallate solution, wherein the tetracyanometallate contains a metal R and a metal M2, wherein R includes at least one of Na or K, and M2 includes at least one of Ni, Cu, Pd, or Pt; mixing a salt solution containing the metal M1 with the tetracyanometallate solution, and stirring to obtain M1(H2O)2[M2(CN)4]·x A H2O precursor, M1 includes at least one of Mn, Fe, Co, Ni, Cu or Zn; adsorbed water in the precursor is removed to obtain M1(H2O)2[M2(CN)4]; M1(H2O)2[M2(CN)4] is mixed with an organic ligand solvent and a ligand exchange reaction is carried out, and then dried to obtain M1(L)2[M2(CN)4], wherein L includes at least one of N,N-dimethylformamide, dimethylacetamide or dimethyl sulfoxide.

[0008] In some possible implementations, the salt solution containing the metal M1 includes a metal salt and water, wherein the molar ratio of the metal salt to the tetracyanometallate is 1-5.

[0009] In some possible implementations, a dispersant is further added to the salt solution containing the metal M1, and the dispersant includes at least one of trisodium citrate dihydrate or polyvinyl pyrrolidone.

[0010] In some possible implementations, the anions in the salt solution containing the metal M1 include at least one of nitrate, sulfate, chloride, or acetate.

[0011] In some possible implementations, the precursor is heated under vacuum at 100-110° C. to remove adsorbed water.

[0012] In some possible implementations, the solid-liquid ratio of M1(H2O)2[M2(CN)4] after mixing with the organic ligand solvent is 1:10 to 1:100.

[0013] In some possible implementations, the process of mixing the salt solution containing the metal M1 with the tetracyanometallate solution includes: dropwise adding one of the salt solution containing the metal M1 and the tetracyanometallate solution into the other.

[0014] This application also provides an application of an organic Hofmann-type two-dimensional material in the fields of composite solid electrolytes and gas screening.

[0015] The M1(L)2[M2(CN)4] provided in the present application is composed of an M1 metal site and an M2 metal site, an organic ligand and a cyano group. The M1 metal site forms a coordination bond with the N atoms in the four cyano groups and the highly electronegative atoms in the organic ligand L to obtain an octahedral, hexacoordinate structure, and the M2 metal site forms a coordination bond with the C in the four cyano groups to obtain a planar structure, so that the crystal extends along a two-dimensional direction during the growth process to form a two-dimensional nanolayered structure. The present application prepares a two-dimensional material containing a metal coordination structure and an organic ligand, realizes the synergistic advantages of inorganic components and organic components, and realizes multi-component composition and performance. M1(L)2[M2(CN)4] has good stability, large pore size and specific surface area, good ligand substitutability, and shows great application potential in the fields of gas adsorption, gas screening and composite solid electrolytes. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG1 is a schematic diagram of the process for preparing the organic Hofmann-type two-dimensional material provided in this application.

[0017] Figure 2 is a molecular structure diagram of the organic Hofmann-type two-dimensional material M1(L)2[M2(CN)4] provided in this application.

[0018] FIG3 is a molecular structure diagram of the organic Hofmann-type two-dimensional material M1(L)2[M2(CN)4] shown in FIG2 from another perspective.

[0019] FIG4 is a molecular structure diagram of Ni(DMF)2[Ni2(CN)4] prepared in Example 1.

[0020] FIG5 is a Fourier transform infrared spectrum of Ni(DMF)2[Ni2(CN)4] prepared in Example 1.

[0021] FIG6 is a scanning electron microscope image of Ni(DMF)2[Ni2(CN)4] prepared in Example 1.

[0022] FIG7 is an X-ray diffraction pattern of Ni(DMF)2[Ni2(CN)4] prepared in Example 1.

[0023] FIG8 is a nitrogen adsorption-desorption curve of Ni(DMF)2[Ni2(CN)4] prepared in Example 1.

[0024] Figure 9 is a thermogravimetric diagram of Ni(DMF)2[Ni2(CN)4] prepared in Example 1.

[0025] FIG10 is a physical picture of the composite solid electrolyte containing Ni(DMF)2[Ni(CN)4] prepared in Example 2 after bending.

[0026] FIG11 is an impedance diagram of the composite solid electrolyte prepared in Example 2.

[0027] FIG12 is a scanning electron microscope image of Co(DMF)2[Ni2(CN)4] prepared in Example 3.

[0028] FIG13 is a scanning electron microscope image of Ni(DMF)2[Ni2(CN)4] prepared in Example 4. DETAILED DESCRIPTION

[0029] The embodiments of the present invention are described in detail below. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be understood as limiting the present invention.

[0030] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0031] Organic Hofmann-type two-dimensional layered coordination compounds are a class of inorganic-organic hybrid materials with a two-dimensional skeleton topology. The typical organic Hofmann topology includes structural elements such as a central metal coordination octahedron, interlayer cyano bridges, and outer layer organic cation supplements. Due to their unique composition and structure, two-dimensional organic Hofmann-type materials can be used as components of composite solid-state electrolytes to achieve lithium transport and are used in fields such as gas adsorption or gas screening. The design and preparation of two-dimensional organic Hofmann-type metal-organic materials will further broaden the types of two-dimensional materials and achieve the synergy of multiple components and diverse properties. However, the current research on this type of material is relatively limited, and breakthroughs are urgently needed in the preparation technology with simple and controllable synthesis methods and high yields.

[0032] The present application provides an organic Hofmann-type two-dimensional material, the structural formula of which is M1(L)2[M2(CN)4], wherein M1 includes at least one of Mn, Fe, Co, Ni, Cu or Zn, M2 includes at least one of Ni, Cu, Pd or Pt, and L includes at least one of N,N-dimethylformamide, dimethylacetamide or dimethyl sulfoxide.

[0033] In this application, the two-dimensional material refers to an organic Hofmann-type two-dimensional material M1(L)2[M2(CN)4], which is composed of an M1 metal and an M2 metal, an organic ligand, and a cyano group. As shown in Figure 2, the M1 metal forms coordination bonds with the nitrogen atoms in the four cyano groups and the highly electronegative atoms in the two organic ligands L, resulting in an octahedral, hexacoordinated structure. Furthermore, as shown in Figure 3, the M2 metal forms coordination bonds with the carbon atoms in the four cyano groups, resulting in a planar structure. This allows the crystal to extend along a two-dimensional direction during growth, forming a two-dimensional nanolayered structure.

[0034] In some embodiments, M1 and M2 are both Ni metal, and the organic ligand L is N,N-dimethylformamide (DMF), thereby forming the two-dimensional material Ni(DMF)2[Ni(CN)4]. Figure 4 shows a molecular structure diagram of a cross-section of the two-dimensional material Ni(DMF)2[Ni(CN)4].

[0035] Referring to FIG1 , the present application also provides a method for preparing an organic Hofmann-type two-dimensional material, comprising:

[0036] S1. Dissolving a tetracyanometallate in water to obtain a tetracyanometallate solution, wherein the tetracyanometallate contains a metal R and a metal M2, M2 includes at least one of Ni, Cu, Pd or Pt, and R includes at least one of Na or K.

[0037] The tetracyanometallate salt may be at least one of potassium tetracyanonickelate, sodium tetracyanocuprate, potassium tetracyanoplatinate, and potassium tetracyanopalladate.

[0038] S2. Mixing a salt solution containing metal M1 with the tetracyanometallate solution, stirring, and obtaining a M1(H2O)2[M2(CN)4]·xH2O precursor, wherein M1 includes at least one of Mn, Fe, Co, Ni, Cu, or Zn.

[0039] In some embodiments, the salt solution containing the metal M1 comprises a metal salt and water, and the metal salt is dissolved in water to obtain the salt solution containing the metal M1. The metal M1 is selected from a transition metal, and the metal salt is a transition metal salt. In some embodiments, a dispersant is further added to the salt solution containing the metal M1, and the dispersant comprises at least one of trisodium citrate dihydrate or polyvinylpyrrolidone. The dispersant can promote the dissolution and dispersion of the metal salt and reduce agglomeration of the salt solution containing the metal M1.

[0040] In some embodiments, the anions in the salt solution containing the metal M1 include at least one of nitrate, sulfate, chloride, or acetate, and the anions are used as acid ions in the salt solution containing the metal M1.

[0041] In some embodiments, the molar ratio of the metal salt to the tetracyanometallate is 1 to 5, within which the salt solution containing the metal M1 and the tetracyanometallate are fully reacted. If the molar ratio of the two is too large, the concentration of one of them after mixing is too high, which will cause the local coordination polymerization reaction of the two to be too fast and the crystal growth to be too fast, thereby making the structure and morphology of the two-dimensional material uneven, which is not conducive to the uniform growth of the crystal. At the same time, if the molar ratio of the two is too small, the reaction of the two is too slow and the yield is low. In some embodiments, the molar ratio of the two can be 1, 2, 3, 4 or 5.

[0042] In some embodiments, the concentration of the salt solution containing the metal M1 is 0.1-1 mol / L, and the concentration may be 0.1 mol / L, 0.2 mol / L, 0.5 mol / L, 0.8 mol / L, or 1 mol / L.

[0043] In some embodiments, mixing the salt solution containing the metal M1 with the tetracyanometallate solution comprises dropwise adding one of the salt solution containing the metal M1 and the tetracyanometallate solution to the other. Specifically, the salt solution containing the metal M1 is dropwise added to the tetracyanometallate solution, or the tetracyanometallate solution is dropwise added to the salt solution containing the metal M1, with continuous stirring during the addition process to ensure thorough mixing and reaction. After the reaction, the mixture is allowed to stand to precipitate, which is then collected to obtain the M1(H2O)2[M2(CN)4]·xH2O precursor.

[0044] In some embodiments, the precipitate is collected by filtering, centrifuging, or concentrating the precipitate, and the precipitate is washed with water and ethanol, and dried to obtain the precursor. The drying step includes heating or vacuum drying.

[0045] S3. Remove the adsorbed water in the precursor to obtain M1(H2O)2[M2(CN)4].

[0046] In some embodiments, the precursor is heated at 100-110° C. to remove adsorbed water. In some embodiments, the precursor is heated at 100-110° C. to remove adsorbed water under vacuum.

[0047] S4. M1(H2O)2[M2(CN)4] is mixed with an organic ligand solvent and a ligand exchange reaction is carried out, followed by drying to obtain M1(L)2[M2(CN)4], wherein L includes at least one of N,N-dimethylformamide (DMF), dimethylacetamide (DMAc) or dimethyl sulfoxide (DMSO).

[0048] In the above ligand exchange reaction, the organic ligand is exchanged with the H2O in M1(H2O)2[M2(CN)4] to obtain M1(L)2[M2(CN)4].

[0049] In some embodiments, in M1(L)2[M2(CN)4], the mass percentage of the organic ligand L is 10 wt % to 40 wt %. Thermogravimetric analysis and infrared analysis indicate that the mass percentage of the organic ligand L is within the above range.

[0050] In some embodiments, the solid-to-liquid ratio of M1(H2O)2[M2(CN)4] after mixing with the organic ligand solvent is 1:10 to 1:100. At this solid-to-liquid ratio, the excessive amount of organic ligand solvent added promotes the spontaneous reaction between the two, thereby promoting the full replacement of the H2O in M1(H2O)2[M2(CN)4] by the organic ligand, thereby allowing the two to fully react. For example, the solid-to-liquid ratio is 1:10, 1:20, 1:30, 1:50, 1:80, or 1:100.

[0051] In some embodiments, M1(H2O)2[M2(CN)4] is mixed with an organic ligand solvent and stirred at 25-60°C for a ligand substitution reaction, followed by drying to obtain M1(L)2[M2(CN)4]. Drying can include at least one of heating, vacuum drying, or freeze drying. The heating temperature is 80-100°C.

[0052] This application adopts the ligand exchange method (the ligand exchange method can be understood as using a ligand substance with coordination function to replace the ligand in another substance to obtain a new substance with a more stable structure) to carry out the diffusion and substitution reaction of the organic ligand, using [M2(CN)4] 2- (M2 = Ni, Cu, Pd or Pt) as a building block, in combination with different transition metal ions (M1), a series of metal organic framework-type organic Hofmann-type two-dimensional materials M1(L)2[M2(CN)4] can be synthesized. The preparation method of organic Hofmann-type two-dimensional materials has a short process and low cost, has excellent environmental advantages and high economic benefits, and is suitable for large-scale batch synthesis. By optimizing metal sites and ligands, a variety of organic Hofmann-type two-dimensional materials M1(L)2[M2(CN)4] can be synthesized. Two-dimensional materials containing metal coordination structures and organic ligands can be prepared in a controlled manner, realizing the synergistic advantages of inorganic and organic components, and achieving multi-component composition and performance.

[0053] At the same time, M1(L)2[M2(CN)4] has good stability, large pore size and specific surface area, good ligand substitutability, and shows great application potential in the fields of gas adsorption, gas screening and composite solid electrolytes.

[0054] The present application also provides an application of an organic Hofmann-type two-dimensional material in the fields of composite solid electrolytes and gas screening.

[0055] The organic Hofmann-type two-dimensional material M1(L)2[M2(CN)4] prepared in this application can be applied to composite solid electrolyte components and gas screening. In composite solid electrolytes, organic Hofmann-type two-dimensional materials can coordinate with lithium ions to form a solvated structure through ligands (DMF, DMAc or DMSO) to assist the ion conduction process (which can be understood as: the ligands in the two-dimensional material coordinate with the lithium ions in the electrolyte and transport the lithium ions to move, and a vacancy is formed at the original position of the ligand; when the lithium ions are transported to the adjacent ligand position, the adjacent ligand coordinates with the lithium ions, and the original ligand returns to the vacant position of the original ligand under the intramolecular force. During the lithium ion transport process, the local structure of the two-dimensional material changes, but the overall structure is in dynamic equilibrium, and the lithium ions are transported in sequence through multiple ligands.), and the organic ligand can controllably adjust the coordination strength with the lithium ions, thereby constructing an efficient lithium ion transport channel to accelerate lithium ion conduction and prepare a composite solid electrolyte with high ionic conductivity and electrochemical stability.

[0056] In addition, organic Hofmann-type two-dimensional materials have larger pore sizes and pore volumes, which can be used to accommodate more gas molecules. The metal sites in the two-dimensional materials can interact with a variety of organic ligands, confining them between layers, forming multi-coordination effects on gas molecules, showing stronger gas molecule adsorption forces and higher adsorption selectivity. This heterogeneous pore channel is very beneficial for simultaneously improving gas adsorption capacity and separation selectivity. This unique physical structure and chemical interaction indicate that organic Hofmann-type two-dimensional materials M1(L)2[M2(CN)4] have great development potential in the fields of gas storage and gas screening.

[0057] The preparation of the composite solid electrolyte includes: mixing a polymer solid electrolyte matrix and a lithium salt and dissolving the mixture in an organic polar solution to obtain a mixed solution.

[0058] The M1(L)2[M2(CN)4] sample dried in step S4 is mixed with the mixed solution and stirred until uniformly mixed. The mixed solution is then applied to a glass plate using a solution casting method and dried for 4 to 12 hours to obtain a homogeneous composite solid electrolyte. The drying method can be vacuum drying or drying in an argon atmosphere glove box. The drying temperature is 60°C to 80°C.

[0059] Among them, the polymer solid electrolyte matrix can be at least one of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), and polyethylene oxide (PEO); the lithium salt can be at least one of lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and lithium hexafluorophosphate (LiPF6); and the organic polar solution can be at least one of DMF and DMSO organic solutions.

[0060] The present invention will be explained below with reference to the embodiments. Those skilled in the art will appreciate that the following examples are intended only to illustrate the present invention and are not to be construed as limiting the present invention. Unless otherwise indicated, the reagents, software, and instruments not specifically described in the following examples are all conventional commercially available products or open source.

[0061] Example 1

[0062] In this embodiment, an organic Hofmann-type two-dimensional material M1(L)2[M2(CN)4] is prepared, where M1 and M2 are both metal Ni, and L is N,N-dimethylformamide (DMF). That is, the two-dimensional material is Ni(DMF)2[Ni2(CN)4]. The preparation process is shown in Figure 1 and specifically includes the following steps:

[0063] S1. Dissolve 0.95 g of NiCl2·6H2O and 0.88 g of trisodium citrate dihydrate in 40 mL of water and stir magnetically for 1 hour to obtain a uniform and stable salt solution containing metallic Ni. Dissolve 0.48 g of potassium tetracyanonitricholate (K2[Ni(CN)4]) in 40 mL of water and stir magnetically to obtain a uniform potassium tetracyanonitricholate solution.

[0064] S2. A salt solution containing nickel chloride and trisodium citrate dihydrate was mixed with a potassium tetracyanonicbond solution and magnetically stirred. After stirring for 4 hours, the mixture was allowed to stand for 8 hours. The mixture was centrifuged and washed with water and ethanol to obtain a light blue Ni(H2O)2[Ni(CN)4]·xH2O precursor.

[0065] S3. Dehydrate the Ni(H2O)2[Ni(CN)4]·xH2O precursor in vacuum at 100°C to remove adsorbed water and obtain khaki Ni(H2O)2[Ni(CN)4].

[0066] S4. Add 0.2 g of Ni(H2O)2[Ni(CN)4] to 2 mL of DMF solvent and magnetically stir at room temperature for 1 hour to perform a ligand exchange reaction. Remove excess DMF solvent and displaced water molecules by vacuum drying to obtain avocado green Ni(DMF)2[Ni(CN)4] powder.

[0067] Referring to Figure 5, the present application uses Fourier transform infrared spectroscopy (FT-IR) to perform component analysis on Ni(H2O)2[Ni(CN)4]·xH2O and Ni(DMF)2[Ni(CN)4] prepared in Example 1. The results are shown in Figure 5. Compared with the spectrum of Ni(H2O)2[Ni(CN)4]·xH2O, it shows that after the ligand exchange reaction, in the spectrum of Ni(DMF)2[Ni(CN)4], the characteristic peaks of OH and HOH in Ni(H2O)2[Ni(CN)4]·xH2O do not appear in Ni(DMF)2[Ni(CN)4]. Instead, an obvious C=O characteristic peak appears, indicating that the ligand exchange process is complete and the DMF ligand has replaced H2O.

[0068] FIG6 is a scanning electron microscope image of the Ni(DMF)2[Ni(CN)4] powder sample prepared in Example 1. As can be seen from FIG6, Ni(DMF)2[Ni(CN)4] presents a lamellar structure with a size of 300 to 500 nm and no obvious impurity phase.

[0069] The crystal structure of the prepared Ni(DMF)2[Ni(CN)4] is shown in Figure 4. The coordination compound belongs to the monoclinic system and the space group is C2 / m. The tetracoordinated Ni(M2) center at the inversion center has a planar square coordination configuration, and the bond lengths of the CN bond and the Ni-C bond are and The Ni-C≡N bond is almost linear. The hexacoordinated metal Ni (M1) is coordinated with four nitrogen atoms of the cyano group and two oxygen atoms in DMF to form a distorted octahedral coordination configuration. The bond lengths of the Ni-N bond and the Ni-O bond are and

[0070] The Ni(DMF)2[Ni(CN)4] prepared in Example 1 was subjected to phase analysis by X-ray diffractometer (XRD), and the results are shown in FIG7 . The crystal structure corresponding to FIG7 was simulated to obtain a simulation curve as shown in FIG7 . It was found that the peak position height of the Ni(DMF)2[Ni(CN)4] powder sample prepared in Test Example 1 was the same as that of the simulation curve, which indicates that the prepared powder sample has a single crystal structure.

[0071] Figure 8 is a Brunauer-Emmett-Teller (BET) specific surface area curve of Ni(DMF)2[Ni(CN)4] powder tested by nitrogen adsorption-desorption method. Its specific surface area is 59.7m 2 g -1 The pore size is mainly micropores below 2 nm, and the pore volume is 0.36 cm 3 g-1 , which indicates that it has a high specific surface area and has the potential to be used in the field of gas adsorption or gas screening.

[0072] Figure 9 is a thermogravimetric analysis diagram of the Ni(DMF)2[Ni2(CN)4] powder prepared in Example 1. Thermogravimetric testing was carried out in nitrogen. The results show that Ni(DMF)2[Ni2(CN)4] has a weight loss platform near 270°C, which corresponds to the loss of the organic ligand DMF molecule. After the loss of the organic ligand DMF molecule, the mass fraction is stable and the structural stability is maintained, indicating that the Ni(DMF)2[Ni2(CN)4] prepared by this preparation method has good stability.

[0073] Example 2

[0074] A composite solid electrolyte was prepared using Ni(DMF)2[Ni2(CN)4] prepared in step S3 of Example 1.

[0075] 0.2 g of Ni(H2O)2[Ni(CN)4] was added to 2 mL of DMF solvent and magnetically stirred at room temperature for 1 hour for ligand exchange reaction. After drying, a powder sample of Ni(DMF)2[Ni(CN)4] was obtained.

[0076] The PVDF-HFP polymer solid electrolyte matrix and lithium bis(fluorosulfonyl)imide were mixed and dissolved in a DMF organic polar solution under stirring at 80°C to obtain a mixed solution. The molar ratio of the polymer solid electrolyte matrix to the lithium salt was 1:4.

[0077] Ni(DMF)2[Ni(CN)4] powder was mixed with the mixed solution and stirred at room temperature for 8 hours until uniformly mixed.

[0078] A solution casting method is adopted and the mixture is dried at 60° C. for 4 to 12 hours to obtain a homogeneous composite solid electrolyte.

[0079] The prepared composite solid electrolyte can match the positive and negative electrode materials to assemble a solid-state battery for testing. Sulfurized polyacrylonitrile is used as the positive electrode material, lithium metal is used as the negative electrode material, and a polymer film containing Ni(DMF)2[Ni(CN)4] is used as the composite solid electrolyte. The test voltage range is 1.0-3.0V, and the current density is 0.2C (1C = 1675mA g -1 ), to test the cycle performance of solid-state batteries.

[0080] An optical photograph of the Ni(DMF)2[Ni(CN)4]-based composite solid electrolyte prepared in Example 2 is shown in FIG10 , which indicates that the composite polymer solid electrolyte containing an organic Hofmann-type two-dimensional material has good strength and flexibility, which is conducive to achieving better interface contact between the positive and negative electrodes.

[0081] The present application also conducted an ionic conductivity test on the Ni(DMF)2[Ni(CN)4]-based composite solid electrolyte, as shown in Figure 11. The AC impedance of the composite solid electrolyte was tested using a stainless steel symmetrical cell to obtain the ionic conductivity, which was 6.5×10 -4 S cm -1 The conductivity of the composite polymer solid electrolyte based on organic Hofmann-type two-dimensional materials can reach 10 -4 ~10 -3 S cm -1 This indicates that it is a solid electrolyte with high ionic conductivity at room temperature, which is expected to achieve a solid electrolyte design with higher ionic conductivity and higher safety. Moreover, since the solution casting process is relatively simple, it is suitable for large-scale preparation and production, which is conducive to promoting the practical application of such composite solid electrolytes.

[0082] Example 3

[0083] The difference from embodiment 1 lies in step S1.

[0084] The mixture was replaced with “0.95 g NiCl2·6H2O and 0.88 g sodium citrate dissolved in 40 mL water”, and the remaining conditions were the same as those in Example 1.

[0085] The prepared Co(DMF)2[Ni(CN)4] powder sample was observed by scanning electron microscopy, and the results are shown in Figure 12. The Co(DMF)2[Ni(CN)4] has a uniform structure, a distinct layered structure, a size of 1 to 2 μm, and no obvious impurity phase.

[0086] Example 4

[0087] The difference from embodiment 1 lies in step S1.

[0088] The mixture was replaced by “2.8 g NiCl2·6H2O and 2.64 g sodium citrate dissolved in 40 mL water”, and the remaining conditions were the same as those in Example 1.

[0089] The Ni(DMF)2[Ni(CN)4] powder sample prepared in Example 4 was observed under a scanning electron microscope, as shown in Figure 13. Compared to the powder sample prepared in Example 1 (see Figure 6), the Ni(DMF)2[Ni(CN)4] prepared in Example 4 exhibits fragmented structure, varying sizes, and slightly poor uniformity. This suggests that the molar ratio of metal salt to tetracyanometallate is too high, resulting in an inhomogeneous structure and morphology of the prepared two-dimensional material.

[0090] From the above, it can be seen that the present application provides a preparation and application for synthesizing a series of organic Hofmann-type two-dimensional materials. The preparation method has a short process and low cost, has high environmental advantages and economic benefits, and can be applied to large-scale batch synthesis. The prepared organic Hofmann-type two-dimensional material M1(L)2[M2(CN)4] has good stability, large pore size and specific surface area, and good ligand substitutability, and shows great application potential in the fields of gas adsorption, gas screening and composite solid electrolytes.

[0091] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent replacements of the technical solutions of the present invention should not depart from the spirit and scope of the technical solutions of the present invention.

Claims

1. An organic Hofmann-type two-dimensional material, characterized in that: The structural formula of the two-dimensional material is M1(L)2[M2(CN)4], wherein M1 includes at least one of Mn, Fe, Co, Ni, Cu or Zn, M2 includes at least one of Ni, Cu, Pd or Pt, and L includes at least one of N,N-dimethylformamide, dimethylacetamide or dimethyl sulfoxide.

2. The organic Hofmann-type two-dimensional material according to claim 1, characterized in that In M1(L)2[M2(CN)4], the mass percentage of L is 10wt% to 40wt%.

3. A method for preparing an organic Hofmann-type two-dimensional material, characterized in that: The preparation method comprises: Dissolving a tetracyanometallate in water to obtain a tetracyanometallate solution, wherein the tetracyanometallate contains a metal R and a metal M2, wherein R includes at least one of Na or K, and M2 includes at least one of Ni, Cu, Pd or Pt; Mixing a salt solution containing metal M1 with the tetracyanometallate solution, stirring, and obtaining a M1(H2O)2[M2(CN)4]·xH2O precursor, wherein M1 includes at least one of Mn, Fe, Co, Ni, Cu, or Zn; removing adsorbed water in the precursor to obtain M1(H2O)2[M2(CN)4]; M1(H2O)2[M2(CN)4] is mixed with an organic ligand solvent to undergo a ligand exchange reaction, and then dried to obtain M1(L)2[M2(CN)4], wherein L includes at least one of N,N-dimethylformamide, dimethylacetamide or dimethyl sulfoxide.

4. The preparation method according to claim 3, characterized in that: The salt solution containing the metal M1 comprises a metal salt and water, wherein the molar ratio of the metal salt to the tetracyanometallate is 1-5.

5. The preparation method according to claim 3, characterized in that: A dispersant is also added to the salt solution containing the metal M1, and the dispersant includes at least one of trisodium citrate dihydrate or polyvinyl pyrrolidone.

6. The preparation method according to claim 3, characterized in that: The anions in the salt solution containing the metal M1 include at least one of nitrate, sulfate, chloride or acetate.

7. The preparation method according to claim 3, characterized in that: The precursor is heated under vacuum at 100-110° C. to remove adsorbed water.

8. The preparation method according to claim 3, characterized in that: The solid-liquid ratio of M1(H2O)2[M2(CN)4] after mixing with the organic ligand solvent is 1:10 to 1:

100.

9. The preparation method according to claim 3, characterized in that: The process of mixing the salt solution containing the metal M1 with the tetracyanometallate solution comprises: dropping one of the salt solution containing the metal M1 and the tetracyanometallate solution into the other.

10. An application of the organic Hofmann-type two-dimensional material as claimed in claim 1 or 2 in the field of composite solid electrolytes and gas screening.

Images