A cobalt cluster-based supramolecular framework material, preparation method and application

Abstract

This invention provides a cobalt cluster-based supramolecular framework material, its preparation method, and its applications, relating to the technical field. The molecular formula of the cluster-based supramolecular framework material of this invention is [Co...]. II 12 Co III 8(HL) 12 ( m 3-OH) 24 ] 12+ (NO3 ‑ ) 12 In this context, HL is the ligand, and the structure is shown below. Cobalt cluster-based supramolecular framework materials have a tetragonal crystal structure. I 4 / m The space group and body-centered cubic (bcc) packing mode of the cobalt cluster-based supramolecular framework material of this invention are suitable for gas separation, especially for the separation of hydrogen and deuterium.

Description

Technical Field

[0001] This invention belongs to the technical field and relates to a cobalt cluster-based supramolecular framework material, its preparation method, and its application. Background Technology

[0002] Deuterium (D), as a core fuel for nuclear fusion energy, is also widely used in key fields such as isotope tracing, neutron scattering experiments, and nuclear medicine, showing broad application prospects. Deuterium is generally obtained through deuterium-hydrogen separation. Adsorption separation technology based on crystalline porous materials has become a research hotspot in the field of deuterium-hydrogen separation due to its advantages of low energy consumption, simple operation, and high separation efficiency. Among them, metal-organic frameworks (MOFs), covalent organic frameworks (COFs), and supramolecular assembly frameworks (SAFs) have shown great application potential in deuterium-hydrogen separation due to their designable structures, tunable pore sizes, and high specific surface areas. However, the kinetic diameter difference of deuterium-hydrogen molecules is only 0.016 Å, and its efficient separation depends on the material having a precise pore size of 3.0-3.4 Å to achieve selective diffusion of isotopes through the kinetic quantum sieving (KQS) effect. Therefore, achieving sub-angstrom-level fine control is a major challenge for using crystalline porous materials to separate deuterium-hydrogen. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a cobalt cluster-based supramolecular framework material, its preparation method, and its applications.

[0004] The technical solution of the present invention is as follows:

[0005] A cobalt cluster-based supramolecular framework material has the molecular formula shown in formula (1). [Co II 12 Co III 8(HL) 12 ( μ 3-OH) 24 ] 12+ (NO3 - ) 12 (1) Wherein, HL is a ligand, and its structure is shown in equation (2) below. (2) The cobalt cluster-based supramolecular framework material has a tetragonal crystal structure. I 4 / m The spatial group and body-centered cubic (bcc) stacking method.

[0007] Preferably, the tetragonal crystal system has a = 23.57 ± 11 Å, b = 23.57 ± 11 Å, c = 20.49 ± 14 Å, and α = β = γ.= 90°.

[0008] A method for preparing a cobalt cluster-based supramolecular framework material according to any of the above embodiments, wherein 1,2-diacetonitrile-4,5-difluorobenzene and cobalt nitrate hexahydrate are added to an organic solvent to form a mixed solution, and the mixed solution undergoes a solvothermal reaction to obtain the cobalt cluster-based supramolecular framework material; The organic solvent is composed of DMF, methanol and chloroform in a volume ratio of 1:2:1.

[0009] Preferably, the molar ratio of the 1,2-diacetonitrile-4,5-difluorobenzene to the cobalt nitrate hexahydrate is 1:1-1.2; The concentration of 1,2-diacetonitrile-4,5-difluorobenzene in the mixed solution is 0.05-0.14 mol / L.

[0010] More preferably, the molar ratio of the 1,2-diacetonitrile-4,5-difluorobenzene and the cobalt nitrate hexahydrate is 1:1.1-1.2.

[0011] Preferably, the temperature of the solvothermal reaction is 100-150℃ and the time is 3-10 days.

[0012] Preferably, the mixed solution also contains an organic base; The volume ratio of the organic base to the organic solvent is 0.003-0.008:1.

[0013] More preferably, the organic base is added after the 1,2-diacetonitrile-4,5-difluorobenzene, the cobalt nitrate hexahydrate, and the organic solvent are stirred at room temperature for 12-30 hours, and the mixed solution is in a clear state.

[0014] An application of the cobalt cluster-based supramolecular framework material described in any of the above embodiments in the field of gas separation.

[0015] Preferably, it is used for the separation of hydrogen and deuterium.

[0016] The beneficial effects of this invention are: (1) The organic ligand HL of the cobalt cluster-based supramolecular framework material of the present invention introduces fluorine functional groups. By utilizing the strong electronegativity and small atomic radius of fluorine, the channel polarity and H2 / D2 adsorption enthalpy difference are significantly enhanced without sacrificing porosity, thus achieving synergistic optimization of precise pore size (3.05 Å) and excellent deuterium-hydrogen separation performance.

[0017] (2) The cobalt cluster-based supramolecular framework material of the present invention has good stability: 1) The structure does not change after soaking in water for 48 h and in various organic solvents for 72 h. 2) The structure is intact in aqueous solutions with pH 2-12. 3) The structure remains intact after desolventization at 30-150℃. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the non-covalent intermolecular interactions of the cobalt cluster-based supramolecular framework material of the present invention.

[0019] Figure 2 The diagram shows the packing pattern and corresponding pore pattern of the cobalt cluster-based supramolecular framework material of the present invention along the a, b, and c axes.

[0020] Figure 3 The image shows the powder X-ray diffraction pattern of the cobalt cluster-based supramolecular framework material obtained in the example.

[0021] Figure 4 Comparison of powder X-ray diffraction results of the cobalt cluster-based supramolecular framework material obtained in the example after heat treatment and after being exposed to air for 2 months.

[0022] Figure 5 Comparison of powder X-ray diffraction results of the cobalt cluster-based supramolecular framework material obtained in the examples after treatment in acidic aqueous solution (pH=2), alkaline aqueous solution (pH=12), and water.

[0023] Figure 6 Comparison of powder X-ray diffraction results of cobalt cluster-based supramolecular framework materials obtained in the examples after being immersed in different organic solvents for 3 days.

[0024] Figure 7 Comparison of H2 and D2 adsorption isotherms (77 K) of the cobalt cluster-based supramolecular framework material obtained in the examples. Detailed Implementation

[0025] The technical solution of the present invention will be further explained and described below through specific embodiments.

[0026] On the one hand, this invention proposes a cobalt cluster-based supramolecular framework material having the molecular formula shown in formula (1). [Co II 12 Co III 8(HL) 12 ( μ 3-OH) 24 ] 12+ (NO3 - ) 12 (1) Wherein, HL is a ligand, and its structure is shown in equation (2) below. (2) Cobalt cluster-based supramolecular framework materials have a tetragonal crystal structure. I 4 / m The spatial group and body-centered cubic (bcc) stacking method.

[0028] The cobalt cluster-based supramolecular framework material of this invention uses a para-difluorinated 1,3-diiminoisoindoline derivative (as shown in formula (2) above) as a ligand. Fluorine atoms have the characteristics of strong electronegativity and small atomic radius. Without significantly changing the framework topology, it optimizes the pore space and enhances the pore polarity, maintaining or even increasing the porosity of the material. For the separation of hydrogen and deuterium, it can increase the adsorption enthalpy of deuterium and expand the adsorption enthalpy difference of H2 / D2 (Δ). Q st This enhances the driving force of CAQS separation (chemical affinity quantum sieving). (See attached image) Figure 1 This is a schematic diagram of the non-covalent intermolecular interactions of the cobalt cluster-based supramolecular framework material of the present invention. Adjacent clusters are synergistically connected through three types of non-covalent interactions: π···π stacking (3.68 Å), NH / CH···O hydrogen bonds (2.53-2.71 Å), and CF···O halogen bonds (2.13 Å). Each cluster unit is connected to eight surrounding adjacent clusters, exhibiting a stable bcc stacking structure. (See attached diagram.) Figure 2 The figures show the packing diagrams and corresponding pore diagrams of the cobalt cluster-based supramolecular framework material of the present invention along the a, b, and c axes. The pores are interconnected in the three directions. Figures (a) and (d) show the packing diagrams and corresponding pore diagrams along the a axis, Figures (b) and (e) show the packing diagrams and corresponding pore diagrams along the b axis, and Figures (c) and (f) show the packing diagrams and corresponding pore diagrams along the c axis.

[0029] In some embodiments, the tetragonal crystal system has a = 23.57 ± 11 Å, b = 23.57 ± 11 Å, c = 20.49 ± 14 Å, α = β = γ. = 90°. The cell volume of the cobalt cluster-based supramolecular framework material of this invention is 11394.60 ± 13 Å. 3 Table 1 below shows the pore characteristics of the cobalt cluster-based supramolecular framework material of the present invention.

[0030] Table 1

[0031] Table 2 below shows the nitrogen adsorption performance (77K) of the cobalt cluster-based supramolecular framework material of the present invention.

[0032] Table 2

[0033] On the other hand, the present invention also proposes a method for preparing the cobalt cluster-based supramolecular framework material according to any of the above embodiments, wherein 1,2-diacetonitrile-4,5-difluorobenzene and cobalt nitrate hexahydrate are added to an organic solvent to form a mixed solution, and the mixed solution undergoes a solvothermal reaction to obtain the cobalt cluster-based supramolecular framework material. The organic solvent is composed of DMF, methanol and chloroform in a volume ratio of 1:2:1.

[0034] This invention provides a method for preparing cobalt cluster-based supramolecular framework materials by using 1,2-diacenitrile-4,5-difluorobenzene and cobalt nitrate hexahydrate as reactants in a solvothermal reaction. During the solvothermal reaction, 1,2-diacenitrile-4,5-difluorobenzene undergoes cyclization to form a phthalocyanine intermediate. The phthalocyanine intermediate then decomposes to generate the ligand shown in formula (2) and a para-difluorophthalimide. The ligand and cobalt nitrate then coordinate and assemble to obtain the cobalt cluster-based supramolecular framework material.

[0035] In some embodiments, the molar ratio of 1,2-diacetonitrile-4,5-difluorobenzene to cobalt nitrate hexahydrate is 1:1-1.2; The concentration of 1,2-diacetonitrile-4,5-difluorobenzene in the mixed solution is 0.05-0.14 mol / L.

[0036] For example, the molar ratio of 1,2-diacetonitrile-4,5-difluorobenzene to cobalt nitrate hexahydrate can be 1:1, 1:1.02, 1:1.04, 1:1.05, 1:1.06, 1:1.08, 1:1.1, 1:1.12, 1:1.15, 1:1.16, 1:1.18, 1:1.2, etc. Further, the molar ratio of 1,2-diacetonitrile-4,5-difluorobenzene to cobalt nitrate hexahydrate is 1:1.1-1.2. For example, the concentration of 1,2-diacetonitrile-4,5-difluorobenzene in the mixed solution can be 0.05 mol / L, 0.06 mol / L, 0.07 mol / L, 0.08 mol / L, 0.09 mol / L, 0.1 mol / L, 0.11 mol / L, 0.12 mol / L, 0.13 mol / L, 0.14 mol / L, etc.

[0037] In some embodiments, the temperature of the solvothermal reaction is 100-150°C, and the time is 3-10 days. For example, the solvothermal reaction can be 100°C × 10 days, 110°C × 8 days, 110°C × 5 days, 120°C × 3 days, 130°C × 3 days, 150°C × 3 days, etc.

[0038] In some embodiments, the mixed solution also contains an organic base; The volume ratio of organic base to organic solvent is 0.003-0.008:1. Cobalt nitrate hexahydrate has low solubility in the above organic solvents; adding an organic base can improve its solubility. For example, the volume ratio of organic base to organic solvent can be 0.003:1, 0.004:1, 0.005:1, 0.006:1, 0.007:1, 0.008:1, etc., and the organic base can be triethylamine, triethanolamine, N-methyldiethylamine, etc.

[0039] In some embodiments, 1,2-diacenitrile-4,5-difluorobenzene, cobalt nitrate hexahydrate, and an organic solvent are stirred at room temperature for 12-30 hours before the organic base is added, resulting in a clear mixed solution. Stirring 1,2-diacenitrile-4,5-difluorobenzene, cobalt nitrate hexahydrate, and an organic solvent at room temperature for 12-30 hours promotes the dissolution of the reactants as much as possible before solvothermal heating.

[0040] Furthermore, the present invention also proposes an application of the cobalt cluster-based supramolecular framework material described in any of the above embodiments for use in the field of gas separation.

[0041] In some embodiments, it is used for the separation of hydrogen and deuterium.

[0042] As shown in Table 1 above, the pore confinement diameter (PLD) of the cobalt cluster-based supramolecular framework material of this invention is 3.05 Å, which falls precisely within the optimal pore size window (3.0-3.4 Å) for deuterium-hydrogen separation. The precise pore size is achieved through the synergistic spatial and electronic effects of the fluorine functional group of the ligand shown in Equation (2) – the fluorine atom has a small volume (van der Waals radius 1.47 Å), and after its introduction, it does not significantly compress the pores like large functional groups. Instead, it induces a more open pore structure through micro-adjustment of the framework, and the most probable pore size in NLDFT is 4.93 Å.

[0043] Meanwhile, the introduction of fluorine atoms in the ligand increases the adsorption enthalpy of D2 for the cobalt cluster-based supramolecular framework material of this invention. Q st (D2) reaches 8.80 kJ / mol, H2 / D2 adsorption enthalpy difference Δ Q st (Δ) Q st = Q st (D2) - Q stThe adsorption enthalpy (H2) reaches 0.80 kJ / mol, providing a strong thermodynamic driving force for efficient separation based on CAQS. Density functional theory (DFT) calculations show that D2 forms a quadruple hydrogen bond with four fluorine atoms in the pores of the cobalt cluster-based supramolecular framework material of this invention (D···F: 2.55-2.87 Å), while H2 forms only a triple hydrogen bond with three fluorine atoms (H···F: 2.77-2.91 Å). This differential binding mode is the microscopic source of the significantly increased adsorption enthalpy difference. The ideal adsorption solution theory (IAST, 77 K) reaches 1.61, indicating good separation performance in the breakthrough experiment.

[0044] The adsorption and separation performance of the cobalt cluster-based supramolecular framework material of the present invention for hydrogen / deuterium isotopes is shown in Table 3 below.

[0045] Table 3

[0046] The technical solution of the present invention will be further described and illustrated below with reference to various embodiments. Unless otherwise specified, the parts mentioned in the following embodiments are parts by weight.

[0047] Example 1 0.064 g of 1,2-diacenitrile-4,5-difluorobenzene (0.39 mmol) and 0.131 g of Co(NO3)3·6H2O (0.45 mmol) were added to 4 mL of a mixed solvent of DMF / CH3OH / CHCl3 (volume ratio 1:2:1). The mixture was stirred at room temperature for 24 hours, and then 0.02 mL of triethylamine was added. The mixture was stirred until the solution became clear. The solution was then transferred to a reaction vessel and heated at 110 °C for 5 days. After cooling to room temperature, the resulting red crystals were washed three times with anhydrous ethanol and dried under vacuum at 60 °C overnight to obtain a cobalt cluster-based supramolecular framework material. The yield was 65% based on 1,2-diacenitrile-4,5-difluorobenzene.

[0048] The powder X-ray diffraction (PXRD) results of the cobalt cluster-based supramolecular framework material obtained in this embodiment are attached. Figure 3 As shown.

[0049] The cobalt cluster-based supramolecular framework material obtained in this embodiment underwent heat treatment (453K, 24h) and PXRD comparisons after exposure to air for 2 months are shown in the attached figures. Figure 4 As shown, the cobalt cluster-based supramolecular framework material exhibits good thermal stability.

[0050] The PXRD comparisons of the cobalt cluster-based supramolecular framework material obtained in this embodiment after treatment in acidic aqueous solution (pH=2, soaking for 48 h), alkaline aqueous solution (pH=12, soaking for 48 h), and water (soaking for 48 h) are shown in the attached figures. Figure 5As shown, the cobalt cluster-based supramolecular framework material exhibits good acid, alkali, and water stability.

[0051] PXRD comparisons of the cobalt cluster-based supramolecular framework material obtained in this embodiment after immersion in different organic solvents for 3 days are shown in the attached figures. Figure 6 As shown, the cobalt cluster-based supramolecular framework material exhibits good stability in organic solvents.

[0052] Appendix Figure 7 Comparison of H2 and D2 adsorption isotherms (77 K) of the cobalt cluster-based supramolecular framework material obtained in this embodiment.

[0053] Example 2 0.074 g of 1,2-diacenitrile-4,5-difluorobenzene (0.45 mmol) and 0.131 g of Co(NO3)3·6H2O (0.45 mmol) were added to 4 mL of a mixed solvent of DMF / CH3OH / CHCl3 (volume ratio 1:2:1). The mixture was stirred at room temperature for 24 hours, and then 0.03 mL of triethylamine was added. The mixture was stirred until the solution became clear. The solution was then transferred to a reaction vessel and heated at 120 °C for 4 days. After cooling to room temperature, the resulting red crystals were washed three times with anhydrous ethanol and dried under vacuum at 60 °C overnight to obtain a cobalt cluster-based supramolecular framework material. The yield was 71% based on 1,2-diacenitrile-4,5-difluorobenzene.

[0054] As described above, the basic principles, main features, and advantages of the present invention have been shown and described. Those skilled in the art should understand that the present invention is not limited to the above embodiments, which are merely preferred embodiments and should not be construed as limiting the scope of the invention. All equivalent changes and modifications made in accordance with the scope of the patent and the description should still fall within the scope of the present invention. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A cobalt cluster-based supramolecular framework material, characterized in that, It has the molecular formula shown in equation (1) below. [What II 12 What III 8(HL) 12 ( μ 3-OH) 24 ] 12+ (NO3 - ) 12 (1) Wherein, HL is a ligand, and its structure is shown in equation (2) below. （2） The cobalt cluster-based supramolecular framework material has a tetragonal crystal structure. I 4 / m The spatial group and body-centered cubic (bcc) stacking method.

2. The cobalt cluster-based supramolecular framework material according to claim 1, characterized in that, The tetragonal crystal system has a = 23.57 ± 11 Å, b = 23.57 ± 11 Å, c = 20.49 ± 14 Å, α = β = γ = 90°.

3. A method for preparing a cobalt cluster-based supramolecular framework material as described in claim 1 or 2, characterized in that, 1,2-Dianitrile-4,5-difluorobenzene and cobalt nitrate hexahydrate are added to an organic solvent to form a mixed solution, and the mixed solution undergoes a solvothermal reaction to obtain the cobalt cluster-based supramolecular framework material; The organic solvent is composed of DMF, methanol and chloroform in a volume ratio of 1:2:

1.

4. The method for preparing the cobalt cluster-based supramolecular framework material according to claim 3, characterized in that, The molar ratio of the 1,2-diacetonitrile-4,5-difluorobenzene to the cobalt nitrate hexahydrate is 1:1-1.2; The concentration of 1,2-diacetonitrile-4,5-difluorobenzene in the mixed solution is 0.05-0.14 mol / L.

5. The method for preparing the cobalt cluster-based supramolecular framework material according to claim 4, characterized in that, The molar ratio of the 1,2-diacetonitrile-4,5-difluorobenzene to the cobalt nitrate hexahydrate is 1:1.1-1.

2.

6. The method for preparing the cobalt cluster-based supramolecular framework material according to claim 3, characterized in that, The solvothermal reaction is carried out at a temperature of 100-150℃ for 3-10 days.

7. The method for preparing the cobalt cluster-based supramolecular framework material according to claim 3, characterized in that, The mixed solution also contains organic bases; The volume ratio of the organic base to the organic solvent is 0.003-0.008:

1.

8. The method for preparing the cobalt cluster-based supramolecular framework material according to claim 7, characterized in that, The 1,2-diacetonitrile-4,5-difluorobenzene, the cobalt nitrate hexahydrate, and the organic solvent were stirred at room temperature for 12-30 hours before the organic base was added, and the mixed solution was in a clear state.

9. An application of the cobalt cluster-based supramolecular framework material according to claim 1 or 2, characterized in that, Used in the field of gas separation.

10. The application of the cobalt cluster-based supramolecular framework material according to claim 9, characterized in that, Used for the separation of hydrogen and deuterium.

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