A quasicrystal-like metal organic framework and its preparation method and application

Abstract

The present invention discloses a quasi-crystal metal organic framework and a preparation method thereof and an application in the field of gas adsorption. The present invention synthesizes a quasi-crystal metal organic framework with pentagonal mosaic by using multi-linked carboxylic acid ligands, and the framework structure has certain stability and porosity. Gas adsorption experiments show that the quasi-crystal metal organic framework mcm-MOF-1 of the present invention has certain adsorption properties for different gases. The maximum adsorption capacity of nitrogen at 77K is 110cm 3 g ‑1 The maximum adsorption capacity of CO2 at 195K is 100cm 3 g ‑1 At room temperature, the adsorption capacity of methane is 8cm 3 g ‑1 The adsorption capacity of sulfur hexafluoride is 18 cm 3 g ‑1 .

Description

Technical Field

[0001] The present invention relates to the technical field of porous materials, and in particular to a quasicrystal-like metal organic framework and a preparation method and application thereof. Background Art

[0002] Quasicrystals are solids between crystals and amorphous solids. They have a long-range ordered atomic arrangement similar to that of crystals, but lack the translational symmetry of crystals. Therefore, they can have macroscopic symmetry that is not allowed by crystals. Since quasicrystals usually have poor electrical and thermal conductivity, they have potential applications in fields such as thermal insulation materials and light-emitting diodes. In addition, despite their poor thermal conductivity, they can be used as ideal thermoelectric materials because they can convert heat into electricity. However, quasicrystals are very rare in nature, and it is difficult to study and analyze the structure of quasicrystals. Fortunately, researchers have been able to use chemical methods to prepare quasi-crystal-like materials with similar structures and properties to quasicrystals, making them an important part of optical, electronic and magnetic research.

[0003] The quasicrystals reported so far are mainly concentrated in metal alloys and are still relatively rare in metal-organic complexes. Recently, researchers have reported some triangular and quadrilateral mosaic quasicrystal metal-organic frameworks. For example, Rogers et al. (Science Advances, 2020, 6:eaay7685) used ionic liquids to synthesize the first 3 2 .4.3.4 Embedded two-dimensional layered compounds. Pedersen et al. (Nature Communications, 2020, 11: 4705) used rare earth ions to synthesize 3 3 .4 2 The embedded two-dimensional solid further proves the possibility of observing quasicrystalline phases in metal-organic coordination compounds. However, these reported compounds usually connect metal ions through nitrogen atoms, resulting in poor stability of such compounds, further limiting their application value. According to the theory of hard and soft acids and bases, carboxylic acid ligands usually form stronger coordination bonds with metal ions, which is conducive to obtaining more stable complex structures. Therefore, the design and synthesis of carboxylic acid-connected quasicrystalline metal-organic frameworks is of great significance.

[0004] The present invention uses polycarboxylic acid ligands as linkers and introduces metal ions to synthesize a novel pentagonal mosaic quasicrystal-like metal organic framework. In addition, the framework structure has higher stability than previous quasicrystal-like compounds, prompting us to further explore its adsorption performance for different gases. Summary of the invention

[0005] The present invention provides a quasicrystal-like metal organic framework with novel structure, relative stability and convenient synthesis, a preparation method thereof and an application thereof in gas adsorption.

[0006] The specific technical solutions are as follows:

[0007] A quasicrystal-like metal-organic framework with a two-dimensional layered structure of pentagonal tessellations as shown below:

[0008]

[0009] in:

[0010] L represents a hexacarboxy caged oxacalixarene anion C having the following molecular structure 69 H 33 N 3 O 18 6- :

[0011]

[0012] M stands for Cu 2+ The Cu 2 Wheel paddle structure Cu 2 (COO) 4 :

[0013]

[0014] In other words, in the molecular structure of the quasi-crystalline metal organic framework described in the present invention, the Cu 2 The unit is connected to four carboxyl groups from four hexacarboxyl cage-like oxacalixarene anions, and extends alternately in the two-dimensional direction to form a two-dimensional layered structure with pentagons.

[0015] The present invention also provides a method for preparing the quasicrystal-like metal organic framework, comprising the following steps:

[0016] (1) mixing a copper ion source, a ligand hexacarboxylic acid caged oxacalixarene, a solvent N,N-dimethylformamide and nitric acid to obtain a reaction solution;

[0017] (2) sealing the reaction container containing the reaction solution and reacting it at 60-100° C., washing the solid after the reaction is completed, and vacuum drying to obtain the quasicrystal-like metal organic framework.

[0018] In step (1), the mass ratio of the copper ion source to the ligand hexacarboxylic acid caged oxacalixarene can be 2:(0.5-2).

[0019] In one embodiment, in step (1), the nitric acid is added in the form of a nitric acid N,N-dimethylformamide solution, the volume ratio of the solvent N,N-dimethylformamide to the nitric acid N,N-dimethylformamide solution is (5-30):1, and the HNO 3 The concentration is 3~3.5mol / L.

[0020] In the method for preparing the quasicrystal-like metal organic framework, in step (1), the concentration of the copper ion source in the reaction solution can be 1 to 20 mg / mL.

[0021] In the method for preparing the quasicrystal-like metal organic framework, in step (1), the copper ion source can be copper nitrate hexahydrate.

[0022] In the method for preparing the quasi-crystalline metal organic framework, in step (1), the ligand hexacarboxylic acid cage-shaped oxacalixarene has the structure shown below:

[0023]

[0024] The ligand hexacarboxylic acid caged oxacalixarene can be prepared according to the existing technology, for example, reference can be made to the inventor's prior research results: Chinese patent application "A fluorescent molecule based on caged oxacalixarene and its preparation method and application" (patent application number: CN202211267712.0).

[0025] In the method for preparing the quasicrystal-like metal organic framework, in step (2), the reaction time can be 1 to 3 days.

[0026] In one embodiment, in step (2), the washing specifically comprises: washing the solid with N,N-dimethylformamide and acetone in sequence.

[0027] The present invention also provides application of the quasicrystal-like metal organic framework in the field of gas adsorption.

[0028] The quasi-crystal-like metal organic framework described in the present invention can be used to adsorb gases such as nitrogen, carbon dioxide, methane, and sulfur hexafluoride.

[0029] Specifically, the maximum adsorption capacity of nitrogen by the quasi-crystalline metal organic framework described in the present invention at low temperature (77K) is 110 cm 3 g -1 (Relative pressure p / p 0 =0.9), the specific surface area reaches 320m 2 g -1 . CO at low temperature (195K) 2 The maximum adsorption capacity is 100 cm 3 g -1(Relative pressure p / p 0 =0.9). In addition, the quasi-crystalline metal organic framework also has a certain adsorption capacity for natural gas and greenhouse gases. For example, at room temperature, the adsorption capacity of methane by the quasi-crystalline metal organic framework of the present invention is 8 cm 3 g -1 The adsorption capacity of sulfur hexafluoride is 18 cm 3 g -1 .

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. The present invention utilizes hexacarboxylic acid cage-like oxacalixarene as a linker to bind metal copper ions, laying a foundation for the exploration and synthesis of supramolecular metal-organic frameworks.

[0032] 2. The present invention creatively synthesizes a quasicrystal-like metal-organic framework connected by polycarboxylic acids, which forms a quasicrystal-like two-dimensional layered structure through pentagonal tiling.

[0033] 3. The quasi-crystal-like metal organic framework provided by the present invention has a microporous structure and exhibits adsorption performance for different gases. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0035] Figure 1 Schematic diagram of the ball-and-stick model structure of the quasicrystal-like metal-organic framework prepared in Example 1.

[0036] Figure 2 This is the X-ray powder diffraction pattern of the quasicrystal-like metal-organic framework prepared in Example 1.

[0037] Figure 3 This is a scanning electron microscope photograph of the quasicrystal-like metal organic framework prepared in Example 1.

[0038] Figure 4 This is a nitrogen adsorption-desorption isotherm of the quasicrystal-like metal-organic framework prepared in Example 1.

[0039] Figure 5 This is a graph showing the carbon dioxide adsorption-desorption isotherm of the quasicrystal-like metal organic framework prepared in Example 1.

[0040] Figure 6 This is the methane adsorption-desorption isotherm of the quasicrystal-like metal-organic framework prepared in Example 1.

[0041] Figure 7 This is the sulfur hexafluoride adsorption-desorption isotherm curve of the quasicrystal-like metal organic framework prepared in Example 1. DETAILED DESCRIPTION

[0042] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0043] The operating methods in the following examples without specifying specific conditions are usually carried out under conventional conditions or conditions recommended by the manufacturers.

[0044] In the following embodiment 1:

[0045] The hexacarboxylic acid caged oxacalixarene was prepared with reference to the inventor's prior research results, namely the Chinese patent application "A fluorescent molecule based on caged oxacalixarene and its preparation method and application" (patent application number: CN202211267712.0);

[0046] The nitric acid N,N-dimethylformamide solution is prepared by adding concentrated nitric acid dropwise into N,N-dimethylformamide.

[0047] Example 1

[0048] Copper nitrate hexahydrate (40 mg) and hexacarboxylic acid caged oxacalixarene (20 mg) were added to a 15 mL glass bottle, and N,N-dimethylformamide (4 mL) was added. After ultrasonic dispersion, 0.2 mL HNO 3 A 3.5 mol / L nitric acid N,N-dimethylformamide solution was prepared. The glass bottle was sealed and placed in an 80°C forced air drying oven for 2 days, then taken out and cooled to room temperature. The supernatant was removed and washed with 12 mL of N,N-dimethylformamide and 12 mL of ethanol in turn to obtain a blue crystalline solid, which is the quasi-crystalline metal organic framework of the present invention, denoted as mcm-MOF-1.

[0049] The obtained blue crystalline solid was characterized by the ball-and-stick model structure. Figure 1 The X-ray powder diffraction results are shown in Figure 2 The scanning electron microscopy results are shown in Figure 3 shown.

[0050] Example 2

[0051] The gas adsorption performance of the quasicrystal-like metal organic framework obtained in Example 1 was tested.

[0052] The specific steps include:

[0053] (a) The quasi-crystalline metal organic framework synthesized in Example 1 was washed with 10 mL of acetone and then immersed in 5 mL of acetone for three days, with the acetone being replaced every 12 hours. The blue solid with acetone was added to an adsorption tube, the acetone was gradually blown dry with nitrogen, and then dried under vacuum at room temperature for 6 hours to obtain an activated sample.

[0054] (b) The activated sample was transferred to the adsorption instrument, and the adsorption-desorption curve of carbon dioxide was measured at a low temperature of 195K; the elution-desorption curve of nitrogen was measured at a low temperature of 77K.

[0055] The experimental results are as follows Figure 4 and Figure 5 As shown. Figure 4 It can be seen that the maximum adsorption capacity of nitrogen by the quasicrystal-like metal organic framework mcm-MOF-1 at 77K is 110 cm 3 g -1 (Relative pressure p / p 0 =0.9), the specific surface area reaches 320m 2 g -1 .Depend on Figure 5 It can be seen that the quasicrystal-like metal organic framework mcm-MOF-1 has a CO 2 The maximum adsorption capacity is 100 cm 3 g -1 These results indicate that this type of quasicrystal MOF has certain stability and porosity and has potential for gas adsorption applications.

[0056] Example 3

[0057] The activation was carried out in the manner of Example 2, and the activated sample was transferred to the adsorption instrument to measure the adsorption performance of mcm-MOF-1 on natural gas and greenhouse gases at different temperatures. The results showed that this type of quasicrystalline metal organic framework also has a certain adsorption capacity for natural gas and greenhouse gases. Figure 6 , Figure 7 At room temperature, the adsorption capacity of methane by the quasi-crystalline metal organic framework of the present invention is 8 cm 3 g -1 The adsorption capacity of sulfur hexafluoride is 18 cm 3 g -1 .

[0058] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A quasicrystal-like metal-organic framework, characterized in that: A two-dimensional layered structure with pentagonal tessellation as shown below: in: L represents a hexacarboxy caged oxacalixarene anion C having the following molecular structure 69 H 33 N3O 18 6- : M stands for Cu 2+ The Cu2 wheel-paddle structure Cu2(COO)4 is formed by connecting with the carboxyl group in the hexacarboxyl cage-like oxacalixarene anion: The method for preparing the quasicrystal-like metal organic framework comprises the following steps: (1) mixing a copper ion source, a ligand hexacarboxylic acid caged oxacalixarene, a solvent N,N-dimethylformamide and nitric acid to obtain a reaction solution; (2) sealing the reaction container containing the reaction solution and reacting it at 60-100° C., washing the solid after the reaction is completed, and vacuum drying to obtain the quasicrystal-like metal organic framework.

2. The method for preparing a quasicrystal-like metal organic framework according to claim 1, characterized in that: The following steps are involved: (1) mixing a copper ion source, a ligand hexacarboxylic acid caged oxacalixarene, a solvent N,N-dimethylformamide and nitric acid to obtain a reaction solution; (2) sealing the reaction container containing the reaction solution and reacting it at 60-100° C., washing the solid after the reaction is completed, and vacuum drying to obtain the quasicrystal-like metal organic framework.

3. The preparation method according to claim 2, characterized in that: In step (1), the mass ratio of the copper ion source to the ligand hexacarboxylic acid caged oxacalixarene is 2:(0.5-2).

4. The preparation method according to claim 2, characterized in that: In step (1), the nitric acid is added in the form of a nitric acid N,N-dimethylformamide solution, the volume ratio of the solvent N,N-dimethylformamide to the nitric acid N,N-dimethylformamide solution is (5-30):1, and the concentration of HNO3 in the nitric acid N,N-dimethylformamide solution is 3-3.5 mol / L.

5. The preparation method according to claim 2, characterized in that: In step (1), the concentration of the copper ion source in the reaction solution is 1 to 20 mg / mL.

6. The preparation method according to claim 2, characterized in that: In step (1), the copper ion source is copper nitrate hexahydrate.

7. The preparation method according to claim 2, characterized in that: In step (2), the reaction time is 1 to 3 days.

8. The preparation method according to claim 2, characterized in that: In step (2), the washing specifically comprises: washing the solid with N,N-dimethylformamide and acetone in sequence.

9. Use of the quasicrystal-like metal organic framework according to claim 1 in the field of gas adsorption.

10. The use according to claim 9, characterized in that: The quasi-crystal metal organic framework is used for adsorbing nitrogen, carbon dioxide, methane and sulfur hexafluoride.

Images