Double-interpenetrating MOF (Metal Organic Framework), preparation method thereof and application of double-interpenetrating MOF in acetylene purification

Abstract

The invention relates to the field of acetylene purification and new materials, and particularly provides a double-interspersed MOF (Metal Organic Framework) and a preparation method and application thereof in acetylene purification, and the specific synthesis method comprises the following steps: reacting a tricarboxylic acid ligand 1, 3, 5-tris (4-carboxylphenyl) benzene (H3btb) with a nitrogen-containing methyl-containing ligand 3-methyl-1H-1, 2, 3, 4-tetramethyl-1, 3, 4-tetramethyl-1, 3, 4-tetramethyl-1, 3, 4-tetramethyl-1, 3, 4-tetramethyl-1, 3, 4-tetramethyl-1, 3-tetramethyl-1 The MOF (Zn-btb-fmtrz) with ultrahigh stability performance is synthesized from 2, 3, 4-triazole (fmtrz) and a zinc-containing compound, and the material can be used as an adsorbent, has strong acetylene adsorption action force, high selectivity and good stability, is suitable for industrial production, and shows a more excellent separation effect on low-concentration acetylene compared with a traditional method. The synthesized material is stable and has good acetylene adsorption capacity, and a new direction is provided for using MOF as an acetylene purification material.

Description

Technical Field

[0001] The present invention relates to the fields of new compounds, new materials and acetylene purification, and in particular to a doubly intercalated MOF and a preparation method thereof and application in acetylene purification. Background Art

[0002] Acetylene (C2H2) and ethylene (C2H4) are important chemical raw materials and energy fuel gases, widely used in the production of rubber, resins, fibers, and plastics. C2H4 is primarily produced during steam cracking, typically coexisting with approximately 1% C2H2. During ethylene polymerization, the presence of 45 ppm of acetylene can lead to catalyst deactivation, limiting catalyst recovery. Furthermore, in the production of acetylene via partial combustion of natural gas or thermal cracking of hydrocarbons, a certain concentration of carbon dioxide (CO2) is always present as an impurity, typically between 3.2% and 3.5%. Therefore, selective separation and purification of C2H2 from C2H2 / C2H4 or C2H2 / CO2 mixtures is of great importance. However, due to the close similarity of C2H2's molecular size and physicochemical properties to those of C2H4 and CO2, acetylene purification remains a significant challenge.

[0003] Compared to traditional separation techniques such as cryogenic distillation, solvent extraction, and chemical reactions, physical separation using porous materials can improve energy efficiency and environmental sustainability. Among various adsorbents, metal-organic frameworks (MOFs) have shown great potential for gas adsorption separation in recent years due to their highly ordered pore structures, tunable pore sizes, and rich functional pore surfaces. Several MOFs have been reported for the separation of C2H2 / C2H4 and C2H2 / CO2. However, due to the inherent trade-off between adsorption capacity and selectivity, as well as structural instability, MOFs have not been practically applied as adsorbents in separation processes.

[0004] Therefore, how to obtain a C2H2 adsorbent with high adsorption capacity and selectivity as well as high structural stability is an urgent problem to be solved in this field. Summary of the Invention

[0005] To address the inherent trade-off between adsorption capacity and selectivity, as well as structural instability, in existing acetylene-selective adsorbents, this paper presents a doubly intercalated MOF, its preparation method, and its application in acetylene purification. Specifically, the synthesis method combines the tricarboxylic acid ligand 1,3,5-tris(4-carboxyphenyl)benzene (H3btb), the nitrogen- and methyl-containing ligand 3-methyl-1H-1,2,4-triazole (fmtrz), and a zinc-containing compound to create an ultra-stable MOF (Zn-btb-fmtrz). This material can be used as an adsorbent, exhibiting strong acetylene adsorption, high selectivity, and excellent stability, making it suitable for industrial production and exhibiting superior separation efficiency for low-concentration acetylene compared to conventional methods. The material synthesized in this paper is both stable and has excellent acetylene adsorption capacity, thus providing a new direction for the use of MOFs as acetylene purification materials.

[0006] The present invention provides a doubly intercalated MOF (Zn-btb-fmtrz) having a doubly intercalated structure, a molecular formula of [Zn4(H2O)2(fmtrz)2(btb)2(DMA)]·2DMA, a relative molecular mass of 1589.81, and colorless, transparent block crystals, wherein Zn represents a divalent zinc ion, H2O represents a water molecule, fmtrz represents 3-methyl-1H-1, 2, 4-triazole, btb represents deprotonated 1, 3, 5-tris(4-carboxyphenyl)benzenecarboxylic acid, and DMA represents N,N-dimethylacetamide.

[0007] MOF (Zn-btb-fmtrz) in the triclinic system It crystallizes in the space group and presents a two-fold interpenetrating three-dimensional framework structure. Specifically, the basic asymmetric unit of MOF (Zn-btb-fmtrz) consists of four independent Zn 2+ ions, two deprotonated btb 3- ligand, two fmtrz ligands, one coordinated DMA molecule, two coordinated water molecules and two free DMA. Four independent Zn 2+The ions have different coordination environments. Zn1 is coordinated with two oxygen atoms from the carboxylic acid ligand, two nitrogen atoms from the azole ligand, and one oxygen atom from the DMA molecule. Zn2 is connected to four oxygen atoms of the carboxylic acid ligand and one nitrogen atom of the azole ligand, two of which are from the same carboxylic acid ligand and the other two are from two different carboxylic acid ligands. Zn3 is connected to two oxygen atoms of the carboxylic acid ligand, one nitrogen atom of the azole ligand, and two oxygen atoms of water molecules. Zn4 is coordinated with four oxygen atoms of the carboxylic acid ligand and two nitrogen atoms of the azole ligand. The unit cell parameters are: axis length a = 14.8203(6) Å, b = 16.7360(8) Å, c = 18.2865(9) Å, α = 67.072(2)°, β = 71.819(2)°, γ = 87.068(2)°; the unit cell volume is V = 3955.9(3) Å 3 ; Z=2.

[0008] The rhombic pore size of MOF (Zn-btb-fmtrz) is 9.3 Å × 18.5 Å, and the larger pore size is conducive to the entry of guest gas molecules. In addition, the DMA guest molecules coordinated with MOF (Zn-btb-fmtrz) are easily removed after activation, resulting in the partial removal of Zn 2+ It becomes unsaturated in the coordination environment. This modification not only increases the pore size but also provides more adsorption sites for the guest molecule acetylene. The btb ligand contains numerous oxygen atoms, and the fmtrz contains nitrogen atoms and methyl functional groups. The N / O sites can produce stronger interactions with acetylene, making the MOF (Zn-btb-fmtrz) exhibit good acetylene adsorption performance.

[0009] The present invention further provides a method for preparing the highly stable doubly intercalated MOF (Zn-btb-fmtrz), which specifically comprises the following steps: (1) Weigh the H3btb ligand and the fmtrz ligand into a reaction vessel, add the solvent N,N-dimethylacetamide (DMA), and stir until dissolved; (2) preparing an aqueous solution of a zinc-containing compound, namely, weighing the zinc-containing compound, adding it to deionized water, and stirring until it dissolves; (3) The N,N-dimethylacetamide solution of the ligand and the aqueous solution containing the zinc compound are mixed, and after stirring evenly, the resulting solution is sealed, subjected to high-temperature hydrothermal reaction, washed, and dried to obtain MOF (Zn-btb-fmtrz).

[0010] Furthermore, the zinc-containing compound is zinc nitrate.

[0011] Furthermore, the molar ratio of the zinc-containing compound to the ligand fmtrz is 1:1-5:1, and the molar ratio of the two ligands H3btb and fmtrz is 1:1-1:5.

[0012] Furthermore, every 0.02 mmol of H3btb corresponded to 1.5 mL of DMA, and every 0.2 mmol of zinc nitrate corresponded to 1.5 mL of H2O.

[0013] Furthermore, the high-temperature hydrothermal reaction temperature is controlled at 90-110° C. and the reaction time is 24-48 h to control the nucleation and growth rates of the crystals.

[0014] Furthermore, the washing operation is to use DMA and H2O for washing three times respectively; the drying condition is to place it in a vacuum drying oven at 60°C and dry it for 24 hours.

[0015] The MOF (Zn-btb-fmtrz) prepared above does not require solvent exchange and can be used for acetylene purification after degassing and activation under vacuum at 160°C for 12 h. The specific steps are as follows: 1) A mixed gas containing acetylene is passed through a container filled with the prepared MOF (Zn-btb-fmtrz) at a certain temperature and pressure to complete the adsorption of acetylene; 2) The MOF (Zn-btb-fmtrz) was desorbed and regenerated by inert gas purge at room temperature to obtain high-purity acetylene.

[0016] Furthermore, the mixed gas is acetylene and separation gas, and the separation gas includes one of ethylene and carbon dioxide; the volume fraction of acetylene in the mixed gas is greater than 0 and less than or equal to 50%.

[0017] Furthermore, when acetylene is adsorbed on MOF (Zn-btb-fmtrz), the adsorption temperature is 0-25 °C, the pressure in the container is 100 kPa or above, and the reaction space velocity is 5-100 h -1 The amount of MOF (Zn-btb-fmtrz) used for each mixed gas with a flow rate of 2 mL / min is ≥1 g.

[0018] Furthermore, the inert gas is one of helium and argon, and the purge rate is 15 mL / min.

[0019] The doubly intercalated MOF (Zn-btb-fmtrz) prepared in this invention allows for simple acetylene purification procedures, and the purity of the acetylene product gas obtained after adsorption separation can exceed 90%. When the product gas needs to be recovered, it can be desorbed from the adsorbent by vacuuming. When recovery is no longer necessary, the adsorbent can be regenerated by purging with an inert gas at room temperature.

[0020] Compared with the prior art, the present invention has the following beneficial effects: (1) Compared with traditional adsorption materials, the highly stable doubly intercalated MOF (Zn-btb-fmtrz) prepared by the present invention uses tricarboxylic acid and nitrogen-containing methyl-containing dual ligands to construct a doubly intercalated structure with a rhombic pore size of 9.3 Å × 18.5 Å. The larger pore size is conducive to the entry of guest gas molecules. In addition, the DMA guest molecules coordinated with MOF (Zn-btb-fmtrz) are easily removed after activation, resulting in the partial removal of Zn 2+ It becomes unsaturated in the coordination environment. This modification not only increases the pore size but also provides more adsorption sites for the guest molecule acetylene. The btb ligand contains numerous oxygen atoms, and the fmtrz contains nitrogen atoms and methyl functional groups. The N / O sites can produce stronger interactions with acetylene, making the MOF (Zn-btb-fmtrz) exhibit good acetylene adsorption performance.

[0021] (2) Compared with traditional MOF adsorbent materials, the highly stable doubly intercalated MOF (Zn-btb-fmtrz) prepared in the present invention exhibits better water, acid, alkali and thermal stability due to the intercalation interlocking effect. It does not require solvent exchange and can be used for acetylene purification after direct activation. It is a preferred acetylene purification adsorbent.

[0022] (3) The acetylene purification method provided by the present invention uses a doubly intercalated MOF (Zn-btb-fmtrz) prepared with a dual ligand, which can simultaneously achieve efficient separation of ethylene / acetylene and acetylene / carbon dioxide, realize the purification of acetylene, and desorb at room temperature to obtain high-purity acetylene product gas.

[0023] In summary, this invention has prepared a doubly intercalated MOF (Zn-btb-fmtrz) and applied it to acetylene purification. This material exhibits strong acetylene adsorption, high selectivity, and excellent stability, making it suitable for industrial production. It demonstrates superior separation efficiency for low-concentration acetylene compared to traditional methods. The material synthesized in this invention is both stable and exhibits excellent acetylene adsorption capacity, providing a new avenue for the use of MOFs as acetylene purification materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the structure of the MOF (Zn-btb-fmtrz) material prepared in Example 1 (a is the minimum structural unit diagram, b is a schematic diagram of the secondary building unit, and c is a schematic diagram of the coordination situation); Figure 2 A schematic diagram of the structure of the MOF (Zn-btb-fmtrz) material prepared in Example 1 (a is a schematic diagram of the structure, b is a schematic diagram of the interlaced structure) Figure 3 A comparison diagram of the single crystal X-ray simulation image and the powder X-ray image of the MOF (Zn-btb-fmtrz) material prepared in Example 1; Figure 4 This is a graph showing the acid-base stability test of the MOF (Zn-btb-fmtrz) prepared in Example 1; Figure 5 This is a thermal stability test diagram of the MOF (Zn-btb-fmtrz) prepared in Example 1; Figure 6 This is the nitrogen adsorption-desorption curve of the MOF (Zn-btb-fmtrz) prepared in Example 1 at 77 K; Figure 7 Adsorption curves of acetylene, ethylene, and carbon dioxide by the MOF (Zn-btb-fmtrz) material prepared in Example 1 at standard pressure of 298 K; Figure 8 This is the multiple cycle adsorption curve of acetylene by the MOF (Zn-btb-fmtrz) material prepared in Example 1; Figure 9 These are the breakthrough curves of the MOF (Zn-btb-fmtrz) material prepared in Example 1 for different ratios of acetylene / ethylene and acetylene / carbon dioxide at room temperature. DETAILED DESCRIPTION

[0025] The technical solution of the present invention will be further described below in conjunction with specific embodiments. These embodiments are only used to illustrate the technical solution of the present invention in more detail and should not be construed as limiting the scope of protection of the present invention.

[0026] Unless otherwise specified, the test methods described in the examples are all conventional methods; the instruments and materials described are all commercially available unless otherwise specified.

[0027] Example 1 Preparation method of a doubly intercalated MOF (Zn-btb-fmtrz) (1) Weigh 8.8 mg (0.02 mmol) of H3btb ligand and 8.3 mg (0.1 mmol) of fmtrz ligand into a glass vial, add 1.5 mL of N,N-dimethylacetamide (DMA) solution, and stir until dissolved; (2) Weigh 60.0 mg (0.2 mmol) of zinc nitrate hexahydrate, add 1.5 mL of deionized water, and stir until dissolved. (3) The DMA solution of the ligand and the aqueous solution of zinc nitrate hexahydrate were mixed and stirred evenly. The resulting solution was sealed and reacted at 90°C for 48 h. The solution was filtered, washed three times with DMA and H2O, respectively, and dried in a vacuum drying oven at 60°C for 24 h to obtain MOF (Zn-btb-fmtrz) with a yield of 64.7% (based on H3btb).

[0028] Example 2 Preparation method of a doubly intercalated MOF (Zn-btb-fmtrz) (1) Weigh 8.8 mg (0.02 mmol) of H3btb ligand and 8.3 mg (0.1 mmol) of fmtrz ligand into a glass vial, add 1.5 mL of N,N-dimethylacetamide (DMA) solution, and stir until dissolved; (2) Weigh 60.0 mg (0.2 mmol) of zinc nitrate hexahydrate, add 1.5 mL of deionized water, and stir until dissolved. (3) The DMA solution of the ligand and the aqueous solution of zinc nitrate hexahydrate were mixed and stirred evenly. The resulting solution was sealed and reacted at 100°C for 48 h. The solution was filtered and then washed and dried using the same method as in Example 1 to obtain MOF (Zn-btb-fmtrz) with a yield of 75.3% (based on H3btb).

[0029] Example 3 Preparation method of a doubly intercalated MOF (Zn-btb-fmtrz) (1) Weigh 8.8 mg (0.02 mmol) of H3btb ligand and 8.3 mg (0.1 mmol) of fmtrz ligand into a glass bottle, add 1.5 mL of N,N-dimethylacetamide (DMA) solution, and stir until dissolved; (2) Weigh 60.0 mg (0.2 mmol) of zinc nitrate hexahydrate, add 1.5 mL of deionized water, and stir until dissolved. (3) The DMA solution of the ligand and the aqueous solution of zinc nitrate hexahydrate were mixed and stirred evenly. The resulting solution was sealed and reacted at 110°C for 48 h. The solution was filtered and then washed and dried using the same method as in Example 1 to obtain MOF (Zn-btb-fmtrz) with a yield of 80.2% (based on H3btb).

[0030] Example 4 Preparation Method of a Double Intercalated MOF (Zn-btb-fmtrz) (1) Weigh 8.8 mg (0.02 mmol) of H3btb ligand and 5.8 mg (0.07 mmol) of fmtrz ligand into a glass bottle, add 1.5 mL of N,N-dimethylacetamide (DMA) solution, and stir until dissolved; (2) Weigh 60.0 mg (0.2 mmol) of zinc nitrate hexahydrate, add 1.5 mL of deionized water, and stir until dissolved. (3) The DMA solution of the ligand and the aqueous solution of zinc nitrate hexahydrate were mixed and stirred evenly. The resulting solution was sealed and reacted at 100°C for 48 h. The solution was filtered and then washed and dried using the same method as in Example 1 to obtain MOF (Zn-btb-fmtrz) with a yield of 47.8% (based on H3btb).

[0031] Example 5 Synthesis of a doubly intercalated MOF (Zn-btb-fmtrz) (1) Weigh 8.8 mg (0.02 mmol) of H3btb ligand and 3.3 mg (0.04 mmol) of fmtrz ligand into a glass bottle, add 1.5 mL of N,N-dimethylacetamide (DMA) solution, and stir until dissolved; (2) Weigh 60.0 mg (0.2 mmol) of zinc nitrate hexahydrate, add 1.5 mL of deionized water, and stir until dissolved. (3) The DMA solution of the ligand and the aqueous solution of zinc nitrate hexahydrate were mixed and stirred evenly. The resulting solution was sealed and reacted at 100°C for 48 h. The solution was filtered and then washed and dried using the same method as in Example 1 to obtain MOF (Zn-btb-fmtrz) with a yield of 35.2% (based on H3btb).

[0032] Example 6 Preparation Method of a Double Intercalated MOF (Zn-btb-fmtrz) (1) Weigh 8.8 mg (0.02 mmol) of H3btb ligand and 5.8 mg (0.07 mmol) of fmtrz ligand into a glass bottle, add 1.5 mL of N,N-dimethylacetamide (DMA) solution, and stir until dissolved; (2) Weigh 30.0 mg (0.1 mmol) of zinc nitrate hexahydrate, add 0.75 mL of deionized water, and stir until dissolved. (3) The DMA solution of the ligand and the aqueous solution of zinc nitrate hexahydrate were mixed and stirred evenly. The resulting solution was sealed and reacted at 100°C for 48 h. The solution was filtered and then washed and dried using the same method as in Example 1 to obtain MOF (Zn-btb-fmtrz) with a yield of 77.9% (based on H3btb).

[0033] Example 7 Preparation Method of a Double Intercalated MOF (Zn-btb-fmtrz) (1) Weigh 8.8 mg (0.02 mmol) of H3btb ligand and 5.8 mg (0.07 mmol) of fmtrz ligand into a glass bottle, add 1.5 mL of N,N-dimethylacetamide (DMA) solution, and stir until dissolved; (2) Weigh 42.0 mg (0.14 mmol) of zinc nitrate hexahydrate, add 1.05 mL of deionized water, and stir until dissolved. (3) The DMA solution of the ligand and zinc nitrate hexahydrate were mixed and stirred evenly. The resulting solution was sealed and reacted at 100°C for 48 h. The solution was filtered and then washed and dried using the same method as in Example 1 to obtain MOF (Zn-btb-fmtrz) with a yield of 61.6% (based on H3btb).

[0034] The MOF (Zn-btb-fmtrz) prepared in Examples 2-7 has the same structure as that obtained in Example 1. In order to understand the single crystal structure of the synthesized MOF in detail, the product obtained in Example 1 was characterized by single crystal X-ray diffraction analysis (SC-XRD). Figure 1 a is the minimum structural unit diagram of the MOF (Zn-btb-fmtrz) obtained above, Table 1 is the crystallographic parameters of the Zn-btb-fmtrz obtained above, Table 2 is the selective bond length, and Table 3 is the selective bond angle. Its molecular formula is [Zn4(H2O)2(fmtrz)2(btb)2(DMA)]·2DMA. It crystallizes in the space group and presents a two-fold interlaced three-dimensional framework structure. Specifically, the basic asymmetric unit of MOF (Zn-btb-fmtrz) consists of four independent Zn 2+ ions, two deprotonated btb 3- ligand, two fmtrz ligands, one coordinated DMA molecule, two coordinated water molecules and two free DMA. Figure 1 As can be seen from the schematic diagram of the secondary building unit of b, four independent Zn 2+The ions have different coordination environments. Zn1 is coordinated with two oxygen atoms from the carboxylic acid ligand, two nitrogen atoms from the azole ligand and one oxygen atom from the DMA molecule. Zn2 is connected to four oxygen atoms of the carboxylic acid ligand (two of which are from the same carboxylic acid ligand and the other two are from two different carboxylic acid ligands) and one nitrogen atom of the azole ligand. Zn3 is connected to two oxygen atoms of the carboxylic acid ligand, one nitrogen atom of the azole ligand and two oxygen atoms of water molecules. Zn4 is coordinated with four oxygen atoms of the carboxylic acid ligand and two nitrogen atoms of the azole ligand.

[0035] Figure 1 c is a schematic diagram of the coordination situation, combined with Figure 1 aIt can be seen Figure 1 Zn1, Zn2, Zn3, and Zn4 in c are the same structural unit, and Zn3' is in another structural unit. The secondary building units are connected to each other through the H3btb ligand, further forming a three-dimensional framework structure in space.

[0036] Figure 2 This is a simplified structural diagram of the MOF (Zn-btb-fmtrz) material prepared in Example 1. Figure 2 a is a structural diagram, Figure 2 b is a schematic diagram of the interpenetrating structure. It can be seen that the structure is a double interpenetrating structure, and the mutual interpenetration of the two interpenetrating layers forms a new channel structure.

[0037] The rhombic pore size of MOF (Zn-btb-fmtrz) is 9.3 Å × 18.5 Å. The larger pore size is conducive to the entry of guest gas molecules. In addition, the DMA guest molecules coordinated with Zn-btb-fmtrz are easily removed after activation, resulting in the partial removal of Zn 2+ It becomes unsaturated in the coordination environment. This modification not only increases the pore size but also provides more adsorption sites for the guest molecule acetylene. The btb ligand contains numerous oxygen atoms, and fmtrz contains nitrogen atoms and methyl functional groups. The N / O sites can produce stronger interactions with acetylene, making Zn-btb-fmtrz exhibit good acetylene adsorption performance.

[0038] The sample prepared in Example 1 was subjected to powder X-ray diffraction (PXRD) analysis at room temperature. Figure 3 It can be seen that the PXRD peaks of the synthesized MOF (Zn-btb-fmtrz) are basically consistent with the results of SC-XRD data simulation, confirming the successful synthesis of the sample.

[0039] Table 1 Crystal data

[0040] Table 2 Selective bond lengths of MOF (Zn-btb-fmtrz)

[0041] Table 3 Selective bond angles of MOF (Zn-btb-fmtrz) Application Example 1 Acid-base stability test of doubly intercalated MOF (Zn-btb-fmtrz) Weigh 6 samples of MOF (Zn-btb-fmtrz) synthesized in Example 1, and put about 0.1 g of each sample into 10 mL glass bottles. Add 5 mL of aqueous solution (pH adjusted with sodium hydroxide and hydrochloric acid, pH = 1, 3, 5, 7, 9, 11) respectively, soak for 24 hours, filter and dry after soaking, and perform powder X-ray diffraction analysis. The test results refer to Figure 4 The experiment showed that within the pH range of 1-11, the peak position and peak intensity of XRD did not change significantly, which indicates that the material maintains its structural integrity. The material has high acid-base stability and its stable range is pH = 1-11.

[0042] Application Example 2 Thermal Stability Test of Double Intercalated MOF (Zn-btb-fmtrz) Figure 5 The thermogravimetric analysis (TGA) curve of MOF (Zn-btb-fmtrz) shows that the structure of MOF (Zn-btb-fmtrz) completely decomposes at approximately 500°C. Therefore, it can be concluded that MOF (Zn-btb-fmtrz) has good thermal stability due to its interpenetrating structure and the hydrophobicity of the methyl groups in the ligands.

[0043] Application Example 3 Performance Test of Double Intercalated MOF (Zn-btb-fmtrz) for Acetylene Purification The product prepared in Example 1 was directly degassed and activated at 160° C. under vacuum for 12 h to obtain the MOF (Zn-btb-fmtrz) from which the DMA guest was removed.

[0044] The activated MOF (Zn-btb-fmtrz) was subjected to N2 adsorption-desorption experiments at 77 K. 0.1 g of the activated MOF was used to test its single-component gas adsorption isotherm at 77 K on a Micromeritics ASAP 2020 instrument. The specific surface area and pore size distribution were calculated based on the adsorption data. Figure 6 The results show that the MOF with interpenetrating structure (Zn-btb-fmtrz) has high N2 saturation adsorption capacity and BET specific surface area at 77 K, among which the N2 saturation adsorption capacity reaches 183 cm3 / g, and the BET specific surface area reaches 697m 2 / g.

[0045] The pressure range of the test sample was 0-100 kPa, and 0.1g of the activated MOF was tested on a Micromeritics ASAP2020 instrument for the adsorption of single components C2H2, C2H4 and CO2 at 298K. Figure 7 The adsorption curve shows that the MOF (Zn-btb-fmtrz) exhibits good adsorption capacity for C2H2. The desorption curve completely overlaps with the adsorption curve, demonstrating that the material can be easily regenerated and reused.

[0046] To confirm the cyclic stability of MOF (Zn-btb-fmtrz), 0.1 g of activated MOF was subjected to multiple acetylene adsorption cycle tests on a Micromeritics ASAP 2020 instrument in the pressure range of 0-100 kPa at 298 K. Figure 8 The results showed that the adsorption capacity of MOF (Zn-btb-fmtrz) for C2H2 remained stable during five adsorption cycle experiments, indicating that the material has good cyclic stability.

[0047] In order to test the separation performance of MOF (Zn-btb-fmtrz) in practical applications, a mixed gas penetration experiment was carried out.

[0048] 1) At 298 K, mixed gases of varying proportions flowed through a sample column containing a MOF (Zn-btb-fmtrz) at a flow rate of 2 mL / min. Initially, a co-adsorption reaction occurred, followed by the exit of the mixed gases at different times until the concentrations of the two components reached their initial concentrations, indicating adsorption completion. The gas mixtures used were C2H2 / CO2 (50:50 volume fraction ratio) and C2H2 / C2H4 (50:50 and 1:99 volume fraction ratios, respectively). 2) Under room temperature conditions, the MOF (Zn-btb-fmtrz) was desorbed and regenerated by inert gas (He) purge to obtain high-purity acetylene.

[0049] like Figure 9As shown in Figure a, at 298 K, a C2H2 / CO2 (50 / 50, v / v) gas mixture flowed through a sample column containing MOF (Zn-btb-fmtrz) at a flow rate of 2 mL / min. A co-adsorption reaction occurred in the initial stage of the experiment, with a co-adsorption time of 26.8 min / g. Thereafter, the adsorption of CO2 reached saturation and gradually eluted from the sample column. After 35.4 min / g, the presence of C2H2 gas began to be detected, and then MOF (Zn-btb-fmtrz) gradually adsorbed and reached saturation, with a total separation time of 8.6 min / g. Figure 9 As shown in Figure b, when separating a C2H2 / C2H4 (1 / 99, v / v) gas mixture, the high-concentration C2H4 eluted from the column almost instantly (2.0 min / g), while C2H2 eluted from the adsorption column at approximately 22.9 min / g, with a total separation time of 20.9 min / g. Figure 9 As shown in c, for C2H2 / C2H4 (50 / 50, v / v) mixed gas, MOF (Zn-btb-fmtrz) also showed significant separation effect, with a separation time of about 5 min / g. After each set of adsorption experiments, an inert gas (He) was used to purge at a rate of 15 mL / min. Figure 9 As can be seen from Figure d, the separation time of the three penetration cycle experiments on the C2H2 / CO2 (50 / 50, v / v) mixed gas is basically the same, which shows that the MOF (Zn-btb-fmtrz) has good regeneration ability, that is, the regeneration conditions are simple and it can be recycled many times. Figure 9 It can be seen that whether it is C2H2 / CO2 or C2H2 / C2H4, MOF (Zn-btb-fmtrz) can successfully separate the mixed gas and achieve the purification of acetylene gas.

[0050] The above describes specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments. Those skilled in the art can make various variations or modifications within the scope of the claims, which will not affect the essential content of the present invention.

Claims

1. A doubly intercalated MOF, characterized in that: Its molecular formula is [Zn4(H2O)2(fmtrz)2(btb)2(DMA)]·2DMA, with a relative molecular mass of 1589.

81. It is a colorless, transparent block crystal, where Zn represents divalent zinc ion, H2O represents water molecule, fmtrz represents 3-methyl-1H-1, 2,4-triazole, btb represents deprotonated 1,3,5-tris(4-carboxyphenyl)benzenecarboxylic acid, and DMA represents N,N-dimethylacetamide.

2. The doubly intercalated MOF according to claim 1, characterized in that The doubly interpenetrating MOF in the triclinic system The crystallization space group shows a two-fold interpenetrating three-dimensional framework structure, and its basic asymmetric unit includes four independent Zn 2+ ions, two deprotonated btb 3- ligand, two fmtrz ligands, one coordinated DMA molecule, two coordinated water molecules and two free DMA; four independent Zn 2+ The ions have different coordination environments. Zn1 is coordinated with two oxygen atoms from the carboxylic acid ligand, two nitrogen atoms from the azole ligand, and one oxygen atom from the DMA molecule. Zn2 is connected to four oxygen atoms of the carboxylic acid ligand and one nitrogen atom of the azole ligand, two of which are from the same carboxylic acid ligand and the other two are from two different carboxylic acid ligands. Zn3 is connected to two oxygen atoms of the carboxylic acid ligand, one nitrogen atom of the azole ligand, and two oxygen atoms of water molecules. Zn4 is coordinated with four oxygen atoms of the carboxylic acid ligand and two nitrogen atoms of the azole ligand. The rhombic pore size of the doubly intercalated MOF is 9.3 Å × 18.5 Å, and the unit cell parameters are: axis lengths a=14.8203(6) Å, b=16.7360(8) Å, c=18.2865(9) Å, α=67.072(2)°, β=71.819(2)°, γ=87.068(2)°; the unit cell volume is V=3955.9(3) Å. 3 ; Z=2.

3. The method for preparing the doubly intercalated MOF according to claim 1 or 2, characterized in that: The specific steps are as follows: (1) Weigh 1,3,5-tris(4-carboxyphenyl)benzene and 3-methyl-1H-1,2,4-triazole into a reaction vessel, add N,N-dimethylacetamide as solvent, and stir until dissolved; (2) preparing an aqueous solution of a zinc-containing compound, namely, weighing the zinc-containing compound, adding it to deionized water, and stirring until it dissolves; (3) The N,N-dimethylacetamide solution of the ligand and the aqueous solution containing the zinc compound are mixed, and after being stirred evenly, the resulting solution is sealed, subjected to high-temperature hydrothermal reaction, washed, and dried to obtain MOF.

4. The method for preparing the doubly intercalated MOF according to claim 3, characterized in that: The zinc-containing compound is zinc nitrate.

5. The method for preparing the doubly intercalated MOF according to claim 3, wherein: The molar ratio of the zinc-containing compound to the ligand fmtrz is 1:1-5:1, and the molar ratio of the two ligands H3btb and fmtrz is 1:1-1:

5.

6. The method for preparing the doubly intercalated MOF according to claim 3, characterized in that: For every 0.02 mmol of 1,3,5-tris(4-carboxyphenyl)benzene, there was 1.5 mL of DMA, and for every 0.2 mmol of zinc nitrate, there was 1.5 mL of H2O.

7. The method for preparing the doubly intercalated MOF according to claim 3, characterized in that: The high-temperature hydrothermal reaction temperature is controlled at 90-110° C., and the reaction time is 24-48 h.

8. The method for preparing the doubly intercalated MOF according to claim 3, characterized in that: The washing operation is to use DMA and H2O for washing three times respectively; the drying condition is to place it in a vacuum drying oven at 60°C for 24 hours.

9. Use of the doubly intercalated MOF according to claim 1 in acetylene purification, characterized in that: The specific steps are as follows: 1) A mixed gas containing acetylene is passed through a container filled with the prepared doubly interpenetrating MOF at a certain temperature and pressure to complete the adsorption of acetylene; 2) The desorption and regeneration of the doubly interpenetrating MOF was completed by purging with inert gas at room temperature to obtain high-purity acetylene.

10. The doubly interpenetrating MOF according to claim 9 is applied to acetylene purification, characterized in that: The mixed gas is acetylene and separation gas, and the separation gas includes one of ethylene and carbon dioxide; the volume fraction of acetylene in the mixed gas is greater than 0 and less than or equal to 50%; the adsorption temperature is 0-25°C, the pressure in the container is 100 kPa or above, and the reaction space velocity is 5-100 h -1 The usage of double-interpenetrating MOF is ≥1g for every mixed gas flow rate of 2 mL / min.

Images