Process for the preparation of zinc-based complex compounds and their use for gas separation

Abstract

The application belongs to the technical field of new materials, and particularly relates to a Zn-MOF material and a preparation method and application thereof. The chemical general formula is [Zn2(H2O)4(TCPB-Me)], wherein Zn is a divalent zinc ion, and TCPB-Me is a deprotonated 1,2,4,5-tetrakis(4-carboxylphenyl)-3,6-dimethylbenzene ligand. The structure of the Zn-MOF material belongs to a monoclinic system, a P21 / c space group, the cell parameter is a-axis length, and an a-axis angle alpha = gamma = 90 DEG, beta = 90.989(10) DEG, and the cell volume is Z = 4. The preparation method of the Zn-MOF material is that metal zinc salt and H4TCPB-Me are dissolved in a mixed solution of an organic solvent and water; sealed and placed in an oven at 80-120 DEG C for 24-72 hours; naturally cooled to room temperature to obtain the Zn-MOF material. Benefited from the unique structure, the Zn-MOF material can be applied to the fields of mixed gas C2H2 / CO2 and CO2 / CH4 separation.

Description

Technical Field

[0001] This invention belongs to the field of new materials technology, specifically relating to a method for preparing a zinc-based coordination compound and its application in gas separation. Background Technology

[0002] Acetylene (C2H2) is a key industrial raw material widely used in the manufacture of basic chemicals such as ethylene, polyvinyl chloride, propylene, and butadiene, as well as synthetic materials such as rubber, fibers, and plastics. Industrially, acetylene is mainly produced through the oxidation of methane. However, the acetylene produced by this reaction contains a significant amount of carbon dioxide (CO2) impurities, affecting its efficiency in downstream chemical processes and the quality of the final product. Therefore, efficiently separating high-purity acetylene is crucial for improving energy efficiency and reducing production costs. Faced with energy shortages and environmental crises, cleaner and more economical gaseous resources such as natural gas, biogas, shale gas, and coalbed methane have attracted considerable attention as ideal substitutes for oil and coal. The active ingredient in these gaseous resources is methane (CH4), which often contains carbon dioxide, reducing its calorific value and corroding gas pipelines, thus limiting its utilization. Therefore, selective CO2 capture and efficient CO2 / CH4 separation are critical.

[0003] Current gas separation processes mainly include chemical absorption, cryogenic distillation, and solvent extraction. These methods are often energy-intensive and have adverse environmental impacts. For example, cryogenic distillation separates components in a mixed gas based on differences in their liquefaction temperatures, requiring a large amount of energy to cool and liquefy the gas. Chemical absorption, on the other hand, requires large amounts of solvent, and the solvent recovery and regeneration processes are energy-intensive, potentially generating harmful waste liquids that also have an environmental impact. Therefore, there is an urgent need for a low-energy, environmentally friendly separation and purification process and materials.

[0004] Compared to traditional separation techniques, adsorption separation can be performed at room temperature and pressure, with lower cost and energy consumption. However, traditional adsorbents, such as zeolites, molecular sieves, and activated carbon, have small surface areas and porosities, and their structures are not controllable, making it difficult to achieve gas separation. Metal-organic frameworks (MOFs) are crystalline materials with periodic network structures formed by the self-assembly of metal ions and organic ligands. MOFs possess highly ordered pore structures, large specific surface areas, and controllable and modifiable pore sizes, making them highly applicable in gas adsorption, storage, separation, and selective gas adsorption. They can serve as a low-energy, high-efficiency, and highly adaptable adsorbent. Summary of the Invention

[0005] In order to solve the technical problems in the background art, the present invention provides a Zn-MOF material.

[0006] The technical solution of this invention to solve the above-mentioned technical problems is as follows: A Zn-MOF material with the general chemical formula [Zn2(H2O)4(TCPB-Me)], wherein Zn is a divalent zinc ion, and TCPB-Me is a deprotonated 1,2,4,5-tetra(4-carboxyphenyl)-3,6-xylene ligand. The Zn-MOF material has a monoclinic crystal system, space group P21 / c, and its cell parameters are axial lengths... The axial angles α = γ = 90°, β = 90.989(10)°, and the unit cell volume is Z = 4.

[0007] The beneficial effects of this invention are:

[0008] 1. The synthesis method of the Zn-MOF material of the present invention is simple, mild, and yields 45%-50%. The desired material can be obtained by dissolving the reactants and reacting at around 100°C. None of the raw materials used contain toxic or harmful substances or catalysts, and no toxic or harmful substances are generated during the preparation process.

[0009] 2. The Zn-MOF material of the present invention has a triple interpenetrating structure with a SQL topology in each layer, which has excellent thermal stability.

[0010] 3. The Zn-MOF material of the present invention can be used to prepare adsorbent materials and proton conduction materials, and is a highly promising composite functional porous material.

[0011] The crystal structure of the Zn-MOF material of this invention was measured at 150 K using an Agilent SuperNova microspot X-ray single-crystal diffractometer, with data received on an EosCCD. A graphite monochromator was used, and λ(Cu Kα) was... Data analysis and absorption correction were performed using the CrysAlisPro tool with a variable-speed arbitrary-angle scan mode of ω-2θ. All structures were solved directly using the SHELXS program packaged in SHELXTL, and the structure was refined using the SHELXL full-matrix least squares method. Anisotropic treatment was applied to all non-hydrogen atoms, and hydrogen atoms in the organic ligands were generated through geometric symmetry. The resulting Zn-MOF material structure belongs to the monoclinic crystal system, space group P21 / c, and the basic structural unit of the crystal is obtained from asymmetric units through symmetry operations.

[0012] The asymmetric unit contains 0.5 deprotonated TCPB-Me ligands, 1 zinc ion, and 2 coordinated oxygen atoms.

[0013] Zinc ions are coordinated in a four-coordinate manner to four oxygen atoms, which originate from oxygen atoms (O5, O6) in the two carboxyl groups (O1-C1-O5, O6-C14-O7) of two different ligands, and two water molecules (O2, O4). Each Zn atom center is combined with two oxygen atoms from two TCPB-Me ligands and two terminal H2O atoms to form a regular tetrahedron. Each TCPB-Me ligand is connected to four Zn atom centers through its four carboxyl oxygen atoms.

[0014] The Zn-MOF material structure belongs to the monoclinic crystal system, space group P21 / c, and its cell parameter is the axis length. The axial angles α = γ = 90°, β = 90.989(10)°, and the unit cell volume is Z = 4.

[0015] This invention also provides a method for preparing Zn-MOF materials, comprising the following steps:

[0016] A. H4TCPB-Me ligand and zinc nitrate hexahydrate are dissolved in a solvent to obtain a homogeneous mixed solution. The molar ratio of H4TCPB-Me ligand to zinc nitrate hexahydrate is 1:4, and the concentration of H4TCPB-Me ligand in the solution is 1.7047 mmol / L.

[0017] B. Place the mixed solution described in step A in a glass bottle and keep it at 100°C for 24–72 hours to obtain the Zn-MOF material.

[0018] The beneficial effects of this invention are: the preparation method is simple, the reaction can proceed rapidly, and it saves energy and time. Furthermore, the preparation method of Zn-MOF materials in this invention has high yield and requires less ligand, thus saving costs.

[0019] Based on the above technical solution, the present invention can be further improved as follows:

[0020] In this invention, the solvent is N,N-dimethylacetamide and water, and the volume ratio is 1:0.1 to 10.

[0021] The advantages of adopting the above-mentioned further scheme are that the solvent composed of N,N-dimethylacetamide and water is readily available, inexpensive, and causes little pollution, and the prepared Zn-MOF material has a better crystalline state.

[0022] In this invention, the molar ratio of the H4TCPB-Me ligand to the zinc nitrate hexahydrate is 1:4, and the concentration of the H4TCPB-Me ligand in the solution is 1.7047 mmol / L.

[0023] The beneficial effect of adopting the above-mentioned further scheme is that the Zn-MOF material obtained by the determined concentration and molar amount ratio has a better crystal morphology and the reaction is more smooth.

[0024] This invention also provides an application of Zn-MOF material in the field of low-carbon hydrocarbon gas separation. The Zn-MOF material is used to perform adsorption tests on single-component CO2, C2H2 and CH4 gases to obtain differentiated adsorption amounts of C2H2 / CO2 and CO2 / CH4 for gas separation.

[0025] The beneficial effect of the present invention is that the Zn-MOF material is applied to the field of C2H2 / CO2 and CO2 / CH4 gas separation, making the function of Zn-MOF material more comprehensive. Attached Figure Description

[0026] Figure 1 This is a structural diagram of the asymmetric structural unit of the Zn-MOF material of the present invention;

[0027] Figure 2 The structural diagram of the Zn-MOF material of this invention is as follows: (a) coordination environment of zinc ions; (b) formed SQL topology; (c) triple interpenetration structure and stacking mode; (d) pores;

[0028] Figure 3 The XRD patterns of the Zn-MOF material of this invention are the test and simulation results. The horizontal axis is the Bragg diffraction angle and the vertical axis is the diffraction intensity.

[0029] Figure 4 This is a thermogravimetric curve of the Zn-MOF material of the present invention, with the horizontal axis representing temperature and the vertical axis representing the percentage of weight loss.

[0030] Figure 5 The image shows the infrared spectrum of the Zn-MOF material of this invention. The horizontal axis represents wavenumber, and the vertical axis represents transmittance.

[0031] Figure 6 This is the adsorption isotherm of the Zn-MOF material of the present invention on N2 at 77K. The horizontal axis is pressure and the vertical axis is the amount of adsorption.

[0032] Figure 7 The image shows the pore size distribution curve of the Zn-MOF material of this invention, with the horizontal axis representing pore size and the vertical axis representing pore size distribution.

[0033] Figure 8 The graph shows the adsorption isotherms of CO2, CH4 and C2H2 on the Zn-MOF material of this invention at 273K. The horizontal axis represents pressure and the vertical axis represents the amount of adsorption.

[0034] Figure 9The image shows the adsorption isotherms of the Zn-MOF material of this invention for CO2, CH4 and C2H2 at 298K. The horizontal axis represents pressure and the vertical axis represents the amount of adsorption.

[0035] Figure 10 This is an adsorption enthalpy diagram of CO2, CH4 and C2H2 for the Zn-MOF material of this invention. The horizontal axis is the adsorption amount and the vertical axis is the adsorption enthalpy.

[0036] Figure 11 The graphs show the adsorption selectivity of the Zn-MOF material of this invention for C2H2 / CO2 and CO2 / CH4 mixed gases at 273K and 298K, respectively. The horizontal axis represents pressure, and the vertical axis represents the common logarithm of selectivity. Detailed Implementation

[0037] The principles and features of the present invention will be described in detail below with reference to implementation. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0038] Example 1

[0039] A method for preparing Zn-MOF materials specifically includes the following steps:

[0040] A. Accurately weigh 0.0050 g and 0.0085 mmol of 1,2,4,5-tetra(4-carboxyphenyl)-3,6-xylene (H4TCPB-Me) ligand and 0.0100 g and 0.0336 mmol of zinc nitrate hexahydrate into a reaction vessel using an analytical balance. At room temperature, add 5 mL of a mixed solvent of N,N-dimethylacetamide and water to the reaction vessel. The volume ratio of N,N-dimethylacetamide to water is 1:1.

[0041] B. Place the mixed solution from step A into a glass bottle and keep it in a constant temperature blower at 100℃ for 24–72 h to obtain colorless crystalline Zn-MOF material.

[0042] like Figure 1 and Figure 2 As shown, the colorless crystalline Zn-MOF material was tested at 150 K using an Agilent SuperNova micro-focal-spot X-ray single-crystal diffractometer, with data received on an EosCCD. A graphite monochromator was used, and λ(CuKα) was... Data analysis and absorption correction were performed using the CrysAlisPro tool with a variable-speed arbitrary-angle scan mode of ω-2θ. All structures were solved directly using the SHELXS program encapsulated in SHELXTL, and the structure was refined using the SHELXL full-matrix least squares method. Anisotropic treatment was applied to all non-hydrogen atoms, and hydrogen atoms in organic ligands were generated through geometric symmetry. The crystal data are shown in Table 1, typical bond lengths in Table 2, and typical bond angles in Table 3.

[0043] Table 1: Crystal Data

[0044]

[0045]

[0046] Table 2: Typical bond length data for crystals (unit: )

[0047] Zn1 O5 1.954(8) Zn1 O6 1.977(9) Zn1 O3 1.924(6) Zn1 O1 1.940(7) O1 C1 1.243(12) O2 C1 1.232(12) C6 C7 1.384(12) C6 C5 1.391(13) C7 C2 1.372(13) C3 C2 1.388(12) C3 C4 1.388(12) C9 C8 1.385(12) C8 C5 1.480(11) C5 C4 1.364(13) C2 C1 1.508(11)

[0048] Table 3: Typical bond angle data for crystals (unit: °)

[0049]

[0050]

[0051] Based on the crystal data in Tables 1, 2, and 3, the following characterizations of the Zn-MOF materials were obtained:

[0052] The asymmetric unit consists of 0.5 deprotonated TCPB-Me ligands, 1 zinc ion, and 2 coordinated oxygen atoms.

[0053] The zinc ion is connected to four oxygen atoms in a four-coordinate manner. These four oxygen atoms come from the oxygen atoms (O5, O6) in the two carboxyl groups (O1-C1-O5, O6-C14-O7) of two different ligands and from two water molecules (O2, O4).

[0054] The carboxyl groups in the ligands (O1-C1-O5, O6-C14-O7) connect to adjacent Zn atoms in a monodentate bridging mode, ultimately forming the [Zn(H2O)2][COO]2 structure. All carboxyl groups in TCPB-Me are deprotonated and connect to adjacent Zn atoms in a monodentate bridging mode, forming a two-dimensional Sql topological network. Three two-dimensional Sql topological networks interweave to form one layer of the framework, with layers connected by hydrogen bonds (O2-H2b···O1, bond length...). The stacked elements are connected to form a three-dimensional frame structure.

[0055] The Zn-MOF material structure of this invention belongs to the monoclinic crystal system, space group P21 / c, and its unit cell parameter is the axis length. The axial angles α = γ = 90°, β = 90.989(10)°, and the unit cell volume is Z = 4.

[0056] like Figure 3 As shown, the colorless crystalline Zn-MOF material was tested using a powder X-ray diffractometer. The Bragg diffraction angle was measured from 3 to 50°, with diffraction intensity measured every 0.01°. The Zn-MOF material exhibited the diffraction pattern shown in the figure. The diffraction pattern indicates that the collected Zn-MOF material has good phase purity.

[0057] like Figure 4 As shown, thermogravimetric analysis (TGA) was performed on the colorless crystalline Zn-MOF material. The TGA test was conducted on a Mettler simultaneous thermogravimetric analyzer (model RGA / DSC-1). Nitrogen was used for both the reaction gas and the protective gas, with a flow rate of 25 mL / min. The run time was 50 minutes, the heating rate was 10 °C / min, and the test temperature range was 30–900 °C. Figure 4 The thermogravimetric analysis (TGA) curves show that the Zn-MOF material is stable up to approximately 492°C. The complex loses its coordinating solvent at 256°C, and the weight loss between 256°C and 492°C is due to framework collapse. This demonstrates that the Zn-MOF material of this invention exhibits excellent stability and can decompose at high temperatures.

[0058] like Figure 5 As shown, the colorless crystalline aluminum-based complex was detected by infrared spectroscopy. The infrared measurement was performed using the KBr pellet method, and samples were collected from 4000 to 4000 cm⁻¹ using a Nicolet 330 FTIR spectrometer. -1 Infrared spectrum within the region. From Figure 5 It can be seen from the interior that the complex is located at 1600 cm⁻¹ -1 The nearby absorption peak can be attributed to the stretching vibration peak of the benzene ring skeleton in the ligand, located at 1400 cm⁻¹. -1 The nearby absorption peaks can be attributed to the symmetric stretching vibrations of the deprotonated carboxylate group, located between 1300 and 400 cm⁻¹. -1 The absorption peaks in the region are characteristic peaks of the fingerprint region belonging to the Zn-MOF material.

[0059] like Figure 6As shown, the colorless crystalline Zn-MOF material was tested using an ASAP2020 instrument from Micron Instruments, Inc. The zinc-based complex exhibited an adsorption isotherm for single-component N2 at 77 K, as shown in the figure. This adsorption isotherm is a type II isotherm, exhibiting a relatively significant desorption hysteresis. From the isotherm, the single-point BET specific surface area of ​​the Zn-MOF material at P / P0 = 0.2 is 204.765 m². 2 / g, BET specific surface area is 220.228m² 2 / g; the total pore volume at a single point when P / P0 = 0.99 is 0.198 cm³. 3 / g, t-plot micropore volume is 0.061cm³. 3 / g. The pore size distribution was calculated from the N2 adsorption isotherm as follows: Figure 7 As shown.

[0060] like Figure 8 and Figure 9 As shown, the colorless crystalline Zn-MOF material was tested using an ASAP2020 instrument from Micron Instruments, Inc. The zinc-based complex exhibited adsorption isotherms for single-component CO2, C2H2, and CH4 gases as shown in the figure. The adsorption capacities of CO2, C2H2, and CH4 at 273 K were 40.5 cm⁻¹, respectively. 3 / g, 49.7cm 3 / g and 16.2cm 3 / g, the adsorption capacities of CO2, C2H2 and CH4 at 298K are 29.6 cm⁻¹, respectively. 3 / g, 44.1cm 3 / g and 7.9cm 3 / g. Therefore, the differential adsorption amounts shown in the figure indicate that the Zn-MOF material can be applied to the gas separation of C2H2 / CO2 and CO2 / CH4.

[0061] like Figure 10 As shown, the adsorption enthalpy was calculated using the virial formula for the adsorption isotherms of CO2, C2H2, and CH4, yielding the relationship curves between the adsorption enthalpy and the adsorption amount of CO2, C2H2, and CH4. The figure shows that the maximum adsorption enthalpies of the Zn-MOF material for CO2, C2H2, and CH4 are 26.64 kJ / mol, 46.54 kJ / mol, and 30.48 kJ / mol, respectively.

[0062] like Figure 11As shown in the figure, the adsorption selectivity of the Zn-MOF material for CO2, C2H2, and CH4 was analyzed using the ideal adsorption solution theory, and the selectivity-pressure curves are obtained. The figure shows that the Zn-MOF material exhibits high adsorption selectivity for both C2H2 / CO2 and CO2 / CH4.

[0063] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A Zn-MOF material, characterized in that: The general chemical formula is [Zn2(H2O)4(TCPB-Me)], where Zn is a divalent zinc ion, TCPB-Me is a deprotonated 1,2,4,5-tetra[4-carboxyphenyl]-3,6-xylene ligand, each Zn atom center combines with two oxygen atoms from two TCPB-Me ligands and two terminal H2O to form a regular tetrahedron, and each TCPB-Me ligand is connected to four Zn atom centers through its four carboxyl oxygen atoms; The Zn-MOF material structure belongs to the monoclinic crystal system, space group P21 / c, and its cell parameter is the axis length. The axial angles α = γ = 90°, β = 90.989(10)°, and the unit cell volume is Z = 4.

2. A method for preparing the Zn-MOF material as described in claim 1, characterized in that, Includes the following steps: A. H4TCPB-Me ligand and zinc nitrate hexahydrate are dissolved in a solvent to obtain a homogeneous mixed solution. The molar ratio of H4TCPB-Me ligand to zinc nitrate hexahydrate is 1:4, and the concentration of H4TCPB-Me ligand in the solution is 1.7047 mmol / L. B. Place the mixed solution described in step A in a glass bottle and keep it at 100°C for 24–72 hours to obtain the Zn-MOF material.

3. The method for preparing the zinc-based complex according to claim 2, characterized in that, The solvent is composed of N,N-dimethylacetamide and water, wherein the volume ratio of N,N-dimethylacetamide to water is 1:

1.

4. The method for preparing Zn-MOF material according to any one of claims 2 or 3, characterized in that, The molar ratio of the H4TCPB-Me ligand to the zinc nitrate hexahydrate is 1:4, and the concentration of the H4TCPB-Me ligand is 1.7047 mmol / L.

5. An application of the Zn-MOF material as described in claim 1 in the field of mixed gas separation, characterized in that, The Zn-MOF material was tested for adsorption of single-component CO2, C2H2, and CH4 gases, and the results showed significant differences in the adsorption amounts of C2H2 / CO2 and CO2 / CH4, which can be used for gas separation.

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