Preparation method and application of stimuli-responsive flexible two-dimensional zinc-based complex

Abstract

The invention belongs to the technical field of new materials, and discloses a preparation method and application of a stimuli-responsive flexible two-dimensional zinc-based complex. The structural unit of the complex is [Zn2 (OH) 2 (H2L1) 4], Zn is a divalent zinc ion, H2L1 represents a ligand: 4, 4 '-(2, 2-di-p-methylphenyl ethylene-1, 1-diyl) dibenzoic acid, and a ligand: 4, 4'-(2, 2-di-p-methylphenyl ethylene-1, 1-diyl) dibenzoic acid; wherein the structure of the two-dimensional zinc-based complex belongs to a hexagonal crystal system and a P-3 space group, and the cell parameters of the two-dimensional zinc-based complex are as follows: the axial length is # imgabs 0 # # imgabs 1 #, the axial angle is alpha = beta = 90 degrees, gamma = 120 degrees, and the cell volume is # imgabs 2 # Z = 6. Based on tetraphenylethylene (TPE), a material structure is constructed by modifying a functional methyl functional group on a benzene ring serving as a rotor group. The H2L1 contains two active benzene rings with methyl, and the benzene rings can still perform internal molecular movement even after forming a complex, so that the H2L1 is not limited. Therefore, the two-dimensional zinc-based complex can show stimulus-responsive structure reversible conversion during gas molecule adsorption, so that gas is specifically adsorbed. The two-dimensional zinc-based complex has the potential to be applied to the field of low-carbon hydrocarbon gas separation.

Description

Technical Field

[0001] The present invention belongs to the technical field of new materials, and particularly relates to a stimulus-responsive flexible two-dimensional zinc-based complex and its preparation method and application. Background Art

[0002] Lower olefins represented by ethylene are bulk basic chemicals in the global petrochemical industry. The global ethylene market size in 2023 was 137.2 billion US dollars. As the world's largest polyethylene consumer country, China accounts for about 30% of the global polyethylene consumption. Therefore, in the context of the "dual carbon" goal task, how to achieve low-energy consumption for obtaining lower olefins is a key scientific and technological problem to be solved urgently.

[0003] With the rapid progress of crystal engineering and structural chemistry, new porous materials, especially metal-organic framework (MOF) materials, have continuously achieved remarkable achievements in preparation technology and performance improvement. With its unique pore structure and tunability, this material has brought a revolutionary change to the field of materials science and engineering. By precisely controlling the pore size, shape, and pore wall characteristics, MOF materials can efficiently and selectively distinguish and separate specific molecules in complex environments. Flexible MOFs can respond to external conditions such as temperature, pressure, and guest molecules, and this responsiveness has attracted particular attention from researchers in the field of adsorption and separation technology. Systematically studying the influence law of tetraphenylethylene (TPE) on the performance of constructing stimulus-responsive flexible MOF materials not only helps to understand the complex mechanism of intermolecular interactions and structural regulation, but also has important scientific and practical application value for the development of highly functional flexible metal-organic framework materials. However, the current research on the application of flexible MOFs constructed by TPE in gas adsorption separation is limited. Therefore, the present invention uses methyl-functionalized functional group modification on the benzene ring where TPE is suspended, and then prepares a new stimulus-responsive flexible two-dimensional zinc-based complex and applies it in the field of separation of light hydrocarbons. Summary of the Invention

[0004] The present invention provides a stimulus-responsive flexible two-dimensional zinc-based complex porous material for effective separation of light hydrocarbon gases to solve the technical problems in the above background art.

[0005] The technical solution of the present invention to solve the above technical problems is as follows: A stimulus-responsive flexible two-dimensional zinc-based complex, the structural unit is [Zn2(OH)2(H2L1)4], wherein Zn is a divalent zinc ion, and H2L1 represents a 4,4'-(2,2-di-p-tolylethylene-1,1-diyl) dibenzoic acid ligand;

[0006] Among them, the two-dimensional zinc-based coordination complex structure belongs to the hexagonal crystal system, space group P-3, and its unit cell parameters are the axial lengths The axial angles α = β = 90°, γ = 120°, and the unit cell volume is Z = 6.

[0007] The present invention also provides a preparation method of a stimulus-responsive flexible two-dimensional zinc-based coordination complex, comprising the following steps:

[0008] A. Dissolve zinc nitrate hexahydrate and the ligand 4,4'-(2,2-di-p-tolylethylene-1,1-diyl) dibenzoic acid in a solvent, and obtain a homogeneous and clear mixed solution after stirring and ultrasonic dissolution. The molar dosage ratio of the 4,4'-(2,2-di-p-tolylethylene-1,1-diyl) dibenzoic acid ligand to the zinc nitrate hexahydrate is 1:(1-3), and the concentration of the 4,4'-(2,2-di-p-tolylethylene-1,1-diyl) dibenzoic acid ligand in the solution is 0.01-0.03 mmol / L.

[0009] B. Place the mixed solution obtained in step A in a glass bottle, and use the solvothermal method to place the glass bottle in a constant temperature static reaction at 90-100 °C for 3-5 days under closed conditions, and then slowly cool to room temperature. The product is filtered, washed, and dried to obtain the two-dimensional zinc-based coordination complex.

[0010] The advantages of the present invention are as follows: The preparation process conditions are simple, the reaction speed is fast, and it is effectively energy-saving and time-saving. At the same time, the preparation method of the two-dimensional zinc-based coordination complex in the present invention has a high yield and a low ligand dosage, thereby reducing costs.

[0011] On the basis of the above technical solutions, the present invention can be further improved as follows.

[0012] Further, the solvent is composed of N,N-dimethylformamide, absolute ethanol, and deionized water, and the volume ratio of N,N-dimethylformamide, absolute ethanol, and deionized water is 2:1:1.

[0013] The advantages of adopting the above improvement scheme include: The solvent composed of N,N-dimethylformamide, absolute ethanol, and deionized water used is easily obtained, has a low cost, and causes less pollution to the environment.

[0014] Further, the molar dosage ratio of the 4,4'-(2,2-di-p-tolylethylene-1,1-diyl) dibenzoic acid ligand to the zinc nitrate hexahydrate is 1:1.5, and the concentration of the 4,4'-(2,2-di-p-tolylethylene-1,1-diyl) dibenzoic acid ligand in the solution is 0.02 mmol / L.

[0015] The advantage of adopting the above improvement scheme is that by precisely setting the concentration and molar ratio, two-dimensional zinc-based complexes with better quality can be prepared, and the reaction process can be made smoother.

[0016] The present invention also provides an application of the stimulus-responsive flexible two-dimensional zinc-based complex in the field of low-carbon hydrocarbon gas separation, which is characterized in that the two-dimensional zinc-based complex conducts adsorption tests on acetylene (C2H2), ethylene (C2H4), ethane (C2H6), n-butane (n-C4H 10 ) and isobutane (iso-C4H 10 ) light hydrocarbons, and obtains different adsorption amounts for adsorption separation. Description of the Drawings

[0017] Figure 1 It is the structural diagram of the stimulus-responsive flexible two-dimensional zinc-based complex of the present invention;

[0018] Figure 2 It is the comparative curve graph of the simulated and experimental powder diffraction patterns of the stimulus-responsive flexible two-dimensional zinc-based complex of the present invention;

[0019] Figure 3 It is the thermogravimetric curve graph of the stimulus-responsive flexible two-dimensional zinc-based complex of the present invention, with the abscissa being temperature and the ordinate being the percentage of weight loss;

[0020] Figure 4 It is the N2 adsorption isotherm graph of the stimulus-responsive flexible two-dimensional zinc-based complex of the present invention at 77K, with the abscissa being the relative pressure and the ordinate being the adsorption amount;

[0021] Figure 5 It is the adsorption isotherm graph of the stimulus-responsive flexible two-dimensional zinc-based complex of the present invention for C2H2, C2H4 and C2H6 at 273K, with the abscissa being the absolute pressure and the ordinate being the adsorption amount;

[0022] Figure 6 It is the adsorption isotherm graph of the stimulus-responsive flexible two-dimensional zinc-based complex of the present invention for C2H2, C2H4 and C2H6 at 298K, with the abscissa being the absolute pressure and the ordinate being the adsorption amount.

[0023] Figure 7 It is the adsorption isotherm graph of the stimulus-responsive flexible two-dimensional zinc-based complex of the present invention for n-C4H 10 and iso-C4H 10 at 273K, with the abscissa being the absolute pressure and the ordinate being the adsorption amount;

[0024] Figure 8 It is the adsorption isotherm graph of the stimulus-responsive flexible two-dimensional zinc-based complex of the present invention for n-C4H 10 and iso-C4H 10Adsorption isotherm diagram, where the abscissa is the absolute pressure and the ordinate is the adsorption capacity. Detailed implementation manners

[0025] The principle and features of the present invention will be described in detail below in conjunction with the embodiments. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0026] Example 1

[0027] A preparation method of a stimulus-responsive flexible two-dimensional zinc-based complex, specifically including the following steps:

[0028] A. Accurately weigh 0.02 g, 0.05 mmol of 4,4'-(2,2-di-p-tolylethylene-1,1-diyl)dibenzoic acid ligand and 0.020 g, 0.067 mmol of zinc nitrate hexahydrate in a reaction vessel. At room temperature, add 3 mL of a mixed solvent composed of N,N-dimethylformamide, anhydrous ethanol and deionized water to the reaction vessel. The volume ratio of N,N-dimethylformamide, anhydrous ethanol and deionized water is 2:2:1;

[0029] B. Place the mixed solution in step A in a glass bottle and keep it warm in a constant-temperature air blast oven at 100 °C for 72 h to obtain a colorless transparent crystal-like two-dimensional zinc-based complex.

[0030] The obtained colorless transparent crystal-like two-dimensional zinc-based complex was tested at 298 K using an Agilent SuperNova microfocus X-ray single crystal diffractometer, and data was received on an Eos CCD. Using a graphite monochromator, λ(CuKα) is In the variable-angle scanning mode of ω-2θ, the CrysAlisPro tool was used for data analysis and absorption correction. All structures were directly solved using the SHELXS program encapsulated in SHELXTL, and structure refinement was performed using the SHELXL full matrix least squares method. Anisotropic treatment was performed on all non-hydrogen atoms, and the hydrogen atoms of the organic ligand were generated by geometric symmetry The crystal data shown in Table 1, the typical bond length data of the crystal shown in Table 2, and the typical bond angle data of the crystal shown in Table 3 were obtained. Tables 1, 2 and 3 are as follows:

[0031] Table 1: Crystal data

[0032]

[0033]

[0034] Table 2: Typical bond length data of the crystal (unit: )

[0035] Zn2 Zn3 3.1531(4) Zn2 <![CDATA[Zn3 1 > 3.1531(4) Zn2 <![CDATA[Zn3 2 > 3.1531(4) Zn2 O1 1.940(2) Zn2 <![CDATA[O8 3 > 1.9371(13) Zn2 <![CDATA[O8 4 > 1.9370(13) Zn2 <![CDATA[O8 5 > 1.9372(13) Zn3 O1 1.9376(7)

[0036] Table 3: Typical bond angle data of the crystal (unit: °)

[0037]

[0038]

[0039] Combining the crystal data in Table 1, Table 2 and Table 3, the following characterizations of the two-dimensional zinc-based complex are obtained:

[0040] As Figure 1 shown, the structure of the two-dimensional zinc-based complex of the present invention belongs to the hexagonal crystal system, space group P-3. The basic building unit is a tetra-nuclear zinc-oxygen cluster (Zn4O). Each zinc atom and the surrounding oxygen atoms together form a tetrahedral structure, and these tetrahedrons are interconnected by 4,4'-(2,2-di-p-tolylethylene-1,1-diyl) dibenzoic acid ligands. Its unit cell parameters are the axial length axial angles α = β = 90°, γ = 120°, and the unit cell volume is Z = 6.

[0041] As Figure 2 shown, the colorless transparent crystal-like two-dimensional zinc-based complex is subjected to experimental powder X-ray diffraction (PXRD). The X-ray powder analyzer is from PANalytical B.V. of the Netherlands, and the instrument model is X-Pert PRO MPD. The test results show that the colorless transparent crystal-like two-dimensional zinc-based complex is similar to the simulated PXRD pattern calculated from Mercury software, indicating high sample purity and crystallinity.

[0042] As Figure 3 shown, the colorless transparent crystal-like two-dimensional zinc-based complex is subjected to thermogravimetric curve analysis. The thermogravimetric test is carried out on a Mettler Toledo synchronous thermogravimetric analyzer, and the machine model is RGA / DSC-1. The reaction gas and the protective gas are both nitrogen, with flow rates of 25 mL / min respectively, the running time is 50 minutes, the heating rate is 10 K / min, and the test temperature range is 40 - 900 °C. From Figure 4 the thermogravimetric curve, it can be known that the two-dimensional zinc-based complex can be stable up to about 480 °C, and the two-dimensional zinc-based complex decomposes after 480 °C. This shows that the two-dimensional zinc-based complex of the present invention has good stability and can decompose at high temperatures.

[0043] As Figure 4 shown, the colorless transparent crystal-like two-dimensional zinc-based complex is exchanged three times with high-performance liquid chromatography methanol and high-performance liquid chromatography dichloromethane respectively, and degassed under vacuum at 80 °C for 5 hours to obtain the N2 adsorption isotherm at 77 K.

[0044] AsFigure 5 and Figure 6 As shown in Figure 6 , the colorless transparent crystalline two-dimensional zinc-based complex was tested by the ASAP 2020 instrument of Micromeritics Instrument Corporation in the United States. The two-dimensional zinc-based complex exhibited the adsorption isotherms shown in the figure for light hydrocarbons composed of C2H2, C2H4, and C2H6. The adsorption amounts of C2H2, C2H4, and C2H6 at 273K were 46.31 cm 3 / g, 43.95 cm 3 / g, 38.82 cm 3 / g, and the adsorption amounts of C2H2, C2H4, and C2H6 at 298K were 41.62 cm 3 / g, 38.87 cm 3 / g, 33.18 cm 3 / g. Therefore, from the differential adsorption amounts in the figure, it can be known that the two-dimensional zinc-based complex can be applied to the field of gas adsorption and separation.

[0045] As Figure 7 and Figure 8 shown, the colorless transparent crystalline two-dimensional zinc-based complex was tested by the ASAP 2020 instrument of Micromeritics Instrument Corporation in the United States. The two-dimensional zinc-based complex exhibited the adsorption isotherms shown in the figure for light hydrocarbons of n-C4H 10 and iso-C4H 10 . The adsorption amounts of n-C4H 10 and iso-C4H 10 at 273K were 209.05 cm 3 / g, 189.21 cm 3 / g, and the adsorption amounts of n-C4H 10 and iso-C4H 10 at 298K were 168.50 cm 3 / g, 154.19 cm 3 / g. Therefore, from the differential adsorption amounts in the figure, it can be known that the two-dimensional zinc-based complex can be applied to the field of gas adsorption and separation.

[0046] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A stimulus-responsive flexible two-dimensional zinc-based coordination complex, characterized in that: The structural unit is [Zn2(OH)2(H2L1)4], where Zn is a divalent zinc ion and H2L1 represents the ligand: 4,4'-(2,2-di-p-tolylethylene-1,1-diyl)dibenzoic acid. Among them, the two-dimensional zinc-based coordination complex structure belongs to the hexagonal crystal system, space group P-3, and its unit cell parameters are the axial lengths The axial angles α = β = 90°, γ = 120°, and the unit cell volume is Z = 6..

2. A preparation method of the two-dimensional zinc-based complex as described in claim 1, characterized in that, It includes the following steps: A. Dissolve zinc nitrate hexahydrate (Zn(NO3)2·6H2O) and the ligand H2L1 in a solvent, and stir and ultrasonically dissolve to obtain a homogeneous and clear mixed solution. Among them, the molar dosage ratio of the H2L1 ligand to Zn(NO3)2·6H2O is 1:(1-3), and the concentration of the H2L1 ligand in the solution is 0.01-0.03 mmol / L. B. Place the mixed solution described in step A in a glass bottle, and use the solvothermal method to place the glass bottle in a constant temperature static reaction at 90-100 °C for 3-5 days under closed conditions, and then slowly cool to room temperature. The product is filtered, washed, and dried to obtain the two-dimensional zinc-based complex.

3. The preparation method of the two-dimensional zinc-based coordination compound according to claim 2, wherein The solvent is composed of N,N-dimethylformamide, absolute ethanol, and deionized water, and the volume ratio of N,N-dimethylformamide, absolute ethanol, and water is 2:1:

1.

4. The preparation method of the two-dimensional zinc-based complex according to any one of claims 2 or 3, characterized in that, The molar dosage ratio of the H2L1 ligand to Zn(NO3)2·6H2O is 1:1.5, and the concentration of the H2L1 ligand in the solution is 0.02 mmol / L.

5. Use of a stimulus-responsive flexible two-dimensional zinc-based complex as described in claim 1 in the field of low-carbon hydrocarbon gas separation, characterized in that, The described two-dimensional zinc-based complex is used for adsorption tests on light hydrocarbons such as acetylene (C2H2), ethylene (C2H4), ethane (C2H6), n-butane (n-C4H 10 ), and isobutane (iso-C4H 10 ) to obtain differential adsorption amounts for adsorption separation.

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