Preparation method of flexible two-dimensional zinc-based complex and application thereof in low carbon hydrocarbon separation

Abstract

The application belongs to the technical field of new materials, and particularly relates to a zinc-based complex and a preparation method and application thereof. The chemical general formula is [Zn3(TMTA)3(DPP).DMF.H2O], wherein Zn is a divalent zinc ion, TMTA is a deprotonated 4,4',4''-(2,4,6-trimethylbenzene-1,3,5) tribenzoic acid ligand, and DPP is a 4-(2,5-difluoro-4-bromophenyl) pyridine ligand. The zinc-based complex structure belongs to a triclinic system, a P-1 space group, the cell parameter is a, the axial angle alpha is 60.225(9)°, the axial angle beta is 73.437(8)°, the axial angle gamma is 84.579(7)°, the cell volume is V, and Z is 2. The zinc-based complex can be used for preparing adsorption materials, antibacterial materials, catalytic materials, photoelectric magnetic materials and drug carrier materials, belongs to a metal-organic framework structure, and is a composite functional porous material with great potential. The zinc-based complex can be applied to the field of low-carbon hydrocarbon gas separation.

Description

Technical Field

[0001] This invention belongs to the field of new materials technology, specifically relating to a method for preparing a flexible two-dimensional zinc-based complex and its application in the separation of low-carbon hydrocarbons. Background Technology

[0002] Nanostructured materials exhibit superior performance in many aspects due to their structural characteristics. In the past two decades, a class of organic-inorganic hybrid nanoporous materials known as "metal-organic frameworks (MOFs)" has received widespread attention, becoming one of the research hotspots and frontiers in the field of new materials. MOF materials have attracted widespread attention due to their unique and excellent properties, and have been applied in materials science, chemistry, and other fields. Currently, in materials synthesis, the focus has shifted from finding new structures to application-oriented precision synthesis. MOF materials have become a new generation of functional materials following zeolites and activated carbon. There are two main methods for preparing functional MOF materials: one is to anchor functional groups onto the framework through post-modification, endowing it with specific functionality; the other is to directly prepare functional framework materials by pre-designing and synthesizing functional building block ligands. This bottom-up pre-modification method allows the target functional groups to be precisely distributed on the framework of the material, which is beneficial for controlling the position and number of active sites and effectively avoiding the destruction of material structure and porosity by modifying functional groups on the framework.

[0003] Compared to porous adsorbents such as molecular sieves and activated carbon, MOF materials exhibit unique advantages in gas adsorption and separation due to their customizable framework and diverse pore structures. Adsorption is an exothermic process, and rigid porous structures struggle to dissipate the binding energy generated during adsorption, thus hindering adsorption capacity. Flexible MOFs, whose structure is altered by changes in the guest medium, pressure, or temperature, are more likely to undergo structural changes to offset this energy, thus holding great potential in challenging separation processes. Therefore, flexible porous structures are expected to become the preferred material for separating and purifying olefins from binary or even multi-component mixtures.

[0004] To date, the design of flexible MOFs for binary and ternary gas separation has shown great promise. In recent years, many publications have reported the synthesis methods of flexible MOFs and their applications in gas separation. For example, Qiubing Dong, Xin Zhang, Shuang Liu, Angew. Chem. Int. Ed. 2020, 59, pp 22756-22762 constructed NTU-65 using 1,4-bis(1H-imidazol-1-yl)benzene and Cu(SiF6)·6H2O. At a specific temperature, NTU-65 can adsorb large amounts of C2H2 and CO2, while the adsorption of C2H4 is negligible, thus achieving one-step purification of C2H4; In 2021, Mohana Shivanna, Ken-ichi Otake, Bai-Qiao Song, Angew. Chem. Int. Ed. 2021, 6, pp 20383-20390, 1,2-bis(4-pyridyl)ethane and ZnSiF6 were used. 2- ZNU-5 exhibits a rapid adsorption capacity for C2H2 under low pressure and can selectively separate C2H4 / CO2 / C2H2. Lingyao Wang, Nuo Xu, Yongqi Hu, Nano Res. 2023, 16, pp 3536–3541. ZNU-5 was synthesized using 1,4-bis(1H-imidazol-1-yl)benzene, (NH4)2TiF6, and Cu(NO3)2·3H2O. ZNU-5 possesses high C2H2 adsorption capacity and exhibits good selectivity for separating C2H2 / CO2, C2H2 / C2H4, and C2H2 / CH4 at room temperature.

[0005] The strategies used to construct the aforementioned flexible coordination compounds all involve ligand torsion; no case has been reported of using a pillared ligand tailoring strategy to design and synthesize flexible two-dimensional MOFs. In other words, a flexible two-dimensional coordination compound synthesized using a pillared ligand tailoring strategy is lacking. Summary of the Invention

[0006] To address the technical problems mentioned above, this invention provides a method for synthesizing flexible two-dimensional zinc-based complexes using a tailoring strategy for pillared ligands.

[0007] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: a zinc-based complex with the general chemical formula [Zn3(TMTA)2(DPP)·DMF·H2O], wherein Zn is a divalent zinc ion, TMTA is a deprotonated 4,4',4”-(2,4,6-trimethylbenzene-1,3,5)tribenzoic acid ligand, and DPP is a 4-(2,5-difluoro-4-bromophenyl)pyridine ligand;

[0008] The zinc-based complex structure belongs to the triclinic crystal system, space group P-1, and its unit cell parameter is the axial length. Axis angle α=60.225(9)°, β=73.437(8)°, γ=84.579(7)°, Z=2.

[0009] The beneficial effects of this invention are: the zinc-based complex of this invention can be used to prepare adsorbent materials, antibacterial materials, catalytic materials, photoelectric materials, and drug carrier materials. The zinc-based complex of this invention belongs to a metal-organic framework structure, which is a highly promising composite functional porous material. The zinc-based complex crystals of this invention were tested at 293K using an Agilent Technologies SuperNova micro-focal spot X-ray single-crystal diffractometer, and data was received on an EosCCD. A graphite monochromator was used, with λ(CuKα) as... Data analysis and absorption correction were performed using CrysAlisPro 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. Anisotropy was applied to all non-hydrogen atoms, and hydrogen atoms in the organic ligands were generated through geometric symmetry (CH). The zinc-based complex structure obtained in this invention belongs to the triclinic crystal system, space group P-1. The basic structural unit of the crystal is obtained by symmetry operations on asymmetric units, and the symmetry opcode is . 1 +X,+Y,-1+Z; 2 +X,-1+Y,+Z; 3 +X,1+Y,+Z; 4 +X,+Y,1+Z.

[0010] The asymmetric unit consists of a deprotonated ligand TMTA, a ligand DPP, three zinc ions, and a coordinated water molecule.

[0011] The zinc ion is connected to four atoms in a four-coordinate mode. The four atoms connected to Zn1 are oxygen atoms (O2) from four carboxylate groups (O2-C1-O2) from three different ligands, and one oxygen atom (O1) from a water molecule. The four atoms connected to Zn2 are oxygen atoms (O2) from four carboxylate groups (O2-C1-O2) from three different ligands, and one nitrogen atom (N1) from the DPP ligand. The carboxylate groups (O2-C1-O2) in the ligands connect to adjacent Zn ions in a bidentate bridging mode, ultimately forming a binuclear [Zn3(TMTA)2(DPP)·DMF·H2O] structure. The zinc-based complex structure belongs to the triclinic crystal system, space group P-1, and its unit cell parameter is y = y = y = y. Axis angle α=60.225(9)°, β=73.437(8)°, γ=84.579(7)°, Z=2.

[0012] This invention also provides a method for preparing a zinc-based complex, comprising the following steps:

[0013] A. A homogeneous mixed solution was obtained by dissolving 4,4',4”-(2,4,6-trimethylbenzene-1,3,5)tribenzoic acid ligand, 4-(2,5-difluoro-4-bromophenyl)pyridine ligand, and zinc nitrate hexahydrate in a solvent. The molar ratio of 4,4',4”-(2,4,6-trimethylbenzene-1,3,5)tribenzoic acid ligand, 4-(2,5-difluoro-4-bromophenyl)pyridine to zinc nitrate hexahydrate was 1:20:12.8. The concentrations of 4,4',4”-(2,4,6-trimethylbenzene-1,3,5)tribenzoic acid ligand and 4-(2,5-difluoro-4-bromophenyl)pyridine ligand in the solution were 0.0054 mmol / L and 0.064 mmol / L, respectively.

[0014] B. Place the mixed solution described in step A in a glass bottle and keep it at 90°C for 24–48 hours to obtain the zinc-based complex.

[0015] 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 the zinc-based complex of this invention has high yield, requires less ligand, and saves costs.

[0016] Based on the above technical solution, the present invention can be further improved as follows.

[0017] Furthermore, the solvent is composed of N,N-dimethylformamide, ethanol, and water, and the volume ratio of N,N-dimethylformamide, ethanol, and water is 5:2:1.

[0018] The advantages of adopting the above-mentioned further scheme are that the solvent composed of N,N-dimethylformamide, ethanol and water is readily available, inexpensive and causes little pollution.

[0019] Furthermore, the molar ratio of the 4,4',4”-(2,4,6-trimethylbenzene-1,3,5)tribenzoic acid ligand, the 4-(2,5-difluoro-4-bromophenyl)pyridine ligand, and the zinc nitrate hexahydrate is 0.054:1.1:0.64, and the concentrations of the 4,4',4”-(2,4,6-trimethylbenzene-1,3,5)tribenzoic acid ligand and the 4-(2,5-difluoro-4-bromophenyl)pyridine ligand in the solution are 0.0054 mmol / L and 0.064 mmol / L, respectively.

[0020] The advantages of adopting the above-mentioned further scheme are that the determined concentration and molar amount result in a zinc-based complex with better quality and a smoother reaction.

[0021] This invention also provides an application of a zinc-based complex in the field of low-carbon hydrocarbon gas separation. The zinc-based complex is used to perform adsorption tests on low-carbon hydrocarbons composed of CO2, C2H2, C2H4 and C2H6 to obtain differentiated adsorption amounts for adsorption separation.

[0022] The beneficial effects of this invention are: the zinc-based complex is applied in the field of low-carbon hydrocarbon gas separation, making the functions of the zinc-based flexible complex more comprehensive. Attached Figure Description

[0023] Figure 1 This is a structural diagram of the asymmetric structural unit of the zinc-based complex of the present invention;

[0024] Figure 2 This is a structural diagram of the zinc-based complex of the present invention;

[0025] Figure 3 This is a thermogravimetric curve of the zinc-based complex of the present invention, with the horizontal axis representing temperature and the vertical axis representing the percentage of weight loss.

[0026] Figure 4 The infrared spectrum of the zinc-based complex of the present invention is shown below. The horizontal axis represents wavenumber and the vertical axis represents transmittance.

[0027] Figure 5 The graph shows the adsorption isotherms of the zinc-based complex of the present invention for CO2, C2H2, C2H4 and C2H6 at 195 K. The horizontal axis represents pressure and the vertical axis represents the amount of adsorption.

[0028] Figure 6 The graph shows the adsorption isotherms of the zinc-based complex of the present invention for CO2, C2H2, C2H4 and C2H6 at 273 K. The horizontal axis represents pressure and the vertical axis represents the amount of adsorption.

[0029] Figure 7 The graph shows the adsorption isotherms of the zinc-based complex of the present invention for CO2, C2H2, C2H4 and C2H6 at 298 K. The horizontal axis represents pressure and the vertical axis represents the amount of adsorption.

[0030] Figure 8 The graph shows the dynamic penetration test of the zinc-based complex of the present invention against C2H2 / C2H4 (v / v = 1:99) at 195K. The horizontal axis represents time, and the vertical axis represents relative concentration.

[0031] Figure 9 The graph shows the dynamic penetration test of the zinc-based complex of the present invention against CO2 / C2H4 (v / v = 10:90) at 195 K. The horizontal axis represents time, and the vertical axis represents relative concentration.

[0032] Figure 10 The graph shows the dynamic breakthrough experiment of the zinc-based complex of the present invention against C2H2 / C2H4 / CO2 (v / v / v=1:98:1) at 195K. The horizontal axis represents time and the vertical axis represents relative concentration.

[0033] Figure 11 The graph shows the dynamic penetration test of the zinc-based complex of the present invention against C2H2 / C2H4 (v / v = 1:99) at 298K. The horizontal axis represents time, and the vertical axis represents relative concentration.

[0034] Figure 12 The graph shows the dynamic penetration test of the zinc-based complex of the present invention against C2H2 / C2H4 (v / v = 50:50) at 298K. The horizontal axis represents time, and the vertical axis represents relative concentration.

[0035] Figure 13 The graph shows the dynamic penetration test of the zinc-based complex of the present invention against C2H2 / CO2 (v / v = 50:50) at 298K. The horizontal axis represents time, and the vertical axis represents relative concentration.

[0036] Figure 14 The graph shows the dynamic breakthrough experiment of the zinc-based complex of the present invention against C2H2 / C2H4 / CO2 (v / v / v=1:98:1) at 298K. The horizontal axis represents time, and the vertical axis represents relative concentration. 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 a zinc-based complex specifically includes the following steps:

[0040] A. Using an analytical balance, accurately weigh 0.0026 g and 0.0054 mmol of 4,4',4”-(2,4,6-trimethylbenzene-1,3,5)tribenzoic acid ligand, 0.03 g and 0.11 mmol of 4-(2,5-difluoro-4-bromophenyl)pyridine ligand, and 0.0189 g and 0.064 mmol of zinc nitrate hexahydrate into a reaction vessel. At room temperature, add 1 mL of a mixed solvent consisting of N,N-dimethylformamide, ethanol, and water, with a volume ratio of 5:2:1.

[0041] B. Place the mixed solution from step A in a glass bottle and keep it in a constant temperature blower at 90°C for 48 hours to obtain a colorless, transparent, blocky zinc-based complex.

[0042] The obtained colorless, transparent crystalline zinc-based complex was analyzed at 293 K using an Agilent SuperNova microspot 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 CrysAlisPro 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. Anisotropy was applied to all non-hydrogen atoms, and hydrogen atoms in the organic ligands were generated through geometric symmetry (CH). The crystal data are shown in Table 1, the typical bond length data are shown in Table 2, and the typical bond angle data are shown in Table 3. Tables 1, 2, and 3 are shown below:

[0043] Table 1: Crystal Data

[0044]

[0045]

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

[0047]

[0048]

[0049] Table 3: Typical bond angle data for crystals (unit: °)

[0050] O4 Zn1 O5 113.6(5) O4 Zn1 O9 115.1(5) O9 Zn1 O5 108.9(5) O1 Zn1 O4 112.2(6) O1 Zn1 O5 101.4(6) O1 Zn1 O9 104.5(6) N2 Zn2 O8 97.5(5) O7 Zn2 N2 107.9(5) O10 Zn2 N2 119.4(6) O10 Zn2 O7 125.7(6) O10 Zn2 O8 97.7(5)

[0051] like Figure 1 and Figure 2 As shown, the colorless, transparent crystalline zinc-based complex was measured at 293 K using an Agilent SuperNova micro-focal 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 CrysAlisPro 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. Anisotropy was applied to all non-hydrogen atoms, and hydrogen atoms in the organic ligands were generated through geometric symmetry (CH). Based on the crystal data in Tables 1, 2, and 3, the following characterizations of the zinc-based complexes were obtained:

[0052] The asymmetric unit consists of a quarter of a deprotonated ligand TMTA, a DPP ligand, a water molecule, a DMF molecule, and three zinc ions.

[0053] The zinc ion is connected to four atoms in a four-coordinate mode. The four atoms connected to Zn1 are oxygen atoms (O2) from four carboxylate groups (O2-C1-O2) from three different ligands, and one oxygen atom (O1) from a water molecule. The four atoms connected to Zn2 are oxygen atoms (O2) from four carboxylate groups (O2-C1-O2) from three different ligands, and one nitrogen atom (N1) from the DPP ligand. The carboxylate groups (O2-C1-O2) in the ligands connect to adjacent Zn ions in a bidentate bridging mode, ultimately forming a binuclear Zn3(TMTA)2(DPP)·DMF·H2O structure. Its unit cell parameter is the axial length. The axial angles α = 60.225(9)°, β = 73.437(8)°, γ = 84.579(7)°, and the unit cell volume is... Z = 2.

[0054] The zinc-based complex structure of this invention belongs to the triclinic crystal system, space group P-1. All carboxyl groups in H3TMTA are deprotonated and connected to adjacent Zn ions via bidentate bridging. Zn ions are connected to each other through carboxylic acid oxygen bridging to form binuclear secondary structural units. Adjacent secondary structural units are connected to each other through the three carboxyl groups of the ligand.

[0055] like Figure 3 As shown, thermogravimetric analysis (TGA) was performed on the colorless, transparent crystalline zinc-based complex. 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 min, the heating rate was 10 °C / min, and the test temperature range was 40–900 °C. Figure 3 The thermogravimetric curves show that the zinc-based complex is stable up to approximately 433°C. The complex loses its coordinating solvent at 200°C, and the weight loss between 200 and 370°C indicates partial decomposition of the ligands. The zinc-based complex decomposes after 433°C. This demonstrates that the zinc-based complex of this invention exhibits good stability and can decompose at high temperatures.

[0056] like Figure 4 As shown, the colorless, transparent crystalline zinc-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 4 It can be seen from the interior that the complex is located at 3424 cm. -1The nearby absorption peaks can be attributed to the stretching vibration peaks of OH in water, located between 1660 and 1614 cm⁻¹. -1 and 1412~1380cm -1 The nearby absorption peaks can be attributed to the antisymmetric and symmetric stretching vibrations of the carboxylate group, respectively.

[0057] like Figure 5 , Figure 6 and Figure 7 As shown, the colorless, transparent crystalline zinc-based complex was tested using an ASAP 2020 instrument from Micron Technology, USA. The zinc-based complex exhibited adsorption isotherms for low-carbon hydrocarbons composed of CO2, C2H2, C2H4, and C2H6, as shown in the figure. The adsorption capacities of CO2, C2H2, C2H4, and C2H6 at 195 K were 235.84 cm⁻¹, respectively. 3 / g, 317.83cm 3 / g, 165.22cm 3 / g and 165.18cm 3 / g. The isotherm of the zinc-based complex for C2H2 shows multi-step adsorption, a typical feature of flexible porous structures. The isotherm reaches the first adsorption plateau at P > 52 kPa. A second adsorption step occurs at P > 52 kPa, with a maximum adsorption capacity of 317.83 cm⁻¹ at 100 kPa. 3 / g. The adsorption capacities of CO2, C2H2, C2H4, and C2H6 at 273K were 64.97 cm⁻¹, respectively. 3 / g, 100.23cm 3 / g, 101.92cm 3 / g and 96.2cm 3 / g, the adsorption capacities of CO2, C2H2, C2H4, and C2H6 at 298K are 42.5 cm⁻¹, respectively. 3 / g, 87.13cm 3 / g, 67.89cm 3 / g and 74.16cm 3 / g. Therefore, the differential adsorption amounts shown in the figure indicate that the zinc-based complex can be applied in the field of gas adsorption and separation.

[0058] like Figure 8-14As shown, the colorless, transparent crystalline zinc-based complex was tested using a multi-component competitive adsorption breakthrough curve analyzer with a total gas flow rate of 2 mL / min. The zinc-based complex exhibited the separation effects shown in the figure for C2H2 / C2H4, C2H2 / CO2, C2H4 / CO2, and C2H2 / C2H4 / CO2. The separation times at 195 K for C2H2 / C2H4 (v:v = 1 / 99), CO2 / C2H4 (v:v = 10 / 90), and C2H2 / C2H4 / CO2 (v:v:v = 1 / 98 / 1) were 27.63 min / g, 35.23 min / g, and 37.39 min / g, respectively. The separation times of C2H2 / C2H4 (v:v=1 / 99), C2H2 / C2H4 (v:v=50 / 50), C2H2 / CO2 (v:v=50 / 50), and C2H2 / C2H4 / CO2 (v:v:v=1 / 98 / 1) at 298 K were 26.32 min / g, 22.89 min / g, 15.83 min / g, and 4.77 min / g, respectively.

[0059] 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 zinc-based complex, characterized in that: The chemical general formula is [Zn3(TMTA)2(DPP)·DMF·H2O], wherein, Zn is a divalent zinc ion, TMTA is a deprotonated 4,4',4"-(2,4,6-trimethylbenzene-1,3,5) triphenylcarboxylic acid ligand, and DPP is a 4-(2,5-difluoro-4-bromophenyl) pyridine ligand; The zinc-based complex structure belongs to triclinic system, P-1 space group, and the cell parameters are axis length Axis angle a = 60.225(9) °, b = 73.437(8) °, and g = 84.579(7) °.

2. A process for the preparation of a zinc-based complex according to claim 1, characterized in that, The method comprises the following steps: A. Dissolving 4,4',4"-(2,4,6-trimethylbenzene-1,3,5) triphenylcarboxylic acid ligand, 4-(2,5-difluoro-4-bromophenyl) pyridine ligand and zinc nitrate hexahydrate in a solvent to obtain a uniform mixed solution, the molar amount ratio of the 4,4',4"-(2,4,6-trimethylbenzene-1,3,5) triphenylcarboxylic acid ligand, 4-(2,5-difluoro-4-bromophenyl) pyridine ligand and zinc nitrate hexahydrate is 1:20:12.8, and the concentrations of the 4,4',4"-(2,4,6-trimethylbenzene-1,3,5) triphenylcarboxylic acid ligand and 4-(2,5-difluoro-4-bromophenyl) pyridine ligand in the solution are 0.0054 mmol / L and 0.064 mmol / L respectively; B. Placing the mixed solution in a glass bottle and incubating at 90°C for 24-48 hours to obtain the zinc-based complex.

3. Process for the preparation of a zinc complex according to claim 2, characterized in that, The solvent is composed of N,N-dimethylformamide, ethanol and water, and the volume ratio of the N,N-dimethylformamide, ethanol and water is 5:2:

1.

4. Process for the preparation of a zinc-based complex according to any one of claims 2 or 3, characterized in that, The molar amount ratio of the 4,4',4"-(2,4,6-trimethylbenzene-1,3,5) triphenylcarboxylic acid ligand, 4-(2,5-difluoro-4-bromophenyl) pyridine ligand and zinc nitrate hexahydrate is 0.054:1.1:0.64, and the concentrations of the 4,4',4"-(2,4,6-trimethylbenzene-1,3,5) triphenylcarboxylic acid ligand and 4-(2,5-difluoro-4-bromophenyl) pyridine ligand in the solution are 0.0054 mmol / L and 0.064 mmol / L respectively.

5. Use of a zinc-based complex according to claim 1 in the field of low carbon hydrocarbon gas separation, characterized in that, The zinc-based complex is subjected to adsorption test on low-carbon hydrocarbons composed of CO2, C2H2, C2H4 and C2H6 to obtain differential adsorption amount for adsorption separation.

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