Zinc-based complex as well as synthesis method and application thereof

Abstract

The invention belongs to the field of new materials, and relates to a zinc-based complex and a synthesis method and application thereof.The zinc-based complex is of a nano-sized three-dimensional network structure synthesized with pyridine-2, 4, 6-tribenzoic acid, tris (4-pyridyl) amine and zinc nitrate hexahydrate as raw materials, the molecular formula of the basic structural unit of the zinc-based complex is [Zn2 (DiO) (L)], and the molecular formula of the basic structural unit of the zinc-based complex is as shown in the specification. The complex is obtained by symmetric operation of the basic structural units. The complex contains a six-core cluster structure formed by combining six zinc with oxygen on a ligand, the ligand H3L-N is coordinated with zinc ions to form a cage-shaped structure, the size is 8.5, the complex is of a double interlaced structure through connection of the ligand H3L-N, the double interlaced structure forms a tightly interlocked topological network through two mutually interlaced but independent three-dimensional frames, and the three-dimensional structures are mutually interlaced and mutually interlaced and mutually interlaced and mutually interlaced and mutually interlaced and mutually interlaced and mutually interlaced and mutually interlaced and mutually interlaced and mutually interlaced and mutually interlaced. Compared with the prior art, the preparation method provided by the invention has the advantages that the stability of the complex is improved, oxygen atoms on the ligand can form hydrogen bonds with hydrogen on C2H2, so that the adsorption capacity is improved, relatively strong separation selectivity is shown in the aspect of C2H2 / CO2 separation application, and the synthesis method provided by the invention is simple in preparation process, green and efficient.

Description

Technical Field

[0001] The present invention belongs to the field of new materials, and in particular relates to a zinc-based complex and a synthesis method and application thereof. Background Art

[0002] Metal-organic frameworks (MOFs) materials have been a hot topic in the field of new materials research in recent years. Metal-organic framework materials, also known as porous coordination polymers (PCPs), are a type of crystalline material with a periodic network structure that is self-assembled by metal ions or metal clusters and multi-dentate organic ligands through coordination bond bridging. During the synthesis process, simple ligand metal clusters formed by metal ions and organic ligands cannot be used in the synthesis of network materials due to the lack of stable coordination directionality. In order to form a secondary structural unit with rigidity, the most common MOF material is to "couple" (coordinate) the metal ions with a bidentate through carboxyl groups, and use the carbon atoms of the carboxyl groups as extension points to define the secondary structural units. MOFs were originally used for gas storage because they have a high achievable surface area and a considerable porosity. At the beginning of the research, scientists mainly focused on increasing its surface area and pore size, but due to its low chemical stability and poor mechanical strength, researchers expanded the practical value of MOFs by modifying metal ions and organic ligands, and promoted its further development in gas storage, separation, catalysis, sensors and other fields.

[0003] Nitrogen-containing tricarboxylic acid ligands (such as H3TCA, H3BTC derivatives, etc.) have significant advantages in coordination chemistry and materials science. The three carboxylic acid groups (-COOH) provide multiple oxygen atom coordination sites and can form stable coordination bonds with metal ions (such as transition metals and rare earth metals). They are often coordinated in a bidentate or bridging manner to enhance the stability of the complex or framework structure. By adjusting the substituents or nitrogen atom positions of the ligand skeleton (such as benzene ring, triazine ring), the electronic effect and steric hindrance of the ligand can be controlled, thereby optimizing material properties (such as pore size and catalytic activity). In addition, the introduction of nitrogen may enhance the stability of the framework or introduce functional sites, such as catalytic active sites or gas adsorption sites.

[0004] The separation of acetylene (C2H2) and carbon dioxide (CO2) currently faces significant challenges. The core issue stems from the high similarity in their molecular properties (e.g., similar kinetic diameters, polarizabilities, and boiling points), which makes it difficult for traditional adsorbent materials to achieve efficient separation through size screening or polarity differences. Existing adsorbents often face the dilemma of balancing adsorption capacity and selectivity, and are susceptible to competitive adsorption interference in complex mixed systems (e.g., those containing impurities such as ethylene and sulfides), resulting in insufficient dynamic separation stability. In industrial applications, large-scale applications are further hampered by the high cost of material synthesis, high regeneration energy consumption, and the discrepancy between ideal laboratory conditions and actual operating conditions (e.g., impurity influences and pressure fluctuations).

[0005] Therefore, there is an urgent need to develop high-performance materials, optimize process coupling, and explore green and low-carbon technologies to achieve efficient separation of acetylene and carbon dioxide. Summary of the Invention

[0006] In response to the many shortcomings of the existing technology, the present invention provides a zinc-based complex, a synthesis method and application thereof. The zinc-based complex uses pyridine-2,4,6-tribenzoic acid (H3L-N), tri(4-pyridyl)amine (TPA) and zinc nitrate hexahydrate as raw materials to prepare a three-dimensional network framework material; the complex has the ability to separate C2H2 / CO2 binary mixtures, filling the gap in the field of constructing new zinc-based metal-organic framework complexes using pyridine-2,4,6-tribenzoic acid (H3L-N) as a ligand and its application in the separation of C2H2 / CO2. The provided synthesis method has a simple preparation process, is green and efficient.

[0007] The specific technical solutions of the present invention are as follows: A zinc-based complex, wherein the molecular formula of the basic structural unit is [Zn2(DiO)(L)], wherein Zn represents a divalent zinc ion, L represents a deprotonated pyridine-2,4,6-tribenzoate ligand, and DiO represents 1,4-dioxane.

[0008] Furthermore, the zinc-based complex belongs to the cubic crystal system Im-3 space group, and the crystal structure is obtained by symmetry operation of basic structural units (symmetry operation codes are -l / 2_x, +y, l / 2-z; 1-X, 1-y, lz; 3-x, 2-y, 1-z). The zinc ions and ligands form a three-dimensional network structure, in which the six zinc ions form a hexanuclear cluster with the oxygen atoms of the ligand and the oxygen atoms of 1,4-dioxane. The ligand H3L-N coordinates with the zinc ions to form a cage-like structure with a size of 8.5 Å. Furthermore, the connection of the ligand H3L-N gives the complex a doubly intercalated structure. This doubly intercalated structure forms a tightly interlocked topological network through two interwoven but independent three-dimensional frameworks, significantly enhancing the stability of the MOF. First, the physical interlocking between the frameworks enhances mechanical strength and effectively inhibits pore collapse or structural deformation. Second, the intercalation leads to a smaller pore size and forms multiple confined spaces, reducing the erosion of the framework by solvents or reactant molecules. Third, the abundant van der Waals forces and π-π interactions between adjacent frameworks further strengthen the overall structure, reducing defects caused by thermal vibration or external stress. This synergistic effect enables the MOF to maintain its structural integrity despite high temperatures, solvent immersion, or pressure fluctuations, thereby expanding its application potential in harsh environments.

[0009] The unit cell parameters of the zinc-based complex are: axis length a = 27.3477(18) Å, b = 27.3477(18) Å, c = 27.3477(18) Å, α = 90°, β = 90°, γ = 90°; the unit cell volume is V = 20453(4) Å 3 Z = 256. The hexanuclear cluster structural unit is composed of six divalent zinc ions, two 1,4-dioxanes, and coordinated oxygen atoms. The zinc ions have two coordination modes: one in which the zinc ions are connected to the oxygen atoms in a tetracoordinate manner, forming coordination bonds with two oxygen atoms from the carboxylates on the two pyridine-2,4,6-tribenzoic acid ligands, and the other two from oxygen atoms in water; the other in which the zinc ions are connected to the oxygen atoms in a hexacoordinate manner, forming coordination bonds with one oxygen from water, another from the oxygen on the 1,4-dioxane, and the remaining four from the oxygen atoms on the four carboxylic acid ligands, forming a symmetrical structure.

[0010] Furthermore, the inventors also provide a method for synthesizing the above zinc-based complex, the specific steps of which are as follows: The carboxylic acid ligand pyridine-2,4,6-tribenzoic acid (H3L-N), the modifier tris(4-pyridyl)amine (TPA) and zinc nitrate hexahydrate are added to a mixed solution of N,N-dimethylacetamide (DMA), 1,4-dioxane (DiO) and water, and ultrasonically treated at room temperature. The mixture is placed in a reaction vessel, stirred at room temperature on a magnetic stirrer, and then transferred to an oven and heated to 100°C. The mixture is kept at 100°C for 24-36 hours to obtain the zinc-based complex.

[0011] The pyridine-2,4,6-tribenzoic acid used herein has a CAS number of 107063-53-6 and a structural formula as shown in Formula I: Formula I.

[0012] The tri(4-pyridyl)amine used has a CAS number of 153467-50-6 and a structural formula as shown in Formula II: Formula II; The molar ratio of the pyridine-2,4,6-tribenzoic acid, tri(4-pyridyl)amine and zinc nitrate hexahydrate is 1:1:4-6.

[0013] The volume ratio of N,N-dimethylacetamide (DMA), 1,4-dioxane and water in the mixed solution is 5:2:1.

[0014] The concentration of the pyridine-2,4,6-tribenzoic acid in the mixed solution of DMA, 1,4-dioxane and water is 1.46 g / L; the concentration of the zinc nitrate hexahydrate in the mixed solution of DMA, 1,4-dioxane and water is 3.97-5.96 g / L.

[0015] The ultrasonic treatment was carried out at 60 Hz for 30 min; the magnetic stirring was carried out at 60 Hz for 12 h; and the heating rate in the oven was 10° C. / min.

[0016] The regulator 1,4-dioxane can regulate the growth of crystals and promote crystallization.

[0017] The zinc-based complex prepared in this invention was cleaned with DMA, then subjected to solvent exchange with methanol and dichloromethane, and subjected to vacuum removal of organic molecules (a process known as activation). The resulting material exhibited distinct adsorption differences between C2H2 and CO2, with a preference for C2H2. The separation capacity of a C2H2 / CO2 binary mixture was predicted using ideal adsorption solution theory (IAST), yielding an IAST selectivity of approximately 2.55, demonstrating potential for practical separation.

[0018] Compared with the prior art, the zinc-based complex and its synthesis method provided by the present invention have the following advantages: (1) The ligand selected in the present invention contains nitrogen, which increases the adsorption sites, and the structure is doubly interpenetrated, which improves the stability of the structure, filling the gap in the construction of new zinc-based metal-organic framework complexes with pyridine-2,4,6-tribenzoic acid (H3L-N) as a ligand and its application in the separation of C2H2 / CO2.

[0019] (2) The zinc-based complex prepared by the present invention contains a hexanuclear cluster structure formed by six zinc atoms combined with ligands, which improves the stability of the complex. At the same time, the oxygen atoms on the ligand can form hydrogen bonds with the hydrogen on C2H2, thereby increasing the adsorption capacity. Therefore, it shows strong separation selectivity in C2H2 / CO2 separation applications, expands the crystallographic structure data of zinc-based complexes, helps to study the assembly mechanism of zinc-based complexes, promotes industrial-scale production, and has guiding significance for the expansion of applications in gas adsorption and separation.

[0020] (3) The synthetic method provided is simple in preparation, environmentally friendly, and has a high yield. It is also of great value in expanding the application of zinc-based complexes in catalysis, fluorescence recognition, opto-electromagnetic materials, and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the basic structural unit of the zinc-based complex prepared in Example 1; Figure 2 Schematic diagram of the crystal structure of the zinc-based complex prepared in Example 1; Figure 3 Schematic diagram of the hexanuclear cluster structure in the zinc-based complex prepared in Example 1; Figure 4 Schematic diagram of the doubly intercalated topological structure of the zinc-based complex prepared in Example 1; Figure 5 This is the thermogravimetric curve of the zinc-based complex prepared in Example 1; Figure 6 This is the infrared spectrum of the zinc-based complex prepared in Example 1; Figure 7 This is a graph showing the single-component adsorption of C2H2 / CO2 at 298 K for the zinc-based complex prepared in Example 1; Figure 8 This is the IAST selectivity diagram of the zinc-based complex prepared in Example 1 at 298 K in a C2H2 / CO2 mixed gas (volume ratio of 50:50); Figure 9 This is the penetration diagram of the zinc-based complex prepared in Example 1 under the conditions of 298 K and C2H2 / CO2 mixed gas (volume ratio of 50:50). DETAILED DESCRIPTION

[0022] The present invention is further illustrated below with reference to the examples, which will help those skilled in the art to further understand the present invention, but will not limit the present invention in any form. It should be noted that, for those skilled in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. The experimental methods described in the following examples, unless otherwise specified, are all conventional methods; the instruments and drugs used, unless otherwise specified, can be obtained through normal commercial channels.

[0023] Example 1 A method for synthesizing a zinc-based complex comprises the following steps: The reactants, pyridine-2,4,6-tribenzoic acid, tri(4-pyridyl)amine and zinc nitrate hexahydrate, were added in a molar ratio of 1:1:6; 4.39 mg of the carboxylic acid ligand pyridine-2,4,6-tribenzoic acid, 2.48 mg of the modulator tri(4-pyridyl)amine, and 17.84 mg of zinc nitrate hexahydrate were accurately weighed using an analytical balance and added to a 10 mL glass vial. 3 mL of a mixed solvent (DMA, 1,4-dioxane, and H2O in a volume ratio of 5:2:1) was added, and the mixture was sonicated at 60 Hz at room temperature for 30 min. The mixture was placed in a glass vial and stirred on a magnetic stirrer at 60 Hz at room temperature for 12 h. The mixture was then transferred to an oven and heated to 100°C at a rate of 10°C / min. The mixture was kept at 100°C for 24-36 h to obtain the zinc-based complex with a yield of 46.9%.

[0024] Example 2 A method for synthesizing a zinc-based complex comprises the following steps: The reactants, pyridine-2,4,6-tribenzoic acid, tri(4-pyridyl)amine and zinc nitrate hexahydrate, were added in a molar ratio of 1:1:4; 4.39 mg of the carboxylic acid ligand pyridine-2,4,6-tribenzoic acid, 2.48 mg of the modulator tri(4-pyridyl)amine, and 11.90 mg of zinc nitrate hexahydrate were accurately weighed using an analytical balance and added to a 10 mL glass vial. 3 mL of a mixed solvent (DMA, 1,4-dioxane, and H2O in a volume ratio of 5:2:1) was added, and the mixture was ultrasonically treated at 60 Hz at room temperature for 30 min. The mixture was placed in a glass vial and stirred on a magnetic stirrer at 60 Hz at room temperature for 12 h. The mixture was then transferred to an oven and heated to 100°C at a heating rate of 10°C / min. The mixture was kept at 100°C for 24-36 h to obtain the zinc-based complex with a yield of 54.3%.

[0025] The structure of the zinc-based complex prepared in this example is consistent with that obtained in Example 1.

[0026] The zinc-based complex prepared in Example 1 has a basic structural unit having the molecular formula [Zn2(DiO)(L)], wherein Zn represents a divalent zinc ion, L represents a deprotonated pyridine-2,4,6-tribenzoate ligand, and DiO represents 1,4-dioxane.

[0027] like Figure 1-3 As shown in Table 1-3, the complex belongs to the cubic Im-3 space group, where Figure 2 The crystal structure shown is derived from Figure 1 The basic structural unit shown is obtained by symmetry operation (symmetry operation code is -l / 2_x, +y, l / 2-z; 1-X, 1-y, lz; 3-x, 2-y, 1-z). The zinc ion coordinates with the ligand to form a three-dimensional network structure, such as Figure 3 As shown, the six metal zinc ions form a hexanuclear cluster structure with the oxygen atoms of the ligand and the oxygen on the 1,4-dioxane ring, and the ligand H3L-N coordinates with the metal zinc ions to form a cage structure with a size of 8.5 Å; secondly, the connection of the ligand H3L-N makes the complex a two-fold interpenetrating structure, and the two-fold interpenetrating structure forms a tightly interlocked topological network through two interwoven but independent three-dimensional frameworks. Figure 4 Schematic diagram of the topological structure of the complex. It can be seen from the figure that the complex is a doubly interpenetrating structure.

[0028] The unit cell parameters are: axis length a = 27.3477(18) Å, b = 27.3477(18) Å, c = 27.3477(18) Å, α = 90°, β = 90°, γ = 90°; the unit cell volume is V = 20453(4) Å 3 ; Z = 256. The ligand H3L-N coordinates with the zinc ion to form a cage-like structure with a size of 8.5 Å.

[0029] The single crystal structure was collected at room temperature using a Bruker Apex2 Smart CXD surface detector. Absorption correction was performed using a graphite monochromator with a λ (Mo Kα) of 0.71073 Å and a variable ω-2θ scanning mode using the multiscan program SADABS. The crystal structure was solved by direct methods using the Sir97 program; the F2 structure was refined using the SHELXL-97 program using full-matrix least-squares methods. Anisotropic refinement was performed for all non-hydrogen atoms. Hydrogen atoms of organic ligands were generated by geometric symmetry (C-H 0.96 Å).

[0030] TGA and infrared spectra are attached. Figure 5 、 Figure 6 ,from Figure 5It can be seen that the complex remains stable within 200 ℃, the solvent is removed after 200 ℃, and the structure collapses after 400 ℃. Figure 6 It can be seen that 1450 cm -1 The absorption peaks near 1690-1605 cm are derived from the stretching vibration of pyridine in the ligand. -1 and 1440-1330 cm -1 The absorption peaks near 3000 cm are derived from the antisymmetric and symmetric stretching vibration peaks of the carboxyl group in the ligand; -1 The nearby absorption peaks originate from the absorption peaks of CH on the benzene ring in the ligand.

[0031] Table 1 Crystal data

[0032] Table 2 Typical bond length data of crystals (unit: Å)

[0033] Table 3 Typical bond angle data of crystals (unit: °)

[0034] Application Example 1 The adsorption performance of the zinc-based complex for C2H2 and CO2 is tested. The specific steps are as follows: Take 100 mg of the zinc-based complex prepared in Example 1, wash the crystals with DMA, and then perform solvent exchange with fresh chromatographic methanol (three exchanges, 6 hours each soak). Repeat the solvent exchange with fresh chromatographic dichloromethane under the same operating conditions. Transfer the zinc-based complex to an adsorption tube and degas under vacuum at 120°C for 10 hours to obtain 95.8 mg of activated sample.

[0035] The activated sample was placed in a 25°C constant temperature water bath to maintain a constant system temperature. Under the same conditions, the single-component pressure swing adsorption curves of C2H2 and CO2 were measured in sequence using a JW-BK200 microporous analyzer (pressure range 0-110 kPa). A glass rod was placed in the adsorption tube, which was installed on the analysis station to measure the adsorption curve at 298 K. The experimental results are shown in Figure 2. Figure 7 As shown, it can be clearly seen that the complex has obvious adsorption differences for the two gases.

[0036] Figure 8 The IAST selectivity of the zinc-based complex prepared in Example 1 for a C2H2 / CO2 mixed gas (volume ratio of 50:50) at 25°C is 2.55, calculated based on the ideal adsorption solution theory, and can be used for the separation of C2H2 / CO2.

[0037] 0.5 g of the activated sample was loaded into a penetration column filled with quartz wool and a penetration test was performed using a BSD-MAB analyzer at 298 K. After the penetration test, helium was passed through the adsorbent at a flow rate of 15 mL / min at 393 K and regenerated at 393 K for 4 h to ensure complete desorption of the adsorbed gas. Figure 9 It can be seen that the separation time of C2H2 / CO2 is 5 min, indicating that the material can effectively separate acetylene and carbon dioxide.

[0038] 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 zinc-based complex, characterized in that The molecular formula of its basic structural unit is [Zn2(DiO)(L)], wherein Zn represents a divalent zinc ion, L represents a deprotonated pyridine-2,4,6-tribenzoate ligand, and DiO represents 1,4-dioxane; the crystal structure of the zinc-based complex is obtained through symmetry operations of the basic structural unit.

2. The zinc-based complex according to claim 1, characterized in that The zinc-based complex belongs to the cubic Im-3 space group, and the zinc ions coordinate with the ligands to form a three-dimensional network structure, wherein the six zinc ions form a hexanuclear cluster structure with the oxygen atoms of the ligands and the oxygen on the 1,4-dioxane, and the ligand H3L-N coordinates with the zinc ions to form a cage structure with a size of 8.5Å; the connection of the ligand H3L-N makes the complex a two-fold interpenetrating structure, and the two-fold interpenetrating structure forms a tightly interlocked topological network through two interwoven but independent three-dimensional frameworks; the unit cell parameters of the zinc-based complex are: axis length a = 27.3477(18) Å, b = 27.3477(18) Å, c = 27.3477(18) Å, α = 90°, β = 90°, γ = 90°; the unit cell volume is V = 20453(4) Å 3 ; Z=256; The hexanuclear cluster structural unit is composed of six divalent zinc ions, two 1,4-dioxanes, and coordinated oxygen atoms, wherein the zinc ions have two coordination modes. One zinc ion is connected to the oxygen atom by forming a coordination bond in a four-coordinate manner, wherein two oxygens come from the carboxylic acids on the two pyridine-2,4,6-tribenzoic acid ligands, and the other two are oxygens in water; the other zinc ion is connected to the oxygen atom by forming a six-coordinate bond, wherein one is oxygen in water, another comes from the oxygen on 1,4-dioxane, and the remaining four come from the oxygens on the four carboxylic acid ligands, forming a symmetrical structure.

3. The method for synthesizing the zinc-based complex according to claim 1 or 2, characterized in that: The specific steps are as follows: adding a carboxylic acid ligand pyridine-2,4,6-tribenzoic acid ligand, a tris(4-pyridyl)amine regulator and zinc nitrate hexahydrate to a mixed solution of N,N-dimethylacetamide, 1,4-dioxane and water, and ultrasonically treating the mixture at room temperature; placing the mixture in a reaction vessel, placing it on a magnetic stirrer to stir the reaction at room temperature, transferring it to an oven and heating it to 100°C, and keeping it at 100°C for 24-36 hours to obtain the zinc-based complex.

4. The method for synthesizing the zinc-based complex according to claim 3, wherein The molar ratio of the pyridine-2,4,6-tribenzoic acid, tri(4-pyridyl)amine and zinc nitrate hexahydrate is 1:1:4-6.

5. The method for synthesizing the zinc-based complex according to claim 3, wherein: The volume ratio of N,N-dimethylacetamide, 1,4-dioxane and water in the mixed solution is 5:2:

1.

6. The method for synthesizing the zinc-based complex according to claim 3, wherein: The concentration of the pyridine-2,4,6-tribenzoic acid in the mixed solution of DMA, 1,4-dioxane and water is 1.46 g / L; the concentration of the zinc nitrate hexahydrate in the mixed solution of DMA, 1,4-dioxane and water is 3.97-5.96 g / L.

7. The method for synthesizing the zinc-based complex according to claim 3, wherein: The ultrasonic treatment was carried out at 60 Hz for 30 min.

8. The method for synthesizing the zinc-based complex according to claim 3, wherein: The magnetic stirring was carried out at 60 Hz for 12 h.

9. The method for synthesizing the zinc-based complex according to claim 3, wherein: The heating rate in the oven is 10°C / min.

10. Use of the zinc-based complex according to claim 1 in C2H2 / CO2 separation.

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