Cobalt-based complex as well as preparation method and application thereof

Abstract

The invention belongs to the field of new materials, and particularly relates to a cobalt-based complex and a preparation method and application thereof.The cobalt-based complex is prepared by taking 1, 3, 5-tris (4-carboxyphenyl) benzene (BTB), 3, 5-dimethyl-4H-1, 2, 4-triazole (DMTA) and cobalt nitrate hexahydrate as raw materials, and a three-dimensional metal organic framework material with nanoscale pore channels is prepared; a basic asymmetric unit of the complex comprises one hexa-coordinated Co < 2 + >, one deprotonated BTB3 <-> ligand molecule, one coordinated DMTA ligand molecule and one coordinated water molecule; the ligand 1, 3, 5-tri (4-carboxyl phenyl) benzene, 3, 5-dimethyl-4H-1, 2, 4-triazole and Co < 2 + > coordinate with one another to obtain a three-dimensional pore channel structure with double interspersing, the complex has the capacity of separating a C2H2 / CO2 binary mixture, and the preparation method provided by the invention is simple in synthesis process, green and efficient.

Description

Technical Field

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

[0002] Acetylene (C2H2), a key raw material in the modern chemical industry, is irreplaceable in fields such as synthetic rubber, engineering plastics, pharmaceutical intermediates, and clean energy technologies. The industrial production of acetylene, such as through partial combustion of natural gas or cracking of hydrocarbons, inevitably produces a large amount of carbon dioxide (CO2) as a byproduct. However, acetylene and CO2 have very similar physicochemical properties, such as boiling point (C2H2, 189.3K; CO2, 194.7K), kinetic diameter (C2H2, 3.3 Å, CO2, 3.3 Å), and molecular size (C2H2, 3.34 × 3.32 × 5.70 Å). 3 , CO2, 3.33×3.18×5.36 Å 3 ), making C2H2 / CO2 separation a huge challenge.

[0003] Metal-Organic Frameworks (MOFs) are organic-inorganic hybrid materials formed by self-assembly of organic ligands and metal ions or metal ion clusters through coordination bonds. As a typical porous material, MOFs are characterized by ultra-high specific surface area, permanent porosity, and highly designable structure. Based on the self-assembly behavior of molecules, atoms with coordination ability are often used to construct new MOF structures. Due to the designability of MOFs structure, precise design can be achieved by tuning its pore structure. Therefore, it has a wide range of applications in gas adsorption / separation, drug delivery, chemiluminescence, and catalysis. In addition, MOFs have precise operability at the molecular level, and the material structure and application can be controlled by chemical methods. It is a basic material with great potential for application expansion.

[0004] However, MOFs still face the following challenges in the field of C2H2 / CO2 separation: First, due to the similar molecular size and polarity of the two, most MOFs lack selectivity, requiring the sacrifice of adsorption capacity in exchange for high selectivity; second, some highly selective MOFs are easily affected by moisture or impurities, causing structural collapse and poor chemical stability; third, research on dynamic separation performance is scarce, and breakthrough experimental data under actual industrial conditions are limited; fourth, the competitive adsorption mechanism is unclear, and there is a lack of systematic theoretical analysis of the preferential adsorption sites and interactions between C2H2 and CO2 within the pores. Therefore, a metal-organic framework complex that can effectively separate C2H2 / CO2 is urgently needed. Summary of the Invention

[0005] In response to the many deficiencies in the prior art, the present invention provides a cobalt-based complex, a preparation method, and an application thereof. The cobalt-based complex uses 1,3,5-tris(4-carboxyphenyl)benzene (BTB), 3,5-dimethyl-4H-1,2,4-triazole (DATZ), and cobalt nitrate hexahydrate as raw materials to prepare a three-dimensional metal-organic framework material with nanoscale pores. The complex has the ability to separate C2H2 / CO2 binary mixtures, filling the gap in the field of constructing new cobalt-based metal-organic framework complexes using 1,3,5-tris(4-carboxyphenyl)benzene and 3,5-dimethyl-4H-1,2,4-triazole dual ligands and their application in the separation of C2H2 / CO2. The provided preparation method has a simple synthesis process and is green and efficient.

[0006] The specific technical solutions of the present invention are as follows: A cobalt-based complex having the molecular formula [Co(BTB 3- )(DMTA)( H2O)], where Co represents divalent cobalt ion, BTB 3- represents the deprotonated 1,3,5-tris(4-carboxyphenyl)benzenecarboxylate ligand, DMTA represents 3,5-dimethyl-4H-1,2,4-triazole, and H2O represents a water molecule.

[0007] The complex belongs to the cubic Im-3 space group with unit cell parameters of: axis length a = b = c = 27.1743 Å; α = β = γ = 90°; unit cell volume is 20066.7 Å 3 ; Z=12.

[0008] The basic asymmetric unit contains a six-coordinated Co 2+ , a deprotonated BTB 3- ligand molecule, a coordinated DMTA ligand molecule and a coordinated water molecule. 2+ The coordination mode is hexacoordination, in which 4 coordinated oxygen atoms come from the oxygen atoms in the 4 carboxylic acid ligands, 1 coordinated oxygen atom comes from the oxygen atom in the solvent H2O, and 1 coordinated nitrogen atom comes from the nitrogen atom in 3,5-dimethyl-4H-1,2,4-triazole.

[0009] The unsaturated metal sites in the complex provide strong binding sites, which can promote the preferential adsorption of acetylene by the material. The two functionalized ligands, carboxylic acid ligand and triazole ligand, enhance the selectivity through hydrogen bonding and acid-base interaction. The ligands 1,3,5-tris(4-carboxyphenyl)benzene and 3,5-dimethyl-4H-1,2,4-triazole and Co 2+ The mutual coordination results in a three-dimensional pore structure with double interpenetration, and the microporous structure of the crystal realizes molecular sieving through size effect and surface chemistry.

[0010] Correspondingly, the present invention also provides a method for preparing the above-mentioned cobalt-based complex, the specific steps of which are as follows: The carboxylic acid ligand 1,3,5-tris(4-carboxyphenyl)benzene, 3,5-dimethyl-4H-1,2,4-triazole and cobalt nitrate hexahydrate are placed in a reaction vessel, a mixture of DMA and water is added, and ultrasonic treatment is performed at room temperature. The mixture is heated at 120° C. for 24-36 hours to obtain the cobalt-based complex.

[0011] The 1,3,5-tris(4-carboxyphenyl)benzene used has a CAS number of 50446-44-1 and a structure as follows: Formula I.

[0012] The 3,5-dimethyl-4H-1,2,4-triazole used has a CAS number of 7343-34-2 and a structure as follows: Formula II.

[0013] The mass ratio of the 1,3,5-tris(4-carboxyphenyl)benzene, 3,5-dimethyl-4H-1,2,4-triazole, and cobalt nitrate hexahydrate is 1:1:7 to 1:1:10, and 3 mL of a mixture of DMA and water is added for every 4 mg of 1,3,5-tris(4-carboxyphenyl)benzene.

[0014] The volume ratio of the mixed solution of DMA and water is 1:1.

[0015] The ultrasonic treatment was carried out at 60 Hz for 30 min.

[0016] The cobalt-based complex prepared by this invention, after solvent exchange with acetone for three days and activation at 80°C, can be used to prepare an adsorbent material for C2H2 / CO2 gas adsorption separation. The complex exhibits a significant difference in adsorption between C2H2 and CO2, with preferential adsorption of C2H2. The separation capacity of a C2H2 / CO2 binary mixture was predicted based on the ideal adsorption solution theory (IAST), with an IAST selectivity of approximately 3.17 at 298K, demonstrating potential for practical separations.

[0017] Compared with the prior art, the preparation method provided by the present invention has the following advantages: (1) The unsaturated metal sites in the cobalt-based complex prepared by the present invention provide strong binding sites, which can promote the preferential adsorption of acetylene by the material. The two functionalized ligands, carboxylic acid ligand and triazole ligand, enhance the selectivity through hydrogen bonding and acid-base interaction. The ligands 1,3,5-tris(4-carboxyphenyl)benzene and 3,5-dimethyl-4H-1,2,4-triazole react with Co 2+The mutual coordination results in a three-dimensional pore structure with double interpenetration. The microporous structure of the crystal realizes molecular sieving through size effect and surface chemistry, showing strong separation selectivity in the separation application of C2H2 / CO2, expanding the crystallographic structure data of cobalt-based complexes, helping to study the assembly mechanism of cobalt-based complexes, promoting industrial-scale production, and providing guidance for the expansion of applications in gas adsorption and separation.

[0018] (2) The method for preparing the cobalt-based complex provided by the present invention has an environmentally friendly reaction system and uses a small amount of organic solvent; the reaction conditions are simple and the synthesis efficiency is high; the amount of ligand used is low, which saves costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is the basic asymmetric unit of the cobalt-based complex prepared in Example 1; Figure 2 This is a pore structure diagram of the cobalt-based complex prepared in Example 1; Figure 3 This is a diagram of the doubly interpenetrating topological structure of the cobalt-based complex prepared in Example 1; Figure 4 This is the thermogravimetric curve of the cobalt-based complex prepared in Example 1; Figure 5 This is the infrared spectrum of the cobalt-based complex prepared in Example 1; Figure 6 This is a graph showing the C2H2 / CO2 single-component adsorption curve of the cobalt-based complex prepared in Example 1 at 273K; Figure 7 This is a graph showing the C2H2 / CO2 single-component adsorption curve of the cobalt-based complex prepared in Example 1 at 298K; Figure 8 IAST selectivity diagrams of C2H2 / CO2 mixed gas at 273K and 298K for the cobalt-based complex prepared in Example 1; Figure 9 This is the penetration curve of the C2H2 / CO2 mixed gas at 298K for the cobalt-based complex prepared in Example 1. DETAILED DESCRIPTION

[0020] 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 conventional methods; the instruments and drugs used, unless otherwise specified, can be obtained from normal commercial channels.

[0021] Example 1 A method for preparing a cobalt-based complex comprises the following steps: 4 mg of 1,3,5-tris(4-carboxyphenyl)benzene, 4 mg of 3,5-dimethyl-4H-1,2,4-triazole, and 40 mg of cobalt nitrate hexahydrate were accurately weighed using an analytical balance and placed in a 10 mL glass vial. 3 mL of DMA aqueous solution was added and ultrasonicated at room temperature for 30 minutes. The reaction system was placed in a thermostatic blower oven at 120°C for 24-36 hours to produce purple blocky crystals. The crystals were separated from the liquid phase by filtration to obtain the cobalt-based complex (yield 72%, based on 1,3,5-tris(4-carboxyphenyl)benzene).

[0022] Example 2 A method for preparing a cobalt-based complex comprises the following steps: 4 mg of 1,3,5-tris(4-carboxyphenyl)benzene, 4 mg of 3,5-dimethyl-4H-1,2,4-triazole, and 28 mg of cobalt nitrate hexahydrate were accurately weighed using an analytical balance and placed in a 10 mL glass vial. 3 mL of DMA aqueous solution was added and ultrasonicated at room temperature for 30 minutes. The reaction system was placed in a thermostatic blower oven at 120°C for 24-36 hours to produce purple blocky crystals. The crystals were separated from the liquid phase by filtration to obtain the cobalt-based complex (yield 72%, based on 1,3,5-tris(4-carboxyphenyl)benzene).

[0023] The cobalt-based complexes prepared in Example 1 and Example 2 have the same structure and the molecular formula is [Co(BTB 3- )(DMTA)(H20)], where Co represents divalent cobalt ion, BTB 3- represents the deprotonated 1,3,5-tris(4-carboxyphenyl)benzenecarboxylate ligand, DMTA represents 3,5-dimethyl-4H-1,2,4-triazole, and H2O represents a water molecule.

[0024] like Figure 1 As shown in Table 1-3, the cobalt-based complex belongs to the cubic Im-3 space group, and the basic asymmetric unit of the crystal (such as Figure 1 (shown) contains one hexacoordinated Co 2+ , a deprotonated BTB 3- ligand molecule, a coordinated DMTA ligand molecule and a coordinated water molecule. 2+ The coordination mode is six-coordination, in which four coordinated oxygen atoms come from the oxygen atoms in the carboxylic acid ligand, one coordinated oxygen atom comes from the oxygen atom in the solvent water, and one coordinated nitrogen atom comes from the nitrogen atom in 3,5-dimethyl-4H-1,2,4-triazole. Figure 2 、 Figure 3As shown, the ligands 1,3,5-tris(4-carboxyphenyl)benzene, 3,5-dimethyl-4H-1,2,4-triazole and Co 2+ The mutual coordination results in a three-dimensional pore structure with double interpenetration.

[0025] The unit cell parameters are: axis length a = b = c = 27.1743 Å; α = β = γ = 90°; unit cell volume is 20066.7 Å 3 ; Z=12.

[0026] The single crystal structure was acquired at room temperature using a Bruker Apex2 Smart CCD area detector. Absorption correction was performed using a graphite monochromator with a λ (Mo Kα) of 0.71073 Å and a variable scan rate of ω-2 Å using the multiscan program SADABS. The crystal structure was solved directly using the Sir97 program. The F2 structure was refined using the SHELXL-97 program using full-matrix least-squares. Anisotropic refinement was performed on all non-hydrogen atoms. Hydrogen atoms of organic ligands were generated by geometric symmetry (CH 0.96 Å).

[0027] The sample prepared in Example 1 was subjected to infrared spectroscopy analysis at room temperature. Figure 5 It can be seen that the characteristic peaks after carboxyl coordination in BTB and the Co-O / Co-N vibration peaks are at 1616 cm -1 and 480 cm -1 , demonstrating the successful synthesis of cobalt-based complexes.

[0028] Table 1 Crystal data

[0029] Table 2 Typical bond length data of crystals (unit: Å)

[0030] Table 3 Typical bond angle data of crystals (unit: °)

[0031] Application Example 1 Thermal Stability Test of Cobalt-Based Complex The weight loss of the cobalt-based complex prepared in Example 1 at 40-900°C was tested by thermogravimetric analysis in a N2 atmosphere. Figure 4 It can be seen that the cobalt-based complex loses the solvent molecules in the system at 200°C, and then the complex can be stabilized to 400°C. After 400°C, the complex decomposes, indicating that the complex has good thermal stability.

[0032] Application Example 2 Adsorption Performance Test of Cobalt-Based Complex The cobalt-based complex prepared in Example 1 was solvent exchanged with acetone for three days and activated at 80° C. to prepare an adsorption material for C 2 H 2 / CO 2 gas adsorption separation.

[0033] Figure 6 、 Figure 7 The single-component adsorption curves for acetylene and carbon dioxide at 273K and 298K, respectively, are shown. Adsorption-desorption isotherms for acetylene and carbon dioxide were performed on a 0.1g activated sample at pressures of 0-110kPa using an ASAP 2020 surface area and pore size analyzer at 273K and 298K, respectively. As can be seen from the figure, the material adsorbs acetylene more strongly than carbon dioxide.

[0034] Figure 8 The IAST selectivity diagram of acetylene and carbon dioxide mixed gas (volume ratio of 50:50) at 273K and 298K respectively is about 3.17, which shows that the material has the potential for acetylene / carbon dioxide separation.

[0035] Figure 9 This figure shows the breakthrough curve for a 50:50 volume ratio acetylene and carbon dioxide mixture at 298 K. A 0.5 g sample, after activation, was loaded into a penetration column filled with quartz wool. A breakthrough test was performed at 298 K using a BSD-MAB analyzer. Following the breakthrough test, the adsorbent was passed through helium at a flow rate of 15 mL / min at 353 K and regenerated at 353 K for 4 hours to ensure complete desorption of the adsorbed gases. The figure shows that the acetylene / carbon dioxide separation time is 10 minutes, demonstrating that the material can effectively separate acetylene and carbon dioxide.

[0036] 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 cobalt-based complex, characterized in that Its molecular formula is [Co(BTB 3- )(DMTA)( H2O)], where Co represents divalent cobalt ion, BTB 3- represents the deprotonated 1,3,5-tris(4-carboxyphenyl)benzenecarboxylate ligand, DMTA represents 3,5-dimethyl-4H-1,2,4-triazole, and H2O represents a water molecule.

2. The cobalt-based complex according to claim 1, characterized in that The cobalt-based complex belongs to the cubic Im-3 space group, with unit cell parameters of: axis length a = b = c = 27.1743 Å; α = β = γ = 90°; unit cell volume is 20066.7 Å 3 Z = 12; the basic asymmetric unit contains a six-coordinated Co 2+ , a deprotonated BTB 3- ligand molecule, a coordinated DMTA ligand molecule and a coordinated water molecule; Co 2+ The coordination mode is hexacoordination, in which 4 coordinated oxygen atoms come from the oxygen atoms in the carboxylic acid ligand, 1 coordinated oxygen atom comes from the oxygen atom in the solvent H20, and 1 coordinated nitrogen atom comes from the nitrogen atom in 3,5-dimethyl-4H-1,2,4-triazole; the ligands 1,3,5-tris(4-carboxyphenyl)benzene, 3,5-dimethyl-4H-1,2,4-triazole and Co 2+ The mutual coordination results in a three-dimensional pore structure with double interpenetration.

3. The method for preparing the cobalt-based complex according to claim 1 or 2, characterized in that: The specific steps are as follows: placing the carboxylic acid ligand 1,3,5-tris(4-carboxyphenyl)benzene, 3,5-dimethyl-4H-1,2,4-triazole and cobalt nitrate hexahydrate into a reaction vessel, adding a mixture of DMA and water, ultrasonically treating the mixture at room temperature, heating the mixture to a certain temperature and keeping the temperature for 24-36 hours to obtain the cobalt-based complex.

4. The method for preparing the cobalt-based complex according to claim 3, wherein: The mass ratio of the 1,3,5-tris(4-carboxyphenyl)benzene, 3,5-dimethyl-4H-1,2,4-triazole and cobalt nitrate hexahydrate is 1:1:7 to 1:1:

10.

5. The method for preparing the cobalt-based complex according to claim 3, characterized in that: For every 4 mg of 1,3,5-tris(4-carboxyphenyl)benzene, add 3 mL of a mixture of DMA and water.

6. The method for preparing the cobalt-based complex according to claim 3, characterized in that: The volume ratio of the mixed solution of DMA and water is 1:

1.

7. The method for preparing the cobalt-based complex according to claim 3, characterized in that: The ultrasonic treatment was carried out at 60 Hz for 30 min.

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

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