A nitrogen-containing carboxylic acid transition metal complex and its preparation method and application

Abstract

The present invention provides a nitrogen-containing carboxylic acid transition metal complex and its preparation method and application, the chemical formula of which is [Zn3(H3Ntba)2(4,4′-bipy)] n , wherein H3Ntba=4,4′,4″‑triphenylamine tricarboxylate, and 4,4′‑bipy=4,4′‑bipyridine. The preparation method is to use 4,4′,4″‑triphenylamine tricarboxylate as a ligand and 4,4′‑bipyridine as an auxiliary ligand, and react with zinc nitrate in a mixed solvent of N,N‑dimethylformamide and N,N‑dimethylacetamide to obtain a nitrogen-containing carboxylic acid transition metal complex. The complex belongs to the orthorhombic system and the Cmca space group, and its unit cell parameters are: α=90°, β=90°, γ=90°. The preparation method of the present invention is simple to operate and can be promoted and applied on a large scale. The present invention also provides an application of the nitrogen-containing carboxylic acid transition metal complex, which can be used as a good CO2 gas adsorption and separation material.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal organic complex preparation, and in particular relates to a nitrogen-containing carboxylic acid transition metal complex and a preparation method and application thereof. Background Art

[0002] With the development of science and technology, the extensive use of coal, oil, and natural gas has led to a continuous increase in atmospheric carbon dioxide emissions. Large amounts of carbon dioxide act like an invisible glass cover, absorbing long-wave radiation emitted by the Earth's surface and preventing heat exchange with outer space. This has led to an intensified greenhouse effect, resulting in a series of environmental problems such as melting glaciers, rising sea levels, abnormal climate conditions, and increased land drought and desertification. Therefore, mastering methods for quickly and efficiently capturing and converting carbon dioxide is of great significance in helping to solve environmental and energy problems.

[0003] Current methods for capturing carbon dioxide include absorption, membrane separation, and adsorption. Common materials for capturing carbon dioxide include activated carbon, calcium oxide-based adsorbents, sodium-based adsorbents, potassium-based adsorbents, covalent organic materials, and metal-organic frameworks (MOFs). MOFs, due to their structural characteristics such as large surface area, high porosity, adjustable pore size, and numerous active sites, have attracted considerable research attention in recent years and have been applied in a variety of fields, including adsorption, sensing, and catalysis. Nitrogen-containing carboxylic acid transition metal complexes, which use metal ions as coordination centers to form 1D, 2D, and 3D structures, can be directly used as adsorbent materials in gas adsorption and separation applications due to their unique porous structures.

[0004] The present invention utilizes the potential superior properties of 4,4′,4″-triphenylamine tricarboxylate, a "triangular" nitrogen-containing tricarboxylic acid flexible ligand, to combine it with a transition metal salt to prepare a transition metal complex with high porosity and large specific surface area. The complex's excellent pore structure and its differences in adsorption capacity for different gas molecules are utilized to achieve the separation effect of mixed gases, providing a good adsorption material for the field of gas adsorption separation. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the deficiencies of the above-mentioned prior art and provide a nitrogen-containing carboxylic acid transition metal complex and its preparation method and application. The preparation method of the present invention is simple to operate, and the obtained complex has a high specific surface area and can be used as a good gas adsorption material.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a nitrogen-containing carboxylic acid transition metal complex and its preparation method and application, characterized in that the chemical formula of the nitrogen-containing carboxylic acid transition metal complex is [Zn3(H3Ntba)2(4,4′-bipy)] n, where H3Ntba = 4,4′,4″-triphenylamine tricarboxylate, 4,4′-bipy = 4,4′-bipyridine;

[0007] This nitrogen-containing carboxylic acid transition metal complex belongs to the orthorhombic system and Cmca space group, and its unit cell parameters are: a=34.616Å, b=27.381Å, c=23.974Å, α=90º, β=90º, γ=90º.

[0008] A method for preparing a nitrogen-containing carboxylic acid transition metal complex, characterized in that the method comprises:

[0009] S1. Zinc nitrate, 4,4′,4″-triphenylamine tricarboxylate, and 4,4′-bipyridine were sequentially added to a glass bottle, and then a mixed solvent of N,N-dimethylformamide and N,N-dimethylacetamide was added, and stirred at room temperature for 30 minutes to obtain a mixed solution A;

[0010] S2. Place the mixed solution A obtained in S1 in a constant temperature forced air drying oven, react at a temperature of 90°C to 100°C for 48h to 72h, take it out, cool it naturally to room temperature, wash it with pure water and anhydrous ethanol three times each, then filter and dry it to obtain yellow leaf-shaped crystals, which are the nitrogen-containing carboxylic acid transition metal complex.

[0011] The preparation method uses zinc nitrate as a transition metal salt, 4,4',4"-triphenylamine triformate as a ligand, and 4,4'-bipyridine as an auxiliary ligand.

[0012] Preferably, the molar ratio of zinc nitrate, 4,4′,4″-triphenylamine tricarboxylate and 4,4′-bipyridine in S1 is 5:2:3; the volume ratio of N,N-dimethylformamide and N,N-dimethylacetamide is 2:1; and the dosage ratio of zinc nitrate to N,N-dimethylacetamide is 0.1 mmol:1 mL.

[0013] The nitrogen-containing carboxylic acid transition metal complex obtained in the present invention is analyzed for specific surface area and pore size using an ASAP 2020 HD88 fully automatic microporous physical adsorption analyzer.

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] 1. The preparation method of the nitrogen-containing carboxylic acid transition metal complex provided by the present invention comprises mixing zinc nitrate, 4,4',4"-triphenylamine tricarboxylate and 4,4'-bipyridine in a certain proportion in sequence by a solvothermal method, then adding a mixed solvent of N,N-dimethylformamide and N,N-dimethylacetamide, stirring and reacting in a constant temperature box for a certain period of time to obtain yellow leaf-shaped crystals, i.e., the nitrogen-containing carboxylic acid transition metal complex. This preparation method is simple to operate and can be widely promoted and applied.

[0016] 2. The nitrogen-containing carboxylic acid transition metal complex prepared by the present invention has zinc as the coordination center, 4,4′,4″-triphenylamine tricarboxylate as the ligand, and 4,4′-bipyridine as the auxiliary ligand. The obtained complex can be used as a good CO2 gas adsorption and separation material.

[0017] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 [Zn3(H3Ntba)2(4,4′-bipy)] prepared in Example 1 of the present invention n Diagram of the asymmetric structural unit.

[0019] Figure 2 [Zn3(H3Ntba)2(4,4′-bipy)] prepared in Example 1 of the present invention n 3D structural diagram.

[0020] Figure 3 [Zn3(H3Ntba)2(4,4′-bipy)] prepared in Example 1 of the present invention n Comparison of the experimental adsorption isotherm (left: Y-axis) and the simulated adsorption isotherm (left: Y-axis) as well as its adsorption selectivity separation ratio of equimolar binary mixture gas CO2 / N2 (right: Y-axis). DETAILED DESCRIPTION

[0021] Example 1

[0022] This embodiment provides a nitrogen-containing carboxylic acid transition metal complex, the chemical formula of which is [Zn3(H3Ntba)2(4,4′-bipy)] n , wherein H3Ntba = 4,4′,4″-triphenylamine tricarboxylate, 4,4′-bipy = 4,4′-bipyridine. The preparation method of the complex is:

[0023] S1. 0.1 mmol of zinc nitrate, 0.04 mmol of triphenylamine 4,4′,4″-tricarboxylate, and 0.06 mmol of 4,4′-bipyridine were sequentially added to a 10 mL glass bottle, followed by the addition of a mixed solvent of 2 mL of N,N-dimethylformamide and 1 mL of N,N-dimethylacetamide. The mixture was then stirred at room temperature for 30 min to obtain a mixed solution A.

[0024] S2. Place the mixed solution A obtained in S1 in a constant temperature forced air drying oven and dry it at 95°C for 48 hours. Take it out, cool it naturally to room temperature, wash it with pure water and anhydrous ethanol three times each, then filter and dry it to obtain yellow leaf-shaped crystals, which are nitrogen-containing carboxylic acid transition metal complex [Zn3(H3Ntba)2(4,4′-bipy)] n .

[0025] The nitrogen-containing carboxylic acid transition metal complex prepared in this example has zinc as the coordination center, 4,4′,4″-triphenylamine tricarboxylate as the ligand, and 4,4′-bipyridine as the auxiliary ligand. The complex is a yellow leaf-shaped crystal with the molecular formula C 52 H 32 N4O 12 Zn3.

[0026] The basic structural unit of the nitrogen-containing carboxylic acid transition metal complex prepared in this example is shown in FIG. Figure 1 Single crystal X-ray diffraction analysis shows that it belongs to the orthorhombic system, Cmca space group, with unit cell parameters of a=34.616Å, b=27.381Å, c=23.974Å, α=90°, β=90°, and γ=90°. The complex has a three-dimensional network structure, with each asymmetric structural unit containing three crystallographically independent zinc ions, two 4,4′,4″-triphenylamine tricarboxylate ligands, and a 4,4′-bipyridine auxiliary ligand. The central metal ion Zn1 has a hexa-coordinate structure with a regular octahedral configuration, with six oxygen atoms coming from the six 4,4′,4″-triphenylamine tricarboxylate ligands. The metal ion Zn2 ​​has a penta-coordinate structure with a distorted trigonal bipyramidal configuration, with four oxygen atoms coming from three 4,4′,4″-triphenylamine tricarboxylate ligands and one nitrogen atom from the 4,4′-bipyridine auxiliary ligand. Some bond lengths (Å) and bond angles (°) of this nitrogen-containing carboxylate transition metal complex are listed in Table 1.

[0027] Table 1 Some bond lengths (Å) and bond angles (°) of transition metal complexes containing nitrogen-containing carboxylic acids

[0028]

[0029] The three-dimensional structure of the nitrogen-containing carboxylic acid transition metal complex prepared in this example is as follows Figure 2 , it can be seen from the figure that the complex has obvious pore characteristics.

[0030] The pore size and specific surface area of ​​the nitrogen-containing carboxylic acid transition metal complex prepared in this example were measured using an ASAP 2020 HD88 fully automatic microporous physical adsorption analyzer at 77K using N2 adsorption / desorption isotherms. The results showed that the specific surface area was 42.9 m 2 / g, and the average pore diameter is 3.5nm.

[0031] The nitrogen-containing carboxylic acid transition metal complex prepared in this example was applied to gas adsorption and separation tests. CH4, CO2, N2, and O2 gas adsorption and desorption tests were conducted at 273K and 298K. The results showed that at 273K, the adsorption capacity of N2 was 0.84 cm 3 / g, and the adsorption capacity for O2 is 4.22cm 3 / g, and the adsorption capacity of CO2 is 24.05cm 3 / g, and the adsorption capacity for CH4 is 3.05cm 3 / g. At 298K, the adsorption capacity of N2 is 0.57cm 3 / g, and the adsorption capacity for O2 is 1.45cm 3 / g, and the adsorption capacity of CO2 is 14.171cm 3 / g, and the adsorption capacity for CH4 is 2.94 cm 3 / g. It can be seen that the complex material has different adsorption capacities for different gases, and has good adsorption selectivity for CO2 gas.

[0032] According to the single-point Langmuir-Freundlich model of ideal adsorption solution theory (IAST), the adsorption isotherms of [Zn3(H3Ntba)2(4,4′-bipy)] activated at 273K and 298K were calculated from the single-component adsorption isotherms. n Adsorption separation selectivity of equimolar binary gas mixture CO2 / N2; wherein the adsorption selectivity S is defined as.

[0033] Depend on Figure 3 It can be seen that under standard atmospheric pressure, the nitrogen-containing carboxylic acid transition metal complex [Zn3(H3Ntba)2(4,4′-bipy)] prepared in this embodiment n Theoretical molar adsorption separation selectivity for CO2 / N2 S It is 750:1, which fully proves that it can be used as an ideal material for CO2 gas adsorption separation.

[0034] Example 2

[0035] This embodiment provides a method for preparing a nitrogen-containing carboxylic acid transition metal complex, which is:

[0036] S1. 0.2 mmol of zinc nitrate, 0.08 mmol of 4,4′,4″-triphenylamine tricarboxylate, and 0.12 mmol of 4,4′-bipyridine were sequentially added to a 25 mL glass bottle, followed by the addition of a mixed solvent of 4 mL of N,N-dimethylformamide and 2 mL of N,N-dimethylacetamide. The mixture was then stirred at room temperature for 30 min to obtain a mixed solution A.

[0037] S2. Place the mixed solution A obtained in S1 in a constant temperature forced air drying oven and dry it at 100°C for 48 hours. Take it out, cool it naturally to room temperature, wash it with pure water and anhydrous ethanol three times each, then filter and dry it to obtain yellow leaf-shaped crystals, which are the nitrogen-containing carboxylic acid transition metal complex [Zn3(H3Ntba)2(4,4′-bipy)] n .

[0038] The nitrogen-containing carboxylic acid transition metal complex prepared in this example is yellow leaf-shaped crystals with a specific surface area of ​​42.3 m 2 / g, and the average pore size is 3.6 nm.

[0039] Example 3

[0040] This embodiment provides a method for preparing a nitrogen-containing carboxylic acid transition metal complex, which is:

[0041] S1. 0.2 mmol of zinc nitrate, 0.08 mmol of 4,4′,4″-triphenylamine tricarboxylate, and 0.12 mmol of 4,4′-bipyridine were sequentially added to a 25 mL glass bottle, followed by the addition of a mixed solvent of 4 mL of N,N-dimethylformamide and 2 mL of N,N-dimethylacetamide. The mixture was then stirred at room temperature for 30 min to obtain a mixed solution A.

[0042] S2. Place the mixed solution A obtained in S1 in a constant temperature forced air drying oven and dry it at 98°C for 60 hours. Take it out, cool it naturally to room temperature, wash it with pure water and anhydrous ethanol three times each, then filter and dry it to obtain yellow leaf-shaped crystals, which are the nitrogen-containing carboxylic acid transition metal complex [Zn3(H3Ntba)2(4,4′-bipy)] n .

[0043] The nitrogen-containing carboxylic acid transition metal complex prepared in this example is yellow leaf-shaped crystals with a specific surface area of ​​41.7 m 2 / g, and the average pore diameter is 4.2nm.

[0044] Example 4

[0045] This embodiment provides a method for preparing a nitrogen-containing carboxylic acid transition metal complex, which is:

[0046] S1. 0.1 mmol of zinc nitrate, 0.04 mmol of triphenylamine 4,4′,4″-tricarboxylate, and 0.06 mmol of 4,4′-bipyridine were sequentially added to a 10 mL glass bottle, followed by the addition of a mixed solvent of 2 mL of N,N-dimethylformamide and 1 mL of N,N-dimethylacetamide. The mixture was then stirred at room temperature for 30 min to obtain a mixed solution A.

[0047] S2. Place the mixed solution A obtained in S1 in a constant temperature forced air drying oven and dry it at 93°C for 56 hours. Take it out, cool it naturally to room temperature, wash it with pure water and anhydrous ethanol three times each, then filter and dry it to obtain yellow leaf-shaped crystals, which are the nitrogen-containing carboxylic acid transition metal complex [Zn3(H3Ntba)2(4,4′-bipy)] n .

[0048] The nitrogen-containing carboxylic acid transition metal complex prepared in this example is yellow leaf-shaped crystals with a specific surface area of ​​41.9 m 2 / g, and the average pore diameter is 3.8nm.

[0049] Example 5

[0050] This embodiment provides a method for preparing a nitrogen-containing carboxylic acid transition metal complex, which is:

[0051] S1. 0.4 mmol of zinc nitrate, 0.16 mmol of 4,4′,4″-triphenylamine tricarboxylate, and 0.24 mmol of 4,4′-bipyridine were sequentially added to a 50 mL glass bottle, and then 8 mL of a mixed solvent of N,N-dimethylformamide and 4 mL of N,N-dimethylacetamide were added, and the mixture was stirred at room temperature for 30 min to obtain a mixed solution A.

[0052] S2. Place the mixed solution A obtained in S1 in a constant temperature forced air drying oven and dry it at 90°C for 72 hours. Take it out, cool it naturally to room temperature, wash it with pure water and anhydrous ethanol three times each, then filter and dry it to obtain yellow leaf-shaped crystals, which are the nitrogen-containing carboxylic acid transition metal complex [Zn3(H3Ntba)2(4,4′-bipy)] n .

[0053] The nitrogen-containing carboxylic acid transition metal complex prepared in this example is yellow leaf-shaped crystals with a specific surface area of ​​41.6 m 2 / g, and the average pore diameter is 3.5nm.

[0054] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent variation made to the above embodiment based on the essence of the invention technology shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A porous transition metal complex of nitrogen-containing carboxylic acid, characterized in that: The chemical formula of the nitrogen-containing carboxylic acid transition metal complex is [Zn3(H3Ntba)2(4,4′-bipy)] n , where H3Ntba = 4,4′,4″-triphenylamine tricarboxylate, 4,4′-bipy = 4,4′-bipyridine; The nitrogen-containing carboxylic acid transition metal complex belongs to the orthorhombic system and the Cmca space group, and its unit cell parameters are: a=34.616Å, b=27.381Å, c=23.974Å, α=90º, β=90º, γ=90º; The preparation method of the nitrogen-containing carboxylic acid transition metal complex is: S1. Zinc nitrate, 4,4′,4″-tricarboxylic acid triphenylamine and 4,4′-bipyridine were added to a glass bottle in sequence, and then a mixed solvent of N,N-dimethylformamide and N,N-dimethylacetamide was added, and the mixture was stirred at room temperature for 30 minutes to obtain a mixed solution A; the molar ratio of zinc nitrate, 4,4′,4″-tricarboxylic acid triphenylamine and 4,4′-bipyridine was 5:2:3; the volume ratio of N,N-dimethylformamide and N,N-dimethylacetamide in the mixed solvent was 2:1; and the amount ratio of zinc nitrate to N,N-dimethylacetamide was 0.1 mmol:1 mL; S2. Place the mixed solution A obtained in S1 in a constant temperature forced air drying oven, react at a temperature of 90°C to 100°C for 48h to 72h, take it out, cool it naturally to room temperature, wash it with pure water and anhydrous ethanol three times each, then filter and dry it to obtain yellow leaf-shaped crystals, which are the nitrogen-containing carboxylic acid transition metal complex.

2. The nitrogen-containing carboxylic acid transition metal complex according to claim 1, characterized in that The specific surface area of ​​the nitrogen-containing carboxylic acid transition metal complex is 41.6 m 2 / g~42.9m 2 / g, and the average pore size is 3.5nm~4.2nm.

3. An application of the nitrogen-containing carboxylic acid transition metal complex according to claim 1, characterized in that: The nitrogen-containing carboxylic acid transition metal complex is used for selective adsorption-separation of CO2 in mixed gas.

Images