Pyrazine-bridged terpyridyl polymer as well as preparation method and application thereof

Abstract

The invention discloses a pyrazine-bridged terpyridyl polymer as well as a preparation method and application thereof, and belongs to the technical field of high polymer materials. The pyrazine-bridged terpyridyl polymer has the following molecular structure: R is aryl, substituted aryl, heteroaromatic ring group or substituted heteroaromatic ring group, and n is the degree of polymerization. The polymer has relatively strong coordination chelation capability on heavy metal ions, has high adsorption capability on heavy metal ions in a solution system, takes a rigid aromatic structure as a skeleton, is good in structural stability, belongs to a solid material, and has a wide application prospect in the field of heavy metal removal.

Description

Technical Field

[0001] This invention relates to an adsorption material, particularly to a pyrazine-bridged terpyridine polymer, and also to its preparation method and application as a heavy metal adsorption material, belonging to the field of novel polymer material synthesis. Background Technology

[0002] Tripyridine, a tridentate chelating ligand, can coordinate with mercury and various heavy metal ions to form stable complexes. Introducing terpyridine into polymers holds promise for playing a significant role in the adsorption and removal of mercury and heavy metal ions. For example, Chinese patent (CN119463181A) discloses embedding a pyridine ligand (terpyridine) into the macromolecular framework of polyethersulfone, improving the molecular weight and structural stability of pyridine alone. Furthermore, the hyperconjugated system formed by the pyridine group and the benzene ring in polyethersulfone enhances the coordination stability between the pyridine-polyethersulfone organic polymer and heavy metal ions, thereby increasing its adsorption efficiency. However, its adsorption capacity for heavy metal ions is relatively low. For instance, the adsorption capacity for cadmium and mercury ions reaches its maximum at pH=7, at 80 μg / g and 120 μg / g, respectively. It is only suitable for the adsorption of trace amounts of heavy metal ions in solution systems and is insufficient for the removal of heavy metal ions from heavily polluted wastewater. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the first objective of this invention is to provide a pyrazine-bridged terpyridine polymer. This polymer constructs terpyridine ligand units in its molecular backbone through pyrazine, achieving perfect coupling between bidentate ligand-pyrazine and tridentate ligand-terpyridine. This synergistically enhances the coordination and chelation effect on heavy metal ions, significantly improving the adsorption capacity for heavy metal ions compared to existing terpyridine ligands. Furthermore, this polymer, with its rigid aromatic structure as a backbone, exhibits good structural stability and is a solid material, thus possessing broad application prospects in the field of heavy metal removal.

[0004] The second objective of this invention is to provide a method for preparing pyrazine-bridged terpyridine polymers. This method uses readily available and relatively low-cost raw materials, and the synthesis process is simple and the conditions are mild, which helps to greatly reduce production and application costs.

[0005] The third objective of this invention is to provide an application of a pyrazine-bridged terpyridine polymer, which can efficiently and with high capacity adsorb heavy metal ions in a solution system through coordination chelation, and generates insoluble polymer-heavy metal complex precipitates that are easy to separate. It can be widely used for the adsorption and removal of heavy metal ions in wastewater.

[0006] To achieve the above-mentioned technical objectives, the present invention provides a pyrazine-bridged terpyridine polymer having the following molecular structure:

[0007] in, n = 1~35, where n is the degree of aggregation (n is an integer, specifically 1, 2, 3...); R is an aromatic group, a substituted aromatic group, an aromatic heterocyclic group, or a substituted aromatic heterocyclic group; The substituted aromatic group contains C1 to C2. 10 Alkyl, C1-C 10 At least one aryl group of the alkoxy group; The substituted aromatic heterocyclic group contains C1 to C2. 10 Alkyl, C1-C 10 An aromatic heterocyclic group in which at least one substituent of an alkoxy group is present.

[0008] The pyrazine-bridged terpyridine polymer of this invention has a backbone composed of alternating pyridine and pyrazine rings. The pyrazine ring is a diaza-heterocyclic ring with bidentate ligand characteristics. The pyrazine and pyridine rings further participate in the construction of a terpyridine structure, which is a typical tridentate ligand. This achieves perfect coupling between bidentate ligand-pyrazine and tridentate ligand-terpyridine, demonstrating the synergistic effect of multiple coordination adsorption and significantly improving the adsorption capacity for heavy metal ions. Simultaneously, the entire polymer constitutes a rigid, highly conjugated system. On the one hand, the presence of a large π enhances the electron-donating ability of the unit cells, improving the coordination capacity for heavy metal ions. On the other hand, the rigid, highly conjugated system provides a stable framework structure, allowing heavy metal ions to precipitate in solid form after adsorption, facilitating separation. Furthermore, introducing aryl groups, heterocycles, and alkyl or alkoxy groups modified on the polymer side chains can regulate the polymer's adsorption capacity for heavy metal ions through electronic effects and steric hindrance.

[0009] As a preferred embodiment, the aromatic group is phenyl or naphthyl.

[0010] As a preferred embodiment, the aromatic heterocyclic group is a five-membered or six-membered aromatic heterocyclic group containing at least one heteroatom selected from nitrogen, oxygen, and sulfur. More preferably, the aromatic heterocyclic group is a six-membered aromatic heterocyclic group containing a nitrogen heteroatom.

[0011] In the pyrazine-bridged terpyridine polymer of the present invention, R can be selected from an aromatic group, a substituted aromatic group, an aromatic heterocyclic group, or a substituted aromatic heterocyclic group. When R is an aromatic group, the aromatic group can be phenyl, or a fused aromatic ring group, such as naphthyl or phenanthrene, or a group consisting of multiple benzene rings bonded by covalent bonds, such as biphenyl. When R is a substituted aromatic group, the substituted aromatic group contains C1 to C2. 10 Alkyl, C1-C 10An aromatic group containing at least one substituent in the alkoxy group; the number and position of substituents are not limited, and there can be one or more substituents, generally one to two, and the substituents can be located at any substituted position on the aromatic group. The substituents are C1 to C2. 10 When alkyl is used, the substituent can be a straight-chain alkyl group, such as methyl, propyl, octyl, etc. When the number of carbon atoms is greater than 3, the substituent can be a cycloalkyl or branched alkyl group, such as isopropyl, isobutyl, cyclohexyl, etc. The substituent has a C1 to C2 configuration. 10 When R is an alkoxy group, the alkyl group can be a straight-chain alkyl group, such as methyl, propyl, hexyl, octyl, etc. When the number of carbon atoms is greater than 3, the substituent can be a cycloalkyl or a branched alkyl group, such as isopropyl, isobutyl, cyclohexyl, etc. When R is an aromatic heterocyclic group, the aromatic heterocyclic group can be a five-membered or six-membered aromatic heterocyclic group containing at least one heteroatom of nitrogen, oxygen, or sulfur. Specific examples include thiophene, furan, pyrrole, imidazole, thiazole, pyrazole, oxazole, pyridine, pyrimidine, pyran, pyridazine, etc. When R is a substituted aromatic heterocyclic group, the substituted aromatic heterocyclic group contains C1 to C2 atoms. 10 Alkyl, C1-C 10 An aromatic heterocyclic group containing at least one substituent in the alkoxy group; the number and position of substituents are not limited, and there can be one or more substituents, generally one, and the position of the substituent can be any substituted position on the aromatic group. The substituents are C1 to C2. 10 When alkyl is used, the substituent can be a straight-chain alkyl group, such as methyl, propyl, octyl, etc. When the number of carbon atoms is greater than 3, the substituent can be a cycloalkyl or branched alkyl group, such as isopropyl, isobutyl, cyclohexyl, etc. The substituent has a C1 to C2 configuration. 10 When alkoxy is used, the alkyl group in the alkoxy group can be a straight-chain alkyl group, such as methyl, propyl, hexyl, octyl, etc. When the number of carbon atoms is greater than 3, the substituent can be a cycloalkyl or a branched alkyl group, such as isopropyl, isobutyl, cyclohexyl, etc.

[0012] Specific examples of the aromatic aldehydes of the present invention are as follows:

[0013] R1 is hydrogen, C1-C5 alkoxy, or C1-C5 alkyl.

[0014] In the pyrazine-bridged terpyridine polymer of the present invention, n is further preferably 5 to 30.

[0015] The present invention also provides a method for preparing pyrazine-bridged terpyridine polymers. The method involves dissolving 2,5-diacetylpyrazine and an aromatic aldehyde in a solvent to form a mixed solution, and then adding ammonia water or ammonium salt solution containing sodium hydroxide dropwise to the mixed solution to carry out a zijibaben reaction, thereby obtaining the pyrazine-bridged terpyridine polymer. The aromatic aldehyde has the following molecular structure: ; in, R is an aromatic group, a substituted aromatic group, an aromatic heterocyclic group, or a substituted aromatic heterocyclic group; The substituted aromatic group contains C1 to C2. 10 Alkyl, C1-C 10 At least one aryl group of the alkoxy group; The substituted aromatic heterocyclic group contains C1 to C2. 10 Alkyl, C1-C 10 An aromatic heterocyclic group in which at least one substituent of an alkoxy group is present.

[0016] As a preferred embodiment, the molar ratio of the 2,5-diacetylpyrazine to the aromatic aldehyde is (0.5–1.5):1. A further preferred molar ratio of the 2,5-diacetylpyrazine to the aromatic aldehyde is (1.0–1.2):1.

[0017] As a preferred embodiment, the zijibaben reaction is carried out at a temperature of 45–95°C for 1–12 hours. As a more preferred embodiment, the zijibaben reaction is carried out at a temperature of 75–90°C for 6–12 hours. A further preferred reaction temperature is 80–90°C. A further preferred reaction time is 8–12 hours. Under these preferred reaction conditions, the monomer conversion rate is significantly improved, and the polymer yield can reach over 95%.

[0018] As a preferred embodiment, the solvent may be ethanol, methanol, isopropanol, water, dimethylformamide, etc.

[0019] This invention also provides an application of a pyrazine-bridged terpyridine polymer as a heavy metal adsorbent. The pyrazine-bridged terpyridine polymer of this invention possesses a molecular framework coupled with a bidentate ligand-pyrazine and a trimentate ligand-terpyridine, exhibiting strong coordination ability for heavy metal ions and possessing strong adsorption capacity, enabling it to rapidly capture heavy metal ions from the environment.

[0020] As a preferred embodiment, the pyrazine-bridged terpyridine polymer is used to adsorb heavy metal ions in water.

[0021] This invention provides a method for preparing pyrazine-bridged terpyridine polymers, comprising the following steps: (1) Add 2,5-diacetylpyrazine to the ethanol solution of aromatic aldehyde and dissolve it completely to form a mixed solution; (2) Add sodium hydroxide ammonia water or ammonium salt solution to the mixed solution; (3) After the addition is complete, stir at 75-90℃ for 6-12 hours; (4) After the reaction is complete, filter the solid phase, wash it three times with methanol and chloroform, and dry it in a vacuum drying oven to obtain a pyrazine-bridged terpyridine polymer.

[0022] The schematic synthetic route of the pyrazine-bridged terpyridine polymer of the present invention is as follows:

[0023] In the reaction equation, R represents hydrogen, C1 to C2. 10 Alkyl or C1-C 10 Alkoxy group; n is the degree of polymerization (n is an integer, specifically 1, 2, 3, ...).

[0024] Compared with the prior art, the technical solution of the present invention brings the following beneficial technical effects: The method for synthesizing pyrazine-bridged terpyridine polymers of the present invention uses 2,5-diacetylpyrazine, pyrimidine formaldehyde (or formaldehyde-containing compounds), sodium hydroxide (or alkalis), ammonia (or ammonium salts), ethanol (or alcohols and other organic solvents) as the main raw materials. The raw materials are abundant and the cost is low.

[0025] The pyrazine-bridged terpyridine polymer provided by this invention has a simple preparation method and mild reaction conditions, which is conducive to large-scale industrial production.

[0026] The pyrazine-bridged terpyridine polymer provided by this invention can efficiently and with high capacity adsorb heavy metal ions in solution systems through coordination chelation, and form insoluble polymer-heavy metal complex precipitates that are easy to separate. It can be widely used for the adsorption and removal of heavy metal ions in wastewater. Attached Figure Description

[0027] 【 Figure 1 [Image caption: Gel permeation chromatogram of the pyrazine-bridged terpyridine polymer prepared in Example 1.]

[0028] 【 Figure 2 [Image caption: Transmission electron microscope image of the pyrazine-bridged terpyridine polymer prepared in Example 1.]

[0029] 【 Figure 3 [Image caption: 1H NMR spectrum of the pyrazine-bridged terpyridine polymer prepared in Example 4 (solvent d6-DMSO)] Detailed Implementation

[0030] The following examples are intended to further illustrate the present invention, but not to limit the scope of protection of the claims of the present invention.

[0031] Example 1 This embodiment uses 2,5-diacetylpyrazine, 5-pyrimidine formaldehyde, sodium hydroxide, ammonia, and ethanol as main raw materials, and specifically includes the following main steps: (1) In a 500 mL round-bottom flask, 2,5-diacetylpyrazine (3.5 g) was added to an ethanol solution of 5-pyrimidinecarboxaldehyde (2.3 g) to completely dissolve 2,5-diacetylpyrazine and 5-pyrimidinecarboxaldehyde; (2) Dissolve sodium hydroxide (5.63 g) in 20 mL of ammonia solution and add it dropwise into a round-bottom flask; (3) After the addition is complete, react at 80℃ for 12 hours; (4) After the reaction was completed, the solid phase was filtered, washed three times with methanol and chloroform, and dried in a vacuum drying oven to obtain pyrazine-bridged terpyridine polymers with a yield of 97.3%.

[0032] The specific synthesis route is as follows:

[0033] Example 2 This embodiment uses 2,5-diacetylpyrazine, 5-pyrimidine formaldehyde, sodium hydroxide, ammonia, and ethanol as main raw materials, and specifically includes the following main steps: (1) In a 500 mL round-bottom flask, 2,5-diacetylpyrazine (3.5 g) was added to an ethanol solution of 5-pyrimidinecarboxaldehyde (2.8 g) to completely dissolve 2,5-diacetylpyrazine and 5-pyrimidinecarboxaldehyde; (2) Dissolve sodium hydroxide in 20 mL of ammonia solution and add it dropwise into a round-bottom flask; (3) After the addition is complete, react at 90℃ for 12 hours; (4) After the reaction was completed, the solid phase was filtered, washed three times with methanol and chloroform, and dried in a vacuum drying oven to obtain pyrazine-bridged terpyridine polymers with a yield of 95.7%.

[0034] Example 3 This embodiment uses 2,5-diacetylpyrazine, 2-methoxy-5-carboxaldehyde pyrimidine, sodium hydroxide, ammonium chloride, and isopropanol as the main raw materials, and specifically includes the following main steps: (1) In a 500 mL round-bottom flask, 2,5-diacetylpyrazine (3.5 g) was added to an isopropanol solution of 2-methoxy-5-carboxaldehyde pyrimidine (2.3 g) to completely dissolve 2,5-diacetylpyrazine and 2-methoxy-5-carboxaldehyde pyrimidine. (2) Dissolve sodium hydroxide in 25 mL of ammonium chloride aqueous solution and add it dropwise into a round-bottom flask; (3) After the addition is complete, react at 85°C for 8 hours; (4) After the reaction was completed, the solid phase was filtered, washed three times with methanol and chloroform, and dried in a vacuum drying oven to obtain methoxypyrazine-bridged terpyridine polymers with a yield of 96.1%.

[0035] Example 4 This embodiment uses 2,5-diacetylpyrazine, 4-methoxybenzaldehyde, sodium hydroxide, ammonium chloride, and ethanol as main raw materials, and specifically includes the following main steps: (1) In a 500 mL round-bottom flask, 2,5-diacetylpyrazine (1.8 g) was added to an ethanol solution of 4-methoxybenzaldehyde (1.6 g) to completely dissolve 2,5-diacetylpyrazine and 4-methoxybenzaldehyde. (2) Dissolve sodium hydroxide in 18 mL of ammonium chloride aqueous solution and add it dropwise into a round-bottom flask; (3) After the addition is complete, react at 78°C for 12 hours; (4) After the reaction was completed, the solid phase was filtered, washed three times with methanol and chloroform, and dried in a vacuum drying oven to obtain a methoxybenzylpyrazine-bridged terpyridine polymer with a yield of 90.5%.

[0036] The specific synthesis route is as follows:

[0037] Example 5 0.17g of the polymer material prepared in Example 1 was added to 200mL of wastewater containing 22mg / L of mercury ions. After stirring at 50°C for 20 minutes, flocculant was added and the mixture was filtered. The mercury ion content in the treated wastewater was 0.005mg / L.

[0038] Example 6 0.4g of the polymer material prepared in Example 3 above was added to 500mL of wastewater containing 3.2mg / L cadmium ions, 11mg / L mercury ions, and 5.5mg / L lead ions. After stirring at room temperature for 30 minutes, flocculant was added and the mixture was filtered. After treatment, the concentrations of cadmium ions in the wastewater were 0.033mg / L, mercury ions were 0.009mg / L, and lead ions were 0.012mg / L.

[0039] Example 7 0.55g of the polymer material prepared in Example 4 above was added to 500mL of wastewater (pH=8.0) containing 12.2mg / L cadmium ions and 5.2mg / L mercury ions. After stirring at room temperature for 45 minutes, flocculant was added and the mixture was filtered. After treatment, the concentrations of cadmium ions in the wastewater were 0.061mg / L and the concentrations of mercury ions were 0.007mg / L.

Claims

1. A pyrazine-bridged terpyridine polymer, characterized in that: It has the following molecular structure: ； in, n=1~35； R is an aromatic group, a substituted aromatic group, an aromatic heterocyclic group, or a substituted aromatic heterocyclic group; The substituted aromatic group contains C1 to C2. 10 Alkyl, C1-C 10 At least one aryl group of the alkoxy group; The substituted aromatic heterocyclic group contains C1 to C2. 10 Alkyl, C1-C 10 An aromatic heterocyclic group in which at least one substituent of an alkoxy group is present.

2. The pyrazine-bridged terpyridine polymer according to claim 1, characterized in that: The aromatic group is phenyl or naphthyl; The aromatic heterocyclic group is a five-membered or six-membered aromatic heterocyclic group containing at least one heteroatom of nitrogen, oxygen, or sulfur.

3. The method for preparing a pyrazine-bridged terpyridine polymer according to claim 1 or 2, characterized in that: 2,5-Diacetylpyrazine and aromatic aldehyde are dissolved in a solvent to form a mixed solution. Ammonia water or ammonium salt solution containing sodium hydroxide is added dropwise to the mixed solution to carry out the zijibaben reaction, thereby obtaining a pyrazine-bridged terpyridine polymer. The aromatic aldehyde has the following molecular structure: ； in, R is an aromatic group, a substituted aromatic group, an aromatic heterocyclic group, or a substituted aromatic heterocyclic group; The substituted aromatic group contains C1 to C2. 10 Alkyl, C1-C 10 At least one aryl group of the alkoxy group; The substituted aromatic heterocyclic group contains C1 to C2. 10 Alkyl, C1-C 10 An aromatic heterocyclic group in which at least one substituent of an alkoxy group is present.

4. The method for preparing a pyrazine-bridged terpyridine polymer according to claim 3, characterized in that: The molar ratio of the 2,5-diacetylpyrazine to the aromatic aldehyde is (0.5-1.5):

1.

5. The method for preparing a pyrazine-bridged terpyridine polymer according to claim 3, characterized in that: The conditions for the zijibaben reaction are: reaction at 45–95°C for 1–12 hours.

6. The method for preparing a pyrazine-bridged terpyridine polymer according to claim 5, characterized in that: The conditions for the zizibaben reaction are: reaction at 75–90°C for 6–12 hours.

7. The application of the pyrazine-bridged terpyridine polymer according to claim 1 or 2, characterized in that: Application as a heavy metal adsorbent.

8. The application of the pyrazine-bridged terpyridine polymer according to claim 7, characterized in that: It is used to adsorb heavy metal ions in water.

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