A method for preparing a phosphorus-containing polymer by Friedel-Crafts polymerization catalyzed by a protonic acid

Abstract

The present invention discloses a method for synthesizing a phosphorus-containing polymer by Friedel-Crafts polymerization catalyzed by a protonic acid. Using a phosphorus-containing monomer and a fluorine-containing monomer as raw materials, and a protonic acid as a catalyst and a solvent, a phosphorus-containing polymer is synthesized through Friedel-Crafts polymerization reaction. The phosphorus-containing monomer can be selected from phosphine ligands with an aryl structure, complexes of phosphine ligands with an aryl structure, quaternary phosphonium salts with an aryl structure, etc. The synthesized phosphorus-containing polymer contains an aryl structure and a methylene group, and has a certain pore structure and swelling performance. In the present invention, using a protonic acid as a catalyst, on the one hand, it avoids the use of metal catalysts and there is no problem of metal residue, while reducing the synthesis cost of the phosphorus-containing polymer; on the other hand, the protonic acid also serves as a solvent, avoiding the use of other organic solvents, which not only reduces the cost but also is environmentally friendly; in addition, the synthesis method of the present invention is simple and the conditions are mild, which is conducive to popularization and expansion.

Description

Technical Field

[0001] The present invention relates to a method for synthesizing a phosphorus-containing polymer, and particularly to a method for synthesizing a phosphorus-containing polymer through a Friedel-Crafts polymerization catalyzed by a protonic acid, belonging to the technical field of chemical synthesis. Background Art

[0002] As an advanced emerging material, phosphorus-containing polymers have broad application prospects in the fields of heterogeneous catalysis, material separation, sewage treatment, metal enrichment, etc. Currently, the methods for synthesizing phosphorus-containing polymers generally include two types. First, polycondensation starting from functionalized phosphine ligand monomers. In this method, functionalized phosphine ligand monomers are used to synthesize phosphorus-containing polymers through coupling polycondensation, radical polycondensation, aldamine polycondensation, etc. However, due to the oxygen sensitivity of trivalent phosphorus, the synthesis and purification of these functionalized phosphine ligand monomers are very difficult, hindering their large-scale preparation. In addition, the methods involving coupling polycondensation require metal catalysts, which not only increase the manufacturing cost but also lead to metal residues. Second, Friedel-Crafts polymerization of arylphosphine ligand monomers catalyzed by Lewis acids. Arylphosphine ligands can polymerize with coupling monomers under the catalysis of Lewis acid catalysts to form phosphorus-containing polymers, but iron chloride or aluminum chloride used for catalysis is prone to hydrolysis to produce hydrochloric acid, and there will be a large amount of metal residues in the polymer. In addition, the state of phosphorus in the phosphorus-containing polymers prepared by this method is still not very certain, and it is questionable which form of trivalent phosphine, quaternary phosphonium salt, or phosphine oxide it exists in. Therefore, an alternative route for preparing phosphorus-containing polymers using non-functionalized phosphine ligands and non-metal catalysts is very urgent.

[0003] Fluorine-containing polymer materials have unique hydrophobicity, thermal stability, and carbon dioxide affinity, and have been applied in the synthesis of phosphorus-containing polymers. For example, the synthesis of fluorinated phosphorus-containing heteroaromatic polymers includes two steps: First, a polymer containing pyranylium salts is prepared under the catalysis of BF 3 ·Et 2 O; in the second step, P(Me 3 Si) 3 is used to convert the pyranylium salt into a phosphaheteroaromatic group. However, the synthesis of monomers in this method is relatively complex, and the types of synthesized phosphorus are limited to phosphaheteroaromatics, so the application is very limited. Summary of the Invention

[0004] In order to achieve the simple synthesis of phosphorus-containing polymers, the present invention provides a method for synthesizing phosphorus-containing polymers through a Friedel-Crafts polymerization catalyzed by a protonic acid.

[0005] The method for synthesizing a phosphorus-containing polymer of the present invention is to use a phosphorus-containing monomer and a fluorine-containing monomer as raw materials, a protonic acid as a catalyst and a solvent, and carry out a polymerization reaction at 80 - 140 °C for 4 - 48 h in a vacuum environment; after the reaction is completed, the reaction system is cooled and quenched with water, and the insoluble solid is filtered, washed, and dried to obtain the phosphorus-containing polymer.

[0006] The phosphorus-containing monomer is a phosphine ligand with an aryl structure, and its structure is as follows:

[0007]

[0008] The phosphorus-containing monomer can also be a phosphine ligand complex with an aryl structure, and its structure is as follows:

[0009]

[0010] The phosphorus-containing monomer can also be an oxidized phosphine ligand with an aryl structure, such as triphenylphosphine oxide, 1,2-bis(diphenylphosphino)ethane oxide, etc.

[0011] The phosphorus-containing monomer can also be a quaternary phosphonium salt with an aryl structure; such as triphenylpropylphosphonium bromide, tetraphenylphosphonium bromide, benzyltriphenylphosphonium chloride, etc.

[0012] The structure of the fluorine-containing monomer is as follows:

[0013]

[0014] The phosphorus-containing monomer and the fluorine-containing monomer are proportioned in a molar ratio of 1:2 to 1:8.

[0015] The protonic acid catalyst is formic acid, acetic acid, trifluoroformic acid, trifluoromethanesulfonic acid, concentrated sulfuric acid, concentrated nitric acid, concentrated hydrochloric acid, etc., and trifluoromethanesulfonic acid is preferred. The protonic acid serves as both a catalyst and a solvent for the Friedel-Crafts polymerization, and its amount should be sufficient for the reaction to occur fully.

[0016] Solid state 13 From the characterization results of the C MAS NMR spectrum, it can be seen that the synthesized phosphorus-containing polymer in the present invention contains aryl structures and methylene groups, indicating the feasibility of the Friedel-Crafts polymerization catalyzed by protonic acid.

[0017] Solid state 31 The P MAS NMR spectrum shows that the phosphorus in the phosphorus-containing polymer after polymerization is still trivalent phosphorus and is not destroyed during the reaction. The trivalent phosphine site has a good coordination effect on transition metals, which is beneficial to the further application of the polymer, such as loading metals to prepare heterogeneous catalysts, serving as an adsorbent material for transition metals in wastewater, etc.

[0018] The nitrogen adsorption isotherm shows that the synthesized phosphorus-containing polymer in the present invention has a certain pore structure and swelling performance, which is beneficial to the further application of the polymer, such as being beneficial to mass transfer when used as a heterogeneous catalyst and increasing the adsorption capacity when used as an adsorbent material, etc.

[0019] In summary, the present invention uses a phosphorus-containing monomer and a fluorine-containing monomer as raw materials, and a protonic acid as a catalyst and a solvent to synthesize a phosphorus-containing polymer through a Friedel-Crafts polymerization reaction. On the one hand, the use of a metal catalyst is avoided, there is no problem of metal residue, and at the same time, the synthesis cost of the phosphorus-containing polymer is reduced; on the other hand, the protonic acid also serves as a solvent, avoiding the use of other organic solvents, which not only reduces the cost but also is environmentally friendly and green; in addition, the synthesis method of the present invention is simple and the conditions are mild, which is conducive to popularization and expansion. Description of the Drawings

[0020] Figure 1 Solid state 13 C MAS NMR spectrum of phosphorus-containing polymer 1.

[0021] Figure 2 Solid state 31 P MAS NMR spectrum of phosphorus-containing polymer 1.

[0022] Figure 3 BET adsorption isotherm of phosphorus-containing polymer 1.

[0023] Figure 4 BET adsorption isotherm of phosphorus-containing polymer 4.

[0024] Figure 5 Photos of phosphorus-containing polymer 5 before (left) and after (right) adsorbing dichloromethane. Detailed Description of the Invention

[0025] The synthesis, structure and properties of the phosphorus-containing polymer of the present invention will be further described below in conjunction with specific embodiments.

[0026] Example 1

[0027] Triphenylphosphine (0.13 g, 0.5 mmol) and 2,3,5,6-tetrafluoroterephthalyl alcohol (0.32 g, 1.5 mmol) were charged into a 50 mL Schlenk reaction flask, and then 8 mL of trifluoromethanesulfonic acid was added; the flask was placed in a liquid nitrogen bath (77K), and the air in the flask was evacuated using a vacuum pump, and after sealing, it was slowly warmed to room temperature; this step was repeated twice to remove air as much as possible. The sealed reaction flask was placed in an ultrasonic bath and ultrasonically treated for 10 minutes, and then the flask was placed in an oil bath and heated to 100 °C for reaction for 24 hours. Then the flask was cooled to 0 °C, and after opening the reaction flask, it was quenched with 30 mL of degassed deionized water, filtered by suction, and the obtained brown solid product was pulverized and washed successively with deionized water (100 mL), ethanol (100 mL), tetrahydrofuran (100 mL) and dichloromethane (100 mL), and the obtained brown solid was dried in vacuo at 50 °C for 24 hours to obtain 0.36 g of phosphorus-containing polymer 1. Its synthesis formula is shown as follows:

[0028]

[0029] Figure 1 For the solid state of the prepared phosphorus-containing polymer 1 13 C MAS NMR spectrum. It can be seen from Figure 1 the NMR characterization results that the phosphorus-containing polymer 1 contains aryl structures and methylene groups.

[0030] Figure 2 For the solid state of the phosphorus-containing polymer 1 31 P MAS NMR spectrum. Figure 2 The results show that the phosphorus in the phosphorus-containing polymer 1 remains trivalent after the polymerization of triphenylphosphine and is not destroyed during the reaction process.

[0031] Figure 3 For the BET adsorption isotherm of the phosphorus-containing polymer 1. The nitrogen adsorption isotherm shows that the specific surface area of the phosphorus-containing polymer 1 is 94.5 m 2 / g, and the pore volume is 0.14 cm 3 / g, indicating that the phosphorus-containing polymer 1 has certain pore structure properties, which are beneficial to the further application of the polymer, such as loading metals to prepare heterogeneous catalysts and using it as an adsorbent material for transition metals in wastewater, etc.

[0032] Example 2

[0033] Charge triphenylphosphine (0.13 g, 0.5 mmol) and 2,3,5,6-tetrafluoroterephthalyl alcohol (0.16 g, 0.75 mmol) into a 50 mL Schlenk reaction flask, then add 2 mL of trifluoromethanesulfonic acid; place the flask in a liquid nitrogen bath (77 K), use a vacuum pump to evacuate the air in the bottle, seal it and slowly warm it up to room temperature; repeat this step twice to remove air as much as possible. Seal the reaction flask and ultrasonicate it for 10 minutes, then place the flask in an oil bath and heat it to 120 °C for reaction for 24 hours. Then cool the flask to 0 °C, open the reaction flask and quench it with 30 mL of degassed deionized water, filter by suction, crush the obtained brown solid product, wash it successively with deionized water (100 mL), ethanol (100 mL), tetrahydrofuran (100 mL) and dichloromethane (100 mL), and dry the obtained brown solid in vacuo at 50 °C for 24 hours to obtain 0.25 g of phosphorus-containing polymer 2. Compared with the phosphorus-containing polymer 1, this polymer uses less 2,3,5,6-tetrafluoroterephthalyl alcohol and has a higher phosphorus content.

[0034] Example 3

[0035] Triphenylphosphine (0.13 g, 0.5 mmol) and 2,3,5,6-tetrafluoroterephthalic alcohol (0.21 g, 1.0 mmol) were charged into a 50 mL Schlenk reaction flask, and then 2 mL of trifluoromethanesulfonic acid was added. The flask was placed in a liquid nitrogen bath (77 K), and the air in the flask was evacuated using a vacuum pump. After sealing, it was slowly warmed to room temperature; this step was repeated twice to remove air as much as possible. The sealed reaction flask was sonicated for 10 minutes and then placed in an oil bath and heated to 120 °C for 24 hours. Then the flask was cooled to 0 °C. After opening the reaction flask, it was quenched with 30 mL of degassed deionized water, filtered by suction. The obtained brown solid product was crushed. The brown solid was crushed and washed successively with deionized water (100 mL), ethanol (100 mL), tetrahydrofuran (100 mL), and dichloromethane (100 mL). The obtained brown solid was dried in vacuo at 50 °C for 24 hours to obtain 0.29 g of phosphorus-containing polymer 3. Compared with phosphorus-containing polymer 1, this polymer uses less 2,3,5,6-tetrafluoroterephthalic alcohol and has a higher phosphorus content; compared with phosphorus-containing polymer 2, this polymer uses more 2,3,5,6-tetrafluoroterephthalic alcohol and has a lower phosphorus content.

[0036] Through the comparison of Examples 1 - 3, the amount of the linking monomer 2,3,5,6-tetrafluoroterephthalic alcohol used was adjusted within a certain range, thereby adjusting the phosphorus content of the polymer. However, there were certain differences in the polymerization temperatures required for different amounts of the linking monomer.

[0037] Example 4

[0038] Triphenylphosphine oxide (0.14 g, 0.5 mmol) and 2,3,5,6-tetrafluoroterephthalic alcohol (0.32 g, 1.5 mmol) were charged into a 50 mL Schlenk reaction flask, and then 8 mL of trifluoromethanesulfonic acid was added. The flask was placed in a liquid nitrogen bath (77 K), and the air in the flask was evacuated using a vacuum pump. After sealing, it was slowly warmed to room temperature; this step was repeated twice to remove air as much as possible. The sealed reaction flask was sonicated for 10 minutes and then placed in an oil bath and heated to 140 °C for 24 hours. Then the flask was cooled to 0 °C. After opening the reaction flask, it was quenched with 30 mL of degassed deionized water, filtered by suction. The obtained brown solid product was crushed and washed successively with deionized water (100 mL), ethanol (100 mL), tetrahydrofuran (100 mL), and dichloromethane (100 mL). The obtained brown solid was dried in vacuo at 50 °C for 24 hours to obtain 0.38 g of phosphorus-containing polymer 4. Its synthesis formula is shown as follows:

[0039]

[0040] Figure 4 is the BET adsorption isotherm of phosphorus-containing polymer 4. The nitrogen adsorption isotherm shows that the specific surface area of phosphorus-containing polymer 4 is 358 m 2 / g, the pore volume is 0.37 cm 3 / g, indicating that the phosphorus-containing polymer 4 has a certain pore structure and can be used as an adsorption material in specific scenarios. In addition, the successful synthesis of the phosphorus-containing polymer 4 shows that this method can polymerize arylphosphine oxide monomers with relatively low polymerization activity, demonstrating the applicability of this method.

[0041] Example 5

[0042] Bis(diphenylphosphino)methane (0.19 g, 0.5 mmol) and 2,3,5,6-tetrafluoroterephthalyl alcohol (0.42 g, 2.0 mmol) were placed in a 50 mL Schlenk reaction flask, and then 8 mL of trifluoromethanesulfonic acid was added; the flask was placed in a liquid nitrogen bath (77 K), and the air in the flask was evacuated using a vacuum pump, and after sealing, it was slowly warmed to room temperature; this step was repeated twice to remove air as much as possible. The sealed reaction flask was sonicated for 10 minutes and then placed in an oil bath and heated to 100 °C for 24 hours. Then the flask was cooled to 0 °C, and after opening the reaction flask, it was quenched with 30 mL of degassed deionized water, filtered by suction, the obtained brown solid product was crushed, and washed successively with deionized water (100 mL), ethanol (100 mL), tetrahydrofuran (100 mL), and dichloromethane (100 mL). The obtained brown solid was dried in vacuo at 50 °C for 24 hours to obtain 0.51 g of phosphorus-containing polymer 5. Its synthesis formula is shown as follows:

[0043]

[0044] Figure 5 Photos of the phosphorus-containing polymer 5 before (left) and after (right) adsorbing dichloromethane. From Figure 5 it can be seen that the phosphorus-containing polymer 5 has excellent swelling performance in solvents. The successful synthesis of the phosphorus-containing polymer 5 shows that this method can synthesize polymers containing bidentate phosphine ligands, and the swelling performance exhibited by this polymer makes it useful as an adsorption material or a catalyst support. For example, the rich fluorine element makes the polymer have good hydrophobicity, and this material can be used to selectively adsorb halogen-containing organic compounds in wastewater.

[0045] Example 6

[0046] Charge palladium tetrakis(triphenylphosphine) (0.58 g, 0.5 mmol) and 2,3,5,6-tetrafluoroterephthalyl alcohol (1.26 g, 6 mmol) into a 50 mL Schlenk reaction flask, then add 8 mL of trifluoromethanesulfonic acid; place the flask in a liquid nitrogen bath (77 K), use a vacuum pump to evacuate the air in the flask, seal it and slowly warm it to room temperature; repeat this step twice to remove air as much as possible. After the sealed reaction flask is sonicated for 10 minutes, place the flask in an oil bath and heat it to 120 °C for reaction for 72 hours. Then cool the flask to 0 °C, open the reaction flask and quench it with 30 mL of degassed deionized water, filter it by suction, crush the obtained brown solid product, and wash it successively with deionized water (100 mL), ethanol (100 mL), tetrahydrofuran (100 mL) and dichloromethane (100 mL). The obtained brown solid is dried in vacuo at 50 °C for 24 hours to obtain 1.61 g of phosphorus-containing polymer 6. Its synthetic formula is shown as follows:

[0047]

[0048] Phosphorus-containing polymer 6 not only contains abundant phosphine ligand coordination sites, but also contains transition metal palladium, and can be directly used as a heterogeneous catalyst for Suzuki, Kumada, Negishi and other coupling reactions.

[0049] As can be seen from Examples 1-6, different types of aryl phosphorus-containing monomers can all be polymerized by this method. The synthesized polymers, such as phosphorus-containing polymers 1-3, contain different concentrations of phosphorus sites and fluorine contents. Among them, due to the phosphorus sites in the polymer that can coordinate with transition metals, they can be directly used as adsorption materials for transition metals, or loaded with metals for catalytic reactions. The successful synthesis of phosphorus-containing polymer 4 shows that this method can polymerize arylphosphine oxide monomers with relatively low polymerization activity, indicating the applicability of this method. The successful synthesis of phosphorus-containing polymer 5 shows that this method can synthesize polymers containing bidentate phosphine ligands, and the swelling properties exhibited by this polymer make it useful as an adsorption material or a catalyst support. The successful synthesis of phosphorus-containing polymer 6 further demonstrates the generality of this method, and this phosphorus-containing polymer not only contains phosphine ligands, but also reductively introduces transition metal palladium, and can be directly used as a catalytic material.

Claims

1. A method for preparing a phosphorus-containing polymer by Friedel-Crafts polymerization catalyzed by a protonic acid, which is carried out in a vacuum environment using a phosphorus-containing monomer and a fluorine-containing monomer as raw materials, and a protonic acid as a catalyst and a solvent, and polymerizing at 80-140 °C for 4-48 h; after the reaction is completed, the reaction system is cooled and quenched with water, and the insoluble solid is filtered, washed and dried to obtain the phosphorus-containing polymer; The structure of the fluorine-containing monomer is as follows: 。 2. The method for preparing a phosphorus-containing polymer by Friedel-Crafts polymerization catalyzed by a protonic acid as described in claim 1, characterized in that: The phosphorus-containing monomer is a phosphine ligand with an aryl structure, and its structure is as follows: 。 3. The method for preparing a phosphorus-containing polymer by Friedel-Crafts polymerization catalyzed by a protonic acid as described in claim 1, characterized in that: The phosphorus-containing monomer is a phosphine ligand complex with an aryl structure, and its structure is as follows: 。 4. The method for preparing a phosphorus-containing polymer by Friedel-Crafts polymerization catalyzed by a protonic acid as described in claim 1, characterized in that: The phosphorus-containing monomer is an oxidized phosphine ligand with an aryl structure.

5. The method for preparing a phosphorus-containing polymer by Friedel-Crafts polymerization catalyzed by a protonic acid as described in claim 4, characterized in that: The oxidized phosphine ligand with an aryl structure is triphenylphosphine oxide, 1,2-bis(diphenylphosphino)ethane oxide.

6. The method for preparing a phosphorus-containing polymer by Friedel-Crafts polymerization catalyzed by a protonic acid as described in claim 1, characterized in that: The phosphorus-containing monomer is a quaternary phosphonium salt with an aryl structure.

7. The method for preparing a phosphorus-containing polymer by Friedel-Crafts polymerization catalyzed by a protonic acid as described in claim 6, characterized in that: The quaternary phosphonium salt with an aryl structure is triphenylpropylphosphonium bromide, tetraphenylphosphonium bromide, benzyltriphenylphosphonium chloride.

8. The method for preparing a phosphorus-containing polymer by Friedel-Crafts polymerization catalyzed by a protonic acid as described in claim 1, characterized in that: The phosphorus-containing monomer and the fluorine-containing monomer are proportioned in a molar ratio of 1:2 to 1:

8.

9. The method for preparing a phosphorus-containing polymer by Friedel-Crafts polymerization catalyzed by a protonic acid as described in claim 1, characterized in that: The protonic acid catalyst is formic acid, acetic acid, trifluoroformic acid, trifluoromethanesulfonic acid, concentrated sulfuric acid, concentrated nitric acid, concentrated hydrochloric acid.

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