Carbon dioxide-based superabsorbent material and method for preparing the same

Abstract

The application provides a carbon dioxide-based superabsorbent material. The main chain of the CO2-based superabsorbent material is a degradable carbonate group, which can be completely degraded after use without causing harm to the environment, and a biologically based monomer such as oxidized limonene can be used to reduce the consumption of chemical raw materials. Compared with other degradable materials, the superabsorbent material has more excellent water absorption performance. The superabsorbent material can be conveniently and quickly prepared by using efficient 'thiol-ene' click reaction and fast nucleophilic substitution reaction crosslinking, the preparation method is fast and efficient, the superabsorbent material is very stable after water absorption, has excellent repeated water absorption performance, and is not prone to mold or corruption, and can be used for a long time. Meanwhile, the preparation method can fix and utilize CO2, and has important significance for the fixation and utilization of CO2.

Description

Technical Field

[0001] This invention relates to the field of materials technology, and in particular to a carbon dioxide-based superabsorbent material and its preparation method. Background Technology

[0002] Superabsorbent polymers (SAPs) are a typical class of functional polymer materials that play an important role in our lives, used in products such as agriculture, hygiene, and construction. Among them, the largest proportion is used in disposable diapers and adult hygiene products.

[0003] Non-degradable SAP materials are difficult to recycle after use due to their high liquid content, or are difficult to regenerate through incineration, making them a major source of primary microplastics and causing incalculable harm to the ecosystem.

[0004] To address this problem, researchers are continuously developing biodegradable SAP materials. These include SAP materials prepared using natural polymers such as starch, cellulose, chitosan, proteins, and polyamino acids, which introduce biodegradable glycosidic and amide bonds into the polymer chain. There are also biodegradable SAP materials prepared by introducing ester bonds.

[0005] However, most of these substances are prepared by graft copolymerization with acrylic acid and its derivatives, sacrificing some of their biodegradability and failing to achieve 100% degradation. Furthermore, due to the high crystallinity or numerous hydrogen bonds within the polysaccharide system, they are insoluble in many solvents, posing problems in their preparation and production. Additionally, polysaccharides are susceptible to microbial contamination, leading to mold or spoilage. Starch-based polysaccharides slowly hydrolyze when absorbing water, resulting in pectinization, making these types of SAPs unsuitable for long-term use. Summary of the Invention

[0006] In view of this, the technical problem to be solved by the present invention is to provide a carbon dioxide-based superabsorbent material and its preparation method, wherein the carbon dioxide-based superabsorbent material has high stability after absorbing water, excellent repeated water absorption performance, and can be used for a long time.

[0007] This invention provides a method for preparing a carbon dioxide-based superabsorbent material, comprising the following steps:

[0008] S1) Polycarbonate is prepared by ring-opening copolymerization of epoxy monomers with double bonds and CO2.

[0009] S2) Hydrophilic groups are introduced into the above polycarbonate groups using a "thiol-ene" click reaction;

[0010] S3) Using a nucleophilic substitution reaction, the polycarbonate with introduced hydrophilic groups is cross-linked to obtain a gel;

[0011] S4) The above gel is directly freeze-dried, or the above gel is neutralized into salt in an alkaline solution and then freeze-dried to obtain a carbon dioxide-based superabsorbent material.

[0012] Optionally, the epoxy monomer with double bonds is selected from one or more of allyl glycidyl ether, allyl glycidyl carbonate, 1,2-epoxy-4-cyclohexene, 1,2-epoxy-3-cyclohexene, 1,2-epoxy-4-vinylcyclohexane, limonene oxide, and 2-vinyl ethylene oxide.

[0013] Optionally, the hydrophilic group introduced in step S2) is one or more of amino, hydroxy, carboxyl, and sulfonic acid groups.

[0014] Optionally, the reagent structure for performing the "thiol-ene" click reaction contains a thiol group and one or more of an amino, hydroxyl, carboxyl, or sulfonic acid group.

[0015] Optionally, the reagent for performing the "thiol-ene" click reaction has any of the following structures:

[0016] HS-R1-COOH, HS-R2-OH, HS-R3-NH2, HS-R4-SO3H, HS-R4-SO3Na;

[0017] Wherein, R1 is selected from substituted or unsubstituted C1-C5 alkyl groups; the substituents of the C1-C5 alkyl groups are selected from amino groups;

[0018] R2, R3, and R4 are independently selected from C1 to C5 alkyl groups.

[0019] Optionally, the reagent used to perform the "thiol-ene" click reaction is selected from one or more of the following: mercaptoacetic acid, mercaptopropionic acid, mercaptosuccinic acid, mercaptoethanol, mercaptopropanol, mercaptoethylamine, mercaptopropylamine, sodium 3-mercapto-1-propanesulfonate, 2-mercaptoethanesulfonic acid, and cysteine.

[0020] Optionally, the reagent for performing the nucleophilic substitution reaction is selected from one or more of the following: epoxy resin, 1,6-dibromohexane, 1,12-dibromododecane, 1,2-ethylenediamine, 1,6-hexanediamine, succinic acid, glutaric acid, polyethylene glycol diglycidyl ether, poly(propylene glycol) diglycidyl ether, tris(2-aminoethyl)amine, ethylene glycol bis(3-aminopropyl) ether, and citric acid.

[0021] Optionally, the ring-opening copolymerization reaction is carried out in the presence of a catalyst.

[0022] Optionally, the catalyst is selected from one or more of the following: tetrabromomonoporphyrin aluminum catalyst, zinc-cobalt bimetallic cyanide complex catalyst, β-diimine zinc catalyst, salon cobalt / bis(triphenylphosphine)dinitrophenol ammonium catalyst, and bifunctional salon Co catalyst.

[0023] Optionally, a co-catalyst may be added to the catalyst. Optionally, the co-catalyst is selected from bis(triphenylphosphine)ammonium chloride.

[0024] Optionally, the condensing agent for the crosslinking reaction is selected from 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxythiosuccinimide.

[0025] Optionally, magnetic nanoparticles are also added in step S3) to obtain a magnetic carbon dioxide-based superabsorbent material.

[0026] In some specific embodiments of the present invention, the magnetic nanoparticles are iron oxide nanoparticles.

[0027] Optionally, the alkaline solution is added in excess.

[0028] Optionally, the alkaline solution is selected from sodium bicarbonate solution.

[0029] Optionally, the concentration of the sodium bicarbonate solution is 0.1–0.5 mol / L, preferably 0.15 mol / L.

[0030] This invention provides a carbon dioxide-based superabsorbent material prepared by the above-described preparation method.

[0031] The carbon dioxide-based superabsorbent material prepared by this invention has a three-dimensional network structure.

[0032] Compared with existing technologies, this invention provides a carbon dioxide-based superabsorbent material. The main chain of the CO2-based superabsorbent material provided by this invention is a biodegradable carbonate group, which can be completely degraded after use without causing harm to the environment. Moreover, it can use bio-based monomers such as limonene oxide, reducing the consumption of chemical raw materials.

[0033] Compared with other biodegradable materials, it has superior water absorption properties. It can be conveniently and quickly prepared by using efficient "thiol-ene" click reaction and rapid nucleophilic substitution crosslinking. The preparation method is fast and efficient. The material is very stable after absorbing water, has excellent repeated water absorption performance, is not prone to mold or spoilage, and can be used for a long time.

[0034] Meanwhile, the preparation method of the present invention can fix and utilize CO2, which is of great significance for the fixation and utilization of CO2. Attached Figure Description

[0035] Figure 1 The hydrogen spectroscopy spectrum of the product of tetrabromomonoporphyrin aluminum / bis(triphenylphosphino)ammonium chloride catalyzed polymerization of allyl glycidyl ether and CO2;

[0036] Figure 2 The hydrogen spectrum of the product after the click reaction of allyl glycidyl ether, CO2, polycarbonate, and mercaptoacetic acid;

[0037] Figure 3 The infrared spectrum of the freeze-dried product after neutralization with sodium bicarbonate following the crosslinking reaction of ethylene glycol bis(3-aminopropyl) ether;

[0038] Figure 4 Hydrogen spectra of the polymerization products of 1,2-epoxy-4-vinylcyclohexane and CO2 catalyzed by zinc-cobalt bimetallic cyanide complex catalyst;

[0039] Figure 5 The hydrogen spectrum of the product after the click reaction of 1,2-epoxy-4-vinylcyclohexane and CO2 with polycarbonate and mercaptoacetic acid;

[0040] Figure 6 The infrared spectrum of the freeze-dried product after neutralization with sodium bicarbonate following the crosslinking reaction of tris(2-aminoethyl)amine;

[0041] Figure 7 The hydrogen spectrum of the product after the click reaction of 1,2-epoxy-4-vinylcyclohexane and CO2 with polycarbonate and mercaptosuccinic acid;

[0042] Figure 8 The infrared spectrum of the freeze-dried product after neutralization with sodium bicarbonate following the 1,6-hexanediamine crosslinking reaction;

[0043] Figure 9 The hydrogen spectrum of the polymerization products of limonene and CO2 catalyzed by zinc β-diimine catalyst;

[0044] Figure 10 The hydrogen spectrum of the products after the click reaction of limonene oxide, CO2, polycarbonate, and mercaptosuccinic acid.

[0045] Figure 11 The infrared spectrum of the freeze-dried product after neutralization with sodium bicarbonate following the crosslinking reaction of 1,12-dibromododecane.

[0046] Figure 12 The hydrogen spectrum of the polymerization product of 1,2-epoxy-3-cyclohexene and CO2 catalyzed by salen Co / bis(triphenylphosphine)dinitrophenolammonium;

[0047] Figure 13 The hydrogen spectrum of the product after the click reaction of 1,2-epoxy-3-cyclohexene with CO2, polycarbonate and mercaptoacetic acid;

[0048] Figure 14 The infrared spectrum of the freeze-dried product after E-44 epoxy resin crosslinking reaction and neutralization with sodium bicarbonate to form salt is shown.

[0049] Figure 15 The hydrogen spectrum of the product after the click reaction of 1,2-epoxy-4-vinylcyclohexane and CO2 with polycarbonate and mercaptosuccinic acid;

[0050] Figure 16 The infrared spectrum of the freeze-dried product after neutralization with sodium bicarbonate following the crosslinking reaction of 1,12-dibromododecane.

[0051] Figure 17 The hydrogen spectrum of the product of the polymerization of 2-vinyl ethylene oxide and CO2 catalyzed by bifunctional salon Co;

[0052] Figure 18 The hydrogen spectrum of the product after the click reaction of 2-vinyl ethylene oxide, CO2, polycarbonate, and mercaptoethanol;

[0053] Figure 19 The infrared spectrum of the freeze-dried product after the citric acid crosslinking reaction and neutralization with sodium bicarbonate.

[0054] Figure 20 The infrared spectrum of the freeze-dried product after crosslinking reaction of polyethylene glycol diglyoxyethylene methyl ether and neutralization with sodium bicarbonate is shown.

[0055] Figure 21 The image shows the SEM pattern of the freeze-dried product after neutralization with sodium bicarbonate following the crosslinking reaction of tris(2-aminoethyl)amine.

[0056] Figure 22 SEM image of the freeze-dried product after neutralization with sodium bicarbonate following the crosslinking reaction of 1,12-dibromododecane;

[0057] Figure 23 This is the SEM image of the freeze-dried product after the crosslinking reaction of E-44 epoxy resin and neutralization with sodium bicarbonate. Detailed Implementation

[0058] To further illustrate the present invention, the following detailed description of a carbon dioxide-based superabsorbent material and its preparation method provided by the present invention is provided in conjunction with embodiments.

[0059] Example 1

[0060] (a) Polymerization reaction: 41 mg of tetrabromomonoporphyrin aluminum catalyst with chlorine as the axial group, 24 mg of bis(triphenylphosphine)ammonium chloride co-catalyst, and 34 mL of allyl glycidyl ether monomer were successively added to a 50 mL high-pressure polymerization reactor under anhydrous and oxygen-free conditions. The reactor was then purged with 3.5 MPa of CO2 gas. After stabilization, the reactor was heated and stirred in a 60 °C oil bath for 48 h. After opening the reactor, the product was dissolved and precipitated three times using dichloromethane and methanol (with 1 drop of concentrated hydrochloric acid added), followed by vacuum drying to obtain 7.93 g of polycarbonate with a carbonate content of 99.25%. The proton NMR spectrum is shown below. Figure 1 As shown.

[0061] (b) "Mercapto-Alkene" Click Reaction: Under anhydrous and oxygen-free conditions, 7.93 g of the polymerized polycarbonate was dissolved in 100 mL of anhydrous tetrahydrofuran solvent. 2.72 g of azobisisobutyronitrile (AIBN) and 34.89 mL of mercaptoacetic acid were added to the reaction flask. The flask was connected to a nitrogen balloon and placed in a 60°C oil bath with stirring for 24 h. After the reaction was complete, the precipitate was dissolved three times with a mixed solvent of tetrahydrofuran, methanol, and water (v / v = 1:1), and then dried under vacuum to obtain 9.12 g of the product. The proton NMR spectrum is shown below. Figure 2 As shown.

[0062] (c) Take 0.5 g of the click reaction product and dissolve it in 2.5 mL of 2-morpholinoethanesulfonic acid buffer solution with a pH of approximately 5. Add 0.38 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 0.12 g of N-hydroxythiosuccinimide slowly to the buffer solution while stirring. After 40 min, the solution becomes clear and transparent. Dissolve 53 μL of ethylene glycol bis(3-aminopropyl) ether in 0.5 mL of 2-morpholinoethanesulfonic acid buffer solution and add it dropwise to the reaction flask while stirring. After reacting at room temperature for 2 h, it becomes a gel. Cut the gel into small pieces and soak them overnight in 15 mL of 0.15 mol / L sodium bicarbonate solution, then freeze-dry to obtain a CO2-based superabsorbent material. Its water absorption ratio is 79.46 g / g. The infrared spectrum of the superabsorbent material is shown below. Figure 3 As shown.

[0063] Example 2

[0064] (a) Polymerization reaction: 5 mg of zinc-cobalt bimetallic cyanide complex catalyst, 20 mL of 1,2-epoxy-4-vinylcyclohexane monomer, and 20 mL of anhydrous dichloromethane solvent were successively added to a 75 mL high-pressure polymerization reactor under anhydrous and oxygen-free conditions. CO2 gas at 3.0 MPa was introduced into the reactor at room temperature, and the reactor was heated and stirred in a 70 °C oil bath. After the CO2 pressure stabilized, it was further introduced to 6.0 MPa, approximately 20 g of CO2 gas, and then heated and stirred in a 70 °C oil bath for 12 h. After opening the reactor, the product was dissolved and precipitated three times using dichloromethane and methanol, and then vacuum dried to obtain 16.26 g of polycarbonate with a carbonate content of 96.95%. The proton NMR spectrum is shown below. Figure 4 As shown.

[0065] (b) "Mercapto-Alkene" Click Reaction: Under anhydrous and oxygen-free conditions, 8.66 g of the polymerized polycarbonate was dissolved in 150 mL of anhydrous tetrahydrofuran solvent. 2.83 g of azobisisobutyronitrile (AIBN) and 18.14 mL of mercaptoacetic acid were added to the reaction flask. The flask was connected to a nitrogen balloon and placed in a 60°C oil bath with stirring for 24 h. After the reaction was complete, the precipitate was dissolved three times with a mixed solvent of tetrahydrofuran, methanol, and water (v / v = 1:1), and then dried under vacuum to obtain 12.36 g of the product. The proton NMR spectrum is shown below. Figure 5 As shown.

[0066] (c) Crosslinking reaction: Take 1.05 g of the click reaction product and dissolve it in 10 mL of tetrahydrofuran. Slowly add 4.30 mL of saturated sodium bicarbonate solution to the solution. After no more bubbles are generated, add diethyl ether to precipitate the product. Use a plastic dropper to remove the upper liquid. Dissolve the lower gelatinous precipitate in 200 mL of deionized water. After stirring, use an oil pump to remove the solvent and obtain a white powder. Take 0.73 g of the white powder and dissolve it in 3.0 mL of 2-morpholine ethanesulfonic acid buffer with a pH of approximately 5. In a solution, 0.50 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 0.15 g of N-hydroxythiosuccinimide were slowly added to a buffer solution while stirring. After 40 min, the solution became clear and transparent. 0.39 mL of tris(2-aminoethyl)amine was dissolved in 1.0 mL of 2-morpholinoethanesulfonic acid buffer solution. 139 μL of the mixed solution was then slowly added dropwise to the reaction flask while stirring. After reacting at room temperature for 2 h, it became a gel. The gel was cut into small pieces and soaked overnight in 15 mL of 0.15 mol / L sodium bicarbonate solution, followed by freeze-drying to obtain a CO2-based superabsorbent material. Its water absorption ratio was 61.20 g / g. The infrared spectrum of the superabsorbent material is shown below. Figure 6 As shown. The SEM image of the absorbent material is shown below. Figure 21 As shown.

[0067] Example 3

[0068] (a) Polymerization reaction: 5 mg of zinc-cobalt bimetallic cyanide complex catalyst, 20 mL of 1,2-epoxy-4-vinylcyclohexane monomer, and 20 mL of anhydrous dichloromethane solvent were successively added to a 75 mL high-pressure polymerization reactor under anhydrous and oxygen-free conditions. CO2 gas at 3.0 MPa was introduced into the reactor at room temperature, and the reactor was heated and stirred in a 70 °C oil bath. After the CO2 pressure stabilized, it was introduced to 6.0 MPa and about 20 g of CO2 gas. Then, the reactor was heated and stirred in a 70 °C oil bath for 12 h. After the reactor was opened, the product was dissolved and precipitated three times with dichloromethane and methanol and then dried under vacuum to obtain 16.26 g of polycarbonate with a carbonate content of 96.95%.

[0069] (b) "Mercapto-Alkene" Click Reaction: Under anhydrous and oxygen-free conditions, 5.89 g of the polymerized polycarbonate was dissolved in 120 mL of anhydrous tetrahydrofuran solvent. 0.64 g of azobisisobutyronitrile and 17.78 g of mercaptosuccinic acid were added to the reaction flask. The flask was connected to a nitrogen balloon and placed in a 60°C oil bath with stirring for 24 h. After the reaction was complete, the precipitate was dissolved three times with a mixed solvent of tetrahydrofuran, methanol, and water (v / v = 1:1), and then dried under vacuum to obtain 9.78 g of the product. The proton NMR spectrum of the product is shown below. Figure 7 As shown.

[0070] (c) Crosslinking reaction: Take 0.98 g of the click reaction product and dissolve it in 5 mL of tetrahydrofuran. Slowly add 6.10 mL of saturated sodium bicarbonate solution to the solution. After no more bubbles are generated, add diethyl ether to precipitate the product. Use a plastic dropper to remove the upper liquid. Dissolve the lower gelatinous precipitate in 100 mL of deionized water. After stirring, use an oil pump to remove the solvent and obtain a white powder. Take 0.90 g of the white powder and dissolve it in 2.0 mL of 2-morpholine ethanesulfonic acid buffer solution with a pH of about 5. Add 0.96 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 0.29 g of N-hydroxythiosuccinimide to the buffer solution while stirring. After 40 min, the solution becomes clear and transparent. Dissolve 50 μL of 1,6-hexanediamine in 0.5 mL of 2-morpholine ethanesulfonic acid buffer solution and slowly add it to the reaction flask while stirring. After reacting at room temperature for 2 h, it becomes gel-like. The gel was cut into small pieces and soaked overnight in 15 mL of 0.15 mol / L sodium bicarbonate solution, followed by freeze-drying to obtain a CO2-based superabsorbent material. Its water absorption ratio was 70.34 g / g. The infrared spectrum of the superabsorbent material is shown below. Figure 8 As shown.

[0071] Example 4

[0072] (a) Polymerization reaction: 18 mg of β-diimine zinc catalyst and 3.8 mL of limonene oxide monomer were successively added to a 5 mL high-pressure polymerization reactor under anhydrous and oxygen-free conditions. The reactor was then purged with 100 psi of CO2 gas. After stabilization, the reactor was heated and stirred in a 50 °C oil bath for 2 h. After opening the reactor, the product was dissolved and precipitated three times using dichloromethane and methanol, followed by vacuum drying to obtain 5.93 g of polycarbonate with a 100% carbonate content. The proton NMR spectrum of the product is shown below. Figure 9 As shown.

[0073] (b) "Mercapto-Alkene" Click Reaction: Under anhydrous and oxygen-free conditions, 5.93 g of the polymerized polycarbonate was dissolved in 100 mL of anhydrous tetrahydrofuran solvent. 1.64 g of azobisisobutyronitrile and 45.37 g of mercaptosuccinic acid were added to the reaction flask. The flask was connected to a nitrogen balloon and placed in a 60°C oil bath with stirring for 24 h. After the reaction was complete, the precipitate was dissolved three times with a mixed solvent of tetrahydrofuran, methanol, and water (v / v = 1:1), and then dried under vacuum to obtain 8.40 g of the product. The proton NMR spectrum of the product is shown below. Figure 10 As shown.

[0074] (c) Crosslinking reaction: 0.93 g of the click reaction product was dissolved in 6 mL of N,N-dimethylformamide. 0.07 g of 4-dimethylaminopyridine was slowly added while stirring. After 30 min, the solution became clear and transparent. 0.09 g of 1,12-dibromododecane was then slowly added while stirring. After reacting at 100 °C for 1 h, a gel formed. The gel was cut into small pieces and soaked in 15 mL of 0.15 mol / L sodium bicarbonate solution overnight, followed by freeze-drying to obtain a CO2-based superabsorbent material. Its water absorption ratio was 80.65 g / g. The infrared spectrum of the superabsorbent material is shown below. Figure 11 As shown. The SEM image of the absorbent material is shown below. Figure 22 As shown.

[0075] Example 5

[0076] (a) Polymerization reaction: 14 mg of Salen cobalt catalyst with 2,4-dinitrophenol as the axial group, 12 mg of bis(triphenylphosphino)dinitrophenol ammonium, and 1.5 mL of 1,2-epoxy-3-cyclohexene monomer were successively added to a 5 mL high-pressure polymerization reactor under anhydrous and oxygen-free conditions. CO2 gas at 2.0 MPa was introduced into the reactor, and after stabilization, the mixture was stirred in a room temperature water bath for 10 h. After opening the reactor, the product was dissolved and precipitated three times using dichloromethane and methanol, and then vacuum dried to obtain 1.28 g of polycarbonate with a 100% carbonate content. The proton NMR spectrum of the product is shown below. Figure 12 As shown.

[0077] (b) "Mercapto-Alkene" Click Reaction: Under anhydrous and oxygen-free conditions, 1.28 g of the polymerized polycarbonate was dissolved in 40 mL of anhydrous tetrahydrofuran solvent. 0.47 g of azobisisobutyronitrile (AIBN) and 15.91 g of mercaptoacetic acid (MGA) were added to the reaction flask. The flask was connected to a nitrogen balloon and placed in a 70°C oil bath with stirring for 24 h. After the reaction was complete, the precipitate was dissolved three times with tetrahydrofuran and ethanol, and then dried under vacuum to obtain 1.98 g of the product. The proton NMR spectrum of the product is shown below. Figure 13 As shown.

[0078] (c) Crosslinking reaction: 0.82 g of the click reaction product was dissolved in 8 mL of N,N-dimethylformamide. 0.13 g of 4-dimethylaminopyridine was slowly added while stirring. After 30 min, the solution became clear and transparent. 0.59 g of E-44 epoxy resin was dissolved in 0.5 mL of N,N-dimethylformamide and slowly added while stirring. After reacting at 100℃ for 1 h, it became a gel. The gel was cut into small pieces and soaked overnight in 15 mL of 0.15 mol / L sodium bicarbonate solution, then freeze-dried to obtain a CO2-based superabsorbent material. Its water absorption ratio was 64.20 g / g. The infrared spectrum of the superabsorbent material is shown below. Figure 14 As shown. The SEM image of the absorbent material is shown below. Figure 23 As shown.

[0079] Example 6

[0080] (a) Polymerization reaction: 10 mg of zinc-cobalt bimetallic cyanide complex catalyst, 20 mL of 1,2-epoxy-4-vinylcyclohexane monomer, and 20 mL of anhydrous dichloromethane solvent were successively added to a 75 mL high-pressure polymerization reactor under anhydrous and oxygen-free conditions. CO2 gas at 3.0 MPa was introduced into the reactor at room temperature, and the reactor was heated and stirred in a 70 °C oil bath. After the CO2 pressure stabilized, it was introduced to 6.0 MPa and about 20 g of CO2 gas was introduced. The reactor was then heated and stirred in a 70 °C oil bath for 12 h. After the reactor was opened, the product was dissolved and precipitated three times with dichloromethane and methanol and then dried under vacuum to obtain 17.34 g of polycarbonate with a carbonate content of 98.95%.

[0081] (b) "Mercapto-Alkene" Click Reaction: Under anhydrous and oxygen-free conditions, 1.96 g of the polymerized polycarbonate was dissolved in 40 mL of anhydrous tetrahydrofuran solvent. 0.64 g of azobisisobutyronitrile and 17.78 g of mercaptosuccinic acid were added to the reaction flask. The flask was connected to a nitrogen balloon and heated and stirred in a 60°C oil bath for 24 h. After the reaction was completed, the precipitate was dissolved three times with tetrahydrofuran and deionized water, and then dried under vacuum to obtain 3.26 g of the product. The proton NMR spectrum of the product is shown below. Figure 15 As shown.

[0082] (c) Crosslinking reaction: 0.28 g of the click reaction product was dissolved in 2.5 mL of N,N-dimethylformamide. 0.02 g of 4-dimethylaminopyridine was slowly added while stirring. After 30 min, the solution became clear and transparent. 0.03 g of 1,12-dibromododecane was then slowly added while stirring. After reacting at 100 °C for 1 h, the solution became gel-like. The gel was cut into small pieces and soaked overnight in 15 mL of 0.15 mol / L sodium bicarbonate solution, followed by freeze-drying to obtain a CO2-based superabsorbent material. Its water absorption ratio was 129.86 g / g. The infrared spectrum of the superabsorbent material is shown below. Figure 16 As shown.

[0083] Example 7

[0084] (a) Polymerization reaction: 11.5 mg of a bifunctional [(1R,2R)-SalenCo(III)(DNP)2] (DNP = 2,4-dinitrophenol) catalyst with a quaternary ammonium salt on the ligand framework and 8.0 mL of 2-vinyl ethylene oxide monomer were added sequentially to a 25 mL high-pressure polymerization reactor under anhydrous and oxygen-free conditions. CO2 gas at 33 bar was introduced into the reactor at room temperature. After the pressure stabilized, the reactor was heated and stirred in a 25 °C water bath for 72 h. After opening the reactor, the product was dissolved and precipitated three times using a mixture of 10 mL dichloromethane / methanol (5 / 1, v / v) containing 0.5% hydrochloric acid solution and methanol, followed by vacuum drying to obtain 0.94 g of polycarbonate with a 100% carbonate content. The proton NMR spectrum of the product is shown below. Figure 17 As shown.

[0085] (b) "Mercapto-Alkene" Click Reaction: Under anhydrous and oxygen-free conditions, 0.50 g of the polymerized polycarbonate was dissolved in 25 mL of anhydrous tetrahydrofuran solvent. 0.27 g of azobisisobutyronitrile (AIBN) and 13 mL of mercaptoethanol were added to the reaction flask. The flask was connected to a nitrogen balloon and placed in a 70°C oil bath with stirring for 24 h. After the reaction was complete, the precipitate was dissolved three times with tetrahydrofuran and diethyl ether, and then dried under vacuum to obtain 0.80 g of the product. The proton NMR spectrum of the product is shown below. Figure 18 As shown.

[0086] (c) Crosslinking reaction: Under an argon atmosphere, 0.5 g of the click reaction product was mixed with 0.24 g of citric acid and dissolved in 2.5 mL of anhydrous tetrahydrofuran. The mixture was reacted at 80 °C for 24 h to form a gel. The gel was cut into small pieces and soaked in 15 mL of 0.15 mol / L sodium bicarbonate solution overnight, followed by freeze-drying to obtain a CO2-based superabsorbent material. Its water absorption ratio was 60.23 g / g. The infrared spectrum of the superabsorbent material is shown below. Figure 19 As shown.

[0087] Example 8

[0088] (a) 5 mg of zinc-cobalt bimetallic cyanide complex catalyst, 20 mL of 1,2-epoxy-4-vinylcyclohexane monomer, and 20 mL of anhydrous dichloromethane solvent were successively added to a 75 mL high-pressure polymerization reactor under anhydrous and oxygen-free conditions. CO2 gas at 3.0 MPa was introduced into the reactor at room temperature, and the reactor was heated and stirred in a 70 °C oil bath. After the CO2 pressure stabilized, it was introduced to 6.0 MPa and about 20 g of CO2 gas. The reactor was then heated and stirred in a 70 °C oil bath for 12 h. After the reactor was opened, the product was dissolved and precipitated three times with dichloromethane and methanol and then dried under vacuum to obtain 16.26 g of polycarbonate with a carbonate content of 96.95%.

[0089] (b) "Mercapto-olefin" click reaction: Under anhydrous and oxygen-free conditions, 1.96 g of the polymerized polycarbonate was dissolved in 40 mL of anhydrous tetrahydrofuran solvent. 0.64 g of azobisisobutyronitrile and 17.78 g of mercaptosuccinic acid were added to the reaction flask. The reaction flask was connected to a nitrogen balloon and heated and stirred in an oil bath at 60 °C for 24 h. After the reaction was completed, the precipitate was dissolved three times with tetrahydrofuran and deionized water and then dried under vacuum to obtain 3.26 g of product.

[0090] (c) Crosslinking reaction: Take 0.50 g of the click reaction product and dissolve it in 3.0 mL of N,N-dimethylformamide. Slowly add 0.04 g of 4-dimethylaminopyridine while stirring. After 30 min, the solution becomes clear and transparent. Dissolve 0.19 g of polyethylene glycol diethylene oxide methyl ether in 1.5 mL of N,N-dimethylformamide and slowly add it to the reaction flask while stirring. Then add 0.18 g of iron oxide particles to prepare magnetic SAP. After reacting at 100℃ for 1 h, it becomes gel-like. Cut the gel into small pieces and soak them in 15 mL of 0.15 mol / L sodium bicarbonate solution overnight. After freeze-drying, obtain CO2-based superabsorbent material. Its water absorption ratio is 146.98 g / g. The infrared spectrum of the superabsorbent material is shown below. Figure 20 As shown.

[0091] The CO2-based superabsorbent material prepared above can maintain the same state for a long time after absorbing water, and after being sealed and stored, the total mass of the absorbent material and the water adsorbed therein does not change much, indicating that the prepared CO2-based superabsorbent material has high stability after absorbing water.

[0092] Repeated water absorption performance test:

[0093] The CO2-based superabsorbent material prepared in the above embodiments was subjected to five cycles of water absorption testing. The results are shown in Table 1.

[0094] Table 1. Water absorption ratio after five cycles

[0095]

[0096]

[0097] As can be seen from Table 1, after five repeated uses, the water absorption ratio of the above CO2-based superabsorbent material does not decrease significantly, indicating that the material has excellent repeated water absorption performance.

[0098] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a carbon dioxide-based superabsorbent material, characterized in that, Includes the following steps: S1) Polycarbonate is prepared by ring-opening copolymerization of epoxy monomers with double bonds and CO2. S2) Hydrophilic groups are introduced into the above polycarbonate groups using the "thiol-ene" click reaction; S3) Using a nucleophilic substitution reaction, the polycarbonate with introduced hydrophilic groups is cross-linked to obtain a gel; S4) The above gel is directly freeze-dried, or the above gel is neutralized into salt in an alkaline solution and then freeze-dried to obtain a carbon dioxide-based superabsorbent material.

2. The method for preparing the carbon dioxide-based superabsorbent material according to claim 1, characterized in that, The epoxy monomer with double bonds is selected from one or more of allyl glycidyl ether, allyl glycidyl carbonate, 1,2-epoxy-4-cyclohexene, 1,2-epoxy-3-cyclohexene, 1,2-epoxy-4-vinylcyclohexane, limonene oxide, and 2-vinyl ethylene oxide.

3. The method for preparing the carbon dioxide-based superabsorbent material according to claim 1, characterized in that, The reagent structure for performing the "thiol-ene" click reaction contains a thiol group, as well as one or more of the following groups: amino, hydroxyl, carboxyl, and sulfonic acid groups.

4. The method for preparing the carbon dioxide-based superabsorbent material according to claim 3, characterized in that, The reagents that carry out the "thiol-ene" click reaction have any of the following structures: HS-R1-COOH, HS-R2-OH, HS-R3-NH2, HS-R4-SO3H, HS-R4-SO3Na; Wherein, R1 is selected from substituted or unsubstituted C1~C5 alkyl groups; the substituents of the C1~C5 alkyl groups are selected from amino groups; R2, R3, and R4 are independently selected from C1 to C5 alkyl groups.

5. The method for preparing the carbon dioxide-based superabsorbent material according to claim 4, characterized in that, The reagents used to perform the "thiol-ene" click reaction are selected from one or more of the following: mercaptoacetic acid, mercaptopropionic acid, mercaptosuccinic acid, mercaptoethanol, mercaptopropanol, mercaptoethylamine, mercaptopropylamine, sodium 3-mercapto-1-propanesulfonate, 2-mercaptoethanesulfonic acid, and cysteine.

6. The method for preparing the carbon dioxide-based superabsorbent material according to claim 1, characterized in that, The reagent used for the nucleophilic substitution reaction is selected from one or more of the following: epoxy resin, 1,6-dibromohexane, 1,12-dibromododecane, 1,2-ethylenediamine, 1,6-hexanediamine, succinic acid, glutaric acid, tris(2-aminoethyl)amine, ethylene glycol bis(3-aminopropyl) ether, and citric acid.

7. The method for preparing the carbon dioxide-based superabsorbent material according to claim 1, characterized in that, The reagents for carrying out nucleophilic substitution reactions are selected from one or more of polyethylene glycol diglycidyl ether and poly(propylene glycol) diglycidyl ether.

8. The method for preparing the carbon dioxide-based superabsorbent material according to claim 1, characterized in that, The ring-opening copolymerization reaction is carried out in the presence of a catalyst; The catalyst is selected from one or more of the following: tetrabromomonoporphyrin aluminum catalyst, zinc cobalt bimetallic cyanide complex catalyst, β-diimine zinc catalyst, salon cobalt / bis(triphenylphosphino)dinitrophenol ammonium catalyst, and bifunctional salon Co catalyst; The condensing agent for the crosslinking reaction is selected from 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxythiosuccinimide.

9. The method for preparing the carbon dioxide-based superabsorbent material according to claim 1, characterized in that, In step S3), magnetic nanoparticles are also added to obtain a magnetic carbon dioxide-based superabsorbent material.

10. A carbon dioxide-based superabsorbent material prepared by the preparation method according to any one of claims 1 to 9.

Images