Preparation method and application of starch-based ionic porous polymer

Abstract

This invention discloses a method for preparing a starch-based ionic porous polymer (H-ST-LA-IL) and its application. The method first modifies starch with lactic acid under the action of a catalyst to obtain lactic acid-starch. Then, the lactic acid-starch is reacted with an ionic liquid and lactic acid free radicals under the action of an initiator to obtain ionic liquid-functionalized starch. Finally, under a N2 atmosphere, the ionic liquid-functionalized starch, a crosslinking agent, and 1,2-dichloroethane are mixed uniformly, a catalyst is added, and the mixture is heated to react. The mixture is then filtered, Soxhlet extracted, and dried to obtain H-ST-LA-IL. This invention utilizes the chemical bonding of the ionic liquid to the starch molecular chain, acting as a crosslinking reaction site to generate strong chemical interactions with the crosslinking agent molecules, thereby increasing the crosslinking strength of the crosslinking agent on the starch molecular chain and constructing a high specific surface area starch-based ionic porous material. The basic groups of the ionic liquid can construct an alkaline adsorption microenvironment within the pores of H-ST-LA-IL, thus achieving efficient capture of aldehyde VOCs.

Description

Technical Field

[0001] This invention belongs to the field of novel functional materials, specifically relating to a method for preparing a starch-based ionic porous polymer that adsorbs formaldehyde. Background Technology

[0002] Formaldehyde (HCHO) is one of the major volatile organic compounds (VOCs), widely used in materials used in preservatives, textiles, wood processing, and coatings, thus being released into the air. Long-term exposure to formaldehyde, even at low concentrations (<0.1 mg / m³), can lead to serious health problems. 3 Formaldehyde can also lead to nasal tumors, nasopharyngeal carcinoma, and skin irritation. Therefore, effectively removing formaldehyde under atmospheric conditions to improve air quality in enclosed spaces such as bedrooms, offices, and cars is of crucial significance and importance.

[0003] Adsorption is considered a particularly suitable method for formaldehyde treatment due to its high removal rate, cost-effectiveness, and low energy consumption. Currently, the widely used adsorbents for aldehyde VOCs in industry are mainly porous materials with high specific surface areas, such as activated carbon and molecular sieves. However, these adsorbents become "VOCs waste adsorbents" after a certain period of use, and even after VOCs are removed, they are still clearly identified as hazardous waste. If LOE-degradable porous materials could be designed and prepared for the capture of aldehyde VOCs, they could be rendered harmless through full microbial degradation after adsorption, thus avoiding secondary hazardous waste pollution generated by existing inorganic porous materials and possessing certain ecological and economic value.

[0004] Among numerous biodegradable materials, natural starch is the second largest renewable natural biomass resource on Earth after cellulose, boasting advantages such as abundant supply, low price, and environmental friendliness, and has attracted widespread attention from researchers in recent years. Research reports indicate that starch-based polymers (such as starch-based plastics) can be completely and rapidly degraded by microorganisms in nature, and the final degradation products can be recycled through plant photosynthesis without causing any environmental pollution. Using adsorbents made from such materials to adsorb VOCs could solve the problem of the difficult degradation of waste adsorbents. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a green, high specific surface area, and highly efficient method for preparing a starch-based ionic porous polymer for formaldehyde adsorption. The method utilizes an ionic liquid chemically bonded to the starch molecular chain, acting as a crosslinking reaction site to generate strong chemical interactions with the crosslinking agent molecules, thereby increasing the crosslinking strength of the crosslinking agent on the starch molecular chain and constructing a high specific surface area starch-based ionic porous material. Simultaneously, the basic groups of the ionic liquid can construct an alkaline adsorption microenvironment within the pores of the starch-based ionic porous polymer, thus achieving selective capture of aldehyde VOCs.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A method for preparing a starch-based ionic porous polymer and its application, the method comprising the following steps:

[0008] (1) Preparation of lactic acid-starch: starch is gelatinized at a certain temperature, and then lactic acid and zinc acetate catalyst are added to continue the reaction for 10-12 hours. After the reaction is completed and cooled, ethanol is added to precipitate a white solid. After filtration, ethanol Soxhlet extraction and freeze drying, lactic acid-starch is obtained.

[0009] (2) Preparation of ionic liquid functionalized starch: Under N2 atmosphere protection, the lactic acid-starch obtained in (1), ionic liquid, and initiator azobisisobutyronitrile were dispersed in an aqueous solution and stirred for 20-24 h. After the reaction was completed and cooled, ethanol was added to precipitate a white solid. After filtration and freeze drying, ionic liquid functionalized starch was obtained.

[0010] (3) Preparation of starch-based ionic porous polymer: Under N2 atmosphere protection, the ionic liquid functionalized starch obtained in (2) and the crosslinking agent were added to 1,2-dichloroethane, and then anhydrous FeCl3 catalyst was added. After stirring at 40-45℃ for 2-3h, the temperature was raised to 80-85℃ and the reaction continued for 16-20h. After the reaction was completed and cooled, the starch-based ionic porous polymer was obtained by filtration, methanol Soxhlet extraction and vacuum drying.

[0011] As a further preferred embodiment of this technical solution, the starch in step (1) is tapioca starch, sweet potato starch or corn starch.

[0012] As a further preferred embodiment of this technical solution, the mass ratio of starch, lactic acid and zinc acetate catalyst in step (1) is 1:0.2-3:0.02-0.1.

[0013] As a further preferred embodiment of this technical solution, in step (1), the starch is first gelatinized at 70-85℃ for 30-60 minutes.

[0014] As a further preferred embodiment of this technical solution, the ionic liquid in step (1) is any one of 1-vinyl-3-butylimidazolium bromide [C4VIm][Br], 1-vinyl-3-butylimidazolium tetrafluoroborate [C4VIm][BF4], 1-vinyl-3-butylimidazolium hexafluorophosphate [C4VIm][PF6], and 1-vinyl-3-butylimidazolium acetate [C4VIm][OAc].

[0015] As a further preferred embodiment of this technical solution, the mass ratio of lactic acid-starch, ionic liquid and initiator azobisisobutyronitrile in step (2) is 1:1-5:0.02-0.1.

[0016] As a further preferred embodiment of this technical solution, the crosslinking agent in step (3) is biphenyl dichlorobenzyl or p-dichlorobenzyl.

[0017] As a further preferred embodiment of this technical solution, the mass ratio of ionic liquid functionalized starch, crosslinking agent and anhydrous FeCl3 catalyst in step (3) is 1:0.5-3:0.2-2.

[0018] As a further preferred embodiment of this technical solution, the mass-to-volume ratio of ionic liquid functionalized starch to 1,2-dichloroethane in step (3) is 1:50-150.

[0019] The application of the starch-based ionic porous polymer prepared by the method of the present invention in aldehyde VOCs adsorbents.

[0020] The starch-based ionic porous polymer of the present invention is applied to the field of adsorption and separation of aldehyde VOCs, and achieves high-efficiency adsorption of formaldehyde.

[0021] This invention first modifies starch with lactic acid through esterification under the action of zinc acetate catalyst to obtain lactic acid-starch (ST-LA); then, using lactic acid as a linker molecule, an ionic liquid containing double bonds reacts highly with lactic acid free radicals under the action of an initiator, enabling the ionic liquid to covalently bond to the starch molecular chain, obtaining ionic liquid functionalized starch (ST-LA-IL); finally, under N2 atmosphere protection, ST-LA-IL, crosslinking agent, and 1,2-dichloroethane are mixed evenly, and anhydrous FeCl3 catalyst is added to induce Friedel-Crafts alkylation reaction. The reaction is carried out under heating conditions to obtain a brown solid, which is then filtered, Soxhlet extracted, and vacuum dried to obtain a starch-based ionic porous polymer (H-ST-LA-IL).

[0022] The principle of this invention: Addressing the issue that traditional starch-based porous materials suffer from easily collapsing frameworks and low specific surface areas, failing to meet the practical requirements for gas adsorption and capture, this invention proposes an alkaline ionic liquid immobilization strategy. The ionic liquid functionalizes the starch chains, providing effective crosslinking sites for subsequent crosslinking and forming a high-strength, high-specific-surface-area adsorption network. The ionic liquid is anchored to the starch molecular chains through chemical bonds, utilizing its inherent imidazole groups to generate strong chemical interactions with crosslinking agent molecules, increasing the crosslinking strength of the crosslinking agent on the starch molecular chains, and constructing a high-specific-surface-area starch-based ionic porous polymer. Simultaneously, the binding sites of the alkaline ionic liquid enhance the adsorption performance for formaldehyde.

[0023] Compared with the prior art, the advantages of this invention are:

[0024] 1. This invention utilizes lactic acid grafted starch, which not only effectively breaks the high-density entanglement between starch chains, but also successfully modifies the starch chains with lactic acid active sites, which is beneficial for the grafting of ionic liquids.

[0025] 2. The starch-based ionic porous polymer prepared in this invention is used for formaldehyde adsorption. The material has a stable structure and stable physicochemical properties. It not only solves the problem of easy collapse of the material skeleton, but also facilitates the recovery and recycling of the adsorbent.

[0026] 3. The starch-based ionic porous polymer prepared by this invention enables alkaline ionic liquids to be successfully intercalated into the cross-linked network of the starch-based polymer, which not only increases the specific surface area of ​​the starch-based polymer, but also enhances the adsorption process of formaldehyde.

[0027] 4. This invention utilizes ionic liquids as adsorption sites for formaldehyde, constructing a starch-based ionic porous polymer that exhibits excellent formaldehyde adsorption performance. Formaldehyde adsorption test results show that the starch-based ionic porous polymer formed by intercalating starch molecular chains with ionic liquid exhibits excellent adsorption performance for low concentrations of formaldehyde (350 ppm), with an adsorption capacity of approximately 13.5 mg / g. The adsorption capacities of the starch-based nonionic porous polymer and the pure starch-based polymer for formaldehyde are only 6.9 mg / g and 4.5 mg / g, respectively.

[0028] 5. The starch-based ionic porous polymer prepared by this invention is green, environmentally friendly, biodegradable, and low in cost, making it suitable for large-scale industrial production. Attached Figure Description

[0029] Figure 1 Infrared spectra of native cassava starch, lactic acid-cassava starch, ionic liquid-functionalized cassava starch, and starch-based ionic porous polymers prepared in Example 8.

[0030] Figure 2 SEM images of the starch-based nonionic porous polymer (H-ST-g-PS) prepared in Comparative Example 1, the starch-based polymer (H-ST) prepared in Comparative Example 2, and the starch-based ionic porous polymer (H-ST-LA-IL) prepared in Example 8 of this invention.

[0031] Figure 3 The XRD patterns are of the starch-based nonionic porous polymer (H-ST-g-PS) prepared in Comparative Example 1, the starch-based polymer (H-ST) prepared in Comparative Example 2, and the starch-based ionic porous polymer (H-ST-LA-IL) prepared in Example 8 of this invention.

[0032] Figure 4Nitrogen adsorption / desorption isotherms and pore size distribution curves of the starch-based nonionic porous polymer (H-ST-g-PS) prepared in Comparative Example 1, the starch-based polymer (H-ST) prepared in Comparative Example 2, and the starch-based ionic porous polymer (H-ST-LA-IL) prepared in Example 8 of this invention.

[0033] Figure 5 The adsorption kinetics curves of formaldehyde for the starch-based nonionic porous polymer (H-ST-g-PS) prepared in Comparative Example 1, the starch-based polymer (H-ST) prepared in Comparative Example 2, and the starch-based ionic porous polymer (H-ST-LA-IL) prepared in Example 8 of this invention are shown.

[0034] Figure 6 Adsorption rate diagrams of formaldehyde for the starch-based nonionic porous polymer (H-ST-g-PS) prepared in Comparative Example 1, the starch-based polymer (H-ST) prepared in Comparative Example 2, and the starch-based ionic porous polymer (H-ST-LA-IL) prepared in Example 8 of this invention. Detailed Implementation

[0035] The following examples further illustrate the present invention in detail. It should be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below.

[0036] Example 1

[0037] A method for preparing a starch-based ionic porous polymer and its application, comprising the following steps:

[0038] (1) Preparation of lactic acid-cassava starch: 5g of cassava starch was dispersed in 100mL of deionized water and gelatinized at 80℃ for half an hour. Then, 10g of lactic acid and 0.2g of zinc acetate catalyst were added and the reaction continued for 12h. After the reaction was completed and cooled, 200mL of ethanol was added to precipitate a white solid. After filtration, Soxhlet extraction with ethanol for 24h, and freeze drying, lactic acid-cassava starch was obtained.

[0039] (2) Preparation of ionic liquid functionalized cassava starch: Under N2 atmosphere protection, 2g lactic acid-cassava starch, 4g 1-vinyl-3-butylimidazolium bromide and 0.15g initiator azobisisobutyronitrile obtained in (1) were dispersed into 50mL deionized water and heated and stirred for 24h. After the reaction was completed and cooled, 200mL ethanol was added to precipitate a white solid. After filtration and freeze drying, ionic liquid functionalized cassava starch was obtained.

[0040] (3) Preparation of starch-based ionic porous polymer: Under N2 atmosphere protection, 1g of ionic liquid functionalized cassava starch obtained in (2) and 1g of crosslinking agent biphenyl dichlorobenzyl were added to 100mL of 1,2-dichloroethane, and then 2g of catalyst anhydrous FeCl3 were added. After stirring at 45℃ for 2h, the temperature was raised to 80℃ and the reaction continued for 20h. After the reaction was completed and cooled, the starch-based ionic porous polymer (H-ST-LA-IL) was obtained by vacuum filtration, methanol Soxhlet extraction for 24h, and vacuum drying.

[0041] Example 2

[0042] A method for preparing a starch-based ionic porous polymer and its application, comprising the following steps:

[0043] (1) Preparation of lactic acid-cassava starch: 5g of cassava starch was dispersed in 100mL of deionized water and gelatinized at 80℃ for 60min. Then, 10g of lactic acid and 0.2g of zinc acetate catalyst were added and the reaction continued for 10h. After the reaction was completed and cooled, 200mL of ethanol was added to precipitate a white solid. After filtration, Soxhlet extraction with ethanol for 24h, and freeze drying, lactic acid-cassava starch was obtained.

[0044] (2) Preparation of ionic liquid functionalized cassava starch: Under N2 atmosphere protection, 2g lactic acid-cassava starch, 4g 1-vinyl-3-butylimidazolium tetrafluoroborate and 0.15g initiator azobisisobutyrate obtained in (1) were dispersed into 50mL deionized water and heated and stirred for 20h. After the reaction was completed and cooled, 200mL ethanol was added to precipitate a white solid. After filtration and freeze drying, ionic liquid functionalized cassava starch was obtained.

[0045] (3) Preparation of starch-based ionic porous polymer: Under N2 atmosphere protection, 1g of ionic liquid functionalized cassava starch obtained in (2) and 1g of crosslinking agent biphenyl dichlorobenzyl were added to 100mL of 1,2-dichloroethane, and then 2g of catalyst anhydrous FeCl3 were added. After stirring at 40℃ for 3h, the temperature was raised to 85℃ and the reaction continued for 16h. After the reaction was completed and cooled, the starch-based ionic porous polymer (H-ST-LA-IL) was obtained by filtration, methanol Soxhlet extraction for 24h, and vacuum drying.

[0046] Example 3

[0047] A method for preparing a starch-based ionic porous polymer and its application, comprising the following steps:

[0048] (1) Preparation of lactic acid-cassava starch: 5g of cassava starch was dispersed in 100mL of deionized water and gelatinized at 80℃ for half an hour. Then, 10g of lactic acid and 0.2g of zinc acetate catalyst were added and the reaction continued for 12h. After the reaction was completed and cooled, 200mL of ethanol was added to precipitate a white solid. After filtration, Soxhlet extraction with ethanol for 24h, and freeze drying, lactic acid-cassava starch was obtained.

[0049] (2) Preparation of ionic liquid functionalized cassava starch: Under N2 atmosphere protection, 2g lactic acid-cassava starch, 4g 1-vinyl-3-butylimidazolium hexafluorophosphate, and 0.15g initiator azobisisobutyronitrile obtained in (1) were dispersed into 50mL of deionized water and heated and stirred for 24h. After the reaction was completed and cooled, 200mL of ethanol was added to precipitate a white solid. After filtration and freeze-drying, ionic liquid functionalized cassava starch was obtained.

[0050] (3) Preparation of starch-based ionic porous polymer: Under N2 atmosphere protection, 1g of ionic liquid functionalized cassava starch obtained in (2) and 1g of crosslinking agent biphenyl dichlorobenzyl were added to 100mL of 1,2-dichloroethane, and then 2g of catalyst anhydrous FeCl3 were added. After stirring at 45℃ for 2h, the temperature was raised to 80℃ and the reaction continued for 20h. After the reaction was completed and cooled, the starch-based ionic porous polymer (H-ST-LA-IL) was obtained by vacuum filtration, methanol Soxhlet extraction for 24h, and vacuum drying.

[0051] Example 4

[0052] A method for preparing a starch-based ionic porous polymer and its application, comprising the following steps:

[0053] (1) Preparation of lactic acid-cassava starch: 5g of cassava starch was dispersed in 100mL of deionized water and gelatinized at 80℃ for half an hour. Then, 10g of lactic acid and 0.2g of zinc acetate catalyst were added and the reaction continued for 12h. After the reaction was completed and cooled, 200mL of ethanol was added to precipitate a white solid. After filtration, Soxhlet extraction with ethanol for 24h, and freeze drying, lactic acid-cassava starch was obtained.

[0054] (2) Preparation of ionic liquid functionalized cassava starch: Under N2 atmosphere protection, 2g lactic acid-cassava starch, 4g 1-vinyl-3-butylimidazolium acetate and 0.15g initiator azobisisobutyronitrile obtained in (1) were dispersed into 50mL deionized water and heated and stirred for 24h. After the reaction was completed and cooled, 200mL ethanol was added to precipitate a white solid. After filtration and freeze drying, ionic liquid functionalized cassava starch was obtained.

[0055] (3) Preparation of starch-based ionic porous polymer: Under N2 atmosphere protection, 1g of ionic liquid functionalized cassava starch obtained in (2) and 1g of crosslinking agent biphenyl dichlorobenzyl were added to 100mL of 1,2-dichloroethane, and then 2g of catalyst anhydrous FeCl3 were added. After stirring at 45℃ for 2h, the temperature was raised to 80℃ and the reaction continued for 20h. After the reaction was completed and cooled, the starch-based ionic porous polymer (H-ST-LA-IL) was obtained by vacuum filtration, methanol Soxhlet extraction for 24h, and vacuum drying.

[0056] Example 5

[0057] A method for preparing a starch-based ionic porous polymer and its application, comprising the following steps:

[0058] (1) Preparation of lactic acid-cassava starch: 5g of cassava starch was dispersed in 100mL of deionized water and gelatinized at 85℃ for half an hour. Then, 10g of lactic acid and 0.2g of zinc acetate catalyst were added and the reaction continued for 10h. After the reaction was completed and cooled, 200mL of ethanol was added to precipitate a white solid. After filtration, Soxhlet extraction with ethanol for 24h, and freeze drying, lactic acid-cassava starch was obtained.

[0059] (2) Preparation of ionic liquid functionalized cassava starch: Under N2 atmosphere protection, 2g of lactic acid-cassava starch, 4g of 1-vinyl-3-butylimidazolium bromide, and 0.15g of initiator azobisisobutyronitrile obtained in (1) were added to 50mL of deionized water and heated and stirred for 20h. After the reaction was completed and cooled, 200mL of ethanol was added to precipitate a white solid. After filtration and freeze-drying, ionic liquid functionalized cassava starch was obtained.

[0060] (3) Preparation of starch-based ionic porous polymer: Under N2 atmosphere protection, 1g of ionic liquid functionalized cassava starch obtained in (2) and 1g of crosslinking agent p-dichlorobenzyl were added to 100mL of 1,2-dichloroethane, and then 2g of catalyst anhydrous FeCl3 were added. After stirring at 40℃ for 3h, the temperature was raised to 85℃ and the reaction continued for 16h. After the reaction was completed and cooled, the starch-based ionic porous polymer (H-ST-LA-IL) was obtained by vacuum filtration, methanol Soxhlet extraction for 24h, and vacuum drying.

[0061] Example 6

[0062] A method for preparing a starch-based ionic porous polymer and its application, comprising the following steps:

[0063] (1) Preparation of lactic acid-cassava starch: 5g of cassava starch was dispersed in 100mL of deionized water and gelatinized at 80℃ for half an hour. Then, 10g of lactic acid and 0.2g of zinc acetate catalyst were added and the reaction continued for 12h. After the reaction was completed and cooled, 200mL of ethanol was added to precipitate a white solid. After filtration, Soxhlet extraction with ethanol for 24h, and freeze drying, lactic acid-cassava starch was obtained.

[0064] (2) Preparation of ionic liquid functionalized cassava starch: Under N2 atmosphere protection, 2g lactic acid-cassava starch, 4g 1-vinyl-3-butylimidazolium tetrafluoroborate and 0.15g initiator azobisisobutyronitrile obtained in (1) were dispersed into 50mL deionized water and heated and stirred for 24h. After the reaction was completed and cooled, 200mL ethanol was added to precipitate a white solid. After filtration and freeze drying, ionic liquid functionalized cassava starch was obtained.

[0065] (3) Preparation of starch-based ionic porous polymer: Under N2 atmosphere protection, 1g of ionic liquid functionalized cassava starch obtained in (2) and 1g of crosslinking agent p-dichlorobenzyl were added to 100mL of 1,2-dichloroethane, and then 2g of catalyst anhydrous FeCl3 were added. After stirring at 45℃ for 2h, the temperature was raised to 80℃ and the reaction continued for 20h. After the reaction was completed and cooled, the starch-based ionic porous polymer (H-ST-LA-IL) was obtained by filtration, methanol Soxhlet extraction for 24h, and vacuum drying.

[0066] Example 7

[0067] A method for preparing a starch-based ionic porous polymer and its application, comprising the following steps:

[0068] (1) Preparation of lactic acid-cassava starch: 5g of cassava starch was dispersed in 100mL of deionized water and gelatinized at 80℃ for half an hour. Then, 10g of lactic acid and 0.2g of zinc acetate catalyst were added and the reaction continued for 12h. After the reaction was completed and cooled, 200mL of ethanol was added to precipitate a white solid. After filtration, Soxhlet extraction with ethanol for 24h, and freeze drying, lactic acid-cassava starch was obtained.

[0069] (2) Preparation of ionic liquid functionalized cassava starch: Under N2 atmosphere protection, 2g lactic acid-cassava starch, 4g 1-vinyl-3-butylimidazolium hexafluorophosphate, and 0.15g initiator azobisisobutyronitrile obtained in (1) were dispersed into 50mL of deionized water and heated and stirred for 24h. After the reaction was completed and cooled, 200mL of ethanol was added to precipitate a white solid. After filtration and freeze-drying, ionic liquid functionalized cassava starch was obtained.

[0070] (3) Preparation of starch-based ionic porous polymer: Under N2 atmosphere protection, 1g of ionic liquid functionalized cassava starch obtained in (2) and 1g of crosslinking agent p-dichlorobenzyl were added to 100mL of 1,2-dichloroethane, and then 2g of catalyst anhydrous FeCl3 were added. After stirring at 45℃ for 2h, the temperature was raised to 80℃ and the reaction continued for 20h. After the reaction was completed and cooled, the starch-based ionic porous polymer (H-ST-LA-IL) was obtained by filtration, methanol Soxhlet extraction for 24h, and vacuum drying.

[0071] Example 8

[0072] A method for preparing a starch-based ionic porous polymer and its application, comprising the following steps:

[0073] (1) Preparation of lactic acid-cassava starch: 5g of cassava starch was dispersed in 100mL of deionized water and gelatinized at 80℃ for half an hour. Then, 10g of lactic acid and 0.2g of zinc acetate catalyst were added and the reaction continued for 12h. After the reaction was completed and cooled, 200mL of ethanol was added to precipitate a white solid. After filtration, Soxhlet extraction with ethanol for 24h, and freeze drying, lactic acid-cassava starch was obtained.

[0074] (2) Preparation of ionic liquid functionalized cassava starch: Under N2 atmosphere protection, 2g lactic acid-cassava starch, 4g 1-vinyl-3-butylimidazolium acetate and 0.15g initiator azobisisobutyronitrile obtained in (1) were dispersed into 50mL deionized water and heated and stirred for 24h. After the reaction was completed and cooled, 200mL ethanol was added to precipitate a white solid. After filtration and freeze drying, ionic liquid functionalized cassava starch was obtained.

[0075] (3) Preparation of starch-based ionic porous polymer: Under N2 atmosphere protection, 1g of ionic liquid functionalized cassava starch obtained in (2) and 1g of crosslinking agent p-dichlorobenzyl were added to 100mL of 1,2-dichloroethane, and then 2g of catalyst anhydrous FeCl3 were added. After stirring at 45℃ for 2h, the temperature was raised to 80℃ and the reaction continued for 20h. After the reaction was completed and cooled, the starch-based ionic porous polymer (H-ST-LA-IL) was obtained by filtration, methanol Soxhlet extraction for 24h, and vacuum drying.

[0076] Comparative Example 1

[0077] A method for preparing a starch-based nonionic porous polymer includes the following steps:

[0078] (1) Preparation of styrene-functionalized cassava starch (ST-g-PS): 5g of cassava starch was dispersed in 100mL of deionized water and gelatinized at 80℃ for half an hour. Then, 10g of styrene and 0.2g of initiator ammonium persulfate were added and the reaction continued for 6 hours. After the reaction was completed and cooled, 200mL of ethanol was added to precipitate a white solid. After filtration, Soxhlet extraction with a mixed solvent of cyclohexane and acetone (cyclohexane:acetone = 3:1) was performed for 24 hours and then freeze-dried to obtain styrene-cassava starch.

[0079] (2) Preparation of starch-based nonionic porous polymer (H-ST-g-PS): Under N2 atmosphere protection, 1g of styrene-functionalized cassava starch obtained in (1) and 0.5g of crosslinking agent p-dichlorobenzyl were added to 100mL of 1,2-dichloroethane, and then 2g of anhydrous FeCl3 catalyst were added. After stirring at 45℃ for 2h, the temperature was raised to 80℃ and the reaction continued for 20h. After the reaction was completed and cooled, the starch-based nonionic porous polymer (H-ST-g-PS) was obtained by filtration, methanol Soxhlet extraction for 24h, and vacuum drying.

[0080] Comparative Example 2

[0081] Preparation of pure starch-based polymer (H-ST): Under N2 atmosphere protection, 1g of cassava starch and 1g of crosslinking agent p-dichlorobenzyl were added to 100mL of 1,2-dichloroethane, and then 2g of anhydrous FeCl3 catalyst were added. After stirring at 45℃ for 2h, the temperature was raised to 80℃ and the reaction continued for 20h. After the reaction was completed and cooled, the pure starch-based polymer (H-ST) was obtained by filtration, methanol Soxhlet extraction for 24h, and vacuum drying.

[0082] Material performance testing:

[0083] The products prepared according to Comparative Example 1, Comparative Example 2, and some embodiments of the present invention were subjected to structural and performance characterization analysis.

[0084] (I) FT-IR characterization of starch-based ionic porous polymers

[0085] Figure 3 The infrared spectra of native cassava starch (Starch), lactic acid-treated cassava starch (ST-LA), ionic liquid-functionalized cassava starch (ST-LA-IL), and starch-based ionic porous polymer (H-ST-LA-IL) are shown (using an FTS3000 infrared spectroscopy scanner from Bio-Rad, USA). Starch, ST-LA, ST-LA-IL, and H-ST-LA-IL are shown at 3400 cm⁻¹. -1A strong absorption peak with a broad shape is observed at 1732 cm⁻¹, which is formed by hydrogen bonding of the OH peaks in the starch molecule. Compared with the Starch spectrum, the intensity of this absorption peak in ST-LA is weakened, suggesting that the hydroxyl groups in starch are partially substituted. Furthermore, ST-LA shows a strong absorption peak at 1732 cm⁻¹. -1 A sharp and distinct absorption peak appears at 1549 cm⁻¹, which is a characteristic peak of the C=O stretching vibration in the ester group. -1 The peak at 3024 cm⁻¹ represents the characteristic peaks of the C=N and C=C stretching vibrations of the imidazole ring in the ionic liquid of ST-LA-IL. -1 The Ar-H stretching vibration peaks observed indicate that the crosslinking agent has successfully crosslinked dichlorobenzyl.

[0086] (II) Surface morphology of polymers

[0087] The surface morphology of cassava starch (Starch), the starch-based nonionic porous polymer (H-ST-g-PS) prepared in Comparative Example 1, the pure starch-based polymer (H-ST) prepared in Comparative Example 2, and the starch-based ionic porous polymer (H-ST-LA-IL) prepared in Example 8 of this invention were characterized using a Hitachi S-3400N low-power scanning electron microscope. Figure 1 As shown, the surface of cassava starch granules is very smooth, while the surface of H-ST-g-PS prepared in Comparative Example 1 is rough, exhibiting a disordered and chaotic structure. In contrast, the SEM image of Comparative Example 2 clearly shows the presence of starch granules, indicating that the H-ST synthesized according to Comparative Example 2 is a mixture of starch granules and the self-polymer of dichlorobenzyl crosslinking agent, and the starch did not polymerize successfully. This may be because the unmodified starch surface lacks polymerization functional groups, leading to polymerization failure. The H-ST-LA-IL prepared in Example 8 of this invention has a distinct lamellar structure, which can maximize the exposure of formaldehyde adsorption sites and improve formaldehyde adsorption capacity.

[0088] (III) XRD characterization of polymers

[0089] The crystal structures of cassava starch (Starch), the starch-based nonionic porous polymer (H-ST-g-PS) prepared in Comparative Example 1, the pure starch-based polymer (H-ST) prepared in Comparative Example 2, and the starch-based ionic porous polymer (H-ST-LA-IL) prepared in Example 8 of this invention were characterized using a Japanese RIGAKU SMARTLAB3KW powder X-ray diffractometer (PXRD) with CuKα radiation in the range of 2θ = 5-60°. Figure 2 As shown, both H-ST-g-PS and H-ST-LA-IL exhibit characteristic amorphous carbon peaks, while H-ST retains some of the original starch crystal form, indicating that the starch was not successfully polymerized, consistent with the SEM results.

[0090] (iv) Characterization of nitrogen adsorption / desorption isotherms and pore structure parameters of polymer

[0091] The specific surface area and pore structure of the starch-based nonionic porous polymer (H-ST-g-PS) prepared in Comparative Example 1, the pure starch-based polymer (H-ST) prepared in Comparative Example 2, and the starch-based ionic porous polymer (H-ST-LA-IL) prepared in this invention were characterized at 77 K using a Micromeritics ASAP 2460 surface area and porosity analyzer. The characterization results are as follows: Figure 4 As shown in Table 1, Example 8 is the material with the optimal parameters.

[0092] Table 1. Specific surface area and pore structure parameters of polymer materials

[0093]

[0094] Depend on Figure 4 Pore ​​size analysis shows that the pore sizes of H-ST-g-PS, H-ST, and H-ST-LA-IL are all concentrated in... The size of the crosslinking agent matches that of formaldehyde molecules, which is beneficial for formaldehyde adsorption. A comparison between Examples 4 and 8 shows that the H-ST-LA-IL prepared by crosslinking agent p-dichlorobenzyl in Example 8 has a microporous specific surface area ratio as high as 0.78, which is much higher than that of H-ST-LA-IL prepared by crosslinking agent p-dichlorobenzyl in Example 4. This indicates that H-ST-LA-IL prepared by crosslinking agent p-dichlorobenzyl contains a richer microporous structure, which is more conducive to formaldehyde adsorption. Furthermore, compared with H-ST-g-PS prepared in Comparative Example 1 and H-ST prepared in Comparative Example 2, the H-ST-LA-IL prepared in Example 8 of this invention has increased BET specific surface area, microporous specific surface area, and mesoporous specific surface area, and the pore volume of micropores and mesopores is also increased, creating favorable conditions for adsorption.

[0095] (V) Analysis of the adsorption kinetics of formaldehyde by polymers.

[0096] The adsorption kinetics of low-concentration formaldehyde (350 ppm) in the starch-based nonionic porous polymer (H-ST-g-PS) prepared in Comparative Example 1, the pure starch-based polymer (H-ST) prepared in Comparative Example 2, and the starch-based ionic porous polymer (H-ST-LA-IL) prepared in this invention were determined using a Finnish GASERA ONE photoacoustic spectrometer. Figure 5 As shown, the adsorption kinetics of formaldehyde by H-ST-g-PS, H-ST, and H-ST-LA-IL reached equilibrium within 90 min, and exhibited a favorable trend according to the universal diffusion model (R0). 2>0.9). Among them, H-ST-LA-IL has a higher formaldehyde equilibrium adsorption capacity of 13.5 mg / g, while H-ST-g-PS and H-ST have only 6.9 mg / g and 4.5 mg / g, respectively, for formaldehyde.

[0097] Figure 6 The calculated adsorption kinetics show that H-ST-LA-IL has a higher adsorption rate for formaldehyde, which is 3.22 times and 4.33 times that of H-ST-g-PS and H-ST, respectively. This is attributed to the high specific surface area of ​​H-ST-LA-IL and the alkaline ionic liquid adsorption microenvironment.

[0098] The examples provided in this invention are not intended to limit the implementation of the invention. Those skilled in the art will recognize that various variations and modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all possible implementations. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of the claims.

Claims

1. A method for preparing a starch-based ionic porous polymer, characterized in that, The method includes the following steps: (1) Preparation of lactic acid-starch: starch is gelatinized at a certain temperature, and then lactic acid and zinc acetate catalyst are added to continue the reaction for 10-12 h. After the reaction is completed and cooled, ethanol is added to precipitate a white solid. After filtration, extraction and freeze drying, lactic acid-starch is obtained. (2) Preparation of ionic liquid functionalized starch: Under N2 atmosphere protection, the lactic acid-starch obtained in (1), ionic liquid, and initiator azobisisobutyronitrile were dispersed in an aqueous solution and stirred for 20-24 h. After the reaction was completed and cooled, ethanol was added to precipitate a white solid. After filtration and freeze drying, ionic liquid functionalized starch was obtained. The ionic liquid is any one of 1-vinyl-3-butylimidazolium bromide [C4VIm][Br], 1-vinyl-3-butylimidazolium tetrafluoroborate [C4VIm][BF4], 1-vinyl-3-butylimidazolium hexafluorophosphate [C4VIm][PF6], and 1-vinyl-3-butylimidazolium acetate [C4VIm][OAc]. (3) Preparation of starch-based ionic porous polymer: Under N2 atmosphere protection, the ionic liquid functionalized starch and crosslinking agent obtained in (2) were added to 1,2-dichloroethane, and then anhydrous FeCl3 catalyst was added. After stirring at 40-45 ℃ for 2-3 h, the temperature was raised to 80-85 ℃ and the reaction continued for 16-20 h. After the reaction was completed and cooled, the starch-based ionic porous polymer was obtained by filtration, extraction and vacuum drying. The crosslinking agent is biphenyl dichlorobenzyl or p-dichlorobenzyl.

2. The method for preparing starch-based ionic porous polymer according to claim 1, characterized in that: The starch in step (1) is tapioca starch, sweet potato starch or corn starch.

3. The method for preparing the starch-based ionic porous polymer according to claim 1, characterized in that: In step (1), the mass ratio of starch, lactic acid and catalyst zinc acetate is 1:0.2-3:0.02-0.

1.

4. The method for preparing the starch-based ionic porous polymer according to claim 1, characterized in that: In step (1), the starch is first gelatinized at 70-85 ℃ for 30-60 min.

5. The method for preparing the starch-based ionic porous polymer according to claim 1, characterized in that: In step (2), the mass ratio of lactic acid-starch, ionic liquid and initiator azobisisobutyronitrile is 1: 1-5: 0.02-0.

1.

6. The method for preparing the starch-based ionic porous polymer according to claim 1, characterized in that: In step (3), the mass ratio of ionic liquid functionalized starch, crosslinking agent and anhydrous FeCl3 catalyst is 1:0.5-3:0.2-2.

7. The method for preparing the starch-based ionic porous polymer according to claim 1, characterized in that: In step (3), the mass-to-volume ratio of ionic liquid functionalized starch to 1,2-dichloroethane is 1:50-150.

8. The application of the starch-based ionic porous polymer prepared by the method according to any one of claims 1 to 7, characterized in that: Application of starch-based ionic porous polymers in aldehyde VOCs adsorbents.

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