A covalent organic framework cellulose gel solid phase extraction material, and a preparation method and application thereof
Patent Information
- Application Number
- CN202611105040.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-07-24
- Publication Date
- 2026-08-21
AI Technical Summary
然而，纯COFs材料通常以粉末形式存在，存在以下缺陷：一是难以直接装填柱体，易发生自堆积导致传质受阻；二是机械强度低，在水相环境中易发生溶胀甚至结构坍塌，导致循环使用寿命短；三是合成过程通常涉及有机试剂，环境友好性较差
[0024]本发明针对多菌灵等农药残留检测中样品前处理的需求，提供sp2-COF@CA复合固相萃取材料，有益效果如下：以纤维素气凝胶为三维骨架原位合成烯键连接sp²-COFs，无需复杂后处理，结构稳定不易脱落；材料由C、H、O、N等轻元素构成，绿色可再生、生物相容性好，属环境友好型；结合纤维素大孔与sp²-COFs微孔形成多级孔结构，可排除大分子杂质干扰，选择性吸附多菌灵等小分子目标物；比表面积达372 m²/g，吸附位点充分暴露，传质效率高；热稳定性良好，满足富集分离工作条件；用于固相萃取柱可重复使用，适应不同盐离子浓度及pH环境，有效提升检测灵敏度与准确度。
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Figure CN122605503A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of solid-phase extraction material preparation technology, specifically relating to a solid-phase extraction material of covalent organic framework cellulose gel, its preparation method and application. Background Technology
[0002] Carbendazim, a benzimidazole systemic fungicide, is widely used in crop cultivation to control fungal diseases due to its broad spectrum of activity, long-lasting effect, and flexible application methods. However, due to long-term and frequent use, carbendazim residues are frequently detected in soil, water bodies, and various agricultural products such as fruits, vegetables, and grains. This substance has certain endocrine-disrupting toxicity, and long-term intake poses a potential risk to human health. It may also disrupt the balance of soil microbial communities and threaten ecological security. Therefore, establishing a sensitive and reliable method for detecting carbendazim residues is of great significance for ensuring food safety and environmental monitoring.
[0003] In actual detection processes, carbendazim often exists at trace levels in environmental and biological samples, and the complex composition of the sample matrix (such as pigments, proteins, lipids, etc.) severely interferes with the accuracy and sensitivity of instrument analysis. Therefore, efficient sample pretreatment techniques are crucial for successful detection. Solid phase extraction (SPE) technology, with its advantages of simple operation, high enrichment factor, good purification effect, and effective reduction of matrix effects, has become one of the most commonly used pretreatment methods for pesticide residue analysis. Among them, the solid phase extraction material, as the core consumable, directly determines the pretreatment effect based on its adsorption capacity, selectivity, and stability.
[0004] Existing commercial solid-phase extraction packing materials (such as C18, silica gel matrix packing materials, neutral alumina, etc.) generally suffer from limited specific surface area, poor specific adsorption capacity, and large amounts of organic solvents, making it difficult to meet the enrichment requirements of ultra-trace targets in complex matrices. In recent years, covalent organic frameworks (COFs) have shown great application potential in the field of adsorption separation due to their high specific surface area, regular pore structure, and ability to be functionalized. However, pure COFs materials are usually in powder form, which has the following drawbacks: first, they are difficult to pack directly into columns, and are prone to self-stacking, leading to impaired mass transfer; second, they have low mechanical strength and are prone to swelling or even structural collapse in aqueous environments, resulting in short cycle life; and third, the synthesis process usually involves organic reagents, which is not environmentally friendly.
[0005] In addition, although some studies have attempted to load COFs onto carriers such as cellulose to improve moldability, traditional loading methods are mostly physical mixing or weak interaction bonding, which can easily lead to COFs falling off during use. Furthermore, cellulose carriers have poor compatibility with COF synthesis conditions (such as strongly alkaline environments), making it difficult to achieve in-situ growth. The process is complex and the bonding strength is insufficient.
[0006] Therefore, there is an urgent need to develop a new type of solid-phase extraction material that combines high specific surface area, excellent structural stability, good aqueous dispersibility, and environmental friendliness to solve the problems of low adsorption efficiency, short service life, and cumbersome operation of existing materials in the detection of pesticide residues such as carbendazim. Summary of the Invention
[0007] In order to solve the above-mentioned technical problems in the prior art, the purpose of this invention is to provide a solid-phase extraction material of covalent organic framework cellulose gel, its preparation method and application.
[0008] The technical solution is as follows:
[0009] A solid-phase extraction material based on a covalent organic framework cellulose gel, comprising a three-dimensional macroporous framework of cellulose aerogel, with olefin-linked sps grown in situ on the surface and inside of the framework. 2 Type covalent organic framework, forming a hierarchical porous structure, sp 2 The covalent organic framework is constructed by the condensation of 2,4,6-trimethyl-1,3,5-triazine (TATM) and benzoxaldehyde (DFB) through strong base catalysis, with carbon-carbon double bonds connecting them.
[0010] A method for preparing a solid-phase extraction material of a covalent organic framework cellulose gel includes the following steps:
[0011] 1) Add 2,4,6-trimethyl-1,3,5-triazine, phenylenedialdehyde and potassium hydroxide to a solvent, and sonicate until completely dissolved to obtain a reaction solution;
[0012] 2) Add absorbent cotton to the reaction solution in step 1), ensuring the liquid level covers the cotton, and sonicate to ensure the cotton is in full contact with the reaction solution;
[0013] 3) Transfer to a reaction vessel and react in an oven to simultaneously achieve cellulose aerogelation and sp from the defatted cotton under strongly alkaline conditions. 2 -In-situ growth of COFs;
[0014] 4) After the reaction was complete, the mixture was filtered, washed with methanol until the filtrate was clear, then washed successively with dimethyl sulfoxide and ultrapure water, frozen, and then freeze-dried under vacuum to obtain sp. 2 -COFs@CA composite adsorbent material.
[0015] Further, in step 1), the molar ratio of 2,4,6-trimethyl-1,3,5-triazine, benzoxaldehyde, and potassium hydroxide is 2-3:3-4:6-7, the solvent is a mixture of n-butanol and 1,2-dichlorobenzene with a volume ratio of 6-8:3, and the molar ratio of 2,4,6-trimethyl-1,3,5-triazine to the volume ratio of the solvent is 0.03-0.06 mmol / mL.
[0016] Furthermore, in step 2), the mass ratio of the defatted cotton to the volume ratio of the reaction solution is 16-18 mg / mL.
[0017] Furthermore, in step 3), the reaction is carried out in an oven at 100-120℃ for 36-72 hours, and in step 4), the reaction is carried out under vacuum freeze-drying for 12-24 hours.
[0018] A solid-phase extraction column is prepared by packing a solid-phase extraction material of covalent organic framework cellulose gel into an empty column and adding sieve plates at the top and bottom to obtain the solid-phase extraction column. The mass ratio of the solid-phase extraction material of covalent organic framework cellulose gel to the volume of the empty column is 16-18 mg / mL.
[0019] A solid-phase extraction method for pesticide residues, using the above-mentioned solid-phase extraction column, is carried out according to the following steps:
[0020] 1) Activation: Load the sample with methanol 2-3 times, pressurize and blow dry, then load the sample with pure water 2-3 times, pressurize and blow dry;
[0021] 2) Sample loading: Extract the aqueous phase or matrix sample solution containing the target pesticide through the column at a flow rate of 5 mL / min, with a loading volume of 40-50 mL;
[0022] 3) Elution: Elute with methanol, collect the eluent, concentrate it to 0.5 mL by nitrogen blowing, and test and evaluate the extraction and adsorption effect.
[0023] Furthermore, the target pesticide is selected from one or more of carbendazim (MBC), mebendazole (MBZ), thiophanate-methyl (TM), and albendazole (ABZ), and the solid phase extraction column is suitable for aqueous phase conditions with pH=3-11 and NaCl concentration of 20-100 mM.
[0024] This invention addresses the sample pretreatment requirements in the detection of pesticide residues such as carbendazim, providing a solution using SP. 2The COF@CA composite solid-phase extraction material offers the following advantages: It utilizes a cellulose aerogel as a three-dimensional framework for in-situ synthesis of olefin-linked sp²-COFs, eliminating the need for complex post-processing and ensuring structural stability against detachment; the material is composed of light elements such as C, H, O, and N, making it green, renewable, and biocompatible, thus environmentally friendly; the combination of cellulose macropores and sp²-COF micropores forms a hierarchical porous structure, eliminating interference from large molecular impurities and selectively adsorbing small molecule targets such as carbendazim; its specific surface area reaches 372 m² / g, fully exposing adsorption sites and resulting in high mass transfer efficiency; it exhibits good thermal stability, meeting the requirements for enrichment and separation; it can be reused in solid-phase extraction columns, adapting to different salt ion concentrations and pH environments, effectively improving detection sensitivity and accuracy. Attached Figure Description
[0025] Figure 1 sp prepared for the example 2 -COFs@CA composite adsorbent materials and sp 2 XRD patterns of COFs;
[0026] Figure 2 Infrared spectra of different materials;
[0027] Figure 3 The TG spectra of sp²-COFs@CA, sp²-COFs, and CA are shown.
[0028] Figure 4 BET plots for sp²-COFs@CA and sp²-COFs;
[0029] Figure 5 For CA ( Figure 5 a) and sp²-COFs@CA ( Figure 5 Scanning electron microscope image of b) in the image;
[0030] Figure 6 The results are from the extraction column circulation test.
[0031] Figure 7 The results are for testing the extraction column under different salt ion concentrations.
[0032] Figure 8 The results show the test results of the extraction column under different pH conditions;
[0033] Figure 9 This study compares the extraction performance of different materials for four bactericides. Detailed Implementation
[0034] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.
[0035] Example 1
[0036] Preparation of sp 2 -COFs@CA composite adsorbent material
[0037] 1) Add 2,4,6-trimethyl-1,3,5-triazine (0.5 mmol, 61 mg), benzoxaldehyde (0.75 mmol, 100 mg), and potassium hydroxide (84 mg) to a solvent (10 ml, n-butanol: 1,2-chlorobenzene volume ratio of 1:1), sonicate until completely dissolved to obtain the reaction solution;
[0038] 2) Add 161mg of defatted cotton to the reaction solution in step 1), ensuring the liquid level covers the cotton, and sonicate for 5 minutes to ensure the cotton is in full contact with the reaction solution;
[0039] 3) Transfer to a reaction vessel and react in a 120℃ oven for 72 hours. Under strongly alkaline conditions, the cellulose aerogelation and sp... 2 -In-situ growth of COFs;
[0040] 4) After the reaction was complete, the mixture was filtered, washed with methanol until the filtrate was clear, then washed three times with dimethyl sulfoxide and three times with ultrapure water, frozen, and then freeze-dried under vacuum for 24 h to obtain sp. 2 -COFs@CA composite adsorbent material.
[0041] sp 2 The reaction equations for -COFs are as follows:
[0042]
[0043] The prepared sp 2 The XRD pattern of the COFs@CA composite adsorbent is shown below. Figure 1 As shown, sp can be found 2 -COFs and sp 2 -COFs@CA exhibit crystalline structures within the 2-10nm wavelength range, indicating that sp 2 -COFs were successfully grown in crystalline form on a cellulose substrate.
[0044] sp 2 -COFs are obtained via the Knoevenagel reaction, using olefinic bonds as connecting bonds to provide excellent stability for the framework structure.
[0045] Synthesis conditions at sp 2 By removing the addition of fibers during the synthesis of -COFs@CA while keeping other operating conditions unchanged, pure sp can be obtained. 2 -COFs materials.
[0046] like Figure 2 As shown, because benzoxaldehyde (DFB) contains an aldehyde group, its concentration at 1700 cm⁻¹ -1 Characteristic peaks caused by stretching vibrations will be generated nearby, but in sp 2 -COFs and sp 2 In -COFs@CA, this peak no longer appears. Meanwhile, at 980 cm⁻¹... -1 and 1630 cm -1 The presence of a characteristic peak belonging to an olefin (-C=C-) indicates that during the material synthesis process, the aldehyde group reacts with the methyl group to form an olefin bond, causing the characteristic peak of the aldehyde group to disappear, while the characteristic peak of a carbon-carbon double bond is formed, further confirming the successful synthesis of the target material.
[0047] like Figure 3 As shown, sp 2 The TG spectrum of -COFs@CA. The graph shows that pure sp... 2 -COFs begin to decompose at approximately 400℃, resulting in a decrease in weight. Meanwhile, sp... 2 The -COFs@CA composite material decomposes at around 300℃. The above results indicate that the prepared composite material has excellent thermal stability and can meet the working conditions required for sample enrichment and separation.
[0048] The permanent porosity of sp²-COFs and sp²-COFs@CA was studied by nitrogen adsorption measurement at 77 K. Figure 4 As shown, both materials exhibit rapid increases in the lower pressure range, which can be attributed to type I adsorption isotherms, indicating their microporous properties. Pure sp 2 -COFs have a specific surface area of 1137 m² / g, while sp 2 The specific surface area of -COFs@CA is 372 m² / g. The above results indicate that the prepared material has high specific surface area, which is beneficial to the full exposure of adsorption sites and the efficient adsorption of target substances.
[0049] The material was characterized using scanning electron microscopy, from Figure 5 As can be seen, the cellulose aerogel CA (obtained by removing the two functional monomers required for sp²-COFs in the sp²-COFs@CA synthesis process, while keeping other processes unchanged) has a relatively smooth surface (e.g. Figure 5 As shown in (a)), the surface of the sp²-COFs material becomes rough after in-situ growth (as shown in (a)). Figure 5(as shown in (b)). The above results indicate that the sp²-COFs material is uniformly coated on the cellulose surface. This hierarchical porous structure, composed of a macroporous network of cellulose and a microporous structure of COF loaded on it, can effectively improve the utilization rate of the pores and enhance the adsorption effect on the target analyte.
[0050] Example 2
[0051] sp 2 Application of COFs@CA composite adsorbent materials in solid extraction
[0052] Preparation of analyte standard solutions: Prepare 10 mL of a mixture containing four analytes: carbendazim, mebendazole, thiophanate-methyl, and albendazole as the stock solution (mixed standard stock solution) for subsequent experiments. The concentration of each analyte is 10 mg / L. The analytical solutions of different concentrations required for subsequent experiments are obtained by stepwise dilution from this mixture.
[0053] Assembly of solid phase extraction column:
[0054] Weigh 15 mg of the sp prepared in Example 1 2 - The COFs@CA composite adsorbent material is loaded into a 3 mL solid-phase extraction column pre-loaded with a lower sieve plate, and then the upper sieve plate is added to complete the assembly of the solid-phase extraction column.
[0055] Using the solid-phase extraction column described above, extraction and adsorption were performed according to the following steps:
[0056] 1) Activation: Load the sample with 2 mL of methanol 3 times, pressurize and blow dry, then replace with 2 mL of pure water 3 times, pressurize and blow dry to complete the activation of the extraction column and put it into working state;
[0057] 2) Sample loading: Extract the aqueous phase containing the target pesticide (50 ppb mixed standard solution) through the column at a flow rate of 5 mL / min, and the sample loading volume is 40 mL;
[0058] 3) Elution: Elute with 1.5 mL of methanol, collect the eluent, concentrate it to 0.5 mL by nitrogen blowing, and analyze and quantify it using high performance liquid chromatography.
[0059] Investigating the effect of repeated use on the adsorption performance of the material: the three steps of activation, loading, and elution were repeated to explore the maximum number of times the extraction column could be used. The results are as follows: Figure 6 As shown, after 15 repeated loading and elution, the recovery rate of the extraction column (measured concentration / actual spiked concentration × 100) decreased by about 20%, but still remained above 80%, indicating that it has good reusability.
[0060] The effect of salt ion concentration was investigated: Sodium chloride aqueous solutions with concentrations of 20 mM, 40 mM, 60 mM, 80 mM, and 100 mM were prepared, with 200 mL prepared for each concentration. Then, 1 mL of a mixed standard stock solution was added to each solution to prepare mixed standard solutions containing different salt ion concentrations. These solutions were then loaded with the solutions, eluted, concentrated under nitrogen, and analyzed. The study investigated whether the performance of the extraction column was affected by different salt ion concentrations. Results are as follows: Figure 7 As shown, at low salt ion concentrations, salt ions can improve the overall performance of the material; at high salt ion concentrations, the material recovery rate remains stable at around 70%, maintaining a highly efficient and stable working state.
[0061] The effect of solution pH was investigated: 200 mL of aqueous solutions with pH values of 3, 5, 7, 9, and 11 were prepared using 0.1 M hydrochloric acid and NaOH, respectively. Then, 1 mL of the mixed standard stock solution was added to each of the five solutions and mixed thoroughly to obtain mixed standard solutions under different pH conditions. The sample loading, elution, and nitrogen blowing concentration were repeated three times for each pH value, and the detection steps were performed. The performance of the material under different pH conditions was investigated. The results are as follows: Figure 8 As shown, the material properties are relatively stable, with a recovery rate maintained at over 70% within a wide pH range of 3-11.
[0062] Therefore, the prepared sp 2 -COFs@CA composite adsorbents not only have good reusability, but are also less affected by salt ion concentration and pH, and can maintain stable and efficient performance in various extreme environments.
[0063] Example 3
[0064] Under the same experimental conditions, individual cellulose aerogels, sp²-COFs, and sp²-COFs were prepared. 2 -COFs@CA composite adsorbent material (all materials were obtained using the preparation method described in Example 1). Sample loading and elution were performed using a 40 mL sample volume and an analyte concentration of 50 ppb (operating conditions were the same as in Example 2). Figure 9 It can be seen that the extraction efficiency of sp²-COFs@CA for carbendazim mainly comes from the sp²-COFs fraction, while the extraction efficiency of cellulose aerogel itself is relatively poor. Furthermore, the overall performance of sp²-COFs@CA is superior to that of sp²-COFs. This indicates that cellulose aerogel and sp²-COFs@CA have similar extraction efficiency. 2 The combination of sp²-COFs materials fully leverages the synergistic effect, namely, the combination of the three-dimensional network and macroporous structure of cellulose aerogel with the two-dimensional structure and discrete microporous structure of sp²-COFs, thereby improving the overall performance of the composite material.
Claims
1. A solid-phase extraction material for covalent organic framework cellulose gel, characterized in that, It uses cellulose aerogel as a three-dimensional macroporous framework, with olefin-linked SPs grown in situ on the surface and inside the framework. 2 Type covalent organic framework, forming a hierarchical porous structure, sp 2 The covalent organic framework is constructed by the condensation of 2,4,6-trimethyl-1,3,5-triazine and benzoxaldehyde through strong base catalysis, with carbon-carbon double bonds connecting them.
2. A method for preparing a solid-phase extraction material of a covalent organic framework cellulose gel as described in claim 1, characterized in that, Includes the following steps: 1) Add 2,4,6-trimethyl-1,3,5-triazine, phenylenedialdehyde and potassium hydroxide to a solvent, and sonicate until completely dissolved to obtain a reaction solution; 2) Add the defatted cotton to the reaction solution in step 1), ensuring the liquid level covers the cotton, and sonicate to ensure the cotton is in full contact with the reaction solution; 3) Transfer to a reaction vessel and react in an oven to simultaneously achieve cellulose aerogelation and sp from the defatted cotton under strongly alkaline conditions. 2 -In-situ growth of COFs; 4) After the reaction was complete, the mixture was filtered, washed with methanol until the filtrate was clear, then washed successively with dimethyl sulfoxide and ultrapure water, frozen, and then freeze-dried under vacuum to obtain sp. 2 -COFs@CA composite adsorbent material.
3. The preparation method according to claim 2, characterized in that, In step 1), the molar ratio of 2,4,6-trimethyl-1,3,5-triazine, benzoxaldehyde, and potassium hydroxide is 2-3:3-4:6-7. The solvent is a mixture of n-butanol and 1,2-dichlorobenzene, with a volume ratio of 6-8:
3. The molar ratio of 2,4,6-trimethyl-1,3,5-triazine to the volume ratio of the solvent is 0.03-0.06 mmol / mL.
4. The preparation method according to claim 3, characterized in that, In step 2), the mass ratio of the degreased cotton to the volume of the reaction solution is 16-18 mg / mL.
5. The preparation method according to claim 3, characterized in that, In step 3), the reaction is carried out in an oven at 100-120 ℃ for 36-72 h, and in step 4), the reaction is carried out under vacuum freeze drying for 12-24 h.
6. A solid-phase extraction column, characterized in that, The solid-phase extraction material of the covalent organic framework cellulose gel described in claim 1 is packed into an empty column, and sieve plates are added above and below to obtain a solid-phase extraction column. The mass ratio of the solid-phase extraction material of the covalent organic framework cellulose gel to the volume of the empty column is 16-18 mg / mL.
7. A solid-phase extraction method for pesticide residues, characterized in that, Using the solid-phase extraction column as described in claim 6, the following steps are performed: 1) Activation: Load the sample with methanol 2-3 times, pressurize and blow dry, then load the sample with pure water 2-3 times, pressurize and blow dry; 2) Sample loading: Extract the aqueous phase or matrix sample solution containing the target pesticide through the column at a flow rate of 5 mL / min, with a loading volume of 40-50 mL; 3) Elution: Elute with methanol, collect the eluent, concentrate it to 0.5 mL by nitrogen blowing, and test and evaluate the extraction and adsorption effect.
8. The solid-phase extraction method for pesticide residues as described in claim 7, characterized in that, The target pesticide is selected from one or more of carbendazim, mebendazole, thiophanate-methyl, and albendazole. The solid phase extraction column is suitable for aqueous phase conditions with pH 3-11 and NaCl concentration of 20-100 mM.