CN114994199B

CN114994199B - Preparation of MOF@COF core-shell composite material and application of MOF@COF core-shell composite material as solid phase extraction adsorbent

Info

Publication number: CN114994199B
Application number: CN202210569863.5A
Authority: CN
Inventors: 梁晓静; 马明财; 郭勇; 王旭生; 王帅
Original assignee: Lanzhou Institute of Chemical Physics LICP of CAS
Current assignee: Lanzhou Institute of Chemical Physics LICP of CAS
Priority date: 2022-05-24
Filing date: 2022-05-24
Publication date: 2023-06-09
Anticipated expiration: 2042-05-24
Also published as: CN114994199A

Abstract

The invention discloses preparation of a MOF@COF core-shell composite material and application of the MOF@COF core-shell composite material as a solid phase extraction adsorbent, and belongs to the technical fields of composite materials and solid phase extraction. Firstly, preparing amino-functionalized MOFs by using a solvothermal synthesis method; secondly, adding the aminated MOFs into a synthesis system of a covalent organic framework material COFs, and constructing a covalent-connection MOF@COF core-shell composite material in situ by utilizing Schiff base reaction between the two components; and finally, using the MOF@COF core-shell composite material as a solid phase extraction adsorbent filler to extract and enrich the flavonoid compounds in the food matrix, and combining an HPLC technology to detect and analyze the enriched flavonoid compounds. The MOF@COF core-shell composite material prepared by the method combines the advantages of original components, has the advantages of large specific surface area, good stability, rich porous structure and the like, has large adsorption capacity and multiple adsorption acting force as an adsorbent, and is suitable for efficient enrichment of trace flavonoid compounds in a complex system.

Description

Preparation of MOF@COF core-shell composite material and application of MOF@COF core-shell composite material as solid phase extraction adsorbent

Technical Field

The invention relates to a preparation method of a MOF@COF core-shell composite material and application thereof in enrichment detection of flavonoid substances in foods, belonging to the technical fields of composite materials and solid phase extraction.

Background

Flavonoid such as quercetin, luteolin and apigenin is a polyphenol compound widely distributed in medicinal plants, vegetables, fruit juice and honey. Research shows that part of flavonoid compounds have the functions of resisting aging, resisting cancer, resisting oxidation, resisting inflammation, resisting bacteria and resisting viruses. However, the concentration of flavonoids in the actual sample is extremely low, and the matrix interference is complex, which is unfavorable for direct analysis. Therefore, there is a need to develop an effective sample pretreatment method to determine flavonoids in complex sample matrices.

Several sample pretreatment methods have been developed so far for extracting flavonoids in various samples, including reflux extraction, microwave-assisted extraction, pressurized liquid extraction, ultrasonic-assisted extraction, and the like. However, these methods generally require large amounts of toxic and hazardous organic reagents and long extraction times. In recent decades, various novel pretreatment technologies such as Solid Phase Extraction (SPE), solid Phase Microextraction (SPME), magnetic Solid Phase Extraction (MSPE), and Dispersed Solid Phase Extraction (DSPE) have emerged to play an important role in the pretreatment of complex samples. The solid phase extraction technology is a sample pretreatment method which is very widely applied, and has the advantages of high enrichment factor, high separation speed, less reagent consumption, simple operation and the like. In addition, separation and analysis of analytes in complex samples can be achieved through off-line, on-line and other modes in combination with chromatographic techniques and the like.

The novel sample pretreatment technologies are all extraction methods based on adsorbents, and the performance of the adsorption materials directly restricts the extraction behaviors of the methods, so that the development of efficient and stable novel adsorbents has become a research hot spot in the technical field of pretreatment. With the development of Metal Organic Frameworks (MOFs) and Covalent Organic Frameworks (COFs) synthesis technology in recent years, MOF/COF composite materials prepared by combining MOFs and COFs have emerged as an emerging porous hybrid material. The prepared MOF/COF composite material not only inherits the self characteristics of abundant porous structures, ultrahigh porosity, large specific surface area and the like, but also often shows unexpected new characteristics through the synergistic effect of each component, so that the MOF/COF composite material has great application potential in different fields of membrane separation, sensing, catalysis and the like, but has less research on the composite material in the field of solid-phase extraction, and particularly has not been reported in separation detection of flavonoid substances in food matrixes. According to the invention, the MOF@COF core-shell composite material is used as a solid phase extraction adsorbent, so that flavonoid components in food can be extracted efficiently.

Disclosure of Invention

The invention aims to provide a preparation method of a MOF@COF core-shell composite material, which is combined with a high performance liquid chromatography method, and is applied to enrichment, analysis and determination of flavonoid substances in food.

1. Preparation of MOF@COF core-shell composite material

The preparation method of the MOF@COF core-shell composite material comprises the following steps:

(1) Preparation of amino-functionalized MOFs: dissolving 2-amino terephthalic acid and ferric trichloride hexahydrate in N, N-dimethylformamide, uniformly mixing by ultrasonic, transferring the mixed solution into an autoclave, and performing solvothermal treatment at 100-140 ℃ for 16-24 hours to obtain the amino-functionalized MOFs. Wherein the molar ratio of the 2-amino terephthalic acid to the ferric trichloride hexahydrate is 1:1-1:2.

(2) Preparation of MOF@COF core-shell composite material: adding the prepared MOFs with the amino functionalization into a mixed solution of 1, 4-dioxane and mesitylene, and carrying out ultrasonic treatment to uniformly mix the MOFs with the mixed solution; and then, sequentially adding 4-formylphenylboric acid and 1, 3, 5-tris (4-aminophenylbenzene) into the suspension, continuously carrying out ultrasonic treatment on the suspension, and carrying out solvothermal treatment on the reaction mixture at 100-140 ℃ for 60-84 hours after the suspension is uniformly mixed to obtain the MOF@COF core-shell composite material. Wherein, in the mixed solution of the 1, 4-dioxane and the mesitylene, the volume ratio of the 1, 4-dioxane to the mesitylene is 1:1; the mass ratio of the 4-formylphenyl boric acid to the 1, 3, 5-tri (4-aminophenyl benzene) is 1:1-1.5:1.

The invention firstly utilizes a solvothermal synthesis method to prepare amino-functionalized metal-organic framework material (NH) ₂ -MILs-101 (Fe)); secondly, adding the aminated MOFs into a synthesis system of a covalent organic framework material (TAPB-FPBA-COF), and constructing a covalent connected MOF@COF core-shell composite material in situ by utilizing a Schiff base reaction between the two components; and finally, filling the prepared MOF@COF core-shell composite material serving as a solid phase extraction adsorbent filler into an empty extraction column to prepare a solid phase extraction column, and carrying out detection analysis on the enriched flavonoid compounds by combining a High Performance Liquid Chromatography (HPLC) technology.

FIG. 1 (a) is a scanning electron microscope image of a MOF, which is a polyhedral structure with smooth surface; (b) The scanning electron microscope image is a MOF@COF core-shell composite material, inherits the polyhedral form of the MOF, and the surface is obviously rougher; (c) And (d) is a transmission electron microscope image of the MOF@COF core-shell composite material at different angles, which shows that the morphology of the composite material is a core-shell structure. FIG. 2 is an XRD contrast pattern of MOF, COF and MOF@COF core-shell composites, XRD showing that the MOF@COF core-shell composites have both MOF and COF characteristic diffraction peaks, demonstrating successful preparation of the composites.

2. MOF@COF core-shell composite material used as solid phase extraction adsorbent for flavonoid substances in grape juice sample

The MOF@COF core-shell composite material is used for enriching and detecting flavonoid substances in food, wherein the flavonoid substances comprise quercetin, luteolin and apigenin, and specifically comprise the following steps:

(1) Preparing a solid phase extraction column: and filling the prepared solid phase extraction adsorbent MOF@COF core-shell composite material serving as an adsorbent filler into an empty extraction column.

(2) Sample preparation: taking a food sample containing flavonoid substances, centrifuging, taking supernatant, and diluting with ultrapure water to form a uniform solution; filtering all diluted sample solutions through a 0.45 mu m aperture membrane, and storing in a refrigerator at the temperature of 4 ℃ for further solid phase extraction treatment; the flow rate of the sample solution in the sample loading is 1 mL min ^-1 The method comprises the steps of carrying out a first treatment on the surface of the The eluent is methanol solution containing 5% phosphoric acid; the elution flow rate was 0.2 mL min ^-1 。

(3) Solid phase extraction: activating: connecting the filled extraction column to a solid phase extraction instrument, and respectively activating and cleaning the solid phase extraction column by using methanol and distilled water; loading: taking a sample solution, passing through a solid phase extraction column at a certain flow rate under the assistance of a vacuum pump, and fully contacting with the MOF@COF core-shell composite material adsorbent for adsorption; leaching: after the sample loading is completed, the adsorbent is washed by distilled water to remove impurities; eluting: and eluting the flavonoid compounds adsorbed by the adsorbent by using eluent to achieve the purpose of separation and enrichment.

(4) And (3) analysis and detection: performing HPLC-UV analysis detection on the eluent obtained in the step (3); the HPLC conditions were: hedera ODS-2C 18 column (4.6 mm ×250 mm, diameter 5 μm); phosphoric acid aqueous solution/methanol (35/65, v/v) with mobile phase of 0.25% (v/v); the flow rate is 1 mL min ^-1 The method comprises the steps of carrying out a first treatment on the surface of the The temperature of the column temperature box is 25 ℃; sampling 20 mu L;the detection wavelength was 360 nm.

Compared with the prior art, the invention has the beneficial effects that:

(1) The MOF@COF core-shell composite material prepared by the invention realizes covalent bonding of two materials through Schiff base reaction between amino functionalized MOFs and COFs components, and is more stable and firm compared with other synthesis modes.

(2) Compared with single MOFs, the MOF@COF core-shell composite material prepared by the invention combines the COFs shell with better chemical stability, and the stability of the composite material is better than that of the single MOFs.

(3) The solid phase extraction adsorbent prepared by the invention not only has larger specific surface area and rich porous structure, but also contains polar hydroxyl and hydrophobic COFs shell, can generate multiple cross acting forces such as hydrogen bond action, hydrophobic action, pi-pi stacking action, lewis acid-base interaction and the like with flavonoid compounds such as quercetin, luteolin, apigenin and the like in food, and has large adsorption capacity and good selectivity on flavonoid substances.

(4) The preparation method of the synthesized solid phase extraction column is simple, the amount of the adsorbent filler is small, and the solid phase extraction column can be repeatedly used.

(5) The solid phase extraction separation method provided by the invention solves the problems of long extraction time and pollution caused by using a large amount of organic solvents in the traditional separation and enrichment method of flavonoid compounds, simplifies the pretreatment process of samples and reflects the concept of green chemistry.

Drawings

FIG. 1 is a topographical map of a preparation material: (a) Is NH ₂ -scanning electron microscopy of MILs-101 (Fe); (b) is a scanning electron microscope image of the MOF@COF core-shell composite material; (c) And (d) is a transmission electron microscope image of different angles of the MOF@COF core-shell composite material.

Figure 2 is an XRD comparison of MOF, COF and mof@cof.

Fig. 3 is a physical diagram of a solid phase extraction column packed with mof@cof core-shell composite material adsorbent.

FIG. 4 is a chromatogram of quercetin (1), luteolin (2) and apigenin (3) in a grape juice sample.

FIG. 5 is a chromatogram of quercetin (1), luteolin (2) and apigenin (3) in a honey sample.

Detailed Description

The present invention will be described in further detail by way of specific examples, but embodiments of the present invention are not limited thereto.

Example 1: preparation of MOF@COF core-shell composite material

(1) Preparation of amino-functionalized MOFs: 250.6 mg (1.384 mmol) of 2-aminoterephthalic acid and 374.0 mg (1.384 mmol) of ferric trichloride hexahydrate were dissolved in 30 mL of DMF and mixed well by sonication, and the mixed solution was transferred to a 100 mL polytetrafluoroethylene-lined autoclave and subjected to solvothermal treatment at 120℃for 20 h. After the autoclave was cooled to room temperature, the product was separated from the reaction mixture by centrifugation and washed thoroughly with DMF and absolute ethanol, and then dried in vacuo at 60 ℃ for 12 h to give amino-modified NH ₂ MILs-101 (Fe) material (fig. 1 (a)).

(2) Preparation of MOF@COF core-shell composite material: in a 38 mL thick-walled pressure bottle, NH was prepared ₂ MIL-101 (Fe) was dissolved in a solution of COFs in 1, 4-dioxane/mesitylene (1/1 v/v,10 mL) and sonicated to mix well. Subsequently, 39 mg of 4-formylphenylboronic acid, 30 mg of 1, 3, 5-tris (4-aminophenylbenzene) were added sequentially to the suspension, and the suspension was continued to be sonicated. After they were mixed well, the reaction mixture was subjected to solvothermal treatment at 120 ℃ 72 h. After the thick-walled pressure flask was cooled to room temperature, the product was centrifuged and washed with anhydrous 1, 4-dioxane. The resulting material was purified by soxhlet extraction with dichloromethane and dried under vacuum at 60 ℃ for 12 h, successfully preparing NH ₂ MIL-101 (Fe) @ TAPB-FPBA-COF core-shell composites (FIGS. 1 (b), (c) and (d)).

Example 2: application of MOF@COF core-shell composite material in enrichment detection of flavonoid substances in grape juice

(1) Preparing a solid phase extraction column: the prepared MOF@COF core-shell composite material is weighed 5 mg, taken as an adsorbent filler, filled into a 3 mL SPE hollow column tube with a sieve plate, lightly tapped with fingers to uniformly fill the filler, and then a sieve plate is added on the adsorbent and is pressed, so that the solid phase extraction column (figure 3) is successfully prepared.

(2) Sample preparation: firstly, taking a grape juice sample purchased from a supermarket of 50 mL, and centrifuging at 10000 rpm for 8 min; then, taking 5 mL supernatant, diluting to 50 mL by using ultrapure water to form a uniform solution; finally, the diluted sample solution is filtered through a 0.45 mu m aperture membrane and stored in a refrigerator at 4 ℃ to be used as a grape juice adding standard solution or sample solution for further SPE treatment.

(3) Solid phase extraction: firstly, connecting the filled extraction column to a solid phase extraction instrument, and activating the material by using 2 mL methanol and 2 mL distilled water through an extraction column respectively; then, 20 mL is added with the standard solution or the sample solution to be processed with the assistance of a vacuum pump at the speed of 1.0 mL min ^-1 The flow velocity of the solution passes through the solid phase extraction column, so that the target object is fully contacted with the adsorbent for adsorption; after loading was completed, the adsorbent was washed with 1 mL distilled water to remove impurities; finally, the flavonoids adsorbed by the adsorbent were eluted with 1 mL methanol solution containing 5% phosphoric acid at a flow rate of 0.2 mL min-1 and collected directly for HPLC analysis.

(4) And (3) analysis and detection: detecting the eluent obtained in the step (3) in HPLC-UV, wherein a chromatogram is shown in figure 4, and the standard recovery rate of flavonoid substances in the grape juice sample is shown in table 1. The method has excellent adsorption performance on flavonoid substances in the grape juice sample, and can be used for enriching and detecting the flavonoid substances in the grape juice sample by combining high performance liquid chromatography.

The conditions of the high performance liquid chromatography are as follows: hedera ODS-2C 18 column (4.6 mm ×250 mm, diameter 5 μm); phosphoric acid aqueous solution/methanol (35/65, v/v) with mobile phase of 0.25% (v/v); the flow rate is 1 mL min ^-1 The method comprises the steps of carrying out a first treatment on the surface of the The temperature of the column temperature box is 25 ℃; sampling 20 mu L; the detection wavelength was 360 nm.

The data in the table show that the adsorbent prepared by the invention has high recovery rate of flavonoid substances in grape juice samples.

Example 3: application of MOF@COF core-shell composite material in enrichment detection of flavonoid substances in honey

(2) Sample preparation: firstly, weighing a 5 g honey sample, and diluting the honey sample to 50 mL by using ultrapure water to form a uniform solution; the diluted sample solution was then filtered through a 0.45 μm pore size membrane and stored in a refrigerator at 4 ℃ as a honey-spiked or sample solution for further SPE processing.

(3) Solid phase extraction: firstly, connecting the filled extraction column to a solid phase extraction instrument, and activating the material by using 2 mL methanol and 2 mL distilled water through an extraction column respectively; then, 20 mL is added with the standard solution or the sample solution to be processed with the assistance of a vacuum pump at the speed of 1.0 mL min ^-1 The flow velocity of the solution passes through the solid phase extraction column, so that the target object is fully contacted with the adsorbent for adsorption; after loading was completed, the adsorbent was washed with 1 mL distilled water to remove impurities; finally, the mixture was treated with 1. 1 mL in methanol with 5% phosphoric acid at 0.2 mL min ^-1 The flavonoids adsorbed by the adsorbent are eluted at a flow rate and directly collected for HPLC analysis.

(4) And (3) analysis and detection: detecting the eluent obtained in the step (3) in HPLC-UV, wherein a chromatogram is shown in figure 5, and the standard recovery rate of flavonoid substances in the honey sample is shown in table 2. The method has excellent adsorption performance on flavonoid substances in the grape juice sample, and can be used for enriching and detecting the flavonoid substances in the grape juice sample by combining high performance liquid chromatography.

The conditions of the high performance liquid chromatography are as follows: hedera ODS-2C 18 column (4.6 mm ×250 mm, diameter 5 μm); phosphoric acid aqueous solution/methanol (35/65, v/v) with mobile phase of 0.25% (v/v); the flow rate was 1 mL ·min ^-1 The method comprises the steps of carrying out a first treatment on the surface of the The temperature of the column temperature box is 25 ℃; sampling 20 mu L; the detection wavelength was 360 nm.

The data in the table show that the adsorbent prepared by the invention has high recovery rate of flavonoid substances in the honey sample.

The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above examples, and any other changes, modifications, substitutions, combinations, and simplifications that do not depart from the spirit and principle of the present invention should be made in the equivalent manner, and the embodiments are included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. The application of the MOF@COF core-shell composite material as a solid phase extraction adsorbent in enrichment detection of flavonoid substances in food is characterized in that: the enrichment detection of flavonoid substances in food by using the MOF@COF core-shell composite material comprises the following steps of:

(1) Preparing a solid phase extraction column: filling the prepared solid phase extraction adsorbent MOF@COF core-shell composite material serving as an adsorbent filler into an empty extraction column;

(2) Sample preparation: taking a food sample containing flavonoid substances, centrifuging, taking supernatant, and diluting with ultrapure water to form a uniform solution; filtering all diluted sample solutions through a 0.45 mu m aperture membrane, and storing in a refrigerator at the temperature of 4 ℃ for further solid phase extraction treatment; the food sample is honey or grape juice; the flavonoid comprises quercetin, luteolin and apigenin;

(3) Solid phase extraction: activating: connecting the filled extraction column to a solid phase extraction instrument, and respectively activating and cleaning the solid phase extraction column by using methanol and distilled water; loading: taking a sample solution, passing through a solid phase extraction column at a certain flow rate under the assistance of a vacuum pump, and fully contacting with the MOF@COF core-shell composite material adsorbent for adsorption; leaching: after the sample loading is completed, the adsorbent is washed by distilled water to remove impurities; eluting: eluting the flavonoid compounds adsorbed by the adsorbent by using eluent to achieve the purpose of separation and enrichment; the eluent is methanol solution containing 5% phosphoric acid;

(4) And (3) analysis and detection: performing HPLC-UV analysis detection on the eluent obtained in the step (3);

the preparation method of the MOF@COF core-shell composite material comprises the following steps of:

(1) Preparation of amino-functionalized MOFs: dissolving 2-amino terephthalic acid and ferric trichloride hexahydrate in N, N-dimethylformamide, uniformly mixing by ultrasonic, transferring the mixed solution into an autoclave, performing solvothermal treatment at 100-140 ℃ for 16-24 hours, centrifuging, washing and vacuum drying to obtain amino-functionalized MOFs;

(2) Preparation of MOF@COF core-shell composite material: adding the prepared MOFs with the amino functionalization into a mixed solution of 1, 4-dioxane and mesitylene, and carrying out ultrasonic treatment to uniformly mix the MOFs with the mixed solution; and sequentially adding 4-formylphenylboric acid and 1, 3, 5-tris (4-aminophenylbenzene) into the suspension, continuously carrying out ultrasonic treatment on the suspension, carrying out solvothermal treatment on the reaction mixture at 100-140 ℃ for 60-84 hours after the suspension is uniformly mixed, centrifuging, washing and purifying to obtain the MOF@COF core-shell composite material.

2. The use of the mof@cof core-shell composite material as claimed in claim 1 as a solid phase extraction adsorbent for enrichment detection of flavonoids in food, characterized in that: in the enrichment detection step (3), the flow rate of the sample solution in the sample loading is 1 mL min ^-1 The method comprises the steps of carrying out a first treatment on the surface of the The elution flow rate was 0.2 mL min ^-1 。

3. The use of the mof@cof core-shell composite material as claimed in claim 1 as a solid phase extraction adsorbent for enrichment detection of flavonoids in food, characterized in that: in the enrichment detection step (4), the HPLC conditions are: hedera ODS-2C 18 chromatographic column with specification of 4.6 mm ×250 mm and diameter of 5 μm; the mobile phase was 0.25% by volumePhosphoric acid aqueous solution and methanol, wherein the volume ratio of the phosphoric acid aqueous solution to the methanol is 35:65; the flow rate is 1 mL min ^-1 The method comprises the steps of carrying out a first treatment on the surface of the The temperature of the column temperature box is 25 ℃; sampling 20 mu L; the detection wavelength was 360 nm.

4. The use of the mof@cof core-shell composite material as claimed in claim 1 as a solid phase extraction adsorbent for enrichment detection of flavonoids in food, characterized in that: in the preparation step (1) of the MOF@COF core-shell composite material, the molar ratio of the 2-amino terephthalic acid to the ferric trichloride hexahydrate is 1:1-1:2.

5. The use of the mof@cof core-shell composite material as claimed in claim 1 as a solid phase extraction adsorbent for enrichment detection of flavonoids in food, characterized in that: in the preparation step (2) of the MOF@COF core-shell composite material, the volume ratio of the 1, 4-dioxane to the mesitylene solution in the mixed solution of the 1, 4-dioxane and the mesitylene is 1:1.

6. The use of the mof@cof core-shell composite material as claimed in claim 1 as a solid phase extraction adsorbent for enrichment detection of flavonoids in food, characterized in that: in the preparation step (2) of the MOF@COF core-shell composite material, the mass ratio of the 4-formylphenyl boric acid to the 1, 3, 5-tris (4-aminophenyl benzene) is 1:1-1.5:1.