CN111171212A - Metal organic framework surface molecularly imprinted polymer and preparation method and application thereof - Google Patents
Metal organic framework surface molecularly imprinted polymer and preparation method and application thereof Download PDFInfo
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Abstract
The invention discloses a metal organic framework surface molecularly imprinted polymer and a preparation method thereof, wherein the preparation method comprises the following steps: with ZrCl4And 4, 4' -biphenyl dicarboxylic acid are taken as raw materials to prepare a metal organic framework UiO-67; dissolving diazinon in a proper amount of ultrapure water, adding a dispersing agent and a solvent, and carrying out template-monomer compounding by using bifunctional monomer methacrylic acid and 4-vinylpyridine to obtain a template-monomer compound mixed solution; and adding a cross-linking agent, an initiator and a metal organic framework UiO-67 serving as a surface imprinting carrier material into the mixed solution of the template-monomer compound, and carrying out polymerization reaction to obtain the metal organic framework surface molecularly imprinted polymer. The invention also discloses application of the metal organic framework surface molecularly imprinted polymer in surface Raman enhanced detection of diazinon in an environmental water body. The preparation method is simple and convenient to operate, and the raw materials are cheap and easy to obtain; the metal organic framework surface molecularly imprinted polymer is combined with surface Raman enhancement to detect the selective separation effect of diazinon in the environmental water body.
Description
Technical Field
The invention belongs to the field of molecularly imprinted polymers, and particularly relates to a metal organic framework surface molecularly imprinted polymer and a preparation method and application thereof.
Background
Molecular Imprinting (MIT) is a new technology for preparing polymers having specific recognition ability for target compounds, and is an edge discipline developed by combining disciplines of polymer chemistry, biochemistry, and the like. Molecularly Imprinted Polymers (MIPs) have the characteristics of high affinity and selectivity, strong adverse environment resistance, good stability, long service life and the like, and are applied to the fields of simulated antibodies and receptors, enzyme simulation catalysis, immunoassay, separation and purification of drugs and herbicides, separation of isomers and enantiomers, selective catalysis, identification of biomacromolecules such as amino acids and polypeptides and the like. The molecular imprinting technology has good application prospect particularly in the fields of analytical chemistry such as chromatographic separation, chiral substance resolution, bionic sensors, solid phase extraction and the like.
Molecularly Imprinted Polymers (MIPs) prepared by the conventional method have the disadvantages of difficulty in extraction of target molecules, low adsorption capacity, poor kinetic properties, and the like due to high degree of crosslinking. Imprinting target molecules on the surface of a carrier material is an imprinting technology emerging in recent years. The imprinted active sites are controlled on the surface of the carrier material, so that the adsorption capacity and the dynamic performance of the obtained MIPs can be greatly improved, and the MIPs have good application prospects in the fields of sewage treatment, chromatographic separation, chiral substance resolution, biomimetic sensors, solid-phase extraction and the like. The mesoporous silica-based material has the advantages of large specific surface area, simple and convenient modification, good stability, high mechanical strength and the like, and is very suitable for being used as a carrier material of Surface Molecularly Imprinted Polymers (SMIPs).
The diazinon is also called as Dihon pesticide and diazinon pesticide, has good systemic conduction effect, can inhibit the synthesis of acetylcholinesterase in insect bodies, and has good effect on preventing and treating cabbage caterpillar, cotton aphid, tryporyza incertulas, underground pests and the like. However, diazinon adversely affects the human nervous system. Based on the carcinogen list published by the world health organization international agency for research on cancer on day 27/10/2017, diazinon is in the class 2A carcinogen list. The residual amount of diazinon directly influences the quality safety of agricultural products. At present, the methods for removing diazinon mainly comprise an adsorption separation method, a bacterial and fungal degradation method, a chemical oxidation method, a solvent extraction method and the like. Each of these methods has advantages, but also has many limitations. If the liquid-liquid extraction technology is used in a large amount, secondary pollution can be caused by organic solvents; the operation of the chemical oxidation process is more complex and the cost is higher; the membrane separation technology has the problems of membrane blockage and the like. Adsorption technology is widely used because of its simplicity of operation, high efficiency of enrichment and low cost. The activated carbon is the most common adsorbent, but the adsorption separation of the activated carbon has the defects of poor selectivity, small adsorption capacity, long time for reaching equilibrium and the like.
Therefore, the development of a novel adsorbent material with low cost and high selectivity for separating diazinon is urgently needed.
Disclosure of Invention
The invention provides a metal organic framework surface molecularly imprinted polymer and a preparation method thereof, and the method is simple and convenient to operate, and the raw materials are cheap and easy to obtain; the obtained metal organic framework surface molecularly imprinted polymer is combined with surface Raman enhancement to detect the selective separation effect of diazinon in the environmental water body.
The technical scheme adopted by the invention is as follows:
a preparation method of a metal organic framework surface molecularly imprinted polymer comprises the following steps:
(1) with ZrCl4And 4, 4' -biphenyl dicarboxylic acid as raw materials, dissolving in DMF under acidic condition, and carrying out solvent heat treatment on the dissolved mixture. After the reaction is cooled to room temperature, centrifugally collecting, and carrying out two-step activation treatment by using DMF (dimethyl formamide) and acetone to obtain an activated metal organic framework UiO-67;
(2) dissolving diazinon in a proper amount of ultrapure water, adding a dispersing agent and a solvent, carrying out template-monomer compounding by using bifunctional monomer methacrylic acid and 4-vinylpyridine, and stirring to obtain a template-monomer compound mixed solution;
(3) adding a cross-linking agent, an initiator and a surface imprinting carrier material UiO-67 into the mixed solution of the template-monomer compound, performing ultrasonic dispersion, introducing nitrogen, performing an ice-water bath, and performing a polymerization reaction; and after the reaction is finished, removing the imprinted template by using an eluant, and drying to obtain the metal organic framework surface molecularly imprinted polymer.
The preparation method provided by the invention is simple to operate, the raw materials are cheap and easy to obtain, and the metal organic framework surface molecularly imprinted polymer material with larger specific surface area and better thermal stability can be obtained.
In the step (1), the preparation method of the metal organic framework UiO-67 comprises the following steps: reacting ZrCl4And 4, 4' -biphenyldicarboxylic acid in a molar ratio of 1: 1-2, adding 8-12 mmol of glacial acetic acid and 4-6 mmol of concentrated hydrochloric acid, and heat treating with a solvent at 110-130 deg.C to 18E24 h; centrifuging and collecting the product, and activating the product in two steps: firstly, soaking the mixture in 20-40 mL of DMF containing 0.5-1.0 mL of HCl, and heating the mixture for 5-8 hours at the temperature of 100 ℃; secondly, acetone is used for replacing DMF, the product is soaked for 5-8 hours at the temperature of 60 ℃, and the soaking is repeated for 3-5 times; and centrifuging to collect a final product, and drying in vacuum to obtain the activated metal organic framework UiO-67.
The specific surface area of the activated metal organic framework UiO-67 is 2100-2300 m2A pore diameter of 1.17 to 1.61nm and a pore volume of 1.1 to 1.5cm3/g。
In the step (2), in the preparation process of the template-monomer compound, the adding molar ratio of the template diazinon to the monomer 4-vinylpyridine to the methacrylic acid is 1: 1-8: 1 to 8. .
Preferably, the adding molar ratio of the monomer 4-vinylpyridine to the methacrylic acid is 1:2 to 8. More preferably, the adding molar ratio of the monomer 4-vinylpyridine to the methacrylic acid is 1: 4.
in the step (2), 30-50 mL of a dispersing agent is added, wherein the dispersing agent is a hydroxymethyl cellulose solution with the mass fraction of 1-5%; adding 15-20 mL of solvent, wherein the solvent is toluene.
In the step (3), in the preparation process of the metal organic framework surface molecularly imprinted polymer, the adding mass ratio of the template-monomer compound to the metal organic framework UiO-67 is 6-23: 5-20, wherein the adding molar ratio of the template-monomer compound to the cross-linking agent is 1:2 to 4. The cross-linking agent is Ethylene Glycol Dimethacrylate (EGDMA), and the initiator is Azobisisobutyronitrile (AIBN).
Preferably, the adding mass ratio of the template-monomer compound to the metal organic framework UiO-67 is 0.9: 1-2; the adding molar ratio of the template-monomer compound to the cross-linking agent is 1: 2.67.
in the step (3), the ice-water bath time is 10-20 min; the temperature of the polymerization reaction is 50-60 ℃, and the reaction time is 18-24 h.
In the step (3), the eluent is methanol: the method comprises the following steps of (1) mixing acetic acid, wherein the volume ratio of methanol to acetic acid in the mixture is 7-9: 1 to 3.
The invention also provides a metal organic framework surface molecularly imprinted polymer prepared by the method.
The specific surface area of the metal organic framework surface molecularly imprinted polymer is 780-900 m2A pore diameter of 0.6 to 1.0nm and a pore volume of 0.64 to 0.86cm3/g。
The invention also aims to provide application of the metal organic framework surface molecularly imprinted polymer combined surface Raman enhancement technology in removing diazinon in water. The molecularly imprinted polymer on the surface of the metal organic framework can efficiently and selectively separate diazinon from a water body, and the standard addition recovery rate reaches 92.7-108.2%.
Compared with the prior art, the method has the advantages that:
(1) the preparation method is simple to operate, the raw materials are cheap and easy to obtain, and the approach for obtaining the metal organic framework surface molecularly imprinted polymer material is simple and convenient;
(2) the imprinting process is carried out on the surface of the metal organic framework, and the synthesized imprinting material has the advantages of large specific surface area, high mass transfer rate, more exposed surface imprinting active sites, high selectivity and high potential for quickly separating diazinon in an actual sample with high selectivity, and is suitable for Raman-enhanced high-sensitivity detection and high-selectivity and quick separation of diazinon in a sample with complex environment.
Drawings
FIG. 1 is a flow chart of the preparation of the metal organic framework surface molecularly imprinted polymer provided by the invention;
FIG. 2 is a transmission electron micrograph (a), an infrared spectrum (b), a thermogram (c) and an X-ray photoelectron spectrum (d) of the MOFs-MIPs prepared in example 1;
FIG. 3 is a graph of the effect of different functional monomer ratios on adsorption capacity;
FIG. 4 is a graph showing the effect of different amounts of UiO-67 added on adsorption capacity;
FIG. 5 is a graph showing the adsorption kinetics of MOFs-MIPs, MOFs-NIPs, MIPs and NIPs;
FIG. 6 is a Raman enhancement spectrogram of diazinon with 0.5mmol/L of mechanics such as adsorption, an inset (left) is a micro Raman imaging spectrogram of MOFs-MIPs after the diazinon is adsorbed, and a right is a micro Raman imaging spectrogram after the MOFs-MIPs desorbs the diazinon;
FIG. 7 is the adsorption isotherms of MOFs-MIPs, MOFs-NIPs, MIPs and NIPs;
FIG. 8 is an adsorption isotherm of MOFs-MIPs fitted with Langmuir (a) and Freundlich (b) isothermal models;
FIG. 9 shows the adsorption selectivity of MOFs-MIPs and MOFs-NIPs;
FIG. 10 is a graph of the regeneration performance of the MOFs-MIPs and MOFs-NIPs;
FIG. 11 is a Raman enhancement spectrum of diazinon at different concentrations (Raman shift at 660 cm)-1)；
FIG. 12 is a standard graph of diazinon.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail with reference to the accompanying drawings and examples. It should be understood that the detailed description and specific examples, while indicating the scope of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
The invention provides a preparation process of an organometallic framework surface molecularly imprinted polymer, which is shown in figure 1.
Example 1
(1) Preparation of a Metal-organic framework UiO-67
Reacting ZrCl4(233mg,1mmol), 4, 4' -biphenyldicarboxylic acid (BPDC, 242mg, 1mmol), acetic acid (0.6g, 10mmol) and HCl (0.33mL,4mmol added to 34mL DMF the mixture after solvent treatment in an oven at 120 ℃ for 24h after cooling the reaction to room temperature, white powder UiO-67 was collected by centrifugation and washed with DMF at room temperature.
The synthesized UiO-67 was soaked in 20mL of DMF containing 0.5mL of HCl and heated at 100 ℃ for 6h to remove incompletely reacted ligand and acetic acid embedded in the backbone. Then, UiO-67 was soaked at 60 ℃ for 6h with acetone instead of DMF and repeated three times to remove residual DMF from the material. Finally, the material was collected by centrifugation and dried in a vacuum oven at 100 ℃ for 12 h.
(2) Dissolving diazinon (1.25mmol, 380mg) in 30mL of deionized water, adding bifunctional monomers of 4-vinylpyridine (1.25mmol, 132mg) and methacrylic acid (5.0mmol, 430mg), adding 30mL of 1% hydroxymethyl cellulose acetate and 15mL of toluene, and stirring for 3 hours to obtain a mixed solution of a template-monomer complex;
(3) to the mixed solution were added a crosslinking agent EGDMA (20mmol), an initiator AIBN (40mg) and a matrix material UiO-67(1.0 g).
(4) The mixed solution is subjected to ultrasonic treatment for 10 minutes, nitrogen is introduced for 15 minutes, the mixed solution is placed in an ice-water bath for 15 minutes and then is placed in a water bath kettle for polymerization for 6 hours at the temperature of 50 ℃ and for polymerization for 8 hours at the temperature of 60 ℃.
(5) Washing the obtained product for multiple times by using an acetone/water (1:1, v: v) mixed solution, washing away unreacted functional monomers and a cross-linking agent, centrifugally collecting the product, and drying to obtain the metal organic framework surface molecularly imprinted polymer.
(6) Using methanol: the ratio of acetic acid is 8:2 (v: v) as eluent to elute the template molecule diazinon.
A transmission electron micrograph of the MOFs-MIPs prepared in example 1 is shown in (a) of FIG. 1, an infrared spectrum is shown in (b) of FIG. 1, a thermogravimetric curve is shown in (c) of FIG. 1, and an X-ray photoelectron spectrum is shown in (d) of FIG. 1.
Comparative example 1
(1) Dissolving a bifunctional monomer, 4-vinylpyridine (1.25mmol, 132mg) and methacrylic acid (5.0mmol, 430mg) in 30mL of deionized water, adding 30mL of 1% hydroxymethyl cellulose acetate and 15mL of toluene, and stirring for 3 hours to obtain a mixed solution;
(2) to the mixed solution were added a crosslinking agent EGDMA (20mmol), an initiator AIBN (40mg) and a matrix material UiO-67(1.0 g).
(3) The mixed solution is subjected to ultrasonic treatment for 10 minutes, nitrogen is introduced for 15 minutes, the mixed solution is placed in an ice-water bath for 15 minutes and then is placed in a water bath kettle for polymerization for 6 hours at the temperature of 50 ℃ and for polymerization for 8 hours at the temperature of 60 ℃.
(4) Washing the obtained product for multiple times by using acetone/water (1:1, v: v) mixed liquor, washing away unreacted functional monomers and cross-linking agents, centrifuging, collecting the product, and drying to obtain the non-molecularly imprinted polymers (MOFs-NIPs) on the surface of the metal organic framework.
Comparative example 2
(1) Dissolving diazinon (1.25mmol, 380mg) in 30mL of deionized water, adding the bifunctional monomers 4-vinylpyridine (1.25mmol, 132mg) and methacrylic acid (5.0mmol, 430mg) in 30mL of deionized water, adding 30mL of 1% hydroxymethyl cellulose acetate and 15mL of toluene, and stirring for 3 hours to obtain a mixed solution;
(2) to the mixed solution were added EGDMA (20mmol) as a crosslinking agent and AIBN (40mg) as an initiator.
(3) The mixed solution is subjected to ultrasonic treatment for 10 minutes, nitrogen is introduced for 15 minutes, the mixed solution is placed in an ice-water bath for 15 minutes and then is placed in a water bath kettle for polymerization for 6 hours at the temperature of 50 ℃ and for polymerization for 8 hours at the temperature of 60 ℃.
(4) Washing the obtained product for multiple times by using an acetone/water (1:1, v: v) mixed solution, washing away unreacted functional monomers and a cross-linking agent, centrifuging, collecting the product, and drying to obtain the Molecularly Imprinted Polymers (MIPs).
(5) Using methanol: the ratio of acetic acid is 8:2 (v: v) as eluent to elute the template molecule diazinon.
Comparative example 3
(1) Dissolving a bifunctional monomer, 4-vinylpyridine (1.25mmol, 132mg) and methacrylic acid (5.0mmol, 430mg) in 30mL of deionized water, adding 30mL of 1% hydroxymethyl cellulose acetate and 15mL of toluene, and stirring for 3 hours to obtain a mixed solution;
(2) to the mixed solution were added EGDMA (20mmol) as a crosslinking agent and AIBN (40mg) as an initiator.
(3) The mixed solution is subjected to ultrasonic treatment for 10 minutes, nitrogen is introduced for 15 minutes, the mixed solution is placed in an ice-water bath for 15 minutes and then is placed in a water bath kettle for polymerization for 6 hours at the temperature of 50 ℃ and for polymerization for 8 hours at the temperature of 60 ℃.
(4) Washing the obtained product for multiple times by using an acetone/water (1:1, v: v) mixed solution, washing away unreacted functional monomers and cross-linking agents, centrifuging, collecting the product, and drying to obtain non-molecularly imprinted polymers (NIPs).
Example 2
Preparing a series of metal organic framework surface molecularly imprinted polymers with different functional monomer ratios:
(1) mixing diazinon: 4-vinylpyridine: methacrylic acid (1:8:1, 1:4:1, 1:2:1, 1:1:1, 1:1:2, 1:1:8), adding 30mL of 1% hydroxymethyl cellulose acetate and 15mL of toluene, and stirring for 3 hours to obtain mixed solutions of template-monomer complexes in different proportions;
(2) to the mixed solution were added a crosslinking agent EGDMA (20mmol), an initiator AIBN (40mg) and a matrix material UiO-67(1.0 g).
(3) The mixed solution is subjected to ultrasonic treatment for 10 minutes, nitrogen is introduced for 15 minutes, the mixed solution is placed in an ice-water bath for 15 minutes and then is placed in a water bath kettle for polymerization for 6 hours at the temperature of 50 ℃ and for polymerization for 8 hours at the temperature of 60 ℃.
(4) Washing the obtained product for multiple times by using an acetone/water (1:1, v: v) mixed solution, washing away unreacted functional monomers and a cross-linking agent, centrifugally collecting the product, and drying to obtain a series of metal organic framework surface molecularly imprinted polymers.
(5) Using methanol: the ratio of acetic acid is 8:2 (v: v) as eluent to elute the template molecule diazinon.
Example 3
Preparing a series of metal organic framework surface molecularly imprinted polymers with different UiO-67 addition amounts:
(1) dissolving diazinon (1.25mmol, 380mg) in 30mL of deionized water, adding bifunctional monomers of 4-vinylpyridine (1.25mmol, 132mg) and methacrylic acid (5.0mmol, 430mg), adding 30mL of 1% hydroxymethyl cellulose acetate and 15mL of toluene, and stirring for 3 hours to obtain a mixed solution of a template-monomer complex;
(2) to the mixed solution were added a crosslinking agent EGDMA (20mmol), an initiator AIBN (40mg) and a matrix material UiO-67 (0.1, 0.5, 1.5, 2.0g, respectively).
(4) The mixed solution is subjected to ultrasonic treatment for 10 minutes, nitrogen is introduced for 15 minutes, the mixed solution is placed in an ice-water bath for 15 minutes and then is placed in a water bath kettle for polymerization for 6 hours at the temperature of 50 ℃ and for polymerization for 8 hours at the temperature of 60 ℃.
(5) Washing the obtained product for multiple times by using an acetone/water (1:1, v: v) mixed solution, washing away unreacted functional monomers and cross-linking agents, centrifugally collecting the product, and drying to obtain the series of metal organic framework surface molecularly imprinted polymers.
(6) Using methanol: the ratio of acetic acid is 8:2 (v: v) as eluent to elute the template molecule diazinon.
Example 4
Adsorption kinetics experiment: 30mg of MOFs-MIPs prepared in example 1, MOFs-NIPs prepared in comparative example 1, MIPs prepared in comparative example 2 and NIPs prepared in comparative example 3 are respectively weighed and added into 8mL of diazinon solution with the concentration of 0.5mmol/L, and the kinetic models of the MOFs-MIPs, the MOFs-NIPs, the MIPs and the NIPs are researched by measuring the adsorption capacity under different adsorption times.
Example 5
Isothermal adsorption experiment: 30mg of MOFs-MIPs prepared in example 1, MOFs-NIPs prepared in comparative example 1, MIPs prepared in comparative example 2 and NIPs prepared in comparative example 3 were weighed respectively and added to 8mL of absolute ethanol: adsorbing in diazinon solutions with different concentrations prepared by water (2: 3, V: V) for a certain time, centrifuging, and measuring the concentration of diazinon in the supernatant by surface Raman enhanced spectroscopy.
Example 6
Selective adsorption experiments: selecting acephate, glyphosate and glufosinate as competitive substances, preparing a mixed solution of diazinon and the competitive substances, wherein the initial concentration of the mixed solution is 0.5mmol/L, respectively weighing 30mg of MOFs-MIPs prepared in example 1 and MOFs-NIPs prepared in comparative example 1, adding the weighed materials into 8mL of the mixed solution, carrying out adsorption for 3h, carrying out centrifugal separation, obtaining a supernatant, namely the solution after MOFs-MIPs treatment, and measuring the concentration of each substance in the supernatant by using high performance liquid chromatography.
Desorption experiments: dispersing MOFs-MIPs adsorbing diazinon in methanol: eluting in mixed solution of acetic acid (8: 2, v/v), collecting eluent, calculating desorption efficiency, and experimental results show that the desorption efficiency can reach more than 90%.
FIG. 3 shows the effect of MOFs-MIPs prepared with different ratios of functional monomers (example 1 and example 3) on the adsorption capacity of the blots, as can be seen from FIG. 3 when 4-VP: the blotting effect was best when the MAA ratio was 1: 4.
FIG. 4 shows the effect of imprinting materials prepared with different amounts of UiO-67 (examples 1 and 4) on the adsorption capacity of diazinon, and it can be seen from FIG. 4 that the adsorption capacity reaches 131.2mg/g when the amount of UiO-67 added exceeds 1.0 g.
Wherein, the adsorption conditions in fig. 3 and fig. 4 are that 30mg of prepared series of MOFs-MIPs are respectively weighed and added into 8mL of diazinon solution with the concentration of 0.5mmol/L, after 2 hours of adsorption, centrifugal separation is carried out, the concentration of diazinon in the solution is determined by surface raman enhancement, and the adsorption capacity of a series of MOFs-MIPs is calculated.
FIG. 5 is a graph showing the adsorption kinetics of MOFs-MIPs, MOFs-NIPs, MIPs and NIPs; as can be seen from FIG. 5, the MOFs-MIPs have faster adsorption kinetics, the adsorption can reach equilibrium within 1.5h, and the imprinting factor is calculated to be 3.5. On the other hand, the adsorption kinetics curves of the MOFs-MIPs and the MIPs show that the MOFs-MIPs have higher saturated adsorption capacity and are 2.1 times of the MIPs. From this point, UiO-67 as a carrier of surface imprinting is used for preparing the surface imprinting material, and the surface imprinting material has better imprinting recognition sites, higher saturated adsorption capacity and faster mass transfer rate. The MOFs-MIPs and the MOFs-NIPs are subjected to primary/secondary dynamic curve fitting, and the dynamic curve fitting condition shows (table 1), the adsorption process is combined with a secondary dynamic adsorption model, and chemical adsorption is the main adsorption mode.
TABLE 1 MOFs-MIPs and MOFs-NIPs Primary/Secondary kinetic fitting data
FIG. 6 is a surface Raman enhancement spectrogram of 0.5mmol/L diazinon, wherein (the left embedded graph) the micro-Raman imaging spectrogram after the MOFs-MIPs adsorb the diazinon; (right embedded picture) a microscopic Raman imaging spectrogram after the MOFs-MIPs desorb diazinon; spectral conditions: the laser wavelength is 532 nm: the laser intensity is 5.0 mW; the exposure time was 50 Hz; the number of scans was 500. As can be seen from FIG. 6, the MOFs-MIPs can realize the high-selectivity separation and enrichment of diazine phosphorus in the aqueous solution through the adsorption and desorption process.
FIG. 7 is the adsorption isotherms of MOFs-MIPs, MOFs-NIPs, MIPs and NIPs; from FIG. 7, it can be seen that the adsorption capacity of MOFs-MIPs for diazinon increases rapidly with increasing initial concentration and slowly reaches a maximum at initial concentrations above 0.6 mmol/L. The saturated adsorption capacity of the MOFs-MIPs reaches 152.7mg/g, which is 2.2 times of the MIPs and 3.5 times of the MOFs-NIPs. The result shows that the MOFs-MIPs have stronger capability of selectively adsorbing diazine phosphorus than the MIPs and the MOFs-NIPs.
FIG. 8 is a graph of Langmuir and Freundlich isothermal models fitting the adsorption of diazinon data by MOFs-MIPs and MOFs-NIPs; from FIG. 8, it can be seen that the adsorption process of MOFs-MIPs conforms to Langmuir isothermal adsorption model and belongs to monolayer adsorption.
FIG. 9 shows the adsorption selectivity of MOFs-MIPs and MOFs-NIPs; as can be seen from FIG. 9, the adsorption capacity of MOFs-MIPs to diazinon is significantly higher than that of competing molecules such as glyphosate, acephate and glufosinate, which indicates that pore structures matched with the structure and size of diazinon exist in the MOFs-MIPs, and the pore structures and the diazinon have interactive binding sites, so that the MOFs-MIPs have higher selective recognition capability to the diazinon.
FIG. 10 is a study of the regeneration performance of MOFs-MIPs and MOFs-NIPs; from fig. 10 it can be seen that MOFs-MIPs can be recycled efficiently with a loss of about 20% of its saturated adsorption capacity after 6 cycles, demonstrating its high stability and reusability in the selective recognition of diazinon from aqueous solutions.
FIG. 11 is a Raman enhanced spectrum (660 cm) of diazinon at various concentrations detected-1At (c); FIG. 12 is a standard curve for detection of diazinon; as can be seen from FIG. 12, the linear relationship of A to C is good in the range of 10-1200 nM of diazinon aqueous solution, and the linear equation is as follows: a 2.85C +1.82, correlation coefficient R2The method detection limit (3 δ/K, n-11) was 3.6nM 0.9996.
And (3) analyzing an actual sample: the MOFs-MIPs are used for detecting diazinon in an actual water sample (tap water, river water and environmental wastewater from a laboratory), and the actual water sample is analyzed by adopting a standard addition method. Firstly, a water sample is subjected to high-speed centrifugal treatment to remove insoluble impurities in the water sample, and then the obtained water sample passes through a 0.40-micron filter membrane. Weighing 30mg of MOFs-MIPs, adding the MOFs-MIPs into 8mL of treated water sample, adsorbing for 3h, carrying out centrifugal separation, dispersing the MOFs-MIPs adsorbing diazinon in a mixed solution of methanol and acetic acid (volume ratio) of 8:2, desorbing the diazinon, carrying out centrifugal separation, collecting a desorption solution, and determining the content of the diazinon remained in the desorption solution by using a surface Raman enhanced spectrum; the results of the spiking recovery experiments are shown in table 2, because the sample has a low content of diazinon, and it can be seen from the data in the table that the Relative Standard Deviation (RSD) is in the range of 1.63% to 8.74%, and the recovery rate is between 92.7% and 108.2%. These results indicate that the MOFs-MIPs have high affinity, high selectivity and excellent adsorption capacity, and can be used for selective recognition and separation of trace amount of diazinon from an environmental water sample.
TABLE 2 determination of diazinon in actual Water samples
In the table, ND means no detection.
The above-mentioned embodiments are intended to illustrate the technical solutions and advantages of the present invention, and it should be understood that the above-mentioned embodiments are only the most preferred embodiments of the present invention, and are not intended to limit the present invention, and any modifications, additions, equivalents, etc. made within the scope of the principles of the present invention should be included in the scope of the present invention.
Claims (10)
1. A preparation method of a metal organic framework surface molecularly imprinted polymer is characterized by comprising the following steps:
(1) with ZrCl4Dissolving 4, 4' -biphenyldicarboxylic acid serving as a raw material in DMF (dimethyl formamide) under an acidic condition, and carrying out solvent heat treatment on the dissolved mixture; after the reaction is cooled to room temperature, centrifugally collecting, and carrying out activation treatment by using DMF (dimethyl formamide) and acetone to obtain an activated metal organic framework UiO-67;
(2) dissolving diazinon in a proper amount of ultrapure water, adding a dispersing agent and a solvent, carrying out template-monomer compounding by using bifunctional monomer methacrylic acid and 4-vinylpyridine, and stirring to obtain a template-monomer compound mixed solution;
(3) adding a cross-linking agent, an initiator and a metal organic framework UiO-67 serving as a surface imprinting carrier material into the mixed solution of the template-monomer compound, performing ultrasonic dispersion, introducing nitrogen, performing an ice-water bath, and performing a polymerization reaction; and after the reaction is finished, removing the imprinted template by using an eluant, and drying to obtain the metal organic framework surface molecularly imprinted polymer.
2. The method for preparing the organometallic framework surface molecularly imprinted polymer according to claim 1, wherein in the step (1), the preparation method of the organometallic framework UiO-67 is as follows: reacting ZrCl4And 4, 4' -biphenyldicarboxylic acid in a molar ratio of 1: 1-2 are mixed and placed in 30-50 mL of DMF, 8-12 mmol of glacial acetic acid and 4-6 mmol of concentrated hydrochloric acid are added at the same time, and the mixture is subjected to solvent heat treatment at 110-130 ℃ for 18-24 h; centrifuging and collecting a product, soaking the product in 20-40 mL of DMF (dimethyl formamide) containing 0.5-1.0 mL of HCl, and heating for 5-8 h at 100 ℃; then, acetone is used for replacing DMF, the product is soaked for 5-8 hours at the temperature of 60 ℃, and the soaking is repeated for 3-5 times; and centrifuging to collect a final product, and drying in vacuum to obtain the activated metal organic framework UiO-67.
3. The preparation method of the metal organic framework surface molecularly imprinted polymer according to claim 1, wherein in the step (2), the adding molar ratio of the template diazinon to the monomer 4-vinylpyridine to the methacrylic acid in the preparation process of the template-monomer composite is 1: 1-8: 1 to 8.
4. The preparation method of the metal organic framework surface molecularly imprinted polymer according to claim 1, characterized in that in the step (2), 30-50 mL of a dispersing agent is added, wherein the dispersing agent is a hydroxymethyl cellulose solution with the mass fraction of 1-5%; adding 15-20 mL of solvent, wherein the solvent is toluene.
5. The preparation method of the metal organic framework surface molecularly imprinted polymer according to claim 1, wherein in the step (3), in the preparation process of the metal organic framework surface molecularly imprinted polymer, the adding mass ratio of the template-monomer compound to the metal organic framework UiO-67 is 6-23: 5-20, wherein the adding molar ratio of the template-monomer compound to the cross-linking agent is 1: 2-4; the cross-linking agent is ethylene glycol dimethacrylate, and the initiator is azobisisobutyronitrile.
6. The preparation method of the metal organic framework surface molecularly imprinted polymer according to claim 1, wherein in the step (3), the time of the ice-water bath is 10-20 min; the temperature of the polymerization reaction is 50-60 ℃, and the reaction time is 18-24 h.
7. The method for preparing the metal-organic framework surface molecularly imprinted polymer according to claim 1, wherein in the step (3), the eluent is methanol: the method comprises the following steps of (1) mixing acetic acid, wherein the volume ratio of methanol to acetic acid in the mixture is 7-9: 1 to 3.
8. A metal organic framework surface molecularly imprinted polymer, characterized by being prepared by the method of any one of claims 1 to 7.
9. The metal-organic framework surface molecularly imprinted polymer according to claim 8, wherein the specific surface area of the metal-organic framework surface molecularly imprinted polymer is 780-900 m2A pore diameter of 0.6 to 1.0nm and a pore volume of 0.64 to 0.86cm3/g。
10. The application of the metal organic framework surface molecularly imprinted polymer according to claim 8 or 9 in surface Raman-enhanced detection of diazinon in an environmental water body.
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| CN115141408A (en) * | 2022-05-23 | 2022-10-04 | 佛山市三水佛水供水有限公司 | Molecular imprinting fluorescence sensor based on amphiphilic block copolymer-metal organic framework and preparation method and application thereof |
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