Preparation method of covalent / organic framework composite material for enriching triazine ultraviolet light absorber

Abstract

The invention discloses a preparation method of a covalent / organic framework composite material for enriching triazine ultraviolet absorbers, and belongs to the field of environmental pollutant enrichment. The preparation method comprises the following steps: synthesizing MOF (MIL-68) through a solvothermal method; and then synthesizing COF (TpBD) on the surface of the MIL-68 through a heating reflux method and an amine-aldehyde condensation method. Based on a multi-benzene ring structure of MIL-68 and TpBD, both MIL-68 and TpBD can generate pi-pi interaction with a triazine ultraviolet light absorber. The unsaturated metal center of the MIL-68 can adsorb a target object through hydrogen-bond interaction, the MIL-68 is bonded with TpBD, the enrichment capacity of the composite material after bonding is greatly enhanced, and the composite material shows high extraction efficiency on the target object. The covalent / metal organic framework material is simple to prepare and has excellent binding capacity and reusability, and the triazine ultraviolet light absorber is high in enrichment efficiency, excellent in sensitivity, good in reusability and excellent in enrichment capacity.

Description

Technical Field

[0001] The invention belongs to the field of environmental pollutants, and in particular relates to the preparation and application of a covalent / organic skeleton composite material enriched with triazine ultraviolet absorbers. Background Art

[0002] Triazine UV absorbers are a new type of UV absorber that is widely added to plastic products to improve the light stability of plastics. Since triazine UV absorbers are not chemically bonded to the polymers in plastic products, but are bonded through very weak physical effects, triazine UV absorbers can easily migrate from plastic products into the daily environment. Triazine UV absorbers have a high octanol-water partition coefficient and can accumulate in organisms through the food chain and then migrate into the human body, which may affect the human reproductive system and be toxic to the liver and kidneys, causing serious harm to human health. Since the concentration of triazine UV absorbers in environmental samples is very small, it is of great significance to study and establish a method for efficiently enriching triazine UV absorbers.

[0003] At present, the separation and enrichment methods of triazine UV absorbers mainly include solid phase extraction (SPE) and liquid-liquid extraction (LLE). As a fast and simple sample pretreatment technology, solid phase extraction technology can achieve the enrichment of analytes and improve the accuracy of analytical detection. In addition, suitable solid phase extraction materials can improve the sensitivity and selectivity of the method. Metal organic frameworks (MOFs) are porous one-, two- or three-dimensional structures formed by metal ions or metal clusters coordinated with organic ligands. MOFs have excellent properties such as large pore volume, large specific surface area, and adjustable structure, making it widely used in different fields such as separation science, gas storage, catalysis, and medical treatment. However, due to the small enrichment capacity and weak chemical stability of MOFs, we proposed a hybrid framework composed of one MOF and another adjustable structure, such as covalent / metal organic framework composites. Compared with single MOFs or COFs, metal organic framework / covalent organic framework (MOF / COF) composites show excellent performance due to the synergistic effect of their different components. At present, the commonly used detection methods for ultraviolet absorbers are high performance liquid chromatography (HPLC), liquid chromatography tandem mass spectrometry (LC-MS), gas chromatography (GC), and gas chromatography tandem mass spectrometry (GC-MS). Compared with gas chromatography, HPLC is not limited by the volatility and thermal stability of the sample, has a variety of mobile phases, and can generally be analyzed at room temperature. In addition, it has the advantages of high separation efficiency, good selectivity, high detection sensitivity, automated operation, and a wide range of applications. Therefore, efficient enrichment of triazine ultraviolet absorbers can be achieved by synthesizing covalent metal organic framework composite solid phase extraction and combining it with high performance liquid chromatography. Summary of the invention

[0004] The purpose of the present invention is to prepare a method for a covalent / metal organic framework composite material for enriching triazine ultraviolet absorbers, so as to achieve rapid and efficient enrichment and separation of triazine ultraviolet absorbers. The material has strong stability, and compared with a single covalent organic framework or metal organic framework, it has a larger enrichment capacity and higher extraction efficiency. The covalent / metal organic framework composite material of the present invention is simple to prepare, has mild conditions, has high enrichment efficiency for triazine ultraviolet absorbers, has good reusability, and is easy to separate from the reaction system.

[0005] The invention first synthesizes MIL-68 by a solvent thermal method; then synthesizes TpBD@MIL-68 by an amine aldehyde condensation method to obtain a covalent / metal organic framework composite material with a multi-benzene ring structure.

[0006] In order to achieve the above object, the present invention is implemented according to the following technical solutions:

[0007] A method for preparing a covalent / metal organic framework composite material for enriching a triazine ultraviolet absorber, characterized by comprising the following steps:

[0008] (1) Weigh 0.945g of hydrated indium nitrate into a 100mL beaker, add 45ml of N,N-dimethylformamide (DMF), and sonicate until dissolved. Then weigh 0.405g of 2-aminoterephthalic acid and 0.081g of benzoic acid into another 100mL beaker, add 360μl of pyridine and 67.5ml of DMF, and sonicate until dissolved. Mix the solutions in the two beakers and dispense them into a reactor, and react in an oven at 125℃ for 2.5h. After the reaction is completed, centrifuge at 11000rmp for 5min at room temperature and discard the upper solution. Wash with anhydrous ethanol 4 times, sonicate for 5min each time. Finally, dry the obtained yellow MIL-68 in a vacuum oven at 60℃ overnight.

[0009] (2) Weigh 0.072g MIL-68 and 0.168g 2,4,6-triformylpyrogallol (Tp) in a three-necked flask, add 60mL 1,4-dioxane, and sonicate until dissolved. Weigh 0.156g benzidine (BD) in a centrifuge tube, add 20mL 1,4-dioxane, and sonicate until dissolved. Place the three-necked flask in an oil bath for mechanical stirring. When heated to 120°C, add the solution in the centrifuge tube dropwise, and continue mechanical stirring at this temperature for 12h to obtain TpBD@MIL-68. Cool to room temperature, wash the product with DMF and anhydrous ethanol 5 times and 2 times, respectively, and then dry it in a vacuum oven at 60°C for 5 hours.

[0010] Furthermore, the prepared TpBD@MIL-68 is a porous organic material with benzene rings, which has a large specific surface area and more binding sites, and has a good enrichment efficiency;

[0011] Furthermore, the TpBD@MIL-68 has good reusability and is easy to separate from the reaction system;

[0012] Furthermore, the TpBD@MIL-68 composite material can not only be used for the detection of environmental pollutants such as triazine ultraviolet absorbers in environmental samples, but also can broaden its application in sample pretreatment, environmental analysis and other fields.

[0013] The advantages of the present invention are:

[0014] (1) The material relies on the benzene rings of MIL-68 and TpBD to interact with triazine UV absorbers and adsorb triazine UV absorbers. This method has mild reaction conditions, high sensitivity and fast extraction efficiency when enriching triazine UV absorbers.

[0015] (2) This material is combined with solid phase extraction technology and high performance liquid chromatography to establish a detection method for triazine ultraviolet absorbers with high sensitivity and low detection limit.

[0016] (4) Compared with other triazine ultraviolet absorber enrichment materials, the covalent / metal organic framework composite material prepared by the present invention has a higher extraction rate and is easy to separate from the reaction system.

[0017] (5) The present invention can be successfully applied to the enrichment and identification of triazine ultraviolet absorbers in plastic films. It can also be widely used in the enrichment of triazine ultraviolet absorbers in different matrices and is a universal enrichment material. DETAILED DESCRIPTION

[0018] The present invention is described in detail below in conjunction with embodiments, but is not intended to limit the present invention.

[0019] Implementation example: Using covalent / metal organic framework composite materials to enrich triazine ultraviolet absorbers in white degradable plastic greenhouse films, black degradable plastic greenhouse films, and yellow soil and black soil in contact with degradable plastics

[0020] (1) Preparation process of covalent / metal-organic framework composites

[0021] (a) Weigh 0.945g of hydrated indium nitrate in a 100mL beaker, add 45mL of N,N-dimethylformamide (DMF), and sonicate until dissolved. Then weigh 0.405g of 2-aminoterephthalic acid and 0.081g of benzoic acid in another 100mL beaker, add 360μL of pyridine and 67.5mL of DMF, and sonicate until dissolved. Mix the solutions in the two beakers and dispense them into a reactor, and react in an oven at 125℃ for 2.5h. After the reaction is completed, centrifuge at 11000rmp for 5min at room temperature, and discard the upper solution. Wash with anhydrous ethanol 4 times, sonicate for 5min each time. Finally, the obtained yellow MIL-68 is dried in a vacuum oven at 60℃ overnight.

[0022] (b) Weigh 0.072g MIL-68 and 0.168g 2,4,6-triformylpyrogallol (Tp) in a three-necked flask, add 60mL 1,4-dioxane, and sonicate until dissolved. Weigh 0.156g benzidine (BD) in a centrifuge tube, add 20mL 1,4-dioxane, and sonicate until dissolved. The three-necked flask is placed in an oil bath for mechanical stirring. When heated to 120°C, the solution in the centrifuge tube is added dropwise, and mechanical stirring is continued at this temperature for 12h to obtain TpBD@MIL-68. The product is cooled to room temperature, and washed twice with DMF and twice with anhydrous ethanol, respectively, and then dried in a vacuum oven at 60°C for 5 hours.

[0023] (2) Sample solution preparation process: Preparation of degradable plastic greenhouse film samples. Cut the degradable plastic greenhouse film into pieces, weigh 1g, soak it in 50mL methanol for 1h, let it stand and soak for 4h, centrifuge it for 5min at a speed of 10000rpm, and separate the supernatant from the lower sediment after centrifugation. Keep the supernatant and filter it with 0.45μm and 0.22μm filter membranes. The filtrate is the sample solution of the degradable plastic greenhouse film. Preparation of soil samples in contact with degradable plastics: Weigh 1g of soil and soak it in 50mL of methanol for 1h, then soak it for 4h, centrifuge it at room temperature for 5min at a speed of 10000rpm, and separate the supernatant from the lower sediment after centrifugation. Keep the supernatant and filter it with 0.45μm and 0.22μm filter membranes. The filtrate is the soil sample solution.

[0024] (a) Preparation of standard solution: Weigh 1 mg of each of the six triazine UV absorbers (Appolo-116, DBDT, TPTZ, 2,4,6-trip-tolyl-1,3,5-triazine, UV-1577, and UV-1164), divide them into six 5 mL centrifuge tubes, add 2 mL of methanol, and dissolve them by ultrasonic. Transfer them to six 10 mL volumetric flasks, adjust the volume, and obtain a 100 μg / mL standard solution. Dilute the 100 μg / mL standard solution step by step to finally obtain a standard solution with a concentration of 1 μg / mL for the six triazine UV absorbers.

[0025] (3) Solid phase extraction process

[0026] (a) First, pipette 0 mL, 1 mL, 5 mL, and 10 mL of a standard solution with a target concentration of 1 μg / mL, dilute it with 100 mL, 99 mL, 95 mL, and 90 mL of sample solution, and prepare spiked sample solutions with concentrations of 0, 10, 50, and 100 μg / L. Add 30 mg of TpBD@MIL-68 composite material to 1 mL of sample solution. Vortex the mixture for 15 min, centrifuge it at 12,000 rpm for 5 min, and carefully aspirate the supernatant with a rubber-tipped pipette. Add 1 mL of ethyl acetate to the remaining material, centrifuge it at 12,000 rpm for 5 min, and transfer the supernatant to an empty centrifuge tube. Add 1 mL of ethyl acetate to the remaining material, centrifuge it at 12,000 rpm for 5 min, and mix the supernatant with the previous supernatant. Concentrate it to dryness with nitrogen blow, and add 1 ml of methanol to reconstitute it.

[0027] (4) The applicability of the established SPE-HPLC method to biodegradable plastic greenhouse films and soil samples in contact with biodegradable plastics was evaluated, and the contents of six triazine ultraviolet absorbers in the samples were analyzed using TpBD@MIL-68 composite materials. The designed method was used to process, extract and detect four actual samples. Three triazine UV absorbers were detected in the original white degradable plastic greenhouse film samples, namely Appolo-116, TPTZ, and UV-1577. The detected contents were 2.14μg / L, 1.94μg / L, and 3.37μg / L, respectively. The recovery rates were all above 80%, and the relative standard deviations were all below 7%. The mixed standard solution containing Appolo-116, DBDT, TPTZ, 2,4,6-trip-tolyl-1,3,5-triazine, UV-1577, and UV-1164 was added to the actual sample to prepare spiked samples with concentrations of 10μg / L, 50μg / L, and 100μg / L, respectively, and solid phase extraction and high performance liquid chromatography were performed. The results of the spike recovery experiment showed that the spiked recovery rates of the six triazine UV absorbers were in the range of 80.90% to 1018.90%, and the RSDs were all less than 7%. Three triazine UV absorbers were detected in the original black degradable plastic greenhouse film samples, namely Appolo-116, TPTZ, and 2,4,6-trip-tolyl-1,3,5-triazine. The detected contents were 14.56μg / L, 2.04μg / L, and 8.37μg / L, respectively. The recovery rates were all above 90%, and the relative standard deviations were all below 7%. The mixed standard solution containing the six triazine UV absorbers was added to the actual sample, and the spiked samples with concentrations of 10μg / L, 50μg / L, and 100μg / L were prepared, respectively, for solid phase extraction and high performance liquid chromatography detection. The results of the spiked recovery experiment showed that the spiked recovery rates of the six triazine UV absorbers were as low as 96.40% and as high as 109.90%, and the RSDs were all less than 7%. Three triazine UV absorbers were detected in the yellow soil samples that were in contact with biodegradable plastics, namely Appolo-116, DBDT, and UV-1577, with the detected contents of 5.52μg / L, 10.20μg / L, and 2.85μg / L, respectively. The mixed standard solution containing the six triazine UV absorbers was added to the actual sample, and the spiked samples with concentrations of 10μg / L, 50μg / L, and 100μg / L were prepared for solid phase extraction and high performance liquid chromatography detection. The results of the spike recovery experiment showed that the spike recovery rates of the six triazine UV absorbers were in the range of 87.60% to 109.90%, and the RSDs were all less than 9%. Three triazine UV absorbers were detected in black soil samples that were in contact with degradable plastics, namely Appolp-116, DBDT, and UV-1577. The detected contents were 2.60μg / L, 1.80μg / L, and 1.30μg / L, respectively. The recovery rates were all above 80%, and the relative standard deviations were all below 7%. A mixed standard solution containing Appolo-116, DBDT, TPTZ, 2,4,6-trip-tolyl-1,3,5-triazine, UV-1577, and UV-1164 was added to the actual sample to prepare spiked samples with concentrations of 10μg / L, 50μg / L, and 100μg / L, respectively, and solid phase extraction and high performance liquid chromatography were performed. The results of the spike recovery experiment showed that the spiked recoveries of the six triazine UV absorbers were all greater than 80%, and the RSDs were all less than 7%. These results indicate that the composite material TpBD@MIL-68 is effective in the extraction analysis of triazines in UV absorbers, and the established SPE-HPLC method is suitable for detecting the residues of triazine UV absorbers in actual samples. These results indicate that the composite material TpBD@MIL-68 is effective in the extraction analysis of triazine UV absorbers, and the established SPE-HPLC method is suitable for detecting the residues of triazine UV absorbers in actual samples.

[0028] (5) Investigation of the reusability of covalent / metal-organic framework composites:

[0029] (a) If the prepared composite material TpBD@MIL-68 has stable mechanical and extractability, then the composite material TpBD@MIL-68 can be recycled and reused after washing and drying. In order to investigate the reusability of the new covalent / metal organic framework composite material TpBD@MIL-68, we used the composite material TpBD@MIL-68 to repeatedly extract the sample solution with a spiked concentration of 1.0μg / mL. After TpBD@MIL-68 was reused 6 times, the extraction rate of the 6 triazine ultraviolet absorbers was still above 70%, proving that the mechanical, physical and chemical properties of the composite material TpBD@MIL-68 we prepared are relatively stable, and the reuse effect is good. It can be widely used in subsequent actual sample applications to achieve the effect of saving resources and protecting the environment.

Claims

1. A method for preparing a covalent / metal organic framework composite material for enriching triazine ultraviolet absorbers, characterized in that: The following steps are involved: (1) Weigh 0.945 g of hydrated indium nitrate and put it into 45 ml DMF and ultrasonicate until it is completely dissolved; weigh 0.405 g of 2-aminoterephthalic acid and 0.081 g of benzoic acid and put them into 360 μL of pyridine and 67.5 ml DMF and ultrasonicate until they are completely dissolved; mix the two and transfer them to a reactor, place them in a high-temperature oven at 125° C. to react for 2.5 hours; after the reaction is completed, wait for the reactor to cool to room temperature, transfer the liquid in the reactor to a centrifuge tube, centrifuge, and discard the upper solution; wash with ethanol; and vacuum dry the obtained MIL-68; (2) Weigh 0.072 g of MIL-68 and 0.168 g of 2,4,6-triformylpyrogallol Tp into 60 ml of 1,4-dioxane and ultrasonicate until completely dissolved; weigh 0.156 g of benzidine BD and ultrasonicate until completely dissolved in 20 ml of 1,4-dioxane; mix the two and reflux at 120°C for 12 h; after the reaction, wash the orange product TpBD@MIL-68 with DMF and ethanol respectively by ultrasonication and then vacuum dry.

2. A method for preparing a covalent / metal organic framework composite material for enriching triazine ultraviolet absorbers according to claim 1, characterized in that: The specific reaction conditions in step (1) are: rotation speed 11000 rpm, centrifugation 5 min; ethanol washing 4 times.

3. The method for preparing a covalent / metal organic framework composite material for enriching triazine ultraviolet absorbers according to claim 1, characterized in that: The specific conditions of the reaction in step (2) are: washing with DMF twice and washing with ethanol twice.