阅读说明：本技术 一种嘧啶唑共价有机框架的制备方法及吸附应用 (Preparation method and adsorption application of pyrimidazole covalent organic framework ) 是由 邱建丁 张程蓉 梁汝萍 于 2021-09-30 设计创作，主要内容包括：本发明公开了一种嘧啶唑共价有机框架的制备方法及吸附应用,属于环境保护技术领域。本发明以1,3,5-三(3-氟-4-甲酰基苯基)苯、1,3,5-三(4-氰基-4,4-联苯)苯和2-氨基-4-羧基吡啶为原料,构建了一种羧酸官能化的嘧啶唑基共价有机框架制备方法。嘧啶唑基共价有机框架的内孔径略大于铀的直径,可以实现对铀的选择性尺寸匹配吸附,大大降低了质子化效应；同时,嘧啶唑基共价有机框架具有规则的多孔通道和优异的亲水性,可促进铀酰离子的扩散,使其具有高的吸附容量和快速的吸附动力学。本发明方法简单、成本低、制备的材料结构明确且亲水性好,可高效吸附铀酰离子,具有良好的应用前景。(The invention discloses a preparation method and adsorption application of a pyrimidazole covalent organic framework, and belongs to the technical field of environmental protection. The invention takes 1,3, 5-tri (3-fluoro-4-formylphenyl) benzene, 1,3, 5-tri (4-cyano-4, 4-biphenyl) benzene and 2-amino-4-carboxypyridine as raw materials to construct a preparation method of a carboxylic acid functionalized pyrimidinyloxy covalent organic framework. The internal pore diameter of the pyrimidine-based covalent organic framework is slightly larger than the diameter of uranium, so that selective size matching adsorption of uranium can be realized, and the protonation effect is greatly reduced; meanwhile, the pyrimidine-based covalent organic framework has a regular porous channel and excellent hydrophilicity, and can promote diffusion of uranyl ions, so that the uranyl ions have high adsorption capacity and rapid adsorption kinetics. The method is simple, low in cost, clear in prepared material structure and good in hydrophilicity, can efficiently adsorb uranyl ions, and has a good application prospect.)

1. A preparation method of a pyrimidazole covalent organic framework is characterized by comprising the following steps:

1) adding 1,3, 5-tri (3-fluoro-4-formylphenyl) benzene, 1,3, 5-tri (4-cyano-4, 4-biphenyl) benzene and 2-amino-4-carboxypyridine into a reaction container, adding a catalyst and an organic solvent, performing ultrasonic treatment on the mixed solution, and uniformly mixing to obtain a reaction mixed solution;

2) carrying out freezing-pumping-unfreezing cycle degassing and flame sealing on a reaction container filled with the reaction mixed solution, placing the reaction container in an environment with the temperature of 120 ℃ for reaction for 4-6 days, and cooling the reaction container to room temperature to obtain a reaction product;

3) and (3) separating a precipitate from the reaction product by vacuum filtration, washing the precipitate with ethanol, draining the precipitate to obtain a solid, and drying the solid at 80 ℃ in vacuum for 12 hours to prepare the carboxylic acid functionalized pyrimidineazole covalent organic framework.

2. The method for preparing a pyrimidazole covalent organic framework as claimed in claim 1, wherein the molar ratio of 1,3, 5-tris (3-fluoro-4-formylphenyl) benzene, 1,3, 5-tris (4-cyano-4, 4-biphenyl) benzene and 2-amino-4-carboxypyridine in step 1) is 1: (0.5-2.0): (2.5-4.0).

3. The method for preparing the pyrimidine azole covalent organic framework according to claim 1, wherein the catalyst in step 1) is p-toluenesulfonic acid.

4. The method for preparing a pyrimidazole covalent organic framework according to claim 1, wherein the organic solvent in step 1) is one or more of ethanol, mesitylene, o-dichlorobenzene and dichloromethane.

5. Use of a covalent organic framework of pyrimidinazoles prepared according to any of claims 1 to 4 for the adsorption of uranyl ions.

6. The application of the covalent organic framework of pyrimidazole in adsorption of uranyl ions according to claim 5, wherein the method comprises the steps of adding the covalent organic framework of pyrimidazole to aqueous solutions containing different concentrations of uranyl ions, shaking for 12 hours by using a constant-temperature oscillator, filtering by using a 0.22-micrometer microporous filter membrane, collecting filtrate, measuring the content of residual uranyl ions in the filtrate by using inductively coupled plasma mass spectrometry, and calculating the adsorption capacity of the covalent organic framework of pyrimidazole on uranyl ions.

7. The use of the covalent organic framework of pyrimidazoles for the adsorption of uranyl ions according to claim 6, wherein the concentration of the aqueous solution of different concentrations of uranyl ions is in the range of 0-500 mg/L.

8. Use of the covalent organic framework of pyrimidiniazoles for the adsorption of uranyl ions according to claim 6, characterized in that the pH of the solution is adjusted with nitric acid or sodium hydroxide solution to 2.0-6.0, more preferably 5.0, before the mixing of the aqueous solution containing different concentrations of uranyl ions with the covalent organic framework of pyrimidiniazoles.

9. Use of the covalent organic framework of pyrimidazoles according to claim 6 for the adsorption of uranyl ions, characterized in that the adsorption capacity is calculated by the following formula: q. q.s_t＝(C_o-C_t) M × V; wherein V is the volume of the solution, unit L, m is the amount of covalent organic framework used, unit g, C_oIs the initial concentration of uranyl ions and the unit mg/L, C_tIs the equilibrium concentration of uranyl ions and the unit mg/L.

Technical Field

The invention relates to the technical field of environmental protection, in particular to a preparation method and adsorption application of a pyrimidazole covalent organic framework.

Background

Along with the rapid development of nuclear power, the spent fuel generated by the nuclear power station is continuously accumulated, and the spent fuel contains a large amount of fissile nuclides (A), (B)²³⁵Uranium and²³⁹plutonium, etc.) and convertible nuclides (mainly plutonium, etc.)²³⁸Uranium), which is a valuable nuclear resource, wherein uranium is a key element in nuclear fuel, but is also a highly toxic and radioactive environmental pollutant. Due to widespread use of nuclear power, large-scale uranium mining, nuclear accidents, and improper disposal of nuclear waste, large quantities of radioactive uranium permeate the environment primarily in the form of uranyl ions (Xiao, f.et al, Smart sonic crystalline hydrogel material for uranyl monitoring and removal in water, adv.funct.mater.2017,27,1702147). Therefore, a stable and efficient uranium adsorbent is of great importance for environmental protection and social development. Porous materials, such as Porous Organic Polymers (POPs) (Xu, M.et al, high throughput connected microporus polymers for current acquisition and detection of uranium, J.Mater.chem.A.2019,7,11214), Metal Organic Frameworks (MOFs) (Liu, W.et al, high throughput connected and selective urea acquisition in raw water systems using a luminescence detection agent, and any other suitable adsorbent material may be used as the adsorbent for uranium (U.S.A.A.. However, the performance of amorphous POPs is affected by irregular pores, most of which are buried (Aguila, b.et al, effective polymer capture using functional polymer. adv.mater.2017,29,1700665), hindering rapid mass transfer. Despite their regular porosity and good crystal structure, stability under extreme conditions (acid, base, temperature and radiation) remains a challenge (Xu, l.et al, Nano-MOF technique for influencing urea metabolism, ACS appl.mater.interfaces.2019,11,21619). High stability is particularly important for extracting uranyl ions, so that development of a uranyl ion adsorbing material with high adsorption capacity, good selectivity and stability is very important.

Covalent organic framework materials (COFs) are an emerging class of porous crystalline materials connected by covalent bonds (p.j.waller, f.gandara and o.m.yaghi, Acc, Chemistry of covalent organic frameworks, chem.res.2015,48,3053). COFs are considered to adsorb uranium due to their regular porosity, large specific surface area and excellent stabilityExcellent candidate material for the same. Although good progress has been made in the research of adsorbents based on amidoxime COFs, vanadium has a greater affinity for amidoximes than uranium and, during post-amidoxime modification, reduces the crystallinity and porosity of COFs (w. -r.cui, c. -r.zhang, w.jiang, f. -f.li, r. -p.liang, j.liu, j. -d.qiu, Regenerable and stable²carbon-conjugated scientific frames for selective detection and extraction of uranium, nat. Commun.2020,11,436). Therefore, a proper design thought and a construction method are found to solve the problems faced by the current amidoxime group COFs, and the method is an important breakthrough point of applying the COFs material to uranium adsorption research.

Disclosure of Invention

The invention aims to provide a preparation method of a pyrimidine azole covalent organic framework with a unique pore structure and an application of the pyrimidine azole covalent organic framework in adsorption of uranyl ions. The carboxylic acid functionalized pyrimidinyloxy covalent organic frameworks are prepared by using 1,3, 5-tris (3-fluoro-4-formylphenyl) benzene, 1,3, 5-tris (4-cyano-4, 4-biphenyl) benzene and 2-amino-4-carboxypyridine as raw materials. The carboxyl groups on the carboxylic acid functionalized pyrimidinyloxy covalent organic frameworks can coordinate with uranyl ions; the unique inner hole structure of the pyrimidine-based covalent organic framework is beneficial to size matching of uranyl ions, selective size matching adsorption of the uranyl ions can be realized, and adsorption selectivity of the uranyl ions is improved; the pyrimidyl covalent organic framework has regular porous channels and excellent hydrophilicity, and can promote diffusion of uranyl ions, so that the pyrimidyl covalent organic framework has high adsorption capacity and rapid adsorption kinetics. The method not only can provide a new idea for the design and regulation of the microstructure of the adsorption material, but also provides a new way for preparing the high-efficiency uranium adsorbent. At present, no report on the synthesis of a carboxylic acid functionalized pyrimidine azole covalent organic framework and the adsorption of uranyl ions is found.

The invention is realized by the following technical scheme:

a preparation method of a pyrimidazole covalent organic framework comprises the following steps: the preparation method adopts a one-pot method strategy under solvothermal conditions to prepare the carboxylic acid functionalized pyrimidazole covalent organic framework, takes 1,3, 5-tri (3-fluoro-4-formylphenyl) benzene, 1,3, 5-tri (4-cyano-4, 4-biphenyl) benzene and 2-amino-4-carboxypyridine as raw materials, and reacts under certain conditions to form the carboxylic acid functionalized pyrimidazole covalent organic framework, and comprises the following specific steps:

1) adding 1,3, 5-tri (3-fluoro-4-formylphenyl) benzene, 1,3, 5-tri (4-cyano-4, 4-biphenyl) benzene and 2-amino-4-carboxypyridine into a reaction container, adding a catalyst and an organic solvent, performing ultrasonic treatment on the mixed solution, and uniformly mixing to obtain a reaction mixed solution;

2) degassing a reaction container filled with reaction mixed liquid through three times of freezing-pumping-unfreezing circulation, sealing flame, placing the reaction container in an environment with the temperature of 120 ℃ for reaction for 4 to 6 days, and cooling the reaction container to room temperature to obtain a reaction product;

3) and (3) separating a precipitate from the reaction product by vacuum filtration, washing the precipitate with ethanol, draining the precipitate to obtain a solid, and drying the solid at 80 ℃ in vacuum for 12 hours to prepare the carboxylic acid functionalized pyrimidineazole covalent organic framework.

Preferably, the molar ratio of 1,3, 5-tris (3-fluoro-4-formylphenyl) benzene, 1,3, 5-tris (4-cyano-4, 4-biphenyl) benzene and 2-amino-4-carboxypyridine in step 1) is 1: (0.5-2.0): (2.5-4.0).

Preferably, the catalyst in step 1) is p-toluenesulfonic acid.

Preferably, the organic solvent in the step 1) is one or more of ethanol, mesitylene, o-dichlorobenzene and dichloromethane.

The invention also provides application of the pyrimidazole covalent organic framework in adsorption of uranyl ions, which comprises the steps of adding the pyrimidazole covalent organic framework into aqueous solutions containing different concentrations of uranyl ions, oscillating for 12 hours by using a constant-temperature oscillator, filtering by using a 0.22-micrometer microporous filter membrane, collecting filtrate, measuring the content of residual uranyl ions in the filtrate by using inductively coupled plasma mass spectrometry, and calculating the adsorption capacity of the pyrimidazole covalent organic framework on the uranyl ions.

Preferably, the concentration range of the aqueous solution of the uranyl ions with different concentrations is 0-500 mg/L.

Preferably, the pH of the aqueous solution containing different concentrations of uranyl ions is adjusted to 2.0 to 6.0, more preferably 5.0, with nitric acid or sodium hydroxide solution before mixing with the covalent organic framework of pyrimidazole.

Preferably, the adsorption capacity is calculated by the following formula: q. q.s_t＝(C_o-C_t) M × V; wherein V is the volume of the solution, unit L, m is the amount of covalent organic framework used, unit g, C_oIs the initial concentration of uranyl ions and the unit mg/L, C_tIs the equilibrium concentration of uranyl ions and the unit mg/L.

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

(1) the carboxylic acid functionalized pyrimidazole covalent organic framework is synthesized by a solvothermal one-pot method, and the method has the advantages of simplicity, low cost, strong stability and good hydrophilicity.

(2) Carboxyl on the pyrimidine azole covalent organic framework prepared by the invention can coordinate with uranyl ions, and selective combination of the uranyl ions is facilitated.

(3) The pyrimidine azole covalent organic framework prepared by the invention can form a unique carboxylic acid functionalized nano pocket structure, and is beneficial to selectively combining uranyl ions.

(4) The internal aperture of the pyrimidine azole covalent organic framework nano pocket prepared by the invention is slightly larger than the diameter of the uranyl hydrate ion, and the size matching adsorption of the uranyl hydrate ion can be realized, so that the protonation effect is greatly reduced, and the selective adsorption performance of the uranyl hydrate ion is improved.

(5) The pyrimidine azole-based covalent organic framework prepared by the invention has regular porous channels and excellent hydrophilicity, can promote diffusion of uranyl ions, has high adsorption capacity and rapid adsorption kinetics, and has good application prospects.

Drawings

FIG. 1 is a schematic diagram of the synthetic route of FP-TZ-AAC.

FIG. 2 is a Fourier transform Infrared Spectroscopy (FT-IR) plot of FP, TZ, AAC and FP-TZ-AAC.

FIG. 3 shows PXRD patterns of FP, TZ, AAC and FP-TZ-AAC measured in experiments.

FIG. 4 is a graph showing adsorption capacities of FP-TZ-AAC for uranyl ions at different pH values.

FIG. 5 is an adsorption isotherm diagram of uranyl ions by FP-TZ-AAC.

Detailed Description

The technical solution of the present invention will be described clearly and completely with reference to the following examples, which are only a part of the examples of the present invention, but not all of them, which are conventional processes unless otherwise specified, and the raw materials which are commercially available from the public unless otherwise specified. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making creative efforts, fall within the protection scope of the present invention.

Example 1: preparation and characterization of pyrimidazole covalent organic frameworks

1,3, 5-tris (3-fluoro-4-formylphenyl) benzene (Fp) (22.3mg, 0.05mmol), 1,3, 5-tris (4-cyano-4, 4-biphenyl) benzene (TZ) (17.6mg, 0.046mmol), 2-amino-4-carboxypyridine (AAC) (24.9mg, 0.180mmol) and p-toluenesulfonic acid (7.0mg, 0.037mmol) were added to a Pyrex tube, ethanol (0.1mL) and mesitylene (0.3mL) were added, the mixture was sonicated for 10 minutes to mix well, degassed by three freeze-pump-thaw cycles, the Pyrex tube was flame sealed and placed in an oven at 120 ℃ for 5 days, cooled to room temperature, the reaction product was isolated by vacuum filtration as a precipitate and washed three times with ethanol to afford a solid, the resulting solid was vacuum dried at 80 ℃ for 12 hours, a pyrimidazole covalent organic framework (FP-TZ-AAC) was prepared.

FIG. 1 is a schematic diagram of the synthetic route of FP-TZ-AAC.

FIG. 2 is a Fourier transform Infrared Spectroscopy (FT-IR) plot of FP, TZ, AAC and FP-TZ-AAC. From FIG. 2, it was found that FP-TZ-AAC was 1615cm in FT-IR comparison with FP, TZ, AAC and FP-TZ-AAC^-1A new absorption band appears, corresponding to C ═ N stretching vibration of the pyrimidazole ring, indicating successful preparation of the pyrimidazole covalent organic framework FP-TZ-AAC with carboxylic acid functional group as linking unit.

The crystallinity of FP-TZ-AAC is characterized by X-ray powder diffraction Pattern (PXRD). FIG. 3 is the experimentally measured PXRD spectra of FP, TZ, AAC and FP-TZ-AAC. As can be seen from FIG. 3, a strong diffraction peak appears at 3.4 ℃ in FP-TZ-AAC, and the diffraction peaks of the monomers FP, TZ and AAC disappear, which indicates that the pyrimidine azole covalent organic framework FP-TZ-AAC with high crystallinity is successfully synthesized by the method.

Example 2: optimization of the Experimental conditions

The pH value has an effect on the basic morphology of uranium and the extraction capacity of the adsorbent, and therefore the effect of pH on the performance of the adsorbent was investigated. Adjusting the pH value of the aqueous solution to be within the range of 2.0-6.0 by using nitric acid or sodium hydroxide solution, adding 4mg of FP-TZ-AAC into 20mL of uranyl ion aqueous solution with the concentration of 500mg/L, oscillating for 12 hours by using a constant-temperature oscillator, filtering by using a 0.22 mu m microporous filter membrane, collecting filtrate, measuring the content of residual uranyl ions in the filtrate by using inductive coupling plasma mass spectrometry, and calculating the adsorption capacity of FP-TZ-AAC on the uranyl ions.

FIG. 4 is a graph of adsorption capacity of FP-TZ-AAC for uranyl ions at different pH. As can be seen from FIG. 4, the adsorption capacity of FP-TZ-AAC for uranyl ions gradually increases with the increase of pH, and the maximum adsorption capacity of FP-TZ-AAC for uranyl ions is 644mg/g at pH 5.0. The pH value influences the basic existing form of uranium, and when the pH value is more than 5.0, uranyl ions can form precipitates in an aqueous solution, so that the adsorption quantity is reduced. Therefore, the pH of 5.0 was selected as the optimum pH.

Example 3: adsorption application of covalent organic framework of pyrimidazole to uranyl ions

The influence of adsorption performance of the initial concentration FP-TZ-AAC of uranyl ions is researched. Adjusting the pH value of the aqueous solution to 5.0 by using nitric acid or sodium hydroxide solution, adding 4mg of FP-TZ-AAC into 20mL of aqueous solution containing uranyl ions with different concentrations (0-500mg/L), oscillating for 12 hours by using a constant-temperature oscillator, filtering by using a 0.22 mu m microporous filter membrane, collecting filtrate, measuring the content of the residual uranyl ions in the filtrate by using inductive coupling plasma mass spectrometry, calculating the adsorption capacity of the FP-TZ-AAC on the uranyl ions, and drawing an adsorption isotherm of the FP-TZ-AAC on the uranyl ions.

FIG. 5 is an adsorption isotherm diagram of uranyl ions by FP-TZ-AAC. As can be seen from fig. 5, due to the large driving force of the concentration gradient, the adsorption capacity of FP-TZ-AAC for uranyl ions increases rapidly with increasing concentration of uranyl ions until an equilibrium state is reached. Fitting finds that the isothermal adsorption process accords with a Langmuir model, and shows that the adsorption of the FP-TZ-AAC on the uranyl ions is single-layer adsorption, and the maximum adsorption capacity of the FP-TZ-AAC on the uranyl ions is 644 mg/g. The high adsorption capacity can be attributed to the fact that FP-TZ-AAC has regular porous channels and excellent hydrophilicity, and diffusion of uranyl ions is promoted.

The carboxylic acid functionalized pyrimidazole covalent organic framework synthesized by the solvothermal one-pot method has the advantages of high crystallinity, strong stability and good hydrophilicity. FP-TZ-AAC can form a unique carboxylic acid functionalized nano pocket structure, and carboxyl can coordinate with uranyl ions, so that selective combination of the uranyl ions is facilitated. Meanwhile, the inner aperture of the FP-TZ-AAC nano pocket is slightly larger than the diameter of the uranyl hydrate ions, so that size matching adsorption of the uranyl hydrate ions can be realized, and selective adsorption performance of the uranyl hydrate ions is improved. The FP-TZ-AAC has a regular porous channel and excellent hydrophilicity, can promote the diffusion of uranyl ions, has high adsorption capacity and rapid adsorption kinetics, and has good application prospect.

The foregoing is only a preferred embodiment of the present invention and it should be noted that modifications and adaptations can be made by those skilled in the art without departing from the principle of the present invention and are intended to be included within the scope of the present invention.