阅读说明：本技术 席夫碱网络聚合物光催化剂及其制备方法和应用 (Schiff base network polymer photocatalyst and preparation method and application thereof ) 是由 曾光明 王晗 许飘 刘洋 程敏 黄丹莲 杜力 李晓沛 秦蕾 陈军霞 于 2020-12-30 设计创作，主要内容包括：本发明公开了一种席夫碱网络聚合物光催化剂及其制备方法和应用,该光催化剂是以三聚氰胺和邻苯二甲醛为原料,在1,4-二氧六环与均三甲苯混合溶液体系中发生缩聚反应后制备得到。本发明方法制得的席夫碱网络聚合物光催化剂具有比表面积高、反应活性位点多、光吸收范围宽、电子-空穴对复合率低、光催化性能好等优点,能够广泛用于降解有机污染物,且能够取得较好的降解效果,有着很高的使用价值和很好的应用前景；同时,本发明制备方法具有工艺简单、操作方便、原材料易得、成本低廉、制备效率高、产率高等优点,适合于大规模制备,利于工业化生产。(The invention discloses a Schiff base network polymer photocatalyst and a preparation method and application thereof, wherein the photocatalyst is prepared by taking melamine and o-phthalaldehyde as raw materials and carrying out polycondensation reaction in a mixed solution system of 1, 4-dioxane and mesitylene. The Schiff base network polymer photocatalyst prepared by the method has the advantages of high specific surface area, more reactive sites, wide light absorption range, low electron-hole pair recombination rate, good photocatalytic performance and the like, can be widely used for degrading organic pollutants, can obtain better degradation effect, and has very high use value and good application prospect; meanwhile, the preparation method has the advantages of simple process, convenient operation, easily available raw materials, low cost, high preparation efficiency, high yield and the like, is suitable for large-scale preparation, and is beneficial to industrial production.)

1. A preparation method of a Schiff base network polymer photocatalyst is characterized in that melamine and o-phthalaldehyde are used as raw materials, and a polycondensation reaction is carried out in a mixed solution system of 1, 4-dioxane and mesitylene to obtain the Schiff base network polymer photocatalyst.

2. The method of preparing a schiff base network polymer photocatalyst according to claim 1, comprising the steps of: dispersing melamine and o-phthalaldehyde in a mixed solution system of 1, 4-dioxane and mesitylene by ultrasonic, adding glacial acetic acid for polycondensation, washing, and drying in vacuum to obtain the Schiff base network polymer photocatalyst.

3. A method for preparing a schiff base network polymer photocatalyst according to claim 2, wherein the molar ratio of the melamine to the o-phthalaldehyde is 1-3: 2-4; the volume ratio of the 1, 4-dioxane to the mesitylene to the glacial acetic acid is 1: 0.01-0.1; the concentration of the glacial acetic acid is 1M-4M.

4. The preparation method of the Schiff base network polymer photocatalyst according to claim 2 or 3, wherein the ultrasonic dispersion time is 5-30 min; the polycondensation reaction is carried out under vacuum conditions; the temperature of the polycondensation reaction is 100-150 ℃; the time of the polycondensation reaction is 2 to 4 days; washing is to wash the precipitate of the polycondensation reaction by sequentially adopting ethanol, acetone, tetrahydrofuran and ethanol; the drying is carried out under vacuum conditions; the drying temperature is 50-80 ℃; the drying reaction time is 6-12 h.

5. A Schiff base network polymer photocatalyst, which is prepared by the preparation method of any one of claims 1 to 4.

6. Use of the schiff base network polymer photocatalyst of claim 5 in the degradation of organic pollutants in wastewater.

7. Use according to claim 6, characterized in that it comprises the following steps: mixing a Schiff base network polymer photocatalyst with organic pollutant wastewater, stirring, and carrying out photocatalytic reaction in a visible light environment to finish degradation of organic pollutants in the wastewater; the mass ratio of the Schiff base network polymer photocatalyst to the organic pollutants in the organic pollutant wastewater is 50-200: 1.

8. The use according to claim 7, wherein the organic contaminant in the organic contaminant wastewater is an antibiotic; the antibiotic is tetracycline.

9. The use according to claim 7 or 8, wherein the stirring time is 1-2 h; the light source of the visible light is sunlight, a xenon lamp or an LED lamp; the time of the photocatalytic reaction is 60-120 min.

Technical Field

The invention belongs to the technical field of material preparation and environmental catalysis, relates to a preparation method of a Schiff base network polymer photocatalyst, and particularly relates to a Schiff base network polymer photocatalyst taking melamine and o-phthalaldehyde as raw materials, and a preparation method and application thereof.

Background

Over the past few decades, there has been an increasing awareness of the growing environmental concerns. As a major source of environmental pollution, water pollution from industrial organic chemicals and agricultural fertilizers has become an urgent problem to be solved. Persistent organic micropollutants are observed in natural and waste waters, such as pharmaceuticals and personal care products, pesticides and herbicides. The traditional sewage treatment technology is difficult to treat novel pollutants. Photocatalytic technology has proven to be an ideal solution, which can utilize solar energy. In fact, the photocatalytic technology is a technology for catalytic reaction under light irradiation by using a photocatalyst, is generally a reaction among multiple phases, and is a green technology with important application prospects in the fields of energy and environment.

Since 1864 Hugo Schiff's discovery of Schiff base chemistry, this classical reaction has been a common tool in organic synthesis. The Schiff base reaction refers to a reaction that an amine group and an aldehyde group generate imine bonds through condensation, wherein the generated imine bonds can continuously react with the amine group to generate aminal. The formation of kinetically controlled imine bonds helps to build complex molecular structures. Under proper experimental conditions, the double bond of the imine can be attacked by primary amine continuously, so that the aminal is generated through reaction. Schiff base chemistry or dynamic imine chemistry has been widely used for synthesizing microporous polymer materials, mainly because the porous polymer prepared based on the schiff base reaction has high chemical stability and good porosity, and the superiority also enables the organic materials based on the schiff base reaction to be rapidly developed and widely applied. As a complement to inorganic semiconductors, schiff-base conjugated porous organic polymers with semiconductor properties are widely used in photocatalysis. They have great advantages in terms of cost, processability, sustainability and tunable performance. Meanwhile, the synthesis modularization of the compounds provides rich choices for adjusting the porosity, the energy band structure and the interface property of the compounds in photochemical application, and the compounds contain rich aromatic ring and triazine ring structures and are beneficial to forming pi-pi interaction and hydrogen bond interaction sites, and the unique properties enable the compounds to have wide application prospects in the aspect of photocatalysis. However, the existing schiff base network polymers still have the defects of poor photocatalytic activity and even no photocatalytic activity, which limits the application of the schiff base network polymers in photocatalytic degradation of organic pollutants. Therefore, how to obtain a schiff base organic network polymer with a proper energy level, thereby accelerating the charge/electron transfer rate and increasing the photocatalytic rate remains a difficult challenge.

Disclosure of Invention

The invention aims to solve the technical problems in the prior art, provides a Schiff base network polymer photocatalyst which has the advantages of high specific surface area, many reactive sites, wide light absorption range, low electron-hole pair recombination rate and good photocatalytic performance, and also provides a preparation method of the Schiff base network polymer photocatalyst which has the advantages of simple process, wide raw material source, low cost, high preparation efficiency and high yield, and application of the Schiff base network polymer photocatalyst in degrading organic pollutants in waste water.

In order to solve the technical problems, the invention adopts the following technical scheme:

a preparation method of a Schiff base network polymer photocatalyst takes melamine and o-phthalaldehyde as raw materials, and the Schiff base network polymer photocatalyst is obtained by carrying out polycondensation reaction in a mixed solution system of 1, 4-dioxane and mesitylene.

The preparation method of the Schiff base network polymer photocatalyst is further improved, and comprises the following steps: dispersing melamine and o-phthalaldehyde in a mixed solution system of 1, 4-dioxane and mesitylene by ultrasonic, adding glacial acetic acid for polycondensation, washing, and drying in vacuum to obtain the Schiff base network polymer photocatalyst.

In the preparation method of the Schiff base network polymer photocatalyst, the molar ratio of the melamine to the o-phthalaldehyde is further improved to be 1-3: 2-4; the volume ratio of the 1, 4-dioxane to the mesitylene to the glacial acetic acid is 1: 0.01-0.1; the concentration of the glacial acetic acid is 1M-4M.

The preparation method of the Schiff base network polymer photocatalyst is further improved, and the ultrasonic dispersion time is 5-30 min; the polycondensation reaction is carried out under vacuum conditions; the temperature of the polycondensation reaction is 100-150 ℃; the time of the polycondensation reaction is 2 to 4 days; washing is to wash the precipitate of the polycondensation reaction by sequentially adopting ethanol, acetone, tetrahydrofuran and ethanol; the drying is carried out under vacuum conditions; the drying temperature is 50-80 ℃; the drying reaction time is 6-12 h.

As a general technical concept, the invention also provides a Schiff base network polymer photocatalyst prepared by the preparation method.

As a general technical concept, the invention also provides an application of the Schiff base network polymer photocatalyst in degrading organic pollutants in wastewater.

The application is further improved, and comprises the following steps: mixing a Schiff base network polymer photocatalyst with organic pollutant wastewater, stirring, and carrying out photocatalytic reaction in a visible light environment to finish degradation of organic pollutants in the wastewater; the mass ratio of the Schiff base network polymer photocatalyst to the organic pollutants in the organic pollutant wastewater is 50-200: 1.

In the above application, further improvement, the organic pollutant in the organic pollutant wastewater is antibiotic; the antibiotic is tetracycline.

The application is further improved, and the stirring time is 1-2 h; the light source of the visible light is sunlight, a xenon lamp or an LED lamp; the time of the photocatalytic reaction is 60-120 min.

Compared with the prior art, the invention has the advantages that:

(1) the invention provides a Schiff base network polymer photocatalyst which is prepared by taking melamine and o-phthalaldehyde as raw materials and carrying out polycondensation reaction in a mixed solution system of 1, 4-dioxane and mesitylene. In the invention, melamine and o-phthalaldehyde are used as organic network construction units, and are connected through Schiff base imine groups (-C ═ N-) to form a porous framework, wherein the adopted o-phthalaldehyde functional group has small steric hindrance, and the Schiff base network polymer (SNW-o) structure obtained by the reaction has more visible light active centers, can promote the generation of light-excited charge carriers under visible light, thereby degrading target pollutants under visible light, improving the carrier mobility through the extension conjugation of aromatic ring combination, thus, the recombination rate of electron-hole pairs is reduced, the photocatalytic performance of the polymer is improved, and Schiff base network polymers (SNW-p and SNW-m) synthesized by terephthalaldehyde and isophthalaldehyde only absorb light in an ultraviolet region, so that target pollutants cannot be degraded under visible light. The Schiff base network polymer photocatalyst prepared by the invention has a structure similar to carbon nitride, contains abundant aromatic rings and triazine ring structures, has high specific surface area, high nitrogen element content, high chemical stability and abundant active sites, and meanwhile, has a wide light absorption range, visible light response and is beneficial to light absorption; on the other hand, the Schiff base network polymer photocatalyst has intramolecular charge transfer, is beneficial to the effective separation of photo-generated electron-hole pairs, increases the utilization efficiency of the photo-generated electron-hole pairs and promotes the effect of photocatalytic degradation. In addition, the photocatalyst prepared by the invention is nontoxic, has a wide application prospect, and is particularly applicable to the field of photocatalysis. Compared with the conventional Schiff base network polymer, the Schiff base network polymer photocatalyst has the advantages of high specific surface area, more reactive sites, wide light absorption range, low electron-hole pair recombination rate, good photocatalytic performance and the like, can be widely used for degrading organic pollutants, can obtain a good degradation effect, and has high use value and good application prospect.

(2) The invention provides a preparation method of a Schiff base network polymer photocatalyst, which adopts a mixed solution system of 1, 4-dioxane and mesitylene for the first time to carry out catalytic polycondensation reaction by glacial acetic acid to obtain the Schiff base network polymer photocatalyst. Compared with other reaction systems, the 1, 4-dioxane and mesitylene mixed solution system adopted in the invention has the advantages that the preparation method is simpler, the addition amount of the solvent is greatly reduced due to no volatilization loss caused by sealing, and no adverse effect is caused on the environment. Meanwhile, the preparation method has the advantages of simple process, convenient operation, easily available raw materials, low cost, high preparation efficiency, high yield and the like, is suitable for large-scale preparation, and is beneficial to industrial production.

(3) The invention also provides the application of the Schiff base network polymer photocatalyst in degrading organic pollutants in wastewater, the Schiff base network polymer photocatalyst and the organic pollutant wastewater are mixed, stirred and subjected to photocatalytic reaction to realize effective degradation of the organic pollutants, and the Schiff base network polymer photocatalyst has the advantages of simple process, convenience in operation, low cost, high treatment efficiency, good degradation effect and the like, has a good degradation effect on various organic pollutants in a water body, and has a good application prospect.

Drawings

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention.

FIG. 1 is an XRD pattern of a Schiff base network polymer photocatalyst (SNW-o) prepared in example 1 of the present invention.

FIG. 2 is a FT-IR plot of Schiff base network polymer photocatalyst (SNW-o) prepared in example 1 of the present invention.

FIG. 3 is a DRS plot of Schiff base network polymer photocatalysts (SNW-o) prepared in example 1 of the present invention and Schiff base network polymers (SNW-p and SNW-m) prepared in comparative examples 1-2.

FIG. 4 is a TEM image of a Schiff base network polymer photocatalyst (SNW-o) prepared in example 1 of the present invention.

FIG. 5 is an SEM image of a Schiff base network polymer photocatalyst (SNW-o) prepared in example 1 of the present invention.

FIG. 6 is a graph of the time-degradation efficiency of Schiff base network polymer photocatalyst (SNW-o) and Schiff base network polymer (SNW-p and SNW-m) in the case of degrading tetracycline solution under visible light in example 2 of the present invention.

Detailed Description

The invention is further described below with reference to the drawings and specific preferred embodiments of the description, without thereby limiting the scope of protection of the invention.

In the following examples of the present invention, unless otherwise specified, materials and instruments used are commercially available, processes used are conventional, apparatuses used are conventional, and the obtained data are average values of three or more repeated experiments.

Example 1:

a preparation method of a Schiff base network polymer photocatalyst takes melamine and o-phthalaldehyde as raw materials, and the Schiff base network polymer photocatalyst is obtained through a polycondensation reaction, and comprises the following steps:

cleaning and drying a 50mL glass solvent storage bottle, weighing and placing melamine (282.576mg) and o-phthalaldehyde (450.6768mg), weighing and placing 1, 4-dioxane (12mL), 1,3, 5-trimethylbenzene (12mL) and glacial acetic acid (1 mL); vacuumizing, introducing nitrogen gas repeatedly for three times, vacuumizing, and screwing down the bottle stopper; sealing with a sealing film, and reacting in an oil bath at 120 ℃ for three days; after the reaction, cooling the product to room temperature, carrying out suction filtration on the product, sequentially cleaning the product according to ethanol, acetone, tetrahydrofuran and ethanol to obtain a product, placing the product in a vacuum drying oven for drying at 60 ℃ for 8h, taking out the product, grinding and drying the product to obtain the Schiff base network polymer photocatalyst, which is named as SNW-o.

Comparative example 1:

a preparation method of a Schiff base network polymer takes melamine and terephthalaldehyde as raw materials, and the preparation method specifically comprises the following steps:

cleaning and drying a 50mL glass solvent storage bottle, weighing and placing melamine (282.576mg) and terephthalaldehyde (450.6768mg), weighing and placing 1, 4-dioxane (12mL), 1,3, 5-trimethylbenzene (12mL) and glacial acetic acid (1 mL); vacuumizing, introducing nitrogen gas repeatedly for three times, vacuumizing, and screwing down the bottle stopper; sealing with a sealing film, and reacting in an oil bath at 120 ℃ for three days; after the reaction is finished, cooling the product to room temperature, carrying out suction filtration on the product, sequentially cleaning the product according to ethanol, acetone, tetrahydrofuran and ethanol to obtain a product, placing the product in a vacuum drying oven for drying at 60 ℃ for 8h, taking out the product, grinding and drying to obtain the Schiff base network polymer, which is named as SNW-p.

Comparative example 2:

a preparation method of a Schiff base network polymer takes melamine and m-phthalaldehyde as raw materials, and the preparation method specifically comprises the following steps:

cleaning and drying a 50mL glass solvent storage bottle, weighing and placing melamine (282.576mg) and m-phthalaldehyde (450.6768mg), weighing and placing 1, 4-dioxane (12mL), 1,3, 5-trimethylbenzene (12mL) and glacial acetic acid (1 mL); vacuumizing, introducing nitrogen gas repeatedly for three times, vacuumizing, and screwing down the bottle stopper; sealing with a sealing film, and reacting in an oil bath at 120 ℃ for three days; after the reaction is finished, cooling the product to room temperature, carrying out suction filtration on the product, sequentially cleaning the product according to ethanol, acetone, tetrahydrofuran and ethanol to obtain a product, placing the product in a vacuum drying oven for drying at 60 ℃ for 8 hours, taking out the product, grinding and drying to obtain the Schiff base network polymer, wherein the name of the Schiff base network polymer is SNW-m.

FIG. 1 is an X-ray diffraction pattern of a Schiff base network polymer photocatalyst (SNW-o) prepared in example 1 of the present invention. It can be seen from fig. 1 that a bulge peak exists at 25 °, indicating that the prepared schiff base network polymer photocatalyst (SNW-o) is an amorphous structure, and a graphite-like two-dimensional layered structure exists.

FIG. 2 is a FT-IR plot of Schiff base network polymer photocatalyst (SNW-o) prepared in example 1 of the present invention. From FIG. 2, it can be seen that the quadrant (1550 cm) of the triazine ring^-1) And semicircular stretching (1480 cm)^-1) The corresponding distinct bands appear in the spectrum of SNW-o, indicating that melamine successfully incorporated into the SNW-o network. characteristic-C ═ O- (1706 cm)^-1) And aldehyde groups C-H (2819 and 2729 cm)^-1) The tensile band disappeared and the imine (-C ═ N-) stretching vibration band appeared at 1612cm^-1Here, the consumption of aldehyde and the completion of condensation are indicated. .

FIG. 3 is a DRS plot of Schiff base network polymer photocatalysts (SNW-o) prepared in example 1 of the present invention and Schiff base network polymers (SNW-p and SNW-m) prepared in comparative examples 1-2. It can be seen from fig. 3 that the absorption edge of the schiff base network polymer photocatalyst (SNW-o) is significantly red-shifted to about 600nm longer than that of the schiff base network polymers (SNW-p and SNW-m) prepared in the comparative examples 1-2, which enhances the absorption of visible light and improves the utilization rate of sunlight; and Schiff base network polymers (SNW-p and SNW-m) cannot realize the absorption of visible light.

FIG. 4 is a TEM image of a Schiff base network polymer photocatalyst (SNW-o) prepared in example 1 of the present invention. FIG. 5 is an SEM image of a Schiff base network polymer photocatalyst (SNW-o) prepared in example 1 of the present invention. As can be seen from fig. 4 and 5, the schiff base network polymer photocatalyst (SNW-o) has a structure of a blocky thin sheet with a large specific surface area.

Example 2:

an application of a Schiff base network polymer photocatalyst in degrading organic pollutants in waste water, in particular to a method for degrading tetracycline in water by using the Schiff base network polymer photocatalyst, which comprises the following steps:

100mg of the Schiff base network polymer photocatalyst (SNW-o) prepared in example 1 and the Schiff base network polymers (SNW-p and SNW-m) prepared in comparative examples 1-2 are respectively put into a tetracycline solution with the concentration of 20mg/L and 100mL, stirred in a dark environment (darkroom) for 30 minutes to reach adsorption equilibrium, and then put into a visible light source (xenon lamp) for photocatalytic reaction, so that the degradation of organic pollutants in a water body is completed.

In the process of photocatalytic reaction, 4mL of tetracycline solution is taken every 10 minutes, the characteristic peak value of tetracycline in the solution is measured by an ultraviolet-visible spectrophotometer, and the degradation efficiency of different catalysts to the tetracycline solution under different time conditions is calculated.

FIG. 6 is a graph of the time-degradation efficiency of Schiff base network polymer photocatalyst (SNW-o) and Schiff base network polymer (SNW-p and SNW-m) in the case of degrading tetracycline solution under visible light in example 2 of the present invention. As shown in FIG. 6, after 1 hour of light irradiation, the degradation efficiency of the Schiff base network polymers (SNW-p and SNW-m) prepared in comparative examples 1-2 to tetracycline was almost zero, while the degradation efficiency of the Schiff base network polymer photocatalyst (SNW-o) to tetracycline was 80%. The comparison shows that the degradation efficiency of the Schiff base network polymer photocatalyst on organic pollutants is obviously improved, the organic pollutants in water can be effectively removed, and the Schiff base network polymer photocatalyst has better photocatalytic activity.

The results in fig. 1-6 show that the schiff base network polymer photocatalyst prepared by the invention has the advantages of high specific surface area, many reactive active sites, wide light absorption range, low electron-hole pair recombination rate, good photocatalytic performance and the like, can be widely used for degrading organic pollutants, can obtain better degradation effect, and has very high use value and good application prospect.

The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above-described embodiments. All technical schemes belonging to the idea of the invention belong to the protection scope of the invention. It should be noted that modifications and embellishments within the scope of the invention may be made by those skilled in the art without departing from the principle of the invention, and such modifications and embellishments should also be considered as within the scope of the invention.