Application of hydrogen bond organic framework combined with ascorbic acid in degradation of organic pollutants

Abstract

The invention belongs to the technical field of organic pollutant removal, and particularly relates to application of hydrogen bond organic framework combined ascorbic acid in degradation of organic pollutants. The invention discloses a photocatalytic system which comprises a hydrogen bond organic framework and ascorbic acid, an organic ligand of the hydrogen bond organic framework is selected from at least one of 1, 3, 6, 8-tetra (4-carboxyl benzene) pyrene, 6, 6 ', 6' ', 6 ''-(pyrene-1, 3, 6, 8-tetrayl) tetra (2-naphthoic acid) or 1, 3, 6, 8-tetra (4-carboxyl phenyl methyl) pyrene, and the photocatalytic system has an excellent degradation effect on organic pollutants and also has relatively good reusability.

Description

Technical Field

[0001] The invention belongs to the technical field of organic pollutant removal, and particularly relates to the application of a hydrogen bond organic framework combined with ascorbic acid in degrading organic pollutants. Background Art

[0002] With the widespread use of plastics around the world, plastic-related water pollution is becoming increasingly serious. Phthalates (PAEs), as common plasticizers, are naturally widely used, such as in building materials, chemical production, food packaging, and medical devices. Because PAEs easily penetrate the surrounding environment, people are easily exposed to PAEs through ingestion, inhalation, and skin absorption, and then PAEs are further involved in human metabolism. PAE metabolites have also been detected in urine samples of people in different countries. More seriously, studies have shown that PAEs, as endocrine disruptors, are harmful to human health. They pose potential risks to humans by causing abnormal hormone secretion, respiratory diseases, birth defects, and even cancer. Therefore, PAEs are listed as key pollutants and people need to find efficient and clean ways to purify them.

[0003] Common methods for removing PAEs include physical and chemical adsorption, advanced oxidation (AOPs) and microbial methods. AOPs is a type of technology that uses strong oxidants to degrade pollutants. Its core is to generate highly reactive free radicals through different reaction systems. These free radicals have extremely high oxidizing power and can destroy the chemical structure of pollutants, ultimately converting them into harmless products such as small molecular compounds or water and carbon dioxide. Common AOPs technologies include: ozone oxidation, hydrogen peroxide oxidation, ultraviolet light / hydrogen peroxide combined oxidation, Fenton reaction, electrochemical oxidation, photocatalytic oxidation, etc.

[0004] Photocatalytic oxidation technology, as an emerging and promising green technology in AOPs, is a good choice worthy of in-depth research. This technology uses light and photocatalysts to generate hole-electron pairs and oxygen-reactive free radicals (ROS) to transform, degrade and mineralize pollutants. However, this technology also has some defects and shortcomings. For example, the size of the energy band gap (Ebg) of the photocatalyst will affect the energy and wavelength of light required to excite electrons from the valence band (VB) to the conduction band (CB), which will limit the choice of light source. On the other hand, the recombination of the generated electrons and holes, the interference of other non-toxic / low-toxic substances coexisting in high concentrations in complex water bodies, and the secondary pollution of photocatalyst materials are also problems that need to be solved.

[0005] Hydrogen-bonded organic frameworks (HOFs) are a class of organic framework materials assembled from organic ligands through hydrogen bonding interactions. Unlike metal-organic frameworks and covalent organic frameworks, the structure of HOFs relies entirely on hydrogen bonding, which makes HOFs more flexible and reduces synthesis costs. Because HOFs are primarily connected by hydrogen bonds, their structure is relatively flexible and can be adjusted to a certain extent during the reaction process.

[0006] HOFs can achieve photoresponse under visible light irradiation and can produce reactive oxygen species (ROS). In addition, HOFs can effectively adsorb some organic matter. Although HOFs have great application potential in photocatalysis, the research on HOFs materials in the field of photocatalytic degradation of pollutants is still in its infancy. Which HOFs materials have better pollutant degradation effects and how to efficiently degrade organic pollutants in water bodies based on HOFs materials have become technical problems that need to be solved urgently. Summary of the Invention

[0007] In response to the current technical problems, the primary purpose of the present invention is to provide a photocatalytic system that has an excellent degradation effect on organic pollutants and has good reusability.

[0008] The second object of the present invention is to provide an application of a photocatalyst in photocatalytic degradation of organic pollutants.

[0009] The third object of the present invention is to provide the use of ascorbic acid in promoting the photocatalytic degradation of organic pollutants by hydrogen-bonded organic frameworks.

[0010] The fourth object of the present invention is to provide a method for degrading organic pollutants in an aquatic environment.

[0011] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0012] The present invention claims protection for a photocatalytic system comprising: a hydrogen-bonded organic framework and ascorbic acid; the organic ligand of the hydrogen-bonded organic framework is selected from at least one of 1,3,6,8-tetrakis(4-carboxyphenyl)pyrene, 6,6',6",6"'-(pyrene-1,3,6,8-tetrayl)tetrakis(2-naphthoic acid) or 1,3,6,8-tetrakis(4-carboxyphenylmethyl)pyrene.

[0013] Hydrogen-bonded organic frameworks (HBOFs) can photoresponsively react to visible light, generating ROS that transform, degrade, and mineralize pollutants, while also generating hole-electron pairs that degrade pollutants. While HBOFs exhibit a high recombination rate of photogenerated carriers upon illumination, these electrons readily recombine with holes, significantly limiting their photocatalytic efficiency.

[0014] Through research, the inventors found that when a specific type of hydrogen-bonded organic framework is used in combination with ascorbic acid, it has an excellent degradation effect on organic pollutants. Ascorbic acid can quench the oxidative free radicals generated during the photocatalytic process, thereby inhibiting the degradation of organic pollutants.

[0015] Through research, the inventors discovered that although ascorbic acid is a commonly used reducing agent, it can significantly improve the photocatalytic activity of specific types of hydrogen-bonded organic frameworks during the photocatalytic degradation of organic pollutants by hydrogen-bonded organic frameworks. The inventors speculate that the strong reducing properties and electron transfer ability of ascorbic acid give it a strong ability to capture photogenerated holes, which enables ascorbic acid to effectively reduce the possibility of electron-hole pair recombination, thereby preventing the transition of photogenerated electrons from easily combining with holes again, and avoiding the decline in the degradation effect of hydrogen-bonded organic frameworks during the photocatalytic process. Other common reducing agents such as EDTA, glucose, ammonium oxalate, etc. are unable to achieve the above-mentioned effects.

[0016] Furthermore, the inventors discovered through research that the type of hydrogen-bonded organic framework will also affect its binding with ascorbic acid and ultimately affect the degradation of organic pollutants. The inventors discovered through research that after a specific hydrogen-bonded organic framework is combined with ascorbic acid, it has an excellent degradation effect on organic pollutants.

[0017] The hydrogen-bonded organic framework material in the present invention has the advantages of high stability, large pore volume, large specific surface area, mild synthesis conditions, etc., and does not contain metal ions, which is extremely advantageous for certain biological applications. The hydrogen-bonded organic framework provided by the present invention has significantly improved resistance to environmental factors. It can adsorb organic pollutants under dark conditions, and can convert and degrade organic pollutants after combining with ascorbic acid under light conditions, significantly increasing the removal efficiency of organic pollutants. In addition, the amount of material added under the same conditions is much lower than that of other reported materials, has extremely high pollutant conversion efficiency, and has good reusability. The photocatalyst provided by the present invention is low-cost and easy to produce, is environmentally friendly, and has extremely high value for practical industrial applications.

[0018] Preferably, the photocatalytic system provided by the present invention comprises two components, namely a hydrogen-bonded organic framework and ascorbic acid. In specific applications, the hydrogen-bonded organic framework and ascorbic acid can be mixed and used; or the hydrogen-bonded organic framework or ascorbic acid can be added to the reaction system in a sequential order.

[0019] Preferably, the mass ratio of the hydrogen-bonding organic framework to ascorbic acid is 0.01-0.20:1-10. Further preferably, the mass ratio of the hydrogen-bonding organic framework to ascorbic acid is 0.02-0.12:1-5. More preferably, the mass ratio of the hydrogen-bonding organic framework to ascorbic acid is 0.04-0.12:2-5.

[0020] Preferably, in some embodiments, the preparation method of the hydrogen-bonded organic framework is: dissolving an organic ligand in N,N-dimethylformamide, then adding an alcohol solvent or a ketone solvent, and mixing them uniformly to obtain the hydrogen-bonded organic framework.

[0021] The present invention uses specific organic ligands as monomers to synthesize hydrogen-bonded organic frameworks, which has simple operation and mild reaction conditions. The organic ligands are dissolved, added with solvents and mixed evenly, and then the hydrogen-bonded organic framework material can be obtained through the self-assembly of the organic ligands.

[0022] Specifically, the alcohol solvent includes but is not limited to methanol, ethanol, etc. Specifically, the ketone solvent includes but is not limited to acetone, etc.

[0023] Specifically, the time for uniform mixing and reaction is 12-24 hours.

[0024] Specifically, the components can be uniformly mixed using conventional methods in the art, such as stirring. More specifically, in some embodiments, the components are uniformly mixed using stirring. More specifically, the stirring speed is 300-1000 rpm; more specifically, the stirring speed is 400-600 rpm.

[0025] Specifically, after the reaction is completed, a post-processing step is further included, wherein the post-processing step comprises: centrifuging the product, collecting the centrifugal precipitate, then adding an alcohol solvent to redissolve it, and re-centrifuging it.

[0026] More specifically, the centrifugal speed is 5000-10000 rpm. More specifically, the centrifugal speed is 8000-9000 rpm. More specifically, the centrifugal time is 5-10 minutes. More specifically, the centrifugal time is 6-8 minutes.

[0027] Specifically, the post-processing is performed 2-4 times.

[0028] Furthermore, the present invention seeks to protect the use of the above-mentioned photocatalytic system in the photocatalytic degradation of organic pollutants.

[0029] Furthermore, the present invention claims protection for the use of ascorbic acid in promoting the photocatalytic degradation of organic pollutants by a hydrogen-bonded organic framework, wherein the organic ligand of the hydrogen-bonded organic framework is selected from at least one of 1,3,6,8-tetrakis(4-carboxyphenyl)pyrene, 6,6',6",6"'-(pyrene-1,3,6,8-tetrayl)tetrakis(2-naphthoic acid) or 1,3,6,8-tetrakis(4-carboxyphenylmethyl)pyrene.

[0030] Preferably, the organic pollutants are selected from one or more of phthalates, phenolic organic pollutants, polybrominated diphenyl ether organic pollutants, and organic dyes.

[0031] More specifically, the phenolic organic pollutants include but are not limited to bisphenol A, etc.; the polybrominated diphenyl ether organic pollutants include but are not limited to tetrabromodiphenyl ether, etc.; the organic dyes include but are not limited to malachite green, etc.

[0032] Preferably, the illumination time of photocatalysis is ≥15 min; and / or the illumination intensity is ≥5 mW / cm 2 More preferably, the illumination time for photocatalysis is 15-60 min; more preferably, the illumination time for photocatalysis is 30-60 min. More preferably, the illumination intensity is 5-15 mW / cm 2 More preferably, the light intensity is 8-10 mW / cm 2 .

[0033] Furthermore, the present invention seeks to protect a method for degrading organic pollutants in an aquatic environment, comprising mixing the above-mentioned photocatalytic system with water containing organic pollutants and treating the water under light conditions.

[0034] Preferably, the pH of the water environment is 1-9. Further preferably, the pH of the water environment is 1-7.

[0035] Preferably, the water system does not contain copper ions.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] (1) The present invention provides a photocatalytic system comprising a specific type of hydrogen-bonded organic framework and ascorbic acid. Ascorbic acid can significantly improve the photocatalytic activity of the specific type of hydrogen-bonded organic framework, thereby avoiding the decrease in the degradation effect of the hydrogen-bonded organic framework during the photocatalytic process.

[0038] (2) The photocatalytic system provided by the present invention has good reusability, can resist the influence of alkaline environment, can be applied to water systems containing most anions and cations, can better resist the interference of natural organic matter in the water environment, and can be used in a variety of actual water environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Schematic diagram of the changes in the adsorption process of the PSO model and the PFO model under different initial DBP concentrations.

[0040] Figure 2 Schematic diagrams describing the interaction between adsorbent and adsorbed molecules at equilibrium for two different adsorption isotherm models.

[0041] Figure 3 Schematic diagram of the changes in DBP concentration in the photocatalytic system and the photocatalytic system eluted with DMF at different times.

[0042] Figure 4 Schematic diagram of the photocatalytic system's resistance to interference from the pH of the aqueous environment.

[0043] Figure 5 Schematic diagram of the photocatalytic system's resistance to anion interference in the aqueous environment.

[0044] Figure 6 Schematic diagram of the photocatalytic system's resistance to cation interference from aqueous environment.

[0045] Figure 7 Schematic diagram of the photocatalyst system's resistance to interference from natural organic matter in the aqueous environment.

[0046] Figure 8 Schematic diagram of the application of photocatalyst system in actual water environment.

[0047] Figure 9 Schematic diagram of the reusability of the photocatalyst system.

[0048] Figure 10 Schematic diagram of DBP removal in different HOF systems.

[0049] Figure 11 Schematic diagram of DBP removal by different reducing agent systems.

[0050] Figure 12 and 13 Schematic diagram of DBP removal with different amounts of HOF or ascorbic acid.

[0051] Figure 14 Schematic diagram of the reaction mechanism of the photocatalytic system. DETAILED DESCRIPTION

[0052] The present invention is further described below with reference to the specification and specific examples, which are not intended to limit the present invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the art.

[0053] Example 1 Construction of photocatalytic system

[0054] (1) Preparation of hydrogen bond organic framework HOF-101: 20 mg of organic ligand 1,3,6,8-tetrakis(4-carboxyphenyl)pyrene (H4TBAPy) was dissolved in 2 mL of N,N-dimethylformamide (DMF) by ultrasonic treatment. 12 mL of methanol was quickly poured into the mixture while stirring. The mixture was stirred at 500 rpm for 16 hours, and then centrifuged at 8500 rpm for 6 minutes. The supernatant was poured out and a yellow precipitate was collected. 5 mL of methanol was added and the solution was shaken vigorously to allow the yellow precipitate to dissolve in the methanol again. The mixture was shaken until the solution was uniform in color, centrifuged again, and this step was repeated three times. Finally, the mixture was dried in a vacuum oven at room temperature overnight and weighed to obtain the yellow hydrogen bond organic framework HOF-101.

[0055] (2) 40 mg of the prepared hydrogen-bonded organic framework HOF-101 was mixed with 2 g of ascorbic acid to construct a photocatalytic system.

[0056] Example 2 Construction of photocatalytic system

[0057] 40 mg of the prepared hydrogen-bonded organic framework HOF-101 was mixed with 0.4 g of ascorbic acid to construct a photocatalytic system.

[0058] Example 3 Construction of photocatalytic system

[0059] 20 mg of the prepared hydrogen-bonded organic framework HOF-101 was mixed with 2 g of ascorbic acid to construct a photocatalytic system.

[0060] Example 4 Construction of photocatalytic system

[0061] 120 mg of the prepared hydrogen-bonded organic framework HOF-101 was mixed with 2 g of ascorbic acid to construct a photocatalytic system.

[0062] Example 5 Construction of photocatalytic system

[0063] 40 mg of the prepared hydrogen-bonded organic framework HOF-101 was mixed with 5 g of ascorbic acid to construct a photocatalytic system.

[0064] Example 6 Construction of Photocatalytic System

[0065] (1) Preparation of HOF-102: First, 20 mg of the organic ligand 6,6',6",6"'-(pyrene-1,3,6,8-tetrayl)tetrakis(2-naphthoic acid) (H4TNAPy) was dissolved in 2 mL of DMF and heated at 120°C to completely dissolve the organic ligand until the solution was transparent and free of particles. Subsequently, 15 mL of acetone was poured into the solution while stirring, and stirring was continued at 500 rpm for 16 hours. The mixture was centrifuged at 8500 rpm for 6 minutes, and the supernatant was discarded to collect the precipitate. 5 mL of acetone was added to the precipitate, mixed thoroughly, and centrifuged again. This washing step was repeated 3 times. Finally, the product was dried in a vacuum oven at room temperature overnight to obtain the hydrogen-bonded organic framework HOF-102.

[0066] (2) 40 mg of the prepared hydrogen bond organic framework HOF-102 was mixed with 2 g of ascorbic acid to construct a photocatalytic system.

[0067] Example 7 Construction of Photocatalytic System

[0068] (1) Preparation of HOF-CH3: 20 mg of the organic ligand 1,3,6,8-tetrakis(4-carboxyphenylmethyl)pyrene (H4TBAPy-CH3) was dissolved in 2 mL of DMF and the solution was made transparent by ultrasonic treatment. 18 mL of methanol was then added to the solution while stirring. After stirring for 5 minutes, the solution became turbid, indicating that the organic ligands were successfully assembled to synthesize the HOF material. After standing for 30 minutes, the solution was centrifuged at 12,000 rpm for 6 minutes to separate the precipitate. The supernatant was poured out and methanol / ethanol was added to dissolve the precipitate and centrifuged again. After washing with methanol three times, the product was dried in a vacuum oven at room temperature overnight and weighed to obtain the hydrogen bonded organic framework HOF-CH3.

[0069] (2) 40 mg of the prepared hydrogen bond organic framework HOF-CH3 was mixed with 2 g of ascorbic acid to construct a photocatalytic system.

[0070] Comparative Example 1

[0071] (1) Preparation of HOF-100: First, 20 mg of the organic ligand pyrene-1,3,6,8-tetracarboxylic acid (H4TCPy) was dissolved in 2 mL of DMF and heated at 120 °C to completely dissolve the ligand until the solution was transparent and free of particles. Subsequently, 15 mL of acetone was poured into the solution while stirring, and stirring was continued at 500 rpm for 16 hours. The mixture was centrifuged at 8500 rpm for 6 minutes, and the supernatant was discarded to collect the precipitate. 5 mL of acetone was added to the precipitate, mixed thoroughly, and centrifuged again. This washing step was repeated 3 times. Finally, the product was dried in a vacuum oven at room temperature overnight to obtain the hydrogen-bonded organic framework HOF-100.

[0072] (2) 40 mg of the prepared hydrogen bond organic framework HOF-100 was mixed with 2 g of ascorbic acid to construct a photocatalytic system.

[0073] Comparative Example 2

[0074] (1) Preparation of HOF-NH2: 20 mg of the organic ligand 1,3,6,8-tetrakis(4-carboxyphenylamino)pyrene (H4TBAPy-NH2) was dissolved in 2 mL of DMF and the solution was made transparent by ultrasonic treatment. 18 mL of methanol was then added to the solution while stirring. After stirring for 5 minutes, the solution became turbid, indicating that the organic ligands were successfully assembled to synthesize the HOF material. After standing for 30 minutes, the solution was centrifuged at 12,000 rpm for 6 minutes to separate the precipitate. The supernatant was poured out and methanol / ethanol was added to dissolve the precipitate and centrifuged again. After washing with methanol three times, the product was dried in a vacuum oven at room temperature overnight and weighed to obtain the hydrogen bonded organic framework HOF-NH2.

[0075] (2) 40 mg of the prepared hydrogen bond organic framework HOF-NH2 was mixed with 2 g of ascorbic acid to construct a photocatalytic system.

[0076] Comparative Example 3

[0077] 40 mg of the prepared hydrogen-bonded organic framework HOF-101 was mixed with 2 g of ethylenediaminetetraacetic acid (EDTA) to construct a photocatalytic system.

[0078] Comparative Example 4

[0079] 40 mg of the prepared hydrogen bond organic framework HOF-101 was mixed with 2 g of glucose to construct a photocatalytic system. Test Example 1 Removal of dibutyl phthalate (DBP)

[0080] Experimental Procedure: The adsorption capacity of HOF-101 prepared in Example 1 for DBP in water was experimentally evaluated. The HOF-101 concentration in water was set to 40 mg / L. Adsorption was tested at different initial DBP concentrations (C0 = 10, 30, 60, and 90 μM). Pseudo-first-order (PFO) and pseudo-second-order (PSO) kinetic models were used to analyze the adsorption process. The fitting results determined the relevant parameters. Two different adsorption isotherm models (Langmuir and Freundlich) were used to describe the interaction between the adsorbent and the adsorbed molecules at equilibrium.

[0081] The experimental results are as follows Figure 1 、 Figure 2 , as shown in Table 1 and Table 2, the fitting results are as follows: R 2 are all greater than 0.99, but compared with the calculation results of PSO model and PFO model, the adsorption amount (qe.cal ) is closer to the adsorption amount of the experimental results (q e.exp ). Therefore, the PSO model is more appropriate to describe the adsorption of DBP on HOF, which shows that HOF-101 is a monolayer adsorption system for DBP.

[0082] Using two different adsorption isotherm models to describe the results, the Langmuir model was found to be more suitable for describing the HOF DBP adsorption isotherm, indicating that DBP adsorbs on the material surface as a monolayer. The factors influencing the adsorption driving force are complex, with common ones including hydrogen bonding, π-π stacking, van der Waals forces, hydrophobic interactions, and electrostatic interactions.

[0083] Table 1. Parameters related to fitting using pseudo first-order (PFO) and pseudo second-order (PSO) kinetic models

[0084]

[0085] Table 2. Fitting results of two different adsorption isotherm models (Langmuir and Freundlich)

[0086]

[0087]

[0088] Test Example 2 Photocatalytic HOF-101 Removal of DBP

[0089] Since the highest occupied molecular orbital (HOMO) of HOF-101 is mainly located at the center of the pyrene core, while the lowest unoccupied molecular orbital (LUMO) is evenly distributed on H4TBAPy, this causes photogenerated holes to easily recombine with electrons, resulting in poor photocatalytic activity. Therefore, ascorbic acid was added to prevent the complexation of photogenerated carriers.

[0090] The photocatalytic system prepared in Example 1 was added to a water body containing DBP. The water body was prepared with ultrapure water. The concentration of DBP was 8.35 mg / L, the concentration of HOF-101 was 40 mg / L, the concentration of ascorbic acid was 2 g / L, the pH was about 3, and the total volume of the solution for the experimental reaction was 5 mL. After 15 minutes of dark adsorption, the experiment was conducted under a 420 nm LED blue light (8 mW / cm 2 ) for 1 hour, and the DBP concentration was detected by gas chromatography-mass spectrometry combined with solid phase microextraction.

[0091] Quantitative analysis was performed using direct immersion solid-phase microextraction coupled with gas chromatography-mass spectrometry (GC-MS). After the sample was transferred to a 10 mL glass vial and diluted, a polydimethylsiloxane (PDMS)-coated fiber was used to extract the target pollutants under optimized conditions. The PDMS fiber was then desorbed on an Agilent 7890GC-5977MS equipped with a DB-5MS column (30 m × 0.25 mm) to quantitatively determine the extracted pollutants. For the detection of PAEs, the PDMS fiber was immersed in the sample solution at 60°C for extraction for 30 minutes. The fiber was then transferred to a GC-MS system for thermal desorption analysis. High-purity helium was used as the carrier gas at a flow rate of 3 mL / min. The inlet temperature was set at 250°C, and the ion source temperature was 230°C. The heating program was as follows: initially maintain the temperature at 60°C for 1 minute, then heat to 150°C at a rate of 10°C / min, then heat to 280°C at a rate of 20°C / min and hold for 3.5 minutes. The SPME extraction and desorption process was automated using a GERTEL LabWorks multifunctional autosampler according to a pre-programmed sequence. Finally, the concentration of the pollutant was quantified by comparing the peak area with that of a sample of known concentration.

[0092] Figure 3 In the figure, the HOF-AA curve represents the total removal of DBP degradation + adsorption, and the HOF-AA (DMF) curve is the DBP adsorbed on HOF in the solution after the HOF-AA reaction was eluted with DMF. That is, the HOF-AA (DMF) curve represents the amount of DBP degradation, and the Adsorption area in the middle represents the amount of DBP adsorption. Figure 3 As shown, ascorbic acid exhibits excellent results, with a DBP removal rate of nearly 90% within 30 minutes. Using DMF to elute the adsorbed DBP for testing, it was found that the addition of ascorbic acid significantly enhanced the photocatalytic activity of HOF-101, achieving a 95.36% DBP photocatalytic conversion within 1 hour. This is likely due to ascorbic acid's strong reducing and electron transfer abilities, and its ability to capture photogenerated holes, which effectively reduces the possibility of electron-hole pair recombination. Common reducing agents such as EDTA, glucose, and ammonium oxalate do not have this effect.

[0093] Test Example 3: Photocatalytic system's resistance to water environment pH interference

[0094] The pH value of the water environment usually has a relatively large impact on the reaction process. The organic ligand H4TBAPy of HOF-101 itself contains 4 carboxyl groups, and the self-assembled HOF-101 naturally has a large number of carboxyl groups. This affects the structural stability of HOF-101 in an alkaline water environment, resulting in a significant decrease in the catalytic effect. However, ascorbic acid, as a weak acid, can neutralize the alkali in the aqueous solution, so that the adsorption and catalytic ability of HOF-101 are restored. At the same time, the added ascorbic acid can also greatly promote the photocatalytic process. Ascorbic acid is first added to the solution because ascorbic acid is acidic and has an effect on pH. Then, a DBP-containing aqueous solution (DBP concentration of 8.35 mg / L) with different pH (1-11) is prepared and added to the photocatalytic system prepared in Example 1 (so that the concentration of HOF-101 is 40 mg / L and the concentration of ascorbic acid is 2 g / L). After 15 minutes of dark adsorption and 1 hour of light exposure, the detection method of DBP concentration is the same as that of Test Example 2.

[0095] Experimental results: Figure 4 As shown in the figure, ascorbic acid is affected by pH value and often exists in the form of corresponding dehydrogenated ions (H2A, HA - and A 2- ), the dominant species also changes at different pH values. When only ascorbic acid is added and the pH is not adjusted additionally, the default initial pH of the reaction system is 3.0. 0.1M HCl and NaOH are used to adjust the pH from 1 to 11. When the pH value is 1 to 7, DBP has a good degradation rate; when the pH is 11, DBP can no longer be well adsorbed and degraded. This is because when the pH is lowered, the hydrogen ion concentration in the water increases, which causes superoxide radicals to combine with hydrogen ions to generate by-products such as hydrogen peroxide, which is not conducive to its oxidation to produce singlet oxygen. On the other hand, it has been reported that the strength of the reducing power of ascorbic acid in different ionic states is A 2- >HA - >H2A, which means that the increase in pH will make the more reducing HA - It becomes the dominant species and is beneficial to the progress of the photocatalytic reaction.

[0096] The effect of pH on the morphology of the material is also worth noting. When the pH is in an alkaline environment, it also has a certain damage to the storage of HOF-101. However, the addition of ascorbic acid can just lower the pH, and increasing the dosage of ascorbic acid is also beneficial to the degradation rate, which makes up for the defect of the system in removing DBP under alkaline conditions.

[0097] Test Example 4: Photocatalytic System Resistance to Ion Interference in Aqueous Environment

[0098] Solutions with 5 mM concentrations of sodium chloride, sodium nitrate, sodium bicarbonate, and sodium sulfate were prepared to test the effects of different anions on degradation. The photocatalytic system prepared in Example 1 was then added to the solution, resulting in concentrations of 40 mg / L HOF-101, 2 g / L ascorbic acid, and 8.35 mg / L DBP. After 15 minutes of dark adsorption, the solution was illuminated for one hour. The DBP concentration was measured using the same method as in Test Example 2.

[0099] Depend on Figure 5 and Figure 6 It can be seen that Cu 2+ The biggest impact on DBP removal rate is due to the fact that Cu 2+ It can be anchored on HOF-101 through electrostatic and coordination interactions with the -COOH group of the linker, which greatly reduces the adsorption rate of DBP. At the same time, in the presence of copper ions, electrons may transfer from the excited state of HOF-101 to the d orbital of copper ions. These conditions will have a great impact on the process of removing DBP. - The addition of ions can increase the conversion rate of DBP, and SO4 2- The ion rate is reduced, and the other ions have no significant effect on the rate. This is because NaHCO3 is weakly alkaline in water, which changes the initial pH of the reaction and thus affects the conversion rate of DBP. SO4 2- Ions may form inactive free radicals SO4· - This interferes with the production of ROS, which is beneficial for DBP conversion.

[0100] Test Example 5: Photocatalyst system resists interference from natural organic matter in aquatic environments

[0101] Natural organic matter (NOM) mainly refers to organic substances widely distributed in nature, such as oils, sugars, and proteins. Since these substances are organic compounds synthesized in organisms, they are called natural organic matter. Because they can also be degraded by photocatalysis, their presence may occupy the reaction sites on the catalytic system, thereby affecting the degradation effect of the target pollutants. Different concentrations of NOM solutions (0-10 mg / L, NOM comes from: International Humic Substances Society, NOM is a complex organic mixture, mainly composed of humus (humic acid, fulvic acid, humin), containing a wide variety of organic substances with complex composition, and non-humic components include carbohydrates, amino acids, lipids, etc.) were prepared and added to the photocatalytic system prepared in Example 1, so that the concentration of HOF-101 in the solution was 40 mg / L, the concentration of ascorbic acid was 2 g / L, and the concentration of DBP was 8.35 mg / L. After 15 minutes of dark adsorption and 1 hour of light exposure, the DBP concentration was detected in the same way as in Test Example 2.

[0102] like Figure 7 As shown, as the concentration of NOM increased from 2 mg L -1 Increased to 10 mg L -1 , the adsorption capacity of HOF-101 on DBP decreased slightly, and the removal rate of DBP also decreased slightly. This is because the addition of NOM consumed the free radicals generated by photocatalysis, and some substances occupied the adsorption sites of DBP. However, the overall removal effect of the system on DBP was not greatly affected, and the concentration of NOM in natural water bodies is generally around 15 mg L -1 the following.

[0103] Test Example 6 Application of the Photocatalyst System in Actual Water Environment

[0104] The actual water environment is very complex. In addition to the target pollutants, it also contains many interfering factors, such as salt, pH, other organic matter, etc. In order to investigate the practical application of the photocatalytic system in complex water bodies, 5 mL each of tap water, Jinghu water (within the Panyu campus of Jinan University, 23°01'09"N 113°24'32"E), and Pearl River water (near Xinzao Ferry, 23°02'18"N113°24'24"E) were used instead of ultrapure water as the solution, and the photocatalytic system prepared in Example 1 was also added to make the concentration of HOF-101 in the solution 40 mg / L, the concentration of ascorbic acid 2 g / L, and the concentration of DBP 8.35 mg / L. After 15 minutes of adsorption in the dark and 1 hour of illumination, the DBP concentration detection method was the same as in Test Example 2.

[0105] like Figure 8 As shown, the photocatalytic system has a good adsorption effect on DBP in different water environments, and has a good photocatalytic degradation effect in tap water and Pearl River water. The degradation rate in other water bodies is inhibited, which may be due to the presence of other organic matter in the water, which is consistent with the experimental results on the effect of NOM concentration on photocatalysis.

[0106] Test Example 7 Reusability of Photocatalyst System

[0107] 40 mg / L of HOF-101 prepared in Example 1 was added to 5 mL of a DBP solution having a concentration of 8.35 mg / L, and the reaction solution was shaken in the dark for 15 minutes to reach adsorption equilibrium. Subsequently, 2 g / L of ascorbic acid was added, and the reaction system was reacted for 1 hour under light conditions. After the reaction was completed, a small amount of the reacted solution was removed and diluted with ultrapure water for subsequent detection. The illumination was then continued for 2 hours to reduce the effect of the intermediate product on subsequent degradation. Subsequently, DBP and ascorbic acid (the same as the initial concentration) were added to the reaction system and the system was illuminated again. The operation steps were the same as before and repeated 4 times. The removal rate was calculated after detecting the DBP concentration.

[0108] like Figure 9 As shown in the figure, after being reused for 4 times, even though the initial adsorption rate of DBP decreased, the photocatalytic system still had good photocatalytic activity.

[0109] Test Example 8: DBP Removal in Different HOF Systems

[0110] The photocatalytic systems prepared in Example 1, Examples 6-7, and Comparative Examples 1-2 were added to a water body containing DBP (DBP concentration was 8.35 mg / L), such that the concentration of each HOF in the water body was 40 mg / L and the concentration of ascorbic acid was 2 g / L. The experiment was conducted under a 420 nm LED blue light (8 mW / cm 2 ) for 1 hour, and the DBP concentration detection method is the same as that in Test Example 2.

[0111] like Figure 10 As shown in Figure 9, HOF-101, HOF-102, and HOF-CH3 have excellent DBP removal effects when combined with ascorbic acid, while HOF-NH2 and HOF-100 have little effect when combined with ascorbic acid.

[0112] Ethylenediaminetetraacetic acid (EDTA), glucose (Glu) and ascorbic acid (L-AA) were selected to inhibit the recombination of photogenerated carriers in HOF, and the effects of different substances were compared. The dosage of HOF-101 was 40 mg / L, and the concentrations of EDTA / Glu / L-AA were all 2 g / L. Ultrasonic instrument was used to accelerate the dissolution. The initial DBP dosage was 8.35 mg / L. The adsorption was carried out under oscillation in the dark for 15 minutes. The subsequent illumination experiment was carried out under 420 nm LED blue light (8 mW / cm 2 ) for 1 hour, and the DBP concentration detection method is the same as that in Test Example 2.

[0113] like Figure 11As shown, the photocatalytic promotion effect is in the order of L-AA > EDTA > Glu. The addition of L-AA enabled the system to remove 98% of DBP within 60 minutes, demonstrating excellent removal efficiency. The EDTA group removed 70% of DBP, showing no significant improvement compared to the control group. The Glu group, on the other hand, was only comparable to the control group.

[0114] Test Example 10: Removal of DBP by Different HOF and Ascorbic Acid Mass Ratios

[0115] The dosage of HOF-101 was varied to (20, 40, 80, and 120 mg / L), the dosage of ascorbic acid was varied to (0.4, 1, 2, and 5 g / L), and the DBP concentration was 8.35 mg / L, and a single variable experiment was performed. The system default parameters were the same as in Example 2, i.e., when the HOF dosage was varied, the ascorbic acid dosage was 2 g / L. When the ascorbic acid dosage was varied, the HOF-101 dosage was 40 mg / L. After 15 minutes of dark adsorption and 1 hour of illumination, the DBP concentration detection method was the same as in Test Example 2.

[0116] like Figure 12 、 Figure 13 and Figure 14 As shown, as the HOF-101 concentration increased from 20 mg / L to 120 mg / L, the combination of HOF-101 and L-AA exhibited excellent DBP removal efficiency. When the HOF-101 concentration increased from 40 mg / L to 120 mg / L, there was no significant change in DBP removal efficiency after 60 minutes of treatment. The DBP removal rate also significantly increased with increasing L-AA concentration. Compared to the effect of HOF-101 concentration changes, the effect of L-AA concentration changes was more intuitive, especially when the L-AA concentration was 1-5 g / L. The combination of HOF-101 and L-AA exhibited excellent DBP removal efficiency.

[0117] The foregoing examples are merely illustrative, serving to illustrate some of the features of the method of the present invention. The appended claims are intended to claim the widest possible scope that can be envisioned, and the embodiments presented herein are demonstrated by the applicant's actual experimental results. Therefore, the applicant intends that the appended claims are not limited by the selection of examples illustrating the features of the present invention. Some numerical ranges used in the claims also include subranges therein, and variations in these ranges should also be interpreted as being covered by the appended claims where possible.

Claims

1. A photocatalytic system, characterized in that: include: A hydrogen-bonding organic framework and ascorbic acid; the organic ligand of the hydrogen-bonding organic framework is selected from at least one of 1,3,6,8-tetrakis(4-carboxyphenyl)pyrene, 6,6',6",6"'-(pyrene-1,3,6,8-tetrayl)tetrakis(2-naphthoic acid) or 1,3,6,8-tetrakis(4-carboxyphenylmethyl)pyrene.

2. The photocatalytic system according to claim 1, characterized in that: The mass ratio of the hydrogen bond organic framework to ascorbic acid is 0.01-0.20:1-10.

3. The photocatalytic system according to claim 1, characterized in that: The mass ratio of the hydrogen bond organic framework to ascorbic acid is 0.04-0.12:2-5.

4. The photocatalytic system according to claim 1, characterized in that: The preparation method of the hydrogen bond organic framework is as follows: dissolving an organic ligand in N,N-dimethylformamide, then adding an alcohol solvent or a ketone solvent, and mixing them uniformly to obtain the hydrogen bond organic framework.

5. Use of the photocatalytic system according to any one of claims 1 to 4 in photocatalytic degradation of organic pollutants.

6. The use of ascorbic acid in promoting the photocatalytic degradation of organic pollutants by hydrogen-bonded organic frameworks, characterized in that: The organic ligand of the hydrogen-bonded organic framework is selected from at least one of 1,3,6,8-tetrakis(4-carboxyphenyl)pyrene, 6,6',6",6"'-(pyrene-1,3,6,8-tetrayl)tetrakis(2-naphthoic acid) or 1,3,6,8-tetrakis(4-carboxyphenylmethyl)pyrene.

7. The use according to claim 5 or 6, characterized in that: The organic pollutants are selected from one or more of phthalates, phenolic organic pollutants, polybrominated diphenyl ether organic pollutants, and organic dyes.

8. The use according to claim 5 or 6, characterized in that: Photocatalytic illumination time ≥ 15 min; and / or illumination intensity ≥ 5 mW / cm 2 .

9. A method for degrading organic pollutants in an aquatic environment, characterized in that: The photocatalytic system according to any one of claims 1 to 4 is mixed with water containing organic pollutants, and the water is treated under light conditions.

10. The method according to claim 9, characterized in that: The pH of the water environment is 1-9.

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