Polyacid cluster catalyst based on confinement self-reduction of PAFs as well as preparation method and application of polyacid cluster catalyst
By loading polyacid clusters into the pores of PAFs, and utilizing strong electrostatic interactions and nitrogen atom reduction, the problems of weak visible light response and stability of POMs photocatalytic materials were solved, achieving the effect of highly efficient catalytic degradation of water pollutants.
Patent Information
- Application Number
- CN202511585422.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-31
- Publication Date
- 2026-01-27
AI Technical Summary
In the existing technology, polyoxometalates (POMs) photocatalytic materials have limited ultraviolet light response range and weak visible light absorption capacity. Furthermore, the loading methods suffer from problems such as weak binding force, easy dissolution of active components, low loading amount, or limited specific surface area of the support, which limits their application in water treatment.
Polyacid clusters are loaded into the pores of PAFs by impregnation and tightly connected by strong electrostatic interactions, achieving high loading and uniform distribution at the molecular level. Combined with the partial reduction of nitrogen atoms in the PAF framework, the catalytic performance is improved and the recombination of photogenerated carriers is suppressed.
The visible light activity of POMs has been enhanced, stabilized and immobilized, and efficiently recycled. The catalyst exhibits outstanding catalytic performance in heterogeneous photocatalytic degradation of water pollutants, and its structural stability and catalytic activity remain unchanged during multiple cycles.
Smart Images
Figure HDA0005665725050000011 
Figure HDA0005665725050000012 
Figure HDA0005665725050000021
Abstract
Description
Technical Field
[0001] This invention belongs to the field of catalytic chemistry technology, specifically a polyacid cluster catalyst based on PAFs confined self-reduction, its preparation method, and its application. Background Technology
[0002] With the rapid development of my country's social economy and the significant improvement in people's living standards, environmental awareness has also been continuously enhanced. The overuse of antibiotics such as tetracycline has become increasingly serious, placing a heavy burden on ecosystems. These drugs, due to their numerous types, poor degradability, and high toxicity, easily lead to eutrophication after entering water bodies, posing a serious threat to ecological balance. However, conventional technologies such as oxidation-adsorption and incineration have limited capacity to treat these recalcitrant organic pollutants.
[0003] Photocatalysis, as an advanced oxidation process utilizing solar energy for chemical reactions, has shown great application potential in environmental pollution control, especially in water treatment, due to its environmental friendliness, ease of operation, and low energy consumption. Among numerous photocatalytic materials, polyoxometalates (POMs), as a class of metal-oxygen cluster compounds formed by bridging former transition metal ions (such as Mo, W, and V) with oxygen, have attracted widespread attention in the field of photocatalysis due to their unique electronic structure and excellent redox properties.
[0004] However, directly applying POMs to photocatalysis still faces several serious challenges, limiting their large-scale practical application. First, the photoresponse range of most POMs is limited to the ultraviolet region, while their absorption capacity for visible light, which accounts for the majority of solar energy, is very weak, resulting in low solar energy utilization efficiency. Second, homogeneous POM catalysts have high solubility in aqueous solutions, making them difficult to recover and reuse, easily causing secondary pollution and increasing costs. To address these issues, researchers typically employ a strategy of loading POMs onto various supports (such as silica, activated carbon, and metal oxides) to construct heterogeneous catalytic systems. However, traditional loading methods often suffer from weak binding forces, easy dissolution of active components, low loading capacity, or limited specific surface area of the support.
[0005] More importantly, conventional loading methods, mostly based on physical adsorption or simple electrostatic interactions, are insufficient to fundamentally alter the electronic structure and light absorption characteristics of POMs. To extend their visible light response, existing research strategies typically involve complex elemental doping, organic ligand modification, or the construction of noble metal / semiconductor heterojunctions. While these methods are effective to some extent, they often present new challenges such as complex fabrication processes, high costs, or poor material stability. Therefore, developing a simple, efficient, and easily recyclable novel composite catalytic material that can fundamentally enhance the visible light catalytic activity of POMs has become a critical scientific challenge and technological bottleneck in this field. Summary of the Invention
[0006] The purpose of this invention is to provide a polyacid cluster catalyst based on PAFs confined self-reduction, its preparation method and application, so as to simultaneously achieve visible light activity enhancement, stable immobilization and efficient recycling of POMs without introducing complex processes or expensive materials.
[0007] The objective of this invention is achieved through the following technical solution:
[0008] Technical Solution 1:
[0009] A polyacid cluster catalyst based on PAFs confined self-reduction is prepared by impregnation method, in which polyacid clusters are loaded into the pores of PAFs. The PAFs are porous frameworks containing viologen-like cationic groups. Under acidic conditions, the framework is more conducive to the adsorption of polyacid clusters with anionic frameworks, so as to achieve strong electrostatic interaction and tight connection between PAFs and polyacid clusters, thereby increasing the loading of heteropolyacids and reducing the aggregation and dissolution of heteropolyacids.
[0010] The polyacid cluster catalyst provided by this invention has a high heteropolyacid loading; simultaneously, strong electrostatic interaction can reduce the aggregation and dissolution of heteropolyacids; nitrogen atoms on the PAF framework can also partially reduce phosphomolybdic acid to improve its catalytic performance; the immobilization of polyacid clusters into the PAF voids can also achieve uniform distribution of polyacid clusters at the molecular level; the heterogeneous combination of PAFs and polyacid clusters can also suppress the recombination of photogenerated carriers, thereby improving photocatalytic performance. The catalyst prepared by this invention can be used as a heterogeneous photocatalyst, exhibiting outstanding catalytic performance in the catalytic degradation of pollutants in water; furthermore, the catalyst can be reused without any change in structure or catalytic activity; the preparation process of this material is simple, and the catalytic conditions are mild and efficient, showing potential application prospects in the field of catalysis.
[0011] The framework of the polyacid clusters is an anionic framework.
[0012] As one possible implementation of this application, the polyacid cluster is a Keggin-type phosphomolybdic acid.
[0013] As one possible implementation of this application, the PAFs are viologen-type cationic PAF-C2 with a pore size greater than 1 nm.
[0014] Technical Solution Two:
[0015] A method for preparing a polyacid cluster catalyst based on PAF confined self-reduction includes the following steps:
[0016] S1. Preparation of viologen-based cationic PAF-C2 under nitrogen atmosphere protection;
[0017] S2. Phosphomolybdic acid is pre-dissolved in deionized water, and then PAF-C2 is added. After the reaction is complete, the mixture is centrifuged, washed, dried, and ground to obtain a polyacid cluster catalyst.
[0018] As one possible implementation of this application, in step S2, the mass ratio of phosphomolybdic acid to PAF-C2 is (0.33~2):1.
[0019] As some possible implementations of this application, in step S2, the temperature for a complete reaction is room temperature, and the reaction time is 48 to 72 hours.
[0020] Technical Solution 3:
[0021] An application of a polyacid cluster catalyst based on PAFs confined self-reduction, wherein the polyacid cluster catalyst is used as a photocatalyst to catalytically degrade tetracycline pollutants in water.
[0022] As some possible implementation methods of this application, the concentration of tetracycline solution in the water body is 8-15 mg / L, and the pH range of the water body is 5-8.
[0023] As some possible implementation methods of this application, the operational steps for the degradation of tetracycline pollutants in water by polyacid cluster catalysts are as follows:
[0024] S1. Prepare a tetracycline simulation solution of a certain concentration in advance (tetracycline solution concentration is 8-15 mg / L), then adjust the pH to 5-8, add 5-20 mg / L of polyacid cluster catalyst, and stir in the dark for 0.5-1 h to achieve the adsorption / desorption balance between the photocatalytic material and tetracycline for subsequent photocatalytic reaction;
[0025] S2. At a certain temperature, a xenon lamp is used as a solar simulator to carry out a catalytic reaction. Samples are taken at certain intervals, and the filtrate is collected for later use by membrane filtration.
[0026] S3. The absorbance at 357 nm was measured using a UV-Vis spectrophotometer and converted into the concentration change of tetracycline in the solution to obtain the catalytic results.
[0027] Compared with the prior art, the beneficial effects of the present invention are:
[0028] 1. The PAFs confined self-reducing polyacid cluster catalyst preparation strategy provided by the present invention is simple and feasible: the catalyst can be prepared in large quantities under conventional stirring at room temperature, and thanks to the porosity structure of the PAFs framework, polyacid clusters can be immobilized therein to achieve uniform distribution at the molecular level, while having a high heteropolyacid loading.
[0029] 2. The PAFs confined self-reducing polyacid cluster catalyst provided by the present invention has good structural stability: the PAF-C2 framework has abundant nitrogen positive ion sites, which can strongly bind with the polyacid clusters of the anionic framework through strong electrostatic interaction, thereby stabilizing the structure on the one hand and reducing the aggregation of heteropolyacids on the other hand; and the polyacid clusters are immobilized in the PAFs voids, which further ensures the structural stability through spatial confinement.
[0030] 3. The PAFs confined self-reducing polyacid cluster catalyst provided by this invention exhibits excellent catalytic performance: the N-containing functional groups in PAF-C2 possess weak reducing properties, enabling them to not only convert Mo... 6+ Restored to Mo 5+ And keep the Keggin structure of PMo unchanged (Mo 5+ It can enhance the intrinsic activity of PMo; at the same time, the heterogeneous combination of PAFs and polyacid clusters can suppress the recombination of heterogeneous photogenerated carriers. Combined with the advantage of the uniform distribution of polyacid clusters at the molecular level, it can jointly improve photoelectric efficiency and photocatalytic activity.
[0031] 4. The PAFs confined self-reducing polyacid cluster catalyst provided by the present invention can be used as a heterogeneous photocatalyst and has outstanding catalytic performance in the photocatalytic degradation of tetracycline pollutants: it can achieve a degradation efficiency of more than 85% for tetracycline within 70 minutes.
[0032] 5. The PAFs-confined self-reducing polyacid cluster photocatalyst provided by this invention has excellent photocatalytic stability and structural stability: strong electrostatic interaction can reduce the dissolution of heteropolyacids, and the spatial confinement and fixation of polyacid clusters by PAFs voids can maintain the catalytic activity unchanged in at least 5 cycles, indicating that the catalyst structure has not collapsed, realizing repeated use without changes in structure and catalytic activity; in addition, the material preparation process is simple and the catalytic conditions are mild and efficient, laying the foundation for recycling and practical application. Attached Figure Description
[0033] Figure 1The diagram shows the synthesis of PMo@PAF-C2, as well as physical images of PAF-C2 and PMo@PAF-C2.
[0034] Figure 2 (a) X-ray powder diffraction pattern of PAF-C2 and PMo@PAF-C2(2:1); (b) Infrared spectrum.
[0035] Figure 3 For PAF-C2 and PMo@PAF-C2(2:1) 13 C solid carbon nuclear magnetic resonance spectrum.
[0036] Figure 4 Nitrogen adsorption-desorption isotherms for PAF-C2 and PMo@PAF-C2 (2:1).
[0037] Figure 5 Thermogravimetric curves of PAF-C2, PMo@PAF-C2 (2:1) and phosphomolybdic acid under nitrogen conditions are shown.
[0038] Figure 6 The full spectrum of X-ray photoelectron spectroscopy analysis of PAF-C2 and PMo@PAF-C2 (2:1).
[0039] Figure 7 X-ray photoelectron spectroscopy analysis spectra: N 1s spectrum: (a) PAF-C2; (b) PMo@PAF-C2(2:1); Mo 3d spectrum: (c) PMo; (d) PMo@PAF-C2(2:1).
[0040] Figure 8 Photocatalytic degradation experiments of tetracycline using PMo@PAF-C2: (a) degradation efficiency of different photocatalysts under visible light; (b) catalyst dosage; (c) effect of pH on catalytic performance; (d) zata potential of PMo@PAF-C2 (2:1) at different pH values.
[0041] Figure 9 The inhibitory effects of different quenchers on the photodegradation of tetracycline.
[0042] Figure 10 Experiments for free capture of electrons by paramagnetic spectra: (a) BQ-·O of PAF-C2 2- Spectrum; (b) BQ-·O of PMo@PAF-C2(2:1) 2- (c) DMSO-·OH spectrum of PAF-C2; (d) DMSO-·OH spectrum of PMo@PAF-C2 (2:1).
[0043] Figure 11For photoelectric performance testing: (a) Mott-Schottky curve of PAF-C2; (b) UV-Vis spectra of PAF-C2, PMo@PAF-C2 (2:1) and PMo; (c) Bandgap (αhν) of PAF-C2. 2 (d) Band gap (αhν) of phosphomolybdic acid. 2 A graph of hν.
[0044] Figure 12 This describes the photocatalytic degradation mechanism of tetracycline by PMo / PAF-C2 under visible light irradiation.
[0045] Figure 13 The results of a cycle experiment show the photodegradation of tetracycline catalyzed by PMo@PAF-C2. Detailed Implementation
[0046] Example 1
[0047] The preparation method of PMo@PAF-C2(2:1) is as follows:
[0048] S1. Preparation of viologen-type cationic PAF-C2 under nitrogen atmosphere protection [see Chem. J. Chinese Universities, 2024, 45(1), 20230438];
[0049] S2. Weigh 20 mg of phosphomolybdic acid (H3PMo) 12 O 40 PMo (abbreviated as PMo) was pre-dissolved in deionized water, and then 10 mg of PAF-C2 solid powder was added. The mixture was stirred under natural conditions for 48 h. The product was filtered to obtain a solid block, washed five times with deionized water, and then vacuum dried at room temperature for 9 h to obtain a blue-green PMo@PAF-C2 (2:1) solid powder. A simplified schematic diagram of the synthesis and sample images are shown below. Figure 1 As shown.
[0050] Example 2
[0051] The preparation methods of PMo@PAF-C2(1:1) and PMo@PAF-C2(1:3) are as follows:
[0052] The preparation process was the same as that for PMo@PAF-C2(2:1) in Example 1, with the amount of phosphomolybdic acid added being 10 mg and 3.3 mg, respectively, to obtain PMo@PAF-C2(1:1) and PMo@PAF-C2(1:3).
[0053] The product in Example 1 was analyzed using X-ray powder diffraction. Figure 2In the diagram, 'a' represents the X-ray powder diffraction patterns of PAF-C2 and PMo@PAF-C2(2:1). Neither PAF-C2 nor PMo@PAF-C2(2:1) exhibited characteristic diffraction peaks, indicating that their material framework lacks crystallinity. Therefore, it can be concluded that both materials, before and after phosphomolybdic acid loading, are amorphous. Furthermore, the introduction of phosphomolybdic acid had almost no effect on the structure of PAF-C2.
[0054] The product in Example 1 was detected using infrared spectroscopy. Figure 2 In the image, 'b' represents the infrared spectrum of PAF-C2 and PMo@PAF-C2 (2:1). The infrared spectrum of PAF-C2 at 1600 cm⁻¹ is clearly visible. -1 A distinct peak appears at 1600 cm⁻¹, which is caused by the stretching vibration of the newly formed CN bonds after the reactants combine, indicating that PAF-C2 was successfully synthesized. PMo@PAF-C2 shows a peak at 1600 cm⁻¹. -1 A peak value was also observed at 1100-770 cm⁻¹, indicating that the PAF-C2 structure remained stable after phosphomolybdic acid loading. Furthermore, the synthesized PMo@PAF-C2 exhibited peak values in the 1100-770 cm⁻¹ range. -1 Four characteristic peaks of the Keggin structure were observed in both samples, indicating that phosphomolybdic acid was successfully immobilized in the PAF-C2 framework.
[0055] use 13 The products in Example 1 were detected by solid-state carbon nuclear magnetic resonance spectroscopy. Figure 3 That is, PAF-C2 and PMo@PAF-C2(2:1). 13 Solid-state carbon NMR spectra. Characteristic peaks at δ = 145 and δ = 125 were observed in both the spectra of PAF-C2 and PMo@PAF-C2(2:1). The presence of these peaks is due to the presence of substituted and unsubstituted C atoms on the aromatic rings of the synthesized materials. Furthermore, the spectra of PAF-C2 and PMo@PAF-C2(2:1) are essentially consistent, indicating that the structure of PAF-C2 remains intact after phosphomolybdic acid loading, and the composite material is relatively stable.
[0056] The product in Example 1 was detected using a nitrogen adsorption-desorption test. Figure 4 The nitrogen adsorption-desorption curves for PAF-C2 and PMo@PAF-C2 (2:1) are shown. After loading, the nitrogen adsorption-desorption curve of the composite decreased significantly, possibly due to the blockage of phosphomolybdic acid in the pores of PAF-C2, leading to a decrease in the specific surface area of PMo@PAF-C2 (2:1). However, tests revealed that the composite material still maintains a high specific surface area and porous structure, which is beneficial for contact between active sites and substrates and promotes mass transfer during photocatalysis, thus resulting in excellent catalytic performance. The specific surface area of PAF-C2 was measured to be 224 m². 2 / g, the specific surface area of the loaded composite material PMo@PAF-C2(2:1) can reach 204m². 2 / g can still provide abundant active sites.
[0057] The products in Example 1 were analyzed using a thermogravimetric analyzer. Figure 5 This shows the weight loss curves for PAF-C2 and PMo@PAF-C2(2:1). Before 100℃, the decrease in weight loss is mainly due to the removal of adsorbed water molecules. PAF-C2 begins to decompose at 300℃, while PMo@PAF-C2(2:1) shows less weight loss in the 100-800℃ range, indicating that PMo@PAF-C2(2:1) has better thermal stability than PAF-C2. This further demonstrates that small increases in temperature do not damage the composite material during photocatalysis.
[0058] The product in Example 1 was detected using X-ray photoelectron spectroscopy. Figure 6 The X-ray photoelectron spectroscopy (XPS) spectra of PAF-C2 and PMo@PAF-C2(2:1) are shown. Compared to the overall spectrum of PAF-C2, the measured spectrum of PMo@PAF-C2(2:1) shows a significant increase of one characteristic peak of Mo 3d, further confirming the successful loading of PMo. Figure 7 These are the N1s and Mo 3d spectra of PAF-C2 and PMo@PAF-C2(2:1). The N1s spectrum of PAF-C2 shows peaks at 401.78 eV and 400.41 eV, corresponding to NR4, respectively. + And C=NC. In the Mo 3d spectrum of PMo@PAF-C2, the peaks at 232.62 eV and 235.75 eV correspond to Mo. 6+ Mo 3d 5 / 2 and Mo 3d 3 / 2 The peaks at 231.44 eV and 234.46 eV correspond to Mo. 5+ The dual state of Mo in phosphomolybdic acid after loading indicates that Mo... 6+ It has been partially restored to Mo 5+ In the Keggin structure, Mo 5+ Replaced Mo 6+ This results in the formation of heteropoly blue. Compared with the binding energy of Mo 3d in pure phosphomolybdic acid, the binding energy of Mo 3d in PMo@PAF-C2 (2:1) is reduced. However, by comparing the binding energy of N1s in PAF-C2 and PMo@PAF-C2, it was found that after loading with phosphomolybdic acid, NR4... +The binding energy increased from 401.78 eV to 401.90 eV. This indicates that during the synthesis of the hybrid material, electrons transferred from PAF-C2 to phosphomolybdic acid, forming Mo with significant catalytic activity. 5+ Then, the Mo content in the sample was calculated based on the area ratio in the X-ray photoelectron spectrum. 5+ / Mo 6+ The molar ratio is 0.2, Mo 5+ The total content is approximately 4.5 wt%, Mo 5+ The presence of [something] improves the photocatalytic performance of PMo@PAF-C2 composite materials.
[0059] Application examples
[0060] This application example verifies the catalytic degradation performance of the catalysts prepared in Examples 1-2 by conducting a photocatalytic degradation experiment of tetracycline using the catalyst PMo@PAF-C2.
[0061] The photocatalytic operation procedure is as follows: Multiple 50 mL solutions of tetracycline with an initial concentration of 10 mg / L were prepared, and 10 mg of PAF-C2 and a series of PMo@PAF-C2 were added to each solution. The solutions were stirred in the dark for 45 minutes to achieve adsorption / desorption equilibrium between the photocatalytic material and tetracycline. Afterward, the xenon lamp was turned on to initiate the photocatalytic reaction. Under visible light, 1 mL of the photocatalyzed mixed solution was collected within a specific time period and filtered through a 0.45 μm membrane. The concentration change of tetracycline in the solution was measured at 357 nm using a UV-Vis spectrophotometer to identify the photocatalyst with optimal photocatalytic performance. Figure 8 Figure 'a' shows the effect of different catalysts on tetracycline degradation. In the dark, tetracycline quickly reaches adsorption equilibrium, indicating that the composite material has a strong adsorption capacity for tetracycline, which is also beneficial to subsequent photocatalysis. As expected, the photocatalytic performance of the material was significantly improved after the introduction of phosphomolybdic acid. When the amount of phosphomolybdic acid increased from 3.3 mg to 20 mg, the degradation efficiency of tetracycline by the composite material gradually increased. This is mainly because the increased loading of phosphomolybdic acid increases the number of catalytic active centers, which is beneficial to photocatalysis. When the amount of phosphomolybdic acid is twice that of PAF-C2, PMo@PAF-C2(2:1) exhibits the best catalytic performance, achieving a degradation rate of over 85% for tetracycline within 70 min. In subsequent experiments, PMo@PAF-C2(2:1), which has the best photocatalytic performance, was selected as the catalyst.
[0062] Effect of photocatalyst dosage: Similar to the above photocatalytic operation procedure, 5, 10, and 20 mg of photocatalyst were added to 50 mL of tetracycline solution (10 mg / L), respectively. After adsorption in the dark for 45 min, the solution was irradiated for 90 min, and the solution was collected at specific time intervals. The tetracycline concentration was measured using a UV-Vis spectrophotometer. Figure 8 Figure b shows the effect of different catalyst dosages on tetracycline degradation. When the dosage of PMo@PAF-C2 (2:1) increased from 5 mg to 10 mg, the degradation efficiency of tetracycline increased from 77% to over 85%. However, increasing the dosage of PMo@PAF-C2 (2:1) to 20 mg did not significantly improve the catalytic efficiency. This may be due to excess sample in the solution, resulting in shading and absorption of scattered photons.
[0063] Effect of pH value on reaction system: The pH value of tetracycline solution was adjusted to 5-8 with dilute HCl and NaOH solution. Then, following the above photocatalysis operation procedure, 10 mg of the best performing photocatalyst was added to carry out the photocatalysis experiment, and the concentration of tetracycline was measured. Figure 8 Figure c shows the effect of different pH values on tetracycline degradation. The degradation efficiency of tetracycline increases with increasing pH, reaching its highest value at pH 7. This may be due to the electrostatic interaction between tetracycline and the photocatalyst, thus affecting the degradation. Tetracycline exists in different forms in aqueous solutions with different pH levels. Below pH 3.3, it is positively charged; between pH 3.3 and 7.7, it is a neutral ion; and above pH 7.7, it is negatively charged.
[0064] Figure 8 Figure d shows the Zata potential of PMo@PAF-C2(2:1) at different pH values. The figure shows that the surface charge gradually decreases with increasing pH. Therefore, in an acidic environment, after protonation, the catalyst adsorbs positive charges on its surface, forming electrostatic repulsion with cationic tetracycline, thus reducing the adsorption amount. In a weakly alkaline environment, electrostatic repulsion also occurs between the two negatively charged substances, affecting adsorption. However, the degradation efficiency at pH 8 was lower than at pH 7. This may be because, under alkaline conditions, some of the supported phosphomolybdic acid is detached, leading to a reduction in reactive sites. At pH 7, the positive charge on the surface of PMo@PAF-C2(2:1) allows for better adsorption of tetracycline.
[0065] Photocatalytic mechanism investigation: O2· quenching with 5 mmol / L tetramethylpiperidine (TEMPO) - The ·OH group was quenched by adding 5 mmol / L isopropanol (IPA), and the holes (h) were quenched by adding 5 mmol / L ethylenediaminetetraacetic acid (EDTA). +Add 10 mg of photocatalyst to each sample, repeat the above photocatalytic operation procedure, and measure the tetracycline concentration during the reaction. Figure 9 The method of quenching h by adding EDTA, TEMPO and IPA to tetracycline solution respectively is given. + O2· - The removal rate of tetracycline decreased significantly from 85% to 22% after the addition of EDTA, indicating a significant inhibitory effect. The degradation efficiency of tetracycline decreased to 38% after the addition of TEMPO. Experimental results show that h + And O2· - It plays a major role in the photocatalytic degradation of tetracycline. Simultaneously, it can be observed that the degradation efficiency of the catalyst for tetracycline remains almost unchanged after the addition of IPA, meaning that ·OH has almost no effect on tetracycline degradation. Similar conclusions can also be drawn through… Figure 10 Experimental evidence using electron paramagnetic spectroscopy is provided.
[0066] Figure 11 The photoelectric performance tests of PAF-C2 and PMo@PAF-C2(2:1) are presented. Figure 11 The flat-band potential (E) of PAF-C2 was calculated using the Mott-Schottky plot. FB The relative value of Ag / AgCl is -0.98V, while the E of phosphomolybdic acid is... FB The relative value is 0.65V compared to Ag / AgCl. Figure 11 The band gap energy of PAF-C2 was measured to be 2.72 eV (vs. Ag / AgCl) using UV-Vis spectroscopy, and its corresponding valence band (E) was calculated. VB The value is 1.54 eV (vs. Ag / AgCl); Figure 11 The band gap energy of phosphomolybdic acid was measured to be 2.21 eV (vs. Ag / AgCl) using UV-Vis spectroscopy. The corresponding valence band (E) was calculated. VB The value is 2.86 eV (vs. Ag / AgCl).
[0067] The above-mentioned mechanism study indicates that the recombination and separation of electron-hole pairs are crucial for the photocatalyst to acquire photocatalytic activity. Phosphomolybdic acid forms a heterojunction with PAF-C2, and photogenerated electrons (e-holes) occur on this heterojunction. - ) and holes (h + The separation and recombination of ) and the generation of superoxide radicals (O2· - O2· - It can further degrade tetracycline. And h, which has a phosphomolybdic acid valence band... + It can serve as an active site in photocatalytic reactions, participating in the degradation of tetracycline. The E group of phosphomolybdic acid... CB on e - E of PAF-C2 vBh on + The recombination of photogenerated electron-hole pairs can significantly avoid the recombination of photogenerated electron-hole pairs, thus ensuring the efficient conduction of photocatalytic reactions. Figure 12 Possible reaction mechanisms are also given.
[0068] Cyclic stability verification: Figure 13 The results of PMo@PAF-C2(2:1) after 5 cycles are presented, showing that its catalytic activity did not decrease significantly in at least 5 cycles, and it can be reused.
Claims
1. A polyacid cluster catalyst based on PAFs confined self-reduction, characterized in that, The polyacid clusters were prepared by impregnation method by loading them into the pores of PAFs; wherein the PAFs are porous frameworks containing viologen-like cationic groups; and the framework of the polyacid clusters is anionic.
2. The polyacid cluster catalyst based on PAFs confined self-reduction according to claim 1, characterized in that, The polyacid clusters are Keggin-type phosphomolybdic acid.
3. The polyacid cluster catalyst based on PAFs confined self-reduction according to claim 2, characterized in that, The PAFs are viologen-type cationic PAF-C2 with a pore size greater than 1 nm.
4. The method for preparing a polyacid cluster catalyst based on PAF confined self-reduction according to claim 3, characterized in that, Includes the following steps: S1. Preparation of viologen-based cationic PAF-C2 under nitrogen atmosphere protection; S2. Phosphomolybdic acid is pre-dissolved in deionized water, and then PAF-C2 is added. After the reaction is complete, the mixture is centrifuged, washed, dried, and ground to obtain a polyacid cluster catalyst.
5. The method for preparing a polyacid cluster catalyst based on PAFs confined self-reduction according to claim 4, characterized in that, In step S2, the mass ratio of phosphomolybdic acid to PAF-C2 is (0.33~2):
1.
6. The method for preparing a polyacid cluster catalyst based on PAF confined self-reduction as described in claim 4, characterized in that, In step S2, the temperature for complete reaction is room temperature, and the reaction time is 48–72 hours.
7. The application of a polyacid cluster catalyst based on PAFs confined self-reduction according to any one of claims 1-3, characterized in that, The polyacid cluster catalyst is used as a photocatalyst to catalyze the degradation of tetracycline pollutants in water.
8. The catalytic application of the polyacid cluster catalyst based on PAFs confined self-reduction according to claim 7, characterized in that, In water bodies, the concentration of tetracycline solution is 8-15 mg / L, and the pH range of the water body is 5-8.