A bifunctional heterojunction photocatalyst and a preparation method and application thereof
By growing CsPbBr3 nanocrystals in ZIF-8 channels to form S-shaped heterojunctions, a stable bifunctional catalyst was prepared, which solved the problems of instability of halide perovskite catalysts and their inability to simultaneously degrade tetracycline and inhibit bacteria, thus achieving a highly efficient water remediation effect.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JIANGSU UNIV OF SCI & TECH
- Filing Date
- 2026-04-09
- Publication Date
- 2026-07-03
AI Technical Summary
Halogenated perovskite catalysts are unstable and cannot effectively degrade tetracycline in water and inhibit bacteria. Furthermore, existing catalysts cannot simultaneously treat chemical and biological pollutants.
By growing CsPbBr3 nanocrystals inside and on the surface of the metal-organic framework ZIF-8 to form an S-shaped heterojunction, and optimizing the mass ratio of CsPbBr3 to ZIF-8 to 60:40, a bifunctional heterojunction catalyst was prepared and loaded onto a porous support to form an immobilized water remediation catalyst.
It significantly improves the stability and antibacterial properties of the catalyst, achieving a tetracycline degradation efficiency of 99.6% and an antibacterial rate of 99%. It also maintains high catalytic activity in actual water bodies, solving the problem that single-function materials cannot simultaneously treat chemical and biological pollution.
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Figure CN122321956A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of photocatalytic materials and environmental pollution control technology, and specifically relates to a bifunctional heterojunction photocatalyst, its preparation method and application. Background Technology
[0002] In recent years, antibiotics, as an emerging class of pollutants, have attracted worldwide attention due to their potential negative impacts on natural ecosystems, particularly the development of antibiotic resistance in pathogens. Tetracycline (TC), due to its widespread use in medicine and aquaculture, is commonly found in water bodies as a residue. Traditional wastewater treatment processes suffer from drawbacks such as requiring secondary treatment and incurring high costs. Therefore, the use of green and environmentally friendly photocatalytic methods to degrade tetracycline has become a research hotspot.
[0003] Halide perovskites (such as CsPbBr3) are an emerging optoelectronic material with characteristics such as high extinction coefficient, wide light absorption range, and long charge diffusion length, showing great potential in the field of photocatalysis. However, the instability of halide perovskites to their external environment (such as water, light, and heat) significantly affects their performance. In addition, bacteria in water bodies can cause microbial pollution, accelerate the decomposition of organic matter, and may spread drug-resistant genes, thus threatening aquatic ecological safety and human health. At the same time, bacteria and their secreted extracellular polymers can easily adsorb and cover the catalyst surface, causing active site shielding, mass transfer obstruction, and decreased catalytic performance.
[0004] In summary, halide perovskite catalysts are unstable, and existing catalysts can only degrade organic pollutants in water, without inhibiting bacteria in the water. Summary of the Invention
[0005] Objectives of the Invention: The first objective of this invention is to provide a bifunctional heterojunction catalyst that improves the stability of halide perovskites and achieves both pollutant degradation and antibacterial effects; the second objective of this invention is to provide a method for preparing the bifunctional heterojunction catalyst; the third objective of this invention is to provide an immobilized water remediation catalyst containing the bifunctional heterojunction catalyst; and the fourth objective of this invention is to provide applications of the bifunctional heterojunction catalyst or the immobilized water remediation catalyst.
[0006] Technical solution: The bifunctional heterojunction catalyst of the present invention comprises a metal-organic framework ZIF-8 and CsPbBr3 nanocrystals grown inside and on the surface of the pores of ZIF-8 to form an S-type heterojunction, wherein the mass ratio of CsPbBr3 to ZIF-8 is 6~14:6; the catalyst has a rhombic dodecahedral crystal structure.
[0007] Introducing ZIF-8 forms a heterojunction between CsPbBr3 and ZIF-8. The catalytic activity initially increases and then decreases with increasing ZIF-8 mass. At a CsPbBr3 to ZIF-8 mass ratio of 60:40, the optimal balance is achieved between the confinement protection of CsPbBr3 by the ZIF-8 pore structure and the charge separation efficiency of the S-type heterojunction at the interface, resulting in a catalyst with maximum photocatalytic degradation and antibacterial activity.
[0008] More preferably, the mass ratio of CsPbBr3 to ZIF-8 is 9~14 : 6.
[0009] The preparation method of the bifunctional heterojunction catalyst of the present invention includes the following steps:
[0010] (1) Preparation of ZIF-8 powder;
[0011] (2) Dissolve the lead source, cesium source and ZIF-8 powder obtained in step (1) in a polar solvent, add surface ligands and stir to obtain a precursor solution, then add an antisolvent to precipitate the precipitate, centrifuge, wash and dry to obtain CsPbBr3@ZIF-8 catalyst powder.
[0012] Preferably, the surface ligands are oleic acid and oleylamine.
[0013] Preferably, the solvent for the machine is N,N-dimethylformamide, and the antisolvent is toluene.
[0014] The immobilized water remediation catalyst of the present invention is a bifunctional heterojunction catalyst of the present invention loaded on a porous support, wherein the porous support is a polyurethane sponge or a loofah.
[0015] Preferably, the bifunctional heterojunction catalyst is loaded onto a porous support using an impregnation-ultrasound method, specifically: the bifunctional heterojunction catalyst powder is dispersed in a solvent, a porous support material is added, and the mixture is ultrasonically treated and then dried to obtain an immobilized photocatalyst.
[0016] Preferably, the ultrasonic treatment time is 30-50 min and the drying temperature is 50-70℃.
[0017] The application of the bifunctional heterojunction catalyst or the immobilized water remediation catalyst described in this invention in the photocatalytic degradation of antibiotic pollutants in water and / or the inhibition of bacteria in water.
[0018] Preferably, the antibiotic contaminant is a tetracycline antibiotic.
[0019] Preferably, the bacteria are Gram-positive and Gram-negative bacteria. More preferably, the bacteria are Staphylococcus aureus and Escherichia coli.
[0020] Invention Mechanism:
[0021] The construction of the S-shaped heterojunction effectively promoted charge separation. Compared with pure CsPbBr3, the optimized CZ-40 composite material achieved a TC degradation efficiency of 99.6% within 120 min, significantly outperforming the single component. Photoelectric testing and band structure analysis showed that an S-shaped heterojunction was formed between CsPbBr3 and ZIF-8, with a built-in electric field driving the directional migration of photogenerated carriers and effectively suppressing electron-hole recombination. Multiple active species synergistically participated in the degradation process. Free radical capture experiments confirmed that ·OH, ·O2⁻, and h+ in the CZ-40 system all significantly contributed to TC degradation, exhibiting a multi-pathway synergistic oxidation mechanism. This contrasts sharply with the single-pathway ·OH-dominated system in the CU-10 system in Chapter 2, revealing the regulatory role of different intrinsic properties of MOFs on the distribution of active species.
[0022] The composite material exhibits excellent photocatalytic degradation and antibacterial properties. CZ-40 showed an inhibition rate of 99% against both Escherichia coli and Staphylococcus aureus. Its antibacterial activity mainly stems from the oxidative damage to bacterial cell membranes caused by reactive oxygen species generated under light, as well as the Zn content in the ZIF-8 backbone. 2+ The material exhibits potential antibacterial properties. This multifunctional characteristic expands its application prospects in fields such as advanced drinking water treatment and medical wastewater purification.
[0023] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The present invention improves the degradation effect of the catalyst on tetracycline antibiotics by growing CsPbBr3 inside and on the surface of ZIF-8 channels to form an S-shaped heterojunction, and has strong antibacterial properties; (2) The catalyst with a mass ratio of CsPbBr3 to ZIF-8 of 60:40 has a degradation efficiency of up to 99.6% for tetracycline and an antibacterial rate (Staphylococcus aureus and Escherichia coli) of 99%; (3) The catalyst preparation method of the present invention is simple and easy to industrialize; (4) The immobilized water remediation catalyst is obtained by using polyurethane sponge or loofah as a macroscopic carrier. Through the "synthesis first and then loading" process, the destruction of the carrier structure by in-situ synthesis is avoided. After the catalyst is recycled 5 times, the removal rate is still above 77%, which solves the problem of difficult recovery of powdered catalysts; (5) The catalyst of the present invention can simultaneously degrade antibiotics and inhibit bacteria in water when used for water treatment, which solves the problem that single-function materials cannot treat chemical pollution and biological pollution at the same time; (6) The immobilized water remediation catalyst of the present invention has a pH It maintains stable catalytic activity in water bodies (tap water, lake water) within the range of 3~11 and in actual water bodies with common ion interference (tap water, lake water). Attached Figure Description
[0024] Figure 1The XRD patterns of the catalysts in Examples 1-3 are shown below.
[0025] Figure 2 The images show the FTIR spectra of the catalysts in Examples 1-3, with a for 500-4000 cm⁻¹ and b for 500-2000 cm⁻¹.
[0026] Figure 3 The images show the SEM morphology of the catalysts in Examples 1-3. a is the SEM image of CZ-30, b is the SEM image of CZ-40, c is the SEM image of CZ-50, and df is the TEM image of CZ-40.
[0027] Figure 4 The graphs show the performance of photocatalytic degradation of tetracycline. a) shows the effect of different catalysts; b) shows the effect of different CZ-40 dosages; c) shows the effect of TC concentration; d) shows the effect of pH; e) shows the effect of HA; f) shows the effect of inorganic anions; and g) shows the effect of cations.
[0028] Figure 5 This is a test diagram of a free radical capture experiment;
[0029] Figure 6 The photoelectrochemical performance test results are shown in graphs a for IT, b for EIS, c for Mott-Schottky of ZIF-8, and d for Mott-Schottky of CsPbBr3.
[0030] Figure 7 The band structure and PL spectrum are shown; a is PL, b is UV-vis; c is Tauc of CsPbBr3; d is Tauc of ZIF-8.
[0031] Figure 8 XPS spectra; a is Cs, b is Pb; c is Br; d is Zn;
[0032] Figure 9 This is a schematic diagram of the photocatalytic degradation mechanism;
[0033] Figure 10 The graphs show the antibacterial performance test results; a) is the control group for *E. coli*, b) is the experimental group for *E. coli* with ZIF-8, c) is the experimental group for *E. coli* with CsPbBr3, d) is the experimental group for *E. coli* with CZ-40, e) is the control group for *Staphylococcus aureus*, f) is the experimental group for *Staphylococcus aureus* with ZIF-8, g) is the experimental group for *Staphylococcus aureus* with CsPbBr3, and h) is the experimental group for *Staphylococcus aureus* with CZ-40.
[0034] Figure 11 Schematic diagram of the morphology and structure of sponge and loofah carrier;
[0035] Figure 12SEM images and elemental mapping images of the immobilized catalyst;
[0036] Figure 13 The graphs show the degradation performance and cycling stability of the immobilized catalyst, (a) the effect of different catalyst types ([TC]0 = 20 mg / L); (b) the cycling experiment ([TC]0 = 20 mg / L); and (c) the effect of different water qualities ([TC]0 = 20 mg / L). Detailed Implementation
[0037] The technical solution of the present invention will be further described below with reference to the embodiments.
[0038] Example 1
[0039] The bifunctional heterojunction photocatalyst of this invention is prepared by the following steps:
[0040] (1) Preparation of ZIF-8 powder
[0041] Dissolve 6 mmol of Zn(NO3)2·6H2O in 55 mL of methanol, and label this solution A. Mix 48 mmol of 2-methylimidazole with 55 mL of methanol, and label this solution B. Mix solutions A and B and stir for 8 h. After standing for 24 h, centrifuge at 8000 rpm for 10 min and wash five times with methanol. Finally, dry at 60 °C for 10 h, collect ZIF-8, and store in a sealed container at room temperature.
[0042] (2) Preparation of CsPbBr3@ZIF-8 composite photocatalyst powder (CZ-40)
[0043] 14.68 mg PbBr2, 8.52 mg CsBr, and 0.015 g of ZIF-8 prepared in step (1) were added to each mL of DMF. After complete dissolution, 50 μL of oleic acid and 50 μL of oleylamine were added rapidly (20 s), and the mixture was vigorously stirred (HA-4j multi-head magnetic stirrer, 600 rpm) for 2 h to obtain the precursor solution. Next, 20 mL of toluene was added rapidly (20 s) under vigorous stirring (HA-4j multi-head magnetic stirrer, 600 rpm) as an antisolvent. After the mixture changed from milky white to green, it was centrifuged at 8000 rpm for 10 minutes. Then, the precipitate was collected and washed with toluene. Finally, after drying in a fume hood, 0.0375 g of CsPbBr3@ZIF-8 composite photocatalyst powder was obtained, with a CsPbBr3 to ZIF-8 mass ratio of 60:40 (CZ-40).
[0044] Example 2
[0045] Based on Example 1, the amount of ZIF-8 added was changed to 0.0096 g, while the other conditions remained unchanged, to obtain CZ-30 (CsPbBr3 to ZIF-8 mass ratio 70:30).
[0046] Example 3
[0047] Based on Example 1, the amount of ZIF-8 added was changed to 0.0225 g, while the other conditions remained unchanged, to obtain CZ-50 (CsPbBr3 to ZIF-8 mass ratio 50:50).
[0048] Example 4
[0049] The preparation method of immobilized water remediation catalyst (HCZ-2) is as follows:
[0050] Commercially available polyurethane foam cubes (average side length 20.0 mm) were used as the support material. 0.0375 g of the CZ-40 composite photocatalyst powder prepared in Example 1 was dispersed in 10 mL of toluene to form a suspension. Three pieces of foam were added to this mixture, and 20 mL of toluene was rapidly added under vigorous stirring (HA-4j multi-head magnetic heating stirrer, 600 rpm), followed by ultrasonic treatment for 40 minutes to ensure uniform adsorption of the photocatalyst on the support surface. Finally, the loaded support was dried at 60 °C to obtain sample HCZ-2. The prepared solid catalyst is as follows... Figure 1 As shown.
[0051] Example 5
[0052] The preparation method of the immobilized water remediation catalyst (SCZ-2) is as follows:
[0053] Based on Example 4, natural loofah fiber (cut into cubes with a side length of 20.0 mm) was used as the carrier material to replace the polyurethane sponge, and CZ-40 was loaded onto the loofah to obtain sample SCZ-2.
[0054] Comparative Example 1
[0055] Preparation of one-step immobilized photocatalyst (HCZ-1):
[0056] (1) Preparation of ZIF-8 precursor solution: Dissolve 6 mmol Zn(NO3)2·6H2O in 55 mL methanol, and label it solution A. Mix 48 mmol dimethylimidazole with 55 mL methanol, and label it solution B. Mix solution A and solution B and stir for 8 h. The resulting solution is the ZIF-8 precursor solution.
[0057] (2) Preparation of CsPbBr3 precursor solution: Add 14.68 mg PbBr2, 8.52 mg CsBr, 50 μL of oleic acid and 50 μL of oleylamine to each milliliter of DMF, and stir vigorously for 2 h to obtain the precursor solution;
[0058] (3) The ZIF-8 precursor solution prepared in step (1) and the CsPbBr3 precursor solution prepared in step (2) were directly mixed with three polyurethane sponge cubic carrier materials (average side length 20.0 mm), and an antisolvent was added for in-situ synthesis loading.
[0059] Comparative Example 2
[0060] Preparation of one-step immobilized photocatalyst (SCZ-1): Based on Comparative Example 1, natural loofah fiber (cut into cubes with a side length of 20.0 mm) was used as the carrier material to replace the polyurethane sponge, while keeping other conditions unchanged, to obtain sample SCZ-1.
[0061] 1. Structural characterization
[0062] (1) Crystal structure analysis (XRD)
[0063] The crystal structures of the catalysts in Examples 1-3 were characterized, and the results are as follows: Figure 1 As shown.
[0064] Figure 1The XRD patterns of ZIF-8 showed characteristic diffraction peaks at 7.60°, 10.57°, 12.85°, 14.8°, 16.6°, and 18.12°, corresponding to the (011), (002), (112), (022), (013), and (222) planes of ZIF-8. The very sharp X-ray diffraction peaks are consistent with previous studies, indicating its phase purity and high crystallinity. In the XRD of the CsPbBr3@ZIF-8 composite, significant peaks of ZIF-8 appeared. In addition to the ZIF-8 diffraction peaks, diffraction peaks observed near 21.6°, 26.6°, 30.6°, and 38.6° were located on the (110), (111), (200), and (211) planes of cubic CsPbBr3, respectively.
[0065] (2) Analysis of chemical bonds and interfacial interactions (FTIR)
[0066] Figure 2 As shown in ab, the characteristic peaks in CZ-40 in the FTIR data are consistent with those observed in ZIF-8, further proving that the introduction of CsPbBr3 into the MOF has no effect on the original crystal structure of ZIF-8. CsPbBr3@ZIF-8 exhibits the characteristic absorption bands of the original ZIF-8 MOF, indicating that the perovskite nanocrystals are successfully bonded to the MOF matrix.
[0067] (3) Microscopic morphology analysis (SEM / TEM / HRTEM)
[0068] Figure 3 a~c reveals that the CsPbBr3@ZIF-8 composite material forms a regular, smooth, rhombic dodecahedral crystal morphology. The original ZIF-8 MOF has a crystal size in the range of 100~220 nm, exhibiting a narrow and uniform size distribution, with an average crystal size of approximately 140 nm. CsPbBr3@ZIF-8 retains the original surface morphology of the ZIF-8 molecular sieve and maintains the stability of ZIF-8 after the addition of CsPbBr3.
[0069] Figure 3 TEM and HRTEM images of d~f further confirm this; such as Figure 3 As shown in the dark selection region in e, CsPbBr3 is well embedded in the MOF matrix; Figure 3 The HRTEM image in f shows that the different lattice fringes have an interplane distance of 0.289 nm and belong to the (200) plane of cubic CsPbBr3.
[0070] 2. Degradation efficiency test of catalyst for tetracycline (TC)
[0071] Test Method: A suspension containing 20 mg of catalyst and 100 mL of a 20 mg / L tetracycline (TC) solution was stirred in the dark for 30 minutes to reach adsorption-desorption equilibrium. Then, the xenon lamp was turned on to initiate the degradation reaction. Every 20 minutes, 5 mL of the suspension was drawn using a syringe, filtered through a 0.22 μm filter to remove solid particles, and the concentration of TC in the reaction system was measured at 357 nm using a UV-Vis spectrophotometer. The test results are shown below. Figure 4 As shown in a
[0072] Figure 4 It can be seen that after adsorption equilibrium, the degradation rates of TC by CsPbBr3, ZIF-8, CZ-30, CZ-40 and CZ-50 are 41.3%, 77.6%, 80.8%, 99.6% and 83.7%, respectively. This indicates that the composite materials show better degradation effects than CsPbBr3 and ZIF-8 alone.
[0073] With a tetracycline concentration of 20 mg / L, the CZ-40 content was varied from 5 to 30 mg to determine the effect of CZ-40 content on the degradation rate. The test results are as follows: Figure 4 As shown in b.
[0074] Depend on Figure 4 As shown in b, the adsorption and degradation rates of TC both increase with the increase of CZ-40 catalyst dosage. This may be because the increase of CZ-40 catalyst dosage leads to an increase in adsorption sites and active sites, thereby continuously improving photocatalytic efficiency.
[0075] With a CZ-40 content of 20 mg, the tetracycline concentration was varied from 5 to 40 mg / L to test the effect of tetracycline concentration on the degradation rate. The test results are as follows: Figure 4 As shown in c.
[0076] Depend on Figure 4 As can be seen from c, the adsorption rate of TC by the CZ-40 composite material gradually decreases with increasing TC concentration. This is attributed to the limited number of adsorption sites provided by ZIF-8, which rapidly saturates at high concentrations. Notably, after 2 hours of photocatalytic reaction, the removal rate of TC by CZ-40 for concentrations of 5–30 mg / L remained above 90%. This result indicates that the composite material has significant advantages in terms of concentration applicability and is suitable for applications such as industrial wastewater treatment and environmental remediation.
[0077] With a tetracycline concentration of 20 mg / L and a CZ-40 content of 20 mg, the pH was adjusted to 3, 5, 7, 9, and 11 using HCl and NaOH. The effect of pH on the degradation rate was tested, and the test results are as follows. Figure 4 As shown in d.
[0078] from Figure 4 As shown in Figure d, the TC degradation efficiency first increases and then decreases with increasing pH, with the TC-HCl degradation efficiency being optimal at pH=7. However, the TC removal rate is still 76.6% at pH=3 and 59.9% at pH=11, indicating that CZ-40 has a certain resistance to pH shocks.
[0079] The effect of background ions on the degradation rate was tested using tetracycline at a concentration of 20 mg / L, CZ-40 at a concentration of 20 mg, and HA at concentrations ranging from 0.1 to 10 g / L. The test results are as follows: Figure 4 As shown in e.
[0080] from Figure 4 As can be seen from the results, HA significantly inhibits the degradation of TC, with the TC removal rate decreasing by 28.2% (10 g / L) within 120 min. This is because HA can remove active species and electrons from the photocatalytic system.
[0081] With a tetracycline concentration of 20 mg / L, a CZ-40 content of 20 mg, and 0.1 mM K... + Mg 2+ Ca 2+ Cl - NO3 - CO3 2- and SO4 2- The effect of background ions on the degradation rate was tested, and the test results are as follows: Figure 4 As shown in f~g.
[0082] from Figure 4 As can be seen from f~g, for common inorganic anions, Cl - NO3 - CO3 2- and SO4 2- The presence of [a substance] reduced its adsorption rate for TC to 57.8%, 53.7%, 36.2%, and 41.9% (61.8% in the blank group), respectively, and the removal rate to 72.8%, 70.8%, 62.1%, and 68.9% (99.6% in the blank group), respectively. [The text also mentions] cation Na. + K + Ca 2+ and Mg 2+ The degradation of TC was significantly inhibited, with the TC removal rate decreasing by 19.5%, 16.5%, 42.4%, and 30%, respectively. This is because the metal precipitates formed on the catalyst surface affected the degradation of TC.
[0083] 3. The key mechanism was verified through a free radical capture experiment, and the test method is as follows:
[0084] 1,4-Benzoquinone (BQ) was selected as the superoxide radical (•O2). - Quenching agent for active groups. Based on a tetracycline concentration of 20 mg / L and a catalyst concentration of 20 mg, 1 mM of p-benzoquinone was added, with all other conditions remaining unchanged.
[0085] tert-butanol (TBA) was selected as the quencher of hydroxyl radicals (•OH). With a tetracycline concentration of 20 mg / L and a catalyst concentration of 20 mg, 1 mM of tert-butanol was added, while other conditions remained unchanged.
[0086] Methanol (MeOH) was selected as the hole (h + The quencher was a tetracycline at a concentration of 20 mg / L and a catalyst of 20 mg, with 1 mM methanol added while keeping other conditions unchanged.
[0087] Test results are as follows Figure 5 As shown.
[0088] from Figure 5 As can be seen, the degradation rate of TC decreased to below 50% in the presence of TBA, BQ, and MeOH, which confirms the degradation effect of ·OH and ·O2. - and h + These are key active species in the TC degradation process. TBA had the greatest impact on the degradation efficiency, decreasing it to 29.9%. BQ's degradation efficiency decreased to 46.1%, and MeOH's decreased to 34.0%. This indicates that ·OH plays a major role in the degradation process, while ·O2... - and h + It plays a supporting role.
[0089] 4. Photoelectrochemical performance testing
[0090] Test Method: The photocurrent density curve (i–t) was measured using a three-electrode system on a CHI 760 electrochemical workstation with a 0.5 M Na₂SO₄ solution as the electrolyte. The working electrode was prepared as follows: 2 mg of catalyst powder was dispersed in 1 mL of ethanol, and 50 μL of naphthol was added to form a uniform suspension. This suspension was then coated onto the conductive surface of an ITO conductive glass substrate (1 cm × 2 cm) and dried in a vacuum oven at 60 °C. Test results are as follows: Figure 6 As shown.
[0091] from Figure 6 As can be seen from a, compared with the original ZIF-8 and CsPbBr3, the transient photocurrent response density of CZ-40 is significantly enhanced, indicating that photogenerated electron-hole pairs can be effectively generated and transferred between interfaces in the composite material. Furthermore, from Figure 6As can be seen from b, the radius of CZ-40 is smaller than that of ZIF-8 / CsPbBr3, indicating that CZ-40's easier electron transfer leads to its high photocatalytic performance. From Figure 6 As shown in diagrams c-d, both CsPbBr3 and ZIF-8 exhibit positive slopes in the Mott-Schottky plots, indicating that they are n-type semiconductors. Studies have shown that the flat-band potential of an n-type semiconductor can be approximated by its conduction band potential. The conduction band potentials of the prepared CsPbBr3 and ZIF-8 are -1.16 eV and -1.12 eV, respectively.
[0092] 5. Band structure and PL spectral analysis
[0093] from Figure 7 As can be seen from a, the fluorescence emission intensity of the CZ-40 sample is lower than that of the undoped CsPbBr3, indicating that electrons and holes at the CsPbBr3-ZIF-8 interface can be better separated and transferred. Figure 7 As can be seen in b, the UV-Vis diffuse reflectance spectrum of CsPbBr3 shows that its absorption edge is located at approximately 545 nm, indicating that CsPbBr3 not only responds to ultraviolet light but also absorbs some visible light. From Figure 7 As can be seen from diagrams c to d, the band gaps of CsPbBr3 and ZIF-8 calculated using the Tauc equation are 2.61 eV and 5.18 eV, respectively. Combining the band gap values obtained from UV-Vis diffuse reflectance spectroscopy, the calculated valence band potentials of CsPbBr3 and ZIF-8 are 2.61 eV and 4.06 eV, respectively.
[0094] 6. XPS spectral analysis
[0095] from Figure 8 As can be seen, in CsPbBr3, the peaks at 723.83 eV and 737.77 eV correspond to Cs3d5 / 2 and Cs3d3 / 2, respectively. Figure 8 a); the peaks at 137.83 eV and 142.67 eV correspond to Pb 4f7 / 2 and Pb 4f5 / 2, respectively. Figure 8 b); The two peaks of Br 3d are located at 67.73 eV and 68.69 eV, respectively, corresponding to Br 3d5 / 2 and Br 3d5 / 2 ( Figure 8 c). After recombination, the binding energies of Cs 3d, Br 3d, and Pb 4f shift towards lower energies. Furthermore, for ZIF-8, the two peaks of Zn 2p are located at 1021.15 eV and 1044.33 eV, corresponding to Zn 2p³ / 2 and Zn 2p¹ / 2, respectively (see [link to relevant documentation]). Figure 8d), but in composite materials, these binding energies shift towards higher energies. These changes in binding energy indicate the presence of charge transfer from ZIF-8 to CsPbBr3.
[0096] 7. Catalytic Mechanism Analysis
[0097] from Figure 9 As can be seen from the above results, the final catalytic mechanism is given. The visible light photocatalytic degradation process of TC is as follows: Under visible light excitation, e-—h in CZ-40 + The electrons can be effectively separated. Subsequently, the separated electrons will migrate from the CB of CsPbBr3 to the CB of ZIF-8. Simultaneously, h+ will also migrate from the VB of CsPbBr3 to the VB of ZIF-8. This photogenerated carrier movement conforms to the photocatalytic process of a type II heterojunction. The electrons enriched in the CB of CsPbBr3 can utilize their reducing properties to reduce O2 adsorbed on the catalyst surface to ·O2. - However, due to the limitations of band structure, the h-band enriched in ZIF-8 is limited by the band structure. + ·OH cannot be generated. In the CsPbBr3@ZIF-8 system, TC can only be reacted with h+ and ·O2. - Degradation occurs, therefore the type II heterojunction does not conform. Based on band structure analysis, the conduction band position of CsPbBr3 (-1.16 eV) is higher than that of O2 / ·O2. - Its standard redox potential (-0.33 eV) is more negative, therefore its conduction band electrons can effectively reduce O2 to •O2. - The valence band position of ZIF-8 (4.06 eV) is higher than that of OH / OH. - Its oxidation potential (+1.99 eV) is corrected, therefore its valence band holes can oxidize OH. - The generation of •OH indicates that photogenerated electrons and holes are enriched in the conduction band of CsPbBr3 and the valence band of ZIF-8, respectively, resulting in spatial separation, consistent with the characteristics of an S-type heterojunction. This mechanism perfectly explains the presence of •OH and •O2 in the free radical capture experiment. - and h + Results of experiments conducted jointly.
[0098] 8. Antibacterial performance test
[0099] Laboratory-preserved Staphylococcus aureus and Escherichia coli were cultured at 37 °C with constant shaking for 24 h to obtain bacterial stock solutions. A catalyst was added to sterile water and ultrasonically dispersed to prepare an antibacterial stock solution. The bacterial and antibacterial stock solutions were mixed, incubated at 37 °C with constant shaking for 2 h, spread on plates, and cultured for 24 h before counting. The inhibition rate (%) was calculated as follows: (Number of colonies in the control group - Number of colonies in the experimental group) / Number of colonies in the control group × 100%. The test results are as follows: Figure 10 As shown.
[0100] Depend on Figure 10 The antibacterial test results show that CZ-40 achieved an inhibition rate of 99% against both Escherichia coli and Staphylococcus aureus, significantly superior to other samples. This excellent antibacterial performance may stem from two aspects: firstly, the reactive oxygen species (such as •O2) generated during the photocatalytic process. - Oxidative damage to bacterial cell membranes caused by (and •OH); secondly, the Zn in the ZIF-8 backbone. 2+ The sustained release may have a synergistic inhibitory effect on bacterial growth.
[0101] 9. Characterization and Practicality Verification of Immobilized Water Remediation Catalysts
[0102] (1) Catalyst characterization
[0103] SEM images of HCZ-2 and SCZ-2 are shown below. Figure 12 As shown in a and f, the catalyst was successfully loaded and uniformly distributed on the three-dimensional porous framework of the support. EDS elemental mapping ( Figure 12 (b~e or g~j) further revealed the uniform distribution of characteristic elements (Zr, Cs, Pb, Br) in the sponge and loofah substrates, confirming the successful and uniform loading of the photocatalyst, indicating the formation of a stable and uniformly loaded immobilized catalyst.
[0104] (2) Evaluation of catalyst performance and application
[0105] Test method: The catalysts (3 cubes of 20.0 mm each) prepared in Examples 4-5 h and Comparative Examples 1-2, along with a suspension of 100 mL of a 20 mg / L tetracycline (TC) solution, were stirred in the dark for 30 minutes to reach adsorption-desorption equilibrium. Subsequently, a xenon lamp was turned on to initiate the degradation reaction. Every 20 minutes, 5 mL of the suspension was drawn using a syringe, filtered through a 0.22 μm filter to remove solid particles, and the concentration of TC in the reaction system was measured at 357 nm using a UV-Vis spectrophotometer. The test results are as follows: Figure 13 As shown in a~c.
[0106] By systematically comparing the effects of support type and synthesis strategy on catalytic performance, HCZ-2 and SCZ-2 achieved removal rates of 84.25% and 59.51%, respectively, while HCZ-1 and SCZ-1 achieved removal rates of 71.81% and 48.55%, respectively. This performance difference may be attributed to interference from the support during in-situ synthesis, which hindered the ordered growth of the CsPbBr3@ZIF-8 composite material. Furthermore, compared to sponge-based samples, loofah-supported samples generally performed worse (this may be due to the uneven catalyst distribution caused by the inhomogeneous pore structure of the loofah).
[0107] It is worth noting that after five consecutive reaction cycles, HCZ-2 and SCZ-2 still maintained removal efficiencies of 77.68% and 50.21%, respectively. Figure 13 (b) demonstrated good recyclability and stability.
[0108] Tests were conducted in a real-world environment using 100 mL of tap water and lake water (Haiyun Lake, Jiangsu University of Science and Technology). The CZ-40 catalyst mass was 20 mg, and the pollutant concentration was 20 mg / L. The test results are as follows: Figure 13 As shown in c.
[0109] Depend on Figure 13 c shows that their catalytic performance fluctuates within 10%. Figure 13 c) demonstrates strong environmental adaptability. In summary, the HCU-2 and SCU-2 composite catalytic system of this invention exhibits high efficiency, recyclability, and stability, and has broad application prospects in practical aquatic environments, thus laying a solid foundation for large-scale water treatment.
Claims
1. A bifunctional heterojunction catalyst characterized in that, The catalyst comprises a metal-organic framework ZIF-8 and CsPbBr3 nanocrystals grown inside and on the surface of the ZIF-8 pores, forming an S-shaped heterojunction, wherein the mass ratio of CsPbBr3 to ZIF-8 is 6~14:6; the catalyst has a rhombic dodecahedral crystal structure.
2. The bifunctional heterojunction catalyst of claim 1, wherein, The mass ratio of CsPbBr3 to ZIF-8 is 9~14 :
6.
3. A process for the preparation of a bifunctional heterojunction catalyst according to claim 1 or 2, characterized in that, Includes the following steps: (1) Preparation of ZIF-8 powder; (2) Dissolve the lead source, cesium source and ZIF-8 powder obtained in step (1) in a polar solvent, add surface ligands and stir to obtain a precursor solution, then add an antisolvent to precipitate the precipitate, centrifuge, wash and dry to obtain CsPbBr3@ZIF-8 catalyst powder.
4. The method for preparing the bifunctional heterojunction catalyst according to claim 3, characterized in that, The surface ligands are oleic acid and oleylamine.
5. The method for preparing the bifunctional heterojunction catalyst according to claim 3, characterized in that, The solvent for this model is N,N-dimethylformamide, and the antisolvent is toluene.
6. An immobilized water remediation catalyst, characterized in that, The bifunctional heterojunction catalyst of claim 1 or 2 is loaded onto a porous support, wherein the porous support is a polyurethane sponge or a loofah.
7. The immobilized water remediation catalyst according to claim 6, characterized in that, The impregnation-ultrasound method is used to disperse the bifunctional heterojunction catalyst powder in a solvent, add a porous support material, and then dry it after ultrasonic treatment to obtain an immobilized water remediation catalyst.
8. The application of the bifunctional heterojunction catalyst of claim 1 or the immobilized water remediation catalyst of claim 6 in the photocatalytic degradation of antibiotic pollutants in water and / or inhibition of bacteria in water.
9. The application according to claim 8, wherein the antibiotic contaminant is a tetracycline antibiotic.
10. The application according to claim 8, wherein the bacteria are Gram-positive and Gram-negative bacteria.