Piezoelectric dissimilar metal co-doped titanium-oxygen cluster compound as well as preparation method and application thereof

Abstract

The invention discloses a piezoelectric dissimilar metal co-doped titanium-oxygen cluster compound as well as a preparation method and application thereof, and relates to the field of materials. The molecular formula of the piezoelectric dissimilar metal co-doped titanium-oxygen cluster compound is H2Ti26Pb10 (mu4-O) 4 (mu3-O) 34 (mu2-O) 6Bz38. 6MeCN. 2 (C4H9ON), and the molecular formula of the piezoelectric dissimilar metal co-doped titanium-oxygen cluster compound is Ti26Pb10, and the molecular formula of the piezoelectric dissimilar metal co-doped titanium-oxygen cluster compound is Ti26Pb10. Wherein mu3-O represents a three-bridged O atom, mu2-O represents a two-bridged O atom, mu4-O represents a four-bridged O atom, Bz represents a benzoic acid ligand, MeCN represents an acetonitrile solvent molecule, and C4H9ON represents a morpholine solvent molecule. The adopted preparation method is simple, raw materials are easy to obtain, aftertreatment is simple, pollution is little, and the green and environment-friendly requirements are met. The piezoelectric dissimilar metal co-doped titanium-oxygen cluster compound prepared by the preparation method disclosed by the invention is relatively high in stability, has piezoelectric activity and has a relatively high degradation rate on antibiotics.

Description

Technical Field

[0001] The present invention relates to the fields of materials and photocatalytic degradation of organic pollutants, and in particular to a piezoelectric heterometallic co-doped titanium oxide cluster compound and a preparation method and application thereof. Background Art

[0002] In recent years, efficient treatment technologies for environmental pollutants have attracted much attention, among which photocatalytic materials have become a research hotspot due to their green and sustainable characteristics. Titanium oxide clusters, as a type of metal oxide cluster material with adjustable structure and rich surface active sites, have shown potential in the field of photocatalytic degradation of organic pollutants due to their excellent photogenerated carrier transport ability and functional modification characteristics. However, traditional titanium oxide clusters are limited by a single metal center and a low nuclear number structure. Their photoresponse range is narrow and the carrier recombination rate is high, making it difficult to break through the catalytic efficiency. In addition, the degradation ability of a single photocatalytic system for complex pollutants is limited, and there is an urgent need to improve performance through a multi-mechanism synergistic strategy.

[0003] Piezoelectric catalysis technology induces a piezoelectric polarization field through mechanical vibration of the material, which can drive carrier separation and participate in redox reactions, providing a new approach to photocatalytic efficiency enhancement. However, existing piezoelectric materials (such as ceramics and polymers) often have problems such as complex preparation processes, insufficient piezoelectric active sites, or poor compatibility with photocatalysis. In recent years, metal oxide clusters have been regarded as ideal candidates for new piezoelectric catalytic materials due to their atomic-level structural precision and controllable electronic properties. However, how to give them a high-nuclear heterometallic structure, stable piezoelectric response, and efficient catalytic activity through rational design remains a challenge.

[0004] Heterometallic co-doping is an effective strategy for regulating the electronic structure and surface properties of materials. The introduction of heavy metals such as lead (Pb) can enhance the polarization effect of the material and broaden the light absorption range, but the synthesis of high-nuclear heterometallic titanium oxide clusters is limited by difficulties such as coordination competition between metals, core-shell structure stability, and ligand steric hindrance. Existing methods mostly use a single template or simple ligand, which makes it difficult to achieve the directed assembly of high-nuclear heterometallic clusters, and the research on their piezoelectric-photocatalytic synergistic mechanism is still blank. Therefore, developing a simple and structurally controllable synthesis method for heterometallic titanium oxide clusters and revealing their piezoelectric and photocatalytic synergistic enhancement mechanism are of great significance to promote the innovative development of environmental catalytic materials. Summary of the Invention

[0005] In view of the above shortcomings of the prior art, the object of the present invention is to provide a piezoelectric heterometallic co-doped titanium oxide cluster and its preparation method and application, which can effectively solve the problems existing in the prior art.

[0006] In order to achieve the above purpose or other purposes, the present invention is implemented through the following technical solutions.

[0007] A piezoelectric heterometallic co-doped titanium oxide cluster compound, wherein the molecular formula of the piezoelectric heterometallic co-doped titanium oxide cluster compound is H2Ti 26 Pb 10 (μ4-O)4(μ3-O) 34 (μ2-O)6Bz 38 ·6MeCN·2(C4H9ON), abbreviated as Ti 26 Pb 10 ;

[0008] Among them, μ3-O represents a triple-bridged O atom, μ2-O represents a double-bridged O atom, μ4-O represents a quadruple-bridged O atom, Bz represents a benzoic acid ligand, MeCN represents an acetonitrile solvent molecule, and C4H9ON represents a morpholine solvent molecule.

[0009] The piezoelectric heterometallic co-doped titanium oxide cluster of the present invention has a skeleton composed of 26 titanium atoms symmetrically assembled using binuclear titanium oxide units, 10 Pb 2+ It is anchored to the Ti–O framework with differentiated coordination modes (2 embedded in the skeleton and 8 exposed on the surface); 26 Ti(IV) and 10 Pb(II) are bridged by μ2-O, μ3-O, and μ4-O to form a core-shell structure, and the periphery is stabilized by 38 benzoic acid ligands (Bz), which are bound to the metal core surface in a monodentate or bidentate coordination mode; the number of μ2-O, μ3-O, and μ4-O bridging oxygens are 6, 34, and 4, respectively.

[0010] The crystal system of the piezoelectric heterometallic co-doped titanium oxide cluster compound of the present invention is triclinic, the space group is P-1, and the unit cell parameter a is b is c is α is 66.4°, β is 70.6°, γ is 63.4°, and the unit cell volume is

[0011] The size of the piezoelectric heterometallic co-doped titanium oxide cluster compound of the present invention is 0.5 mm to 1.2 mm.

[0012] The method for preparing the piezoelectric heterometallic co-doped titanium oxide cluster comprises the following steps: 1) adding lead acetate trihydrate, benzoic acid, and piperazine to acetonitrile as a solvent and stirring and mixing them uniformly to obtain a suspension; adding morpholine and acetic acid to the suspension and continuing to stir and mix them uniformly;

[0013] 2) adding titanium tetraisopropoxide to the reaction system obtained in step 1), stirring evenly under sealing, and carrying out heat-insulating reaction; after the reaction is completed, washing and vacuum drying are performed to obtain the target product.

[0014] In one example of the present invention, the reaction temperature is 95° C.-105° C., and the reaction time is 14 days-21 days.

[0015] In one example of the present invention, the molar ratio of titanium tetraisopropoxide, lead acetate trihydrate, acetic acid, morpholine, piperazine and benzoic acid is (1-3):(1-2):(1-2):(1-2):(1-2):(9-12).

[0016] In one example of the present invention, the molar ratio of the solvent acetonitrile to titanium tetraisopropoxide is (33-35):1.

[0017] In one example of the present invention, acetonitrile is used as a solvent for washing after the reaction is completed.

[0018] In one example of the present invention, the vacuum drying temperature is 20° C.-60° C., and the vacuum drying time is 6 h-18 h.

[0019] The present invention also provides the use of the piezoelectric heterometallic co-doped titanium oxide cluster compound in the piezoelectric-photosynergistic catalytic degradation of antibiotics.

[0020] Furthermore, a piezoelectric heterometallic co-doped titanium oxide cluster is added to the antibiotic and reacted in the dark. After the reaction reaches adsorption equilibrium, the reaction system is placed in a reactor equipped with an ultraviolet lamp and ultrasound, and reacts under the combined action of ultrasound and light.

[0021] Preferably, the antibiotic is selected from one of tetracycline, rhodamine B, methylene blue and penicillin.

[0022] Preferably, the molar ratio of the piezoelectric heterometallic co-doped titanium oxide cluster compound to the antibiotic is (1-3):(1-3).

[0023] Preferably, the wavelength of the ultraviolet lamp is 360nm to 380nm, the ultrasonic power is 120W to 150W, and the frequency is 30kHz to 50kHz.

[0024] The present invention provides a piezoelectric heterometallic co-doped titanium oxide cluster and its preparation method. The piezoelectric heterometallic co-doped titanium oxide cluster is synthesized using a one-step solvothermal method. The raw materials are mixed and then heated in a solvent to react. The piezoelectric heterometallic co-doped titanium oxide cluster is obtained. The preparation method is simple, and the raw materials are readily available, making it easy to industrialize. Furthermore, the preparation method employs simple post-processing, reduces pollution, and meets environmental protection requirements.

[0025] The piezoelectric heterometallic co-doped titanium oxide cluster prepared by the preparation method of the present invention has a titanium oxide core number exceeding Ti 20The piezoelectric heterometallic co-doped titanium oxide cluster compound of the present invention has high stability. After being recycled four times as a catalyst in pollutant degradation experiments, the structure of the piezoelectric heterometallic co-doped titanium oxide cluster compound remained unchanged, and the catalytic efficiency decreased by less than 10% after four cycles. The piezoelectric heterometallic co-doped titanium oxide cluster compound of the present invention also has piezoelectric activity. When used in the piezoelectric-photocatalytic synergistic degradation of antibiotics such as tetracycline, rhodamine B, methylene blue, and penicillin, its piezoelectric slope is not less than 5mV / V, and the degradation efficiency of 22ppm tetracycline under ultraviolet light (wavelength 365nm) is more than 50% (within 1 hour). BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a crystal photograph of the piezoelectric heterometallic co-doped titanium oxide cluster obtained in Example 1 (the crystal photograph was obtained by microscopy).

[0027] Figure 2 1 is the crystal structure of the single crystal of the piezoelectric heterometallic co-doped titanium oxide cluster obtained in Example 1 (for clarity, hydrogen is ignored).

[0028] Figure 3 This is the infrared spectrum of the piezoelectric heterometallic co-doped titanium oxide cluster obtained in Example 1.

[0029] Figure 4 1 is a powder X-ray diffraction (PXRD) spectrum of the piezoelectric heterometallic co-doped titanium oxide cluster obtained in Example 1.

[0030] Figure 5 This is the ultraviolet diffuse reflectance spectrum of the piezoelectric heterometallic co-doped titanium oxide cluster obtained in Example 1.

[0031] Figure 6 These are the butterfly curve and phase hysteresis curve of the piezoelectric heterometallic co-doped titanium oxide cluster obtained in Example 1.

[0032] Figure 7 This is a Kelvin probe force microscopy (KPFM) image of the piezoelectric heterometallic co-doped titanium oxide cluster obtained in Example 1.

[0033] Figure 8a The figure is a comparison chart of the overall kinetics of tetracycline degradation of Application Example 1, Comparative Example 3, and Comparative Example 4.

[0034] Figure 8b It is a curve diagram of the total degradation rate of tetracycline in Application Example 1, Comparative Example 3, and Comparative Example 4.

[0035] Figure 9 The piezoelectric heterometallic co-doped titanium oxide cluster Ti prepared in Example 1 26 Pb 10 During the piezoelectric photocatalytic degradation of tetracycline, the degradation rates were compared after four repeated experiments.

[0036] Figure 10a The catalyst Ti is the piezoelectric heterometallic co-doped titanium oxide cluster obtained in Example 1 and has participated in four piezoelectric photocatalytic degradation reactions of tetracycline. 26 Pb 10 Infrared spectrum comparison chart.

[0037] Figure 10b The catalyst Ti is the piezoelectric heterometallic co-doped titanium oxide cluster obtained in Example 1 and has participated in four piezoelectric photocatalytic degradation reactions of tetracycline. 26 Pb 10 XRD spectrum comparison diagram.

[0038] Figure 11 The figure is a comparison chart of the tetracycline degradation kinetics of Application Example 1 and Comparative Example 5.

[0039] Figure 12a The graph is a graph showing the total degradation kinetics of Rhodamine B in Application Example 2, Comparative Example 6, and Comparative Example 7.

[0040] Figure 12b This is the total rate curve of Rhodamine B for Application Example 2, Comparative Example 6, and Comparative Example 7.

[0041] Figure 13a The total degradation kinetic curves of methylene blue in Application Example 3, Comparative Example 8, and Comparative Example 9 are shown.

[0042] Figure 13b This is a graph of the total degradation rate of methylene blue for Application Example 3, Comparative Example 8, and Comparative Example 9.

[0043] Figure 14 The kinetic curves of the total degradation of penicillin in Application Example 4, Comparative Example 10, and Comparative Example 11 are shown. DETAILED DESCRIPTION

[0044] The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following examples and the features in the examples can be combined with each other unless they conflict. It should also be understood that the terms used in the examples of the present invention are for the purpose of describing specific embodiments, not for the purpose of limiting the scope of protection of the present invention. The test methods for which specific conditions are not specified in the following examples are generally carried out under conventional conditions or under the conditions recommended by the manufacturers.

[0045] It should be noted that the terms such as "upper", "lower", "left", "right", "middle" and "one" cited in this specification are only for the convenience of description and are not used to limit the scope of implementation of the present invention. Changes or adjustments to their relative relationships should be regarded as the scope of implementation of the present invention without substantially changing the technical content.

[0046] The technical scheme of the present invention is described in detail below through several specific examples and comparative examples. Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by conventional methods in the art. Unless otherwise specified, the detection methods used in the examples of the present invention are conventional detection methods in the industry.

[0047] Since the structure of the antibiotics will be destroyed as the catalytic reaction proceeds in the piezoelectric-photosynergistic catalytic degradation of antibiotics by piezoelectric heterometallic co-doped titanium oxide clusters, the absorbance detected at a specific wavelength using an ultraviolet spectrophotometer will show a gradually decreasing trend. Therefore, the degradation rate can be calculated by measuring the absorbance in different reaction time periods according to the degradation rate calculation formula.

[0048] The calculation method of the degradation rate in the embodiment of the present invention is based on the Lambert-Beer law (A=εlc):

[0049] Degradation rate (%) = (C0-C t ) / C0=(A0-A t ) / A0

[0050] Where A represents absorbance, ε is the molar absorptivity, l is the optical path length, and c is the molar concentration of the solution; C0 and A0 are the initial concentration and initial absorbance, respectively. t and A t are the concentration and absorbance at time t.

[0051] Example 1

[0052] A method for preparing a piezoelectric heterometallic co-doped titanium oxide cluster comprises the following steps:

[0053] 1.46 g of benzoic acid, 0.38 g of lead acetate trihydrate, and 100 mg of piperazine were added sequentially to a vial. 4 mL of acetonitrile was added as solvent. The mixture was premixed on a magnetic stirrer (800 rpm) for 5 minutes to form a white suspension. Subsequently, 100 μL of morpholine and 100 μL of glacial acetic acid were added sequentially to the system. Stirring was continued under air for 10 minutes to thoroughly mix the suspension.

[0054] 2) 0.92 mL of titanium tetraisopropoxide was added to the reaction system, and the reaction system changed from a suspension to a clear solution. The reaction vessel was temporarily sealed and placed on a magnetic stirrer (800 rpm) for mixing for 10 minutes. After thorough mixing, the mixture was moved to an oven for further crystallization reaction at 100°C for 14 days.

[0055] 3) After the reaction, colorless transparent block crystals were observed at the bottom of the vial. They were washed three times with acetonitrile and then dried in a vacuum oven at 30°C for 12 hours. The crystals were collected to obtain the target product H2Ti 26 Pb 10 (μ4-O)4(μ3-O) 34 (μ2-O)6Bz 38 ·6MeCN·2(C4H9ON).

[0056] Example 2

[0057] The difference between this embodiment and Example 1 is that the molar ratio of titanium tetraisopropoxide, lead acetate trihydrate, acetic acid, morpholine, piperazine and benzoic acid is 1:1:1:2:1:9, and the molar ratio of the solvent acetonitrile to titanium tetraisopropoxide is 33:1; the reaction temperature is 105°C, the reaction time is 14 days, the vacuum drying temperature is 60°C, and the vacuum drying time is 6 hours.

[0058] Example 3

[0059] The difference between this embodiment and Example 1 is that the molar ratio of titanium tetraisopropoxide, lead acetate trihydrate, acetic acid, morpholine, piperazine and benzoic acid is 1:2:1.5:1.5:2:10, and the molar ratio of the solvent acetonitrile to titanium tetraisopropoxide is 35:1; the reaction temperature is 95°C, the reaction time is 21 days, the vacuum drying temperature is 50°C, and the vacuum drying time is 8 hours.

[0060] Example 4

[0061] The difference between this embodiment and Example 1 is that the molar ratio of titanium tetraisopropoxide, lead acetate trihydrate, acetic acid, morpholine, piperazine and benzoic acid is 1:1.5:2:2:1.5:12, and the molar ratio of the solvent acetonitrile to titanium tetraisopropoxide is 34:1; the reaction temperature is 100°C, the reaction time is 18 days, the vacuum drying temperature is 20°C, and the vacuum drying time is 18 hours.

[0062] Application Example 1

[0063] 50 mg of the piezoelectric heterometallic co-doped titanium oxide cluster prepared in Example 1 was weighed and dispersed into 100 mL of a 22 ppm tetracycline aqueous solution. After the dark reaction for 30 min, the reaction system was placed in a reactor equipped with an ultrasound power of 150 W and a frequency of 40 kHz, and a 365 nm ultraviolet lamp. The reaction was carried out under the combined action of ultrasound and light. After the reaction started, the reaction solution was taken every 20 min, and the absorption peak intensity at 355 nm at different reaction time periods was detected and recorded using an ultraviolet spectrophotometer to determine the degradation rate of tetracycline until the tetracycline was completely degraded.

[0064] Application Example 2

[0065] The difference between this embodiment and Application Example 1 is that:

[0066] The catalyst piezoelectric heterometallic co-doped titanium oxide cluster was dispersed in 100 mL of a 10 ppm Rhodamine B solution. The molar ratio of the piezoelectric heterometallic co-doped titanium oxide cluster to Rhodamine B was 3:1, and other conditions remained unchanged.

[0067] Application Example 3

[0068] The difference between this embodiment and Application Example 1 is that:

[0069] The catalyst piezoelectric heterometallic co-doped titanium oxide cluster was dispersed in 100 mL of a 10 ppm methylene blue solution. The molar ratio of the piezoelectric heterometallic co-doped titanium oxide cluster to the methylene blue was 2:1, and other conditions remained unchanged.

[0070] Application Example 4

[0071] The difference between this embodiment and Application Example 1 is that:

[0072] The catalyst piezoelectric heterometallic co-doped titanium oxide cluster was dispersed in 100 mL of a 50 ppm penicillin solution. The molar ratio of the piezoelectric heterometallic co-doped titanium oxide cluster to penicillin was 1:3. The reaction was carried out for 200 minutes, and other conditions remained unchanged.

[0073] Application Example 5

[0074] The difference between this embodiment and Application Example 1 is that:

[0075] The catalyst piezoelectric heterometallic co-doped titanium oxide cluster was dispersed in 100 mL of a 50 ppm penicillin solution. The molar ratio of the piezoelectric heterometallic co-doped titanium oxide cluster to penicillin was 2:3. The reaction was carried out for 200 minutes, and other conditions remained unchanged.

[0076] Comparative Example 1

[0077] The difference between Comparative Example 1 and Example 1 is that:

[0078] Lead acetate trihydrate was not added, and other conditions were the same.

[0079] The reaction results showed that precipitation occurred in the reaction system, no crystals were precipitated, and the target product could not be obtained.

[0080] Comparative Example 2

[0081] The difference between Comparative Example 2 and Example 1 is that: no morpholine-piperazine template reagent is added in step 1). The results show that the reaction system is clear and transparent, but after the insulation time exceeds 21 days, no crystals are precipitated at the bottom of the reaction vessel, and the target product cannot be obtained.

[0082] Comparative Example 3

[0083] The difference between Comparative Example 3 and Application Example 1 is that:

[0084] The reaction was carried out only under the action of ultrasound, without light.

[0085] Comparative Example 4

[0086] The difference between Comparative Example 4 and Application Example 1 is that:

[0087] The reaction is carried out under the action of stirring and light, and ultrasound does not participate in assisting the reaction.

[0088] Comparative Example 5

[0089] The difference between Comparative Example 5 and Application Example 1 is that:

[0090] The catalyst used is the common piezoelectric material PbTiO3.

[0091] Comparative Example 6

[0092] The difference between Comparative Example 6 and Application Example 1 is that:

[0093] The degradation reaction was carried out under ultrasound conditions only and without light.

[0094] Comparative Example 7

[0095] The difference between Comparative Example 7 and Application Example 2 is that:

[0096] The degradation reaction was carried out under stirring and light conditions only, without ultrasound to assist the reaction.

[0097] Comparative Example 8

[0098] The difference between Comparative Example 8 and Application Example 3 is that:

[0099] The degradation reaction was carried out under ultrasound conditions only and without light.

[0100] Comparative Example 9

[0101] The difference between Comparative Example 9 and Application Example 3 is that:

[0102] The degradation reaction was carried out under stirring and light conditions only, without ultrasound to assist the reaction.

[0103] Comparative Example 10

[0104] The difference between Comparative Example 10 and Application Example 3 is that:

[0105] The degradation reaction was carried out under ultrasound conditions only and without light.

[0106] Comparative Example 11

[0107] The difference between Comparative Example 11 and Application Example 4 is that:

[0108] The degradation reaction was carried out under stirring and light conditions only, without ultrasound to assist the reaction.

[0109] Performance Testing

[0110] 1. Take a photo of the crystal obtained in Example 1 under a microscope. The photo is as follows: Figure 1 As shown, it can be seen that the crystal is colorless, has a relatively regular hexagonal prism shape, and is 0.7 mm in size.

[0111] The crystal obtained in Example 1 was subjected to X-ray single crystal diffraction measurement, and the structure was as follows Figure 2 As shown, it is determined that the obtained product is the piezoelectric heterometallic co-doped titanium oxide cluster Ti of the present invention. 26 Pb 10 , as can be seen from the figure, Ti 26 Pb 10 Belongs to the P-1 space group of the triclinic system, is a nano-type package, long Width In addition, Ti 26 Pb 10 The cluster structure consists of 26 Ti 4+ , 10 Pb 2+ , 34 μ3-O, 6 μ2-O, 4 μ4-O, and 38 benzoate (Bz) groups. This cluster belongs to C iThe S2 molecular point group has a nanoscale binuclear symmetrical structure consisting of two Ti 13 Pb5O 22 The subunits are connected by μ-O bridges. 26 Pb 10 All Ti in the cluster are hexa-coordinated, showing an octahedral configuration. However, the coordination environment of Pb is significantly heterogeneous. 2+ By embedding bridging oxygen into the Ti-oxo core, eight Pb 2+ It is anchored on the surface of the Ti-oxo core through bridging oxygen and benzoic acid ligands.

[0112] The crystals obtained in Example 1 were subjected to infrared spectroscopy (RXI Fourier transform infrared spectrometer, KBr pellet method), and the results were as follows: Figure 3 As shown in the figure, the moderately strong absorption peak at a wavelength of around 1500 cm-1 is attributed to the stretching vibration peak of the carboxyl group on the benzoic acid ligand, and the peak in the range of 500-700 cm-1 is attributed to the stretching vibration peak of Ti-O. The appearance of the characteristic peaks of carboxylate and Ti-O in the infrared spectrum confirms that benzoic acid is successfully coordinated with metal Ti through the carboxylate to form a stable complex.

[0113] The crystals obtained in Example 1 were fully ground and then subjected to powder X-ray diffraction analysis. The results were as follows: Figure 4 As shown in the figure, it can be seen that the peak position, peak shape and intensity of the experimental data are in good agreement with those of the theoretical data, which indicates that the purity of the obtained crystals is high.

[0114] After fully grinding the crystals obtained in Example 1, a small amount of solid was placed in the center of the BaSO4 substrate. After compacting with a tool, the UV-visible diffuse reflectance UV-vis DRS spectrum of the obtained product in the range of 300-800nm ​​was measured. The results are as follows: Figure 5 As shown in the figure, it can be seen that Ti 26 Pb 10 The absorption band edge is red-shifted to about 420nm. Compared with the commonly used photocatalyst TiO2, which only has corresponding light absorption in the ultraviolet region below 400nm, Ti 26 Pb 10 It exhibits a significantly extended visible light response range, which is mainly due to the 2 +6s 2 The hybridization of lone pairs of electrons with the orbitals of the Ti-O skeleton induces an elevation of the valence band top and the introduction of intermediate energy levels, leading to a change in its band gap. This indicates that the successful doping of Pb effectively lowers the conduction band potential and enhances the reduction ability of photogenerated electrons.

[0115] Take the crystals obtained in Example 1, grind them thoroughly with an agate mortar, accurately weigh 1.5 mg of powder and disperse it in 15 mL of anhydrous ethanol, and obtain a uniform dispersion by ultrasonic treatment for 15 minutes. Use a micropipette to accurately take 40 μL of the dispersion droplets and apply them to a P-type doped silicon substrate (resistivity 0.01Ω·cm). After the solvent evaporates naturally, apply conductive glue to the edge area of ​​the sample to construct a conductive path. The test uses a Bruker Dimension Icon atomic force microscope to perform piezoelectric response force microscopy (PFM) characterization at a scanning rate of 1 Hz in tapping mode. At the same time, a DC bias of -8V to +8V is applied for polarization scanning. The entire test process was completed in a dark environment with a constant temperature of 25±0.5°C and a relative humidity of <5%, which effectively eliminated thermal disturbances and photo-induced carrier interference. The results are as follows Figure 6 As shown in the figure, it can be seen that the amplitude-voltage curve shows a typical butterfly symmetry feature, and the phase lag angle can be reversibly flipped within the range of ±100°, confirming that Ti 26 Pb 10 Crystals have a significant intrinsic piezoelectric effect. According to the formula: (A0 and V0 are the intersection points of the butterfly curve, but not the intersection points of the two ends. V is the excitation voltage at the maximum amplitude (A)) Calculate and determine the piezoelectric slope, which is not less than 5mV / V.

[0116] The catalyst surface potential of the product obtained in Example 1 was measured using a Kelvin probe force microscope. Figure 7 As shown, the probe is used to measure Ti 26 Pb 10 When stress is applied to the surface, it can be clearly seen that there is an obvious potential difference between the catalyst and the substrate, which further confirms that the obtained product has piezoelectric properties.

[0117] 2. Take the reaction solutions of Application Example 1, Comparative Example 3 and Comparative Example 4 at different reaction time periods, respectively, and use an ultraviolet spectrophotometer to detect and record the absorbance at 355 nm in different reaction time periods. Calculate the degradation rate according to the calculation formula of the degradation rate, and plot the degradation rate as the ordinate and the reaction time as the abscissa to obtain the degradation kinetic curve of tetracycline. The results are as follows: Figure 8a As shown in the figure, it can be seen that after 30 minutes of adsorption under dark conditions, Ti 26 Pb 10 The adsorption rate of tetracycline is about 10%, indicating that the adsorption capacity of its surface active sites for pollutants is moderate. 26 Pb 10 Only 20% degradation efficiency was achieved within 80 minutes (excluding the adsorption effect of dark reaction); under the conditions of Comparative Example 4, its photocatalytic efficiency was increased to 67% (excluding the adsorption effect of dark reaction), but under the conditions of Application Example 1, that is, under the conditions of piezoelectric-photocatalytic synergy, Ti26 Pb 10 The degradation efficiency of -Ln(C0-C t ) / C0 is the vertical coordinate, and the kinetic curve is converted into a rate curve, such as Figure 8b , Application Example 1 Rate constant under piezoelectric-photocatalytic synergistic conditions (0.0568min -1 ) is for Example 3 under ultrasonic conditions only (0.00267min -1 ) is 21 times that of Comparative Example 4 under light conditions only (0.01365min -1 ), which indicates that the addition of mechanical stress greatly accelerates the separation efficiency of photogenerated carriers, thereby improving the degradation efficiency of tetracycline.

[0118] 3. Application Example 1 After the reaction is completed, the catalyst Ti is separated by centrifugation. 26 Pb 10 , the obtained catalyst Ti 26 Pb 10 The recovered catalyst Ti was washed several times with ultrapure water of resistivity 18.25MΩ·cm and then dried. 26 Pb 10 Put it into the above piezoelectric photocatalytic degradation reaction again, and continue to recover the catalyst Ti after the reaction is completed. 26 Pb 10 , and so on, the catalyst Ti 26 Pb 10 The above piezoelectric-photosynergistic catalytic degradation reaction was repeated 4 times. The reaction liquid of the 4 reactions was detected by ultraviolet spectrophotometer and the absorption peak intensity at 355nm was recorded to calculate the degradation rate. The degradation rate curve of the 4 reactions was obtained as shown in FIG. Figure 9 As shown in the figure, it can be seen that the catalyst Ti 26 Pb 10 When the material is first put into the piezoelectric photocatalytic degradation reaction, the conversion rate is 100%, and when it is put into the reaction for the fourth time, the conversion rate is 97%, and the catalytic efficiency decay is less than 10%.

[0119] The catalyst Ti that participated in four piezoelectric-photocatalytic degradation reactions 26 Pb 10 Recover, and carry out infrared spectrum detection, XRD detection, the results are as follows Figure 10a ), 10b), it can be seen from the figure that the XRD peak position of the catalyst after 4 piezoelectric photocatalytic degradation reactions is basically consistent with that of the catalyst before participating in the reaction ( Figure 10a 、 10b ), which proves that its stability is relatively good.

[0120] 4. Take the reaction solutions of Application Example 1 and Comparative Example 5 at different reaction time periods, respectively, and use an ultraviolet spectrophotometer to detect and record the absorbance at 355 nm at different reaction time periods. Calculate the degradation rate according to the calculation formula of the degradation rate, and plot the degradation rate as the ordinate and the reaction time as the abscissa to obtain the degradation kinetic curve of tetracycline. The results are as follows: Figure 11 As shown in the figure, it can be seen that under the same reaction conditions and reaction time, the degradation efficiency of PbTiO3 is much lower than that of Ti 26 Pb 10 , Ti 26 Pb 10 The degradation efficiency of TiO3 (100%) is 4.3 times that of PbTiO3 (23%), which indicates that the degradation efficiency of TiO3 is 100% and the degradation efficiency of PbTi ... 26 Pb 10 Has better catalytic activity.

[0121] 5. Take the reaction solutions of Application Example 2, Comparative Example 6, and Comparative Example 7 at different reaction time periods, respectively, and use an ultraviolet spectrophotometer to detect and record the absorbance at 554 nm in different reaction time periods. Calculate the degradation rate according to the calculation formula of the degradation rate, and plot the degradation rate as the ordinate and the reaction time as the abscissa to obtain a kinetic curve of Rhodamine B. The results are as follows: Figure 12a As shown in the figure, it can be seen that compared with tetracycline, Ti 26 Pb 10 The adsorption of Rhodamine B is stronger, at about 40%. Like the degradation of tetracycline, under the synergistic effect of ultrasound and light, the degradation efficiency of Rhodamine B (about 99%, excluding the influence of dark adsorption) is higher than the sum of the degradation efficiencies of ultrasound alone (degradation efficiency about 17%, excluding the influence of dark adsorption) and light alone (degradation efficiency about 77%, excluding the influence of dark adsorption). After converting the kinetic curve into a rate curve, as shown in Figure 2, the degradation efficiency of Rhodamine B is about 99%, excluding the influence of dark adsorption. Figure 12b The rate constant of piezoelectric-photocatalytic synergy (0.05294min -1 ) is the sum of the single-field rate constants (0.02159 min -1 +0.00282min -1 =0.02441min -1 ), which is the same as the above conclusion, indicating that the existence of the piezoelectric field promotes the separation efficiency of photogenerated carriers.

[0122] 6. Take the reaction solutions of Application Example 3, Comparative Example 8, and Comparative Example 9 at different reaction time periods, and use an ultraviolet spectrophotometer to detect and record the absorption peak intensity at 664nm in different reaction time periods. Calculate the degradation rate according to the calculation formula of the degradation rate, and plot the degradation rate as the ordinate and the reaction time as the abscissa to obtain a kinetic curve of methylene blue. The results are shown in Figure 6. Figure 13a As shown in the figure, it can be seen that after 30 minutes of dark reaction, Ti26 Pb 10 The adsorption of methylene blue is about 10%, which shows that the adsorption of methylene blue on the active sites is moderate, and under the synergistic effect of ultrasound and light, Ti 26 Pb 10 The degradation efficiency of methylene blue within 160 min of reaction (100%, excluding the effect of dark adsorption) is close to the sum of the degradation efficiencies of ultrasound alone (degradation efficiency of about 33%, excluding the effect of dark adsorption) and light alone (degradation efficiency of about 68%, excluding the effect of dark adsorption), both of which are 100%. However, after being converted into rate constants, Figure 13b The rate constant of the synergistic effect of light and piezoelectricity (0.02982min -1 ) is much larger than the rate constant of ultrasound alone (0.00228min -1 ) and the rate constant for light alone (0.00778 min -1 ) is three times the sum of a single field, which indicates that the existence of the piezoelectric field promotes the separation efficiency of photogenerated carriers, and the mechanical-photoelectric coupling enhancement mechanism is also applicable to the degradation of methylene blue.

[0123] 7. The reaction solutions of Application Example 4, Comparative Example 10, and Comparative Example 11 at different reaction time periods were respectively taken and the concentration of penicillin was detected by high performance liquid chromatography. Under the conditions of acetonitrile and 0.01% formic acid (50:50) as the mobile phase, a flow rate of 1 mL / min, a column box temperature of 25°C, and a detection wavelength of 254 nm, the peak position of penicillin was around 4.4 min. By recording the peak area of ​​penicillin, the degradation rate (%) was calculated as follows: (C0-C t ) / C0=(A0-A t ) / A0, (where C0 and A0 are initial concentration and initial peak area, respectively, C t and A t The degradation efficiency of penicillin was calculated by taking the degradation rate as the ordinate and the reaction time as the abscissa. The results are shown in Figure 2. Figure 14 As shown in the figure, it can be seen that after 30 minutes of dark reaction, Ti 26 Pb 10 The adsorption of penicillin is about 2%, which indicates that the active sites have poor adsorption of methylene blue, and under the synergistic effect of ultrasound and light, Ti 26 Pb 10The degradation efficiency of penicillin within 200 minutes of reaction (about 87%) is much higher than the sum of the degradation efficiencies of ultrasound alone (degradation efficiency about 13%) and light alone (degradation efficiency about 33%). Even if the influence of dark adsorption is not excluded, its degradation efficiency is about twice the sum of the degradation efficiencies of the two. This is enough to show that the existence of the piezoelectric field greatly promotes the separation efficiency of photogenerated carriers, and the mechanical-photoelectric coupling enhancement mechanism is also applicable to the degradation of penicillin.

[0124] In summary, it can be seen that the piezoelectric heterometallic co-doped titanium oxide cluster prepared in the embodiment of the present invention has good stability and piezoelectric activity, and has a high degradation rate when used in the piezoelectric-photocatalytic synergistic degradation of antibiotics such as tetracycline, rhodamine B, methylene blue, and penicillin.

[0125] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A piezoelectric heterometallic co-doped titanium oxide cluster, characterized in that: The molecular formula of the piezoelectric heterometallic co-doped titanium oxide cluster is H2Ti 26 Pb 10 (μ4-O)4(μ3-O) 34 (μ2-O)6Bz 38 ·6MeCN·2(C4H9ON), abbreviated as Ti 26 Pb 10 ; Among them, μ3-O represents a triple-bridged O atom, μ2-O represents a double-bridged O atom, μ4-O represents a quadruple-bridged O atom, Bz represents a benzoic acid ligand, MeCN represents an acetonitrile solvent molecule, and C4H9ON represents a morpholine solvent molecule.

2. The piezoelectric heterometallic co-doped titanium oxide cluster according to claim 1, wherein: The crystal system of the piezoelectric heterometallic co-doped titanium oxide cluster crystalline material is triclinic, the space group is P-1, and the unit cell parameter a is b is c is α is 66.4°, β is 70.6°, γ is 63.8°, and the unit cell volume is 3. A method for preparing the piezoelectric heterometallic co-doped titanium oxide cluster compound according to claim 1 or 2, characterized in that: The following steps are involved: 1) adding lead acetate trihydrate, benzoic acid, and piperazine to acetonitrile as a solvent and stirring to mix uniformly to obtain a suspension; adding morpholine and acetic acid to the suspension and continuing to stir to mix uniformly; 2) adding titanium tetraisopropoxide to the reaction system obtained in step 1), stirring evenly under sealing, and carrying out heat-insulating reaction; after the reaction is completed, washing and vacuum drying are performed to obtain the target product.

4. The method according to claim 3, wherein: The reaction temperature is 95°C-105°C, and the reaction time is 14d-21d.

5. The method according to claim 3, wherein: The molar ratio of titanium tetraisopropoxide, lead acetate trihydrate, acetic acid, morpholine, piperazine and benzoic acid is (1-3): (1-2): (1-2): (1-2): (1-2): (9-12).

6. Use of the piezoelectric heterometallic co-doped titanium oxide cluster compound according to claims 1 to 2, or the piezoelectric heterometallic co-doped titanium oxide cluster compound prepared by the method according to any one of claims 3 to 5, in piezoelectric-photosynergistic catalytic degradation of antibiotics.

7. The use according to claim 6, characterized in that The piezoelectric heterometallic co-doped titanium oxide cluster is added to the antibiotic and reacted in the dark. After the reaction reaches adsorption equilibrium, the reaction system is placed in a reactor equipped with an ultraviolet lamp and ultrasound and reacts under the combined action of ultrasound and light.

8. The use according to claim 7, characterized in that The antibiotic is selected from one of tetracycline, rhodamine B, methylene blue and penicillin.

9. The use according to claim 7, characterized in that The molar ratio of the piezoelectric heterometallic co-doped titanium oxide cluster to the antibiotic is (1-3): (1-3).

10. The use according to claim 7, characterized in that The wavelength of the ultraviolet lamp is 360nm to 380nm, the ultrasonic power is 120W to 150W, and the frequency is 30kHz to 50kHz.

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