A photocatalyst and preparation and application thereof

Abstract

The application discloses a kind of photocatalyst and its preparation and application, it is ADA type compound, ADA type compound includes metal organic framework material as first electron acceptor, electron donor loaded on metal organic framework, second electron acceptor is adsorbed to electron donor, and electron donor is perovskite quantum dot, and the number of hydrogen bond electron acceptor of second electron acceptor is 2;The energy band structure of photocatalyst is type II, and the double-acceptor system of acceptor (A)-donor (D)-acceptor (A) constructed with electron ADA type compound is different from single acceptor (A)-donor (D) system, can effectively inhibit the recombination of photo-generated electron and hole, while not destroying PQDs@MOF structure, effectively improve the photocatalytic efficiency of catalyst, with the advantages of raw material easy to obtain, low equipment requirement.

Description

Technical Field

[0001] This invention relates to the field of photocatalysis technology, and more particularly to a photocatalyst and its preparation and application. Background Technology

[0002] Photocatalytic degradation of organic pollutants is of great significance for developing a green economy and achieving sustainable development of human society. The design and preparation of high-performance photocatalysts are crucial for fully utilizing solar energy and achieving efficient pollutant degradation. Metal-organic frameworks (MOFs) can generate a photoresponse by absorbing light through organic ligands or metal centers. They possess advantages such as large specific surface area, numerous active sites, and tunable chemical composition and crystal structure, making them highly promising photocatalysts that have attracted considerable interest. Meanwhile, perovskite quantum dots (PQDs) also exhibit excellent performance in photocatalysis due to their tunable band gap, large extinction coefficient, and high defect tolerance. By constructing PQDs@MOF composite photocatalysts, the stability of PQDs can be increased while compensating for the low visible light utilization of MOF materials, resulting in superior photocatalytic effects.

[0003] However, the performance of current PQDs@MOF photocatalysts is still insufficient to meet practical application requirements. One of the limiting factors is the short lifetime of photogenerated carriers. Although researchers have achieved photogenerated carrier transfer and separation between PQDs and MOFs in DA systems by designing and adjusting the chemical composition of the acceptor (or donor) and the band structure, thus delaying carrier annihilation and improving photocatalyst performance to some extent—for example, reports indicate that photogenerated electrons generated in MAPbI3 PQDs can be transferred to Fe-based MOF materials (PCN-221(Fe0.2)), resulting in a 38-fold increase in the photocatalytic CO2 degradation efficiency of MAPbI3 PQDs@PCN-221(Fe0.2) compared to PCN-221(Fe0.2) alone—due to the strong coupling effect between PQDs and MOFs, the separated charges still recombine rapidly, making it difficult for them to participate in subsequent photocatalytic reactions, which is detrimental to further improving photocatalyst performance.

[0004] Therefore, it is necessary to provide a means to suppress the recombination of photogenerated carriers in PQDs@MOF photocatalysts in order to improve their photocatalytic efficiency and promote their application in the field of photocatalysis. Summary of the Invention

[0005] In view of this, this application provides a photocatalyst and its preparation and application to solve the problem of low photocatalytic efficiency caused by the strong coupling effect between PQDs and MOF.

[0006] To achieve the above technical objectives, this application adopts the following technical solution:

[0007] In a first aspect, this application provides a photocatalyst, which is an ADA-type composite. The ADA-type composite includes a metal-organic framework material as a first electron acceptor, an electron donor supported on the metal-organic framework, and a second electron acceptor adsorbed on the electron donor. The electron donor is a perovskite quantum dot, and the number of hydrogen-bonded electron acceptors of the second electron acceptor is 2. The band structure of the photocatalyst is type II.

[0008] Preferably, the perovskite quantum dots are CsPbBr3 perovskite quantum dots.

[0009] Preferably, the metal-organic framework material is UiO-67.

[0010] Preferably, the second electron acceptor is p-benzoquinone.

[0011] Secondly, this application provides a method for preparing a photocatalyst, comprising the following steps:

[0012] S1. Perovskite quantum dots are grown in situ inside a metal-organic framework material to obtain PQDs@MOF powder;

[0013] S2. Disperse PQDs@MOF powder in an aqueous solution of the second electron acceptor, sonicate, and then vacuum dry to obtain the photocatalyst.

[0014] Preferably, step S1 includes:

[0015] S11. Disperse PbBr2 and UiO-67 powders in an organic solvent and heat to obtain a mixture;

[0016] S12. Under an inert atmosphere, an organic solution of Cs2CO3 was added to the mixture, heated to react, then cooled and centrifuged to obtain PQDs@MOF powder.

[0017] Preferably, the mass ratio of UiO-67 powder to PbBr2 is 0.05-0.15:0.046-0.138.

[0018] Preferably, the mass ratio of electron acceptor to metal-organic framework material powder is 0.0006-0.002:0.05-0.15.

[0019] Preferably, in step S12, the temperature of the heating reaction is 150-165℃.

[0020] Thirdly, this application provides the application of a photocatalyst in the degradation of organic pollutants.

[0021] The beneficial effects of this application are as follows:

[0022] This application presents a dual-acceptor system of acceptor (A)-donor (D)-acceptor (A) constructed from an electronic ADA-type complex. Unlike a single acceptor (A)-donor (D) system, this system can effectively suppress the recombination of photogenerated electrons and holes. It can effectively improve the photocatalytic efficiency of the catalyst without destroying the band structure of PQDs@MOF, and has the advantages of readily available raw materials and low equipment requirements.

[0023] This application defines the band structure of the photocatalyst as type II by limiting the component types of PQDs and MOF, which enables the transfer of photogenerated electrons from PQDs to MOF. While promoting the separation of photogenerated electron-hole pairs, it utilizes the advantage of the large extinction coefficient of PQDs in the visible light region to use them as photosensitizers, thereby improving the utilization rate of solar energy by the photocatalyst. Furthermore, by combining PQDs with two electron acceptor pairs to form a dual acceptor system (metal-organic framework (A)-PQD quantum dot (D)-p-benzoquinone (A)), the recombination of photogenerated charges can be effectively hindered, forming a long-lived charge-separated state, thereby improving its photocatalytic efficiency.

[0024] This application specifies that the PQDs are CsPbBr3 (cesium bromide lead cesium) perovskite quantum dots, whose absorption displacement is located at around 510 nm. Therefore, they can be used as photosensitizers to effectively improve the visible light response of UiO-67 and enhance photocatalytic efficiency. At the same time, due to the protection of the microporous structure of UiO-67, the CsPbBr3 perovskite quantum dots have high stability, thus improving catalytic stability. Attached Figure Description

[0025] Figure 1 X-ray diffraction patterns of UiO-67, CsPbBr3 PQDs@UiO-67 and CsPbBr3 PQDs@UiO-67@BQ;

[0026] Figure 2 Steady-state absorption spectra of UiO-67, CsPbBr3 PQDs@UiO-67 and CsPbBr3 PQDs@UiO-67@BQ;

[0027] Figure 3 Transient absorption kinetics of CsPbBr3 PQDs@UiO-67 powder at 500 nm and 515 nm under 340 nm laser excitation;

[0028] Figure 4 The fluorescence lifetime curves are for CsPbBr3 PQDs@UiO-67 and CsPbBr3 PQDs@UiO-67@BQ.

[0029] Figure 5The fluorescence lifetime curves of CsPbBr3 PQDs@UiO-67 and CsPbBr3 PQDs@UiO-66 are shown.

[0030] Figure 6 The test results show the photocatalytic degradation effects of UiO-67, CsPbBr3 PQDs@UiO-67, and CsPbBr3 PQDs@UiO-67@BQ. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0032] Terminology Explanation

[0033] Electron ADA-type complex: a dual-receptor system complex of electron acceptor (A)-donor (D)-acceptor (A).

[0034] Type II band structure: The valence band (E) of semiconductors that make up a heterojunction V1 and E V2 ) and conduction band (E) C1 and E C2 The bands are arranged in an alternating pattern to form a type II band structure.

[0035] This application provides a photocatalyst, which is an ADA-type composite. The ADA-type composite includes a metal-organic framework material as a first electron acceptor, an electron donor supported on the metal-organic framework, and a second electron acceptor adsorbed on the electron donor. The electron donor is a perovskite quantum dot, and the number of hydrogen-bonded electron acceptors of the second electron acceptor is 2. The band structure of the photocatalyst is type II.

[0036] This application presents a dual-acceptor system (A)-donor (D)-acceptor (A) constructed from an electronic ADA-type complex. Unlike a single acceptor (A)-donor (D) system, this system effectively suppresses the recombination of photogenerated electrons and holes, forming long-lived charge-separated states. This significantly improves the photocatalytic efficiency of the catalyst without damaging the PQDs@MOF structure, offering advantages such as readily available raw materials and low equipment requirements. Furthermore, the metal-organic framework material and perovskite quantum dots both have type II band structures, enabling photogenerated electron transfer from PQDs to the MOF. This reduces the probability of rapid recombination of separated charges caused by strong coupling between PQDs and the MOF, thereby enhancing photocatalytic efficiency.

[0037] Preferably, the perovskite quantum dots are CsPbBr3 perovskite quantum dots.

[0038] Preferably, the metal-organic framework material is UiO-67; the chemical formula of UiO-67 is C 84 H 52 O 32 Zr6; in some embodiments, it is obtained directly from commercial purchase (CAS1072413-83-2); in other embodiments, it is obtained by heating and reacting 4,4-biphenyl dicarboxylic acid and ZrCl4 with DMF as solvent.

[0039] By defining the specific components of perovskite quantum dots (PQDs) and metal-organic frameworks (MOFs), the band structure of the photocatalyst is made to be type II, thereby enabling photogenerated electron transfer from PQDs to MOFs and suppressing the recombination of photogenerated carriers in the PQDs@MOF photocatalyst. By defining the PQDs as CsPbBr3 perovskite quantum dots, whose absorption shift is located at around 510 nm, they can be used as photosensitizers to effectively improve the visible light response of UiO-67 and enhance photocatalytic efficiency. At the same time, due to the protection of the microporous structure of UiO-67, the CsPbBr3 perovskite quantum dots have high stability, thus improving catalytic stability.

[0040] Preferably, the second electron acceptor is p-benzoquinone, which has two hydrogen bond acceptors. This effectively inhibits the recombination of photogenerated charges, forming a long-lived charge-separated state. When p-benzoquinone is added to PQDs@MOF powder, it forms a dual acceptor system (metal-organic framework (A)-PQDs quantum dot (D)-p-benzoquinone (A)) that can effectively inhibit the recombination of photogenerated electrons and holes. Without destroying the band structure of PQDs@MOF, it effectively improves the photocatalytic efficiency of the catalyst, and has the advantages of readily available raw materials and low equipment requirements.

[0041] This application provides a method for preparing a photocatalyst, comprising the following steps:

[0042] S1. Perovskite quantum dots are grown in situ inside a metal-organic framework material to obtain PQDs@MOF powder;

[0043] S2. Disperse PQDs@MOF powder in an aqueous solution of the second electron acceptor, sonicate, and then vacuum dry to obtain the photocatalyst.

[0044] Step S1 includes: S11. Dispersing PbBr2 and UiO-67 powders in an organic solvent and heating to obtain a mixture; S12. Adding an organic solution of Cs2CO3 to the mixture under an inert atmosphere, heating to react, then cooling and centrifuging to obtain PQDs@MOF powder.

[0045] In some embodiments, the mass ratio of UiO-67 powder to PbBr2 is 0.05-0.15:0.046-0.138. Excessive use of UiO-67 powder will result in the absence of CsPbBr3 PQDs in some UiO-67, thus failing to improve performance.

[0046] In some embodiments, the mass ratio of the second electron acceptor to the metal-organic framework material powder is 0.0006-0.002:0.05-0.15. Too little benzoquinone will lead to incomplete charge separation, while too much will affect the efficiency of PQDs and MOFs in absorbing solar photons.

[0047] In some embodiments, in step S12, the temperature of the heating reaction is 150-165°C.

[0048] In some embodiments, in step S2, the centrifugation rate is 800-1200 r / min. If the rotation speed is higher than 1200 r / min, CsPbBr3 PQDs may detach from the MOF framework.

[0049] The preparation method of UiO-67 is as follows: 0.0807-0.2422g of 4,4-biphenyl dicarboxylic acid, 0.0777-0.233g of ZrCl4 and 10-30ml of N,N-dimethylfuran (DMF) are added to a reaction vessel; the reaction vessel is placed in a preheated oven at 100-120℃ and reacted at a constant temperature for 24-36 hours; the above solution after complete reaction is cooled to room temperature to obtain a white powder, which is separated, washed with DMF, and dried under vacuum at 40-60℃ to obtain MOF powder, i.e., UiO-67, for later use;

[0050] Specifically, the preparation method of the above-mentioned photocatalyst is as follows:

[0051] S11. Disperse 0.046-0.138g PbBr2 and 0.05-0.15g UiO-67 powder in an organic solvent, stir under vacuum, and then heat to 120℃ to obtain a mixture. The organic solvent in step S1 is a mixture of 3.3mL-10mL octadecene, 0.67mL-2mL oleic acid, and 0.4mL-1.2mL oleylamine.

[0052] S12. Under an inert atmosphere, the organic solution of Cs2CO3 is added to the mixture, heated to react, then cooled, centrifuged for 3-5 minutes, the lower precipitate is taken off, washed with anhydrous ethanol and dried under vacuum at 40-60℃ to obtain PQDs@MOF powder; the organic solution of Cs2CO3 contains 5mL-15mL octadecene, 0.4mL-1.2mL oleic acid, and 0.1333g-0.4g of Cs2CO3. The above substances are mixed and heated to 120℃ to obtain the organic solution of Cs2CO3; in step S2, the organic solution of Cs2CO3 is heated to 150℃, the mixture from step S11 is heated to 165℃, and the separately heated organic solutions of Cs2CO3 are added to the mixture, and then rapidly cooled in an ice bath;

[0053] S2. Disperse PQDs@MOF powder in an aqueous solution of p-benzoquinone, sonicate, remove the liquid, and then vacuum dry at 40-60℃ to obtain the photocatalyst. The aqueous solution of p-benzoquinone contains 0.0006-0.002g of p-benzoquinone and 2-5mL of water.

[0054] This application provides the application of a photocatalyst in the degradation of organic pollutants, including but not limited to the degradation of dibutyl phthalate.

[0055] The following detailed implementation method will further illustrate this method.

[0056] Example 1

[0057] A photocatalyst is an ADA-type composite, comprising a metal-organic framework material as a first electron acceptor, an electron donor supported on the metal-organic framework, and a second electron acceptor adsorbed on the electron donor. The electron donor is a perovskite quantum dot, and the second electron acceptor has two hydrogen-bonded electron acceptors. The metal-organic framework material is UiO-67, and the photocatalyst has a type II band structure.

[0058] A method for preparing a photocatalyst includes the following steps:

[0059] 0.2422 g of 4,4-biphenyl dicarboxylic acid, 0.233 g of ZrCl4, and 30 mL of N,N-dimethylfuran (DMF) were added to a 50 mL reaction vessel. The reaction vessel was placed in an oven and reacted at 120 °C for 24 h to obtain a reaction solution. The reaction solution was cooled to room temperature, the white powder was separated, washed with 20 mL of DMF, and dried under vacuum at 40 °C for 24 h to obtain UiO-67 powder for later use.

[0060] 0.4 g Cs₂CO₃, 15 mL octadecene, and 1.2 mL oleic acid were added to a 100 mL three-necked flask. The mixture was stirred under vacuum and heated to 120 °C to obtain solution a. 0.138 g PbBr₂ and 0.15 g UiO-67 powder were dispersed in a mixed solution consisting of 10 mL octadecene, 2 mL oleic acid, and 1.2 mL oleylamine. This solution was added to a 100 mL three-necked flask, stirred under vacuum, and heated to 120 °C to obtain solution b. N₂ was introduced, and solutions a and b were heated to 150 °C and 165 °C, respectively. Under vigorous stirring, 0.6 mL of solution a was rapidly injected into solution b, and then quickly cooled to room temperature in an ice-water bath. The mixture was centrifuged at 1000 rpm for 3 min to separate the precipitate. The lower precipitate was collected, washed with anhydrous ethanol, and dried under vacuum to obtain CsPbBr₃ PQDs@UiO-67 powder for later use.

[0061] Dissolve 0.002 g of p-benzoquinone (BQ) in 5 mL of deionized water to prepare a solution; disperse 0.1 g of CsPbBr3PQDs@UiO-67 powder in the p-benzoquinone aqueous solution, sonicate, remove the liquid, take the powder, and vacuum dry at 40 °C for 24 h to obtain the final product.

[0062] In the final product, the central metal atom of UiO-67 is Zr, and biphenyl dicarboxylic acid acts as an organic ligand connecting the central atoms to form a porous structure. CsPbBr3 quantum dots are distributed in the channels of UiO-67, with an average particle size of approximately 2 nm. BQ is adsorbed on CsPbBr3 PQDs@UiO-67 powder. The final product is a pinkish-white powder that fluoresces blue-green under 405 nm laser irradiation. The crystal structure of the prepared material was analyzed, and the material prepared in Example 1 was characterized by X-ray powder diffraction, with the results as follows: Figure 1 As shown, Figure 1 The X-ray diffraction patterns of UiO-67, CsPbBr3 PQDs@UiO-67, and CsPbBr3PQDs@UiO-67@BQ in Example 1 are shown. It can be seen that, in addition to the characteristic diffraction peaks belonging to UiO-67, new diffraction peaks belonging to CsPbBr3 PQDs also appear in CsPbBr3 PQDs@UiO-67 and CsPbBr3PQDs@UiO-67@BQ, confirming the successful formation of perovskite quantum dots in UiO-67.

[0063] Example 2

[0064] A photocatalyst, otherwise identical to Example 1, except that the amount of UiO-67 powder is 0.05g; the mass of PbBr2 is 0.046g; the mass of p-benzoquinone is 0.0006g; and the amount of Cs2CO3 is 0.1333g.

[0065] Example 3

[0066] A photocatalyst, otherwise identical to Example 1, except that the amount of UiO-67 powder used is 0.1g; and the mass of p-benzoquinone is 0.001g.

[0067] Comparative Example 1

[0068] A photocatalyst, otherwise identical to Example 1, except that the metal-organic framework material UiO-67 is replaced with UiO-66 (CAS1072413-89-8).

[0069] Evaluation Test

[0070] Steady-state absorption spectra of the materials prepared in Example 1, UiO-67, and CsPbBr3PQDs@UiO-67 were measured using a UV-Vis spectrophotometer. Figure 2 The steady-state absorption spectra of UiO-67, CsPbBr3PQDs@UiO-67, and CsPbBr3 PQDs@UiO-67@BQ in Example 1 are shown. It can be seen that the absorption edge of pure UiO-67 is located at 350 nm, mainly absorbing ultraviolet light with weak absorption of visible light. The addition of CsPbBr3 PQDs to CsPbBr3 PQDs@UiO-67 increases the absorption of quantum dots at 510 nm, effectively improving the utilization rate of visible light and thus benefiting photocatalytic efficiency. Further addition of BQ yields CsPbBr3 PQDs@UiO-67@BQ in Example 1. In addition to the two absorption types mentioned above, a shoulder peak with a wavelength range of 530-750 nm also appears, further broadening the absorption range of visible light and further improving photocatalytic efficiency.

[0071] The photogenerated electron transfer process between CsPbBr3 PQDs and UiO-67 was investigated using transient absorption spectroscopy. Figure 3 Under 340nm laser excitation, the absorbance difference of CsPbBr3 PQDs@UiO-67 powder at 500nm and 515nm in Example 1 changes with time, corresponding to the signals of excited-state electrons in UiO-67 and band-edge carriers of CsPbBr3 PQDs, respectively. It can be seen that as the signal of band-edge carriers of CsPbBr3 PQDs decays, the signal of excited-state electrons in UiO-67 gradually increases, corresponding to the electron transfer process from CsPbBr3 PQDs to UiO-67. However, this effect does not occur when using UiO-66 in Comparative Example 1.

[0072] The lifetime of photogenerated carriers in CsPbBr3 PQDs@UiO-67 and CsPbBr3PQDs@UiO-67@BQ in Example 1 was characterized using time-resolved fluorescence. Figure 4 The comparison of the fluorescence lifetime of UiO-67 at 460nm with and without BQ shows that the fluorescence of UiO-67 exhibits a significant long-lifetime component after the addition of BQ. This indicates that the addition of BQ can effectively hinder carrier recombination and delay the lifetime of photogenerated carriers, thereby improving photocatalytic performance.

[0073] The fluorescence lifetimes of CsPbBr3 PQDs@UiO-67 in Example 1 and CsPbBr3PQDs@UiO-66 in Comparative Example 1 were measured using time-resolved fluorescence. Figure 5 The comparison of fluorescence lifetimes between CsPbBr3 PQDs@UiO-67 and CsPbBr3 PQDs@UiO-66 shows that the fluorescence lifetime of CsPbBr3 PQDs@UiO-67 is significantly shorter than that of CsPbBr3 PQDs@UiO-66. This reflects the higher carrier separation efficiency of CsPbBr3 PQDs@UiO-67 and its better suppression of recombination of photogenerated carriers in the PQDs@MOF photocatalyst.

[0074] Using the photocatalytic degradation of dibutyl phthalate (DBP) as a model system, the photocatalytic performance of CsPbBr3 PQDs@UiO-67@BQ and UiO-67, and CsPbBr3 PQDs@UiO-67 in Example 1 were evaluated as comparisons. Figure 6 The photocatalytic efficiency comparison curves of the three show that the photocatalytic performance of CsPbBr3 PQDs@UiO-67@BQ is significantly improved compared to UiO-67 and CsPbBr3 PQDs@UiO-67.

[0075] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a photocatalyst, characterized in that, The photocatalyst is an ADA-type composite, which includes a metal-organic framework material as a first electron acceptor, an electron donor supported on the metal-organic framework, and a second electron acceptor adsorbed on the electron donor. The electron donor is a perovskite quantum dot, and the second electron acceptor has two hydrogen-bonded electron acceptors. The band structure of the photocatalyst is type II. The perovskite quantum dots are CsPbBr3 perovskite quantum dots. The metal-organic framework material is UiO-67; The second electron acceptor is p-benzoquinone; The preparation method includes the following steps: S1. Perovskite quantum dots are grown in situ inside a metal-organic framework material to obtain PQDs@MOF powder; S2. Disperse the PQDs@MOF powder in an aqueous solution of the second electron acceptor, sonicate, and then vacuum dry to obtain the photocatalyst.

2. The method for preparing the photocatalyst according to claim 1, characterized in that, Step S1 includes: S11. Disperse PbBr2 and UiO-67 powders in an organic solvent and heat to obtain a mixture; S12. Under an inert atmosphere, an organic solution of Cs2CO3 is added to the mixture, heated to react, then cooled and centrifuged to obtain PQDs@MOF powder.

3. The method for preparing the photocatalyst according to claim 2, characterized in that, The mass ratio of the UiO-67 powder to the PbBr2 is 0.05-0.15:0.046-0.

138.

4. The method for preparing the photocatalyst according to claim 1, characterized in that, The mass ratio of the second electron acceptor to the metal-organic framework material powder is 0.0006-0.002:0.05-0.

15.

5. The method for preparing the photocatalyst according to claim 2, characterized in that, In step S12, the temperature of the heating reaction is 150-165℃.

6. The application of a photocatalyst prepared by any one of claims 1 to 5 in the degradation of organic pollutants.

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