A Nb2C QDs@PY-DHBD-COF composite photocatalyst and its preparation method

Abstract

This invention belongs to the field of semiconductor photocatalysis technology, specifically a Nb2C QDs@PY-DHBD-COF composite photocatalyst and its preparation method. The invention uses Nb2AlC MAX material as a precursor, etches to obtain Nb2C MXene, prepares Nb2C quantum dots (Nb2C QDs) using a hydrothermal method, and anchors them onto a pyrene-based covalent organic framework PY-DHBD-COF to form a highly efficient and stable composite photocatalyst, denoted as Nb2C QDs@PY-DHBD-COF. This composite photocatalyst has a simple preparation method, uses inexpensive and readily available raw materials, exhibits strong interfacial interactions, and demonstrates excellent photocatalytic performance. It shows high photocatalytic activity for hydrogen peroxide production under simulated sunlight, outperforming most reported photocatalysts.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor photocatalysis technology, specifically relating to Nb2C QDs@PY-DHBD-COF composite photocatalysts and their preparation methods. Background Technology

[0002] Hydrogen peroxide is a versatile oxidant with wide applications in chemical synthesis and wastewater treatment. Traditional industrial production of hydrogen peroxide utilizes a multi-step anthraquinone oxidation process, which is energy-intensive and complex. Photocatalytic synthesis of hydrogen peroxide is a promising alternative to traditional methods. Therefore, developing low-cost, high-efficiency photocatalysts to address the practical challenges of hydrogen peroxide production is imperative.

[0003] Covalent organic frameworks (COFs), with their customizable photoelectric properties and active site structures, have become promising platforms for the photocatalytic synthesis of hydrogen peroxide. However, they typically suffer from low charge generation and transfer efficiency and rapid charge recombination rates, limiting their application in the photocatalytic synthesis of hydrogen peroxide. Interfacial modulation strategies, such as constructing heterojunctions and introducing suitable sites, are beneficial for enhancing charge separation / transfer in COF photocatalysts, thus promoting the photocatalytic synthesis of hydrogen peroxide. In recent years, emerging two-dimensional transition metal carbides, nitrides, and carbonitrides (MXenes) have attracted widespread attention in the field of photocatalysis due to their tunable elemental composition and excellent photoelectric properties. Meanwhile, zero-dimensional quantum dots (MQDs) derived from MXenes not only inherit the properties of MXenes but also exhibit better dispersibility, light absorption capacity, excellent electron transport performance, and high stability due to quantum confinement effects. Therefore, the rational design of abundant MQD active sites in COFs for the photocatalytic synthesis of hydrogen peroxide is unprecedented and challenging. To date, there have been no studies or reports on Nb2C QDs@PY-DHBD-COF composite photocatalysts. Summary of the Invention

[0004] The purpose of this invention is to provide a Nb2C QDs@PY-DHBD-COF composite photocatalyst and its preparation method, in order to improve the hydrogen peroxide production activity of existing catalytic materials. The preparation method is simple, low-cost, and uses readily available reactants.

[0005] The present invention proposes a method for preparing a Nb2C QDs@PY-DHBD-COF (Nb2C MXene quantum dots@covalent organic framework) composite photocatalyst. Using Nb2AlC MAX material as a precursor, Nb2C MXene is etched to obtain Nb2C MXene. Nb2C quantum dots (Nb2C QDs) are then prepared using a hydrothermal method and anchored onto a pyrene-based covalent organic framework material (PY-DHBD-COF) to form a highly efficient and stable composite photocatalyst, denoted as Nb2C QDs@PY-DHBD-COF, which is used for photocatalytic hydrogen peroxide production. The specific steps are as follows:

[0006] (1) Nb2AlC raw material powder was slowly added to HF solution and stirred continuously. The mixture was reacted at a certain temperature and maintained for a period of time. The product was washed with deionized water, centrifuged, and freeze-dried to obtain Nb2C MXene.

[0007] (2) The Nb2C MXene precursor obtained in step (1) is transferred to a reactor, a certain volume of ultrapure water and ammonia is added, the reaction is carried out at a specific temperature and maintained for a period of time to obtain Nb2C QDs;

[0008] (3) Using 1,4-dihydroxybenzidine and 1,3,6,8-tetra(4-formylphenyl)pyrene as monomers, heat to a certain temperature and maintain for a period of time, collect the precipitate, wash with tetrahydrofuran and acetone, and dry under vacuum to obtain PY-DHBD-COF;

[0009] (4) Mix a certain amount of Nb2C QDs obtained in step (2) with a certain amount of PY-DHBD-COF obtained in step (3), disperse by ultrasonication, stir and react for a period of time, and then separate by centrifugation, wash and dry to obtain Nb2CQDs@PY-DHBD-COF composite photocatalyst.

[0010] Furthermore:

[0011] In step (1): the mass of Nb2AlC is 0.5-3g, the concentration of HF is 1-40%, and the volume is 10-40mL; the reaction temperature is 25-40℃, and the reaction time is 20-50h;

[0012] In step (2): the temperature is set to 80-150℃ and the holding time is 4-16h;

[0013] In step (3): the mass ratio of 1,4-dihydroxybenzidine to 1,3,6,8-tetra(4-formylphenyl)pyrene is 1:1 to 1:4; the temperature is set to 90 to 150°C, and the reaction time is 8 to 80 h;

[0014] In step (4): the mass ratio of Nb2C QDs to PY-DHBD-COF is 0.1:1 to 1:1; the reaction temperature is 20 to 50℃; and the reaction time is 10 to 180 min.

[0015] Furthermore, the specific operation process of the preparation method of the Nb2C QDs@PY-DHBD-COF composite photocatalyst proposed in this invention is as follows:

[0016] (1) 0.5-3g of Nb2AlC raw material powder was slowly added to HF (1-40%, 10-40mL) solution and stirred continuously. The mixture was reacted at 25-40℃ for 20-50h. The product was washed with deionized water, centrifuged, and freeze-dried to obtain Nb2C MXene.

[0017] (2) The Nb2C MXene precursor obtained in step (1) is transferred to a reactor, and ultrapure water and ammonia water (volume ratio of 10 to 20) are added. The reaction is carried out at 80 to 150°C for 4 to 16 hours to obtain Nb2C QDs.

[0018] (3) Using 1,4-dihydroxybenzidine and 1,3,6,8-tetra(4-formylphenyl)pyrene as monomers, with a mass ratio of 1:1 to 1:4, heating to 90 to 150°C and maintaining for 8 to 80 h, collecting the precipitate, washing with tetrahydrofuran and acetone, and drying under vacuum to obtain PY-DHBD-COF;

[0019] (4) The Nb2C QDs obtained in step (2) are mixed with the PY-DHBD-COF obtained in step (3) at a mass ratio of 0.1:1 to 1:1. The mixture is ultrasonically dispersed and stirred for reaction at a temperature of 20 to 50°C for 10 to 180 min. After centrifugation, washing and drying, the Nb2C QDs@PY-DHBD-COF composite catalyst is obtained.

[0020] A novel Nb2C QDs@PY-DHBD-COF composite photocatalyst was prepared using the method described above.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] (1) The Nb2C QDs@PY-DHBD-COF composite photocatalyst exhibits high photocatalytic hydrogen peroxide production activity under simulated sunlight, which is superior to most reported photocatalysts.

[0023] (2) Nb2C QDs combine with PY-DHBD-COF to form a heterojunction, which effectively promotes the migration of photogenerated carriers and improves the photocatalytic hydrogen peroxide production activity.

[0024] (3) By using a simple self-assembly method, Nb2C QDs are anchored onto PY-DHBD-COF. The built-in electric field is formed through interfacial interaction, which effectively promotes the migration rate of photogenerated carriers and effectively improves the photocatalytic hydrogen peroxide production activity. Attached Figure Description

[0025] Figure 1 TEM image of Nb2C QDs.

[0026] Figure 2 TEM image of the Nb2C QDs@PY-DHBD-COF composite catalyst.

[0027] Figure 3 SEM image of the Nb2C QDs@PY-DHBD-COF composite catalyst. Detailed Implementation

[0028] The present invention will be further illustrated below with specific embodiments, which are intended to explain the invention rather than limit it.

[0029] Example 1

[0030] (1) Preparation of Nb2C MXene: The specific process is as follows: Nb2AlC raw material powder (1g) is slowly added to HF (30mL) solution and stirred continuously. The mixture is reacted at a certain temperature (40℃) and maintained for a period of time (48h). The product is washed with deionized water, centrifuged, and freeze-dried to obtain Nb2C MXene.

[0031] (2) Preparation of Nb2C QDs: The specific process is as follows: the Nb2C MXene precursor obtained in step (1) is transferred to the reactor, a certain volume of ultrapure water and ammonia water (volume ratio 20) is added, the reaction is carried out at a specific temperature (120℃) and maintained for a period of time (8h) to obtain Nb2C QDs;

[0032] (3) The preparation of PY-DHBD-COF is as follows: 1,4-dihydroxybenzidine and 1,3,6,8-tetra(4-formylphenyl)pyrene are used as monomers (mass ratio of 2). The mixture is heated to a certain temperature and held for a period of time (120℃, 72h). The precipitate is collected, washed with tetrahydrofuran and acetone, and dried under vacuum to obtain PY-DHBD-COF.

[0033] (4) Preparation of Nb2C QDs@PY-DHBD-COF composite photocatalyst: A certain amount of Nb2C QDs obtained in step (2) and a certain amount of PY-DHBD-COF obtained in step (3) were mixed (mass ratio 0.1:1), ultrasonically dispersed, stirred and reacted for a period of time (120 min), the reaction temperature was 10℃, and after centrifugation, washing and drying, Nb2C QDs@PY-DHBD-COF composite photocatalyst was obtained. 2 mg of the above catalyst (1#) was weighed and a photocatalytic hydrogen peroxide production experiment was carried out.

[0034] Example 2

[0035] (1) The preparation process of Nb2C MXene, Nb2C QDs and PY-DHBD-COF is the same as in Example 1.

[0036] (2) Preparation of Nb2C QDs@PY-DHBD-COF composite catalyst: The specific process is as follows: A certain amount of Nb2C QDs obtained in step (1) is mixed with PY-DHBD-COF (mass ratio of 0.2:1), ultrasonically dispersed, stirred and reacted for a period of time (120 min), the reaction temperature is 15℃, and after centrifugation, washing and drying, Nb2C QDs@PY-DHBD-COF composite catalyst is obtained. 2 mg of the above catalyst (2#) is weighed and a photocatalytic hydrogen peroxide production experiment is carried out.

[0037] Example 3

[0038] (1) The preparation process of Nb2C MXene, Nb2C QDs and PY-DHBD-COF is the same as in Example 1.

[0039] (2) Preparation of Nb2C QDs@PY-DHBD-COF composite catalyst: The specific process is as follows: A certain amount of Nb2C QDs obtained in step (1) is mixed with PY-DHBD-COF (mass ratio of 0.4:1), ultrasonically dispersed, stirred and reacted for a period of time (120 min), the reaction temperature is 20℃, and after centrifugation, washing and drying, Nb2C QDs@PY-DHBD-COF composite catalyst is obtained. 3 mg of the above catalyst (3#) is weighed and a photocatalytic hydrogen peroxide production experiment is carried out.

[0040] Example 4

[0041] (1) The preparation process of Nb2C MXene, Nb2C QDs and PY-DHBD-COF is the same as in Example 1.

[0042] (2) Preparation of Nb2C QDs@PY-DHBD-COF composite photocatalyst: A certain amount of Nb2C QDs obtained in step (1) was mixed with PY-DHBD-COF (mass ratio 0.6:1), ultrasonically dispersed, stirred and reacted for a period of time (120 min), the reaction temperature was 25℃, and after centrifugation, washing and drying, Nb2C QDs@PY-DHBD-COF composite photocatalyst was obtained. 2.5 mg of the above catalyst (4#) was weighed and a photocatalytic hydrogen peroxide production experiment was carried out.

[0043] Example 5

[0044] (1) The preparation process of Nb2C MXene, Nb2C QDs and PY-DHBD-COF is the same as in Example 1.

[0045] (2) Preparation of Nb2C QDs@PY-DHBD-COF composite photocatalyst: A certain amount of Nb2C QDs obtained in step (1) was mixed with PY-DHBD-COF (mass ratio 0.8:1), ultrasonically dispersed, stirred and reacted for a period of time (120 min), the reaction temperature was 30℃, and after centrifugation, washing and drying, Nb2C QDs@PY-DHBD-COF composite photocatalyst was obtained. 4 mg of the above catalyst (5#) was weighed and a photocatalytic hydrogen peroxide production experiment was carried out.

[0046] Example 6

[0047] (1) The preparation process of Nb2C MXene, Nb2C QDs and PY-DHBD-COF is the same as in Example 1.

[0048] (2) Preparation of Nb2C QDs@PY-DHBD-COF composite photocatalyst: A certain amount of Nb2C QDs obtained in step (1) was mixed with PY-DHBD-COF (mass ratio 1:1), ultrasonically dispersed, stirred and reacted for a period of time (120 min), the reaction temperature was 40℃, and after centrifugation, washing and drying, Nb2C QDs@PY-DHBD-COF composite catalyst was obtained. 2 mg of the above catalyst (6#) was weighed and a photocatalytic hydrogen peroxide production experiment was carried out.

[0049] The Nb2C QDs@PY-DHBD-COF composite photocatalyst provided by this invention can be used for photocatalytic hydrogen peroxide production. The specific operation process is as follows: The prepared catalyst is dispersed in 5-20 mL of deionized water and allowed to adsorb and equilibrate for 5-60 min under dark conditions. Circulating cooling water is introduced into the outer layer to maintain the system temperature at 5-50℃. A 50-500W xenon lamp is turned on as the irradiation source. The hydrogen peroxide yield is determined by iodometric titration.

[0050] The results of using the catalysts of Examples 1-6 for photocatalytic hydrogen peroxide production are shown in Table 1 below.

[0051] Table 1. Hydrogen peroxide production activity test of Nb2C QDs@PY-DHBD-COF photocatalyst

[0052]

Claims

1. A method for preparing an Nb2C QDs@PY-DHBD-COF composite photocatalyst, characterized in that, Using Nb2AlC MAX material as a precursor, Nb2C MXene was etched to obtain Nb2C MXene. Nb2C quantum dots (Nb2C QDs) were then prepared via a hydrothermal method and anchored onto a pyrene-based covalent organic framework PY-DHBD-COF to form a highly efficient and stable composite photocatalyst, denoted as Nb2CQDs@PY-DHBD-COF. The specific steps are as follows: (1) Nb2AlC raw material powder was slowly added to HF solution and stirred continuously. The mixture was reacted, and the reaction product was washed with deionized water, centrifuged, and freeze-dried to obtain product Nb2C MXene. (2) The Nb2C MXene obtained in step (1) is transferred to a reactor, ultrapure water and ammonia are added, and after reaction, the product Nb2C QDs is obtained; (3) Using 1,4-dihydroxybenzidine and 1,3,6,8-tetra(4-formylphenyl)pyrene as monomers, the mixture was reacted by heating; the precipitate was collected, washed with tetrahydrofuran and acetone, and dried under vacuum to obtain the product PY-DHBD-COF; (4) The Nb2C QDs obtained in step (2) are mixed with the PY-DHBD-COF obtained in step (3), ultrasonically dispersed, stirred and reacted, and the product is separated by centrifugation, washed and dried to obtain the Nb2C QDs@PY-DHBD-COF composite photocatalyst; In step (2), the reaction temperature is 80~150℃ and the reaction time is 4~16 h; In step (4), the mass ratio of Nb2C QDs to PY-DHBD-COF is 0.1:1 to 1:1; the reaction temperature is 20 to 50 °C; and the reaction time is 10 to 180 min.

2. The preparation method according to claim 1, characterized in that, In step (1), the mass of Nb2AlC is 0.5~3 g; the concentration of HF is 1~40% and the volume is 10~40 mL; the reaction temperature is 25~40 ℃ and the reaction time is 20~50 h.

3. The preparation method according to claim 1, characterized in that, In step (3), the mass ratio of 1,4-dihydroxybenzidine to 1,3,6,8-tetra(4-formylphenyl)pyrene is 1:1 to 1:4; the reaction temperature is 90 to 150 °C; and the reaction time is 8 to 80 h.

4. The Nb2C QDs@PY-DHBD-COF composite photocatalyst obtained by the preparation method according to any one of claims 1-3.

5. The application of the Nb2C QDs@PY-DHBD-COF composite photocatalyst according to claim 4 in the photocatalytic hydrogen peroxide production reaction.

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