Zirconium-based MOFs composite material loaded with carbon nitride quantum dots and preparation method and application thereof

Abstract

The invention belongs to the field of preparation of photoelectric catalytic materials, and discloses a zirconium-based MOFs composite material loaded with carbon nitride quantum dots as well as a preparation method and application of the zirconium-based MOFs composite material. The composite material is prepared by adopting a solid phase method, and the method is simple, low in cost, easy to amplify, free of toxic solvents and environmentally friendly. The zirconium-based MOFs composite material loaded with the carbon nitride quantum dots prepared by the invention retains the advantages of large specific surface area and rich pore structure of the MOFs material, and shows excellent hydrogen production performance when the zirconium-based MOFs composite material loaded with the carbon nitride quantum dots is used as a photoelectrode material for hydrogen production by photoelectrocatalytic decomposition of water.

Description

Technical Field

[0001] This invention belongs to the field of photoelectrocatalytic material preparation, and relates to a zirconium-based MOF composite material loaded with carbon nitride quantum dots, its preparation method and application. Background Technology

[0002] Photoelectrocatalytic water splitting for hydrogen production has attracted much attention in recent years as a technology that can convert solar energy into hydrogen energy. Compared with direct water electrolysis, photoelectrocatalytic water splitting can produce hydrogen by splitting water under a relatively low applied bias voltage because the photoelectrode can generate a partial photovoltage.

[0003] Metal-organic frameworks (MOFs), also known as porous coordination polymers, are two-dimensional or three-dimensional porous nanomaterials synthesized from secondary building blocks, metal cation salts or clusters, and multidentate organic ligands with coordination linkages. They possess characteristics such as large specific surface area, high porosity, designable structure, and easy functionalization of both the metal center and ligands. MOFs are widely used in gas adsorption and separation, chemical sensing, and biomedicine, and have also shown potential applications in photocatalysis, electrocatalysis, and photoelectrocatalysis. Zirconium (Zr)-based MOFs have advantages such as large specific surface area, good thermal stability, and good chemical stability. However, their narrow band gap, easy electron-hole recombination, and poor electrical conductivity limit the further application of Zr-based MOFs in photoelectrocatalysis.

[0004] Carbon nitride is an organic polymer material composed of tris(triazine) structural units. Due to its tunable band structure, diverse preparation methods, and low cost, it has been widely studied in the field of photocatalysis. However, bulk carbon nitride prepared by traditional direct pyrolysis of nitrogen-rich precursors exhibits poor electron transport performance, resulting in poor photoelectrode conductivity when applied to photoelectrocatalysis. Summary of the Invention

[0005] To overcome the problems of easy electron-hole recombination and poor conductivity when Zr-based MOFs are applied to photoelectrocatalysis, this invention provides a Zr-based MOFs (CNQDs / Zr-MOFs) composite material loaded with carbon nitride quantum dots, its preparation method, and its application. Carbon nitride quantum dots (CNQDs), as electron-capturing hydrazine, can significantly improve the electron-hole separation efficiency of Zr-MOFs. The prepared CNQDs / Zr-MOFs exhibit good photoelectrocatalytic water splitting for hydrogen production.

[0006] To achieve the above objectives, the present invention adopts the following technical solution.

[0007] The first aspect of the present invention is to provide a zirconium-based MOFs composite material loaded with carbon nitride quantum dots, comprising: a zirconium-based MOFs support and loaded carbon nitride quantum dots, wherein the nitrogen element in the carbon nitride quantum dots exists in the form of pyrrole nitrogen.

[0008] According to the present invention, in the zirconium-based MOFs composite material loaded with carbon nitride quantum dots, the nitrogen atom content, in atomic percentage, is 1 to 10 atom%, for example, it can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 atom%, or any value between any two of the above ranges; preferably, the nitrogen atom content is 2 to 5 atom%.

[0009] The second aspect of the present invention is to provide a method for preparing the zirconium-based MOFs composite material loaded with carbon nitride quantum dots as described in the first aspect of the present invention, comprising the steps of mixing and heating a mixture of components including a nitrogen-rich organic precursor, a zirconium salt, and an organic ligand.

[0010] According to the present invention, the preparation method of the zirconium-based MOFs composite material loaded with carbon nitride quantum dots specifically includes the following steps:

[0011] (1) Mix the components including nitrogen-rich organic precursor, organic acid compound, zirconium salt and organic ligand to obtain composite material precursor;

[0012] (2) The composite material precursor obtained in step (1) is subjected to hydrothermal reaction;

[0013] (3) The product after the reaction in step (2) is post-processed to obtain the zirconium-based MOFs composite material loaded with carbon nitride quantum dots.

[0014] According to the present invention, the following operation method is preferably adopted in step (1) of the preparation method of the zirconium-based MOFs composite material loaded with carbon nitride quantum dots: mixing a nitrogen-rich organic precursor and an organic acid compound and grinding them thoroughly to obtain mixture A; mixing a zirconium salt and an organic ligand and grinding them thoroughly to obtain mixture B; mixing mixture A and mixture B and grinding them thoroughly to obtain the composite material precursor.

[0015] The nitrogen-rich organic precursor is selected from at least one of organic amine compounds, preferably from at least one of urea, thiourea, and melamine.

[0016] The organic acid compound is selected from at least one of polyfatty acid compounds, preferably from at least one of C2 to C8 polyfatty acid compounds, and more preferably from at least one of citric acid, malic acid, and oxalic acid.

[0017] The zirconium salt is selected from at least one of soluble inorganic zirconium salts, preferably from at least one of zirconium chloride, zirconium oxychloride octahydrate, and zirconium nitrate;

[0018] The organic ligand is selected from at least one of aromatic polybasic acids or their derivatives, preferably from at least one of terephthalic acid, 2-aminoterephthalic acid, and 2,5-dihydroxyterephthalic acid;

[0019] The molar ratio of the organic acid compound to the nitrogen-rich organic precursor can be adjusted within a wide range. Preferably, the molar ratio of the organic acid compound to the nitrogen-rich organic precursor is 1:(1-50), for example, it can be 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:45, 1:50, or any value between any two of the above ratios. More preferably, the molar ratio of the organic acid compound to the nitrogen-rich organic precursor is 1:(1-10).

[0020] The molar ratio of the zirconium salt to the organic ligand can be adjusted within a wide range. Preferably, the molar ratio of the zirconium salt to the organic ligand is 1:(1-50), for example, it can be 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:45, 1:50, or any value between any two of the above ratios. More preferably, the molar ratio of the zirconium salt to the organic ligand is 1:(1-10).

[0021] The mass ratio of mixture A and mixture B can be adjusted within a wide range. Preferably, the mass ratio of mixture A and mixture B is 1:(1 to 100), for example, it can be 1:1, 1:5, 1:10, 1:15, 1:20, 1:30, 1:40, 1:50, 1:60, 1:70, 1:80, 1:90, 1:100 or any value between any two of the above ratios; more preferably, the mass ratio of mixture A and mixture B is 1:(5 to 20).

[0022] There are no special requirements for the operating conditions of each grinding process. Grinding can be carried out at room temperature until the materials are fully mixed. For example, the grinding time in each grinding process is 5 to 30 minutes.

[0023] According to the present invention, in step (2) of the preparation method of the zirconium-based MOFs composite material loaded with carbon nitride quantum dots:

[0024] The temperature for the hydrothermal reaction is 80–250℃, preferably 120–200℃;

[0025] The hydrothermal reaction time is 1 to 48 hours, preferably 6 to 24 hours.

[0026] According to the present invention, the post-treatment in step (3) of the preparation method of the zirconium-based MOFs composite material loaded with carbon nitride quantum dots can be carried out by commonly used compound treatment methods. For example, the post-treatment includes washing, filtering and drying steps. The solvent used for washing is an alcohol solvent, preferably at least one of ethanol, methanol, and isopropanol; the washing is carried out by stirring, preferably for 1 to 10 hours; the drying temperature is 50 to 200°C, preferably 80 to 180°C, and the drying time is not particularly limited, as long as the obtained product is sufficiently dried.

[0027] A third aspect of the present invention is to provide an electrode material, including the zirconium-based MOFs composite material loaded with carbon nitride quantum dots as described in the first aspect of the present invention or the zirconium-based MOFs composite material loaded with carbon nitride quantum dots obtained by the preparation method described in the second aspect of the present invention.

[0028] The zirconium-based MOFs composite material (CNQDs / Zr-MOFs) supported on carbon nitride quantum dots provided by this invention can be used as an electrode by coating a slurry containing the composite material onto a substrate material according to commonly used electrode preparation methods in the prior art. For example, CNQDs / Zr-MOFs and perfluorosulfonic acid solution are dispersed in a mixed solvent of water and isopropanol to obtain a uniformly dispersed slurry. After coating the slurry onto a cleaned FTO substrate, it can be used directly as an electrode.

[0029] The fourth aspect of the present invention is to provide the application of the zirconium-based MOFs composite material loaded with carbon nitride quantum dots as described in the first aspect of the present invention, or the zirconium-based MOFs composite material loaded with carbon nitride quantum dots obtained by the preparation method described in the second aspect of the present invention, or the electrode material described in the third aspect of the present invention, in photoelectrocatalytic water splitting to produce hydrogen.

[0030] The technical solution of the present invention has the following beneficial effects:

[0031] (1) The preparation method provided by the present invention is simple, low cost, easy to scale up and does not require the use of toxic solvents, making it green and environmentally friendly.

[0032] (2) The CNQDs / Zr-MOFs prepared by the method provided by the present invention retain the advantages of large specific surface area and rich pore structure of MOFs materials, and can provide sufficient active sites for the reaction in photoelectrocatalytic reaction.

[0033] (3) The CNQDs / Zr-MOFs provided by this invention exhibit excellent hydrogen production performance as photoelectrode materials in photoelectrocatalytic water splitting for hydrogen production. The performance was demonstrated at a test voltage of 1.23V vs. RHE and a light intensity of 100mW / cm². 2At that time, the hydrogen production rate reached 16 μmol / cm. 2 / h. Attached Figure Description

[0034] Figure 1 This is a pore size distribution diagram of CNQDs / Zr-MOFs prepared in Example 1 of this invention; where the horizontal axis represents the pore size (in nm) and the vertical axis represents the pore area (in cm²). 3 ·g -1 ·nm -1 ).

[0035] Figure 2 This is the XRD pattern of CNQDs / Zr-MOFs prepared in Example 1 of the present invention; wherein, the horizontal axis is twice the incident angle of the X-rays, and the vertical axis is the diffraction intensity.

[0036] Figure 3 This is the XPS spectrum of CNQDs / Zr-MOFs prepared in Example 1 of this invention; where the horizontal axis represents the binding energy (unit eV) and the vertical axis represents the relative intensity (unit au).

[0037] Figure 4 This is the XPS high-resolution N1s spectrum of CNQDs / Zr-MOFs prepared in Example 1 of this invention; where the horizontal axis represents the binding energy (unit eV) and the vertical axis represents the relative intensity (unit au).

[0038] Figure 5 This is a graph showing the hydrogen production of CNQDs / Zr-MOFs prepared in Example 1 of this invention; where the horizontal axis represents time (in min) and the vertical axis represents hydrogen production (in μmol / cm³). 2 ). Detailed Implementation

[0039] The present invention will now be described in detail with reference to specific embodiments and accompanying drawings. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0040] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the ranges, the endpoint values ​​of the ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0041] According to a preferred embodiment of the present invention, the present invention provides a method for preparing a zirconium-based MOF composite material (CNQDs / Zr-MOFs) loaded with carbon nitride quantum dots, comprising:

[0042] (1) A nitrogen-rich organic precursor, an organic acid compound, a zirconium salt and an organic ligand are mixed at room temperature to obtain a composite material precursor;

[0043] (2) The composite material precursor was heated and reacted in a closed reactor to obtain unpurified CNQDs / Zr-MOFs;

[0044] (3) The unpurified CNQDs / Zr-MOFs were washed, filtered and dried to obtain CNQDs / Zr-MOFs.

[0045] In this invention, the type of nitrogen-rich organic precursor is not particularly limited, but is preferably at least one of organic amine compounds, and more preferably at least one of urea, thiourea, and melamine.

[0046] In this invention, the organic acid compound can be an organic acid conventionally used in the art, preferably at least one of polyfatty acid compounds, more preferably at least one of C2 to C8 polyfatty acid compounds, and even more preferably at least one of citric acid, malic acid, and oxalic acid.

[0047] In this invention, the zirconium salt can be at least one of the soluble inorganic zirconium salts commonly used in the art, preferably at least one of zirconium chloride, zirconium oxychloride octahydrate, and zirconium nitrate.

[0048] In this invention, the organic ligand is at least one of an aromatic polybasic acid or its derivative, preferably at least one of terephthalic acid, 2-aminoterephthalic acid, and 2,5-dihydroxyterephthalic acid.

[0049] In this invention, the mixing order of the nitrogen-rich precursor, organic acid, zirconium salt, and organic ligand in step (1) is not particularly restricted; they can be mixed simultaneously or added separately for mixing. Preferably, step (1) further includes:

[0050] (i) The nitrogen-rich organic precursor and the organic acid compound are thoroughly ground at room temperature to obtain mixture A;

[0051] (ii) The zirconium salt and organic ligand are thoroughly ground at room temperature to obtain mixture B;

[0052] (iii) Mix mixture A and mixture B and then grind them thoroughly to obtain the composite material precursor.

[0053] In this invention, the molar ratio of organic acid compound to nitrogen-rich organic precursor can be selected within a wide range. Preferably, the molar ratio of organic acid compound to nitrogen-rich organic precursor is 1:(1-50), more preferably 1:(1-10).

[0054] The grinding conditions for the mixed nitrogen-rich organic precursor and organic acid compound are not particularly limited, but preferably, grinding at room temperature for 5 to 30 minutes is preferred.

[0055] In this invention, the molar ratio of zirconium salt to organic ligand can be selected within a wide range. Preferably, the molar ratio of zirconium salt to organic ligand is 1:(1-50), more preferably 1:(1-10).

[0056] The grinding conditions for the zirconium salt and organic ligand can be unrestricted, but preferably, grinding at room temperature for 5 to 30 minutes is preferred.

[0057] In this invention, the mass ratio of mixture A to mixture B can be selected within a wide range, wherein, preferably, the mass ratio of mixture A to mixture B is 1:(1 to 100), more preferably 1:(5 to 20);

[0058] The mixing and grinding conditions of mixture A and mixture B are not particularly limited, but preferably, grinding at room temperature for 5 to 30 minutes is preferred.

[0059] In this invention, the heating reaction conditions in step (2) can be those conventionally used in the art, preferably including: a temperature of 80 to 250°C and a time of 1 to 48 hours; more preferably including: a temperature of 120 to 200°C and a time of 6 to 24 hours.

[0060] In this invention, the cleaning conditions in step (3) can be those conventionally used in the art, such as adding a cleaning solvent and stirring for cleaning. Preferably, the cleaning solvent is ethanol, the cleaning time is 1 to 10 hours, and the product is dried at 50 to 200°C after filtration.

[0061] The present invention provides a zirconium-based MOF composite material (CNQDs / Zr-MOFs) loaded with carbon nitride quantum dots prepared by the method described above.

[0062] In a preferred embodiment of the present invention, the pore size distribution of the obtained CNQDs / Zr-MOFs is as follows: Figure 1 As shown in the figure, the CNQDs / Zr-MOFs provided by the present invention contain micropores of ~1nm and have a rich pore structure.

[0063] In a preferred embodiment of the present invention, the XRD pattern of the obtained CNQDs / Zr-MOFs is as follows: Figure 2As shown in the figure, CNQDs / Zr-MOFs exhibit good crystallinity, and the addition of carbon nitride quantum dots (CNQDs) does not disrupt the original crystal structure of Zr-MOFs.

[0064] In a preferred embodiment of the present invention, the XPS spectra of the obtained CNQDs / Zr-MOFs are as follows: Figure 3 As shown in the figure, the CNQDs / Zr-MOFs provided by this invention contain carbon, oxygen, nitrogen and zirconium elements, with a nitrogen content of 3.35 atom%.

[0065] In a preferred embodiment of the present invention, the obtained high-resolution XPS N1s spectrum of CNQDs / Zr-MOFs is as follows: Figure 4 As shown in the figure, the nitrogen element in CNQDs / Zr-MOFs provided by this invention exists in the form of pyrrole nitrogen.

[0066] In this invention, the pore size distribution map is obtained by nitrogen adsorption-desorption measurement.

[0067] In this invention, the XRD pattern is obtained by an X-ray diffractometer.

[0068] In this invention, the XPS spectrum is obtained by X-ray electron spectrometer.

[0069] The present invention also provides an electrode material comprising CNQDs / Zr-MOFs as described above, and its application in photoelectrocatalytic water splitting for hydrogen production.

[0070] In a preferred embodiment of the present invention, the hydrogen production diagram of the obtained photoelectrocatalytic CNQDs / Zr-MOFs is shown below. Figure 5 As shown in the figure, during the test period, the test voltage was 1.23V vs. RHE, and the light intensity was 100mW / cm². 2 At that time, the hydrogen production rate was 16 μmol / cm. 2 / h.

[0071] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, such as those that can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0072] The present invention will be described in detail below through embodiments.

[0073] Example 1

[0074] This embodiment illustrates the preparation method and application of CNQDs / Zr-MOFs described in this invention.

[0075] Preparation of CNQDs / Zr-MOFs:

[0076] (1) Grind 0.21g of citric acid and 0.18g of urea in a mortar for 15 minutes at room temperature to obtain mixture A. Grind 0.64g of zirconium oxychloride octahydrate and 0.34g of terephthalic acid in a mortar for 15 minutes at room temperature to obtain mixture B. Grind 0.05g of mixture A and 0.5g of mixture B in a mortar for 15 minutes at room temperature to obtain the precursor.

[0077] (2) The precursor was transferred to a hydrothermal reactor, sealed, and reacted at 180°C for 12 h to obtain unpurified CNQDs / Zr-MOFs.

[0078] (3) Transfer the unpurified CNQDs / Zr-MOFs to a beaker, add 100 mL of ethanol, stir and wash for 6 h, then filter and dry at 100 °C for 24 h to obtain CNQDs / Zr-MOFs.

[0079] The specific surface area and pore size distribution of CNQDs / Zr-MOFs were obtained by nitrogen adsorption-desorption tests (see...). Figure 1 As can be seen from the figure, the specific surface area of ​​CNQDs / Zr-MOFs obtained in Example 1 is 875 m². 2 It contains ~1nm micropores and has a rich pore structure. Figure 2 The XRD pattern of CNQDs / Zr-MOFs shows that CNQDs / Zr-MOFs exhibit good crystallinity, and the addition of CNQDs does not disrupt the original crystal structure of Zr-MOFs. The elemental composition of CNQDs / Zr-MOFs was determined, and the XPS spectrum is shown below. Figure 3 As shown in the figure, the CNQDs / Zr-MOFs obtained in Example 1 contain carbon, oxygen, nitrogen, and zirconium, with a nitrogen content of 3.35 atom%. The XPS high-resolution N1s spectrum is shown below. Figure 4 As shown in the figure, the nitrogen element in CNQDs / Zr-MOFs obtained in Example 1 exists in the form of pyrrole nitrogen.

[0080] Applications of CNQDs / Zr-MOFs:

[0081] This application example illustrates the performance of CNQDs / Zr-MOFs as photoelectrodes in the photoelectrocatalytic water splitting for hydrogen production.

[0082] 10 mg of CNQDs / Zr-MOFs from Example 1 and 0.01 mL of perfluorosulfonic acid solution were ultrasonically dispersed in 10 mL of a mixed solvent of water and isopropanol (volume ratio 3:1) to obtain a uniformly dispersed slurry. The FTO conductive glass substrate was ultrasonically cleaned in water and ethanol, respectively, and then dried in an oven. The prepared slurry was uniformly coated onto the FTO substrate, controlling the area to be 1 cm². 2 A square.

[0083] The photoelectrochemical hydrogen production performance of the samples was tested using a sealed electrolytic cell at ambient temperature and pressure. The electrode prepared above and loaded with CNQDs / Zr-MOFs was used as the working electrode, and a Pt electrode as the counter electrode. A 1M borate buffer solution was used as the electrolyte. The test was conducted under backlight irradiation, and the hydrogen content was detected using gas chromatography.

[0084] Figure 5 The graph shows the hydrogen production in Example 1, measured at a voltage of 1.23V vs. RHE and an irradiance of 100mW / cm². 2 Under these conditions, the hydrogen production rate is 16 μmol / cm. 2 / h.

[0085] Example 2

[0086] This embodiment illustrates the preparation method and application of CNQDs / Zr-MOFs described in this invention.

[0087] Preparation of CNQDs / Zr-MOFs:

[0088] The procedure is performed according to the method described in Example 1, except that 0.05g of mixture A in step (1) is replaced with 0.025g of mixture A.

[0089] Applications of CNQDs / Zr-MOFs:

[0090] The procedure was followed as in Example 1, except that the working electrode was replaced with a working electrode made of the CNQDs / Zr-MOFs material obtained in Example 2. The test voltage was 1.23V vs. RHE, and the light intensity was 100mW / cm². 2 Under these conditions, the hydrogen production rate is 12 μmol / cm. 2 / h.

[0091] Example 3

[0092] This embodiment illustrates the preparation method and application of CNQDs / Zr-MOFs described in this invention.

[0093] Preparation of CNQDs / Zr-MOFs:

[0094] The procedure is performed according to the method described in Example 1, except that 0.05g of mixture A in step (1) is replaced with 0.1g of mixture A.

[0095] Applications of CNQDs / Zr-MOFs:

[0096] The procedure was followed as in Example 1, except that the working electrode was replaced with a working electrode made of the CNQDs / Zr-MOFs material obtained in Example 3. The test voltage was 1.23V vs. RHE, and the light intensity was 100mW / cm². 2 Under these conditions, the hydrogen production rate is 10 μmol / cm. 2 / h.

[0097] Example 4

[0098] This embodiment illustrates the preparation method and application of CNQDs / Zr-MOFs described in this invention.

[0099] Preparation of CNQDs / Zr-MOFs:

[0100] The procedure was performed according to the method described in Example 1, except that 0.34g of terephthalic acid in step (1) was replaced with 0.72g of 2-aminoterephthalic acid.

[0101] Applications of CNQDs / Zr-MOFs:

[0102] The procedure was followed as in Example 1, except that the working electrode was replaced with a working electrode made of the CNQDs / Zr-MOFs material obtained in Example 4. The test voltage was 1.23V vs. RHE, and the light intensity was 100mW / cm². 2 Under these conditions, the hydrogen production rate is 11 μmol / cm. 2 / h.

[0103] Example 5

[0104] This embodiment illustrates the preparation method and application of CNQDs / Zr-MOFs described in this invention.

[0105] Preparation of CNQDs / Zr-MOFs:

[0106] The procedure is performed according to the method described in Example 1, except that 0.21g of citric acid in step (1) is replaced with 0.07g of citric acid.

[0107] Applications of CNQDs / Zr-MOFs:

[0108] The procedure was followed as in Example 1, except that the working electrode was replaced with a working electrode made of the CNQDs / Zr-MOFs material obtained in Example 5. The test voltage was 1.23V vs. RHE, and the light intensity was 100mW / cm². 2 Under these conditions, the hydrogen production rate is 10 μmol / cm. 2 / h.

[0109] Comparative Example 1

[0110] This comparative example illustrates the performance of Zr-MOF without CNQDs in photoelectrocatalytic water splitting for hydrogen production.

[0111] Zr-MOFs were prepared using the following method:

[0112] (1) Grind 0.64 g of zirconium oxychloride octahydrate and 0.34 g of terephthalic acid in a mortar for 15 min at room temperature to obtain the precursor.

[0113] (2) The precursor was transferred to a hydrothermal reactor, sealed, and reacted at 180°C for 12 h to obtain unpurified Zr-MOFs.

[0114] (3) Transfer the unpurified Zr-MOFs to a beaker, add 100 mL of ethanol solution, stir and wash for 6 h, then filter and dry at 100 °C for 24 h to obtain Zr-MOFs.

[0115] Performance testing was conducted according to the method in Example 1, except that the working electrode was replaced with a working electrode prepared from the aforementioned material. The test voltage was 1.23V vs. RHE, and the light intensity was 100mW / cm². 2 Under these conditions, the hydrogen production rate is 5 μmol / cm. 2 / h.

[0116] Comparative Example 2

[0117] This comparative example illustrates the performance of Zr-MOF (carbon black / Zr-MOF) supported on conductive carbon black when applied to photoelectrocatalytic water splitting for hydrogen production.

[0118] Carbon black / Zr-MOF is prepared as follows:

[0119] (1) Grind 0.05g of conductive carbon black, 0.64g of zirconium oxychloride octahydrate and 0.34g of terephthalic acid in a mortar for 15min at room temperature to obtain the precursor.

[0120] (2) The precursor was transferred to a hydrothermal reactor, sealed, and reacted at 180°C for 12 h to obtain unpurified carbon black / Zr-MOF.

[0121] (3) Transfer the unpurified carbon black / Zr-MOF to a beaker, add 100 mL of ethanol solution, stir and wash for 6 h, then filter, and dry at 100 °C for 24 h to obtain carbon black / Zr-MOF.

[0122] Performance testing was conducted according to the method in Example 1, except that the working electrode was replaced with a working electrode prepared from the aforementioned material. The test voltage was 1.23V vs. RHE, and the light intensity was 100mW / cm². 2 Under these conditions, the hydrogen production rate is 8 μmol / cm. 2 / h.

Claims

1. A zirconium-based MOF composite material supported on carbon nitride quantum dots, comprising: Zirconium-based MOFs support and loaded carbon nitride quantum dots, wherein the nitrogen element in the carbon nitride quantum dots exists in the form of pyrrole nitrogen.

2. The zirconium-based MOFs composite material supported on carbon nitride quantum dots according to claim 1, characterized in that, In the zirconium-based MOFs composite material loaded with carbon nitride quantum dots, the nitrogen atom content is 1-10 atom%, preferably 2-5 atom%.

3. A method for preparing a zirconium-based MOF composite material loaded with carbon nitride quantum dots as described in any one of claims 1 to 2, comprising the steps of mixing and heating a mixture containing a nitrogen-rich organic precursor, a zirconium salt, and an organic ligand.

4. The preparation method according to claim 3, characterized in that, Specifically, the following steps are included: (1) Mix the components including nitrogen-rich organic precursor, organic acid compound, zirconium salt and organic ligand to obtain composite material precursor; (2) The composite material precursor obtained in step (1) is subjected to hydrothermal reaction; (3) The product after the reaction in step (2) is post-processed to obtain the zirconium-based MOFs composite material loaded with carbon nitride quantum dots.

5. The preparation method according to claim 4, characterized in that, The following operation method is adopted in step (1): the nitrogen-rich organic precursor and organic acid compound are mixed and ground thoroughly to obtain mixture A, the zirconium salt and organic ligand are mixed and ground thoroughly to obtain mixture B, and mixture A and mixture B are mixed and ground thoroughly to obtain composite material precursor.

6. The preparation method according to claim 4 or 5, characterized in that, In step (1): The nitrogen-rich organic precursor is selected from at least one organic amine compound, preferably from at least one of urea, thiourea, and melamine; and / or, The organic acid compound is selected from at least one of polyfatty acid compounds, preferably from at least one of C2-C8 polyfatty acid compounds, more preferably from at least one of citric acid, malic acid, and oxalic acid; and / or, The zirconium salt is selected from at least one of soluble inorganic zirconium salts, preferably from at least one of zirconium chloride, zirconium oxychloride octahydrate, and zirconium nitrate; and / or, The organic ligand is selected from at least one of aromatic polybasic acids or their derivatives, preferably from at least one of terephthalic acid, 2-aminoterephthalic acid, and 2,5-dihydroxyterephthalic acid; and / or, The molar ratio of the organic acid compound to the nitrogen-rich organic precursor is 1:(1-50), preferably 1:(1-10); and / or, The molar ratio of the zirconium salt to the organic ligand is 1:(1-50), preferably 1:(1-10).

7. The preparation method according to claim 5, characterized in that, The mass ratio of mixture A to mixture B is 1:(1-100), preferably 1:(5-20).

8. The preparation method according to claim 4, characterized in that, In step (2): The hydrothermal reaction temperature is 80–250°C, preferably 120–200°C; and / or, The hydrothermal reaction time is 1 to 48 hours, preferably 6 to 24 hours.

9. The preparation method according to claim 4, characterized in that, The post-processing in step (3) includes washing, filtering, and drying; preferably, The solvent used for cleaning is an alcohol solvent, more preferably at least one selected from ethanol, methanol, and isopropanol; and / or, The cleaning is performed by agitation cleaning, and more preferably, the agitation cleaning time is 1–10 hours; and / or, The drying temperature is 50–200°C, more preferably 80–180°C.

10. An electrode material comprising the zirconium-based MOFs composite material loaded with carbon nitride quantum dots as described in any one of claims 1 to 2, or the zirconium-based MOFs composite material loaded with carbon nitride quantum dots obtained by the preparation method described in any one of claims 3 to 9.

11. The application of a zirconium-based MOFs composite material loaded with carbon nitride quantum dots as described in any one of claims 1 to 2, or a zirconium-based MOFs composite material loaded with carbon nitride quantum dots obtained by the preparation method described in any one of claims 3 to 9, or an electrode material as described in claim 10, in photoelectrocatalytic water splitting for hydrogen production.

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