A MOF-derived Cu / t-ZrO2 bimetallic heterojunction catalyst, its preparation method and application

Abstract

The application discloses a MOF derived Cu / t-ZrO2 bimetallic heterojunction catalyst and a preparation method and application thereof, and belongs to the technical field of photocatalyst materials.The preparation method of the catalyst comprises the following steps: adding an organic ligand suspension into a mixed solution of a copper source and 1,2-bis(diphenylphosphino)ethane, and mixing and reacting under anhydrous and oxygen-free conditions to obtain a copper-doped organic ligand material; the copper-doped organic ligand material and a zirconium source are mixed by using an organic solvent and then heated to react, so as to obtain a copper-doped zirconium metal organic framework material; and the copper-doped zirconium metal organic framework material is calcined in an air atmosphere and then heat-treated in an inert atmosphere, so as to obtain the MOF derived Cu / t-ZrO2 bimetallic heterojunction catalyst.The MOF derived Cu / t-ZrO2 bimetallic heterojunction catalyst can realize efficient, stable and low-cost conversion of solar energy-hydrogen energy.

Description

Technical Field

[0001] This invention relates to the field of photocatalyst materials technology, and in particular to a MOF-derived Cu / t-ZrO2 bimetallic heterojunction catalyst, its preparation method, and its application. Background Technology

[0002] Hydrogen energy, as a clean energy carrier, possesses significant advantages such as high energy density (approximately 142 MJ / kg, three times that of traditional gasoline) and water as a combustion product with no pollution, making it a key component of the future energy system. More importantly, hydrogen can be produced greenly using renewable energy sources such as solar and wind power, helping to build a clean and efficient energy cycle and providing new ideas for the coordinated solution of global energy and environmental issues.

[0003] However, currently, approximately 90% of global hydrogen production still relies on fossil fuel reforming, with each ton of hydrogen produced resulting in 9-12 tons of CO2 emissions, exacerbating the increasingly serious carbon emission problem. Therefore, there is an urgent need to develop green hydrogen production technologies driven by renewable energy sources. Against this backdrop, solar-based photothermal catalytic reforming for hydrogen production has become a current research hotspot. Among various available hydrogen production reactions, methanol reforming offers numerous advantages: methanol has a high hydrogen storage density (approximately twice that of traditional liquid organic hydrogen carriers), low toxicity, wide availability, low price, and a mature supply chain, making it a widely used substrate in photocatalytic hydrogen production research. Although various photocatalytic materials have been used in methanol aqueous reforming reactions, many challenges remain. For example, TiO2 only responds to ultraviolet light, resulting in low quantum efficiency; sulfides are prone to photocorrosion and have poor stability; metal oxides have wide band gaps, leading to low utilization of visible light; g-C3N4 has a small specific surface area and a high recombination rate of photogenerated carriers; while composite catalysts offer significant performance improvements, their synthesis routes are typically complex and costly, hindering large-scale applications. Therefore, developing a high-performance photocatalyst that combines structural stability, photothermal responsiveness, and catalytic synergy is key to improving the efficiency of hydrogen production from low-temperature methanol reforming. Summary of the Invention

[0004] The purpose of this invention is to provide a MOF-derived Cu / t-ZrO2 bimetallic heterojunction catalyst, its preparation method, and its application, in order to solve the problems existing in the prior art.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] One of the technical solutions of the present invention: a method for preparing a MOF-derived Cu / t-ZrO2 bimetallic heterojunction catalyst, comprising the following steps:

[0007] An organic ligand suspension was added to a mixed solution of copper source and 1,2-bis(diphenylphosphine)ethane, and the mixture was reacted under anhydrous and oxygen-free conditions to obtain copper-doped organic ligand material.

[0008] The copper-doped organic ligand material and the zirconium source were mixed with an organic solvent and then heated to react, thereby obtaining a copper-doped zirconium-based metal-organic framework material.

[0009] The copper-doped zirconium-based metal-organic framework material was calcined in air and then heat-treated in an inert atmosphere to obtain the MOF-derived Cu / t-ZrO2 bimetallic heterojunction catalyst.

[0010] Preferably, the copper source includes copper hexafluorophosphate tetraacetonitrile, copper acetate monohydrate, or copper chloride dihydrate, more preferably copper hexafluorophosphate tetraacetonitrile; the catalyst prepared using copper hexafluorophosphate tetraacetonitrile as the copper source exhibits the best photothermal catalytic performance in methanol reforming for hydrogen production.

[0011] Preferably, the mass ratio of copper to 1,2-bis(diphenylphosphine)ethane in the copper source is (0.07-0.16):1, more preferably 0.158:1;

[0012] The organic ligands in the organic ligand suspension include 2,2'-bipyridine-5,5'-dicarboxylic acid;

[0013] The mass ratio of the organic ligand to copper in the copper source is 1:(0.05-0.15), preferably 1:0.12.

[0014] Preferably, the solvent in the mixed solution of the copper source and 1,2-bis(diphenylphosphine)ethane includes dichloromethane;

[0015] The solvent in the organic ligand suspension includes dichloromethane and N,N-dimethylformamide in a volume ratio of (4-9):1, more preferably 9:1.

[0016] Preferably, the mixing reaction is carried out at a speed of 300-500 rpm for 5-7 hours.

[0017] Preferably, the zirconium source includes zirconium tetrachloride or zirconium oxychloride;

[0018] Preferably, the mass ratio of the copper-doped organic ligand material to the zirconium source is (1.8-2):1, more preferably 2:1.

[0019] Preferably, the heating reaction is carried out at a temperature of 100–120°C for a duration of 36–72 h.

[0020] More preferably, the heating reaction is carried out at a temperature of 120°C for 48 hours.

[0021] Preferably, the calcination heating rate is 2-5℃ / min, the temperature is 400-500℃, and the holding time is 1.5-3h;

[0022] The heating rate of the heat treatment is 2-5℃ / min, the temperature is 250-350℃, and the holding time is 1.5-3h.

[0023] The MOF-derived Cu / t-ZrO2 bimetallic heterojunction catalyst disclosed in this invention synergistically forms two spatially separated active centers with electron-rich Cu and hydrophilic tetragonal ZrO2 (t-ZrO2), exhibiting highly efficient CH and OH bond breaking and activation capabilities. Under photothermal catalytic coupling, this catalyst can efficiently catalyze the aqueous reforming reaction of methanol at low temperatures, achieving efficient hydrogen release and demonstrating excellent catalytic activity and stability. This provides a novel approach and feasible pathway for developing new green hydrogen production catalytic materials.

[0024] The second technical solution of the present invention: a MOF-derived Cu / t-ZrO2 bimetallic heterojunction catalyst prepared by the above preparation method.

[0025] The third technical solution of the present invention: the application of the above-mentioned MOF-derived Cu / t-ZrO2 bimetallic heterojunction catalyst in photothermal catalytic methanol reforming for hydrogen production.

[0026] Preferably, the methanol reforming for hydrogen production is methanol liquid-phase reforming for hydrogen production.

[0027] Preferably, the method of the application includes: adding a MOF-derived Cu / t-ZrO2 bimetallic heterojunction catalyst to a mixed solution of methanol, water and an alkaline source, and then subjecting it to anaerobic conditions by light irradiation and heating to produce hydrogen.

[0028] Preferably, the molar ratio of methanol to water is 1:(1-3); the alkali source includes potassium hydroxide and / or sodium hydroxide; the amount of alkali source used is 1-5% of the mass of the mixed solution; the heating temperature is 120-210°C; and the illumination is provided by a 300W xenon lamp.

[0029] The present invention discloses the following technical effects:

[0030] The MOF-derived Cu / t-ZrO2 bimetallic heterojunction catalyst of this invention overcomes the problems of "low light absorption, easy charge recombination, instability, slow reaction, and metal agglomeration" existing in traditional single MOF catalysts and copper-based catalytic materials, and finally achieves efficient, stable, and low-cost solar-to-hydrogen energy conversion. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 Transmission electron microscopy (TEM) images of D-Cu / Zr-MOF prepared in step (2) of Example 1, MD-Cu / t-ZrO2 prepared in step (3) of Example 1, and Zr-MOF prepared in Comparative Example 2, wherein (a) to (c) are Zr-MOF prepared in Comparative Example 2, (d) to (f) are D-Cu / Zr-MOF prepared in step (2) of Example 1, and (g) to (h) are MD-Cu / t-ZrO2 prepared in step (3) of Example 1;

[0033] Figure 2 The images shown are high-magnification transmission electron microscope (TEM) images of MD-Cu / t-ZrO2 prepared in step (3) of Example 1, where (a) and (b) are both high-magnification TEM images.

[0034] Figure 3 XRD patterns of D-Cu / Zr-MOF prepared in step (2) of Example 1, MD-Cu / t-ZrO2 prepared in step (3) of Example 1, and Zr-MOF prepared in Comparative Example 2;

[0035] Figure 4 The figure shows the comparison of the long-term stability of MD-Cu / t-ZrO2 prepared in step (3) of Example 1 and Cu / Cu2O+MD-ZrO2 prepared in Effect Example 3;

[0036] Figure 5 The photothermal catalytic methanol liquid-phase reforming hydrogen production performance of MD-Cu / t-ZrO2 prepared in step (3) of Example 1 under different conditions;

[0037] Figure 6 The figure shows a comparison of the photothermal catalytic performance of the catalysts prepared in the examples and comparative examples for hydrogen production from methanol liquid-phase reforming. Detailed Implementation

[0038] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0039] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0040] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0041] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0042] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0043] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0044] In a first aspect, this invention provides a method for preparing a MOF-derived Cu / t-ZrO2 bimetallic heterojunction catalyst, comprising the following steps:

[0045] (1) Add copper source and 1,2-bis(diphenylphosphine) ethane to a dry three-necked flask, then add anhydrous dichloromethane, and use a double-row tube device (Schlenk) to perform freezing-vacuuming-thawing operations to remove oxygen from the flask and continuously and stably input nitrogen gas, and stir it at room temperature and inert atmosphere at a speed of 300-500 rpm for 60-90 min to obtain mixed solution A;

[0046] The organic ligand was added to a mixed solution of anhydrous dichloromethane and anhydrous N,N-dimethylformamide. After being dissolved uniformly by ultrasonication, the solution was deoxygenated using a double-row tube device to obtain mixed solution B.

[0047] Mixed solution B was added dropwise to mixed solution A, and the solution color was observed to gradually change from colorless to reddish-brown. The mixture was stirred at room temperature and under a nitrogen atmosphere at a speed of 300-500 rpm for 5-7 hours. After the reaction was completed, the mixture was concentrated to 1-2 mL under reduced pressure, and a large amount of diethyl ether was added for recrystallization. The solid product was obtained by filtration and freeze-drying. Finally, the product was collected, sealed and stored to obtain the copper-doped organic ligand material (i.e., D-Cu, [Cu(H2bpydc)(dppe)]PF6).

[0048] This step is carried out under anhydrous and oxygen-free conditions.

[0049] (2) The copper-doped organic ligand material and the zirconium source were ultrasonically mixed with an organic solvent (N,N-dimethylformamide) and then heated to react. After centrifugation, washing, drying, and pulverizing, copper-doped zirconium-based metal-organic framework material (i.e., D-Cu / Zr-MOF) was obtained.

[0050] (3) The copper-doped zirconium-based metal-organic framework material was calcined in air and then heat-treated in an inert atmosphere to obtain the MOF-derived Cu / t-ZrO2 bimetallic heterojunction catalyst (i.e., MD-Cu / t-ZrO2).

[0051] In a specific embodiment of the present invention, in step (1), the copper source includes copper hexafluorophosphate tetraacetonitrile, copper acetate monohydrate or copper chloride dihydrate, preferably copper hexafluorophosphate tetraacetonitrile.

[0052] The mass ratio of copper source to 1,2-bis(diphenylphosphine)ethane is (0.07–0.16):1, preferably 0.158:1;

[0053] Organic ligands include 2,2'-bipyridine-5,5'-dicarboxylic acid;

[0054] The mass ratio of organic ligand to copper source is 1:(0.05-0.15), preferably 1:0.12; the catalyst prepared under this ratio has the best hydrogen production effect in photothermal catalytic methanol reforming.

[0055] The volume ratio of anhydrous dichloromethane to anhydrous N,N-dimethylformamide is (4-9):1, preferably 9:1.

[0056] In a specific embodiment of the present invention, in step (2), the zirconium source includes zirconium tetrachloride or zirconium oxychloride octahydrate;

[0057] The mass ratio of copper-doped organic ligand material to zirconium source is (1.8-2):1, preferably 2:1;

[0058] The temperature of the heating reaction is 100-120℃, preferably 120℃; the heating reaction time is 36-72h, preferably 48h.

[0059] In a specific embodiment of the present invention, in step (3), the heating rate of calcination is 2-5℃ / min, the temperature is 400-500℃, and the holding time is 1.5-3h;

[0060] The heating rate for heat treatment is 2–5℃ / min, the temperature is 250–350℃, and the holding time is 1.5–3h.

[0061] The inert atmosphere is nitrogen, and the flow rate is 50 mL / min;

[0062] Centrifugation, washing, and drying include washing three times with N,N-dimethylformamide and ethanol until the supernatant is clear and transparent (centrifugation speed is 10000 rpm), and then placing it in a vacuum drying oven at 60°C for 12 hours.

[0063] In a specific embodiment of the present invention, in step (3), the heating rate of calcination is 2℃ / min, the temperature is 450℃, and the holding time is 2h;

[0064] The heating rate for heat treatment was 2℃ / min, the temperature was 300℃, and the holding time was 2h.

[0065] This invention employs the Schlenk technique to synthesize copper-doped organic ligand materials. Utilizing the strong coordination ability of 2,2'-bipyridine-5,5'-dicarboxylic acid with copper ions, the active component copper is effectively anchored within the MOF precursor structure, resulting in more stable active sites that are less prone to detachment. Subsequently, zirconium salt is introduced under hydrothermal conditions to synthesize copper-doped zirconium-based metal-organic framework materials. Finally, through a two-step heat treatment strategy (i.e., first calcination in air to control the metal oxidation state or form a crystalline phase, allowing the metal salt to be dispersed, enhancing material stability, increasing active sites, and regulating pore structure and conductivity; then heat treatment in an inert atmosphere to remove the organic ligands, forming a porous structure and stabilizing the framework structure), a MOF-derived Cu / t-ZrO2 bimetallic heterojunction catalyst with a dual active center structure (abbreviated as MD-Cu / t-ZrO2) is prepared. In the heterojunction constructed in this invention, a stable metal-semiconductor interface can be formed between metallic copper and tetragonal ZrO2 (t-ZrO2), which can effectively regulate the electron transfer path, reduce the activation energy barrier of the reactants, and significantly improve the electron-hole pair separation and migration efficiency, thereby enhancing the photothermal synergistic hydrogen release performance of the catalyst in low-temperature reforming of methanol-water solution. The catalyst prepared in this invention exhibits excellent low-temperature hydrogen production activity and stability under alkaline conditions, and has good industrial scale-up potential and application prospects.

[0066] The method of this invention can achieve control over the catalyst structure and improve the dispersibility of metal species.

[0067] The catalyst constructed in this invention utilizes a stable metal-semiconductor interface formed between metallic copper and tetragonal ZrO2 (t-ZrO2) to regulate electron transfer, lower the activation energy barrier of reactants, and simultaneously enhance catalytic activity and selectivity, achieving a hydrogen selectivity of up to 96%. Specifically, metallic copper dissociates methanol CH bonds and weakly adsorbs CO intermediates, while tetragonal ZrO2 directionally dissociates water molecules to provide active OH groups to scavenge CO. This dual-functionality enables spatial separation and directional activation of methanol and water molecules, optimizing the reaction pathway, inhibiting excessive accumulation of CO* intermediates, thereby alleviating carbon poisoning on the catalyst surface and achieving efficient and stable solar-to-hydrogen energy conversion.

[0068] In a second aspect, the present invention provides a MOF-derived Cu / t-ZrO2 bimetallic heterojunction catalyst prepared by the above preparation method.

[0069] In a third aspect, the present invention provides an application of the above-mentioned MOF-derived Cu / t-ZrO2 bimetallic heterojunction catalyst in photothermal catalytic methanol reforming for hydrogen production.

[0070] In a specific embodiment of the present invention, methanol reforming for hydrogen production is methanol liquid-phase reforming for hydrogen production.

[0071] In a specific embodiment of the present invention, the method of application includes: adding a MOF-derived Cu / t-ZrO2 bimetallic heterojunction catalyst to a mixed solution of methanol, water and an alkaline source, and then subjecting it to anaerobic conditions by light irradiation and heating to produce hydrogen.

[0072] In a specific embodiment of the present invention, the molar ratio of methanol to water is 1:(1-3); the alkali source includes potassium hydroxide and / or sodium hydroxide; the amount of alkali source is 1-5% of the mass of the mixed solution; the heating temperature is 120-210°C; and the illumination is provided by a 300W xenon lamp.

[0073] Unless otherwise specified, the room temperature in this invention refers to 25±2℃.

[0074] All raw materials used in the embodiments of this invention were purchased commercially. 2,2'-bipyridine-5,5'-dicarboxylic acid was purchased from Guangzhou Rongman Biotechnology Co., Ltd. (brand: Aladdin); anhydrous copper acetate was purchased from Guangzhou Rongman Biotechnology Co., Ltd. (brand: Macklin).

[0075] Example 1

[0076] A method for preparing a MOF-derived Cu / t-ZrO2 bimetallic heterojunction catalyst:

[0077] (1) Weigh 93 mg of copper tetraacetonitrile hexafluorophosphate and 100 mg of 1,2-bis(diphenylphosphine) ethane into a 100 mL dry three-necked flask, add a stir bar and 10 mL of anhydrous dichloromethane, dissolve, and then use a double-row tube device to perform a freeze-evacuation-thawing operation to remove oxygen from the flask and continuously and stably input nitrogen gas, so that it is stirred at room temperature and in an inert atmosphere (speed is 400 rpm, time is 70 min) to obtain mixed solution A;

[0078] Add 122 mg of 2,2'-bipyridine 5,5'-dicarboxylic acid, 20 mL of anhydrous dichloromethane and anhydrous N,N-dimethylformamide (volume ratio of anhydrous dichloromethane to N,N-dimethylformamide is 9:1) to a dry 50 mL soft-stoppered bottle. After sonication to dissolve evenly, deoxygenation is performed using a double-row tube device to obtain mixed solution B.

[0079] Subsequently, mixed solution B was added dropwise to a three-necked flask containing mixed solution A using a syringe. The solution color was observed to gradually change from colorless to reddish-brown. The reaction was maintained at room temperature under a nitrogen atmosphere and stirred (at a speed of 400 rpm for 6 hours). After the reaction was completed, the liquid was concentrated to 1.5 mL under reduced pressure using a rotary evaporator. A large amount of diethyl ether was added for recrystallization. The solid product was obtained by filtration and freeze-dried overnight. Finally, it was collected, sealed, and stored to obtain the copper-doped organic ligand material, denoted as D-Cu or [Cu(H2bpydc)(dppe)]PF6.

[0080] This step is carried out under anhydrous and oxygen-free conditions.

[0081] (2) Weigh 100 mg of the copper-doped organic ligand material prepared in step (1) into a dry pressure-resistant bottle, add 6 mL of DMF and sonicate for 15 min. After no obvious particle precipitation, add 2 mL of DMF solution containing 50 mg ZrCl4. Mix the two evenly by sonication and place them in an oven for hydrothermal reaction at 120 °C for 48 h. After the reaction is completed, cool the pressure-resistant bottle to room temperature and wash it three times with DMF and ethanol until the supernatant is clear and transparent (centrifugation speed is 10000 rpm). After centrifugation, place it in a vacuum drying oven at 60 °C for 12 h and grind the obtained solid into powder to obtain the copper-doped zirconium-based metal-organic framework material, denoted as D-Cu / Zr-MOF.

[0082] (3) The copper-doped zirconium-based metal-organic framework material prepared in step (2) was placed in a muffle furnace and heated to 450°C at a heating rate of 2°C / min. After calcination, when the temperature dropped to about 150°C, it was transferred to a tube furnace and heated to 300°C at a heating rate of 2°C / min under a nitrogen atmosphere with a flow rate of 50 mL / min. After heat treatment for 2 hours, the MOF-derived Cu / t-ZrO2 bimetallic heterojunction catalyst was obtained, denoted as MD-Cu / t-ZrO2.

[0083] Example 2

[0084] Same as Example 1, except that the copper source used in step (1) is copper acetate monohydrate, and the amount is 45.4 mg.

[0085] A MOF-derived Cu / t-ZrO2 bimetallic heterojunction catalyst was prepared, denoted as MD-Cu1 / t-ZrO2.

[0086] Example 3

[0087] Same as Example 1, except that the copper source used in step (1) is copper chloride dihydrate, and the amount used is 42.6 mg.

[0088] A MOF-derived Cu / t-ZrO2 bimetallic heterojunction catalyst was prepared, denoted as MD-Cu2 / t-ZrO2.

[0089] Comparative Example 1

[0090] A method for preparing copper-doped organic ligand-derived materials:

[0091] The copper-doped organic ligand material (denoted as D-Cu) prepared in Example 1 was placed in a muffle furnace and heated to 450°C at a heating rate of 2°C / min. After calcination, when the temperature dropped to about 150°C, it was transferred to a tube furnace and heated to 300°C at a heating rate of 2°C / min under a nitrogen atmosphere with a flow rate of 50 mL / min. After heat treatment for 2 hours, the copper-doped organic ligand derivative material, denoted as Cu / Cu2O, was obtained.

[0092] Comparative Example 2

[0093] A method for preparing a zirconium-based metal-organic framework material:

[0094] Weigh 52.3 mg of 2,2'-bipyridine-5,5'-dicarboxylic acid into a dry, pressure-resistant bottle. Add 6 mL of DMF and sonicate for 15 min until no obvious particle precipitate is found. Then add 2 mL of DMF solution containing 50 mg ZrCl4. Mix the two solutions evenly by sonication and place them in an oven for hydrothermal reaction at 120 °C for 48 h. After the reaction is complete, cool the pressure-resistant bottle to room temperature and wash it three times with DMF and ethanol until the supernatant is clear and transparent (centrifuge at 10000 rpm / min). After centrifugation, place it in a vacuum drying oven at 60 °C for 12 h and dry it. Crush the obtained solid into powder to obtain a zirconium-based metal-organic framework material, denoted as Zr-MOF.

[0095] Comparative Example 3

[0096] A method for preparing a zirconium-based metal-organic framework material-derived support:

[0097] The zirconium-based metal-organic framework material (denoted as Zr-MOF) prepared in Comparative Example 2 was placed in a muffle furnace and heated to 450°C at a heating rate of 2°C / min. After calcination, when the temperature dropped to about 150°C, it was transferred to a tube furnace and heated to 300°C at a heating rate of 2°C / min under a nitrogen atmosphere with a flow rate of 50 mL / min. After heat treatment for 2 hours, the zirconium-based metal-organic framework material derivative support was obtained, denoted as MD-ZrO2.

[0098] Example 1

[0099] Transmission electron microscopy (TEM) was performed on the D-Cu / Zr-MOF prepared in step (2) of Example 1, the MD-Cu / t-ZrO2 prepared in step (3) of Example 1, and the Zr-MOF prepared in Comparative Example 2. The results are shown in the figure. Figure 1 , Figure 1 Figures (a) to (c) show the Zr-MOF prepared in Comparative Example 2, Figures (d) to (f) show the D-Cu / Zr-MOF prepared in step (2) of Example 1, and Figures (g) to (h) show the MD-Cu / t-ZrO2 prepared in step (3) of Example 1.

[0100] A bimetallic heterojunction catalyst, MD-Cu / t-ZrO2, was constructed by integrating pre-coordinated copper organic ligands with a zirconium source to form a MOF precursor, followed by two-step heat treatment (calcination in air + heat treatment in an inert atmosphere). The first step of the subsequent two heat treatments optimized the dispersion of the supported metal species, forming a heterojunction with the metal oxides derived from the secondary building blocks, thus improving conductivity and carrier separation efficiency. The second step stabilized the framework, inhibiting metal particle growth at low heating rates, thereby enhancing photocatalytic activity.

[0101] from Figure 1As can be seen from Figures (g) to (h), the MD-Cu / t-ZrO2 framework prepared in Example 1 has obvious metal loading, indicating the successful synthesis of the catalyst MD-Cu / t-ZrO2.

[0102] The high-magnification transmission electron microscope image of MD-Cu / t-ZrO2 prepared in step (3) of Example 1 is shown below. Figure 2 Figures (a) and (b).

[0103] from Figure 2 Lattice fringes with lengths of 0.214 nm, 0.246 nm, and 0.297 nm can be observed, corresponding to the 111 crystal plane of Cu, the 111 crystal plane of Cu₂O, and the 101 crystal plane of tetragonal t-ZrO₂, respectively. This demonstrates the stability of the bimetallic MOF framework structure and the successful introduction of the copper active component. Furthermore, a tight interfacial contact is observed between the copper component and the zirconium support, which facilitates charge transfer.

[0104] Example 2

[0105] The XRD patterns of D-Cu / Zr-MOF prepared in step (2) of Example 1, MD-Cu / t-ZrO2 prepared in step (3) of Example 1, and Zr-MOF prepared in Comparative Example 2 are shown below. Figure 3 .

[0106] from Figure 3 As can be seen, the ligand-metal functionalized MOF material (D-Cu / Zr-MOF) exhibits characteristic peaks of Zr-MOF in the low diffraction angle range, and characteristic peaks of tetragonal t-ZrO2 appear after two-step heat treatment, proving that the material successfully avoids structural collapse caused by phase transition, indicating the stability of the structure, which is consistent with the above electron microscopy results. Furthermore, the X-ray diffraction results of MD-Cu1 / t-ZrO2 and MD-Cu2 / t-ZrO2 prepared using different copper sources in Examples 2 and 3 are basically consistent with those in Example 1.

[0107] Example 3

[0108] To verify the long-term stability of the catalyst, the MD-Cu / t-ZrO2 and the physically mixed Cu / Cu2O+MD-ZrO2 prepared in Example 1 were subjected to an 80-hour continuous stability test using gas chromatography. The specific steps are as follows:

[0109] (1) Preparation of Cu / Cu2O+MD-ZrO2: Cu / Cu2O prepared in Comparative Example 1 and MD-ZrO2 prepared in Comparative Example 3 were mixed at a mass ratio of 1:1 to obtain Cu / Cu2O+MD-ZrO2.

[0110] (2) Weigh out 5 mg or more of the catalyst material (MD-Cu / t-ZrO2, or Cu / Cu2O+MD-ZrO2), add 10 mL of alkaline methanol aqueous solution (methanol to water molar ratio of 1:1, potassium hydroxide as the alkaline source, concentration of 5 wt%), and mix thoroughly to obtain a mixed solution; place the mixed solution into a photothermal reactor and purge with 2 MPa nitrogen gas for deoxygenation. Before the reaction, place the photothermal reactor in water to test its airtightness. Subsequently, heat the reactor to 210 °C at a heating rate of 5 °C / min, and set the stirring speed to 500 rpm / min during the reaction. Use a 300W xenon lamp (CELPF300-T8) as the light source to carry out the photothermal catalytic reaction. Analyze the content of hydrogen and other byproducts in the product collected by the gas bag using a gas chromatograph. The results are shown in […]. Figure 4 .

[0111] from Figure 4 As can be seen from the data, the hydrogen yield of MD-Cu / t-ZrO2 prepared in Example 1 was 837.462 mmol / g from the initial 2.5 h. cat / h, the hydrogen yield was 5593.626 mmol / g 80h from the initial value. cat / h, which is 6.7 times that of the initial 2.5h, while the hydrogen yield of the physical mixture Cu / Cu2O+MD-ZrO2 is 275.176 mmol / g compared to the initial 2.5h. cat / h, the hydrogen yield was 677.137 mmol / g 80h from the initial value. cat The hydrogen production rate of MD-Cu / t-ZrO2 was 2.4 times that of the initial 2.5h, indicating that the hydrogen production rate of MD-Cu / t-ZrO2 and the physically mixed group Cu / Cu2O+MD-ZrO2 did not decline during the 80-hour continuous stability test. Furthermore, the hydrogen production rate of MD-Cu / t-ZrO2 was 8.2 times that of the physically mixed group Cu / Cu2O+MD-ZrO2 after 80h. These results demonstrate that the MD-Cu / t-ZrO2 catalyst prepared in this invention has excellent photocatalytic hydrogen production stability.

[0112] Example of effect 4

[0113] The alkaline conditions for the photothermal catalytic methanol reforming hydrogen production experiment of the MD-Cu / t-ZrO2 catalyst prepared in Example 1 were modified as follows: 5 mg of the MD-Cu / t-ZrO2 catalyst prepared in Example 1 was added to 10 mL of alkaline-free methanol aqueous solution (methanol to water molar ratio of 1:1), and the remaining reaction conditions were kept consistent with those of Example 3 (temperature 120–210 °C, 300 W xenon lamp irradiation, reaction time 80 min). After the reaction, the hydrogen production was analyzed by gas chromatography, and the results are shown in [Figure 1]. Figure 5 .

[0114] from Figure 5As can be seen from the data, the MD-Cu / t-ZrO2 catalyst prepared in Example 1 has a hydrogen yield of 32.67 mmol / g under alkali-free conditions at 210℃. cat / h.

[0115] Example 5

[0116] The following hydrogen production experiments were conducted: photothermal catalytic methanol reforming for hydrogen production (PC-TC) and pure thermal catalytic methanol reforming for hydrogen production (TC) on the following samples: MD-Cu / t-ZrO2 prepared in Example 1, MD-Cu1 / t-ZrO2 prepared in Example 2, MD-Cu2 / t-ZrO2 prepared in Example 3, Cu / Cu2O+MD-ZrO2 prepared in Comparative Example 1, Zr-MOF prepared in Comparative Example 2, MD-ZrO2 prepared in Comparative Example 3, the physical mixture Cu / Cu2O+MD-ZrO2, and D-Cu / Zr-MOF prepared in Example 1. All reactions were carried out in a 50 mL SG50-Y2W5-316L-CY high-pressure reactor, which is equipped with an automatic temperature and pressure control system, magnetic stirring function, and a sapphire transparent window. The specific steps are as follows:

[0117] (1) The preparation method of physical mixture Cu / Cu2O+MD-ZrO2 is as follows: Cu / Cu2O prepared in Comparative Example 1 and MD-ZrO2 prepared in Comparative Example 3 are mixed at a mass ratio of 1:1 to obtain Cu / Cu2O+MD-ZrO2.

[0118] (2) Weigh out 5 mg or more of the catalyst material and add 10 mL of alkaline methanol aqueous solution (methanol to water molar ratio of 1:1, potassium hydroxide source with a concentration of 5 wt%). Mix well to obtain a mixed solution. Place the mixed solution into a photothermal reactor and purge with 2 MPa nitrogen for deoxygenation. Before the reaction, place the photothermal reactor in water to test its sealing. Then, heat the reactor to 210 °C at a heating rate of 5 °C / min and react for 80 min. The stirring speed during the reaction is set to 500 rpm / min. A 300W xenon lamp (CELPF300-T8) is used as the light source for the photothermal catalytic reaction. For pure thermal catalytic reactions, no light source is required, but other conditions remain the same. After the reaction, cool the reactor and analyze the hydrogen and other byproduct content in the product collected by the gas bag using gas chromatography. The results are shown in [Figure 1]. Figure 6 .

[0119] from Figure 6 As can be seen from this, compared to Cu / Cu2O+MD-ZrO2 (301.36mmol / g) cat / h), Cu / Cu2O (209mmol / g) cat / h), MD-ZrO2 (184.92mmol / g) cat / h), D-Cu / Zr-MOF (86.24mmol / g)cat / h) and Zr-MOF (36.06mmol / g) cat The hydrogen production performance of MD-Cu / t-ZrO2 was improved by 2.9 to 24.3 times. Among the MD-Cux / t-ZrO2 (MD-Cu / t-ZrO2, MD-Cu1 / t-ZrO2 and MD-Cu2 / t-ZrO2) prepared by similar methods, the one using copper tetraacetonitrile hexafluorophosphate showed the highest performance, reaching 877.8 mmol / g. cat / h, which is a purely thermal catalytic method (32.67mmol / g) cat It exhibits 27 times the hydrogen production activity (448.06 μmol / g) even at a low temperature of 70°C. cat ( / h). Furthermore, tests revealed that the photothermal catalytic performance of all catalyst materials was higher than that of pure thermal catalysis, indicating that the photothermal effect can improve reaction performance.

[0120] The catalytic performance of the MD-Cux / t-ZrO2 catalyst is significantly higher than that of the single-component Cu / Cu2O+MD-ZrO2, with an improvement of approximately three times. This is attributed to the heterojunction structure formed within the catalyst, which enhances the separation efficiency of photogenerated carriers. Furthermore, the presence of Cu at the interface... 0 / +1 -Zr also provides sites for the activation and adsorption of reactants. The reaction system utilizes photothermal synergy, with thermally assisted photocatalysis accelerating the separation of photoexcited carriers. The photocatalytic reaction is promoted with increasing temperature within a certain temperature range. Simultaneously, photo-assisted thermal catalysis injects high-energy photons excited by the photocatalyst into the pure thermal catalysis, accelerating the conversion of adsorbed species on the catalyst surface. This allows for more efficient hydrogen production in the methanol liquid-phase reforming process. The performance results demonstrate that the MOF-derived Cu / t-ZrO2 bimetallic heterojunction catalyst is beneficial for the photothermal synergistic catalytic methanol liquid-phase reforming hydrogen production reaction system.

[0121] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a MOF-derived Cu / t-ZrO2 bimetallic heterojunction catalyst, characterized in that, Includes the following steps: (1) Add copper source and 1,2-bis(diphenylphosphine) ethane to a dry three-necked flask, then add anhydrous dichloromethane, and use a double-row tube device to perform freezing-vacuuming-thawing operations to remove oxygen from the flask and continuously and stably input nitrogen gas, so that it is stirred at room temperature and inert atmosphere at a speed of 300~500 rpm for 60~90 min to obtain mixed solution A; The organic ligand was added to a mixed solution of anhydrous dichloromethane and anhydrous N,N-dimethylformamide. After being dissolved uniformly by ultrasonication, the solution was deoxygenated using a double-row tube device to obtain mixed solution B. Mixed solution B was added dropwise to mixed solution A. The solution color was observed to gradually change from colorless to reddish-brown. The mixture was stirred at room temperature and under a nitrogen atmosphere at a speed of 300-500 rpm for 5-7 hours. After the reaction was completed, the mixture was concentrated to 1-2 mL under reduced pressure. A large amount of diethyl ether was added for recrystallization. The solid product was obtained by filtration and freeze-drying. Finally, the product was collected, sealed and stored to obtain the copper-doped organic ligand material. This step is carried out under anhydrous and oxygen-free conditions; (2) The copper-doped organic ligand material and the zirconium source were ultrasonically mixed with N,N-dimethylformamide and then hydrothermally reacted. After centrifugation, washing, drying, and pulverizing, copper-doped zirconium-based metal-organic framework material was obtained. (3) The copper-doped zirconium-based metal-organic framework material was calcined in air and then heat-treated in an inert atmosphere to obtain a MOF-derived Cu / t-ZrO2 bimetallic heterojunction catalyst. The mass ratio of the copper-doped organic ligand material to the zirconium source is (1.8~2):1; The organic ligand is 2,2'-bipyridine-5,5'-dicarboxylic acid.

2. The preparation method according to claim 1, characterized in that, The copper source includes copper tetraacetonitrile hexafluorophosphate, copper acetate monohydrate, or copper chloride dihydrate.

3. The preparation method according to claim 1, characterized in that, The mass ratio of copper to 1,2-bis(diphenylphosphine)ethane in the copper source is (0.07~0.16):1; And / or, the mass ratio of the organic ligand to copper in the copper source is 1:(0.05~0.15).

4. The preparation method according to claim 1, characterized in that, The zirconium source includes zirconium tetrachloride or zirconium oxychloride.

5. The preparation method according to claim 1, characterized in that, The hydrothermal reaction is carried out at a temperature of 100-120°C for a duration of 36-72 hours.

6. The preparation method according to claim 1, characterized in that, The calcination process involves a heating rate of 2-5°C / min, a temperature of 400-500°C, and a holding time of 1.5-3 hours. And / or, the heating rate of the heat treatment is 2~5℃ / min, the temperature is 250~350℃, and the holding time is 1.5~3h.

7. A MOF-derived Cu / t-ZrO2 bimetallic heterojunction catalyst prepared by the preparation method according to any one of claims 1 to 6.

8. The application of the MOF-derived Cu / t-ZrO2 bimetallic heterojunction catalyst of claim 7 in photothermal catalytic methanol reforming for hydrogen production.

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