Interface regulation method based on metal nanoparticle / mof composite and application thereof

Abstract

The application discloses an interface regulation method based on a metal nanoparticle / MOF composite material and application thereof, wherein a reducing agent and a defect modulator are added in the process of synthesizing the metal nanoparticle / MOF composite material by an electrochemical method, the formation speed of MOFs and the reduction speed of a metal precursor are controlled by rationally regulating voltage, reaction temperature and time in the reaction process, and thus the metal nanoparticle / MOF composite material with different interface microenvironments is obtained. The metal nanoparticle / MOF composite material can be applied to a photocatalysis field as a photocatalyst, and a clean two-phase interface environment is favorable for separation and transfer of photo-generated charges, so that efficient utilization of photo-generated electrons and holes is realized, and finally excellent photocatalytic performance is obtained.

Description

Technical Field

[0001] This invention belongs to the field of advanced nanocomposite materials technology, specifically relating to an interface control method based on metal nanoparticle / MOF composite materials and its application. Background Technology

[0002] The depletion of fossil fuel reserves has led to the current global energy crisis and environmental problems. Solar energy, however, is an inexhaustible and clean energy source, making the development of solar energy conversion technologies crucial for solving the energy crisis. Photocatalysis is a widely studied solar energy utilization technology. Generally, semiconductor materials absorb sunlight and are excited, generating photoelectrons and holes, thus undergoing redox reactions. However, single-component semiconductor materials are prone to bulk recombination of photoelectrons and holes, resulting in poor utilization of photogenerated charges and low photo-chemical energy conversion efficiency. Metal nanoparticles, especially platinum (Pt) nanoparticles, are considered excellent electron acceptors. Therefore, in research in this field, synthesizing metal nanoparticle / semiconductor composite photocatalysts is considered one of the reliable methods to improve the separation and transfer efficiency of photogenerated charges in semiconductor materials. Furthermore, micro-environmental control of the interface between metal nanoparticles and semiconductor materials is a key solution to achieve efficient charge separation and transfer, thereby obtaining high-efficiency photocatalytic performance.

[0003] Metal-organic frameworks (MOFs) are a novel class of crystalline porous solid materials composed of metal ions or metal clusters bridged with organic ligands. Due to their defect-free or defect-poor crystalline ordered structure and porous nature, MOFs possess unique advantages in the efficient separation of electrons and holes. The rational design and synthesis of MOFs and their composites for photocatalysis has shown great promise. Using this as a starting point, designing and synthesizing metal nanoparticle / MOF composites with different interfacial environments is of great significance for understanding interface engineering and the structure-activity relationship of photocatalytic reactions.

[0004] To control the size and morphology of metal nanoparticles, researchers typically modify metal surfaces using surfactants (such as polyvinylpyrrolidone). However, the use of surfactants can cover active metal sites, hindering the transfer of photogenerated charges at the interface. Therefore, this invention proposes an electrolytic method to synthesize MOFs without the use of surfactants, and to rationally synthesize metal nanoparticle / MOF composites by in-situ reduction of the target metal nanoparticle precursor using a reducing solvent. This allows for the application of these composites in efficient photocatalysis. During the electrolysis process, a unique interface control method for metal nanoparticle / MOF composites is achieved through rational regulation of the reducing agent and defect modulator, applied voltage, reaction temperature, and time. Summary of the Invention

[0005] This invention addresses the problems existing in the prior art by providing a method for interface control based on metal nanoparticle / MOF composite materials and its application. The technical problem to be solved is to achieve interface control of metal nanoparticle / MOF composite materials by adding reducing agents and defect modulators during the electrochemical synthesis of metal nanoparticle / MOF composite materials, and by rationally controlling the applied voltage, reaction temperature, and time.

[0006] The technical solution of this invention is as follows:

[0007] This invention relates to an interface control method for metal nanoparticle / MOF composite materials. During the electrochemical synthesis of metal nanoparticle / MOF composite materials, a reducing agent and a defect modulator are added. By rationally controlling the applied voltage, reaction temperature, and time during the reaction, the formation rate of MOFs and the reduction rate of the metal precursor are controlled, thereby obtaining metal nanoparticle / MOF composite materials with different interfacial microenvironments. Specifically, the method includes the following steps:

[0008] (1) Using N,N-dimethylformamide as solvent, prepare organic ligand stock solutions and metal precursor stock solutions of specific concentrations respectively; take 25 mL of organic ligand stock solution, 0.9 mL of metal precursor stock solution, 1 mL of concentrated hydrochloric acid (36-38%), and x mL of defect modifier solution, mix them to form an electrolyte, and stir to make it fully mixed;

[0009] (2) Take two metal plates of the same size and place them at both ends of the electrolyte as the anode and cathode. Adjust the reaction temperature and stir the electrolyte. Apply voltage under DC power to carry out electrolytic synthesis.

[0010] (3) After electrolysis for a period of time, cathode products appear. The product precipitate is collected by centrifugation at 10,000 rpm for 5 min. The precipitate is washed three times with methanol and dried under vacuum in the temperature range of 40-60℃. Finally, metal nanoparticle / MOF composite materials with different interfacial microenvironments are obtained.

[0011] As a preferred embodiment of the present invention: the organic ligand is 2-aminoterephthalic acid, and the concentration of the organic ligand mother liquor is 0.025 mol / L-0.1 mol / L; the metal precursor is chloroplatinic acid hexahydrate, and the concentration of the metal precursor mother liquor is 10 mg / mL-25 mg / mL.

[0012] As a preferred embodiment of the present invention, the defect modifier is acetic acid. The value of x mL of the defect modifier is determined by the molar ratio of the organic ligand to the defect modifier, typically 1:50, 1:100, 1:150, or 1:200.

[0013] As a preferred technical solution of the present invention: the metal sheet is a zirconium sheet, 1 cm wide, 6 cm long and 0.5 mm thick, and the length inserted into the solution is 1-2 cm. After the anode metal sheet is oxidized, it coordinates with the organic ligand to form MOFs material.

[0014] As a preferred technical solution of the present invention: the applied voltage during the electrolysis reaction is 0-16V, the reaction temperature is 80-120℃, and the reaction time is 1-6 hours.

[0015] As a preferred embodiment of the present invention, the reducing agent is a reducing solvent, specifically N,N-dimethylformamide.

[0016] In the metal nanoparticle / MOF composite material obtained by the present invention: the metal nanoparticles are preferably platinum (Pt); the MOFs are preferably zirconium-based MOFs UiO-66-NH2.

[0017] The present invention relates to the method described above, wherein the metal nanoparticles are not limited to platinum (Pt), palladium (Pd), gold (Au), and nickel (Ni), but also include other metal nanoparticles that can be reduced by solvent or by electrochemical reduction.

[0018] This invention relates to the method described above, wherein the MOFs are not limited to zirconium-based MOFs UiO-66, UiO-66-NH2, titanium-based MOFs MIL-125, MIL-125-NH2, copper-based MOFs HKUST-1, iron-based MOFs MIL-100(Fe), MIL-101(Fe), and chromium-based MOFs MIL-101(Cr); it also includes other types of metal-organic framework materials obtained by coordination polymerization of zirconium, titanium, copper, iron, chromium and other various carboxylate organic ligands.

[0019] The application of the metal nanoparticle / MOF composite material prepared by the above method is to use the metal nanoparticle / MOF composite material as a photocatalyst in the field of photocatalysis, including photocatalytic water splitting to produce hydrogen.

[0020] The beneficial effects of this invention are reflected in:

[0021] 1. The electrochemical synthesis and interface control method for metal nanoparticle / MOF composite materials provided by this invention is simple to operate, fast to react, and has high yield.

[0022] 2. This method can achieve temperature loading of metal nanoparticles without the use of surfactants, resulting in a "close" interface between metal nanoparticles and MOFs. This facilitates the efficient transfer and separation of photogenerated charges between the two phases, thereby achieving high-efficiency photocatalytic performance.

[0023] 3. By rationally selecting reducing agents and defect modulators, and rationally controlling the amount of defect modulators added and the reaction temperature, the formation rate of MOFs and the reduction rate of metal precursors can be controlled, thereby obtaining a series of metal nanoparticle / MOF composite materials with different interfacial microenvironments. This is of great significance for understanding the structure-activity relationship between interface engineering and photocatalytic performance. Attached Figure Description

[0024] Figure 1 The images show the XRD patterns of the metal nanoparticle / MOF composite materials prepared in Examples 1-4.

[0025] Figure 2 This is a standard TEM image of the metal nanoparticle / MOF composite material prepared in Example 3.

[0026] Figure 3 The graph shows a comparison of the hydrogen evolution rates of the metal nanoparticle / MOF composite materials prepared in Examples 1-6. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The present invention will be further described below with reference to the accompanying drawings and the following embodiments. It should be understood that the following embodiments are only used to illustrate the present invention and are not intended to limit the present invention.

[0028] Example 1:

[0029] Using N,N-dimethylformamide as a solvent, a 0.025 mol / L solution of 2-aminoterephthalic acid (NH2-BDC) and a 25 mg / mL solution of chloroplatinic acid hexahydrate were prepared. 25 mL of NH2-BDC solution, 0.9 mL of chloroplatinic acid hexahydrate solution, 1 mL of concentrated hydrochloric acid, and 2 mL of CH3COOH were mixed to form an electrolyte, and stirred until thoroughly mixed. Two identical zirconium plates were placed at both ends of the electrolyte as the anode and cathode. Electrolysis was performed at 100°C with stirring, using a DC power supply at 8V. After 4 hours, the cathode product was collected, centrifuged at 10000 rpm for 5 minutes to collect the precipitate. The precipitate was washed three times with methanol and dried under vacuum at 60°C to obtain the material, denoted as Pt / UiO-66-NH2 (1:50, 100°C).

[0030] Example 2:

[0031] Using N,N-dimethylformamide as solvent, prepare a 0.025 mol / L NH2-BDC solution and a 25 mg / mL chloroplatinic acid hexahydrate solution. Take 25 mL of NH2-BDC solution, 0.9 mL of chloroplatinic acid hexahydrate solution, 1 mL of concentrated hydrochloric acid, and 4 mL of CH3COOH, mix them to form an electrolyte, and stir to ensure thorough mixing. Place two identical zirconium plates at both ends of the electrolyte as the anode and cathode. Electrolytic synthesis is carried out at 100℃ with stirring, using a DC power supply at 8V. After 4 hours, collect the cathode product, centrifuge at 10000 rpm for 5 min to collect the product precipitate, wash the precipitate three times with methanol, and vacuum dry at 60℃ to obtain the material denoted as Pt / UiO-66-NH2 (1:100, 100℃).

[0032] Example 3:

[0033] Using N,N-dimethylformamide as solvent, prepare a 0.025 mol / L NH2-BDC solution and a 25 mg / mL chloroplatinic acid hexahydrate solution. Take 25 mL of NH2-BDC solution, 0.9 mL of chloroplatinic acid hexahydrate solution, 1 mL of concentrated hydrochloric acid, and 6 mL of CH3COOH, mix them to form an electrolyte, and stir to ensure thorough mixing. Place two identical zirconium plates at both ends of the electrolyte as the anode and cathode. Electrolytic synthesis is carried out at 100 °C with stirring of the electrolyte and a DC power supply at 8 V. After 4 h, collect the cathode product, centrifuge at 10000 rpm for 5 min to collect the product precipitate, wash the precipitate three times with methanol, and vacuum dry at 60 °C to obtain the material denoted as Pt / UiO-66-NH2 (1:150, 100 °C).

[0034] Example 4:

[0035] Using N,N-dimethylformamide as solvent, a 0.025 mol / L NH2-BDC solution and a 25 mg / mL chloroplatinic acid hexahydrate solution were prepared. 25 mL of NH2-BDC solution, 0.9 mL of chloroplatinic acid hexahydrate solution, 1 mL of concentrated hydrochloric acid, and 8 mL of CH3COOH were mixed to form an electrolyte, and stirred until fully homogeneous. Two identical zirconium plates were placed at both ends of the electrolyte as the anode and cathode. Electrolysis was performed at 100°C with stirring of the electrolyte, using a DC power supply at 8V. After 4 hours, the cathode product was collected, and the precipitate was collected by centrifugation at 10000 rpm for 5 minutes. The precipitate was washed three times with methanol and dried under vacuum at 60°C to obtain the material, denoted as Pt / UiO-66-NH2 (1:200, 100°C).

[0036] The XRD patterns of the metal nanoparticle / MOF composite materials prepared in Examples 1-4 are as follows: Figure 1 As shown. From Figure 1It can be seen that the diffraction peaks of these four photocatalysts all have the same characteristic peaks, which are consistent with the standard UiO-66-NH2 peak type, indicating that they were successfully synthesized and have good crystallinity.

[0037] A standard TEM image of the metal nanoparticle / MOF composite material prepared in Example 3 is shown below. Figure 2 As shown. From Figure 2 It can be seen that the material has a regular morphology and a large number of metal nanoparticles were reduced in situ. The distribution of metal nanoparticles on MOF can be clearly seen.

[0038] Example 5:

[0039] Using N,N-dimethylformamide as a solvent, a 0.025 mol / L NH2-BDC solution and a 25 mg / mL chloroplatinic acid hexahydrate solution were prepared. 25 mL of NH2-BDC solution, 0.9 mL of chloroplatinic acid hexahydrate solution, 1 mL of concentrated hydrochloric acid, and 6 mL of CH3COOH were mixed to form an electrolyte, and stirred until fully homogeneous. Two identical zirconium plates were placed at both ends of the electrolyte as the anode and cathode. Electrolysis was performed at 80 °C with stirring, using a DC power supply at 8 V. After 4 hours, the cathode product was collected, centrifuged at 10,000 rpm for 5 minutes to collect the precipitate. The precipitate was washed three times with methanol and dried under vacuum at 60 °C to obtain the material, denoted as Pt / UiO-66-NH2 (1:150, 80 °C).

[0040] Example 6:

[0041] Using N,N-dimethylformamide as solvent, a 0.025 mol / L NH2-BDC solution and a 25 mg / mL chloroplatinic acid hexahydrate solution were prepared. 25 mL of NH2-BDC solution, 0.9 mL of chloroplatinic acid hexahydrate solution, 1 mL of concentrated hydrochloric acid, and 6 mL of CH3COOH were mixed to form an electrolyte, and stirred until fully homogeneous. Two identical zirconium plates were placed at both ends of the electrolyte as the anode and cathode. Electrolysis was performed at 120 °C with stirring, using a DC power supply at 8 V. After 4 h, the cathode product was collected, centrifuged at 10000 rpm for 5 min to collect the precipitate. The precipitate was washed three times with methanol and dried under vacuum at 60 °C to obtain the material, denoted as Pt / UiO-66-NH2 (1:150, 120 °C).

[0042] This invention can be applied to fields such as photocatalytic water splitting for hydrogen production, photocatalytic carbon dioxide reduction, and photocatalytic organic matter conversion. The following description will focus on the study of photocatalytic water splitting for hydrogen production.

[0043] Example 7: Performance Test of Photocatalytic Water Splitting for Hydrogen Production

[0044] In a quartz reactor, 10 mg of the photocatalyst prepared in Examples 1-6, 27 mL of acetonitrile, 0.5 mL of deionized water, and 2.5 mL of LTEA were added as sacrificial agents. The quartz reactor was then capped and bubbled with nitrogen gas for deoxygenation for 30 min; then, circulating condensate was connected. A xenon lamp light source was placed 2 cm above the quartz reactor, and the light source was turned on. After 2 h, a sample was taken and injected into a gas chromatograph to detect the amount of hydrogen.

[0045] The hydrogen production rates of the metal nanoparticle / MOF composite materials prepared in Examples 1-6 are as follows: Figure 3 As shown. From Figure 3 Figure a shows that the amount of defect modulator affects the photocatalytic hydrogen production activity; from Figure 3 As shown in Figure b, temperature also affects the photocatalytic hydrogen production activity.

[0046] Table 1. Photocatalytic hydrogen production rates of composite materials in Examples 1-6

[0047] Example 1 <![CDATA[Pt / UiO-66-NH2(1∶50,100℃)]]> 1187 Example 2 <![CDATA[Pt / UiO-66-NH2(1∶100,100℃)]]> 1063 Example 3 <![CDATA[Pt / UiO-66-NH2(1∶150,100℃)]]> 1654 Example 4 <![CDATA[Pt / UiO-66-NH2(1∶200,100℃)]]> 1620 Example 5 <![CDATA[Pt / UiO-66-NH2(1:150,80℃)]]> 451 Example 6 <![CDATA[Pt / UiO-66-NH2(1∶150,120℃)]]> 819

[0048] Referring to Table 1, among the metal nanoparticle / MOF composite materials prepared in Examples 1-6, Example 3 exhibited a very high hydrogen production rate of 1654 μmol / (g·h). Adjusting the defect modulator / temperature affects the reduction rate of the metal precursor, resulting in metal nanoparticle / MOF composite materials with different interfacial microenvironments, thus producing different photocatalytic properties. Comparison revealed that the metal nanoparticle / MOF composite material obtained under interfacial regulation at 100℃ and an organic ligand / defect modulator motility ratio of 1:150 is more conducive to the separation and transfer of photogenerated charges, thus achieving excellent photocatalytic performance.

[0049] This invention discloses a method and application for controlling the microenvironment of the two-phase interface based on metal nanoparticles / MOF composite materials. The interface control method is simple to operate and easy to control, and the resulting composite material yield is high. The metal nanoparticles / MOF composite materials with different interface microenvironments are applied to photocatalysis. The clean two-phase interface environment enables efficient charge separation and transfer, resulting in high-efficiency photocatalytic performance.

[0050] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for interface control based on metal nanoparticle / MOF composite materials, characterized in that: In the process of electrochemical synthesis of metal nanoparticle / MOF composites, reducing agents and defect modulators are added. By rationally controlling the voltage, reaction temperature and time applied during the reaction process, the formation rate of MOFs and the reduction rate of metal precursors are controlled, thereby obtaining metal nanoparticle / MOF composites with different interfacial microenvironments. Specifically, the following steps are included: (1) Using N,N-dimethylformamide as solvent, prepare organic ligand stock solution and metal precursor stock solution of specific concentrations respectively; take 25 mL organic ligand stock solution, 0.9 mL metal precursor stock solution, 1 mL concentrated hydrochloric acid, and x mL defect modifier solution, mix them to form an electrolyte, and stir to make it fully mixed; (2) Take two metal plates of the same size and place them at both ends of the electrolyte as the anode and cathode. Adjust the reaction temperature and stir the electrolyte. Apply voltage under DC power to carry out electrolytic synthesis. (3) After electrolysis for a period of time, cathode products appear. The product precipitate is collected by centrifugation. The precipitate is washed with methanol and dried under vacuum in the temperature range of 40-60℃. Finally, metal nanoparticle / MOF composite materials with different interfacial microenvironments are obtained. The organic ligand is 2-aminoterephthalic acid, and the concentration of the organic ligand mother liquor is 0.025 mol / L-0.1 mol / L; The metal precursor is chloroplatinic acid hexahydrate, and the concentration of the metal precursor mother liquor is 10 mg / mL-25 mg / mL; The defect modulator is acetic acid; in the x mL defect modulator, the value of x is determined by the molar ratio of the organic ligand to the defect modulator, and the value is 1:50-200; The metal sheet is a zirconium sheet. After the anode metal sheet is oxidized, it coordinates with organic ligands to form MOF materials. In the metal nanoparticle / MOF composite material: the metal nanoparticles are platinum; the MOFs are zirconium-based MOFs UiO-66-NH2.

2. The interface control method according to claim 1, characterized in that: The applied voltage during the electrolysis reaction is 0-16 V, the reaction temperature is 80-120℃, and the reaction time is 1-6 hours.

3. The interface control method according to claim 1, characterized in that: The reducing agent is the reducing solvent N,N-dimethylformamide.

4. The application of the metal nanoparticle / MOF composite material prepared according to any one of claims 1-3, characterized in that: The aforementioned metal nanoparticle / MOF composite material is used as a photocatalyst in the field of photocatalysis.

5. The application according to claim 4, characterized in that: The metal nanoparticle / MOF composite material was used as a photocatalyst for photocatalytic water splitting to produce hydrogen.

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