CN110026241B - Three-dimensional polyacid-based nickel metal-organic crystalline catalytic material and preparation method thereof - Google Patents

Abstract

The purpose of the invention is to provide a low-cost and stable catalytic electrolysis water hydrogen evolution material, which contributes to solving the phenomenon that the electrolysis water hydrogen evolution catalyst is expensive. The present invention utilizes a one-step hydrothermal synthesis method to design a three-dimensional polyacid-based nickel metal-organic crystalline catalytic material whose molecular formula is H ₅ [PW ₁₂ O ₄₀ ] ₃ [Ni ₂ (OH) ₃ ] ₄ [C ₂ N ₄ H ₄ ^] _{12.12H 2} O, wherein C ₂ N ₄ H ₄ is 4-amino-4H-1,2,4-triazole. The crystal system is cubic, and the space group is

, the unit cell parameters are α=90, β=90, γ=90; a=25.3919(4)Å, b=25.3919(4)Å, c=25.3919(4)Å, Z =4. The preparation method is, dissolving phosphotungstic acid (H ₃ PO ₄ .12WO ₃ ^. x H ₂ O) ^, metal nickel salt and 4-amino-4H-1,2,4-triazole in deionized water, stirring, The pH was adjusted to 3.2-4.8 with NaOH solution and HCl solution, and then the reaction solution was placed in a polytetrafluoroethylene reactor, and placed in an oven with a temperature of 160° C. for 4 days. Back to room temperature. The invention can obtain a three-dimensional polyacid-based nickel metal-organic crystalline catalytic material.

Description

A kind of three-dimensional polyacid-based nickel metal-organic crystalline catalytic material and preparation method thereof

technical field

The invention relates to a three-dimensional polyacid-based nickel metal-organic crystalline catalytic material and a preparation method thereof.

Background technique

Polyacids, that is, polyoxometalates (POMs) are a class of inorganic polyoxometalate compounds, which are metal- Oxygen cluster compounds can be divided into homopolyacids and heteropolyacids (central heteroatoms include P, B, Al, Co, etc.) according to their elemental composition. It has a wide range of applications in the fields of adsorption, catalysis, biology, optoelectronics and other research fields.

After more than two centuries of development of polyacids, especially in the past ten years, the invention of various analytical methods and characterization methods has fully explored the basic research fields of polyacids. In the field of catalysis, the most successful developments are photocatalysis and electrocatalysis. However, as a catalyst, although polyacid has its unique redox performance, it also faces inevitable shortcomings: small specific surface area, non-recyclable and so on. Based on this situation, a polyacid-based nickel metal crystalline hydrogen evolution material with a three-dimensional structure was designed and synthesized in this experiment, which can not only improve the specific surface area of the polyacid catalyst; at the same time, the existence of the pore structure can promote and selectively make The reactant molecule is close to the active polyacid catalytic species; more importantly, the polyacid is monodispersed at the molecular level to realize the homogeneous catalytic reaction of the heterogeneous catalyst.

As early as many years ago, polyazole compounds were widely used as protective layers on metal surfaces due to their ability to form metal azole coordination polymers on metal surfaces. The nitrogen atoms of azoles all adopt sp ² hybridization mode, so that azole compounds can deprotonate to form corresponding azole anions under certain conditions. Since the nitrogen atom is an electron withdrawing group, the more nitrogen atoms contained on the azole, the stronger its acidity and the easier it is to deprotonate on the surface. Deprotonation can not only make all nitrogen atoms available for coordination, but also enhance the basicity of nitrogen atoms. The metal azole framework has very high thermal stability and chemical stability. At the same time, due to the small steric hindrance, many coordination points and flexible coordination modes of azoles, it is easy to form a variety of high-dimensional coordination structures.

In this experiment, a three-dimensional polyacid-based nickel metal-organic crystal was designed and synthesized using 4-amino-4H-1,2,4-triazole as the organic ligand and Keggin-type phosphotungstic acid as the center of metal nickel. catalytic material. Through a large number of literature research, it is not difficult to find that among the crystal materials with 4-amino-4H-1,2,4-triazole as the organic ligand, there are few materials that coordinate with metallic nickel. At the same time, the crystal The connection method of the materials is that the metal nickel and the oxygen atoms in the polyacid are alternately connected to each other to form an eight-membered ring structure, and the eight-membered ring structures are superimposed and interlaced with each other to form a three-dimensional three-dimensional structure, which is an organic and inorganic crystal material. Development has added a novel structure. On this basis, taking full advantage of the redox properties of polyacids, the electrocatalytic hydrolysis performance of the crystal material was studied. Electrocatalytic hydrolysis is to split water by electrical energy to generate H ₂ and O ₂ , which is an ideal hydrogen production. At present, the best electrocatalytic hydrolysis catalysts are Pt-based materials. However, the expensive price and less reserves of Pt-based materials greatly limit the industrial application. Therefore, the search for inexpensive and highly active non-precious metal catalysts is still an issue. huge challenge. In recent years, polyacids and their derived composites have shown promising development prospects as catalysts for electrolysis of water for hydrogen production.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a hydrogen evolution material with low cost and good stability, which contributes to solving the phenomenon that the hydrogen evolution catalyst is expensive.

晶胞参数为α＝90，β＝90，γ＝90；

Z＝4。A three-dimensional polyacid-based nickel metal-organic crystalline catalytic material, the molecular formula of which is H ₅ [PW ₁₂ O ₄₀ ] ₃ [Ni ₂ (OH) ₃ ] ₄ [C ₂ N ₄ H ₄ ] ₁₂ ·12H ₂ O, wherein C ₂ N ₄ H ₄ is 4-amino-4H-1,2,4-triazole, the crystal system is cubic, and the space group is

The unit cell parameters are α=90, β=90, γ=90;

Z=4.

A three-dimensional polyacid-based nickel metal-organic crystalline catalytic material and a preparation method thereof, wherein the preparation method is completed according to the following steps:

1. Preparation of a reaction solution with a pH value of 3.2-4.8: Dissolve phosphotungstic acid, metal nickel salt and 4-amino-4H-1,2,4-triazole in deionized water and stir for several hours at room temperature , to obtain a reaction solution; then use sodium hydroxide solution and hydrochloric acid solution to adjust the pH value of the reaction solution to 3.2-4.8 to obtain a reaction solution with a pH value of 3.0-4.8;

The mol ratio of the phosphotungstic acid described in the step 1 and the nickel chloride hexahydrate is 0.1: (0.4-0.9);

The molar ratio of the phosphotungstic acid described in the step 1 and the 4-amino-4H-1,2,4-triazole organic ligand is: 0.1:0.1;

The volume ratio of the amount of the phosphotungstic acid described in the step 1 and the distilled water is: 0.1 mmol: 10 mL;

2. Add the reaction solution with a pH value of 3.2-4.8 to the reaction kettle of polytetrafluoroethylene, react at a temperature of 160 ° C for 4 days, cool down to room temperature to obtain a green triangular pyramid-shaped crystal, which is a kind of three-dimensional polytetrafluoroethylene. Acid-Based Nickel Metal-Organic Crystalline Catalytic Materials.

晶胞参数为α＝90，β＝90，γ＝90；

Z＝4。The three-dimensional polyacid-based nickel metal-organic crystalline catalytic material described in the second step and a preparation method thereof. A three-dimensional polyacid-based nickel metal-organic crystalline catalytic material was designed and prepared, the molecular formula is H ₅ [PW ₁₂ O ₄₀ ] ₃ [Ni ₂ (OH) ₃ ] ₄ [C ₂ N ₄ H ₄ ] ₁₂ ·12H ₂ O. The crystal system is cubic, and the space group is

The unit cell parameters are α=90, β=90, γ=90;

Z=4.

Compared with the prior art, the present invention has the following characteristics:

The crystal material of the invention is synthesized from Keggin-type phosphotungstic acid, 4-amino-4H-1,2,4-triazole and metal nickel salt according to a certain molar ratio by one-step hydrothermal method, which is a novel A crystal material with a triangular structure, in which the two nitrogen atoms located on the 1st and 2nd of the organic ligand are coordinated with the metal nickel, and every three ligands are combined with two metal ions, each The No. 1 metal ion is coordinated with three polyacids in different directions, and the No. 2 metal ion is coordinated with the oxygen atoms in the water molecule. Each polyacid has four terminal oxygen atoms in different directions. Therefore, the crystal is not connected by one-dimensional or two-dimensional connection, but directly centered on polyacid, forming a three-dimensional network structure, which is a three-dimensional polyacid-based nickel metal-organic crystalline catalytic material At the same time, according to the redox performance of polyacid, the electrocatalytic hydrolysis performance of this crystal material was studied in 0.5MH ₂ SO ₄ solution at a scanning speed of 100mV/s. The results showed that the current density was 10mA·cm ^-2 The corresponding potential is 0.66V.

Description of drawings

1 is a schematic diagram of the asymmetric structure of a three-dimensional polyacid-based nickel metal-organic crystalline catalytic material prepared in Example 1. In FIG. 1, 1 is N, 2 is C, 3 is O, 4 is W, and 5 is Ni , 6 is P;

Fig. 2 is the coordination schematic diagram of the ligand and metal of a kind of three-dimensional polyacid-based nickel metal-organic crystalline catalytic material prepared in Example 1;

Fig. 3 is the metal nickel ion of different coordination situation of a kind of three-dimensional polyacid-based nickel metal-organic crystalline catalytic material prepared in Example 1 and the oxygen atom in the polyacid coordinated with the metal;

4 is a three-dimensional structure topology diagram of a three-dimensional polyacid-based nickel metal-organic crystalline catalytic material prepared in Example 1;

5 is an infrared spectrogram of a three-dimensional polyacid-based nickel metal-organic crystalline catalytic material prepared in Example 1;

6 is a PXRD pattern of a three-dimensional polyacid-based nickel metal-organic crystalline catalytic material prepared in Example 1;

7 is a cyclic voltammogram of a three-dimensional polyacid-based nickel metal-organic crystalline catalytic material prepared in Example 1;

8 is a linear scan voltammogram of a three-dimensional polyacid-based nickel metal-organic crystalline catalytic material prepared in Example 1;

9 is a schematic diagram of the synthesis structure of a three-dimensional polyacid-based nickel metal-organic crystalline catalytic material prepared in Example 1;

Detailed ways

The process parameters and process routes of the present invention are not limited to the specific embodiments listed below, and the specific embodiments listed below only illustrate the present invention and are not limited to the process parameters and process routes described in the embodiments of the present invention. It should be understood by researchers in the art that the present invention may be modified or equivalently replaced in practical applications to achieve the same technical effect. As long as the application requirements are met, they are all within the protection scope of the present invention.

晶胞参数为α＝90，β＝90，γ＝90；

Z＝4。Embodiment 1: This embodiment is a three-dimensional polyacid-based nickel metal-organic crystalline catalytic material, the molecular formula is H ₅ [PW ₁₂ O ₄₀ ] ₃ [Ni ₂ (OH) ₃ ] ₄ [C ₂ N ₄ H ₄ ] ₁₂ ·12H ₂ O. The crystal system is cubic, and the space group is

The unit cell parameters are α=90, β=90, γ=90;

Z=4.

In H ₅ [PW ₁₂ O ₄₀ ] ₃ [Ni ₂ (OH) ₃ ] ₄ [C ₂ N ₄ H ₄ ] ₁₂ 12H ₂ O described in this embodiment, the Ni valence is +2, and the coordination mode is 6 Coordination; Keggin-type polyacids participate in the coordination of metals with four terminal oxygen atoms in different directions, and each No. 1 metal nickel is connected with three polyacids and three ligands respectively, thereby forming a three-dimensional network structure.

Compared with the prior art, this embodiment has the following characteristics:

The crystal material of the present invention is synthesized from Keggin-type phosphotungstic acid, 4-amino-4H-1,2,4-triazole and metal nickel according to a certain molar ratio through a one-step hydrothermal method. The single crystal X-ray diffraction results It is shown that it is a crystalline material with a novel triangular structure, in which two nitrogen atoms located on No. 1 and No. 2 on organic ligands coordinate with metal nickel, and every three ligands are coordinated with two nitrogen atoms. Combined with metal ions, each No. 1 metal ion coordinates with three polyacids in different directions, and No. 2 metal ions coordinate with oxygen atoms in water molecules, and each polyacid has four in different directions. The terminal oxygen atoms on the crystal are coordinated, so the crystal is not connected by one-dimensional or two-dimensional connection, but directly centered on the polyacid, forming a three-dimensional network structure, which is a polyacid with a three-dimensional structure. Acid-based nickel metal crystalline hydrogen evolution material, powder X-ray diffraction results show that through the synthesis methods of step one and step two, the tested X-ray diffraction peaks are completely consistent with the simulated single crystal X-ray diffraction peaks, indicating that a large number of single crystals synthesized The material is of high purity. The electrocatalytic hydrolysis test showed that the polyacid-based nickel metal organic-inorganic crystal material has a certain hydrogen evolution performance.

In this embodiment, a three-dimensional polyacid-based nickel metal-organic crystalline catalytic material can be obtained.

Specific embodiment 2: This embodiment is a preparation method of a three-dimensional polyacid-based nickel metal-organic crystalline catalytic material, which is completed according to the following steps:

1. Preparation of a reaction solution with a pH value of 3.2-4.8: Dissolve phosphotungstic acid, metal nickel salt and 4-amino-4H-1,2,4-triazole in deionized water and stir for several hours at room temperature , to obtain a reaction solution; then use sodium hydroxide solution and hydrochloric acid solution to adjust the pH value of the reaction solution to 3.2-4.8 to obtain a reaction solution with a pH value of 3.2-4.8;

The molar ratio of phosphotungstic acid and metal nickel salt described in step 1 is 0.1: (0.4-0.9);

The molar ratio of the phosphotungstic acid described in the step 1 and the 4-amino-4H-1,2,4-triazole organic ligand is: 0.1:0.1;

The volume ratio of the amount of the phosphotungstic acid described in the step 1 and the distilled water is: 0.1 mmol: 10 mL;

2. Add the reaction solution with a pH value of 3.2-4.8 to the reaction kettle of polytetrafluoroethylene, react at a temperature of 160 ° C for 4 days, cool down to room temperature to obtain a green triangular pyramid-shaped crystal, which is a kind of three-dimensional polytetrafluoroethylene. Acid-Based Nickel Metal-Organic Crystalline Catalytic Materials.

晶胞参数为α＝90，β＝90，γ＝90；

Z＝4。Described in step 2 is a polyacid-based dual-nucleic acid-based metal-organic-inorganic crystal material with a polyacid as a template and a preparation method thereof. A molecular formula of H ₅ [PW ₁₂ O ₄₀ ] ₃ [Ni ₂ (OH) ₃ ] ₄ [C ₂ N ₄ H ₄ ] ₁₂ ·12H ₂ O was designed and prepared. The crystal system is cubic, and the space group is

The unit cell parameters are α=90, β=90, γ=90;

Z=4.

Compared with the prior art, this embodiment has the following characteristics:

The crystal material of the invention is synthesized from Keggin-type phosphotungstic acid, 4-amino-4H-1,2,4-triazole and metal nickel salt according to a certain molar ratio by one-step hydrothermal method, which is a novel A crystal material with a triangular structure, in which the two nitrogen atoms on the organic ligands on No. 1 and No. 2 coordinate with metal nickel, and every three ligands are combined with two metal ions, each The No. 1 metal ion is coordinated with three polyacids in different directions, and the No. 2 metal ion is coordinated with the oxygen atoms in the water molecule. Each polyacid has four terminal oxygen atoms in different directions. position, so the crystal is not connected by one-dimensional or two-dimensional connection, but directly centered on polyacid, forming a three-dimensional network structure, which is a polyacid-based nickel metal crystalline hydrogen evolution with three-dimensional structure At the same time, according to the redox performance of polyacid, the electrocatalytic hydrolysis performance of this crystal material was studied in ^0.5MH ₂ SO ₄ solution. .

In this embodiment, a three-dimensional polyacid-based nickel metal-organic crystalline catalytic material can be obtained.

Embodiment 3: The difference between this embodiment and Embodiment 2 is that the metallic silver salts described in step 1 are nickel chloride, nickel sulfate, and nickel nitrate. Others are the same as in the second embodiment.

Embodiment 4: The difference between this embodiment and Embodiments 2 to 3 is that the molar ratio of phosphotungstic acid and metal nickel salt described in step 1 is: 0.1:(0.4-0.9). Others are the same as the second or third embodiment.

Embodiment 5: The difference between this embodiment and Embodiments 2 to 4 is that the molar ratio of the phosphotungstic acid and 4-amino-4H-1,2,4-triazole described in step 1 is: 0.1:0.1. Others are the same as those in the second to fourth embodiments.

Embodiment 6: The difference between this embodiment and Embodiments 2 to 5 is that the volume ratio of the amount of phosphotungstic acid described in step 1 to the volume of distilled water is: 0.1 mmol: 10 ml. Others are the same as those in the second to fifth embodiments.

Embodiment 7: The difference between this embodiment and Embodiments 2 to 6 is: in step 1, the pH value of the reaction solution is adjusted to 3.2-4.8 by using 0.1mol/L～2mol/L hydrochloric acid solution and 0.1mol/L L～2mol/L NaOH solution adjusted to obtain. Others are the same as those in the second to sixth embodiments.

Adopt the following examples to verify the beneficial effects of the present invention:

Embodiment 1: A preparation method of a three-dimensional polyacid-based nickel metal-organic crystalline catalytic material is completed according to the following steps:

1. Prepare a reaction solution with a pH value of 3.2-4.8: dissolve 0.1 mmol phosphotungstic acid and (0.4-0.9) mmol metal nickel salt into 10 ml of deionized water, and then add 0.1 mol of 4-amino-4H-1 to the solution , 2,4-triazole organic ligand to obtain a reaction solution: use 1mol/L _HNO3 solution and 1mol/L NaOH solution to adjust the pH value of the reaction solution to 3.2-4.8 to obtain a reaction with a pH value of 3.2-4.8 liquid;

The volume ratio of the amount of phosphotungstic acid described in step 1 to the volume of deionized water is 0.1 mmol: 10 ml;

2. Add the reaction solution with a pH value of 3.2-4.8 into the polytetrafluoroethylene reaction kettle, react at a temperature of 160 ° C for 4 days, cool down to room temperature to obtain a green triangular pyramid-shaped crystal, which is a kind of three-dimensional structure. The polyacid-based nickel metal crystalline hydrogen evolution material.

The X-single crystal diffraction structure analysis data of a three-dimensional polyacid-based nickel metal-organic crystalline catalytic material prepared in Example 1 is shown in Table 1, and the instrument used is the ApexII single crystal diffractometer of Bruker; Table 1 is Example 1 X-ray diffraction structure analysis data of the prepared polyacid-based metal-organic-inorganic crystal materials with polyacids as templates.

Table 1

^a R ₁ =∑║F _o │─│F _c ║/∑│F _o │, ^b wR ₂ =∑[w(F _o ² ─F _c ² ) ² ]/∑[w(F _o ² ) ² ] ^1/2

It can be seen from Table 1 that the chemical formula of a three-dimensional polyacid-based nickel metal-organic crystalline catalytic material prepared in Example 1 is H ₅ [PW ₁₂ O ₄₀ ] ₃ [Ni ₂ (OH) ₃ ] ₄ [C ₂ N ₄ H ₄ ] ₁₂ 12H ₂ O, the molecular formula is H ₁₂₄ P ₃ W ₃₆ Ni ₈ O ₁₅₆ C ₂₄ N ₄₈ , in the structure of a three-dimensional polyacid-based nickel metal-organic crystalline catalytic material prepared in Example 1, the organic The two nitrogen atoms located on No. 1 and No. 2 on the ligand are coordinated with metal nickel, every three ligands are combined with two metal ions, and each No. 1 metal ion is coordinated with three polyacids in different directions. The No. 2 metal ion is coordinated with the oxygen atom in the water molecule, and each polyacid has four terminal oxygen atoms located in different directions, so the crystal does not pass through one-dimensional or two-dimensional The connection method is directly centered on the polyacid, forming a three-dimensional network structure.

X-ray single crystal diffraction analysis shows that a three-dimensional polyacid-based nickel metal-organic crystalline catalytic material prepared in Example 1 H ₅ [PW ₁₂ O ₄₀ ] ₃ [Ni ₂ (OH) ₃ ] ₄ [C ₂ N The unit cell of ₄ H ₄ ] ₁₂ ·12H ₂ O has three polyanions [PW ₁₂ O ₄₀ ] ^3- (abbreviated as PW ₁₂ ), two nickel ions, three 4-amino-4H-1,2, 4-triazole organic ligands, as shown in Figure 1: Figure 1 is a schematic diagram of the asymmetric structural unit of a three-dimensional polyacid-based nickel metal-organic crystalline catalytic material prepared in Example 1, and 1 in Figure 1 is N, 2 is C, 3 is O, 4 is W, 5 is Ni, and 6 is P;

Ni-N 键键长范围为

所有的这些键长均在合理的范围内。In the structure of a three-dimensional polyacid-based nickel metal-organic crystalline catalytic material prepared in Example 1, there are two crystallographically independent Ni ions, which adopt the same coordination mode; In the shape of two inverted triangles, each Ni ion is coordinated with three oxygen atoms and three nitrogen atoms, and each polyacid has four terminal oxygen atoms located in different directions for coordination. The body and the metal coordinate with each other to form a three-dimensional network crystal structure. Meanwhile, the bond length range of Ni-O bond is

The Ni-N bond length range is

All of these bond lengths are within reasonable limits.

A three-dimensional polyacid-based nickel metal-organic crystalline catalytic material prepared in Example 1 H ₅ [PW ₁₂ O ₄₀ ] ₃ [Ni ₂ (OH) ₃ ] ₄ [C ₂ N ₄ H ₄ ] ₁₂ ·12H ₂ In O, a special structural feature is that its asymmetric unit has a three-dimensional structure, and this structure with nickel as the metal is relatively rare in the previous structures of triazole crystals.

4 is a three-dimensional topology diagram of a three-dimensional polyacid-based nickel metal-organic crystalline catalytic material prepared in Example 1. As shown in the figure, the Keggin-type phosphotungstic acid structural unit is simplified into four-connected nodes, ligands And metal nickel is regarded as a three-connected node. The two kinds of nodes are connected to each other to form a closed eight-membered ring. The ring and the ring are staggered and superimposed in three-dimensional space to form a three-dimensional network structure.

Fig. 5 is the infrared spectrogram of a kind of three-dimensional polyacid-based nickel metal-organic crystalline catalytic material prepared in Example 1; as can be seen from Fig. 5, at 972.5, 959, 812, 612 belong to v(PO _a ), v ( W=O _t ), v _as (WO _b -W) and v _as (WO _c -W) stretching vibration; the vibration peaks in the range of 1000-1700 cm ^-1 are attributed to the organic ligand vibration peaks; at 1635, 1551 The absorption peaks at , 1229 and 1056 cm ^-1 are the vibration absorption peaks of the skeleton ring of the triazole molecule. In addition, the vibrational peak at 3120 cm ^-1 is assigned to the vibrational stretching peak of water molecule in the compound.

6 is a powder X-ray diffraction pattern of a three-dimensional polyacid-based nickel metal-organic crystalline catalytic material prepared in Example 1; as shown in the figure, the measurement data of the crystalline material obtained in the experiment and the simulation obtained by the software according to the standard structure The data are basically coincident, which proves that the crystal material obtained from the experiment is the analyzed structure;

To sum up, the present invention adopts a one-step hydrothermal synthesis method, using organic ligand 4-amino-4H-1,2,4-triazole, metal nickel salt, Keggin-type phosphotungstic acid as reactants, and successfully at 160 ℃ A three-dimensional polyacid-based nickel metal-organic crystalline catalytic material is synthesized; at the same time, the material has certain electrocatalytic hydrolysis performance.

Claims (9)

1. A three-dimensional polyacid-based nickel metal-organic crystalline catalytic material is prepared by a one-step hydrothermal synthesis method, taking metal nickel as a center, adopting 4-amino-4H-1, 2, 4-triazole as an organic ligand and introducing phosphotungstic acid, and has a molecular formula of H ₅ [PW ₁₂ O ₄₀ ] ₃ [Ni ₂ (OH) ₃ ] ₄ [C ₂ N ₄ H ₄ ] ₁₂ ·12H ₂ O, wherein C ₂ N ₄ H ₄ Is 4-amino-4H-1, 2, 4-triazole, the crystal system is a cubic crystal system, and the space group is

The unit cell parameter is alpha-90, beta-90, gamma-90;

Z＝4。

2. a preparation method of a three-dimensional polyacid-based nickel metal-organic crystalline catalytic material comprises the following steps:

firstly, preparing a reaction solution with a pH value of 3.2-4.8: dissolving phosphotungstic acid, metal nickel salt and 4-amino-4H-1, 2, 4-triazole in deionized water, and stirring for several hours at normal temperature to obtain a reaction solution; then adjusting the pH value of the reaction solution to 3.2-4.8 by using a sodium hydroxide solution and a hydrochloric acid solution to obtain a reaction solution with the pH value of 3.2-4.8;

the molar ratio of the phosphotungstic acid to the metal nickel salt in the step one is 0.1 (0.4-0.9);

the molar ratio of the phosphotungstic acid to the 4-amino-4H-1, 2, 4-triazole organic ligand in the step one is 0.1: 0.1;

the volume ratio of the phosphotungstic acid substance in the step one to the distilled water is 0.1mmol:10 mL;

secondly, adding the reaction solution with the pH value of 3.2-4.8 into a polytetrafluoroethylene reaction kettle, reacting for 4 days at the temperature of 160 ℃, cooling to room temperature to obtain a green triangular pyramid crystal, namely the three-dimensional polyacid-based nickel metal-organic crystalline catalytic material.

3. The method as claimed in claim 2, wherein the metal salt in step one is nickel chloride hexahydrate or nickel nitrate.

4. The method for preparing the three-dimensional polyacid based nickel metal-organic crystalline catalytic material according to claim 2, wherein the structural formula of the organic ligand 4-amino-4H-1, 2, 4-triazole in the step one is shown as

5. The method for preparing the three-dimensional polyacid-based nickel metal-organic crystalline catalytic material according to claim 2, wherein the molar ratio of the phosphotungstic acid to the metal nickel salt in the step one is 0.1 (0.4-0.9).

6. The method for preparing the three-dimensional polyacid-based nickel metal-organic crystalline catalytic material according to claim 2, wherein the volume ratio of the amount of the phosphotungstic acid substance to the distilled water in the step one is 0.1mmol:10 mL.

7. The method for preparing the three-dimensional polyacid-based nickel metal-organic crystalline catalytic material according to claim 2, wherein the molar ratio of the phosphotungstic acid to the 4-amino-4H-1, 2, 4-triazole organic ligand in the step one is 0.1: 0.1.

8. The method for preparing the three-dimensional polyacid-based nickel metal-organic crystalline catalytic material according to claim 2, wherein the phosphotungstic acid in the step one is Keggin type phosphotungstic acid.

9. The method for preparing the three-dimensional polyacid-based nickel metal-organic crystalline catalytic material according to claim 2, wherein the pH value of the reaction solution in the step one is adjusted to 3.2-4.8 by using 0.1-2 mol/L HCl solution and 0.1-2 mol/L NaOH solution.

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