CN113388859B - Th-MOF loaded Cu-based single-site catalytic material and preparation method and application thereof - Google Patents

Th-MOF loaded Cu-based single-site catalytic material and preparation method and application thereof Download PDF

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CN113388859B
CN113388859B CN202110543262.2A CN202110543262A CN113388859B CN 113388859 B CN113388859 B CN 113388859B CN 202110543262 A CN202110543262 A CN 202110543262A CN 113388859 B CN113388859 B CN 113388859B
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高志
赖玉莲
陶源
王悦
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East China Institute of Technology
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Abstract

A Th-MOF loaded Cu-based single-site catalytic material, a preparation method and application thereof. The invention belongs to the field of catalytic materials. The invention aims to solve the problem of the prior catalystThe catalytic activity of the catalyst is lower. The catalytic material consists of single-site Cu and Th-MOF materials, wherein the Th-MOF materials are Th-BPYDC, the Th-MOF materials are regular octahedral structures, and a space point group is Fm3m. The method comprises the following steps: step 1, preparing a Th-MOF material; step 2, preparing a copper ion-containing precursor solution; and 3, preparing the Th-MOF loaded Cu-based single-site catalytic material. The Th-MOF loaded Cu-based single-site catalytic material provided by the invention can be used for electroreduction of NO 3 ‑ Application in the synthesis of ammonia. The obtained catalytic material can realize the effect of 225.3 mu mol.h ‑1 ·cm ‑2 And a faradaic efficiency of 92.5%.

Description

Th-MOF loaded Cu-based single-site catalytic material and preparation method and application thereof
Technical Field
The invention belongs to the field of catalytic materials, and particularly relates to a Th-MOF (Th-Metal organic framework) loaded Cu-based single-site catalytic material as well as a preparation method and application thereof.
Background
Ammonia is one of the most common industrial chemicals and plays a central role in national economy. It not only plays an important role in the fields of agriculture, textile industry, pharmaceutical industry and the like, but also can be utilized by human beings as a new generation of green carrier (4.3 kWh/kg) with high energy density. At present, ammonia is industrially synthesized mainly by the traditional Haber-Bosch method, nitrogen and hydrogen are used as raw materials in the process, the reaction conditions are harsh, and the method is a synthetic route with great energy consumption. At present, the technology for synthesizing ammonia by electro-reduction by taking NO 3-as a raw material and water as a hydrogen source has attracted extensive attention due to green, high efficiency and mild reaction conditions, and is a new technology for replacing the traditional high-energy-consumption Haber Bosch method. In addition, the N = O bond energy (204 kJ mol-1) in NO 3-is much lower than the N ≡ N bond energy (941 kJ mol-1) in N2, so that the electroreduction of NO 3-to synthesize ammonia has faster reaction kinetics.
In addition, a large amount of NO 3-in industrial wastewater can cause harm to the environment and human health, and must be purified before being discharged. Therefore, the synthesis of ammonia by the electro-reduction technique using NO3 "as a raw material can solve both energy and environmental problems. At present, various nano composite catalysts have been used for electro-reduction of NO 3-synthetic ammonia, but the large-scale application thereof is limited due to the low catalytic activity and the fuzzy reaction mechanism. Therefore, the development of the electrocatalyst with a definite single crystal structure and low price for realizing the high-efficiency NO 3-reduction synthesis of ammonia has important theoretical significance and practical value.
Disclosure of Invention
The invention provides a Th-MOF loaded Cu-based single-site catalytic material and a preparation method and application thereof, aiming at solving the technical problem of low catalytic activity of the existing catalyst.
The Th-MOF loaded Cu-based single-site catalytic material consists of single-site Cu and a Th-MOF material, wherein the Th-MOF material is Th-BPYDC, the Th-MOF material is in a regular octahedral structure, and a space point group is Fm3m.
The preparation method of the Th-MOF loaded Cu-based single-site catalytic material comprises the following steps:
step 1, preparing a Th-MOF material: dissolving thorium nitrate hexahydrate and 2,2' -bipyridyl-5, 5' -dicarboxylic acid in an N, N ' -dimethylformamide solution, then adding nitric acid, uniformly stirring, transferring to a polytetrafluoroethylene lining, sealing, putting into a high-pressure reaction kettle, reacting in a muffle furnace, centrifuging, washing and drying after the reaction is finished to obtain a colorless octahedral crystal Th-BPYDC, namely a Th-MOF material;
step 2, preparing a copper ion-containing precursor solution: dissolving copper chloride in acetonitrile solution to prepare copper ion-containing precursor solution;
step 3, preparing the Th-MOF loaded Cu-based single-site catalytic material: and (3) adding the Th-MOF material obtained in the step (1) into the copper ion-containing precursor solution obtained in the step (2), uniformly stirring, transferring to a glass bottle, sealing, then putting into a muffle furnace for reaction, and after the reaction is finished, centrifuging, washing and drying to obtain a green octahedral crystal Cu @ Th-BPYDC material, namely the Th-MOF loaded Cu-based single-site catalytic material.
Further defined, the ratio of the amounts of said species of thorium nitrate hexahydrate to 2,2 '-bipyridine-5, 5' -dicarboxylic acid in step 1 is 1: (0.8-1.2).
Further defined, the ratio of the amount of said substance of thorium nitrate hexahydrate to the volume of N, N' -dimethylformamide in step 1 is 1mol: (3-7) L.
Further defining, in step 1, the mass ratio of thorium nitrate hexahydrate to nitric acid is 1: (0.8-1.2).
Further limiting, the specific parameters of the reaction in the muffle furnace in step 1 are as follows: the temperature is 110-130 ℃ and the time is 2-3 days.
Further defined, the ratio of the mass of copper chloride to the volume of acetonitrile in step 2 is 0.5g: (4-6) mL.
Further defined, the ratio of the mass of the Th-MOF material to the volume of the copper ion-containing precursor solution in step 3 is 0.01g: (4-6) mL.
Further limiting, the specific parameters of the reaction in the muffle furnace in step 3 are as follows: the temperature is 70-90 ℃ and the time is 6-8 days.
The Th-MOF loaded Cu-based single-site catalytic material provided by the invention can be used for electroreduction of NO 3 - Application in the synthesis of ammonia.
Compared with the prior art, the invention has the following advantages:
1) The common hydrothermal method is adopted to synthesize the Th-MOF loaded Cu-based single-site catalytic material, the synthesis method is simple, the reaction conditions are safe and mild, the cost is low, the repeatability is high, the preparation method is mature and stable, and the obtained material is easy to apply.
2) Application of Th-MOF loaded Cu-based single-site catalytic material to electrocatalysis of NO 3 - In the reduction field, the performance test result shows that the nitrogen-containing compound is in NO 3 - Excellent NH was selected from a 0.1M KOH (pH = 14) electrolyte solution of 1M concentration 3 Catalytic performance. NH at a wide operating potential of-0.1 to 0.2V vs. RHE 3 The faradaic efficiency of (a) is higher than 70%. RHE was operated at 0V vs. 92.5% maximum Faraday efficiency, NH 3 The production rate of (a) was 225.3. Mu. Mol. H -1 ·cm -2 。
Drawings
FIG. 1 is a photomicrograph of the Th-MOF material (Th-BPYDC) obtained in example 1;
FIG. 2 is a photomicrograph of a Cu @ Th-BPYDC crystal obtained in example 1;
FIG. 3 is a structural diagram showing the arrangement of Cu @Th-BPYDC crystals obtained in example 1;
FIG. 4 is a linear scan curve of Th-BPYDC and Cu @ Th-BPYDC samples;
FIG. 5 is a graph of ammonia yield at different voltages;
FIG. 6 is a graph of ammonia Faraday efficiency at different voltages;
FIG. 7 is a linear scan curve of a Cu @ Th-BPYDC sample before and after 1000 CV cycles;
FIG. 8 is an X-ray diffraction pattern before and after a Cu @ Th-BPYDC sample is stabilized for 1000 CV cycles; wherein 1-the diffraction curve of Cu @ Th-BPYDC obtained in example 1, 2-the diffraction curve after the stability test of Cu @ -Th-BPYDC of example 1, 3-characterizes the diffraction peak.
Detailed Description
Example 1: the preparation method of the Th-MOF loaded Cu-based single-site catalytic material is carried out according to the following steps:
step 1, preparation of a Th-MOF material: dissolving 1mmol of thorium nitrate hexahydrate and 1mmol of 2,2' -bipyridine-5, 5' -dicarboxylic acid in 3mL of N, N ' -dimethylformamide solution, then adding 1mmol of nitric acid, uniformly stirring, transferring to a polytetrafluoroethylene lining, sealing, putting into a high-pressure reaction kettle, heating to 110 ℃ in a muffle furnace at a heating rate of 1 ℃/min, reacting for 3 days at a constant temperature, centrifuging after the reaction is finished, washing with methanol, and drying in vacuum at the temperature of 70 ℃ to obtain colorless octahedral crystal Th-BPYDC (see figure 1), namely a Th-MOF material;
step 2, preparing a copper ion-containing precursor solution: dissolving 0.5g of copper chloride in 5mL of acetonitrile solution to prepare a copper ion-containing precursor solution;
step 3, preparing the Th-MOF loaded Cu-based single-site catalytic material: adding 10mg of the Th-MOF material obtained in the step 1 into 5mL of the copper ion-containing precursor solution obtained in the step 2, uniformly stirring, transferring the mixture into a glass bottle, sealing, then placing the glass bottle into a muffle furnace, heating to 80 ℃ at a heating rate of 1 ℃/min, reacting at a constant temperature for 7 days, centrifuging after the reaction is finished, washing with acetonitrile and methanol in sequence, and drying in vacuum at a temperature of 60 ℃ to obtain a green octahedral crystal Cu @ Th-BPYDC material (see figure 2), namely the Th-MOF loaded Cu-based single-site catalytic material.
The expression of the Th-MOF loaded Cu-based single-site catalytic material obtained in example 1 is as follows: th 6 O 4 (OH) 4 (BPYCuCl 2 ) 6 Wherein BPYCuCl 2 Represents the grafting of CuCl 2 2,2 '-bipyridine-5, 5' -dicarboxylic acid ligand.
The coordination structure of the Th-MOF supported Cu-based single-site catalytic material (Cu @ Th-BPYDC) prepared in example 1 is shown in FIG. 3, the polymer belongs to a cubic system Fm3m space group, and the unit cell parameter a is
Figure BDA0003072407380000031
b is
Figure BDA0003072407380000032
c is a
Figure BDA0003072407380000033
Alpha is 90.00 degrees, beta is 90.00 degrees, gamma is 90.00 degrees and volume is
Figure BDA0003072407380000034
The material is composed of Th 6 O 4 (OH) 4 (H 2 O) 6 Nuclear and BPYCuCl 2 Ligand constitution of each Th 6 O 4 (OH) 4 (H 2 O) 6 The core is connected with 12 BPYCuCl 2 The ligand forms a structure similar to UiO-67, wherein Cu is in a plane four-coordination configuration, is connected by two bipyridyl nitrogen atoms and two chlorine atoms and is an unsaturated coordination site.
Example 2: example 1 preparation of Th-MOF loaded Cu-based Single-site catalytic Material (Cu @ Th-BPYDC) in electro-reduction of NO 3 - Application in ammonia synthesis.
Electroreduction of NO using Cu @ Th-BPYDC prepared in example 1 3 - The results of ammonia synthesis are shown in FIGS. 4 to 8.
As can be seen from FIG. 4, cu @ Th-BPYDC of example 1 had excellent electroreduction of NO 3 - Synthetic ammonia performanceCurrent densities up to 80.7mA cm at-0.1V vs RHE potential -2 Is far superior to Th-BPYDC without Cu. The ammonia generation rate is gradually increased with the increase of the cathode potential (figure 5), but the Faraday efficiency shows a fire hill type trend of increasing and then decreasing (figure 6), and at the optimal voltage of-0.1V vs RHE, the ammonia generation rate and the Faraday efficiency are respectively as high as 225.3 mu mol h -1 cm -2 And 92.5%. The Cu @ Th-BPYDC single-site catalyst had excellent stability, with no degradation in performance after 1000 CV cycles (FIG. 7). As can be seen by comparing XRD (figure 8) data before and after the reaction, the Cu @ Th-BPYDC single-site catalyst keeps a good crystalline structure after the reaction, shows extremely high stability and repeatability and has important significance for green, efficient and sustainable ammonia synthesis.

Claims (9)

1. A preparation method of a Th-MOF loaded Cu-based single-site catalytic material is characterized in that the catalytic material is composed of single-site Cu and a Th-MOF material, wherein the Th-MOF material is Th-BPYDC, the Th-MOF material is a regular octahedral structure, and a space point group isFm3m；
The preparation method comprises the following steps:
step 1, preparing a Th-MOF material: dissolving thorium nitrate hexahydrate and 2,2' -bipyridyl-5, 5' -dicarboxylic acid in an N, N ' -dimethylformamide solution, then adding nitric acid, uniformly stirring, transferring to a polytetrafluoroethylene lining, sealing, putting into a high-pressure reaction kettle, reacting in a muffle furnace, centrifuging, washing and drying after the reaction is finished to obtain a colorless octahedral crystal Th-BPYDC, namely a Th-MOF material;
step 2, preparing a copper ion-containing precursor solution: dissolving copper chloride in an acetonitrile solution to prepare a copper ion-containing precursor solution;
step 3, preparing the Th-MOF loaded Cu-based single-site catalytic material: and (3) adding the Th-MOF material obtained in the step (1) into the copper ion-containing precursor solution obtained in the step (2), uniformly stirring, transferring to a glass bottle for sealing, then putting into a muffle furnace for reaction, and after the reaction is finished, centrifuging, washing and drying to obtain a green octahedral crystal Cu @ Th-BPYDC material, namely the Th-MOF loaded Cu-based single-site catalytic material.
2. The method for preparing the Th-MOF supported Cu-based single-site catalytic material of claim 1, wherein the ratio of the amounts of the substances of thorium nitrate hexahydrate and 2,2 '-bipyridine-5, 5' -dicarboxylic acid in the step 1 is 1: (0.8 to 1.2).
3. The preparation method of the Th-MOF supported Cu-based single-site catalytic material as claimed in claim 1, wherein the ratio of the amount of the substance of thorium nitrate hexahydrate to the volume of N, N' -dimethylformamide in step 1 is 1mol: (3 to 7) L.
4. The preparation method of the Th-MOF supported Cu-based single-site catalytic material as claimed in claim 1, wherein the mass ratio of the thorium nitrate hexahydrate to the nitric acid in step 1 is 1: (0.8 to 1.2).
5. The preparation method of the Th-MOF supported Cu-based single-site catalytic material according to claim 1, wherein the specific parameters of the reaction in the muffle furnace in the step 1 are as follows: the temperature is 110 to 130 ℃, and the time is 2 to 3 days.
6. The preparation method of the Th-MOF loaded Cu-based single-site catalytic material of claim 1, wherein the ratio of the mass of the copper chloride to the volume of the acetonitrile in the step 2 is 0.5g: (4 to 6) mL.
7. The preparation method of the Th-MOF supported Cu-based single-site catalytic material of claim 1, wherein the ratio of the mass of the Th-MOF material to the volume of the copper ion-containing precursor solution in the step 3 is 0.01g: (4 to 6) mL.
8. The preparation method of the Th-MOF supported Cu-based single-site catalytic material according to claim 1, wherein the specific parameters of the reaction in the muffle furnace in the step 3 are as follows: the temperature is 70 to 90 ℃, and the time is 6 to 8 days.
9. The use of the Th-MOF supported Cu-based single-site catalytic material prepared by the method of claim 1 in the electroreduction of NO 3 - The method is applied to the reaction of synthesizing ammonia.
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