Mocp-ag crystal materials, methods of making and uses thereof

Abstract

The application provides a MOCPs-Ag crystal material and a preparation method and application thereof, the molecular formula of the MOCPs-Ag crystal material is Ag[(PMA) 0.5 (DPE)]*4H2O, wherein PMA is 1,2,4,5-benzene tetraformic acid, and DPE is 1,2-di(4-pyridyl)ethylene ligand; the crystal belongs to a triclinic crystal system P space group, and cell parameters are alpha=66.377 (4) °, beta=86.301 (3) °, gamma=71.838 (3) °, a=10.6957 (4) Å, b=12.4200 (5) Å, c=14.3193 (6) Å, and a cell volume is 1651.97 Å 3 , and Z=2. The application synthesizes a MOCPs-Ag crystal material by using a simple room temperature solvent volatilization method, and the MOCPs-Ag crystal material can be used as a catalyst for electrocatalytic carbon dioxide reduction, and high-efficiency carbon dioxide reduction to carbon monoxide is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to a MOCPs-Ag crystal material and a preparation method and use thereof, and belongs to the technical field of catalyst preparation. BACKGROUND

[0002] The use of fossil fuels has forced the concentration of carbon dioxide in the atmosphere to show a sharp upward trend. This not only leads to climate abnormalities, ice and snow melting and other problems, but also has a major negative impact on people's daily life. How to effectively reduce the concentration of CO2 in the atmosphere is another major challenge facing the world. Therefore, it is necessary to use some methods to reduce CO2 emissions from the source and convert them into valuable products. The electrochemical conversion of CO2 has the advantages of mild reaction conditions, adjustable product selectivity, etc. Effective transfer of protons and electrons to the catalyst is crucial for ECR. Compared with composite proton and electron conductive electrocatalysts (PECEs), single-phase PECEs can simultaneously and uniformly provide catalytic activity, proton conduction and electron conduction in one material, which is a very promising method. Therefore, it is of great significance to design new materials that facilitate the adjustment of proton and electron conduction, so as to realize the regulation of ECR performance at the molecular level.

[0003] Metal-organic coordination polymers (MOCPs) can be converted into various morphologies and structures and adjustable metal centers due to the dynamic nature of coordination bonds, and have broad application prospects in the field of ECR. Compared with traditional metal materials and metal oxides, MOCPs have the following advantages: (1) well-defined catalytic site structure stability; (2) high intrinsic electronic conductivity to promote charge transport; (3) MOCPs combine the beneficial properties of homogeneous and heterogeneous catalysts, serving as host materials to bind guest active catalysts for synergistic catalysis (4) well-defined structure greatly facilitates the understanding of the structure-performance of MOCP-based catalysts in the mechanism of catalytic process. However, most MOCPs catalysts lack sufficient conductivity and stability in the ECR process, and the selection of appropriate ligands and / or metal centers and guest molecules can regulate the electronic or proton transport capacity of MOCPs. Therefore, MOCPs are expected to develop into ideal materials for single-phase PECEs. SUMMARY

[0004] The purpose of the present application is to provide a MOCPs-Ag crystal material and a preparation method and use thereof, in order to solve the above-mentioned problems existing in the prior art.

[0005] The present application is realized by the following technical solutions:

[0006] A MOCPs-Ag crystal material, whose molecular formula is Ag[(PMA) 0.5(DPE)·4H2O, wherein PMA is 1,2,4,5-benzenetetracarboxylic acid, and DPE is 1,2-bis(4-pyridyl)ethene ligand; the crystal belongs to triclinic system with space group, and cell parameters are α = 66.377(4)°, β = 86.301(3)°, γ = 71.838(3)°, with cell volume of Z = 2.

[0007] As a preferred solution, the MOCPs-Ag crystal material is crystallographically Ag + The two-coordinated mode is used to coordinate with two 1,2-bis(4-pyridyl)ethene ligands to form a one-dimensional chain through Ag-N bond bridging, 1,2,4,5-benzenetetracarboxylic acid forms a hydrogen bond with adjacent water molecules, and the carboxylic acid ligand is connected through intermolecular hydrogen bond interaction to form a layered hydrogen bond network structure, and the overall spatial structure is that adjacent one-dimensional chains are connected through two π···π interaction forces between 1,2-bis(4-pyridyl)ethene pyridine rings, and the distances are and The π···π stacking interaction is further extended to a two-dimensional layered structure, and the distance between the H atom on the pyridine ring and the centroid of the carboxylic acid ligand between adjacent columnar structures is A three-dimensional molecular structure is formed through C-H···π interaction.

[0008] A preparation method of the MOCPs-Ag crystal material as described above, comprising the following steps:

[0009] The water-soluble silver salt, 1,2,4,5-benzenetetracarboxylic acid, and 1,2-bis(4-pyridyl)ethene are dissolved in a mixed solution of ethanol and distilled water, mixed uniformly, and then concentrated ammonia is added, and the slow evaporation is carried out at room temperature in the dark to obtain the MOCPs-Ag crystal material.

[0010] As a preferred solution, the molar ratio of the water-soluble silver salt, 1,2,4,5-benzenetetracarboxylic acid, and 1,2-bis(4-pyridyl)ethene is 1:1:1.

[0011] As a preferred solution, the water-soluble silver salt is silver nitrate.

[0012] As a preferred solution, the time of the slow evaporation reaction in the dark is 1 week.

[0013] The use of the MOCPs-Ag crystal material as described above in an electrocatalytic reduction working electrode, which can reduce CO2 to CO.

[0014] A preparation method of the electrocatalytic reduction working electrode as described above, comprising the following steps:

[0015] The MOCPs-Ag crystal material is dissolved in a mixture of ethanol, distilled water and nafion as an electrocatalytic agent, and then sprayed on the surface of carbon paper to obtain an electrocatalytic reduction working electrode.

[0016] A method for constructing an electrocatalytic CO2 reduction device by using the electrocatalytic reduction working electrode, comprising the following steps:

[0017] A three-electrode system is constructed by using an H-type electrolytic cell as an electrolytic cell, a saturated Ag-AgCl electrode as a reference electrode, a platinum mesh electrode as a counter electrode, and the electrocatalytic reduction working electrode, and the electrolytic cell solution used in the cathode chamber and the anode chamber of the electrolytic cell is 0.5 mol / L KHCO3 solution.

[0018] A product detection method for reducing CO2 by using the electrocatalytic CO2 reduction device, comprising the following steps:

[0019] The gas-phase product of the reduction reaction is detected by gas chromatography, and the liquid-phase product of the reduction product is detected by nuclear magnetic resonance spectroscopy.

[0020] Compared with the prior art, the present application has the following beneficial effects:

[0021] The present application synthesizes a MOCPs-Ag crystal material by using a simple room temperature solvent evaporation method, which can be used as a catalyst for electrocatalytic reduction of carbon dioxide, and realizes efficient reduction of carbon dioxide to carbon monoxide. BRIEF DESCRIPTION OF DRAWINGS

[0022] Other features, objects and advantages of the present application will become more apparent from the following detailed description of non-limiting embodiments, made with reference to the accompanying drawings:

[0023] Figure 1 is a molecular structure diagram of FJU-223-Dpe of embodiment 1 of the present application, wherein (a) is the simplest asymmetric unit of FJU-223-Dpe, (b) is the construction mode, (c) is the water network connection mode, (d) is the π···π interaction force, and (f) is the three-dimensional structure analysis;

[0024] Figure 2 is an infrared spectrum analysis spectrum diagram of FJU-223-Dpe of embodiment 1 of the present application;

[0025] Figure 3 is a thermogravimetric analysis spectrum diagram of FJU-223-Dpe of embodiment 1 of the present application;

[0026] Figure 4 is a schematic diagram of an electrolytic device of embodiment 3 of the present application;

[0027] Figure 5 is the LSV plot of FJU-223-Dpe of the present application embodiment 3;

[0028] Figure 6 is the Faraday efficiency plot of FJU-223-Dpe of the present application embodiment 4 at different potentials;

[0029] Figure 7 is the XRD pattern of FJU-223-Dpe of the present application embodiment 6 after soaking in electrolyte solution;

[0030] Figure 8 is the CA plot of FJU-223-Dpe electrolysis 1h of the present application embodiment 7. DETAILED DESCRIPTION

[0031] The application will be described in detail below with specific embodiments. The following examples will help those skilled in the art to further understand the application, but in no way limit the application. It should be noted that for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made. These are within the scope of the present application.

[0032] Example 1

[0033] The present embodiment provides a preparation method of MOCPs-silver material, which specifically comprises the following steps:

[0034] Silver nitrate (AgNO3, 1 mmol, 0.17 g), 1,2,4,5-benzene-tetracarboxylic acid (PMA, 1 mmol, 0.254 g), 1,2-di(4-pyridyl)ethylene (DPE, 1 mmol, 0.182 g) were dissolved in ethanol (5 mL) and distilled water (5 mL), and 1 ml NH 3· H2O was added, and the mixture was ultrasonically treated for 30 min to obtain a transparent mixture. Then, the transparent mixture was placed in a light-proof carton at room temperature 25℃, the bottle cap was loosened, and the mixture was slowly evaporated at room temperature for one week to obtain yellow block-shaped crystal MOCPs-silver material, which is recorded as FJU-223-Dpe, and the molecular formula is Ag[(PMA) 0.5 (DPE)]·4H2O, and the yield is 80%.

[0035] The diffraction intensity data of the MOCPs-silver material were collected by Agilent Technologies SuperNova single crystal diffractometer. The crystal data and structure refinement parameters of the MOCPs-silver material are listed in Table 1. The single crystal X-ray diffraction analysis results show that the MOCPs-silver material belongs to a triclinic crystal system with a space group.

[0036] Table 1. Relevant crystal data of MOCPs-silver material (FJU-223-Dpe)

[0037]

[0038] The crystal structure of MOCPs-silver material was analyzed in detail, as shown in Figure 1 (a), Ag + The two-coordinated coordination mode coordinates with two 1,2-di(4-pyridyl)ethylene ligands and forms a one-dimensional chain by Ag-N bond bridging as shown in Figure 1 (b). The 1,2,4,5-benzene tetracarboxylic acid forms a hydrogen bond with adjacent water molecules, and the carboxylic acid ligands are connected by intermolecular hydrogen bond interaction to form a layered hydrogen bond network structure as shown in Figure 1 (c). The overall spatial structure is further extended to a two-dimensional layered structure by the π···π and stacking interaction between the pyridine rings of adjacent one-dimensional chains as shown in Figure 1 (d). The distance between the H atoms on the pyridine ring and the centroid of the carboxylic acid ligand between adjacent columnar structures is A three-dimensional molecular structure is formed by this C-H···π interaction as shown in Figure 1 (e).

[0039] The infrared spectrum of FJU-223-Dpe was tested by a Fourier transform infrared spectrometer (FT-IR), and the infrared spectrum (FT-IR) was determined by a Nicolet 5700 FT-IR Fourier transform infrared spectrometer, KBr tabletting, and the determination range was 4000-400 cm -1 As shown in Figure 2 , according to the obtained results, the peak near 1554 cm -1 corresponds to the C=N stretching vibration peak, the peak near 3092 cm -1 corresponds to the C-H characteristic peak of the benzene ring, and the peak at 1423 cm -1 corresponds to the C=C stretching vibration of the benzene ring. The peaks at about 1612 cm -1 and 1355 cm -1 correspond to the C=O asymmetric stretching vibration and C-O symmetric stretching vibration of the carboxyl group, respectively. Based on the above infrared analysis results, it is shown that FJU-223-Dpe contains the relevant functional groups of PMA and DPE.

[0040] The weight loss of the material was tested by thermal gravimetric analysis. The thermal gravimetric (TGA) characterization was determined on a METTLER STA D851e thermal gravimetric analyzer, under nitrogen atmosphere, the weight loss was tested at a temperature range of 30-600℃, with a heating rate of 10℃ / min. According to the results, the material had three weight loss stages, as shown in Figure 3 Figure 1: The first weight loss was at 106℃-231.7℃, which was the process of losing crystal water of the complex; from 231.7℃, the ionic bonds and coordination bonds in the complex began to break, and the skeleton began to decompose, and when the temperature reached 281℃, the decomposition was basically completed, indicating that FJU-223-Dpe had good thermal stability.

[0041] Comparative Example 1

[0042] The difference between this comparative example and Example 1 is only that the transparent mixture was not subjected to solvent evaporation under light-proof conditions, and as a result, the solution was clear and no product was obtained. This is because the silver ions were reduced to elemental silver by the silver mirror reaction in the absence of light, which adhered to the container wall and could not participate in the reaction to obtain crystals.

[0043] Example 2

[0044] This example relates to a method for preparing FJU-223-Dpe as a catalyst working electrode, which specifically comprises the following steps: The above-mentioned crystal material is ground into a powder, 10 mg of which is dispersed in 1 mL of a mixed solution (700 μL of isopropyl alcohol, 150 μL of distilled water, and 150 μL of a 5 wt% Nanion solution), and after ultrasonic treatment for 30 min, a uniformly dispersed catalyst ink is obtained. Then, 1 mL of the ink solution is uniformly sprayed onto a 2×3 cm 2 carbon paper using a spray pen, and the carbon paper is dried at room temperature to obtain a catalyst gas diffusion electrode (GDL), i.e., a working electrode.

[0045] Example 3

[0046] This example relates to an electrochemical test method for electrocatalytic reduction of carbon dioxide, which specifically comprises the following steps: The experiment was carried out in an H-type electrolytic cell for carbon dioxide, and a cation exchange membrane (Nafion 117) was used to separate the cathode and the anode. An Ag / AgCl electrode was used as a reference electrode (stored in a potassium chloride saturated solution before use), a platinum mesh electrode was used as a counter electrode, and a carbon paper loaded with a catalyst was used as a working electrode. The working electrode and the reference electrode were placed in the cathode chamber, and the counter electrode was placed in the anode chamber (as Figure 4 shown in the schematic diagram of the electrolysis device). The electrolyte solution was a 0.5 M potassium bicarbonate aqueous solution, and the electrolyte was pre-saturated with Ar (pH=8.2) or CO2 (pH=7.83) before use. The voltage conversion formula is as follows: RHE V Ag / AgCl + V0 Ag / AgClvsNHE +0.059pH wherein V 0 Ag / AgClvsNHE =0.199V

[0047] Example 4

[0048] This example relates to FJU-223-Dpe as a catalyst for electrocatalytic reduction of carbon dioxide, and specifically includes the following steps: In order to preliminarily explore the CO2 electroreduction performance of the FJU-223-Dpe catalyst, the polarization curves of the catalyst in Ar-saturated and CO2-saturated KHCO3 solutions were tested, as shown in FIG. 6: in the Ar-saturated KHCO3 solution, the starting potential of the polarization curve was -1.4 V (vs Ag / AgCl), indicating that the catalyst had a relatively high hydrogen evolution (HER) overpotential; in the CO2-saturated KHCO3 solution, the starting potential of the polarization curve was -1.3 V (vs Ag / AgCl), which was different from the polarization curve in the Ar-saturated case, and the current increased in the CO2-saturated case, preliminarily indicating that there was a carbon dioxide reduction reaction and the corresponding current was generated. Figure 5

[0049] Example 5

[0050] This example relates to the reaction steps COOH, CO and the competing reaction HER considered in the electrochemical reduction of carbon dioxide, and is shown in the following formula:

[0051]

[0052] Example 6

[0053] This example relates to the determination of the optimal working potential of FJU-223-Dpe as a catalyst, and specifically includes the following steps: Based on the above-mentioned Example 4, the FJU-223-Dpe catalyst was tested at different potentials in the potential range where the products may exist, and the products were analyzed accordingly, and the Faraday efficiency (FE%) of different products at different potentials was calculated, as shown in FIG. 7: the carbon dioxide reduction products of the catalyst were basically CO and H2, and only a small amount of formic acid was produced. The FE Figure 7 of FJU-223-Dpe remained above 70% in a wide potential range of -1.4 V to -2 V (vs Ag / AgCl), and the Faraday efficiency of CO was optimal at -1.8 V (vs Ag / AgCl), which was 77.3%, and the selectivity of the product CO could be improved by controlling the electrolysis potential. CO

[0054] Example 7

[0055] ​​The present example relates to the stability test of FJU-223-Dpe as catalyst electrolyte solution environment, the specific implementation scheme is as follows: the purity of the synthesized material is judged by comparing the position and intensity of the diffraction peak by X-ray powder diffraction (XRD), and the water stability of the material in the electrolyte solution is characterized by XRD, as shown in Figure 7 The powder diffraction pattern of the synthesized crystal material is basically consistent with the diffraction peak position simulated by the SC-XRD data in the literature, the material still maintains good crystallinity after being soaked in the 0.5M KHCO3 electrolyte solution, and the material structure does not collapse obviously. The test results show that the material FJU-223-Dpe crystal material has good stability in the electrolyte environment.

[0056] Example 8

[0057] The present example relates to the stability test of FJU-223-Dpe as catalyst electrolyte solution environment, the specific implementation scheme is as follows: the purity of the synthesized material is judged by comparing the position and intensity of the diffraction peak by X-ray powder diffraction (XRD), and the water stability of the material in the electrolyte solution is characterized by XRD, as shown in Figure 8 The powder diffraction pattern of the synthesized crystal material is basically consistent with the diffraction peak position simulated by the SC-XRD data in the literature, the material still maintains good crystallinity after being soaked in the 0.5M KHCO3 electrolyte solution, and the material structure does not collapse obviously. The test results show that the material FJU-223-Dpe crystal material has good stability in the electrolyte environment.

[0058] The above describes the specific embodiments of the present application. It should be understood that the present application is not limited to the above specific embodiments, and those skilled in the art can make various modifications or modifications within the scope of the claims, which does not affect the essential content of the present application.

Claims

1. A MOCPs-Ag crystalline material, characterized in that, Formula is Ag [(PMA) 0.5 (DPE)]•4H2O, wherein PMA is 1,2,4,5-benzene tetraformic acid, and DPE is 1,2-di(4-pyridyl)ethylene ligand; the crystal belongs to triclinic crystal system P space group, the cell parameters are α=66.377(4)°, β=86.301(3)°, γ=71.838(3)°, a=10.6957(4)Å, b=12.4200(5)Å, c=14.3193(6)Å, and the cell volume is 1651.97 Å 3 , and Z=2.

2. The MOCPs-Ag crystal material of claim 1, wherein, Crystallographically, Ag + The two 1,2-di(4-pyridyl)ethene ligands are coordinated to Ag(Ⅰ) in a bidentate fashion and bridged by Ag-N bonds to form a one-dimensional chain. 1,2,4,5-benzenetetracarboxylic acid forms hydrogen bonds with adjacent water molecules, and the carboxylate ligands are connected by intermolecular hydrogen bonds to form a layered hydrogen bond network structure. The overall spatial structure is that adjacent one-dimensional chains are further extended into a two-dimensional layered structure through two π···π interactions between the pyridine rings of 1,2-di(4-pyridyl)ethene with distances of 3.706 Å and 3.848 Å, respectively. The distance between the H atom on the pyridine ring and the centroid of the carboxylate ligand between adjacent columnar structures is 2.595 Å, and a three-dimensional molecular structure is formed through C-H···π interactions.

3. A method for preparing MOCPs-Ag crystalline materials as claimed in claim 1 or 2, characterized by, The method comprises the following steps: The water-soluble silver salt, 1,2,4,5-benzene tetraacid and 1,2-di(4-pyridyl)ethylene are dissolved in a mixed solution of ethanol and distilled water, and then mixed uniformly, and then concentrated ammonia is added, and the slow evaporation is carried out at room temperature in the dark to obtain the MOCPs-Ag crystal material.

4. The method for preparing MOCPs-Ag crystal material as described in claim 3, characterized in that, The molar ratio of the water-soluble silver salt, 1,2,4,5-benzene tetraacid and 1,2-di(4-pyridyl)ethylene is 1:1:

1.

5. The method for preparing MOCPs-Ag crystal material as described in claim 4, characterized in that, The water-soluble silver salt is silver nitrate.

6. The method for preparing MOCPs-Ag crystal material as described in claim 3, characterized in that, The time of the slow evaporation reaction in the dark is 1 week.

7. The use of the MOCPs-Ag crystal material in claim 1 in an electrocatalytic reduction working electrode, wherein the electrocatalytic reduction working electrode can reduce CO2 to CO.

8. A method of preparing an electrocatalytic reduction working electrode as claimed in claim 7, characterized in that, The method comprises the following steps: After the MOCPs-Ag crystal material is dissolved in a mixed solution of ethanol, distilled water and nafion, the mixed solution is sprayed on the surface of carbon paper to obtain an electrocatalytic reduction working electrode.

9. A method for constructing an electrocatalytic CO2 reduction device using the electrocatalytic reduction working electrode of claim 8, characterized in that, The method comprises the following steps: An H-type electrolytic cell is used as an electrolytic cell, a saturated Ag-AgCl electrode is used as a reference electrode, a platinum mesh electrode is used as a counter electrode, and the electrocatalytic reduction working electrode is used to construct a three-electrode system, and the electrolytic cell solution used in the cathode chamber and the anode chamber of the electrolytic cell is 0.5 mol / L KHCO3 solution.

10. A product detection method for reducing CO2 using the electrocatalytic CO2 reduction device according to claim 9, characterized by, The method comprises the following steps: The gas-phase product of the reduction reaction is detected by gas chromatography, and the liquid-phase product of the reduction product is detected by nuclear magnetic resonance spectroscopy.

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