Bismuth-based metal-organic framework material with disordered coordination environment and preparation method thereof

Abstract

The application provides a preparation method of a coordination environment disordered bismuth-based metal organic framework material, comprising the step of heating the bismuth-based metal organic framework material by a joule heating device, and simultaneously provides the coordination environment disordered bismuth-based metal organic framework material prepared by the method and application thereof in preparation of an electrocatalytic carbon dioxide reduction reaction catalyst. The coordination environment disordered bismuth-based metal organic framework material promotes the reduction process of Bi 3+ to Bi element in an electrochemical reduction process, causes the reduced Bi 0 nanosheet to exist stress, greatly enhances the current density during the reaction in a wide voltage range, improves the CO2 reduction efficiency, and has the advantages of simple preparation method, high synthesis yield, short period and convenient operation.

Description

Technical Field

[0001] This invention relates to the fields of nanomaterials and electrochemical technology, specifically to a bismuth-based metal-organic framework material with disordered coordination environment and its preparation method. Background Technology

[0002] Electrocatalytic carbon dioxide reduction (CRR) is a promising strategy for CO2 capture, storage, and utilization. It can convert CO2 into usable fuels and value-added chemical products such as CO, CH4, HCOOH, C2H5OH, and hydrocarbons. Formic acid (HCOOH) holds promise as a hydrogen carrier and feedstock for direct use in fuel cells. Researchers are working to screen and design electrocatalytic methods to reduce CO2 to HCOOH / HCOO. - Significant efforts have been made in developing materials. However, due to the thermodynamically stable nature of carbon dioxide, high electrical energy input is required, posing further challenges to the selective conversion of carbon dioxide into specific products. Therefore, developing highly active, selective, stable, yet inexpensive electrocatalysts remains an ongoing challenge for the widespread commercialization of this technology.

[0003] Bismuth (Bi) is considered a good catalyst choice due to its cost-effectiveness, global abundance, non-toxicity, and low activity in the hydrogen evolution reaction (HER). Metal-organic frameworks (MOFs) with unsaturated metal sites have the potential to capture carbon dioxide, thereby promoting the concentration of carbon dioxide on the electrode surface. This further helps overcome the mass transfer limitation caused by the low solubility of carbon dioxide and improves the frequency of electrochemical carbon dioxide conversion. However, during the electrocatalytic reduction of carbon dioxide, the catalytic material also undergoes chemical composition and structural reconstruction. For example, Bi-MOFs can spontaneously reduce to Bi under operating conditions. 0 , and by Bi 0 It acts as a catalyst. The reconstructed Bi... 0 Bi-MOFs exhibit different structures due to the variety of ligands, such as nanoparticles and nanosheets. However, the remodeling process and its underlying causes remain unclear, resulting in a lack of research on the regulation of the final morphology, chemical valence state, and active sites. Summary of the Invention

[0004] To address the problems existing in the background art, this invention provides a bismuth-based metal-organic framework material with disordered coordination environment, its preparation method, and its applications. The preparation method is simple and efficient. This bismuth-based metal-organic framework material with disordered coordination environment exhibits excellent electrochemical performance, and after electroreduction, Bi... 0 The presence of stress within the nanosheets significantly enhances the current density during the electrocatalytic CO2 reduction reaction, and the preparation method is simple, efficient, and inexpensive.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0006] On one hand, the present invention provides a method for preparing bismuth-based metal-organic framework materials with disordered coordination environment, including the step of heating the bismuth-based metal-organic framework material with a Joule heating device.

[0007] Furthermore, the current of the Joule heating device is set to 100-110A, the heating time is 4-6s, and the heating atmosphere is nitrogen.

[0008] Furthermore, the current of the Joule heating device is set to 105A, and the heating time is 5s.

[0009] Furthermore, the bismuth-based metal-organic framework material is synthesized via a hydrothermal method.

[0010] Furthermore, the preparation steps of the bismuth-based metal-organic framework material include:

[0011] Bismuth salt and polycarboxylic acid organic ligand were added to a solvent and stirred to obtain a suspension; and

[0012] The suspension was placed in a reaction vessel and heated to obtain the bismuth-based metal-organic framework material.

[0013] Furthermore, the molar ratio of the bismuth salt to the polycarboxylic acid organic ligand is 1:2 to 20, and the concentration of the bismuth salt in the suspension is 0.003 mmol to 0.05 mmol / L.

[0014] Furthermore, the bismuth salt is selected from at least one of bismuth nitrate pentahydrate and bismuth acetate, the polycarboxylic acid organic ligand is at least one of trimellitic acid, terephthalic acid or 3,5-pyridinedicarboxylic acid, and the solvent is methanol or a mixed solution of methanol and N,N-dimethylformamide.

[0015] Furthermore, the reaction temperature of the suspension in the reactor is 110–150°C, and the reaction time is 6–24 hours.

[0016] Secondly, the present invention provides a bismuth-based metal-organic framework material with disordered coordination environment, which is prepared by the above-described preparation method.

[0017] Thirdly, the present invention provides the application of the above-mentioned disordered coordination environment bismuth-based metal-organic framework material in the preparation of electrocatalytic carbon dioxide reduction catalyst.

[0018] The principle of this invention is: by using Joule heating, the material is rapidly heated to its melting temperature and then rapidly cooled, so that its atoms cannot be adjusted to their original state, thus forming a bismuth-based metal-organic framework material with a disordered coordination environment.

[0019] The beneficial effects of this invention are: compared to the original bismuth-based metal-organic framework material, the bismuth-based metal-organic framework material with disordered coordination environment of this invention does not change its basic morphological characteristics such as size, shape, and specific surface area, but its coordination environment is altered. When used as a catalyst for the electroreduction of carbon dioxide, it promotes the electrochemical reduction of Bi... 3+ The reduction process of Bi elemental leads to the reduction of Bi. 0 The stress within the nanosheets significantly enhances the current density during the reaction over a wide voltage range, thereby improving the efficiency of CO2 reduction. Furthermore, the preparation method for this disordered coordination environment bismuth-based metal-organic framework material is simple, yields high results, has a short cycle time, and is easy to operate. Attached Figure Description

[0020] Figure 1 The images shown are scanning electron microscope (SEM) images of Bi-MOF-JH nanosheets and Bi-MOF nanosheets from Example 1 of this invention. Figure 1 a and 1b are Bi-MOF-JH nanosheets and Bi-MOF nanosheets, respectively;

[0021] Figure 2 These are high-resolution transmission electron microscopy images of Bi-MOF-JH nanosheets and Bi-MOF nanosheets in Example 1 of this invention, wherein... Figure 2 a and 2b are Bi-MOF-JH nanosheets and Bi-MOF nanosheets, respectively;

[0022] Figure 3 The images show the XRD patterns of Bi-MOF-JH nanosheets and Bi-MOF nanosheets in Example 1 of this invention.

[0023] Figure 4 The extended X-ray absorption fine structure (EXAFS) spectra of Bi-MOF-JH nanosheets and Bi-MOF nanosheets in Example 1 of this invention are shown, with Bi2O3 and Bi foil as standard samples.

[0024] Figure 5 The diagram shows the Faradaic efficiency of Bi-MOF-JH nanosheets as an electrocatalytic active material for carbon dioxide in Embodiment 1 of this invention, under room temperature conditions and with an applied voltage of –1.6V to –2.1V, in catalyzing the conversion of carbon dioxide to formic acid.

[0025] Figure 6 This is a comparison of the partial current densities of Bi-MOF-JH nanosheets and Bi-MOF nanosheets as electrocatalytic active materials for carbon dioxide at room temperature under a voltage of –1.6V to –2.1V to catalyze the conversion of carbon dioxide into formic acid in Embodiment 1 of the present invention.

[0026] Figure 7The images show a high-resolution transmission image and a stress distribution diagram of the reduced Bi-MOF-JH nanosheets in Example 1 of this invention. Detailed Implementation

[0027] The principles and features of the present invention are described below with reference to the accompanying drawings and specific embodiments. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0028] In this invention, the inventors use Joule heating to heat the bismuth-based metal-organic framework material, rapidly raising its temperature to the melting temperature of the bismuth-based metal-organic framework material, and then rapidly cooling it so that the atoms cannot be adjusted to their original state, forming a bismuth-based metal-organic framework material with disordered coordination environment.

[0029] Example 1

[0030] The specific steps for preparing bismuth-based metal-organic framework materials with disordered coordination environments are as follows:

[0031] (1) At room temperature, 150 mg of bismuth nitrate pentahydrate and 750 mg of pyromellitic acid were added to 60 ml of methanol and stirred for 30 min to obtain a suspension.

[0032] (2) Add the above suspension to a 100ml polytetrafluoroethylene-lined stainless steel reactor and place it in an oven preheated to 120℃ for 24 hours.

[0033] (3) After the reaction was completed, the mixture was cooled in air, washed five times with methanol, and dried in a 60°C oven to obtain bismuth-based metal-organic framework (Bi-MOF) nanosheets.

[0034] (4) The dried white powdered bismuth-based metal-organic framework material was heated in a nitrogen atmosphere using a Joule heating device with the following parameters: current 105A and heating time 5s, to obtain bismuth-based metal-organic framework (Bi-MOF-JH) nanosheets with disordered coordination environment.

[0035] The morphological characteristics, phase composition, and interatomic distance of the prepared Bi-MOF-JH nanosheets and Bi-MOF nanosheets were determined.

[0036] Scanning electron microscopy (SEM) results are as follows Figure 1 As shown, Figure 1 a and 1b represent Bi-MOF-JH nanosheets and Bi-MOF nanosheets, respectively, both with side lengths ranging from 1 μm to 5 μm. Joule heating showed almost no change in the morphology of the bismuth-based metal-organic framework (Bi-MOF). High-resolution transmission electron microscopy (HRTEM) results are shown below. Figure 2 As shown, Figure 2a and 2b are Bi-MOF-JH nanosheets and Bi-MOF nanosheets, respectively. As can be seen from the figure, the Bi atoms in the Bi-MOF nanosheets are isolated, while the Bi atoms in the Bi-MOF-JH nanosheets are partially aggregated to form blurred grain boundaries. This proves that Joule heating causes the Bi sites to no longer be in their original isolated distribution, thus changing the coordination of Bi.

[0037] The phases were determined by X-ray diffraction (XRD), and the interatomic distances were determined by extended X-ray absorption fine structure spectroscopy (EXAFS). The results are as follows: Figure 3 and Figure 4 As shown, Figure 3 The Bi-MOF-JH nanosheets exhibit an overall amorphous structure. Figure 4 The results show that the Bi-O bond length in the Bi-MOF-JH nanosheets is longer than that in the Bi-MOF nanosheets, which also proves the change in the coordination structure around the Bi site.

[0038] The Bi-MOF-JH material and Bi-MOF material prepared above were applied to electrodes for carbon dioxide reduction, respectively, as follows:

[0039] Fabrication of the gas diffusion electrode: Cut the gas diffusion electrode into rectangles 2cm wide and 5cm long for later use. Disperse 10mg Bi-MOF-JH in 2ml anhydrous ethanol, then add 50μL Nafion and sonicate for 5-10 minutes to ensure uniform dispersion. Coat the prepared ink evenly onto the gas diffusion electrode and allow it to air dry to form a Bi-MOF-JH nanomaterial-supported gas diffusion electrode. The fabrication of the Bi-MOF nanosheet-supported gas diffusion electrode uses the same method, except that Bi-MOF-JH is replaced with Bi-MOF. It is important to note that before coating, the prepared carbon paper electrode should be wiped 2-3 times with deionized water and alcohol to remove dust and impurities adhering to its surface, improving the adhesion strength between the material and the gas diffusion electrode surface.

[0040] Carbon dioxide reduction was performed using gas diffusion electrodes supported on Bi-MOF-JH nanosheets and Bi-MOF nanosheets, respectively. The electrolyte was 1M KOH, and the reference electrode was a saturated Ag / AgCl reference electrode. With an applied voltage range of -1.6V to -2.1V in 0.1V intervals, the Faradaic efficiency and local current density of the electrocatalytic conversion of carbon dioxide to formic acid were measured. The Faradaic efficiency of the electrocatalytic conversion of carbon dioxide to formic acid using the gas diffusion electrode supported on Bi-MOF-JH nanosheets is shown below. Figure 5 As shown, the local current density is as follows Figure 6 As shown in Table 1 below:

[0041] Table 1

[0042] Faraday efficiency 97.5％ 99.8％ 98.8％ 98.5％ 98％ 99.7％ <![CDATA[current density (mA / cm 2 )]]> -16.88 -55.69 -92.98 -146.85 -193.08 -233.79

[0043] The Faraday efficiency of the electrocatalytic conversion of carbon dioxide to formic acid using a gas diffusion electrode supported on Bi-MOF nanosheets is shown in Table 2 below.

[0044] Table 2

[0045] Faraday efficiency 77.5％ 87.9％ 92.9％ 86.5％ 69.3％ 55.5％ Partial current density -10.15 -19.34 -37.12 -52.95 -56.8 -78.74

[0046] After electrochemical reduction, the structure of the reduced Bi-MOF-JH nanosheets was determined using high-resolution transmission electron microscopy, and the results are as follows: Figure 7 As shown, 7a is the reduced Bi. 0 The lattice fringes, the right image is a stress distribution diagram obtained through transformation, indicating that after electrochemical reduction, Bi... 0 Strong stress was observed in the nanosheet lattice.

[0047] Compared to original bismuth-based metal-organic frameworks, bismuth-based metal-organic frameworks with disordered coordination environments retain the same basic morphological characteristics such as size, shape, and specific surface area, but their coordination environments are altered. When used as catalysts for the electroreduction of carbon dioxide, they promote the electrochemical reduction of Bi... 3+ The reduction process of Bi elemental leads to the reduction of Bi. 0 The stress within the nanosheets significantly enhances the current density during the reaction over a wide voltage range, thereby improving the efficiency of CO2 reduction.

[0048] Example 2

[0049] In this embodiment, the Joule heating parameters in the preparation method of Bi-MOF-JH are: current 95A, heating time 5s, and other steps are the same as in Example 1.

[0050] Carbon dioxide reduction was performed using a gas diffusion electrode supported on Bi-MOF-JH nanosheets as described above. The electrolyte was 1M KOH, and the reference electrode was a saturated Ag / AgCl reference electrode. The Faradaic efficiency and local current density of the electrocatalytic conversion of carbon dioxide to formic acid were measured with an applied voltage range of -1.6V to -2.1V in 0.1V intervals. The results are shown in the table below.

[0051] Table 3

[0052] Faraday efficiency 73.59％ 91.83％ 92.45％ 85.83％ 88.3％ 86.49％

[0053] Example 3

[0054] In this embodiment, the Joule heating parameters for the preparation method of Bi-MOF-JH are: current 115A, heating time 5s, and other steps are the same as in Example 1.

[0055] Carbon dioxide reduction was performed using a gas diffusion electrode supported on Bi-MOF-JH nanosheets as described above. The electrolyte was 1M KOH, and the reference electrode was a saturated Ag / AgCl reference electrode. The Faradaic efficiency and local current density of the electrocatalytic conversion of carbon dioxide to formic acid were measured with an applied voltage range of -1.6V to -2.1V in 0.1V intervals. The results are shown in the table below.

[0056] Table 4

[0057] Faraday efficiency 89.93％ 92.45％ 92.41％ 89.68％ 85.36％ 76.72％

[0058] Example 4

[0059] In the preparation method of Bi-MOF-JH in this embodiment, 150 mg of bismuth nitrate pentahydrate and 900 mg of terephthalic acid were weighed. The temperature in the reaction vessel was 150 °C. The Joule heating parameters were set as follows: current 105 A and heating time 5 s. Other preparation methods were the same as in Example 1.

[0060] Carbon dioxide reduction was performed using the gas diffusion electrode supported on Bi-MOF-JH nanosheets described above, with 1M KOH as the electrolyte and a saturated Ag / AgCl reference electrode as the reference electrode. Compared to Example 1, the performance showed a lower Faradaic efficiency for formic acid at high potential, but higher than that of Examples 2 and 3.

[0061] Example 5

[0062] In the preparation method of Bi-MOF-JH in this embodiment, 150 mg of bismuth nitrate pentahydrate and 200 mg of terephthalic acid were weighed. The temperature in the reaction vessel was 115 °C. The Joule heating parameters were set as follows: current 100 A and heating time 6 s. Other preparation methods were the same as in Example 1.

[0063] Carbon dioxide reduction was performed using the gas diffusion electrode supported on Bi-MOF-JH nanosheets described above, with 1M KOH as the electrolyte and a saturated Ag / AgCl reference electrode as the reference electrode. Compared to Example 1, the performance showed a lower Faradaic efficiency for formic acid at high potential, but higher than that of Examples 2 and 3.

[0064] The gas diffusion electrodes supported on Bi-MOF-JH nanosheets prepared in Examples 4 and 5 exhibited higher Faraday efficiency and local current in the electrocatalytic conversion of carbon dioxide to formic acid than those supported on Bi-MOF nanosheets.

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. 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 preparing a bismuth-based metal-organic framework material with disordered coordination environment, characterized in that, The method includes the step of heating a bismuth-based metal-organic framework material using a Joule heating device; the current of the Joule heating device is set to 95-115A, the heating time is 4-6s, and the heating atmosphere is nitrogen; the ligand of the bismuth-based metal-organic framework material is a polycarboxylic acid organic ligand.

2. The method for preparing bismuth-based metal-organic framework materials with disordered coordination environment according to claim 1, characterized in that, The current of the Joule heating device is set to 105A, and the heating time is 5s.

3. The method for preparing bismuth-based metal-organic framework materials with disordered coordination environment according to claim 1 or 2, characterized in that, The bismuth-based metal-organic framework material was synthesized via a hydrothermal method.

4. The method for preparing bismuth-based metal-organic framework materials with disordered coordination environment according to claim 3, characterized in that, The preparation steps of the bismuth-based metal-organic framework material include: Bismuth salt and polycarboxylic acid organic ligand were added to a solvent and stirred to obtain a suspension; and The suspension was placed in a reaction vessel and heated to obtain the bismuth-based metal-organic framework material.

5. The method for preparing bismuth-based metal-organic framework materials with disordered coordination environment according to claim 4, characterized in that, The molar ratio of the bismuth salt to the polycarboxylic acid organic ligand is 1:2 to 20, and the concentration of the bismuth salt in the suspension is 0.003 mmol to 0.05 mmol / L.

6. The method for preparing bismuth-based metal-organic framework materials with disordered coordination environment according to claim 4, characterized in that, The bismuth salt is selected from at least one of bismuth nitrate pentahydrate and bismuth acetate, the polycarboxylic acid organic ligand is at least one of trimellitic acid, terephthalic acid or 3,5-pyridinedicarboxylic acid, and the solvent is methanol or a mixed solution of methanol and N,N-dimethylformamide.

7. The method for preparing bismuth-based metal-organic framework materials with disordered coordination environment according to any one of claims 4-6, characterized in that, The reaction temperature of the suspension in the reactor is 110~150℃, and the reaction time is 6~24 hours.

8. A bismuth-based metal-organic framework material with disordered coordination environment, characterized in that, It is prepared by the preparation method according to any one of claims 1-7.

9. The application of the bismuth-based metal-organic framework material with disordered coordination environment as described in claim 8 in the preparation of an electrocatalytic carbon dioxide reduction catalyst.

Images