Titanium-based metal organic framework material and membrane-free electro-catalysis chlorine preparation method thereof

Abstract

The invention discloses a titanium-based metal organic framework material and a membrane-free electro-catalysis chlorine preparation method thereof. The preparation method comprises the following steps: dissolving 2, 6-naphthalic acid and sodium hydroxide in water and ethanol, drying in air and staying overnight to synthesize 2, 6-naphthalene-2 sodium (2, 6-Na); the preparation method comprises the following steps: dispersing a titanium dioxide precursor into a mixed solution of N, N-dimethylformamide and methanol, adding titanium isopropoxide while stirring, and heating to synthesize a precursor (Ti-MOF-beam); ti-MOF is obtained after calcination in an argon atmosphere and can be used as an electrochemical oxychlorination reaction catalyst. A titanium-based metal organic framework material is made into a membrane-free electrolytic tank based on the Bernoulli principle, chlorine is promoted to directionally migrate to a gas chamber by utilizing the interface pressure difference between an electrode and electrolyte, the chlorine-hydrogen contact risk is avoided, and high-purity chlorine is separated; the Faraday efficiency reaches 88.8%-93.3% in the pH value range of 1-13, chlorine can be continuously produced for 200 hours, and the activity is equivalent to that of a membrane electrolytic tank and is remarkably superior to that of a traditional membrane-free system.

Description

Technical Field

[0001] This invention relates to a method for preparing titanium-based metal-organic framework materials, belonging to the field of nanomaterial synthesis. It also relates to a membrane-free electrolytic cell device designed using Bernoulli's principle, belonging to the field of electrocatalytic synthesis. Background Technology

[0002] Chlorine is a fundamental chemical widely used in wastewater treatment, disinfection, and pharmaceutical manufacturing. In industry, membrane-based chlor-alkali processes are commonly used to produce chlorine, separating chlorine from the anode, hydrogen from the cathode, and sodium hydroxide from the electrolyte using asbestos or ion-exchange membranes. However, the use of membranes complicates system configuration, requiring the maintenance of gas pressure balance between the anode and cathode regions during operation; otherwise, membrane degradation will be accelerated. Therefore, the design of membrane-free systems for the electrosynthesis of chlorine has attracted widespread attention.

[0003] Centuries ago, researchers worked on designing membrane-free chlor-alkali systems. Mercury batteries are essentially intermittent membrane-free systems composed of amalgam / sodium amalgam redox media, capable of separating chlorine, hydrogen, and sodium hydroxide. However, due to their intermittent nature, these membrane-free systems can only provide low chlorine yields.

[0004] To improve the selectivity of chlorine products, current research focuses on the design of novel catalysts, such as single-atom / molecular cluster catalysts, metals, and metal oxides. Among these, metal-organic frameworks (MOFs) are organic-inorganic hybrid materials with intramolecular pores, formed by the self-assembly of organic ligands and metal ions through coordination bonds. MOFs possess porous structures and large specific surface areas, enabling them to adsorb large amounts of hypochlorite intermediates and promote the mass production of chlorine. Furthermore, their organic ligands are easily modified, making them ideal catalysts for chlorination oxidation reactions. However, traditional reaction devices suffer from problems such as difficult product separation, low yield, and short lifespan. To address these issues, a membrane-free electrolyzer device is designed using Bernoulli's principle. By adjusting the gas flow rate to generate a pressure difference, chlorine is promoted to migrate away from hydrogen and the electrolyte, avoiding the risk of contact between chlorine and hydrogen, and simultaneously purifying the chlorine product, significantly improving catalytic performance. Summary of the Invention

[0005] The purpose of this invention is to design and implement a titanium-based metal-organic framework catalyst, providing a non-precious metal-based catalyst that can efficiently electrochemically catalyze the oxidation of sodium chloride to chlorine. At the same time, a membrane-free electrolytic cell device is designed using Bernoulli's principle to separate and purify the product to obtain high-purity chlorine.

[0006] The technical solution to achieve the purpose of this invention is as follows:

[0007] A method for preparing a titanium-based metal-organic framework material includes the following steps:

[0008] Step 1: Dissolve 2,6-naphthalenedicarboxylic acid and sodium hydroxide in a mixed solution of water and ethanol, and dry in air overnight to synthesize 2,6-naphthalene-2-sodium (2,6-Na).

[0009] Step 2: Disperse the 2,6-naphthalene-2-sodium obtained in Step 1 in a mixed solution of N,N-dimethylformamide and methanol, add isopropyl titanate under vigorous stirring, and react at high temperature to synthesize the titanium-based metal-organic framework material precursor (Ti-MOF-before).

[0010] Step 3: The precursor material obtained in Step 2 is calcined in an argon atmosphere for a period of time to obtain a titanium-based metal-organic framework (Ti-MOF) for the electrocatalytic synthesis of chlorine by chlorination. The obtained catalyst material, binder Nafion, and conductive agent carbon black are dispersed evenly in isopropanol to prepare a catalyst dispersion. The obtained dispersion is dropped onto a carbon substrate and allowed to dry naturally. The carbon substrate with the obtained catalyst material is then assembled with a polytetrafluoroethylene film to form a gas diffusion electrode.

[0011] Furthermore, in step one, the mass ratio of 2,6-naphthalenedicarboxylic acid to sodium hydroxide is 1:5 to 5:1, and the volume ratio of the mixed solution of water and ethanol is 1:5 to 5:1.

[0012] Furthermore, in step two, the mass ratio of 2,6-naphthalene-2-sodium to isopropyl titanate is 1:4 to 2:1, the volume ratio of the N,N-dimethylformamide and methanol mixed solution is 5:1 to 10:1, the heating temperature is 100 to 160 °C, and the time is 20 to 26 h.

[0013] Furthermore, in step three, the heating rate is 1–10 °C / min, the calcination temperature is 150–550 °C, and the time is 1–5 h. The mass ratio of catalyst material to conductive agent carbon black is 6:1–1:2, the amount of binder Nafion is 10–60 μL, and the amount of isopropanol is 0.5–4 mL. The catalyst material loading is 1–2.5 mg / cm³. 2 The carbon substrate area is 1~4 cm². 2 Dry at 10~40 ℃ for 4~12 h. The area of ​​the polytetrafluoroethylene film is consistent with that of the carbon substrate, and it covers the side of the carbon substrate without catalyst loading, and is bonded with conductive copper tape.

[0014] As a general technical concept, the present invention also utilizes Bernoulli's principle to design a membrane-free electrolytic cell device, including an anode and a cathode, wherein the catalyst material prepared by the preparation method is used as the anode and the iridium-plated titanium oxide is used as the cathode.

[0015] The above-mentioned membraneless electrolytic cell device is further improved by attaching an insulating tape with a coverage area of ​​about 0.5 square centimeters to the upper part of the gasket window, which effectively prevents the hydrogen gas generated at the cathode from coming into contact with the chlorine gas generated at the anode.

[0016] Compared with the prior art, the significant advantages of this invention are: (1) the catalyst synthesis process is realized under mild conditions; (2) the preparation method is environmentally friendly, green and pollution-free; (3) the titanium-based metal-organic framework material has advantages such as high surface area, which can significantly increase the number of active sites; (4) the design of the membrane-free electrolytic cell device can significantly increase the Faraday efficiency and yield of chlorine gas, and provide new ideas for other gas reaction devices. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the synthesis route of the titanium-based metal-organic framework material of the present invention.

[0018] Figure 2 These are material morphology characterization diagrams of Embodiment 1 of the present invention, wherein (a) is the overall morphology of Embodiment 1, (b) is a high-resolution TEM local image of Embodiment 1, (c) is a SEM local image of Embodiment 1, and (d) is an elemental distribution diagram of Embodiment 1.

[0019] Figure 3 These are material structure characterization diagrams of Example 1 of the present invention, wherein (a) is the X-ray diffraction pattern (XRD) of Example 1, (b) is the Fourier transform infrared spectrum (FT-IR) of Example 1, (c) is the XPS full spectrum image of Example 1, (d) is the 1s characteristic spectrum of element C in Example 1, (e) is the 2p characteristic spectrum of element Ti in Example 1, and (f) is the 1s characteristic spectrum of element Na in Example 1.

[0020] Figure 4 These are material morphology characterization images of Comparative Examples 1, 2 and 3 of the present invention, wherein (a) is the SEM image of Comparative Example 1, (b) is the SEM image of Comparative Example 2 and (c) is the SEM image of Comparative Example 3.

[0021] Figure 5 These are material structure characterization diagrams for Comparative Example 2 of the present invention, wherein (a) is the X-ray diffraction pattern (XRD) of Comparative Example 2, (b) is the Fourier transform infrared spectrum (FT-IR) of Comparative Example 2, (c) is the XPS full spectrum image of Comparative Example 2, (d) is the 1s characteristic spectrum of element C in Comparative Example 2, (e) is the 2p characteristic spectrum of element Ti in Comparative Example 2, and (f) is the 1s characteristic spectrum of element Na in Comparative Example 2.

[0022] Figure 6These are material structure characterization diagrams of Embodiment 1 and Comparative Example 2 of the present invention, wherein (a) is the XANES spectrum of Embodiment 1, (b) is the XANES spectrum of Comparative Example 2, (c) is the wavelet transform diagram of Embodiment 1, (d) is the EXAFS spectrum of Embodiment 1, (e) is the EXAFS spectrum of Comparative Example 2, (f) is the wavelet transform diagram of Comparative Example 2, (g) is the EXAFS fitted curve spectrum of Embodiment 1, (h) is the EXAFS fitted curve spectrum of Ti foil, and (i) is the EXAFS fitted curve spectrum of Comparative Example 2.

[0023] Figure 7 These are electrocatalytic chlorination performance test graphs of the materials from Examples 1, 2, and 3 of this invention under conditions of 5 M NaCl electrolyte and pH 13. (a) is a comparison graph of the Faradaic efficiency of the gaseous chlorine product; (b) is a comparison graph of the gaseous chlorine product yield; (c) is a comparison graph of material performance; (d) is an electrochemical impedance spectroscopy; and (e) is a graph of Example 2 under a current density of 100 mA / cm². 2 Stability test chart after 200 hours of continuous testing.

[0024] Figure 8 This is a comparison chart of the Faraday efficiency of the gaseous chlorine product of the materials in Examples 1 and 3 of the present invention under different flow rates and different carrier gas conditions.

[0025] Figure 9 These are electrocatalytic chlorination performance test graphs of the materials from Examples 1, 4, and 5 of this invention under conditions of 5 M NaCl electrolyte and pH values ​​of 1, 7, and 13. In the graphs, (a) is the Faradaic efficiency of the gaseous chlorine product, (b) is a comparison graph of the gaseous chlorine product yield, (c) is the LSV curve of the material, (d) is the Tafel slope of the material, and (e) is the material's performance under a current density of 100 mA / cm². 2 Stability test chart after 50 hours of continuous testing.

[0026] Figure 10 The graph shows the electrocatalytic chlorination performance test of the material in Example 6 of this invention under the conditions of 5 M NaCl electrolyte and pH 5. In the graph, (a) is the CV curve of the material, (b) is the Faraday efficiency and current density of the product gas phase chlorine, (c) is the LSV curve of the material, and (d) is the Tafel slope of the material.

[0027] Figure 11 The graph shows the electrocatalytic chlorination performance test of the material in Example 7 of this invention under the conditions of 5 M NaCl electrolyte and pH 9. In the graph, (a) is the CV curve of the material, (b) is the Faradaic efficiency and current density of the product gas phase chlorine, (c) is the LSV curve of the material, and (d) is the Tafel slope of the material.

[0028] Figure 12 The graph shows the electrocatalytic chlorination performance test of the material in Example 8 of this invention under the conditions of 5 M NaCl electrolyte and pH 13. In the graph, (a) is the CV curve of the material, (b) is the Faraday efficiency and current density of the product gas phase chlorine, (c) is the LSV curve of the material, and (d) is the Tafel slope of the material.

[0029] Figure 13 The graph shows the electrocatalytic chlorination performance test of the material in Example 9 of this invention under the conditions of 5 M NaCl electrolyte and pH 13. In the graph, (a) is the CV curve of the material, (b) is the Faraday efficiency and current density of the product gas phase chlorine, (c) is the LSV curve of the material, and (d) is the Tafel slope of the material.

[0030] Figure 14 The graph shows the electrocatalytic chlorination performance test of the material in Example 10 of this invention under the conditions of 5 M NaCl electrolyte and pH 13. In the graph, (a) is the CV curve of the material, (b) is the Faradaic efficiency and current density of the product gas phase chlorine, (c) is the LSV curve of the material, and (d) is the Tafel slope of the material.

[0031] Figure 15 The graph shows the electrocatalytic chlorination performance test of the material in Example 11 of this invention under the conditions of 5 M NaCl electrolyte and pH 13. In the graph, (a) is the CV curve of the material, (b) is the Faraday efficiency and current density of the product gas phase chlorine, (c) is the LSV curve of the material, and (d) is the Tafel slope of the material.

[0032] Figure 16 The graph shows the electrocatalytic chlorination performance test of the material of Comparative Example 1 of this invention in 5 M NaCl electrolyte at pH 13. In the graph, (a) is the CV curve of the material, (b) is the Faraday efficiency and current density of the product gas phase chlorine, (c) is the LSV curve of the material, and (d) is the Tafel slope of the material.

[0033] Figure 17 The graphs show the electrocatalytic chlorination performance of the material in Comparative Example 2 of this invention in 5 M NaCl electrolyte at pH 13. In the graphs, (a) is the CV curve of the material, (b) is the Faradaic efficiency and current density of the product gas phase chlorine, (c) is the LSV curve of the material, and (d) is the Tafel slope of the material.

[0034] Figure 18The graphs show the electrocatalytic chlorination performance of the material in Comparative Example 3 of this invention under conditions of 5 M NaCl electrolyte and pH 1, 7 and 13. In the graphs, (a) is the LSV curve of the material under pH 1, (b) is the Tafel slope of the material under pH 1, (c) is the Faraday efficiency of the gaseous chlorine product of the material under pH 1, 7 and 13, and (d) is the yield of the gaseous chlorine product of the material under pH 1, 7 and 13.

[0035] Figure 19 This is a structural diagram of the membraneless electrolytic cell device of the present invention, wherein: (a) is a membraneless electrolytic cell device for electrocatalytic chlorine oxidation reaction; (b) is an optical photograph of the membraneless electrolytic cell device, and potassium iodide is used to verify the generation of chlorine gas before and after the reaction.

[0036] Figure 20 This is an internal structural diagram of the membraneless electrolytic cell device of the present invention, wherein: (a) is an insulating tape with a coverage area of ​​about 0.5 cm that is attached to the upper part of the gasket window; (b) is a schematic diagram to prevent the hydrogen gas generated at the cathode from contacting the chlorine gas generated at the anode. Detailed Implementation

[0037] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0038] Example 1:

[0039] Step 1: Dissolve 5 g of 2,6-naphthalenedicarboxylic acid and 1.85 g of sodium hydroxide completely in a mixed solution of 300 mL of water and ethanol (volume ratio 1:1), and then dry in air overnight to obtain 2,6-naphthalene-2-sodium material 2,6-Na;

[0040] Step 2: Take 2.916 g of the sample obtained in Step 1, completely dissolve it in a mixed solution of 28 mL N,N-dimethylformamide and 3 mL methanol, and add 1.153 g of isopropyl titanate under vigorous stirring. Place it in an oven at 150 °C for 24 h to obtain the titanium-based metal-organic framework precursor material Ti-MOF-before.

[0041] Step 3: After washing and drying the obtained sample, place the sample from Step 2 into a tube furnace and calcine it at 450 °C for 3 hours under argon atmosphere and a heating rate of 5 °C / min. After cooling to room temperature, the titanium-based metal-organic framework catalyst material Ti-MOF is obtained. The titanium-based metal-organic framework catalyst material is then supported on a carbon substrate with a loading of 1.5 mg / cm³. 2The gas diffusion electrode formed serves as the anode, with a polytetrafluoroethylene film attached to its back. The gas flow rate through the gas diffusion electrode's rear gas chamber is 80 mL / min. An iridium-plated titanium oxide electrode serves as the counter electrode, and a silver chloride electrode serves as the reference electrode. This assembly forms a standard three-electrode, three-phase battery system, with the anode and cathode separated by a proton exchange membrane. A 5 M sodium chloride electrolyte with a pH of 13 is used.

[0042] Example 2:

[0043] Step 1: Dissolve 5 g of 2,6-naphthalenedicarboxylic acid and 1.85 g of sodium hydroxide completely in a mixed solution of 300 mL of water and ethanol (volume ratio 1:1), and then dry in air overnight to obtain 2,6-naphthalene-2-sodium material 2,6-Na;

[0044] Step 2: Take 2.916 g of the sample obtained in Step 1, completely dissolve it in a mixed solution of 28 mL N,N-dimethylformamide and 3 mL methanol, and add 1.153 g of isopropyl titanate under vigorous stirring. Place it in an oven at 150 °C for 24 h to obtain the titanium-based metal-organic framework precursor material Ti-MOF-before.

[0045] Step 3: After washing and drying the obtained sample, take out the sample from Step 2 and place it in a tube furnace. Under an argon atmosphere, heat at a rate of 5 °C / min and calcine at 450 °C for 3 hours. After cooling to room temperature, the titanium-based metal-organic framework catalyst material Ti-MOF is obtained. The titanium-based metal-organic framework catalyst material is then supported on a carbon substrate with a loading of 1.5 mg / cm³. 2 The gas diffusion electrode formed serves as the anode, with a polytetrafluoroethylene film attached to its back. The gas flow rate through the gas chamber behind the gas diffusion electrode is 80 mL / min. An iridium-plated titanium oxide electrode serves as the counter electrode, and a silver chloride electrode serves as the reference electrode. This assembly forms a standard three-electrode, three-phase battery system. No proton exchange membrane is used to separate the anode and cathode, and 5 M sodium chloride is used as the electrolyte at pH 13.

[0046] Example 3:

[0047] Step 1: Dissolve 5 g of 2,6-naphthalenedicarboxylic acid and 1.85 g of sodium hydroxide completely in a mixed solution of 300 mL of water and ethanol (volume ratio 1:1), and then dry in air overnight to obtain 2,6-naphthalene-2-sodium material 2,6-Na;

[0048] Step 2: Take 2.916 g of the sample obtained in Step 1, completely dissolve it in a mixed solution of 28 mL N,N-dimethylformamide and 3 mL methanol, and add 1.153 g of isopropyl titanate under vigorous stirring. Place it in an oven at 150 °C for 24 h to obtain the titanium-based metal-organic framework precursor material Ti-MOF-before.

[0049] Step 3: After washing and drying the obtained sample, place the sample from Step 2 into a tube furnace and calcine it at 450 °C for 3 hours under argon atmosphere and a heating rate of 5 °C / min. After cooling to room temperature, the titanium-based metal-organic framework catalyst material Ti-MOF is obtained. The titanium-based metal-organic framework catalyst material is then supported on a carbon substrate with a loading of 1.5 mg / cm³. 2 A gas diffusion electrode is formed as the anode, and a polytetrafluoroethylene film is attached to the back of the gas diffusion electrode. The gas flow rate through the gas chamber behind the gas diffusion electrode is 0 mL / min (simulating the absence of Bernoulli's principle). An iridium-plated titanium oxide electrode is used as the counter electrode, and a silver chloride electrode is used as the reference electrode. The system is assembled into a standard three-electrode three-phase battery system without using a proton exchange membrane to separate the anode and cathode, and uses 5 M sodium chloride as the electrolyte with a pH of 13.

[0050] Example 4:

[0051] Step 1: Dissolve 5 g of 2,6-naphthalenedicarboxylic acid and 5 g of sodium hydroxide completely in a mixed solution of 300 mL of water and ethanol (volume ratio 1:1), and then dry in air overnight to obtain 2,6-naphthalene-2-sodium material 2,6-Na;

[0052] Step 2: Take 2.916 g of the sample obtained in Step 1, completely dissolve it in a mixed solution of 28 mL N,N-dimethylformamide and 3 mL methanol, and add 1.153 g of isopropyl titanate under vigorous stirring. Place it in an oven at 150 °C for 24 h to obtain the titanium-based metal-organic framework precursor material Ti-MOF-before.

[0053] Step 3: After washing and drying the obtained sample, place the sample from Step 2 into a tube furnace and calcine it at 450 °C for 3 hours under argon atmosphere and a heating rate of 5 °C / min. After cooling to room temperature, the titanium-based metal-organic framework catalyst material Ti-MOF is obtained. The titanium-based metal-organic framework catalyst material is then supported on a carbon substrate with a loading of 1.5 mg / cm³. 2The gas diffusion electrode formed serves as the anode, with a polytetrafluoroethylene film attached to its back. The gas flow rate through the gas diffusion electrode's rear gas chamber is 80 mL / min. An iridium-plated titanium oxide electrode serves as the counter electrode, and a silver chloride electrode serves as the reference electrode. This assembly forms a standard three-electrode, three-phase battery system, with the anode and cathode separated by a proton exchange membrane. A 5 M sodium chloride electrolyte with a pH of 1 is used.

[0054] Example 5:

[0055] Step 1: Dissolve 5 g of 2,6-naphthalenedicarboxylic acid and 1.85 g of sodium hydroxide completely in a mixed solution of 300 mL of water and ethanol (volume ratio 1:1), and then dry in air overnight to obtain 2,6-naphthalene-2-sodium material 2,6-Na;

[0056] Step 2: Take 2.916 g of the sample obtained in Step 1, completely dissolve it in a mixed solution of 28 mL N,N-dimethylformamide and 3 mL methanol, and add 1.153 g of isopropyl titanate under vigorous stirring. Place it in an oven at 150 °C for 24 h to obtain the titanium-based metal-organic framework precursor material Ti-MOF-before.

[0057] Step 3: After washing and drying the obtained sample, place the sample from Step 2 into a tube furnace and calcine it at 450 °C for 3 hours under argon atmosphere and a heating rate of 5 °C / min. After cooling to room temperature, the titanium-based metal-organic framework catalyst material Ti-MOF is obtained. The titanium-based metal-organic framework catalyst material is then supported on a carbon substrate with a loading of 1.5 mg / cm³. 2 The gas diffusion electrode formed serves as the anode, with a polytetrafluoroethylene film attached to its back. The gas flow rate through the gas diffusion electrode's rear gas chamber is 80 mL / min. An iridium-plated titanium oxide electrode serves as the counter electrode, and a silver chloride electrode serves as the reference electrode. This assembly forms a standard three-electrode, three-phase battery system, with the anode and cathode separated by a proton exchange membrane. A 5 M sodium chloride electrolyte with a pH of 7 is used.

[0058] Example 6:

[0059] Step 1: Dissolve 5 g of 2,6-naphthalenedicarboxylic acid and 1.85 g of sodium hydroxide completely in a mixed solution of 300 mL of water and ethanol (volume ratio 1:1), and then dry in air overnight to obtain 2,6-naphthalene-2-sodium material 2,6-Na;

[0060] Step 2: Take 2.916 g of the sample obtained in Step 1, completely dissolve it in a mixed solution of 28 mL N,N-dimethylformamide and 3 mL methanol, and add 1.153 g of isopropyl titanate under vigorous stirring. Place it in an oven at 150 °C for 24 h to obtain the titanium-based metal-organic framework precursor material Ti-MOF-before.

[0061] Step 3: After washing and drying the obtained sample, place the sample from Step 2 into a tube furnace and calcine it at 450 °C for 3 hours under argon atmosphere at a heating rate of 5 °C / min. After cooling to room temperature, the titanium-based metal-organic framework catalyst material Ti-MOF is obtained. Step 4: Load the titanium-based metal-organic framework catalyst material onto a carbon substrate with a loading amount of 1.5 mg / cm³. 2 The gas diffusion electrode formed serves as the anode, with a polytetrafluoroethylene film attached to its back. The gas flow rate through the gas diffusion electrode's rear gas chamber is 80 mL / min. An iridium-plated titanium oxide electrode serves as the counter electrode, and a silver chloride electrode serves as the reference electrode. This assembly forms a standard three-electrode, three-phase battery system, with the anode and cathode separated by a proton exchange membrane. A 5M sodium chloride electrolyte with a pH of 5 is used.

[0062] Example 7:

[0063] Step 1: Dissolve 5 g of 2,6-naphthalenedicarboxylic acid and 1.85 g of sodium hydroxide completely in a mixed solution of 300 mL of water and ethanol (volume ratio 1:1), and then dry in air overnight to obtain 2,6-naphthalene-2-sodium material 2,6-Na;

[0064] Step 2: Take 2.916 g of the sample obtained in Step 1, completely dissolve it in a mixed solution of 28 mL N,N-dimethylformamide and 3 mL methanol, and add 1.153 g of isopropyl titanate under vigorous stirring. Place it in an oven at 150 °C for 24 h to obtain the titanium-based metal-organic framework precursor material Ti-MOF-before.

[0065] Step 3: After washing and drying the obtained sample, place the sample from Step 2 into a tube furnace and calcine it at 450 °C for 3 hours under argon atmosphere at a heating rate of 5 °C / min. After cooling to room temperature, the titanium-based metal-organic framework catalyst material Ti-MOF is obtained. Step 4: Load the titanium-based metal-organic framework catalyst material onto a carbon substrate with a loading amount of 1.5 mg / cm³. 2The gas diffusion electrode formed serves as the anode, with a polytetrafluoroethylene film attached to its back. The gas flow rate through the gas diffusion electrode's rear gas chamber is 80 mL / min. An iridium-plated titanium oxide electrode serves as the counter electrode, and a silver chloride electrode serves as the reference electrode. This assembly forms a standard three-electrode, three-phase battery system, with the anode and cathode separated by a proton exchange membrane. A 5M sodium chloride electrolyte with a pH of 9 is used.

[0066] Example 8:

[0067] Step 1: Dissolve 5 g of 2,6-naphthalenedicarboxylic acid and 1.85 g of sodium hydroxide completely in a mixed solution of 300 mL of water and ethanol (volume ratio 1:1), and then dry in air overnight to obtain 2,6-naphthalene-2-sodium material 2,6-Na;

[0068] Step 2: Take 2.916 g of the sample obtained in Step 1, completely dissolve it in a mixed solution of 28 mL N,N-dimethylformamide and 3 mL methanol, and add 1.153 g of isopropyl titanate under vigorous stirring. Place it in an oven at 150 °C for 24 h to obtain the titanium-based metal-organic framework precursor material Ti-MOF-before.

[0069] Step 3: After washing and drying the obtained sample, place the sample from Step 2 into a tube furnace and calcine it at 150 ℃ for 3 hours under argon atmosphere at a heating rate of 5 ℃ / min. After cooling to room temperature, the titanium-based metal-organic framework catalyst material (150 ℃) Ti-MOF-150 is obtained. The titanium-based metal-organic framework catalyst material is then supported on a carbon substrate at a loading of 1.5 mg / cm³. 2 The gas diffusion electrode formed serves as the anode, with a polytetrafluoroethylene film attached to its back. The gas flow rate through the gas diffusion electrode's rear gas chamber is 80 mL / min. An iridium-plated titanium oxide electrode serves as the counter electrode, and a silver chloride electrode serves as the reference electrode. This assembly forms a standard three-electrode, three-phase battery system, with the anode and cathode separated by a proton exchange membrane. A 5 M sodium chloride electrolyte with a pH of 13 is used.

[0070] Example 9:

[0071] Step 1: Dissolve 5 g of 2,6-naphthalenedicarboxylic acid and 1.85 g of sodium hydroxide completely in a mixed solution of 300 mL of water and ethanol (volume ratio 1:1), and then dry in air overnight to obtain 2,6-naphthalene-2-sodium material 2,6-Na;

[0072] Step 2: Take 2.916 g of the sample obtained in Step 1, completely dissolve it in a mixed solution of 28 mL N,N-dimethylformamide and 3 mL methanol, and add 1.153 g of isopropyl titanate under vigorous stirring. Place it in an oven at 150 °C for 24 h to obtain the titanium-based metal-organic framework precursor material Ti-MOF-before.

[0073] Step 3: After washing and drying the obtained sample, place the sample from Step 2 into a tube furnace and calcine it at 250 ℃ for 3 hours under argon atmosphere at a heating rate of 5 ℃ / min. After cooling to room temperature, the titanium-based metal-organic framework catalyst material (Ti-MOF-250) is obtained. The titanium-based metal-organic framework catalyst material is then supported on a carbon substrate at a loading of 1.5 mg / cm³. 2 The gas diffusion electrode formed serves as the anode, with a polytetrafluoroethylene film attached to its back. The gas flow rate through the gas diffusion electrode's rear gas chamber is 80 mL / min. An iridium-plated titanium oxide electrode serves as the counter electrode, and a silver chloride electrode serves as the reference electrode. This assembly forms a standard three-electrode, three-phase battery system, with the anode and cathode separated by a proton exchange membrane. A 5 M sodium chloride electrolyte with a pH of 13 is used.

[0074] Example 10:

[0075] Step 1: Dissolve 5 g of 2,6-naphthalenedicarboxylic acid and 1.85 g of sodium hydroxide completely in a mixed solution of 300 mL of water and ethanol (volume ratio 1:1), and then dry in air overnight to obtain 2,6-naphthalene-2-sodium material 2,6-Na;

[0076] Step 2: Take 2.916 g of the sample obtained in Step 1, completely dissolve it in a mixed solution of 28 mL N,N-dimethylformamide and 3 mL methanol, and add 1.153 g of isopropyl titanate under vigorous stirring. Place it in an oven at 150 °C for 24 h to obtain the titanium-based metal-organic framework precursor material Ti-MOF-before.

[0077] Step 3: After washing and drying the obtained sample, place the sample from Step 2 into a tube furnace and calcine it at 350 ℃ for 3 hours under argon atmosphere at a heating rate of 5 ℃ / min. After cooling to room temperature, the titanium-based metal-organic framework catalyst material (Ti-MOF-350) is obtained. The titanium-based metal-organic framework catalyst material is then supported on a carbon substrate at a loading of 1.5 mg / cm³. 2The gas diffusion electrode formed serves as the anode, with a polytetrafluoroethylene film attached to its back. The gas flow rate through the gas diffusion electrode's rear gas chamber is 80 mL / min. An iridium-plated titanium oxide electrode serves as the counter electrode, and a silver chloride electrode serves as the reference electrode. This assembly forms a standard three-electrode, three-phase battery system, with the anode and cathode separated by a proton exchange membrane. A 5 M sodium chloride electrolyte with a pH of 13 is used.

[0078] Example 11:

[0079] Step 1: Dissolve 5 g of 2,6-naphthalenedicarboxylic acid and 1.85 g of sodium hydroxide completely in a mixed solution of 300 mL of water and ethanol (volume ratio 1:1), and then dry in air overnight to obtain 2,6-naphthalene-2-sodium material 2,6-Na;

[0080] Step 2: Take 2.916 g of the sample obtained in Step 1, completely dissolve it in a mixed solution of 28 mL N,N-dimethylformamide and 3 mL methanol, and add 1.153 g of isopropyl titanate under vigorous stirring. Place it in an oven at 150 °C for 24 h to obtain the titanium-based metal-organic framework precursor material Ti-MOF-before.

[0081] Step 3: After washing and drying the obtained sample, place the sample from Step 2 into a tube furnace and calcine it at 550 ℃ for 3 hours under argon atmosphere and a heating rate of 5 ℃ / min. After cooling to room temperature, the titanium-based metal-organic framework catalyst material (550 ℃) Ti-MOF-5550 is obtained. The titanium-based metal-organic framework catalyst material is then supported on a carbon substrate at a loading of 1.5 mg / cm³. 2 The gas diffusion electrode formed serves as the anode, with a polytetrafluoroethylene film attached to its back. The gas flow rate through the gas diffusion electrode's rear gas chamber is 80 mL / min. An iridium-plated titanium oxide electrode serves as the counter electrode, and a silver chloride electrode serves as the reference electrode. This assembly forms a standard three-electrode, three-phase battery system, with the anode and cathode separated by a proton exchange membrane. A 5 M sodium chloride electrolyte with a pH of 13 is used.

[0082] Comparative Example 1:

[0083] 5 g of 2,6-naphthalenedicarboxylic acid and 1.85 g of sodium hydroxide were completely dissolved in a mixed solution of 300 mL of water and ethanol (volume ratio 1:1), and then dried in air overnight to obtain 2,6-naphthalene-2-sodium material 2,6-Na.

[0084] Comparative Example 2:

[0085] Step 1: Dissolve 5 g of 2,6-naphthalenedicarboxylic acid and 1.85 g of sodium hydroxide completely in a mixed solution of 300 mL of water and ethanol (volume ratio 1:1), and then dry in air overnight to obtain 2,6-naphthalene-2-sodium material 2,6-Na;

[0086] Step 2: Take 2.916 g of the sample obtained in Step 1, completely dissolve it in a mixed solution of 28 mL N,N-dimethylformamide and 3 mL methanol, and add 1.153 g of isopropyl titanate under vigorous stirring. Place it in an oven at 150 °C for 24 h to obtain the titanium-based metal-organic framework precursor material Ti-MOF-before.

[0087] Comparative Example 3:

[0088] Commercial purchase of ruthenium oxide-plated titanium oxide plates

[0089] The results of the present invention will be further explained with reference to the accompanying drawings.

[0090] Figure 1 The diagram shown is a schematic diagram of the synthesis of titanium-based metal-organic framework materials in this invention.

[0091] TEM images, SEM images, and elemental distribution maps of the material in Example 1 (Ti-MOF) are shown below. Figure 2 As shown in (ad), the material is composed of nanosheet structures, with titanium, oxygen, carbon, and sodium as its main components. Figure 2 As shown in (b), the high-resolution TEM image of Ti-MOF shows that the crystallinity of the material is very clear, with an adjacent lattice spacing of 0.2 nm.

[0092] Figure 3 (a) The X-ray diffraction (XRD) spectrum of the material of Example 1 (Ti-MOF) is clearly shown. The spectrum contains a series of characteristic peaks that correspond to the main crystal plane (2 1 0) of the metal-organic framework structure. Figure 3 (b) shows the Fourier transform infrared (FT-IR) spectrum of the Ti-MOF material, which displays the characteristic vibrations of the naphthalene ring of the organic ligand. Figure 3 (cf) shows the X-ray photoelectron spectrum (XPS) of the Ti-MOF material, proving that the main components of the material are titanium, oxygen, carbon and sodium.

[0093] To further determine the effects of hydrothermal and calcination methods on the material morphology, SEM images of Comparative Example 1 (2,6-Na) and Comparative Example 2 (Ti-MOF-before) were observed. Figure 4(a) and (b)). 2,6-Na exhibits a layered structure, while Ti-MOF-before exhibits a nanosheet structure, similar in morphology to the material in Example 1 (Ti-MOF), demonstrating that high-temperature calcination does not change the morphology of the material.

[0094] By observing the structural information of the material in Comparative Example 2 (Ti-MOF-before), it can be seen that the Ti-MOF-before material and the material in Example 1 (Ti-MOF) have similar crystal structures. Figure 5 (a)), and the FT-IR plots both show the characteristic vibrations of the naphthalene ring ( Figure 5 (b) Observation of the XPS spectrum shows that the materials are composed of four elements: titanium, oxygen, carbon, and sodium. Figure 5 (cf) proves that calcination does not damage the internal structural features of the material.

[0095] Furthermore, to gain a deeper understanding of the coordination environment within the material, the synchrotron radiation X-ray absorbing near-edge structure (XANES) and extended X-ray absorbing fine structure (EXAFS) of Example 1 (Ti-MOF) and Comparative Example 2 (Ti-MOF-before) were measured. Figure 6 (a) shows that the absorption edge energy of the Ti-MOF material exceeds that of the titanium foil, and the titanium has a higher valence state, indicating the successful coordination of the organic ligand. Figure 6 (d) shows that the titanium foil has only titanium-titanium bonds, while Ti-MOF exhibits two characteristic peaks: titanium-oxygen bonds and titanium-titanium bonds. Therefore, the titanium-titanium bond coordination number of the titanium foil is 6, while the titanium-titanium bond coordination number of the titanium-based metal-organic framework is 4.165, and the titanium-oxygen bond coordination number is 3.183. This result is in excellent agreement with the wavelet transform image, showing an intensity related to titanium-oxygen scattering, which also verifies the strong coordination between titanium and oxygen.

[0096] To better investigate the impact of membrane-free electrolytic cell devices on the electrocatalytic chlorination performance of materials, the production capacity of Ti-MOF materials in generating gaseous chlorine in both membrane- and membrane-free electrolytic cell devices was further tested. Figure 7 (ac) It was found that using 5 M sodium chloride at pH 13 as the electrolyte, at a potential of 1.8 V (vs. Ag / AgCl), the Faradaic efficiency of Ti-MOF material in producing gaseous chlorine during electrolysis was 80.5%, which is 15.66 times that of DSA, and the yield is 2.6 times that of DSA. By comparing the performance of membrane-based and membrane-free electrolytic cells, it was found that the Faradaic efficiency and yield of gaseous chlorine were almost unchanged. Figure 7 (e) shows the long-term stability test experiment of the membrane-free electrolyzer device, with the Ti-MOF material at 100 mA cm⁻¹. -2At the given current density, the potential fluctuations were minimal over 200 hours. The bar chart represents the overall Faraday efficiency of chlorine, which can be divided into gaseous chlorine (blue) and dissolved chlorine (brown). Throughout the 200 hours, the overall Faraday efficiency of chlorine remained stable, with almost no detectable dissolved chlorine.

[0097] Furthermore, the Faraday efficiency of gaseous chlorine is closely related to the air velocity. For example... Figure 8 As shown, for Ti-MOF materials, the Faraday efficiency of gaseous chlorine increases with increasing air velocity, reaching 17.6% at 0 mL / min (yield of 0.228 mmol / h / cm). 2 At a flow rate of 10 mL / min, the yield was 32.25% (yield of 0.48 mmol / h / cm). 2 At a flow rate of 20 mL / min, the yield was 45.12% (yield of 0.6 mmol / h / cm). 2 At a flow rate of 30 mL / min, the yield was 75.57% (yield of 0.978 mmol / h / cm). 2 This phenomenon can be explained by Bernoulli's principle: low-velocity gas flow can only generate very small pressures (0–7.08 Pa), making it difficult to remove the generated chlorine gas at the three-phase boundary. Above 30 mL / min, within the range of 40–80 mL / min and moderate pressure (15.9–113.4 Pa), the farad efficiency of gas-phase chlorine reaches its maximum (75.8%–82.6%, yield 1.02–1.08 mmol / h / cm³). 2 In addition to airflow, comparative experiments were also conducted under the same conditions using carbon dioxide flow and air. The results showed that the chlorine farad efficiency of carbon dioxide flow was comparable to that of air flow, thus proving the feasibility of the membrane-free electrolysis cell device principle.

[0098] To investigate the electrocatalytic chlorination performance of Ti-MOF materials under different acid-base conditions, 5 M sodium chloride with a pH range of 1–13 was used as the electrolyte. Figure 9 As shown, at a potential of 1.8 V (vs. Ag / AgCl), the gaseous chlorine yields of the Ti-MOF material at pH 1, 7, and 13 were 93.3, 94, and 88.8 mmol / h / cm³, respectively. 2 The gas-phase chlorine Faraday efficiencies were 1.68%, 0.93%, and 0.78%, respectively. The stability of the Ti-MOF material under different acid and alkaline conditions was also investigated. Figure 9 As shown in (e), after 50 h of stability testing, the performance of the Ti-MOF material showed almost no degradation. Figure 10 and 11The figure shows the electrochemical performance of Ti-MOF materials in producing gaseous chlorine at pH 5 and 9, both exhibiting excellent electrocatalytic chlorination activity. Based on the above data, it can be seen that gaseous chlorine has been efficiently produced and purified under a wide range of acidity and alkalinity conditions.

[0099] like Figure 12-15 As shown, the electrochemical chlorination performance of Examples 8 (Ti-MOF-150), 9 (Ti-MOF-250), 10 (Ti-MOF-350), and 11 (Ti-MOF-550) was investigated to explore the effect of calcination temperature on the material properties. It was found that the gas-phase chlorine Faradaic efficiency of the titanium-based metal-organic framework increased with increasing calcination temperature. Using 5 M sodium chloride at pH 13 as the electrolyte, at a potential of 1.8 V (vs. Ag / AgCl), the Faradaic efficiency of the material increased from 38.6% at 150 °C to a maximum value (88.8%) at 450 °C, and finally decreased to 77.7% at 550 °C.

[0100] like Figure 16 The electrochemical performance data of the 2,6-Na material in Comparative Example 1 are shown. Using 5 M sodium chloride at pH 13 as the electrolyte, the test current density was found to be significantly lower than that of the electrodes in the examples. At a potential of 1.8 V (vs. Ag / AgCl), the Faraday efficiency was only 55.4%, and the Tafel slope was 463 mV dec. -1 .

[0101] like Figure 17 The figures show the electrochemical performance data of the Ti-MOF-before material in Comparative Example 2. Using 5M sodium chloride at pH 13 as the electrolyte, the test current density was found to be significantly lower than that of the electrodes in the examples. At a potential of 1.8 V (vs. Ag / AgCl), the Faraday efficiency was only 67%, and the Tafel slope was 274 mV dec. -1 .

[0102] like Figure 18 The electrochemical performance data of the DSA material in Comparative Example 3 are shown. It was found that at a potential of 1.8 V (vs. Ag / AgCl), the gas-phase chlorine Faradaic efficiencies at pH 1, 7, and 13 were 46.6%, 4.3%, and 0%, respectively. This reveals the influence of pH on the catalyst, leading to a performance degradation as high as 46.6%. Similarly, at pH 1, 7, and 13, the gas-phase chlorine yields were 3, 0.21, and 0 mmol / h / cm³, respectively. 2It can be seen that chlorine gas prefers to be produced in acidic environments, while it is easily hydrolyzed into hypochlorous acid and hypochlorite ions under neutral and alkaline conditions. Therefore, this indirectly confirms the excellent performance of the Ti-MOF material in Example 1 in producing gaseous chlorine gas under conditions with universal acidity and alkalinity.

[0103] Figure 19 and 20 The diagram shows a membraneless electrolytic cell device of the present invention. The catalyst material is loaded on the hydrophobic side of the carbon substrate, and polytetrafluoroethylene (PTFE) covers the side without the catalyst material to form a gas diffusion electrode, which is assembled into the electrolytic cell to become the anode. No cation membrane is used to separate the cathode and the anode. Figure 19 (b) shows the generation of chlorine gas before and after the reaction, verified by potassium iodide. Figure 20 (a) and (b) are schematic diagrams showing the insulating tape applied to the upper part of the gasket window and the measures taken to prevent the hydrogen gas generated at the cathode from coming into contact with the chlorine gas generated at the anode.

[0104] Chlorine has wide applications in industry, mainly produced through the chlor-alkali industry. However, the chlor-alkali industry faces problems of high cost and environmental pollution. The precious metal anode materials used in the chlor-alkali industry are expensive, and the diaphragm used in the electrolysis process increases costs. Chlorine gas produced during electrolysis is prone to leakage, causing health risks and environmental pollution, which is detrimental to the further application of chlorine. Therefore, a safe, inexpensive, and convenient strategy for producing and storing chlorine is needed. Inspired by the above phenomena, this application innovatively synthesizes a titanium-based metal-organic framework (Ti-MOF) material through a hydrothermal method and calcination. This improves the crystallinity of the material, resulting in good chlorine oxidation activity and long-term cycling stability, which can promote the electrocatalytic chlorine oxidation reaction to synthesize high-purity chlorine. In Example 1, the Ti-MOF sample with a heating rate of 5 °C / min and calcination at 450 °C for 3 h was the optimal sample. Furthermore, this invention utilizes Bernoulli's principle to design a membrane-free electrolytic cell device, which, after testing, showed excellent performance. The specific application of Bernoulli's principle is manifested in controlling the flow rate of the carrier gas; in this application, a flow rate of 80 mL / min is the optimal carrier gas flow rate. Theory and experiments show that: (1) Titanium-based metal-organic framework materials have advantages such as high surface area, which significantly increases the number of active sites; (2) The Bernoulli principle can effectively improve the chlorine precipitation reaction activity of catalyst materials in neutral and alkaline sodium chloride solutions; (3) Membrane-free electrolytic cells have the same excellent performance as membrane-based electrolytic cells, and reduce the cost of the reaction.

Claims

1. A method for preparing a titanium-based metal-organic framework material, characterized in that, Includes the following steps: Step 1: Dissolve 2,6-naphthalenedicarboxylic acid and sodium hydroxide in a mixed solution of water and ethanol, and dry in air overnight to synthesize sodium 2,6-naphthalene-2; Step 2: Disperse the 2,6-naphthalene-2-sodium from Step 1 in a mixed solution of N,N-dimethylformamide and methanol, add isopropyl titanate under vigorous stirring, and react at high temperature to synthesize the precursor of titanium-based metal-organic framework material. Step 3: Under an argon atmosphere, the titanium-based metal-organic framework precursor from Step 2 is treated by high-temperature calcination to form a titanium-based metal-organic framework material.

2. The method for preparing the titanium-based metal-organic framework material as described in claim 1, characterized in that, In step one, the mass ratio of 2,6-naphthalenedicarboxylic acid to sodium hydroxide is 1:5 to 5:1, and the volume ratio of the mixed solution of water and ethanol is 1:5 to 5:

1.

3. The method for preparing the titanium-based metal-organic framework material as described in claim 1, characterized in that, In step two, the mass ratio of 2,6-naphthalene-2-sodium to isopropyl titanate is 1:4 to 2:1, and the volume ratio of the N,N-dimethylformamide and methanol mixed solution is 5:1 to 10:

1.

4. The method for preparing the titanium-based metal-organic framework material as described in claim 1, characterized in that, In step two, the heating temperature is 100~160 ℃ and the time is 20~26 h.

5. The method for preparing the titanium-based metal-organic framework material as described in claim 1, characterized in that, In step three, the atmosphere is argon, the heating rate is 1~10 ℃ / min, the calcination temperature is 150~550 ℃, and the time is 1~5 h.

6. A titanium-based metal-organic framework material prepared according to any one of claims 1-5.

7. An application of the titanium-based metal-organic framework material as described in claim 6, characterized in that, This material was fabricated into electrodes for use in electrochemical chlorination reactions.

8. A membrane-free electrolytic flow cell apparatus, comprising an anode, a cathode, and a reference electrode in the same chamber, wherein the back side of the anode is a gas chamber, characterized in that, The material described in claim 6 is uniformly coated onto a gas diffusion electrode and used as an anode, with a loading of 1~2.5 mg / cm³. 2 A polytetrafluoroethylene film is attached to the back of the gas diffusion electrode to prevent liquid from penetrating into the gas chamber. Iridium-plated titanium oxide is used as the cathode, and an Ag / AgCl electrode is used as the reference electrode.

9. The membrane-free electrolytic cell apparatus as described in claim 8, characterized in that, One side of the anode catalyst material is a sodium chloride electrolyte, and the other side is a high-velocity carrier gas in the gas chamber, with a carrier gas flow rate of 0~80 mL / min.

10. The membrane-free electrolytic cell apparatus as described in claim 8, characterized in that, The pH of sodium chloride electrolyte is between 1 and 13, and the electrolyte flow rate is 5 to 10 mL / min. It flows into the entire chamber from the bottom of the anode chamber and flows out from the top of the cathode chamber.

Images