A bidentate ligand supported covalent organic framework hydrogen evolution catalyst, and a preparation method and application thereof

Abstract

This invention discloses a bidentate ligand-supported covalent organic framework hydrogen evolution catalyst, its preparation method, and its application. 1,3,5-tricarboxymethyl phloroglucinol and o-phenylenediamine are added to organic solvent I and mixed thoroughly. After degassing, an acid catalyst is added to initiate the reaction. After the reaction, the resulting filter solid is washed with organic solvent II and dried to obtain a covalent organic framework. This covalent organic framework is then added to organic solvent I and mixed thoroughly. After degassing, an acid catalyst is added to initiate the reaction. After the reaction, the resulting filter solid is washed with organic solvent II and dried to obtain a metal-doped covalent organic framework. This metal-doped covalent organic framework is then added to organic solvent I and mixed thoroughly. After degassing, an acid catalyst is added to initiate the reaction. After the reaction, the resulting filter solid is washed with organic solvent II and dried, yielding the desired bidentate ligand-supported covalent organic framework hydrogen evolution catalyst. This invention features a simple preparation method, a short synthesis cycle, low preparation cost, and is very environmentally friendly.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen evolution electrocatalyst technology, specifically relating to a bidentate ligand-supported covalent organic framework hydrogen evolution catalyst, its preparation method, and its application. Background Technology

[0002] Hydrogen energy, with its green, high calorific value, and low energy consumption, holds the promise of replacing fossil fuels. Water electrolysis for hydrogen production, currently the most important green hydrogen production method, has attracted significant attention due to its low energy consumption, low greenhouse gas emissions, high hydrogen purity, and low impurity content. Initial research on catalysts for water electrolysis for hydrogen production focused on precious metals. While these catalysts exhibit high electrocatalytic activity, their scarcity and high cost have hindered large-scale application. Therefore, developing low-cost, high-electrocatalytic-activity, and stable non-precious metal catalysts has become a crucial and popular research area.

[0003] Covalent organic frameworks (COFs) are assembled by connecting organic components through strong covalent bonds, enabling them to exhibit excellent chemical stability even under harsh electrochemical conditions. Due to their modular nature, the pore structure and functional groups of COFs can be precisely controlled according to network chemistry. Therefore, COFs have become potential catalysts for the electrocatalytic evolution of hydrogen. In recent years, an increasing number of researchers have been working on the preparation of electrochemical catalysts using COFs. For example, Xingying Liu et al. synthesized an electrocatalyst, Co-Salen COF, using 1,3,5-TRIS (3'-aldehyde-4'-hydroxybenzene)benzene, ethylenediamine, and cobalt salt. EDA At 10 mA cm -2 The overpotential shown at the current density is 320 mV (Advanced Science, 2022, 9: 22). However, the above electrocatalytic performance still cannot meet the needs of scientific and technological applications. Therefore, how to develop highly efficient electrocatalytic hydrogen evolution performance based on covalent organic frameworks is an important issue.

[0004] By replacing the adjacent layer structure formed by π-π stacking with a spatially extended layer driven by coordination bonds, bidentate ligands separate the stacked covalent organic framework layers with pillars, exposing all catalytic sites accessible to the reaction, thereby improving the electrocatalytic hydrogen evolution activity. Therefore, for research on electrocatalytic hydrogen evolution, it is of great significance to improve point catalytic activity by opening the interlayer spacing with bidentate ligands, exposing more active sites. Summary of the Invention

[0005] In view of the problems existing in the prior art, the purpose of this invention is to provide a bidentate ligand-supported covalent organic framework hydrogen evolution catalyst, its preparation method and application. The material can replace the adjacent layer structure formed by π-π stacking with a spatially extended layer driven by coordination bonds through bidentate ligand support, thereby exposing more active sites and improving electrocatalytic performance. The resulting material has strong electrocatalytic hydrogen production performance.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] This invention proposes a method for preparing a bidentate ligand-supported covalent organic framework hydrogen evolution catalyst, comprising the following steps:

[0008] 1) Preparation of covalent organic framework: 1,3,5-tricarboxymethyl phloroglucinol and o-phenylenediamine were added to organic solvent I and mixed evenly, then degassed. After degassed, an acid catalyst was added to carry out the reaction. After the reaction was completed, the material was filtered. The obtained filter solid was washed with organic solvent II and dried to obtain the covalent organic framework to be prepared.

[0009] 2) Preparation of metal-doped covalent organic framework: The covalent organic framework obtained in step 1) and the metal salt are added to organic solvent I and mixed evenly. Then the mixture is degassed. After degassed, an acid catalyst is added to carry out the reaction. After the reaction is completed, the material after the reaction is filtered. The filter solid is washed with organic solvent II and dried to obtain the metal-doped covalent organic framework to be prepared.

[0010] 3) Preparation of bidentate ligand-supported covalent organic framework hydrogen evolution catalyst: The metal-doped covalent organic framework and bidentate ligand obtained in step 2) are added to organic solvent I and mixed evenly, then degassed. After degassed, an acid catalyst is added to carry out the reaction. After the reaction is completed, the reacted material is filtered, and the obtained filter solid is washed with organic solvent II and dried to obtain the bidentate ligand-supported covalent organic framework hydrogen evolution catalyst to be prepared.

[0011] Further, in step 1), the molar ratio of 1,3,5-tricarboxymethyl phloroglucinol to o-phenylenediamine is 1:1 to 3; the molar ratio of 1,3,5-tricarboxymethyl phloroglucinol to acid catalyst is 1:2 to 4; the reaction temperature in step 1) is 100 to 150 °C, and the reaction time is 48 to 96 h.

[0012] Further, in step 2), the molar ratio of the covalent organic framework obtained in step 1) to the metal salt is 1:0.5 ~ 1.5; the molar ratio of the covalent organic framework obtained in step 1) to the acid catalyst is 1:2 ~ 4; the reaction temperature in step 2) is 100 ~ 150 ℃, and the reaction time is 12 ~ 36 h.

[0013] Further, in step 3), the molar ratio of the metal-doped covalent organic framework obtained in step 2) to the bidentate ligand is 1:0.5 ~ 1.5; the molar ratio of the metal-doped covalent organic framework obtained in step 2) to the acid catalyst is 1:2 ~ 4; the reaction temperature in step 2) is 100 ~ 150 ℃, and the reaction time is 12 ~ 36 h.

[0014] Further, the organic solvent I is any two or three of the following: mesitylene, N,N-dimethylformamide, dioxane, o-dichlorobenzene, and n-butanol;

[0015] Organic solvent II is any three or four of N,N-dimethylformamide, methanol, ethanol, acetone, tetrahydrofuran, and deionized water;

[0016] The acid catalyst is glacial acetic acid, trifluoroacetic acid, trifluoromethanesulfonic acid, or sulfuric acid;

[0017] The bidentate ligand is triethylenediamine or 4,4'-bipyridine.

[0018] Furthermore, the mass percentage concentration of the sulfuric acid is 30% to 40% or 95% to 98%.

[0019] This invention proposes a bidentate ligand-supported covalent organic framework hydrogen evolution catalyst prepared by the method described above.

[0020] This invention also proposes the application of the aforementioned bidentate ligand-supported covalent organic framework hydrogen evolution catalyst as an electrocatalyst in the electrocatalytic splitting of water to produce hydrogen.

[0021] Furthermore, it includes the following steps:

[0022] 1) Polish the L-shaped glassy carbon electrode with polishing powder, wash and dry it to obtain an L-shaped glassy carbon electrode with contaminants removed and physical defects eliminated;

[0023] 2) The bidentate ligand-supported covalent organic framework hydrogen evolution catalyst was thoroughly ground in an agate mortar, and then the bidentate ligand-supported covalent organic framework hydrogen evolution catalyst, binder, anhydrous ethanol and water were ultrasonically mixed evenly according to the mass ratio to obtain ink;

[0024] 3) The ink obtained in step 2) is evenly dropped onto the L-shaped glassy carbon electrode obtained in step 1) and dried under infrared lamp irradiation to obtain an electrocatalytic water splitting and hydrogen evolution electrode.

[0025] Furthermore, in step 1), the L-shaped glassy carbon electrode is polished sequentially with polishing powders of 1.0 µm, 0.3 µm, and 0.05 µm in size;

[0026] In step 2), the mass ratio of the bidentate ligand-supported covalent organic framework hydrogen evolution catalyst, binder, anhydrous ethanol, and water is (1~5):0.01:100:100; the binder in step 2) is naphthol.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] 1) Compared with other hydrogen evolution catalysts, the bidentate ligand-supported covalent organic framework hydrogen evolution catalyst of the present invention replaces the adjacent layer structure formed by π-π stacking with a spatial extension layer driven by coordination bonds, so that the stacked covalent organic framework layers are separated by bidentate ligand columns, exposing all catalytic sites that the reaction can reach, which significantly improves the electrocatalytic hydrogen evolution.

[0029] 2) The bidentate ligand-supported covalent organic framework hydrogen evolution catalyst of this invention operates at 10 mA cm⁻¹ -2 The overpotential can be as low as 145.2 mV, and the Tafel slope is 46.4 mV dec. -1 It exhibits high hydrogen evolution catalytic efficiency;

[0030] 3) The preparation process of the bidentate ligand-supported covalent organic framework hydrogen evolution catalyst of the present invention is simple, the reaction equipment is simple, the production cost is low and the safety is high, and the market prospects are broad. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the synthesis process of the covalent organic framework material DABCO-Co-TpDB of the present invention;

[0032] Figure 2 This is the structural formula of Equation I;

[0033] Figure 3 The X-ray diffraction pattern of the covalent organic framework material DABCO-Co-TpDB of this invention;

[0034] Figure 4 This is a scanning electron microscope (SEM) image of the covalent organic framework material DABCO-Co-TpDB of this invention.

[0035] Figure 5 The dispersive mapping energy spectrum of the covalent organic framework material DABCO-Co-TpDB of this invention;

[0036] Figure 6 Transmission electron microscopy images and pore structure analysis of the covalent organic framework material DABCO-Co-TpDB of this invention; Figure 6 (a) is a transmission electron microscope image of DABCO-Co-TpDB; Figure 6 (b) is Figure 6(a) is used to show the linear plot of the fast Fourier transform of the pores (0.44 nm).

[0037] Figure 7 Transmission electron microscopy images and pore structure analysis of the covalent organic framework material DABCO-Co-TpDB of this invention (Part II); Figure 7 (a) is a transmission electron microscope image of DABCO-Co-TpDB; Figure 7 (b) is Figure 7 (a) is used to show the fast Fourier transform linear plot of the pores (0.57 nm).

[0038] Figure 8 Comparison of Fourier transform infrared spectra of the covalent organic framework material DABCO-Co-TpDB;

[0039] Figure 9 Linear scan curve of the electrocatalytic water splitting and hydrogen evolution electrode of covalent organic framework material DABCO-Co-TpDB;

[0040] Figure 10 Tafel curve of the electrocatalytic hydrogen evolution electrode for water splitting of covalent organic framework material DABCO-Co-TpDB. Detailed Implementation

[0041] The present invention will be further described below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited to the scope described.

[0042] Example 1

[0043] 1. Synthesis of DABCO-Co-TpDB

[0044] 1) Add 0.1 mmol of 1,3,5-triformylphloroglucinol (Tp), 0.15 mmol of o-phenylenediamine (ODP), 0.5 mL of acetic acid, 2 mL of mesitylene, and 2 mL of dioxane to an ampoule. Sonicate the mixture for 30 minutes, then place the ampoule tubes in liquid nitrogen and repeat the freeze-de-thaw cycle three times. Place the ampoule tubes in an oven at 120°C for 72 hours at room temperature. After cooling to room temperature, centrifuge the precipitate and wash repeatedly with N,N-dimethylformamide, tetrahydrofuran, ethanol, and water until the supernatant is clear. Then dry the mixture overnight in a vacuum oven at 80°C to obtain TpDB.

[0045] 2) The obtained TpDB (0.1 mmol), cobalt acetate (0.15 mmol), 0.5 mL acetic acid, 2 mL mesitylene, and 2 mL dioxane were added to an ampoule. The mixture was sonicated for 30 minutes, and then the ampoule tubes were placed in liquid nitrogen and subjected to a freeze-vacuum-thaw cycle three times. The ampoule tubes were then placed in an oven at 120 °C for 24 hours at room temperature. After cooling to room temperature, the precipitate was centrifuged and washed repeatedly with N,N-dimethylformamide, tetrahydrofuran, ethanol, and water until the supernatant was clear. The mixture was then dried overnight in a vacuum oven at 80 °C to obtain Co-TpDB.

[0046] 3) Finally, the obtained Co-TpDB (0.1 mmol), triethylenediamine (0.15 mmol), 0.5 mL acetic acid, 2 mL mesitylene, and 2 mL dioxane were added to ampoules. The mixture was sonicated for 30 minutes, and then the ampoule tubes were placed in liquid nitrogen and subjected to a freeze-vacuum-thaw cycle three times. The ampoule tubes were then placed in an oven at 120°C for 24 hours at room temperature. After cooling to room temperature, the precipitate was centrifuged and washed repeatedly with N,N-dimethylformamide, tetrahydrofuran, ethanol, and water until the supernatant was clear. The mixture was then dried overnight in a vacuum oven at 80°C to obtain DABCO-Co-TpDB.

[0047] 2. Material Characterization:

[0048] Figure 1 The Chinese formula shown is the structural formula of DABCO-Co-TpDB.

[0049] Figure 2 This is the structural formula for Equation I.

[0050] Figure 3 The XRD pattern of the prepared DABCO-Co-TpDB is compared with the simulation, which proves that DABCO-Co-TpDB was successfully synthesized and maintains a good crystal structure.

[0051] Depend on Figure 4 As can be seen from the scanning electron microscope (SEM), we can clearly observe the morphology of DABCO-Co-TpDB, which is cubic in shape.

[0052] Depend on Figure 5 EDS mapping image analysis shows that carbon, oxygen, nitrogen, and Co elements are uniformly dispersed throughout the polymer backbone.

[0053] Figure 6 and 7 Its nanosheet structure was proven.

[0054] Example 2

[0055] The infrared spectra of TpDB, Co-TpDB, and DABCO-Co-TpDB were measured respectively, and the results are as follows: Figure 8 As shown. The results indicate that in NH (3385, 3364 cm⁻¹) -1 ) and C=O(1643 cm -1 The vibration band disappears, C=C vibration band (1552 cm) -1 The appearance of ) indicates the successful synthesis of TpDB. For Co-N vibration, DABCO-Co-TpDB showed activity at 538 and 570 cm⁻¹. -1 The bands are shown at 538 and 568 cm⁻¹, while Co-TpDB shows bands at 538 and 568 cm⁻¹. -1 The bands are displayed. These shifts towards longer wavenumbers suggest axial alignment of the DABCO.

[0056] Example 3

[0057] The method for preparing an electrocatalytic water splitting hydrogen evolution electrode using the covalent organic framework hydrogen evolution catalyst prepared in Example 1 is carried out according to the following steps:

[0058] 1) The L-shaped glassy carbon electrode was polished sequentially with polishing powder of 1.0 µm, 0.3 µm and 0.05 µm size, washed with water and dried to obtain an L-shaped glassy carbon electrode with contaminants removed and physical defects eliminated.

[0059] 2) Grind DABCO-Co-TpDB thoroughly in an agate mortar for 1-2 hours. Then, take 5 mg of DABCO-Co-TpDB, 50 µl of binder naphthol, 500 µl of anhydrous ethanol and 500 µl of water and mix them evenly by ultrasonication to obtain ink.

[0060] 3) Drop 5 µl of ink evenly onto the L-shaped glassy carbon electrode obtained in step 1), and dry it under infrared lamp irradiation for 20-40 min to obtain an electrocatalytic water splitting hydrogen evolution electrode.

[0061] The catalytic performance of the electrocatalytic water splitting and hydrogen evolution electrode prepared in this embodiment was tested on an electrochemical workstation. Electrochemical tests were performed on a CHI660E electrochemical workstation manufactured by Shanghai Chenhua Instrument Co., Ltd. The tests were conducted at room temperature using a three-electrode system, with the electrocatalytic water splitting and hydrogen evolution electrode as the working electrode, wherein the working electrode has a geometric area of ​​0.07065 cm². 2 A graphite rod was used as the counter electrode, and an Hg / HgO electrode was used as the reference electrode. The electrolyte was 1M KOH. The results are as follows: Figure 9 , 10 The results were shown at 10 mA cm⁻¹ -2 The overpotential of DABCO-Co-TpDB can be as low as 145.2 mV, corresponding to a Tafel slope of 46.4 mV dec.-1 This indicates that the covalent organic framework hydrogen evolution catalyst prepared in this embodiment has good hydrogen evolution performance.

Claims

1. A method for preparing a bidentate ligand-supported covalent organic framework hydrogen evolution catalyst, characterized in that... Includes the following steps: 1) Preparation of covalent organic framework: 1,3,5-tricarboxymethyl phloroglucinol, o-phenylenediamine and acid catalyst are added to organic solvent I and mixed evenly, then degassed, and reacted after degassed. After the reaction is completed, the reacted material is filtered, and the obtained filter solid is washed with organic solvent II and dried to obtain the covalent organic framework to be prepared. 2) Preparation of metal-doped covalent organic framework: The covalent organic framework, metal salt and acid catalyst obtained in step 1) are added to organic solvent I and mixed evenly, then degassed, and then reacted. After the reaction is completed, the reacted material is filtered, and the obtained filter solid is washed with organic solvent II and dried to obtain the metal-doped covalent organic framework to be prepared. 3) Preparation of bidentate ligand-supported covalent organic framework hydrogen evolution catalyst: The metal-doped covalent organic framework, bidentate ligand and acid catalyst obtained in step 2) are added to organic solvent I and mixed evenly, then degassed, and reacted. After the reaction is completed, the reacted material is filtered, and the obtained filter solid is washed with organic solvent II and dried, which is the bidentate ligand-supported covalent organic framework hydrogen evolution catalyst to be prepared. The metal salt is cobalt acetate; the bidentate ligand is triethylenediamine.

2. The method for preparing a bidentate ligand-supported covalent organic framework hydrogen evolution catalyst according to claim 1, characterized in that... In step 1), the molar ratio of 1,3,5-tricarboxymethyl phloroglucinol to o-phenylenediamine is 1:1 to 3; the molar ratio of 1,3,5-tricarboxymethyl phloroglucinol to acid catalyst is 1:2 to 4; the reaction temperature in step 1) is 100 to 150 °C, and the reaction time is 48 to 96 h.

3. The method for preparing a bidentate ligand-supported covalent organic framework hydrogen evolution catalyst according to claim 1, characterized in that... In step 2), the molar ratio of the covalent organic framework obtained in step 1) to the metal salt is 1:0.5 to 1.5; the molar ratio of the covalent organic framework obtained in step 1) to the acid catalyst is 1:2 to 4; the reaction temperature in step 2) is 100 to 150 °C, and the reaction time is 12 to 36 h.

4. The method for preparing a bidentate ligand-supported covalent organic framework hydrogen evolution catalyst according to claim 1, characterized in that... In step 3), the molar ratio of the metal-doped covalent organic framework obtained in step 2) to the bidentate ligand is 1:0.5 ~ 1.5; the molar ratio of the metal-doped covalent organic framework obtained in step 2) to the acid catalyst is 1:2 ~ 4; the reaction temperature in step 2) is 100 ~ 150 ℃, and the reaction time is 12 ~ 36 h.

5. The method for preparing a bidentate ligand-supported covalent organic framework hydrogen evolution catalyst according to claim 1, characterized in that... The acid catalyst is glacial acetic acid, trifluoroacetic acid, trifluoromethanesulfonic acid, or sulfuric acid; Organic solvent I is any two or three of the following: mesitylene, N,N-dimethylformamide, dioxane, o-dichlorobenzene, and n-butanol; Organic solvent II is any three or four of N,N-dimethylformamide, methanol, ethanol, acetone, tetrahydrofuran, and deionized water.

6. The method for preparing a bidentate ligand-supported covalent organic framework hydrogen evolution catalyst according to claim 5, characterized in that... The sulfuric acid has a mass percentage concentration of 30% to 40% or 95% to 98%.

7. A bidentate ligand-supported covalent organic framework hydrogen evolution catalyst prepared by the method according to any one of claims 1-6.

8. The application of the bidentate ligand-supported covalent organic framework hydrogen evolution catalyst as described in claim 7 as an electrocatalyst in the electrocatalytic splitting of water to produce hydrogen.

9. The application according to claim 8, characterized in that... Includes the following steps: 1) Polish the L-shaped glassy carbon electrode with polishing powder, wash and dry it to obtain an L-shaped glassy carbon electrode with contaminants removed and physical defects eliminated; 2) The bidentate ligand-supported covalent organic framework hydrogen evolution catalyst was thoroughly ground in an agate mortar, and then the bidentate ligand-supported covalent organic framework hydrogen evolution catalyst, binder, anhydrous ethanol and water were ultrasonically mixed evenly according to the mass ratio to obtain ink; 3) The ink obtained in step 2) is evenly dropped onto the L-shaped glassy carbon electrode obtained in step 1) and dried under infrared lamp irradiation to obtain an electrocatalytic water splitting and hydrogen evolution electrode.

10. The application according to claim 9, characterized in that... In step 1), the L-shaped glassy carbon electrode was polished sequentially with polishing powders of 1.0 µm, 0.3 µm, and 0.05 µm in size; In step 2), the mass ratio of the bidentate ligand-supported covalent organic framework hydrogen evolution catalyst, binder, anhydrous ethanol, and water is (1~5):0.01:100:100; the binder in step 2) is naphthol.

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