Application of a Ru-based Schiff base metal COF in hydrogen production by formic acid decomposition

Abstract

This invention discloses the application of Ru-based Schiff base metal COFs in the decomposition of formic acid to produce hydrogen, comprising the following steps: anhydrous formic acid is used as the reactant, and an alkali is added and mixed to obtain a reaction solution; under nitrogen or argon protection, Ru-based Schiff base metal COFs are added to the reaction solution as a heterogeneous catalyst, and a thermal reaction is carried out at 60-110℃, collecting the product gas; the large π bonds formed by the metal COFs endow the catalyst with overall electron-rich properties; more importantly, the ligands have large steric hindrance and structural rigidity, which can effectively protect the metal center, prevent its aggregation and deactivation, and extend the service life of the catalyst; the application of Ru-based Schiff base metal COFs in heterogeneous catalytic decomposition of formic acid to produce hydrogen exhibits superior catalytic performance and high catalytic conversion efficiency compared with existing heterogeneous catalysts for formic acid to produce hydrogen, and is also conducive to large-scale production.

Description

Technical Field

[0001] This invention relates to the field of hydrogen production technology, and in particular to the application of Ru-based Schiff alkali metal COFs in the decomposition of formic acid to produce hydrogen. Background Technology

[0002] Covalent organic frameworks (COFs) are a new type of porous framework materials constructed by connecting organic modules with different geometric configurations through covalent bonds. They are characterized by high specific surface area, light weight, diverse structures, and good chemical stability.

[0003] Hydrogen energy is a secondary energy source that is abundant, easy to prepare, widely applicable, and environmentally friendly, and is gradually becoming one of the important carriers for global energy transition. Hydrogen energy is also an important means to achieve carbon peaking and carbon neutrality goals and to build a clean, low-carbon, safe, and efficient energy system. However, due to the high cost of traditional high-pressure or low-temperature hydrogen storage, how to efficiently and safely store and transport hydrogen has become a key factor restricting the development of hydrogen energy. To address these issues, storing hydrogen in chemical molecular carriers and releasing it anytime and anywhere through catalytic reactions has become a research hotspot in recent years. Liquid organic hydrogen carriers (LOHCs) are such liquid hydrogen storage media that combine high hydrogen storage capacity and safety, and have received considerable attention in recent years. Formic acid is a representative LOHC material, possessing advantages such as high hydrogen storage capacity (4.4 wt%), wide availability, low toxicity, and ease of transportation.

[0004] It is worth noting that the key to realizing formic acid hydrogen storage technology lies in the development and preparation of formic acid hydrogen production catalysts, which is also a pressing challenge in this field. Current research on formic acid hydrogen production catalysts focuses on homogeneous and heterogeneous catalyst systems. Homogeneous catalysts have advantages such as precise structure, strong designability, high activity, and high selectivity, but also disadvantages such as difficulty in recovery and poor catalyst stability (e.g., many catalysts are sensitive to water and oxygen). In contrast, heterogeneous catalyst systems have advantages such as easy recovery and strong inherent catalyst stability, but generally suffer from low selectivity (e.g., high impurity content such as CO) and poor catalytic stability. Although some current catalyst systems can address one or more of these issues, most homogeneous and heterogeneous catalyst systems still lack long-term reaction stability, resulting in poor long-term catalytic reaction stability.

[0005] Therefore, there is still a lack of formic acid hydrogen production catalysts that combine high activity, high selectivity, and high stability. Designing and synthesizing novel catalyst systems with the above advantages has significant scientific and practical application value. Summary of the Invention

[0006] This invention proposes an application of Ru-based Schiff base metal COFs in the decomposition of formic acid to produce hydrogen, which solves the technical problems of low activity, poor selectivity and poor stability of existing formic acid hydrogen production catalysts.

[0007] To address the above problems, the present invention proposes the following technical solution:

[0008] This invention provides an application of Ru-based Schiff metal bases (COFs) in the decomposition of formic acid to produce hydrogen, wherein the Ru-based Schiff metal COFs include the following four:

[0009] Ru-DFP-TAB COFs:

[0010]

[0011] Ru-DFP-TTACOFs:

[0012]

[0013] Ru-BPDCA-TAB COFs:

[0014]

[0015] Ru-BPDCA-TTACOFs:

[0016]

[0017] Among them, DFP is 2,6-pyridinedicarboxaldehyde; TAB is 1,3,5-tris(4-aminophenyl)benzene; TTA is 2,4,6-tris(4-aminophenyl)-1,3,5-triazine; BPDCA is 2,2'-bipyridine-5,5'-dicarboxaldehyde; [RuCl2(CO)2] n , where n is a positive integer.

[0018] Based on this technical solution, and further preferably, the application of Ru-based Schiff base metal COFs in the decomposition of formic acid to produce hydrogen specifically includes the following steps:

[0019] Anhydrous formic acid is used as the raw material for the reaction. Then, alkali is added and the mixture is stirred to obtain the reaction solution.

[0020] Under nitrogen or argon protection, Ru-based Schiff alkali metal COFs are added to the reaction solution as a heterogeneous catalyst, and the reaction is carried out thermally at 60-110℃, and the product gas is collected.

[0021] Based on this technical solution, and more preferably, the molar volume ratio of the alkali to anhydrous formic acid is (60-160):(5-12)(mol / mL).

[0022] Based on this technical solution, and more preferably, the mass-to-volume ratio of the heterogeneous catalyst to formic acid is (1-20):10 (mg / mL).

[0023] Based on this technical solution, and further preferably, the method for preparing the Ru-based Schiff alkali metal COFs includes the following steps:

[0024] Step 1: 2,2'-bipyridine-5,5'-dicarboxaldehyde or 2,6-pyridinedicarboxaldehyde are reacted with 1,3,5-tris(4-aminophenyl)benzene or 2,4,6-tris(4-aminophenyl)-1,3,5-triazine via a condensation reaction to prepare COFs;

[0025] Step 2: Dissolve the metal compound in ethanol or dichloromethane, then add COFs to the ethanol or dichloromethane solution of the metal compound, and allow the reaction to stand for 48 hours. The metal compound is [RuCl2(CO)2]. n ;

[0026] After the reactions in steps 3 and 2 are completed, the reaction solution is filtered and washed to obtain Ru-based Schiff base metal COFs.

[0027] Based on this technical solution, and more preferably, the loading of the metal compound is 10-100 mg / g.

[0028] Based on this technical solution, more preferably, the molar ratio of 2,2'-bipyridine-5,5'-dicarboxaldehyde or 2,6-pyridinedicarboxaldehyde to 1,3,5-tris(4-aminophenyl)benzene or 2,4,6-tris(4-aminophenyl)-1,3,5-triazine is (1.18-1.5):1.

[0029] Based on this technical solution, and further preferably, the condensation reaction specifically includes the following steps:

[0030] 2,2'-bipyridine-5,5'-dicarboxaldehyde or 2,6-pyridinedicarboxaldehyde was mixed with 1,3,5-tris(4-aminophenyl)benzene or 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, and anhydrous ethanol or anhydrous dioxane was added as a solvent. The mixture was stirred well, and formic acid solution was added. The mixture was reacted at 120-130℃ for 1 hour, cooled naturally, filtered, washed, and dried to obtain COFs.

[0031] Based on this technical solution, and more preferably, the formic acid solution has a mass concentration of 1-6M.

[0032] Based on this technical solution, and more preferably, the alkali includes an organic alkali or an alkaline salt.

[0033] Compared with the prior art, the technical effects achieved by the present invention include:

[0034] This invention utilizes Schiff base COFs and metallic Ru to form Schiff base metal COFs for the decomposition of small molecule hydrogen storage compounds to produce hydrogen. Due to the large π bonds formed by the metal COFs, Ru atoms are endowed with electron-rich properties, and the steric hindrance of the ligands effectively protects the metal center. Furthermore, the COFs isolate Ru atoms from each other, greatly preventing aggregation and deactivation during the catalytic process. Therefore, the designed complex exhibits excellent catalytic performance. The advantages of this catalyst include its high stability in air (maintaining excellent catalytic performance even after one year of storage in air), simple preparation method, high activity (total TON can reach 1150 W), and high selectivity (extremely low CO content during the reaction). It can be prepared on a large scale for hydrogen production from formic acid.

[0035] The Schiff alkali metal COFs heterogeneous catalytic method for formic acid decomposition to produce hydrogen has a simple process, relatively mild reaction conditions, high hydrogen content, and good product quality, which is conducive to the application and promotion of the product.

[0036] The preparation method of Ru-Schiff base metal COFs is applied to the heterogeneous catalytic decomposition of formic acid to produce hydrogen. Compared with the existing industrial hydrogen production method of water electrolysis, this hydrogen production method has lower cost, is conducive to large-scale production, and has good industrial development prospects.

[0037] The CO content is extremely low (<50ppm) during the hydrogen production process, which is beneficial for expanding the application of this hydrogen product in hydrogen fuel cells. Attached Figure Description

[0038] Figure 1 The XRD patterns and fitting patterns of Schiff base (DFP-TAB) COFs and ruthenium-loaded Schiff base metal (Ru-DFP-TAB) COFs prepared in Example 1 of this invention are shown.

[0039] Figure 2 The figure shows the nitrogen adsorption-desorption experiment of DFP-TAB COFs prepared in Example 1 of this invention;

[0040] Figure 3 The figure shows the nitrogen adsorption-desorption experiment of Ru-DFP-TAB COFs prepared in Example 1 of this invention;

[0041] Figure 4 The infrared spectra of DFP-TAB COFs and Ru-DFP-TAB COFs prepared in Example 1 of this invention are shown below.

[0042] Figure 5Electron micrographs of DFP-TAB COFs and Ru-DFP-TAB COFs prepared in Example 1 of this invention.

[0043] Figure 6 This is a gas chromatogram of the product gas prepared in Example 5 of the present invention. Detailed Implementation

[0044] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art based on the technology to which the claims of the present invention pertain without creative effort are within the scope of protection of the present invention.

[0045] It should be understood that the terminology used in this specification of embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to limit the embodiments of the invention. As used in this specification of embodiments of the invention and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0046] Example 1

[0047] This embodiment provides a Ru-based Schiff base metal COFs, wherein the Ru-based Schiff base metal COFs are...

[0048] [RuCl2(CO)2] n A preferred preparation method includes the following steps:

[0049] Under air conditions, 21 mg of 1,3,5-tris(4-aminophenyl)benzene and 12 mg of 2,6-pyridinedicarboxaldehyde were added to a 20 mL reaction flask, followed by 3 mL of anhydrous dioxane. The mixture was shaken and mixed, and then 0.5 mL of formic acid solution was added. The mixture was stirred and reacted at high temperature for 1 hour. The reaction solid was filtered, washed with ethanol, and dried to obtain DFP-TAB COFs material.

[0050] 0.2g of [RuCl2(CO)2] n Dissolved in 20 mL of ethanol, added to DFP-TAB COFs, allowed to stand for 48 h, filtered after the reaction was completed, and dried to obtain Ru-DFP-TAB COFs catalyst.

[0051] Result: See Figure 1The figures show the XRD patterns and fitted spectra of the Schiff base (DFP-TAB) COFs and the Schiff base metal (Ru-DFP-TAB) COFs prepared in this embodiment. It can be seen that the experimentally obtained DFP-TAB COFs are in high agreement with the theoretical simulation results, proving that our synthesis was successful. The further synthesized Ru-DFP-TAB COFs also have peaks at the same positions at low angles, indicating that the overall COFs framework did not change significantly during the coordination process of Ru.

[0052] See Figure 2 The figure shows the nitrogen adsorption-desorption experiment of the DFP-TAB COFs prepared in this embodiment; it can be seen that the specific surface area of ​​the DFP-TAB COFs is 359.36 m². 2 The / g indicates its inherent porous nature. The total pore volume of the material was calculated to be 0.437 m³ when P / P0 = 0.99. 3 / g.

[0053] See Figure 3 The figure shows the nitrogen adsorption-desorption experiment of Ru-DFP-TAB COFs prepared in this embodiment; it can be seen that the specific surface area of ​​Ru-DFP-TAB COFs is 84.87 m². 2 The / g indicates its inherent porous nature. The total pore volume of the material was calculated to be 0.193 m³ when P / P0 = 0.99. 3 / g.

[0054] A comparison of the two figures above shows that the adsorption curves of DFP-TAB COFs and Ru-DFP-TAB COFs increase rapidly under low pressure, while the adsorption amount increases slowly as the pressure increases. Through data comparison, we can observe that the gas adsorption amount of Ru-DFP-TABCOFs is significantly lower than that of DFP-TAB COFs. This indirectly proves that the coordination of Ru atoms blocks part of the pore structure, resulting in a decrease in gas adsorption amount, which proves the successful coordination of Ru metal atoms.

[0055] See Figure 4 The figures show the infrared spectra of DFP-TAB COFs and Ru-DFP-TAB COFs prepared in this embodiment. It can be seen that no characteristic -CO peaks were observed in the DFP-TAB COFs framework; however, two distinct -CO peaks were present in the synthesized Ru-DFP-TAB COFs material, which originate from the raw material [RuCl2(CO)2]. n This further verified the successful coordination of Ru atoms. Infrared spectroscopy of the reacted Ru-DFP-TAB COFs revealed the presence of -CO, proving the structural stability during the reaction.

[0056] See Figure 5 The images shown are electron micrographs of DFP-TAB COFs and Ru-DFP-TAB COFs prepared in this embodiment; it can be seen that... Figure 5 (a) and Figure 5 (b) are transmission electron microscopy and scanning electron microscopy images of the corresponding DFP-TAB COFs. Figure 5 (c) and Figure 5 The transmission electron microscope (TEM) and scanning electron microscope (SEM) images of Ru-DFP-TAB COFs (d) show that, by comparison, we can observe that there are significantly more black particles in the TEM image of Ru-DFP-TAB COFs, which is direct evidence of Ru atom loading. Figure 5 (b) and Figure 5 (d) It can be observed that DFP-TAB COFs and Ru-DFP-TAB COFs have obvious pore structures, which is beneficial to the mass transfer of substrates during the reaction process.

[0057] Example 2

[0058] This embodiment provides a Ru-based Schiff base metal COFs, wherein the Ru-based Schiff base metal COFs are...

[0059] [RuCl2(CO)2] n

[0060] A preferred preparation method includes the following steps:

[0061] Under air conditions, 21 mg of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 12 mg of 2,6-pyridinedicarboxaldehyde were added to a 20 mL reaction flask, followed by 3 mL of anhydrous dioxane. The mixture was shaken and mixed thoroughly, and then 0.5 mL of formic acid solution was added. After mixing, the mixture was reacted at high temperature for 1 hour. The reaction solid was filtered, washed with ethanol, and dried to obtain DFP-TTA COFs material.

[0062] 0.4g of [RuCl2(CO)2] n Dissolved in 20 mL of ethanol, added to DFP-TTA COFs, allowed to stand for 48 h, filtered after the reaction was completed, and dried to obtain Ru-DFP-TTA COFs catalyst.

[0063] Example 3

[0064] This embodiment provides a Ru-based Schiff base metal COFs, wherein the Ru-based Schiff base metal COFs are...

[0065]

[0066] [RuCl2(CO)2] n

[0067] A preferred preparation method includes the following steps:

[0068] Under air conditions, 21 mg of 1,3,5-tris(4-aminophenyl)benzene and 15 mg of 2,2'-bipyridine-5,5'-dicarboxaldehyde were added to a 20 mL reaction flask, followed by 3 mL of anhydrous ethanol. The mixture was shaken and mixed thoroughly, and then 0.5 mL of formic acid solution was added. After mixing, the mixture was reacted at high temperature for 1 hour. The reaction solid was filtered, washed with ethanol, and dried to obtain the BPDCA-TAB COFs material.

[0069] Add 0.3g of [RuCl2(CO)2] n Dissolved in 20 mL of ethanol, added to BPDCA-TAB COFs, allowed to stand for 48 h, filtered after the reaction was completed, and dried to obtain Ru-BPDCA-TAB COFs catalyst.

[0070] Example 4

[0071] This embodiment provides a Ru-based Schiff base metal COFs, wherein the Ru-based Schiff base metal COFs are...

[0072] [RuCl2(CO)2] n

[0073] A preferred preparation method includes the following steps:

[0074] Under air conditions, 21 mg of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 15 mg of 2,2'-bipyridine-5,5'-dicarboxaldehyde were added to a 20 mL reaction flask, followed by 3 mL of anhydrous ethanol. The mixture was shaken and mixed thoroughly, and then 0.5 mL of formic acid solution was added. After mixing, the mixture was reacted at high temperature for 1 hour. The reaction solid was filtered, washed with ethanol, and dried to obtain the BPDCA-TTACOFs material.

[0075] Add 0.3g of [RuCl2(CO)2] n Dissolved in 20 mL of ethanol, added to BPDCA-TTA COFs, allowed to stand for 48 h, filtered after the reaction was completed, and dried to obtain Ru-BPDCA-TTACOFs catalyst.

[0076] Example 5

[0077] This embodiment provides an application of Ru-based Schiff base metal COFs in heterogeneous catalytic formic acid decomposition for hydrogen production, specifically including the following steps:

[0078] Use argon gas to pressurize the water in the gas measuring tube into the separatory funnel, then close the gas measuring tube stopcock. Remove the air from the reaction apparatus, repeating this process three times. While the gas is being pressurized with argon gas, add 108 mmol of triethylamine and 10 mL of formic acid to the reaction flask. Then open the gas measuring tube stopcock to allow the water from the separatory funnel to return to the measuring tube. Adjust the height of the separatory funnel and the gas measuring tube so that the liquid levels inside are equal, and record the liquid level on the gas measuring tube at this point as V1. Then heat the reaction solution to 110°C and hold for 15 minutes, recording the liquid level on the gas measuring tube at this point as V2. The background volume is then V2 - V1.

[0079] Stop heating, cool the reaction solution to room temperature with ice water, open the rubber stopper, connect the gas tube with a needle, and purge the reaction solution with argon gas for 30 minutes to remove oxygen. Add 1 μmol (4.5 mg) of catalyst under nitrogen purging. Purge with argon gas for a final 30 minutes, then heat to 110°C for 4 hours to carry out the catalytic reaction. Record the gas volume in the gas tube and the ambient temperature every hour.

[0080] The methods for calculating TON and TOF of the reaction are as follows:

[0081] For experimental data using the obtained gas volume, TON is calculated based on the amount of hydrogen produced; that is, one TON represents each hydrogen molecule produced. Specifically, the formula for calculating TON is as follows:

[0082]

[0083] V obs Volume (mL) obtained from the gas measuring tube reading

[0084] V blank Blank experiment volume (mL)

[0085] n cat Catalyst dosage (mmol)

[0086] The molar volume of the gas at temperature T℃, as in the experiment conducted in this patent at 22℃. (Calculated from the following van der Waals equation)

[0087]

[0088] For hydrogen, the above parameters are: R = 8.3145m 3 Pa·mol -1 ·K -1 ,T=298.15K, p=101325Pa, a=2.49·10 -10 Pa·m 3 ·mol -2 b = 26.7 × 10 -6m 3 ·mol -1 .

[0089] The TON (total oxygen) and TOF (total oxygen) for 4 hours of catalyst reaction are calculated to be 74380 and 18595 h, respectively, based on equations (1) and (2). -1 After the reaction is complete, the reaction solution is cooled to room temperature, and the noble metal Ru is recovered; the gas chromatogram (GC) of the collected gas is shown below. Figure 6 As shown, the extremely low CO content (<50ppm) during the reaction process is beneficial for hydrogen production.

[0090] The base is selected from organic bases or basic salts, such as triethylamine, diethylamine, sodium formate, etc. The amount of base used has a significant impact on the pH of the reaction solution; both excessively high and low pH will severely affect the catalyst's reactivity. Furthermore, when the pH is low, the strongly acidic solution will also disrupt the Schiff base framework, leading to a reduction in catalyst lifetime.

[0091] After the reaction is completed, the reaction solution is post-treated to cool the remaining reaction solution to room temperature, filter the reaction solution, and separate the catalyst from the reaction solution. In this embodiment, the Schiff base metal complex is insoluble in the reaction solution. Under the condition of heating to the reaction temperature, the heterogeneous catalytic reaction of formic acid and water is realized, which improves the catalytic efficiency. After the reaction is completed and cooled, the catalyst can be separated by separating the solvent layer and recycled after treatment. For example, after treatment, relevant noble metal compounds can be obtained, realizing the reuse of noble metals.

[0092] Example 6

[0093] This embodiment provides an application of Ru-based Schiff base metal COFs in heterogeneous catalytic formic acid decomposition for hydrogen production, specifically including the following steps:

[0094] 108 mol of triethylamine was placed in a three-necked flask, and 10 mL of formic acid was slowly added dropwise. The neutralization reaction generated a large amount of heat. After the mixture cooled, the oxygen in the mixture was removed by purging for half an hour. 1 μmol of catalyst (Ru-DFP-TABCOFs) was added under purging conditions, the purging was stopped, the gas measuring tube was leveled, and the reaction apparatus was placed in a preheated oil bath at 100°C. Stirring was started, and the gas volume was observed. After 4 hours of experiment, TON was 60950, and TOF (4h) was 15238h. -1 .

[0095] Example 7

[0096] This embodiment provides an application of Ru-based Schiff base metal COFs in heterogeneous catalytic formic acid decomposition for hydrogen production, specifically including the following steps:

[0097] 108 mol of triethylamine was placed in a three-necked flask, and 10 mL of formic acid was slowly added dropwise. The neutralization reaction generated a large amount of heat. After the mixture cooled, the oxygen in the mixture was removed by purging for half an hour. 1 μmol (4.5 mg) of catalyst (Ru-DFP-TAB COFs) was added under purging conditions. Purging was stopped, the gas measuring tube was leveled, and the reaction apparatus was placed in a preheated oil bath at 90°C. Stirring was started, and the gas volume was observed. After 4 hours of experiment, the TON was 33678, and the TOF (4 h) was 8419 h. -1 .

[0098] Example 8

[0099] This embodiment provides an application of Ru-based Schiff base metal COFs in heterogeneous catalytic formic acid decomposition for hydrogen production, specifically including the following steps:

[0100] 108 mol of triethylamine was placed in a three-necked flask, and 10 mL of formic acid was slowly added dropwise. The neutralization reaction generated a large amount of heat. After the mixture cooled, the oxygen in the mixture was removed by purging for half an hour. 1 μmol (4.5 mg) of catalyst (Ru-DFP-TAB COFs) was added under purging conditions. Purging was stopped, the gas measuring tube was leveled, and the reaction apparatus was placed in a preheated oil bath at 80°C. Stirring was started, and the gas volume was observed. After 4 hours of experiment, TON was 19421 and TOF (4 h) was 4855 h. -1 .

[0101] Example 9

[0102] This embodiment provides an application of Ru-based Schiff base metal COFs in heterogeneous catalytic formic acid decomposition for hydrogen production, specifically including the following steps:

[0103] 108 mol of triethylamine was placed in a three-necked flask, and 10 mL of formic acid was slowly added dropwise. The neutralization reaction generated a large amount of heat. After the mixture cooled, the oxygen in the mixture was removed by purging for half an hour. 1 μmol (4.5 mg) of catalyst (Ru-DFP-TAB COFs) was added under purging conditions. Purging was stopped, the gas measuring tube was leveled, and the reaction apparatus was placed in a preheated oil bath at 70°C. Stirring was started, and the gas volume was observed. After 4 hours of experiment, TON was 10950, and TOF (4 h) was 2738 h. -1 .

[0104] Example 10

[0105] This embodiment provides an application of Ru-based Schiff base metal COFs in heterogeneous catalytic formic acid decomposition for hydrogen production, specifically including the following steps:

[0106] 72 mol of triethylamine was placed in a three-necked flask, and 10 mL of formic acid was slowly added dropwise. The neutralization reaction generated a large amount of heat. After the mixture cooled, the oxygen in the mixture was removed by purging for half an hour. 1 μmol (4.5 mg) of catalyst (Ru-DFP-TAB COFs) was added under purging conditions. Purging was stopped, the gas measuring tube was leveled, and the reaction apparatus was placed in a preheated oil bath at 70°C. Stirring was started, and the gas volume was observed. After 4 hours of experiment, the TON was 5579 and the TOF (4 h) was 1395 h. -1 .

[0107] Example 11

[0108] This embodiment provides an application of Ru-based Schiff base metal COFs in heterogeneous catalytic formic acid decomposition for hydrogen production, specifically including the following steps:

[0109] 100 mol of diethylamine was placed in a three-necked flask, and 10 mL of formic acid was slowly added dropwise. The neutralization reaction generated a large amount of heat. After the mixture cooled, the oxygen in the mixture was removed by purging for half an hour. 1 μmol (4.5 mg) of catalyst (Ru-DFP-TAB COFs) was added under purging conditions. Purging was stopped, the gas measuring tube was leveled, and the reaction apparatus was placed in a preheated oil bath at 100°C. Stirring was started, and the gas volume was observed. After 4 hours of experiment, the TON was 14375, and the TOF (4 h) was 3594 h. -1 .

[0110] Example 12

[0111] This embodiment provides an application of Ru-based Schiff base metal COFs in heterogeneous catalytic formic acid decomposition for hydrogen production, specifically including the following steps:

[0112] 100 mol of potassium formate was placed in a three-necked flask, and 10 mL of formic acid was slowly added dropwise. The neutralization reaction generated a large amount of heat. After the mixture cooled, the oxygen in the mixture was removed by purging for half an hour. 1 μmol (4.5 mg) of catalyst (Ru-DFP-TAB COFs) was added under purging conditions. Purging was stopped, the gas measuring tube was leveled, and the reaction apparatus was placed in a preheated oil bath at 100°C. Stirring was started, and the gas volume was observed. After 4 hours of experiment, the TON was 3958 and the TOF (4 h) was 990 h. -1 .

[0113] Example 13

[0114] This embodiment provides an application of Ru-based Schiff base metal COFs in heterogeneous catalytic formic acid decomposition for hydrogen production, specifically including the following steps:

[0115] 100 mol of sodium formate was placed in a three-necked flask, and 10 mL of formic acid was slowly added dropwise. The neutralization reaction generated a large amount of heat. After the mixture cooled, the oxygen in the mixture was removed by purging for half an hour. 1 μmol (4.5 mg) of catalyst (Ru-DFP-TAB COFs) was added under purging conditions. Purging was stopped, the gas measuring tube was leveled, and the reaction apparatus was placed in a preheated oil bath at 100°C. Stirring was started, and the gas volume was observed. After 4 hours of experiment, TON was 4688 and TOF (4 h) was 1172 h. -1 .

[0116] Example 14

[0117] This embodiment provides an application of Ru-based Schiff base metal COFs in heterogeneous catalytic formic acid decomposition for hydrogen production, specifically including the following steps:

[0118] 100 mol of sodium ethoxide was placed in a three-necked flask, and 10 mL of formic acid was slowly added dropwise. The neutralization reaction generated a large amount of heat. After the mixture cooled, oxygen was removed by purging for half an hour. Then, 1 μmol (4.5 mg) of catalyst (Ru-DFP-TAB COFs) was added under purging conditions. Purging was stopped, the gas measuring tube was leveled, and the reaction apparatus was placed in a preheated oil bath at 100°C. Stirring was started, and the gas volume was observed. No hydrogen was produced, indicating no catalytic effect. This demonstrates that the type of base has a significant impact on catalyst performance. This may be due to the different solubilities of the base in the reaction system, leading to changes in the pH of the reaction system. Screening for the type of base is an important process in optimizing reaction conditions.

[0119] Example 15

[0120] This embodiment provides an application of Ru-based Schiff base metal COFs in heterogeneous catalytic formic acid decomposition for hydrogen production, specifically including the following steps:

[0121] 100 mol of diisopropylamine was placed in a three-necked flask, and 10 mL of formic acid was slowly added dropwise. The neutralization reaction generated a large amount of heat. After the mixture cooled, the oxygen in the mixture was removed by purging for half an hour. 1 μmol (4.5 mg) of catalyst (Ru-DFP-TAB COFs) was added under purging conditions. Purging was stopped, the gas measuring tube was leveled, and the reaction apparatus was placed in a preheated oil bath at 100°C. Stirring was started, and the gas volume was observed. After 4 hours of experiment, the TON was 3854 and the TOF (4 h) was 964 h. -1 .

[0122] Example 16

[0123] This embodiment provides an application of Ru-based Schiff base metal COFs in heterogeneous catalytic formic acid decomposition for hydrogen production, specifically including the following steps:

[0124] 108 mol of triethylamine was placed in a three-necked flask, and 10 mL of formic acid was slowly added dropwise. The neutralization reaction generated a large amount of heat. After the mixture cooled, the oxygen in the mixture was removed by purging for half an hour. 1 μmol (3.9 mg) of catalyst (Ru-DFP-TTACOFs) was added under purging conditions. Purging was stopped, the gas measuring tube was leveled, and the reaction apparatus was placed in a preheated oil bath at 90°C. Stirring was started, and the gas volume was observed. After 4 hours of experiment, TON was 15155 and TOF (4 h) was 3789 h. -1 .

[0125] Example 17

[0126] This embodiment provides an application of Ru-based Schiff base metal COFs in heterogeneous catalytic formic acid decomposition for hydrogen production, specifically including the following steps:

[0127] 108 mol of triethylamine was placed in a three-necked flask, and 10 mL of formic acid was slowly added dropwise. The neutralization reaction generated a large amount of heat. After the mixture cooled, the oxygen in the mixture was removed by purging for half an hour. 1 μmol (2.6 mg) of catalyst (Ru-BPDCA-TAB COFs) was added under purging conditions. Purging was stopped, the gas measuring tube was leveled, and the reaction apparatus was placed in a preheated oil bath at 90°C. Stirring was started, and the gas volume was observed. After 4 hours of experiment, TON was 18523 and TOF (4 h) was 4631 h. -1 .

[0128] Example 18

[0129] This embodiment provides an application of Ru-based Schiff base metal COFs in heterogeneous catalytic formic acid decomposition for hydrogen production, specifically including the following steps:

[0130] 60 mL (432 mmol) of triethylamine was placed in a three-necked flask, and 40 mL of formic acid was slowly added dropwise. The neutralization reaction generated a large amount of heat. After the mixture cooled, the oxygen in the mixture was removed by purging for half an hour. 4 μmol (18 mg) of catalyst (Ru-DFP-TAB COFs) was added under purging conditions. Purging was stopped, and a flow meter was connected. The reaction apparatus was placed in a preheated oil bath at 100 °C, and stirring was started. The reaction volume was measured using the flow meter. Formic acid was continuously added during the reaction. The catalyst experiment lasted for more than 38 days, with a total TON of 11517181 and a TOF (38 days) of 12695 h. -1 .

[0131] It is evident that the Ru-based Schiff base metal COFs described in this embodiment are the most active heterogeneous formic acid decomposition catalysts for hydrogen production, among those reported to date.

[0132] In summary, the Ru-based Schiff alkali metal COFs proposed in this invention have good catalyst selectivity, high activity, and a TON close to 1200 W, which is the best among the reported heterogeneous catalysts and has a long service life. The decomposition method for producing hydrogen is simple, the reaction conditions are relatively mild, and the hydrogen content produced is high, resulting in good product quality, which is conducive to the application and promotion of the product.

[0133] 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. An application of Ru-based Schiff alkali metal COFs in the decomposition of formic acid to produce hydrogen, characterized in that, The Ru-based Schiff base metal COFs include the following four: Ru-DFP-TAB COFs: ； Ru-DFP-TTA COFs: ； Ru-BPDCA-TAB COFs: ； Ru-BPDCA-TTA COFs: ； Wherein, DFP is 2,6-pyridinedicarboxaldehyde; TAB is 1,3,5-tris(4-aminophenyl)benzene; TTA is 2,4,6-tris(4-aminophenyl)-1,3,5-triazine; BPDCA is 2,2'-bipyridine-5,5'-dicarboxaldehyde; and [RuCl2(CO)2] is used. n , where n is a positive integer.

2. The application of Ru-based Schiff alkali metal COFs as described in claim 1 in the hydrogen production from formic acid decomposition, characterized in that, Specifically, the following steps are included: Anhydrous formic acid is used as the raw material for the reaction. Then, alkali is added and the mixture is stirred to obtain the reaction solution. Under nitrogen or argon protection, Ru-based Schiff alkali metal COFs are added to the reaction solution as a heterogeneous catalyst, and the reaction is carried out thermally at 60-110℃, and the product gas is collected.

3. The application of Ru-based Schiff alkali metal COFs as described in claim 2 in the hydrogen production from formic acid decomposition, characterized in that, The molar volume ratio of the alkali to anhydrous formic acid is (60-160):(5-12) mol / mL.

4. The application of Ru-based Schiff alkali metal COFs as described in claim 2 in the hydrogen production from formic acid decomposition, characterized in that, The mass-to-volume ratio of the heterogeneous catalyst to anhydrous formic acid is (1-20):10 mg / mL.

5. The application of Ru-based Schiff alkali metal COFs as described in claim 1 in the hydrogen production from formic acid decomposition, characterized in that, The method for preparing the Ru-based Schiff base metal COFs includes the following steps: Step 1: 2,2'-bipyridine-5,5'-dicarboxaldehyde or 2,6-pyridinedicarboxaldehyde are reacted with 1,3,5-tris(4-aminophenyl)benzene or 2,4,6-tris(4-aminophenyl)-1,3,5-triazine via a condensation reaction to prepare COFs; Step 2: Dissolve the metal compound in ethanol or dichloromethane, then add COFs to the ethanol or dichloromethane solution of the metal compound, and allow the reaction to stand for 48 hours. The metal compound is [RuCl2(CO)2]. n ; After the reactions in steps 3 and 2 are completed, the reaction solution is filtered and washed to obtain Ru-based Schiff base metal COFs.

6. The application of Ru-based Schiff alkali metal COFs as described in claim 5 in the hydrogen production from formic acid decomposition, characterized in that, The loading of the metal compound is 10-100 mg / g.

7. The application of Ru-based Schiff alkali metal COFs as described in claim 5 in the hydrogen production from formic acid decomposition, characterized in that, The molar ratio of 2,2'-bipyridine-5,5'-dicarboxaldehyde or 2,6-pyridinedicarboxaldehyde to 1,3,5-tris(4-aminophenyl)benzene or 2,4,6-tris(4-aminophenyl)-1,3,5-triazine is (1.18-1.5):

1.

8. The application of Ru-based Schiff alkali metal COFs as described in claim 5 in the hydrogen production from formic acid decomposition, characterized in that, The condensation reaction specifically includes the following steps: 2,2'-bipyridine-5,5'-dicarboxaldehyde or 2,6-pyridinedicarboxaldehyde was mixed with 1,3,5-tris(4-aminophenyl)benzene or 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, and anhydrous ethanol or anhydrous dioxane was added as a solvent. The mixture was stirred well, and formic acid solution was added. The mixture was reacted at 120-130℃ for 1 hour, cooled naturally, filtered, washed, and dried to obtain COFs.

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