An M-HOF material, its preparation method and application in hydroxide ion recognition

Abstract

This invention belongs to the field of metal-hydrogen-bonded organic framework technology, and discloses an M-HOF material, its preparation method, and its application in hydroxide ion recognition. The preparation method of the M-HOF material includes the following steps: mixing methyl 4-(N-hydroxyformamidinium)benzoate, isonicotinyl chloride hydrochloride, triethylamine, and acetonitrile to carry out a first reaction to obtain an intermediate product; mixing the intermediate product, lithium hydroxide, methanol, and water to carry out a second reaction; after the second reaction, adjusting the pH of the obtained product to ≤1 to obtain a pyridine-carboxylic acid ligand; mixing the pyridine-carboxylic acid ligand, zinc nitrate hexahydrate, N,N-dimethylformamide, and water to carry out a third reaction to obtain the M-HOF material. The M-HOF material of this invention has a layered aggregate structure and exhibits good stability in aqueous solutions at different pH values. Its aqueous phase stability lays a solid foundation for its future application research.

Description

Technical Field

[0001] This invention relates to the field of metal-hydrogen-bonded organic framework technology, and more particularly to an M-HOF material, its preparation method, and its application in hydroxide ion recognition. Background Technology

[0002] The biggest difference between metal-hydrogen-bonded organic frameworks (M-HOFs) and MOFs is that the structure of M-HOFs is constructed from hydrogen bonds between coordination molecules. The inherent hydrogen bonding interactions within their structure give M-HOFs research potential in many fields, including gas adsorption, sensing, and proton conduction. However, due to the difficulties in designing and controlling the structure of M-HOFs, research on them is still in its early stages compared to mature systems such as MOFs and COFs. Therefore, researching novel M-HOF materials is significant for expanding the scope and depth of M-HOF research.

[0003] Hydroxides are among the most widely used basic chemical products, with extensive applications in industry. Soluble hydroxides can cause a series of serious harms to living organisms and the entire ecosystem by raising the pH of solutions; therefore, it is often necessary to control the OH content in aqueous solutions during production and daily life. - The concentration of OH- is detected. Currently, a series of methods exist for detecting OH-, such as titration, colorimetry, or electrochemical methods. However, these methods often suffer from problems such as long detection times, susceptibility to interference, or poor accuracy. Therefore, it is necessary to design novel OH- detection methods. - Sensing and detection materials. Current research has developed a variety of materials that can be used for OH detection. – The tested MOF materials. However, due to limitations in some MOFs, including stability, response range, and anti-interference ability, further development of novel stable and anti-interference OH groups is needed. - Sensing materials. Summary of the Invention

[0004] The purpose of this invention is to provide an M-HOF material, its preparation method, and its application in hydroxide ion recognition, thereby solving the problems of existing methods for detecting OH-. - The problems include long detection time, susceptibility to interference, and poor accuracy.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] This invention provides a method for preparing M-HOF materials, comprising the following steps:

[0007] Methyl 4-(N-hydroxyformamidinium)benzoate, isonicotinyl chloride hydrochloride, triethylamine and a first solvent were mixed and subjected to a first reaction to obtain an intermediate product.

[0008] The intermediate product, inorganic base, and second solvent are mixed to carry out the second reaction. After the second reaction is completed, the pH of the obtained product is adjusted to ≤1 to obtain the pyridine-carboxylic acid ligand.

[0009] The pyridine-carboxylic acid ligand, zinc nitrate, N,N-dimethylformamide and water were mixed and subjected to a third reaction to obtain the M-HOF material.

[0010] Preferably, in the above-mentioned method for preparing an M-HOF material, the molar ratio of methyl 4-(N-hydroxymethylamidine)benzoate, isonicotinyl chloride hydrochloride, and triethylamine is 1-2:1-2:1-6.

[0011] The ratio of triethylamine to the first solvent is 0.5–2 mol: 1 L;

[0012] The first solvent is acetonitrile.

[0013] Preferably, in the above-mentioned method for preparing M-HOF material, the conditions for the first reaction are: argon atmosphere, temperature of 50-100℃, and time of 6-18h.

[0014] Preferably, in the above-mentioned method for preparing M-HOF material, the molar ratio of the intermediate product to the inorganic base is 1:1 to 5;

[0015] The inorganic base is lithium hydroxide, sodium hydroxide, or potassium hydroxide;

[0016] The mass ratio of the intermediate product to the volume ratio of the second solvent is 1-2 g: 15-50 mL;

[0017] The second solvent is a mixed solution of alcohol and water;

[0018] The volume ratio of alcohol to water in the second solvent is 1-3:1-3.

[0019] Preferably, in the above-mentioned method for preparing M-HOF material, the temperature of the second reaction is 85-95°C, and the reaction time is 8-16 hours.

[0020] Preferably, in the above-mentioned method for preparing M-HOF material, the molar ratio of pyridine-carboxylic acid ligand to zinc nitrate is 1:0.5-2;

[0021] The ratio of the pyridine-carboxylic acid ligand, N,N-dimethylformamide, and water is 0.2–1.8 mmol: 10 mL: 30–50 mL.

[0022] Preferably, in the above-mentioned method for preparing M-HOF material, the temperature of the third reaction is 80-120°C, and the time of the third reaction is 48-240 h.

[0023] The present invention also provides a method for preparing M-HOF materials, and the resulting M-HOF material.

[0024] This invention also provides an application of M-HOF material in hydroxide ion recognition.

[0025] Preferably, in the application of the above-mentioned M-HOF material in hydroxide ion recognition, the method of application includes the following steps:

[0026] The M-HOF material was mixed with water to obtain a suspension; then the suspension was mixed with an aqueous hydroxide ion solution to obtain a mixed solution, and the mixed solution was detected by ultraviolet-visible absorption spectroscopy.

[0027] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects:

[0028] The M-HOF material of this invention possesses a layered aggregate structure and exhibits excellent stability in aqueous solutions with varying pH values. Its aqueous phase stability lays a solid foundation for its future application research. The principle of UV-Vis recognition of hydroxide ions using the M-HOF material of this invention is based on the hydrogen-removing effect of hydroxide ions, which disrupts hydrogen bond interactions within the material and releases charged small molecules. Recognition of hydroxide ions is achieved through gradual dissociation from the outside in. This material can be used to recognize hydroxide ions, expanding the application range of M-HOF materials; furthermore, under current recognition conditions, this material exhibits good linearity in the recognition of hydroxide ions; simultaneously, the material demonstrates good anti-interference capability in its recognition of hydroxide ions. Attached Figure Description

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for describing the embodiments or the prior art.

[0030] Figure 1 This is a single-molecule structure diagram of the M-HOF material in Example 1;

[0031] Figure 2 This is a layered aggregation diagram of the M-HOF material in Example 1;

[0032] Figure 3 The thermal analysis diagram of the M-HOF material in Example 1 is shown.

[0033] Figure 4 The image shows the XRD patterns of the M-HOF material from Example 1 after soaking in aqueous solutions at different pH values ​​for 3 days.

[0034] Figure 5 The UV-Vis recognition results of sodium hydroxide by the M-HOF material in Example 1 are shown.

[0035] Figure 6 The UV-Vis recognition results of potassium hydroxide by the M-HOF material in Example 1 are shown.

[0036] Figure 7 The UV-Vis recognition results of lithium hydroxide by the M-HOF material in Example 1 are shown.

[0037] Figure 8 The UV-Vis recognition results of barium hydroxide by the M-HOF material in Example 1 are shown. Detailed Implementation

[0038] The invention provides a method for preparing M-HOF material, comprising the following steps:

[0039] Methyl 4-(N-hydroxyformamidinium)benzoate, isonicotinyl chloride hydrochloride, triethylamine and a first solvent were mixed and subjected to a first reaction to obtain an intermediate product.

[0040] The intermediate product, inorganic base, and second solvent are mixed to carry out the second reaction. After the second reaction is completed, the pH of the obtained product is adjusted to ≤1 to obtain the pyridine-carboxylic acid ligand.

[0041] The pyridine-carboxylic acid ligand, zinc nitrate, N,N-dimethylformamide and water were mixed and subjected to a third reaction to obtain the M-HOF material.

[0042] In this invention, the specific process of mixing methyl 4-(N-hydroxyformamidinium)benzoate, isonicotinyl chloride hydrochloride, triethylamine, and the first solvent is as follows:

[0043] First, methyl 4-(N-hydroxymethylamidine)benzoate, triethylamine, and the first solvent are mixed, and then isonicotinic acid chloride hydrochloride is added in batches and mixed.

[0044] There is no special limit to the number of times the material can be added in batches, as long as no material is sprayed during the batch addition process.

[0045] In this invention, the CAS number of the methyl 4-(N-hydroxymethylamidine)benzoate is 184778-33-4.

[0046] In this invention, the molar ratio of methyl 4-(N-hydroxymethylamidine)benzoate, isonicotinyl chloride hydrochloride and triethylamine is preferably 1-2:1-2:1-6, more preferably 1-1.7:1-1.7:2-5, and even more preferably 1:1:3.

[0047] In this invention, the ratio of triethylamine to the first solvent is preferably 0.5 to 2 mol: 1 L, more preferably 1 to 1.5 mol: 1 L, and even more preferably 1.2 mol: 1 L.

[0048] In this invention, the first solvent is preferably acetonitrile.

[0049] In this invention, the conditions for the first reaction are as follows: the atmosphere is preferably argon; the temperature is preferably 50-100°C, more preferably 70-90°C, and even more preferably 85°C; the time is preferably 6-18h, more preferably 8-16h, and even more preferably 12h.

[0050] In this invention, after the first reaction is completed, the process further includes: mixing the product with a saturated NaHCO3 solution to quench the reaction, followed by extraction, drying, and purification.

[0051] The preferred ratio of saturated NaHCO3 solution to methyl 4-(N-hydroxyformamidinium)benzoate is 1-2.5 L: 1-2 mol, more preferably 1.25-2 L: 1-1.7 mol, and even more preferably 1.5 L: 1 mol.

[0052] The preferred extractant in the extraction process is dichloromethane;

[0053] The preferred desiccant for drying is anhydrous Na2SO4;

[0054] The preferred purification method is silica gel column purification;

[0055] The eluent used in purification is preferably a mixture of petroleum ether and ethyl acetate, with a volume ratio of petroleum ether to ethyl acetate preferably of 4:1.

[0056] In this invention, the specific process of mixing the intermediate product, the inorganic base, and the second solvent is as follows:

[0057] The intermediate product is mixed with a second solvent, and then an inorganic base is added.

[0058] In this invention, the molar ratio of the intermediate product to the inorganic base is preferably 1:1 to 5, more preferably 1:1 to 2, and even more preferably 1:1.25.

[0059] In this invention, the inorganic base is preferably lithium hydroxide, sodium hydroxide or potassium hydroxide, more preferably lithium hydroxide or sodium hydroxide, and even more preferably lithium hydroxide;

[0060] The lithium hydroxide is preferably lithium hydroxide monohydrate.

[0061] In this invention, the mass ratio of the intermediate product to the volume ratio of the second solvent is preferably 1-2 g: 15-50 mL, more preferably 1.2-1.6 g: 20-40 mL, and even more preferably 1.4 g: 30 mL.

[0062] In this invention, the second solvent is preferably a mixed solution of an alcohol and water;

[0063] The alcohol is preferably methanol or ethanol, and more preferably methanol.

[0064] In this invention, the volume ratio of alcohol to water in the second solvent is preferably 1-3:1-3, more preferably 1-2.5:1-2.5, and even more preferably 1:1.

[0065] In this invention, the temperature of the second reaction is preferably 85-95°C, more preferably 82-87°C, and even more preferably 85°C; the time of the second reaction is preferably 8-16 hours, more preferably 10-14 hours, and even more preferably 12 hours.

[0066] In this invention, adjusting the pH of the obtained product to ≤1 is preferably done using hydrochloric acid.

[0067] In this invention, after adjusting the pH of the obtained product to ≤1, the process further includes: obtaining the product by rotary evaporation under reduced pressure, filtering the product, and washing and drying the filtered filter cake.

[0068] The detergent used in the washing process is water.

[0069] In this invention, the structure of the pyridine-carboxylic acid ligand is shown in Formula 1.

[0070]

[0071] In this invention, the molar ratio of the pyridine-carboxylic acid ligand to zinc nitrate is preferably 1:0.5 to 2, more preferably 1:0.7 to 1.5, and even more preferably 1:1.

[0072] The ratio of the pyridine-carboxylic acid ligand, N,N-dimethylformamide, and water is 0.2–1.8 mmol:10 mL:30–50 mL, more preferably 0.5–1.5 mmol:10 mL:35–45 mL, and even more preferably 1 mmol:10 mL:40 mL.

[0073] In this invention, the zinc nitrate is preferably zinc nitrate hexahydrate.

[0074] In this invention, the temperature of the third reaction is preferably 80-120°C, more preferably 85-100°C, and even more preferably 90°C; the time of the third reaction is preferably 48-240h, more preferably 72-192h, and even more preferably 120h.

[0075] In this invention, after the third reaction is completed, the process further includes: filtering the obtained product and washing and drying the obtained filter cake;

[0076] The washing agent is preferably methanol.

[0077] The present invention also provides a method for preparing M-HOF materials, and the resulting M-HOF material.

[0078] In this invention, the inorganic metal center of the M-HOF material is a zinc ion, and the organic ligand is a pyridine-carboxylic acid ligand. The zinc ion is six-coordinated, including two nitrogen atoms from the pyridine-carboxylic acid ligand and four oxygen atoms from the coordinated water molecules. The pyridine in the pyridine-carboxylic acid ligand structure is coordinated with the zinc ion, and the carboxylic acid group remains exposed. Then, through intermolecular hydrogen bonds and π-π interactions, a three-dimensional network structure is formed.

[0079] This invention also provides an application of M-HOF material in hydroxide ion recognition.

[0080] Preferably, in the application of the above-mentioned M-HOF material in hydroxide ion recognition, the method of application includes the following steps:

[0081] The M-HOF material was mixed with water to obtain a suspension; then the suspension was mixed with an aqueous hydroxide ion solution to obtain a mixed solution, and the mixed solution was detected by ultraviolet-visible absorption spectroscopy.

[0082] In this invention, the concentration of M-HOF material in the suspension is preferably 0.05-1 g / L, more preferably 0.1-0.5 g / L, and even more preferably 0.2 g / L.

[0083] In this invention, the M-HOF material, after being mixed with water, further includes: ultrasonication and sedimentation;

[0084] The duration of the ultrasound is preferably 0.5 to 2 hours, more preferably 0.7 to 1.5 hours, and even more preferably 1 hour.

[0085] The settling time is preferably 0.5 to 2 hours, more preferably 0.7 to 1.5 hours, and even more preferably 1 hour.

[0086] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments 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 without creative effort are within the scope of protection of the present invention.

[0087] Example 1

[0088] A method for preparing M-HOF material includes the following steps:

[0089] Under argon protection, methyl 4-(N-hydroxyformamidinium)benzoate (3.8838 g, 0.02 mol), triethylamine (8.340 mL, 0.06 mol), and anhydrous acetonitrile (50 mL) were uniformly mixed; then isonicotinyl chloride hydrochloride (3.5602 g, 0.02 mol) was added in portions; after the addition was complete, the mixture was stirred at 85 °C for 12 h to obtain a pale yellow solid-liquid mixture; after quenching the reaction with 30 mL of saturated NaHCO3 solution, the mixture was extracted with dichloromethane to obtain a yellow organic phase, dried with anhydrous Na2SO4, and then evaporated to dryness. The mixture was then purified by silica gel column chromatography (eluent: petroleum ether and ethyl acetate in a volume ratio of 4:1) to obtain an intermediate product (5.2501 g, yield: 93.3%).

[0090] The intermediate product (1.4064 g, 5 mmol) was dissolved in a mixed solution of methanol (15 mL) and deionized water (15 mL), and then lithium hydroxide monohydrate (0.2622 g, 6.25 mmol) was added and mixed evenly. The mixture was heated to 85 °C and reacted for 12 h. After the reaction was completed, the pH was adjusted to ≤1 with hydrochloric acid. The product was obtained by rotary evaporation under reduced pressure, filtered, and the filter cake was washed three times with water and then dried to obtain pyridine-carboxylic acid ligand (1.2974 g, yield 97.1%).

[0091] The preparation of the above pyridine-carboxylic acid ligands is shown below:

[0092]

[0093] The pyridine-carboxylic acid ligand (26.7 mg, 0.1 mmol), zinc nitrate hexahydrate (29.7 mg, 0.1 mmol), N,N-dimethylformamide (1 mL), and deionized water (4 mL) were thoroughly mixed and heated to 90 °C for 120 h. After the reaction was completed, the product was filtered, and the filter cake was washed five times with methanol and then dried to obtain M-HOF material (28.5 mg, yield 42%).

[0094] The crystal structure data of the M-HOF material prepared in Example 1 are shown in Table 1.

[0095] Table 1 Crystal structure data of M-HOF material in Example 1

[0096]

[0097]

[0098] The single-molecule structure diagram and layered aggregation diagram of the M-HOF material prepared in Example 1 are shown below. Figure 1 and 2 As shown. By Figure 1 and 2It is known that the zinc ions in the M-HOF material are six-coordinated, containing two nitrogen atoms from the pyridine-carboxylic acid ligand and four oxygen atoms from the coordinated water molecules; the M-HOF material has a layered aggregate structure, which forms its three-dimensional stacked structure through intermolecular hydrogen bonds and π-π interactions.

[0099] The M-HOF material prepared in Example 1 was subjected to thermal analysis and XRD testing after being immersed in aqueous solutions with different pH values ​​for 3 days. The results are as follows: Figure 3 and 4 As shown. By Figure 3 and 4 It can be seen that M-HOF materials have good stability below 120℃ and good stability over a wide pH range.

[0100] Example 2

[0101] An application of an M-HOF material in recognizing hydroxide ions includes the following steps:

[0102] The M-HOF material prepared in Example 1 was ground and then added to deionized water to prepare a solution of 0.2 g / L. The solution was then sonicated for 1 hour and allowed to settle for 1 hour to obtain a stable suspension.

[0103] Add 0–20 μL of 0.05 mol / L sodium hydroxide aqueous solution to 2 mL of stable suspension, and detect the changes in its UV-Vis absorption spectrum. The results are as follows: Figure 5 As shown.

[0104] Depend on Figure 5 It can be seen that the absorption peak of the M-HOF suspension gradually increases at 249 nm while the absorption peak at 306 nm gradually decreases, indicating that the M-HOF material's detection electrode has a good recognition effect on sodium hydroxide. According to calculations, the recognized R... 2 =0.98872.

[0105] Example 3

[0106] An application of an M-HOF material in recognizing hydroxide ions is consistent with that in Example 2, except that sodium hydroxide is replaced with potassium hydroxide.

[0107] The UV-Vis absorption detection results of the M-HOF material for potassium hydroxide in Example 1 are as follows: Figure 6 As shown. By Figure 6 It can be seen that the working electrode of the M-HOF material has a good recognition effect on potassium hydroxide. According to calculations, the recognized R... 2 =0.97818.

[0108] Example 4

[0109] An application of an M-HOF material in recognizing hydroxide ions is consistent with that in Example 2, except that sodium hydroxide is replaced with lithium hydroxide.

[0110] The UV-Vis absorption detection results of the M-HOF material for lithium hydroxide in Example 1 are as follows: Figure 7 As shown. By Figure 7 It can be seen that the working electrode of the M-HOF material has a good recognition effect on lithium hydroxide. According to calculations, the recognized R... 2 =0.98378.

[0111] Example 5

[0112] The application of an M-HOF material in recognizing hydroxide ions is consistent with that in Example 2, except that sodium hydroxide is replaced with barium hydroxide, and the concentration of the barium hydroxide aqueous solution is 0.025 mol / L.

[0113] The UV-Vis absorption detection results of the M-HOF material for barium hydroxide in Example 1 are as follows: Figure 8 As shown. By Figure 8 It can be seen that the working electrode of the M-HOF material has a good recognition effect on barium hydroxide. According to calculations, the recognized R... 2 =0.98677.

[0114] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing M-HOF material, characterized in that, Includes the following steps: Methyl 4-(N-hydroxyformamidinium)benzoate, isonicotinyl chloride hydrochloride, triethylamine, and a first solvent were mixed and subjected to a first reaction to obtain an intermediate product; the structural formula of the intermediate product is as follows: ； The intermediate product, inorganic base, and second solvent are mixed to carry out the second reaction. After the second reaction is completed, the pH of the obtained product is adjusted to ≤1 to obtain the pyridine-carboxylic acid ligand. The pyridine-carboxylic acid ligand, zinc nitrate, N,N-dimethylformamide and water were mixed and subjected to a third reaction to obtain the M-HOF material.

2. The method for preparing M-HOF material according to claim 1, characterized in that, The molar ratio of methyl 4-(N-hydroxyformamidinium)benzoate, isonicotinyl chloride hydrochloride, and triethylamine is 1~2:1~2:1~6; The ratio of triethylamine to the first solvent is 0.5~2 mol: 1 L; The first solvent is acetonitrile.

3. The method for preparing M-HOF material according to claim 2, characterized in that, The conditions for the first reaction are: argon atmosphere, temperature 50~100℃, and time 6~18h.

4. The method for preparing M-HOF material according to claim 3, characterized in that, The molar ratio of the intermediate product to the inorganic base is 1:1~5; The inorganic base is lithium hydroxide, sodium hydroxide, or potassium hydroxide; The mass ratio of the intermediate product to the volume ratio of the second solvent is 1~2g:15~50mL; The second solvent is a mixed solution of alcohol and water; The volume ratio of alcohol to water in the second solvent is 1~3:1~3.

5. The method for preparing M-HOF material according to claim 4, characterized in that, The temperature of the second reaction is 85~95℃, and the reaction time is 8~16h.

6. The method for preparing M-HOF material according to claim 4 or 5, characterized in that, The molar ratio of the pyridine-carboxylic acid ligand to zinc nitrate is 1:0.5~2; The ratio of the pyridine-carboxylic acid ligand, N,N-dimethylformamide, and water is 0.2~1.8 mmol: 10 mL: 30~50 mL.

7. The method for preparing M-HOF material according to claim 6, characterized in that, The temperature of the third reaction is 80~120℃, and the time of the third reaction is 48~240h.

8. The M-HOF material prepared by the method according to any one of claims 1 to 7.

9. The application of the M-HOF material according to claim 8 in hydroxide ion recognition.

10. The application of the M-HOF material according to claim 9 in hydroxide ion recognition, characterized in that, The method of the application includes the following steps: The M-HOF material was mixed with water to obtain a suspension; then the suspension was mixed with an aqueous hydroxide ion solution to obtain a mixed solution, and the mixed solution was detected by ultraviolet-visible absorption spectroscopy.

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