A rare earth organic framework material for formaldehyde gas fluorescence detection and a preparation method thereof

Abstract

The application discloses a rare earth organic framework material for fluorescent detection of formaldehyde gas and a preparation method thereof. The rare earth organic framework material is an ordered microporous crystalline material, and a general structure formula of the material is [(CH3)2NH2]2[Ln6(mu3-OH)8(L-N2H3)6(H2O)6]*(G)7, wherein Ln is La 3+ , Nd 3+ , Eu 3+ , Gd 3+ , Tb 3+ or Tm 3+ , L-N2H3 is a chain dicarboxylic acid organic ligand with a hydrazine functional group, and G represents a solvent in a channel. The rare earth organic framework material is synthesized by a solvothermal method, and the synthesis method is simple, low in cost and mild in conditions. The rare earth organic framework material has characteristic emission of rare earth and fluorescence of a ligand, and can realize fluorescent enhancement type detection of formaldehyde gas. The probe is high in sensitivity, short in response time and high in specific selectivity, and is expected to be practically applied to the field of formaldehyde gas detection.

Description

Technical Field

[0001] This invention relates to a rare earth organic framework material and its preparation method, particularly a rare earth organic framework material and its preparation method for formaldehyde gas fluorescence detection. Background Technology

[0002] Formaldehyde is an important chemical and building material, widely used in the plastics, leather, synthetic fiber, dye, and detergent industries. Additionally, due to its preservative properties, it is used in the pharmaceutical field. However, due to its high reactivity, formaldehyde is highly toxic and carcinogenic, and is listed by the World Health Organization as the third largest indoor chemical pollutant. Excessive formaldehyde levels in the environment can affect human health, causing headaches, insomnia, and in severe cases, asthma, abnormal lung function, and immune dysfunction. Furthermore, studies have shown that patients with diabetes, lung cancer, Alzheimer's disease, and other diseases experience increased synthesis and metabolism of aldehydes in their blood, urine, and respiration. While the formaldehyde content in the exhaled breath of normal individuals is 0.2-0.8 ppb, it rises to 1.0-2.5 ppb in lung cancer patients. Therefore, formaldehyde can serve as a biomarker for lung cancer.

[0003] Currently, many formaldehyde detection methods have been developed, such as gas chromatography, colorimetry, and electrochemical methods. However, these methods all have drawbacks, such as high operational requirements, high cost, numerous limitations, and complex detection processes, making them unsuitable for real-time formaldehyde detection. Fluorescence detection methods, with their advantages of simple operation, real-time detection, high sensitivity, and good selectivity, have attracted widespread attention. Currently, the main detection mechanisms for formaldehyde include the condensation reaction of amino groups with formaldehyde, the condensation reaction of hydrazine groups with formaldehyde, and the reaction of naphthimide dyes with formaldehyde. However, these reported methods primarily detect formaldehyde solutions, are susceptible to interference, have low accuracy, and long reaction times, making them unsuitable for real-time formaldehyde detection. Therefore, there is a strong need to develop a sensitive, rapid, accurate, and selective formaldehyde gas probe applicable to biological and environmental detection. Summary of the Invention

[0004] One objective of this invention is to provide a rare-earth organic framework material and its preparation method that has high sensitivity, fast response speed, high selectivity, and can realize real-time fluorescence detection of formaldehyde gas.

[0005] To achieve the above objectives, the rare-earth organic framework material for formaldehyde gas fluorescence detection of the present invention is an ordered microporous crystalline material with the general structural formula [(CH3)2NH2]2[Ln6(μ3-OH)8(L-N2H3)6(H2O)6]*(G)7, where Ln is La 3+ 、Nd 3+ Eu 3+ Gd3+ 、Tb 3+ or Tm 3+ L-N2H3 is a chain-like dicarboxylic acid organic ligand with a hydrazine functional group, and G represents the solvent in the pore.

[0006] The L-N2H3 mentioned above can be 2-hydrazino-terephthalic acid, 2,5-dihydrazino-terephthalic acid, 2,3,4,5-tetrahydrazino-terephthalic acid, 2-hydrazino-[1,1'-biphenyl]-4,4'-dicarboxylic acid, or 2'-hydrazino-[1,1':4',1”-terphenyl]-4,4”-dicarboxylic acid.

[0007] The preparation method of the rare-earth organic framework material for formaldehyde gas fluorescence detection of the present invention adopts a solvothermal method, and the specific steps are as follows:

[0008] Rare earth salts and organic ligands containing carboxylic acids (preferably in a molar ratio of 0.5-1:1) are dissolved together in an organic solvent. Then, deionized water, o-fluorobenzoic acid, and nitric acid are added. Preferably, the molar ratio of o-fluorobenzoic acid to the organic ligand is 5-8:1, and the volume ratio of the organic solvent, deionized water, and nitric acid is 60-80:12:1. After thorough mixing, the mixture is transferred to a reaction vessel such as a screw-top glass bottle and reacted at 95-125°C for 1-3 days. The mixture is then allowed to cool naturally to room temperature, washed, and dried to obtain a rare earth organic framework material for formaldehyde gas fluorescence detection.

[0009] In this invention, the rare earth salt can be lanthanum nitrate, neodymium nitrate, europium nitrate, gadolinium nitrate, terbium nitrate, or thulium nitrate.

[0010] In this invention, the organic ligand containing carboxylic acid is 2-hydrazino-terephthalic acid, 2,5-dihydrazino-terephthalic acid, 2,3,4,5-tetrahydrazino-terephthalic acid, 2-hydrazino-[1,1'-biphenyl]-4,4'-dicarboxylic acid, or 2'-hydrazino-[1,1':4',1”-terphenyl]-4,4”-dicarboxylic acid, with the structural formulas corresponding to (a) to (e) below.

[0011]

[0012] In the preparation process of this invention, the organic solvent used can be any one or a mixture of several of N,N-dimethylformamide, N,N-dimethylacetamide, methanol, ethanol and tetrahydrofuran in any proportion.

[0013] The beneficial effects of this invention are as follows:

[0014] 1. The rare earth organic framework material preparation method of the present invention is simple and has a high yield. The obtained rare earth organic framework material has a face-centered cubic structure, high crystallinity, and good stability, and can maintain its structural integrity under conditions such as organic solvents (N,N-dimethylformamide, N,N-dimethylacetamide, methanol, ethanol, and tetrahydrofuran) and air.

[0015] 2. The rare-earth organic framework material prepared by this invention simultaneously exhibits the characteristic emission of rare-earth elements and the fluorescence of ligands. The luminescence performance of this material is highly dependent on formaldehyde content, enabling fluorescence-enhanced detection of formaldehyde gas. It has a fast response speed, reaching stability within 30 seconds, strong anti-interference ability, and the detection results are unaffected by external factors.

[0016] 3. The rare earth organic framework material prepared by this invention can exhibit significant fluorescence response at low formaldehyde concentrations (0-70 ppm), with large variations in emission peak intensity. Compared with other materials currently reported for formaldehyde gas detection, it has higher sensitivity and lower detection limits. Attached Figure Description

[0017] Figure 1 The figures show X-ray spectra of the simulated UiO-66, the synthesized fluorescent probes Tb-BDC-N2H3 and Eu-BDC-N2H3, respectively.

[0018] Figure 2 This is an electron microscope image of the fluorescent probe Tb-BDC-N2H3 synthesized in Example 1.

[0019] Figure 3 The image shows the fluorescence response spectrum of the fluorescent probe Tb-BDC-N2H3 synthesized in Example 1 when formaldehyde gas is added.

[0020] Figure 4 The image shows the fluorescence response spectrum of the fluorescent probe Eu-BDC-N2H3 synthesized in Example 2 when formaldehyde gas is added.

[0021] Figure 5 The selectivity of the fluorescent probe Eu-BDC-N2H3 synthesized in Example 3 for formaldehyde gas detection is shown. Detailed Implementation

[0022] Example 1

[0023] A highly stable rare-earth organic framework material, [(CH3)2NH2]2[Tb6(μ3-OH)8(BDC-N2H3)6(H2O)6]*(G)7 (abbreviated as Tb-BDC-N2H3), was synthesized via a solvothermal method using terbium nitrate hexahydrate and 2-hydrazinophthalic acid. The specific synthetic route is as follows:

[0024] 0.073 mmol of terbium nitrate hexahydrate, 0.073 mmol of 2-hydrazinophthalic acid, and 0.58 mmol of o-fluorobenzoic acid were dissolved in 3.65 ml of N,N-dimethylformamide. Then, 0.6 ml of deionized water and 0.05 ml of nitric acid were added, and the mixture was stirred until homogeneous. The mixture was then placed in a sealed 20 ml screw-top glass bottle and reacted in a constant temperature oven at 115 °C for 72 hours. After cooling to room temperature with the oven, the mixture was separated. The solid was washed three times with N,N-dimethylformamide to obtain the rare earth organic framework material Tb-BDC-N2H3, which was a reddish-brown transparent octahedron.

[0025] The X-ray spectrum of the rare-earth organic framework material Tb-BDC-N2H3 is shown in... Figure 1 Comparison with the simulated X-ray spectrum of UiO-66 indicates that the crystal structure of Tb-BDC-N2H3 is intact. Its scanning electron microscope image is shown below. Figure 2 As shown.

[0026] 2 mg of the fluorescent probe Tb-BDC-N2H3 was immobilized in a 25 ml glass bottle, and 1 μl of formaldehyde solution was added. The fluorescent probe Tb-BDC-N2H3 was not in direct contact with the formaldehyde solution. After a period of time, once the formaldehyde had evaporated to saturation, it was excited at 336 nm, and the fluorescence intensity of the fluorescent probe Tb-BDC-N2H3 was monitored. The fluorescence intensity at 544 nm increased to 6.89 times the initial value. Figure 3 The figures show the fluorescence spectra of the Tb-BDC-N2H3 fluorescent probe before and after contact with formaldehyde gas. As can be seen from the figures, the Tb-BDC-N2H3 fluorescent probe exhibits good detection performance for formaldehyde gas.

[0027] Example 2

[0028] A highly stable rare-earth organic framework material, [(CH3)2NH2]2[Eu6(μ3-OH)8(BDC-N2H3)6(H2O)6]*(G)7 (abbreviated as Eu-BDC-N2H3), was synthesized via a solvothermal method using europium chloride hexahydrate and 2-hydrazinophthalic acid. The specific synthetic route is as follows:

[0029] 0.073 mmol of europium chloride hexahydrate, 0.073 mmol of 2-hydrazinophthalic acid, and 0.58 mmol of o-fluorobenzoic acid were dissolved in 3.65 ml of N,N-dimethylformamide. Then, 0.6 ml of deionized water and 0.05 ml of nitric acid were added, and the mixture was stirred until homogeneous. The mixture was then placed in a sealed 20 ml screw-top glass bottle and reacted in a constant temperature oven at 110 °C for 48 hours. After cooling to room temperature with the oven, the mixture was separated. The solid was washed three times with N,N-dimethylformamide to obtain Eu-BDC-N2H3, a rare earth organic framework material for formaldehyde detection. The crystals were reddish-brown transparent octahedrons.

[0030] 2 mg of the fluorescent probe Eu-BDC-N2H3 was immobilized in a 25 ml glass bottle, and 1 μl of formaldehyde solution was added. The fluorescent probe Eu-BDC-N2H3 was not in direct contact with the formaldehyde solution. After a period of time, once the formaldehyde had evaporated to saturation, it was excited at 326 nm. The fluorescence intensity of the fluorescent probe Eu-BDC-N2H3 was monitored, and the fluorescence intensity at 613 nm increased to 2.81 times the initial value. Figure 4 The figures show the fluorescence spectra of the Eu-BDC-N2H3 fluorescent probe before and after contact with formaldehyde gas. As can be seen from the figures, the Eu-BDC-N2H3 fluorescent probe exhibits good detection performance for formaldehyde gas.

[0031] Example 3: Selectivity of Rare Earth Organic Framework Fluorescent Probes for Formaldehyde Gas Detection

[0032] A highly stable rare-earth organic framework material, Eu-BDC-N2H3, was synthesized via a solvothermal method using europium nitrate hexahydrate and 2-hydrazinophthalic acid. The specific synthetic route is as follows:

[0033] 0.073 mmol europium nitrate hexahydrate, 0.073 mmol 2-hydrazinophthalic acid, and 0.58 mmol o-fluorobenzoic acid were dissolved in 3.65 ml of N,N-dimethylformamide. Then, 0.6 ml of deionized water and 0.05 ml of nitric acid were added, and the mixture was stirred until homogeneous. The mixture was then placed in a sealed 20 ml screw-top glass bottle and reacted in a constant temperature oven at 105 °C for 72 hours. After cooling to room temperature with the oven, the mixture was separated. The solid was washed three times with N,N-dimethylformamide to obtain the rare earth organic framework material Eu-BDC-N2H3, which was a reddish-brown transparent octahedron.

[0034] Two mg of the fluorescent probe Eu-BDC-N2H3 was immobilized in 25 ml glass vials. One μl each of hexanal, formaldehyde, ethanol, acetone, and water were added. The fluorescent probe Eu-BDC-N2H3 was not in direct contact with these liquids. After a period of time, once the liquids had evaporated to saturation, the fluorescence emission spectrum was measured at an excitation wavelength of 326 nm. Figure 5 As shown in the figure, the results showed that only the fluorescent probe Eu-BDC-N2H3 showed a significant change in fluorescence intensity at 613 nm after contact with formaldehyde gas, indicating that the fluorescent probe Eu-BDC-N2H3 has good selectivity for formaldehyde gas.

[0035] In addition to 2-hydrazinophthalic acid, the organic ligand can also be any of 2,5-dihydrazinophthalic acid, 2,3,4,5-tetrahydrazinophthalic acid, 2-hydrazino-[1,1'-biphenyl]-4,4'-dicarboxylic acid, or 2'-hydrazino-[1,1':4',1”-terphenyl]-4,4”-dicarboxylic acid, all of which can achieve similar effects.

Claims

1. A rare-earth organic framework material for formaldehyde gas fluorescence detection, characterized in that, This rare-earth organic framework material is an ordered microporous crystalline material with the general structural formula [(CH3)2NH2]2[Ln6(μ3-OH)8(L-N2H3)6(H2O)6]*(G)7, where Ln is La 3+ 、Nd 3+ Eu 3+ Gd 3+ 、Tb 3+ or Tm 3+ L-N2H3 is a chain-like dicarboxylic acid organic ligand with a hydrazine functional group, and G represents the solvent in the pores; the material is prepared by the following method: a rare earth salt and an organic ligand containing a carboxylic acid are dissolved together in an organic solvent, and then deionized water, o-fluorobenzoic acid and nitric acid are added; after mixing evenly, the mixture is transferred to a reaction vessel and reacted at 95-125℃ for 1-3 days, and then naturally cooled to room temperature, washed and dried; The molar ratio of o-fluorobenzoic acid to organic ligand is 5-8:1; the molar ratio of rare earth salt to organic ligand containing carboxylic acid is 0.5-1:1; the organic ligand containing carboxylic acid used is 2-hydrazino-terephthalic acid with structural formula (a), 2,5-dihydrazino-terephthalic acid with structural formula (b), 2,3,4,5-tetrahydrazino-terephthalic acid with structural formula (c), 2-hydrazino-[1,1'-biphenyl]-4,4'-dicarboxylic acid with structural formula (d), or 2'-hydrazino-[1,1':4',1''-terphenyl]-4,4''-dicarboxylic acid with structural formula (e); 。 2. The method for preparing the rare-earth organic framework material for formaldehyde gas fluorescence detection as described in claim 1, characterized in that, Includes the following steps: Rare earth salts and organic ligands containing carboxylic acids are dissolved together in an organic solvent, and then deionized water, o-fluorobenzoic acid and nitric acid are added. After mixing evenly, the mixture is transferred to a reaction vessel and reacted at 95-125℃ for 1-3 days. Then it is naturally cooled to room temperature, washed and dried. The molar ratio of o-fluorobenzoic acid to organic ligands is 5-8:

1.

3. The method for preparing rare-earth organic framework materials for formaldehyde gas fluorescence detection according to claim 2, characterized in that, The rare earth salts used are lanthanum nitrate, neodymium nitrate, europium nitrate, gadolinium nitrate, terbium nitrate, or thulium nitrate.

4. The method for preparing rare-earth organic framework materials for formaldehyde gas fluorescence detection according to claim 2, characterized in that, The organic solvent used is any one or a mixture of several of N,N-dimethylformamide, N,N-dimethylacetamide, methanol, ethanol and tetrahydrofuran in any proportion.

5. The method for preparing rare-earth organic framework materials for formaldehyde gas fluorescence detection according to claim 2, characterized in that, The volume ratio of organic solvent, deionized water and nitric acid is 60-80:12:

1.

6. A formaldehyde gas probe, characterized in that, The material contains the material as described in claim 1 or the material prepared by the method described in any one of claims 2-5.

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