Ga-based metal organic framework material for detecting sarin simulant as well as preparation method and application of Ga-based metal organic framework material

Abstract

The invention discloses a Ga-based metal organic framework material for detecting sarin simulants and a preparation method and application thereof, the material takes N, N '-di-(isophthalic acid)-1, 2, 6, 7-tetrachloroperylene-3, 4, 9, 10-tetracarboxylic diimine as an organic ligand, the organic ligand and metal Ga < 3 + > are synthesized under solvothermal conditions, and the Ga-based metal organic framework material shows excellent thermal stability and chemical stability. The material shows different degrees of fluorescence opening response to a nerve agent sarin simulant-diethyl chlorophosphate in solvents with different polarities, the response time is extremely short (less than 10 s), the fluorescence detection limit can reach 4.44 ppb, and the material has extremely high sensitivity and shows remarkable selective recognition capability and cyclic test capability to diethyl chlorophosphate. According to the material, detection and analysis of trace diethyl chlorophosphate are achieved, the application range of the metal organic framework material based on the perylene bisimide derivative in the field of nerve poison detection is widened, and a new design thought and theoretical basis are provided for development of efficient and sensitive fluorescent sensing materials.

Description

Technical Field

[0001] The invention belongs to the field of metal organic framework material fluorescence sensing, and in particular relates to a metal organic framework material for detecting diethyl chlorophosphate, a nerve agent sarin simulant. Background Art

[0002] Sarin belongs to a class of organophosphorus nerve agents with high toxicity and rapid lethality. Sarin irreversibly inhibits the activity of acetylcholinesterase (AChE), causing abnormal accumulation of the neurotransmitter acetylcholine in the synaptic cleft, ultimately triggering neurological disorders and leading to respiratory failure and even death. To address this potential threat, the development of rapid, sensitive, and portable sarin detection technologies has become a research priority in the field of chemical defense. Existing detection methods include gas chromatography (GC), ion mobility spectrometry (IMS), surface-enhanced Raman spectroscopy (SERS), colorimetry, and surface acoustic wave sensors. However, these technologies are often limited by complex equipment, long response times, insufficient sensitivity, and limited field applicability. In contrast, fluorescent probes, due to their high sensitivity, rapid response, ease of operation, and low cost, have become a research hotspot for the detection of sarin and its simulants.

[0003] Luminescent metal-organic frameworks (LMOFs) are a class of highly ordered crystalline porous materials self-assembled from metal nodes and organic ligands through coordination interactions. They combine the properties of organic fluorescence with the structural controllability of an inorganic framework. LMOFs, thanks to their tunable pore structure, excellent luminescence performance, and abundant functional modification sites, have demonstrated significant advantages in fluorescence sensing, particularly for the detection of metal ions, explosives, small biomolecules, and toxic gases. Recent studies have demonstrated that the optical response of LMOFs can be further enhanced by introducing chromophores with strong light absorption and excellent fluorescence stability. Perylene diimide (PDI), a representative aromatic diimide, has been widely used in fluorescence sensor design due to its excellent photothermal stability, π-conjugated structure, and highly tunable functional group modification capabilities. Embedding or modifying PDI within the MOF framework has the potential to achieve highly selective recognition of nerve agents and visual detection at low concentrations, expanding the application of LMOFs in hazardous chemical monitoring. Summary of the Invention

[0004] The purpose of the present invention is to provide a Ga-based metal-organic framework material (Ga-MOF) with a two-dimensional layered structure. This material is constructed by a solvothermal method and exhibits high sensitivity and excellent selectivity in detecting diethyl chlorophosphate (DCP), a simulant of the nerve agent sarin. It can achieve rapid response under liquid phase conditions and has good reusability.

[0005] To achieve the above objectives, the present invention provides a Ga-based metal-organic framework material comprising deep red rhombic crystals self-assembled from gallium nitrate hydrate and N,N'-di-(isophthalic acid)-1,2,6,7-tetrachloroperylene-3,4,9,10-tetracarboxylic acid diimide (PDICl4-4COOH) under DMF / H2O / HBF4 solvothermal conditions. The chemical formula is [(CH3)2NH2]3[Ga(PDICl4-4COOH)2(DMF)2(H2O)2], where (CH3)2NH2 is a guest cation (dimethylamine) that balances the negative charge of the framework, PDICl4-4COOH is N,N'-di-(isophthalic acid)-1,2,6,7-tetrachloroperylene-3,4,9,10-tetracarboxylic acid diimide, DMF is N,N-dimethylformamide, and H2O is a crystalline water molecule. The crystal structure of the material is monoclinic, the space group is C2 / C, and the unit cell parameters are: a=15.332 Å, b=10.439 Å, c=53.918 Å, α=γ=90°, β=91.52°, V=8627(3)Å 3 .

[0006] The PDICl4-4COOH compound introduces four chlorine atoms at the bay positions of the PDI backbone, effectively disrupting the π-π stacking interaction between the perylene cores, significantly improving its solubility and dispersibility in polar solvents. Furthermore, the compound incorporates two isophthalic acid groups at the imide positions of PDI, resulting in four carboxylic acid coordination sites suitable for metal ion coordination to form a stable MOF backbone. This compound not only retains the excellent photostability and fluorescence properties of PDI but also exhibits excellent structural modification capabilities, providing an ideal functional ligand platform for the subsequent construction of luminescent MOF materials.

[0007] The preparation method of the Ga-based metal organic framework material of the present invention comprises the following steps:

[0008] Step 1: Preparation of PDICl4-4COOH

[0009] 1,6,7,12-Tetrachloro-3,4,9,10-perylenetetracarboxylic dianhydride and 5-aminoisophthalic acid were heated in propionic acid at 150-160°C for 3-4 days. After the reaction, deionized water was added to the solution, causing a red precipitate to precipitate. The precipitate was collected by filtration and then washed several times with a mixture of methanol and water to remove residual propionic acid. The precipitate was dried in a vacuum drying oven to obtain a deep red crude product. The crude product was recrystallized from DMF to obtain a pure red powder, PDICl4-4COOH, with the following structural formula:

[0010]

[0011] Step 2: Preparation of Ga-based metal-organic framework materials

[0012] Gallium nitrate hydrate and PDICl₄-4COOH were placed in a glass bottle, and DMF, H₂O, and fluoroboric acid (HBF₄) were added. After ultrasonic treatment, the glass bottle was sealed with a polytetrafluoroethylene shell and heated in a constant temperature oven at 90–120°C for 3–4 days. After the reaction, deep red rhombus-shaped crystals were obtained by washing with DMF several times. These crystals were collected and dried to obtain a Ga-based metal-organic framework.

[0013] In the above step 1, the molar ratio of the 1,6,7,12-tetrachloro-3,4,9,10-perylenetetracarboxylic dianhydride to 5-aminoisophthalic acid is preferably 1:9-12.

[0014] In the above step 2, the molar ratio of the PDICl4-4COOH to the gallium nitrate hydrate is preferably 1:2-4.

[0015] In the above step 2, the volume ratio of DMF, H2O, and HBF4 is preferably 4-6:1:0.1-0.5.

[0016] The present invention also provides the use of the aforementioned Ga-MOF as a fluorescent probe for fluorescent detection of the nerve agent sarin simulant DCP in liquid phase. The Ga-MOF exhibits extremely high response sensitivity when detecting DCP, achieving significant changes in fluorescence intensity within a short period of time, making it suitable for rapid identification and quantitative analysis of low-concentration DCP. Furthermore, the fluorescent probe exhibits excellent selectivity and recyclability. Therefore, the Ga-MOF provided by the present invention is particularly suitable for efficient, sensitive, and visual sensing of the sarin simulant DCP in liquid phase environments, possessing significant practical value and broad application prospects.

[0017] The beneficial effects of the present invention are as follows:

[0018] 1. The organic ligand PDICl4-4COOH employed in this invention introduces four chlorine atoms at the bay positions of the perylene imide backbone, significantly weakening the intermolecular π-π stacking interaction, thereby effectively improving its solubility and dispersibility in polar solvents and facilitating the controlled growth of MOF crystals. Furthermore, the isophthalic acid structures introduced at both ends of the ligand provide four coordinated carboxylic acid sites, which not only retains excellent photostability and fluorescence properties but also possesses good metal ion coordination and structural tunability, providing an ideal functional platform for constructing high-performance fluorescent MOF materials.

[0019] 2. The Ga-MOF constructed in this invention uses PDICl4-4COOH as a fluorescent ligand, synthesized via a solvothermal method. It combines structural order with fluorescent activity, achieving spatial control of ligand stacking behavior and significantly improving fluorescence emission performance. In liquid phase, this Ga-MOF exhibits high sensitivity (4.44 ppb) and excellent selectivity for the sarin simulant DCP. It also exhibits rapid response speed and good repeatability, maintaining stable performance after multiple cycles of detection. This material has broad application prospects in areas such as rapid screening of nerve agents and public safety monitoring, significantly outperforming existing fluorescent sensing materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The PDICl4-4COOH prepared in Example 1 1 HNMR spectrum.

[0021] Figure 2 This is a crystal photograph of Ga-MOF prepared in Example 1.

[0022] Figure 3 This is the asymmetric unit diagram of the Ga-MOF prepared in Example 1.

[0023] Figure 4 is Ga in Ga-MOF prepared in Example 1 3+ The coordination environment diagram.

[0024] Figure 5 This is a stacking diagram of the Ga-MOF prepared in Example 1 along the b-axis and c-axis directions.

[0025] Figure 6 The PXRD patterns of the Ga-MOF prepared in Example 1 immersed in different solvents are shown.

[0026] Figure 7 This is the PXRD pattern of the Ga-MOF prepared in Example 1 immersed in an aqueous solution with a pH of 1 to 13.

[0027] Figure 8 Graphs showing the fluorescence spectra of Ga-MOF prepared in Example 1 in different solvents.

[0028] Figure 9 This is the fluorescence titration diagram of Ga-MOF prepared in Example 1 against DCP in DMF.

[0029] Figure 10 3 is a linear relationship diagram of the emission intensity of Ga-MOF prepared in Example 1 in DMF and the DCP concentration.

[0030] Figure 11This is the experimental diagram of the fluorescence sensing selectivity (a) and anti-interference performance (b) of the Ga-MOF prepared in Example 1 to DCP.

[0031] Figure 12 This is a fluorescence sensing cycle test diagram of Ga-MOF prepared in Example 1 to DCP.

[0032] Figure 13 This is a real-time emission intensity diagram of the Ga-MOF prepared in Example 1 after adding different concentrations of DCP. DETAILED DESCRIPTION

[0033] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs.

[0034] Example 1

[0035] Step 1: Preparation of PDICl4-4COOH

[0036] 1,6,7,12-Tetrachloro-3,4,9,10-perylenetetracarboxylic dianhydride (1.00 g, 1.89 mmol) and 5-aminoisophthalic acid (3.40 g, 18.9 mmol) were heated to 160°C in propionic acid (40 mL) for 3 days. After the reaction, 200 mL of water was added to the solution, and a red precipitate began to precipitate. The precipitate was collected by filtration and washed several times with a mixture of methanol and water (1:1 by volume) to remove residual propionic acid. The precipitate was then dried in a vacuum oven at 60°C for 24 hours to obtain a dark red crude product. The crude product was recrystallized from DMF to obtain pure red powder, PDICl4-4COOH, with a yield of 68.2%. The reaction equation is as follows:

[0037]

[0038] The structural characterization data of the obtained PDICl4-4COOH are: 1 HNMR(400 MHz, DMSO-D6) δ (ppm):13.50(s, 4H, COOH), 8.64(s, 4H), 8.60(s, 2H), 8.31(m, 4H), see Figure 1 .

[0039] Step 2: Preparation of Ga-MOF

[0040] Gallium nitrate hydrate (0.040 g, 0.156 mmol) and PDICl4-4COOH (0.066 g, 0.078 mmol) were placed in a 20 mL glass bottle. DMF (5 mL), H2O (1 mL), and HBF4 (160 µL) were then added. After ultrasonic treatment for 10 min, the glass bottle was sealed with a polytetrafluoroethylene shell and heated in a constant temperature oven at 120 °C for 3 days. After the reaction was completed, pure dark red rhombus-shaped crystals ( Figure 2 ), collected and dried to obtain Ga-MOF.

[0041] The transparent Ga-MOF crystals from this example were selected for single crystal X-ray diffraction (SCXRD) characterization. The results showed that the Ga-MOF is a two-dimensional layered Ga(III) metal-organic framework material with the chemical formula [(CH3)2NH2]3[Ga(PDICl4-4COOH)2(DMF)2(H2O)2], where (CH3)2NH2) is a guest cation dimethylamine that balances the negative charge of the framework, PDICl4-4COOH is N,N'-di-(isophthalic acid)-1,2,6,7-tetrachloroperylene-3,4,9,10-tetracarboxylic acid diimide, DMF is N,N-dimethylformamide, and H2O is a molecule of water of crystallization. From the perspective of framework connection construction, the crystal structure of the metal organic framework material is monoclinic, the space group is C2 / C, and the unit cell parameters are: a=15.332 Å, b=10.439 Å, c=53.918Å, α=γ=90°, β=91.52°, V=8627(3) Å 3 Its asymmetric unit consists of 1 Ga 3+ ion and two PDICl4-4COOH ligands ( Figure 3 ), each PDICl4-4COOH ligand is bound to 1 / 2 Ga 3+ Ionic coordination, in which the two ligands are arranged in parallel with a distance of 4.361 Å between the ligands. From the perspective of coordination mode, Ga1 and Ga2 ions have the same coordination environment, both of which are coordinated with the four carboxyl oxygens from the PDICl4-4COOH ligand to form a slightly distorted tetrahedral configuration ( Figure 4 ), Ga-O bond lengths range from 1.741 Å to 1.812 Å. 3+ Among the four ligands of ion coordination, the adjacent two ligands are stacked in parallel, and the distance between the ligands is 9.216 Å. Ga1 and Ga2 with the same coordination environment are stacked in an interlaced manner along the b-axis direction and extend in the a-axis direction, eventually forming a two-dimensional layered structure ( Figure 5 ).

[0042] The chemical stability of the Ga-MOF in this example was tested. It was immersed in eight different solvents (ACE, THF, IPA, EtOH, CH3OH, DMA, DMF, and H2O) for three days, followed by PXRD analysis. The results showed that the PXRD spectra of the samples after three days of immersion in various solvents were consistent with the simulated spectra, and the peak shape did not change significantly, indicating that the material has good solvent stability ( Figure 6 Since Ga-MOF has good stability in water, the fresh sample was further immersed in an aqueous solution with a pH of 1 to 13 for three days. The PXRD spectrum shows that the position of the powder diffraction peak of the sample after immersion is exactly the same as the simulated peak, indicating that Ga-MOF also has excellent acid and alkali stability ( Figure 7 ).

[0043] Example 2

[0044] Step 1 of this example was the same as Step 1 of Example 1. In Step 2 of this example, gallium nitrate hydrate (0.080 g, 0.312 mmol) and PDICl4-4COOH (0.066 g, 0.078 mmol) were placed in a 20 mL glass bottle. DMF (5 mL), H2O (1 mL), and HBF4 (160 µL) were then added. After ultrasonic treatment for 10 minutes, the glass bottle was sealed with a polytetrafluoroethylene shell and heated in a 120 °C constant temperature oven for 3 days. After completion of the reaction, the mixture was washed several times with DMF to obtain a deep red microcrystalline powder and rhombohedral crystals, which were then collected and dried to obtain Ga-MOF.

[0045] Application Example 1

[0046] Application of the Ga-MOF prepared in Example 1 as a fluorescent probe for fluorescence detection of the nerve agent sarin simulant DCP in liquid phase

[0047] 1. Fluorescence emission behavior of Ga-MOF in different organic solvents

[0048] The solid-state fluorescence properties of Ga-MOF were tested at room temperature and found to be weak, so no further analysis was performed. Under liquid phase conditions, 15 mg of Ga-MOF was dispersed in 2 mL of DMF and ultrasonicated to form a mother liquor. 30 µL of the mother liquor was mixed with 2.97 mL of organic solvents, including acetone (ACE), tetrahydrofuran (THF), isopropyl alcohol (IPA), ethanol (EtOH), methanol (CH3OH), N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMA), to a concentration of 0.075 mg·mL -1The fluorescence emission spectrum of Ga-MOF suspension was measured under 485 nm excitation. The results showed that the emission peak of Ga-MOF red-shifted with the increase of solvent polarity (545-554 nm, see Figure 8 ), and exhibits high fluorescence intensity in less polar solvents (such as CH3OH and THF), while it is significantly weakened in DMF and DMA. This behavior may be due to the dipole-dipole interaction between the perylene core and the highly polar solvent, which suppresses the radiative relaxation of the excited state, thereby reducing the luminescence efficiency.

[0049] 2. Fluorescent sensing behavior of Ga-MOF towards DCP in DMF

[0050] In view of the good dispersibility and crystal stability of Ga-MOF in DMF, DMF was selected as the detection medium and prepared at 0.075 mg·mL -1 Ga-MOF suspension was prepared. Different concentrations of DCP were gradually added to the Ga-MOF suspension to conduct fluorescence titration experiments to evaluate its sensing performance. Under 485 nm excitation, Ga-MOF exhibited a significant "fluorescence turn-on" effect on DCP: the fluorescence color increased from weak yellow to bright yellow, and the emission peak intensity was significantly improved ( Figure 9 When the DCP concentration reaches 10-15 ppm, the fluorescence enhancement tends to saturation. In the range of 0-5 ppm, the fluorescence intensity ratio (I / I0) at 545 nm shows a good linear relationship with the DCP concentration, and the fitting equation is I / I0 = 1.6013 [DCP] + 0.9603 ( Figure 10 ). According to the formula LOD = 3σ / K, the detection limit of Ga-MOF for DCP in DMF was calculated to be 4.44 ppb, showing excellent detection sensitivity.

[0051] 3. Evaluation of the specific response, response time and recycling performance of Ga-MOF to DCP in DMF

[0052] DMF was selected as the detection medium and prepared to 0.075 mg·mL -1 Ga-MOF suspension, 10 ppm DCP and 10 ppm organophosphorus compounds with similar structures to DCP were added to the Ga-MOF suspension, including diisopropyl methyl phosphate (DIMP), triethyl phosphate (TEP), tributyl phosphate (TBP), diethyl benzyl phosphate (DEBP), diethyl 2-bromoethylphosphonate (DEBEP) and diethyl cyanophosphate (DECP). The change in fluorescence intensity at 545 nm showed that the addition of DCP resulted in an approximately 8-fold fluorescence enhancement, and the addition of DECP resulted in an approximately 2-fold fluorescence enhancement, while the other analytes had no significant fluorescence changes ( Figure 11a), indicating that Ga-MOF has outstanding selectivity for DCP in DMF. Then, an equal amount of DCP was added to the above system, such as Figure 11 As shown in b, the fluorescence enhancement change of Ga-MOF is consistent with that without interference, indicating that it has good anti-interference performance. Subsequently, 10 ppm DCP was added to the Ga-MOF suspension to test its recyclability. To test the recycling performance, after each round of testing, the Ga-MOF was washed with DMF and centrifuged to recover it, and the test was repeated five times. The fluorescence intensity of Ga-MOF was restored in each round, showing good reusability ( Figure 12 In addition, under the action of different concentrations of DCP, the fluorescence intensity of Ga-MOF increases rapidly within 10 seconds and stabilizes within 70 seconds ( Figure 13 ), showing that it has a fast response and is suitable for real-time detection.

[0053] In summary, the Ga-MOF constructed in the present invention exhibits excellent performance in the detection of the sarin simulant DCP, with rapid response, high sensitivity, good selectivity and anti-interference ability, and good cyclic stability, showing its broad application prospects in the field of efficient identification and visual detection of nerve agents.

[0054] Finally, it should be noted that the above contents are only preferred embodiments of the present invention and are intended to illustrate the technical solutions of the present invention rather than to limit the present invention. For those skilled in the art, any modification, replacement, or equivalent adjustment of the above embodiments without departing from the core ideas and technical principles of the present invention shall be deemed to fall within the scope of protection of the present invention.

Claims

1. A Ga-based metal-organic framework material, characterized by: The chemical formula of the material is [(CH3)2NH2]3[Ga(PDICl4-4COOH)2(DMF)2(H2O)2], wherein (CH3)2NH2 is a guest cation dimethylamine radical that balances the negative charge of the framework, PDICl4-4COOH is N,N'-di-(isophthalic acid)-1,2,6,7-tetrachloroperylene-3,4,9,10-tetracarboxylic acid diimide, DMF is N,N-dimethylformamide, and H2O is a crystal water molecule; The crystal structure of the material is monoclinic, the space group is C2 / C, and the unit cell parameters are: a=15.332 Å, b=10.439 Å, c=53.918 Å, α=γ=90°, β=91.52°, V=8627(3) Å 3 .

2. A method for preparing the Ga-based metal-organic framework material according to claim 1, characterized in that: The method comprises the following steps: Step 1: Preparation of PDICl4-4COOH 1,6,7,12-tetrachloro-3,4,9,10-perylenetetracarboxylic dianhydride and 5-aminoisophthalic acid were heated in propionic acid at 150-160°C for 3-4 days. After the reaction, deionized water was added to the solution to precipitate a red precipitate. The precipitate was collected by filtration, washed with a mixture of methanol and water, and then vacuum-dried. It was then recrystallized from N,N-dimethylformamide to obtain PDICl4-4COOH, the structural formula of which is shown below: Step 2: Preparation of Ga-based metal-organic framework materials Gallium nitrate hydrate and PDICl4-4COOH are added to a mixture of DMF, H2O and HBF4, and after ultrasonic dispersion, the mixture is heated at 90-120 °C under closed conditions for reaction for 3-4 days. After the reaction, the mixture is washed with N,N-dimethylformamide and dried to obtain a Ga-based metal-organic framework material.

3. The method for preparing a Ga-based metal-organic framework material according to claim 2, wherein: In step 1, the molar ratio of 1,6,7,12-tetrachloro-3,4,9,10-perylenetetracarboxylic dianhydride to 5-aminoisophthalic acid is 1:9-12.

4. The method for preparing a Ga-based metal-organic framework material according to claim 2, wherein: In step 2, the molar ratio of the PDICl4-4COOH to gallium nitrate hydrate is 1:2-4.

5. The method for preparing a Ga-based metal-organic framework material according to claim 2, wherein: In step 2, the volume ratio of DMF, H2O, and HBF4 is 4-6:1:0.1-0.

5.

6. Use of the Ga-based metal-organic framework material according to claim 1 as a fluorescent probe for fluorescence detection of the nerve agent sarin simulant DCP in liquid phase.

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