Sensing material based on cadmium metal organic framework, preparation method and application thereof

Abstract

The invention provides a sensing material based on a cadmium metal organic framework as well as a preparation method and application of the sensing material, and a chemical structural unit of the sensing material comprises cadmium ions and 2, 3-quinoline diformate anions; the preparation method at least comprises the following steps: adding 2, 3-quinolinedicarboxylic acid and cadmium salt into a mixed solvent, carrying out solvothermal reaction at 130-150 DEG C for 36-60 hours, and after the reaction is finished, cooling and separating to obtain the Cd-MOF sensing material. The Cd-MOF sensing material disclosed by the invention is good in stability and has high selectivity and high sensitivity to Fe < 3 + > ions, and the good stability and wide pH adaptability of the sensing material guarantee the reliable detection capability in different actual water samples; the bottleneck problem that sensitivity, selectivity, environmental applicability and on-site convenience of a traditional sensing technology are difficult to consider at the same time is systematically solved.

Description

Technical Field

[0001] This invention belongs to the field of chemical materials and sensing technology, and in particular relates to a sensing material based on a cadmium metal-organic framework, its preparation method and its application. Background Technology

[0002] With the development of industries such as mining, smelting, electroplating, and chemicals, and the continuous increase in electronic waste emissions, heavy metal pollution in water bodies is showing an increasingly serious trend of complex pollution. Heavy metal ions are non-degradable, easily accumulate in organisms, and are bioaccumulated through the food chain, causing multi-system toxicity to the nervous system, liver, kidneys, and bones. They have become a key target for global environmental pollution control and public health protection. To address this challenge, countries have established increasingly stringent concentration limits for more than twenty heavy metal ions, including lead, cadmium, chromium, nickel, copper, zinc, mercury, iron, and aluminum. This urgently requires new detection technologies that can simultaneously and rapidly screen multiple heavy metal components under field conditions, while also offering low-cost advantages.

[0003] However, currently used methods for heavy metal detection still have certain limitations. For example, while atomic absorption spectrometry, inductively coupled plasma mass spectrometry, and electrochemical anodic stripping spectroscopy offer microgram-per-liter detection accuracy in laboratory environments, these methods typically rely on large instruments, involve complex and time-consuming sample pretreatment processes, and require high-purity carrier gases and specialized personnel, making them unsuitable for rapid on-site response to sudden pollution incidents. On the other hand, while colorimetric strips and portable electrodes offer advantages such as ease of operation and portability, they are often affected by complex matrices in actual water sample testing and generally suffer from insufficient sensitivity and cross-response to different valence states and coexisting ions, leading to a high risk of misjudgment. These methods are insufficient to meet the trace detection requirements for heavy metal ions at the microgram-per-liter or even submicrogram-per-liter levels in scenarios such as drinking water.

[0004] In recent years, metal-organic frameworks (MOFs) have been considered an ideal sensing platform for overcoming the bottlenecks of existing detection technologies due to their tunable pore structure, easily functionalizable surface properties, and the ability to design multiple synergistic recognition sites. However, existing research has largely focused on the identification and detection of single heavy metal ions, lacking a systematic solution that can simultaneously ensure the material's water stability, anti-interference performance, and signal amplification in real-world water samples. Therefore, developing metal-organic framework sensors that are suitable for complex heavy metal pollution scenarios and possess both high selectivity and high sensitivity has become an important research direction in the field of environmental analysis.

[0005] Of particular concern is that iron ions, as a metallic element with high abundance in the Earth's crust and significant industrial emissions, often coexist in the form of Fe²⁺ / Fe³⁺ in acidic mine drainage or eutrophic water bodies. Their chemical reactivity allows them to catalyze the generation of hydroxyl radicals, which can damage aquatic ecosystems. Furthermore, excessive human intake may lead to health risks such as Parkinson's disease and cirrhosis. Therefore, the World Health Organization stipulates that the iron content in drinking water should not exceed 0.3 mg·L⁻¹. However, iron ions readily undergo hydrolysis, complexation, and redox transformations between different valence states. Traditional detection methods typically rely on external masking agents and complex acid-base adjustment steps, which can easily introduce significant errors in rapid on-site detection.

[0006] Therefore, there is an urgent need to develop a novel metal-organic framework sensing material that can achieve single-target recognition of iron ions and has high sensitivity response characteristics, in order to fill the technological gap in rapid monitoring of iron ions in complex matrices. Summary of the Invention

[0007] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a sensing material based on a cadmium metal-organic framework, its preparation method and its application, to solve the problem that the sensing materials in the prior art are difficult to achieve simple, highly selective and highly sensitive on-site rapid detection of iron ions in complex water bodies.

[0008] To achieve the above and other related objectives, the present invention provides a sensing material based on a cadmium metal-organic framework, wherein the chemical structural units of the sensing material include cadmium ions and 2,3-quinoline dicarboxylate anions.

[0009] Preferably, there is π-π stacking among the quinoline groups in the 2,3-quinoline dicarboxylate anion ligand of the sensing material.

[0010] Preferably, the sensing material belongs to the monoclinic crystal system, P2 1 / c Space group.

[0011] This invention also provides a method for preparing a cadmium metal-organic framework-based sensing material, the method comprising at least the following steps:

[0012] 2,3-quinolinedicarboxylic acid and cadmium salt were added to a mixed solvent and subjected to a solvothermal reaction at 130-150℃ for 36-60 h. After the reaction was completed, the mixture was cooled and separated to obtain the Cd-MOF sensing material.

[0013] Preferably, the molar ratio of 2,3-quinolinedicarboxylic acid to cadmium salt is 1:1 to 1:3.

[0014] Preferably, the cadmium salt is selected from one or a combination of cadmium nitrate, cadmium chloride, cadmium sulfate, and cadmium acetate.

[0015] Preferably, the mixed solvent is a mixture of an organic solvent and deionized water, wherein the volume ratio of the organic solvent to the deionized water is 1:1 to 1:6, and the organic solvent is selected from one or a combination of acetonitrile, N,N-dimethylformamide, methanol, and ethanol.

[0016] Preferably, the preparation method of the 2,3-quinolinedicarboxylic acid is as follows:

[0017] 1,2-Phenylacetamine and dimethyl terephthalate were mixed in a molar ratio of 1:1 to 1:1.5, a catalyst and an organic solvent were added, and the mixture was reacted at 90 to 120 °C for 10 to 36 h to obtain an intermediate.

[0018] The intermediate was subjected to alkaline hydrolysis at 90-120°C for 1-24 hours to obtain 2,3-quinolinedicarboxylic acid.

[0019] Preferably, the catalyst is selected from one or a combination of triethylamine, pyridine, N,N-diisopropylethylamine, and potassium carbonate.

[0020] Preferably, the organic solvent is selected from one or a combination of ethanol, isopropanol, acetonitrile, DMF, and DMSO.

[0021] In addition, this invention also provides an application of a cadmium metal-organic framework-based sensing material, which is used as a fluorescent sensing probe for detecting Fe. 3+ The sensing material is either the cadmium metal-organic framework-based sensing material described above, or a cadmium metal-organic framework-based sensing material prepared using the above-described preparation method.

[0022] As described above, the cadmium-based metal-organic framework sensing material, its preparation method, and its application of the present invention have the following beneficial effects:

[0023] The Cd-MOF sensing material in this invention exhibits good stability and is effective against Fe. 3+ The ions exhibit high selectivity and sensitivity, constructing a stable framework for the monoclinic P21 / c space group through 2,3-quinoline dicarboxylate anion ligands with π-π stacking interactions. When Fe... 3+ After coordinating with the carboxylic acid group and quinoline nitrogen atom in the ligand, the π-π stacking is disrupted, resulting in a significant enhancement of fluorescence intensity and achieving highly sensitive and selective detection of Fe³⁺. Furthermore, this sensing material maintains stable fluorescence performance and detection capability over a wide pH range, making it suitable for practical detection needs under different environmental conditions.

[0024] The raw materials for preparing the Cd-MOF sensing material in this invention are readily available. Synthesized through a mild and controllable solvothermal process, it boasts advantages such as high yield, low cost, and good reproducibility, making it suitable for large-scale production. The detection method based on this sensing material is simple to operate, requiring no complex sample pretreatment or large equipment support, significantly reducing detection costs and operational barriers. Simultaneously, the good stability and wide pH adaptability of the sensing material ensure reliable detection capabilities in various actual water samples. This systematically solves the bottleneck problem of traditional sensing technologies struggling to balance sensitivity, selectivity, environmental applicability, and on-site convenience, providing a reliable and efficient solution for rapid on-site screening in fields such as environmental water quality monitoring and industrial emission control. Attached Figure Description

[0025] Figure 1 The diagram shows the crystal structure of the Cd-MOF sensing material in Embodiment 1 of the present invention.

[0026] Figure 2 The diagram shows a 3D structural schematic of the Cd-MOF sensing material in Embodiment 1 of the present invention.

[0027] Figure 3 The image shown is a thermogravimetric analysis diagram of the Cd-MOF sensing material in Example 1 of this invention.

[0028] Figure 4 The image shows a bar chart of the fluorescence intensity of the Cd-MOF sensing material for different metal ions in Example 1 of this invention.

[0029] Figure 5 The image shows a dotted line graph of the fluorescence intensity of the Cd-MOF sensing material in different concentrations of iron ions in Example 1 of this invention.

[0030] Figure 6 The image shows a dotted line graph of the fluorescence intensity of the Cd-MOF sensing material at different pH values ​​in Example 1 of this invention. Detailed Implementation

[0031] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0032] Before further describing specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terminology used in the embodiments of the present invention is for describing specific embodiments and not for limiting the scope of protection of the present invention. Test methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the respective manufacturers.

[0033] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. In addition to the specific methods, apparatus, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description of this invention, any prior art methods, apparatus, and materials similar to or equivalent to those described, apparatus, and materials in the embodiments of this invention may be used to implement the present invention.

[0034] This invention provides a method for preparing a cadmium metal-organic framework-based sensing material, the method comprising at least the following steps:

[0035] 2,3-quinolinedicarboxylic acid (H2QDA) and cadmium salt were added to a mixed solvent and subjected to a solvothermal reaction at 130-150℃ for 36-60 h. After the reaction was completed, the mixture was cooled and separated to obtain the Cd-MOF sensing material.

[0036] Specifically, the temperature of the solvothermal reaction can be any value within the range of 130℃, 135℃, 140℃, 145℃, 150℃, etc., and can be adjusted according to the actual situation. The time of the solvothermal reaction can be any value within the range of 36h, 42h, 48h, 54h, 60h, etc., and can be adjusted according to the actual situation.

[0037] As an example, the molar ratio of the 2,3-quinolinedicarboxylic acid to the cadmium salt is 1:1 to 1:3.

[0038] Specifically, the molar ratio of 2,3-quinolinedicarboxylic acid to cadmium salt can be any value within a range such as 1:1, 1:2, 1:3, etc., and can be adjusted according to actual conditions.

[0039] As an example, the cadmium salt is selected from one or a combination of cadmium nitrate, cadmium chloride, cadmium sulfate, and cadmium acetate.

[0040] Specifically, cadmium nitrate is preferably cadmium nitrate tetrahydrate (Cd(NO3)2·4H2O).

[0041] As an example, the mixed solvent is a mixture of an organic solvent and deionized water, wherein the volume ratio of the organic solvent to the deionized water is 1:1 to 1:6, and the organic solvent is selected from one or a combination of acetonitrile, N,N-dimethylformamide, methanol, and ethanol.

[0042] Specifically, the mixed solvent can be one or a combination of acetonitrile and deionized water, N,N-dimethylformamide and deionized water, methanol and deionized water, or ethanol and deionized water; the volume ratio of the organic solvent to deionized water can be any value within the range of 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, etc., and can be adjusted according to actual conditions.

[0043] As an example, the specific method for preparing the 2,3-quinolinedicarboxylic acid is as follows:

[0044] S11. Mix 1,2-phenylethylamine and dimethyl terephthalate in a molar ratio of 1:1 to 1:1.5, add a catalyst and an organic solvent, and react at 90 to 120°C for 10 to 36 hours to obtain an intermediate.

[0045] S12. The intermediate is subjected to alkaline hydrolysis at 90~120℃ for 1~24h to obtain 2,3-quinolinedicarboxylic acid.

[0046] Specifically, in step S11, the structural formula of 1,2-phenylethylamine is:

[0047] ;

[0048] The structural formula of dimethyl terephthalate is:

[0049] ;

[0050] The structural formula of the intermediate is:

[0051] .

[0052] In step S12, the structural formula of 2,3-quinolinedicarboxylic acid is:

[0053] .

[0054] Specifically, in step S11, the molar ratio of 1,2-phenylethylamine to dimethyl terephthalate can be any value within the range of 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, etc.; the reaction temperature can be any value within the range of 90℃, 100℃, 110℃, 120℃, etc.; and the reaction time can be any value within the range of 10h, 12h, 18h, 24h, 30h, 36h, etc., which can be adjusted according to the actual situation.

[0055] Specifically, the alkaline hydrolysis in step S12 involves hydrolyzing the intermediate in an alkaline solution. Preferably, the intermediate is mixed with NaOH, MeOH, and deionized water, and alkaline hydrolysis is carried out at 90~120℃ (e.g., 90℃, 100℃, 110℃, 120℃, etc.) for 1~24h (e.g., 1h, 6h, 12h, 18h, 24h, etc.). During alkaline hydrolysis, NaOH can be replaced with other alkaline solutions such as KOH; no specific limitation is made here. The addition of methanol (MeOH) during alkaline hydrolysis can adjust the polarity of the solution, and the methanol-water system is used to dissolve the reactants.

[0056] As an example, the catalyst is selected from one or a combination of triethylamine (N(CH2CH3)3), pyridine, N,N-diisopropylethylamine, and potassium carbonate.

[0057] As an example, the organic solvent is selected from one or a combination of ethanol (EtOH), isopropanol, acetonitrile, DMF, and DMSO.

[0058] The present invention also provides a sensing material based on a cadmium metal-organic framework, wherein the chemical structural unit of the sensing material comprises cadmium ions (Cd). 2+ ) and 2,3-quinoline dicarboxylate anion (BQDA) 2- ).

[0059] Specifically, the preparation of cadmium metal-organic framework (Cd-MOF) based sensing materials can be carried out using the above-mentioned preparation method for cadmium metal-organic framework based sensing materials, but it is not limited to this method, and other preparation methods can also be used as needed.

[0060] In a specific embodiment of the present invention, the sensing material is prepared directly using the above-described method for preparing cadmium-based metal-organic frameworks. This sensing material uses Cd as the metal center and 2,3-quinolinedicarboxylic acid (H2QDA) as the organic ligand, and is self-assembled under hydrothermal conditions. The structural formula of H2QDA is:

[0061] .

[0062] As an example, there is π-π stacking between quinoline groups in the 2,3-quinoline dicarboxylate anion ligand of the sensing material.

[0063] As an example, the sensing material belongs to the monoclinic crystal system, P2 1 / c Space group.

[0064] In addition, this invention also provides an application of a cadmium metal-organic framework-based sensing material, which is used as a fluorescent sensing probe for detecting Fe.3+ The sensing material is either the cadmium metal-organic framework-based sensing material described above, or a cadmium metal-organic framework-based sensing material prepared using the above-described preparation method.

[0065] Specifically, when Fe 3+ After entering the Cd-MOF channel, due to Fe 3+ It has a stronger coordination ability with the 2,3-quinolinedicarboxylic acid ligand (H2QDA), competitively displacing the coordination bond between Cd²⁺ and the ligand, leading to the dissociation of the MOF backbone. The organic ligand (H2QDA) originally locked within the MOF backbone is released, restoring its intrinsic strong fluorescence emission characteristics (i.e., releasing the strongly fluorescent organic ligand); furthermore...

[0066] When Cd-MOF and Fe 3+ Upon encountering the metal ion exchanger (MOF), Cd²⁺ is released from the MOF framework and may react with sulfur sources (such as H₂S, sulfides, etc.) in the system to generate cadmium sulfide (CdS) nanoparticles. CdS is a typical semiconductor fluorescent material, and its fluorescence properties differ from those of the organic ligand H₂QDA. This difference in fluorescence signal can be used for the quantitative detection of Fe. 3+ .

[0067] To better understand the sensing materials, preparation methods, and applications based on cadmium metal-organic frameworks in this invention, the following description, with reference to specific embodiments, illustrates the sensing materials, preparation methods, and applications based on cadmium metal-organic frameworks in this invention. It should be noted that these embodiments are merely descriptive and do not limit the invention in any way.

[0068] Example 1

[0069] This embodiment provides a method for preparing a cadmium metal-organic framework-based sensing material, the method comprising at least the following steps:

[0070] S1. Preparation of 2,3-quinolinedicarboxylic acid;

[0071] S11. Mix 1,2-phenylethylamine (2 mmol) with dimethyl terephthalate (2 mmol), add 0.8 mL of catalyst (N(CH2CH3)3) and 20 mL of organic solvent (EtOH), place in a polytetrafluoroethylene reactor, and react at 90 °C for 36 h to obtain an intermediate;

[0072] S12. The intermediate was mixed with NaOH (25 mmol), MeOH (5.0 mL) and deionized water (25.0 mL) and subjected to alkaline hydrolysis at 90 °C for 12 h to obtain 2,3-quinolinedicarboxylic acid (H2QDA).

[0073] S2. Add 0.04 mmol of 2,3-quinolinedicarboxylic acid and 0.10 mmol of cadmium salt (Cd(NO3)2·4H2O) to a mixed solvent (the mixed solvent consists of 12 mL of deionized water and 2 mL of acetonitrile). Place the resulting mixture in a polytetrafluoroethylene reactor and carry out a solvothermal reaction at 140 °C for 48 h. After the reaction is completed, cool and separate to obtain Cd-MOF sensing material.

[0074] The reaction flow chart for step S1 is as follows:

[0075]

[0076] This embodiment also provides a sensing material, which is prepared by the method for preparing a cadmium-metal-organic framework (Cd-MOF) sensing material in this embodiment. The chemical structural unit of this Cd-MOF sensing material includes cadmium ions (Cd ions). 2+ ) and 2,3-quinoline dicarboxylate anion (BQDA) 2- ).

[0077] Performance testing:

[0078] 1. X-ray single-crystal diffraction analysis was performed on the Cd-MOF sensing material prepared in this embodiment using a DX-2700BH X-ray diffractometer. A schematic diagram of the crystal structure of the Cd-MOF sensing material was drawn after analysis (see...). Figure 1 ) and 3D structural diagram (see Figure 2 ).

[0079] See Figure 1 This is a schematic diagram of the crystal structure of Cd-MOF, which belongs to the monoclinic P2 crystal system. 1 / c Space group; asymmetric unit containing 1 Cd 2+ 1 BQDA 2- Ligands and 2 water molecules, Cd 2+ It coordinates with four carboxylic acid oxygens (O1, O2, O5, O6) and two water oxygens (O3, O4) to form a trigonal bipyramidal configuration, with Cd-O bond lengths ranging from 2.292(2)–2.423(2) Å; the ligands connect to the Cd center to form a two-dimensional infinite network extending along the b and c axes, with a topology of 2,4-connected {8 122}{8}2.

[0080] See Figure 2To analyze and refine the single-crystal diffraction data, a 3D structural diagram of Cd-MOF was drawn using professional software. The diagram presents the atomic arrangement of the crystal in three-dimensional space from two perspectives: the a-axis and the c-axis. The diagram intuitively shows the microscopic crystal structure of Cd-MOF, including the coordination mode of the metal center Cd and the organic ligands, the topological network of the framework, and the possible pore orientation. As can be seen from the diagram, the benzo[g]quinoxaline luminescent groups in the layers are close to each other due to the confined space, resulting in π-π stacking, which leads to the self-quenching of the framework fluorescence.

[0081] 2. Thermogravimetric analysis was performed on the Cd-MOF sensing material prepared in this embodiment using a METTLER TG-DSC-1 thermogravimetric analyzer to investigate its stability at different temperatures. (See reference...) Figure 3 Thermogravimetric analysis curve of Cd-MOF, by Figure 3 It is known that Cd-MOF sensing materials lose two molecules of coordinated water at room temperature to 155℃, resulting in a weight loss of approximately 7.33%, compared to a theoretical value of 6.97%. The stable range of Cd-MOF sensing materials is 155℃ to 320℃, within which they exhibit excellent thermal stability and do not decompose. When the temperature exceeds 320℃, the framework structure begins to collapse.

[0082] 3. Ion selectivity of Cd-MOF sensing materials:

[0083] The optical properties of Cd-MOF sensing material in different heavy metal ions were determined. The specific steps included: dissolving 0.5 mg of Cd-MOF in 3.0 mL of water to prepare a bulk solution; then adding different heavy metal ions (Fe2+, Fe2+, Fe3 ...3+, Fe2+, Fe3+, Fe3+, Fe3+, Fe3+, Fe3+, Fe3+, Fe3+, Fe3+, Fe3+, Fe3 3+ Ag + Al 3+ Ba 2+ Ca 2+ Cd 2+ Co 2+ Cr 3+ Cu 2+ Fe 2+ Hg 2+ K + Li + Mg 2+ Na + Ni 2 + Pb 2+ Zn 2+ Fluorescence emission spectra were obtained at an excitation wavelength λex of 330 nm. Fluorescence intensity at the emission peak of 418 nm was plotted against different metal ions to obtain fluorescence spectra for different metal ions, as shown below. Figure 4 As shown.

[0084] See Figure 4 It can be seen that when Fe is added to the main solution 3+ Afterwards, the fluorescence significantly decreased, exhibiting a strong fluorescence quenching effect. However, upon the addition of several other metal ions, the fluorescence intensity remained essentially the same as that of Cd-MOF itself, showing no significant change. This indicates that Fe... 3+ The competitive mechanism between Fe and Cd in Cd-MOF, which releases luminescent ligands and weakens fluorescence, further indicates that Cd-MOF has high selectivity for iron ions. Even in the presence of multiple interfering ions at high concentrations (80 μM), Cd-MOF can still selectively target Fe. 3+ It produces a unique and remarkable fluorescence response, while other ions produce almost no interfering signal.

[0085] 4. Continuous titration of Cd-MOF sensing materials:

[0086] 0.5 mg of Cd-MOF was dissolved in 3.0 mL of water to prepare the main solution, and different concentrations of Fe were added. 3+ Fluorescence emission spectra were obtained at an excitation wavelength λex of 330 nm. The fluorescence intensity at the fluorescence emission peak of 418 nm was used to correlate different concentrations of Fe. 3+ Plotting the graphs revealed the presence of different concentrations of Fe in Cd-MOF. 3+ The continuous titration spectrum fluorescence intensity dot plot, such as Figure 5 As shown, the limit of detection (LOD) is 1.08 μM, indicating that this Cd-MOF sensing material is capable of detecting low concentrations of Fe. 3+ The goodness-of-fit of the standard curve is R² = 0.99213, indicating a good linear relationship suitable for quantitative analysis.

[0087] 5. pH stability of Cd-MOF sensing materials:

[0088] 0.5 mg of Cd-MOF was dissolved in 3.0 mL of water to prepare the main solution, and fluorescence emission spectra were obtained at an excitation wavelength λex of 330 nm. 0.5 mg of Cd-MOF was dissolved in 3.0 mL of water to prepare the main solution, and Fe was added... 3+ Fluorescence emission spectra were obtained at an excitation wavelength λex of 330 nm. Then, fluorescence intensity was plotted at the fluorescence emission peak at 418 nm to obtain a dot plot of fluorescence intensity from the continuous titration spectra of Cd-MOF with different concentrations of iron ions added, as shown below. Figure 6 As shown, Cd-MOF sensing materials exhibit stable performance at pH values ​​of 4–12, making them suitable for real-world aquatic environments with varying acidity and alkalinity.

[0089] Application Example 1

[0090] This application example demonstrates the use of a cadmium-based metal-organic framework sensing material as a fluorescence sensing probe for detecting Fe. 3+ The sensing material is a cadmium metal-organic framework-based sensing material prepared by the preparation method of Example 1.

[0091] Specifically, the cadmium-metal-organic framework-based sensing material prepared by the method in Example 1 was used as a fluorescent sensing probe and brought into contact with the water sample to be tested, allowing the Cd-MOF sensing material to react with Fe in the water sample. 3+ The reaction was performed; changes in the fluorescence signal of the reaction system were detected; finally, based on the changes in the fluorescence signal, the Fe content in the water sample was determined. 3+ The presence or absence of, or its concentration.

[0092] In summary, the Cd-MOF sensing material in this invention exhibits good stability and is effective against Fe. 3+ The ions exhibit high selectivity and sensitivity, constructing a stable framework for the monoclinic P21 / c space group through 2,3-quinoline dicarboxylate anion ligands with π-π stacking interactions. When Fe... 3+ After coordinating with the carboxylic acid group and quinoline nitrogen atom in the ligand, the π-π stacking is disrupted, resulting in a significant enhancement of fluorescence intensity and achieving highly sensitive and selective detection of Fe³⁺. Furthermore, this sensing material maintains stable fluorescence performance and detection capability across a wide pH range, making it suitable for practical detection needs under various environmental conditions. The raw materials used to prepare the Cd-MOF sensing material in this invention are readily available and synthesized through a mild and controllable solvothermal process, offering advantages such as high yield, low cost, and good reproducibility, making it suitable for large-scale production. The detection method based on this sensing material is simple to operate, requiring no complex sample pretreatment or large-scale equipment support, significantly reducing detection costs and operational barriers. Simultaneously, the good stability and wide pH adaptability of the sensing material ensure reliable detection capability in various actual water samples, systematically solving the bottleneck problem of traditional sensing technologies struggling to balance sensitivity, selectivity, environmental applicability, and on-site convenience. This provides a reliable and efficient solution for rapid on-site screening in fields such as environmental water quality monitoring and industrial emission control. Therefore, this invention effectively overcomes the various shortcomings of existing technologies and has high industrial application value.

[0093] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A sensing material based on a cadmium metal-organic framework, characterized in that, The chemical structural units of the sensing material include cadmium ions and 2,3-quinolinedicarboxylate anions.

2. The sensing material based on a cadmium metal-organic framework according to claim 1, characterized in that: In the sensing material, there is π-π stacking among the quinoline groups in the 2,3-quinoline dicarboxylate anion ligand.

3. The sensing material based on a cadmium metal-organic framework according to claim 1 or 2, characterized in that: The sensing material belongs to the monoclinic crystal system, P2 1 / c Space group.

4. A method for preparing a sensing material based on a cadmium metal-organic framework, characterized in that: The preparation method includes at least the following steps: 2,3-quinolinedicarboxylic acid and cadmium salt were added to a mixed solvent and subjected to a solvothermal reaction at 130-150℃ for 36-60 h. After the reaction was completed, the mixture was cooled and separated to obtain the Cd-MOF sensing material.

5. The method for preparing the cadmium-based metal-organic framework sensing material according to claim 4, characterized in that: The molar ratio of 2,3-quinolinedicarboxylic acid to the cadmium salt is 1:1 to 1:

3.

6. The method for preparing the cadmium-based metal-organic framework sensing material according to claim 4, characterized in that: The cadmium salt is selected from one or a combination of cadmium nitrate, cadmium chloride, cadmium sulfate, and cadmium acetate.

7. The method for preparing the cadmium-based metal-organic framework sensing material according to claim 4, characterized in that: The mixed solvent is a mixture of an organic solvent and deionized water, wherein the volume ratio of the organic solvent to the deionized water is 1:1 to 1:6, and the organic solvent is selected from one or a combination of acetonitrile, N,N-dimethylformamide, methanol, and ethanol.

8. The method for preparing the sensing material based on the cadmium metal-organic framework according to claim 4, characterized in that: The specific method for preparing the 2,3-quinolinedicarboxylic acid is as follows: 1,2-Phenylacetamine and dimethyl terephthalate were mixed in a molar ratio of 1:1 to 1:1.5, a catalyst and an organic solvent were added, and the mixture was reacted at 90 to 120 °C for 10 to 36 h to obtain an intermediate. The intermediate was subjected to alkaline hydrolysis at 90-120°C for 1-24 hours to obtain 2,3-quinolinedicarboxylic acid.

9. The method for preparing the cadmium-based metal-organic framework sensing material according to claim 8, characterized in that: Includes one or a combination of the following conditions: The catalyst is selected from one or a combination of triethylamine, pyridine, N,N-diisopropylethylamine, and potassium carbonate. The organic solvent is selected from one or a combination of ethanol, isopropanol, acetonitrile, DMF, and DMSO.

10. An application of a sensing material based on a cadmium metal-organic framework, characterized in that: The sensing material is used as a fluorescent sensing probe for detecting Fe. 3+ The sensing material is the cadmium metal-organic framework-based sensing material according to any one of claims 1 to 3, or the cadmium metal-organic framework-based sensing material prepared by any one of claims 4 to 9.

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