Precious metal modified conductive MOF (Metal Organic Framework) material as well as synthesis method and application thereof
By introducing a composite metal-organic framework and noble metal nanoparticles into noble metal-modified conductive MOF materials, a two-dimensional conjugated and mesoporous structure is formed, which solves the problems of low conductivity, poor selectivity and insufficient chemical stability of traditional noble metal-modified conductive MOF materials in gas sensing processes, and realizes efficient, accurate identification and stable response to hydrogen sulfide gas at room temperature.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-15
- Publication Date
- 2026-03-27
AI Technical Summary
Traditional noble metal-modified conductive MOF materials suffer from low conductivity, poor selectivity, decreased sensitivity and accuracy, and insufficient chemical stability in gas sensing processes, especially under high temperature and high humidity conditions where performance degradation is severe.
By combining composite metal-organic frameworks with noble metal nanoparticles, and by controlling the size of the composite nanosheets and the mass ratio of noble metal to composite metal-organic frameworks, a two-dimensional conjugated and mesoporous structure is formed. Noble metal nanoparticles are uniformly loaded in the mesoporous structure, and gas sensing performance is improved by utilizing chemical sensitization and electronic sensitization functions.
It significantly improves gas sensing performance at room temperature, exhibits excellent selectivity and stability, can quickly identify and respond to hydrogen sulfide gas, and maintains stable and reliable performance during long-term use.
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Figure CN121740965A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of gas sensing, in particular to a noble metal modified conductive MOF material and a synthesis method and application thereof. BACKGROUND
[0002] With the development of intelligent sensors, gas sensors, as an important part of them, are widely used in environmental monitoring, industrial safety, medical health and other fields. Traditional semiconductor gas sensors mostly use metal oxide semiconductor (MOS) as the gas sensitive sensing material, but due to its high working temperature, it has problems such as high power consumption, poor stability, safety hazards, etc., which greatly limits the application scenarios. Metal organic framework (MOF) material is a kind of porous polycrystalline material formed by self-assembly of organic ligand and metal ion through coordination bond, which has large specific surface area, adjustable porous structure and metal active sites, and is beneficial to the interaction of gas molecules on its surface, and is a promising gas sensitive sensing material. However, the electrical conductivity of traditional MOF material is low, and it is difficult to effectively realize the conversion and output of electrical signal in the sensing process; and the traditional MOF material is easy to collapse under high temperature and high humidity conditions, resulting in poor recovery and performance decay, which seriously restricts its development and application in the field of gas sensing.
[0003] The noble metal modified conductive MOF material is constructed by a specific metal and an organic ligand with π conjugation property to expand the two-dimensional or three-dimensional conjugated skeleton. In this structure, the metal d orbital and the ligand π orbital electron coupling form electron delocalization, which gives the material high electrical conductivity. At the same time, its porous network and conjugated skeleton not only realize efficient charge transfer, but also provide abundant active sites, which provide a large number of adsorption sites for gas molecules and promote the interaction between gas molecules and the material. It overcomes the defect of low electrical conductivity of traditional MOF material, and also brings new opportunities for room temperature gas sensing. However, high electrical conductivity reduces the selectivity of the noble metal modified conductive MOF material to specific gases, resulting in decreased sensing sensitivity and accuracy, and poor gas sensitive sensing performance. Moreover, the chemical stability of the noble metal modified conductive MOF material is insufficient, and it is easy to undergo structure reconstruction under acidic or alkaline environment or potential induction, resulting in inactivation of active sites. SUMMARY
[0004] The present application aims to provide a noble metal modified conductive MOF material and a synthesis method and application thereof, to solve the problem of poor gas sensitive sensing performance of the existing noble metal modified conductive MOF material.
[0005] To achieve the above-mentioned purpose, the present application provides the following technical scheme: a noble metal modified conductive MOF material, comprising a composite metal organic framework and noble metal nanoparticles loaded on the composite metal organic framework, the chemical formula of the composite metal organic framework is: x Co 3-xHHTP2, where x is a positive number not greater than 3.
[0006] Furthermore, the composite metal-organic framework comprises multiple composite nanosheets, which are stacked in layers to form a mesoporous structure between them, and the noble metal nanoparticles are loaded in the mesoporous structure.
[0007] Furthermore, the average size of the composite nanosheets is limited to the range of 30nm-40nm; in the noble metal modified conductive MOF material, the mass ratio of the noble metal nanoparticles to the composite metal-organic framework is in the range of 1:(15-50).
[0008] Furthermore, in the noble metal-modified conductive MOF material, the molar ratio of copper to cobalt is 1:1, and the noble metal element is platinum or palladium.
[0009] This application also provides applications of the above-mentioned noble metal-modified conductive MOF materials, including in gas sensor applications.
[0010] Furthermore, this includes detecting hydrogen sulfide gas at room temperature.
[0011] This application also provides a method for synthesizing the above-mentioned noble metal-modified conductive MOF material, including the following steps: S1. Dissolve the organic ligand in an organic solution, add an organic base to the organic solution and stir until homogeneous, then add a mixture including copper ions and cobalt ions to the organic solution and stir until homogeneous to form a reaction solution; wherein the organic ligand is a conjugated hexahydroxytriphenyl. S2. Place the reaction solution in an oven and heat it at a temperature of 50℃-120℃. After the heat treatment is completed, take out the reaction solution and filter it to collect the precipitate. Dry the precipitate at a temperature of 40℃-80℃ to obtain a composite metal-organic framework. S3. The composite metal-organic framework is completely dissolved in deionized water, a noble metal salt solution is added, and the mixture is stirred thoroughly to form a mixed solution. Then a reducing agent is added, and a reduction reaction is carried out under continuous stirring. S4. The mixed solution is centrifuged to collect the precipitate, which is then washed and dried to obtain a noble metal-modified conductive MOF material.
[0012] Further, in step S3, the content of the noble metal salt in the noble metal salt solution is any value between 1 mg / mL and 3 mg / mL, and the noble metal salt is potassium tetrachloropalladium or chloroplatinic acid; The reducing agent is sodium borohydride or hydrazine hydrate.
[0013] Furthermore, in step S4, the drying temperature is controlled within the range of 60℃-80℃.
[0014] Further, in step S1, the molar concentration of the organic ligand in the reaction solution is limited to the range of 0.05 mol / L-0.2 mol / L, and the molar concentration of the copper ion is limited to the range of 0.012 mol / L-0.04 mol / L.
[0015] The beneficial effects of this invention are as follows: The noble metal-modified conductive MOF material provided in this application exhibits a two-dimensional conjugated and mesoporous structure in its composite metal-organic framework. This structure exposes a large number of active metal sites on its surface, promoting the uniform dispersion of noble metal nanoparticles within the mesoporous structure of the composite metal-organic framework. This results in the noble metal-modified conductive MOF material possessing both chemical and electronic sensitization properties. The chemical sensitization function gives the noble metal-modified conductive MOF material a stronger chemical affinity for specific gas molecules, enabling rapid recognition and chemical reaction. The electronic sensitization function enhances the electron transport efficiency within the noble metal-modified conductive MOF material, improving its electrical signal response speed and intensity. These two functions synergistically enhance the gas-sensing performance of the noble metal-modified conductive MOF material, allowing it to exhibit excellent gas-sensing characteristics even at room temperature. In particular, at room temperature, the material exhibits an extremely high response value to hydrogen sulfide gas, while also possessing excellent selectivity and stability, enabling accurate identification of hydrogen sulfide gas, and maintaining stable and reliable performance during long-term use.
[0016] The method for synthesizing noble metal-modified conductive MOF materials provided in this application effectively separates noble metal nanoparticles by utilizing the pore structure of MOF materials, preventing the nanoparticles from agglomerating and forming aggregates, thereby avoiding performance degradation caused by agglomeration. This mesoporous structure not only ensures uniform loading of noble metal nanoparticles but also significantly enhances the adsorption and dissociation capabilities of gas molecules on the material surface. This allows gas molecules to more easily enter the mesoporous structure inside the noble metal-modified conductive MOF material, fully contact and react with the noble metal nanoparticles, further improving the gas-sensing performance of the material. This provides a reliable material basis and technical support for the development of high-performance room-temperature gas sensors.
[0017] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description
[0018] Figure 1The images shown are SEM characterization images of the composite metal-organic framework materials shown in Examples 1-4 of this invention. Figure 2 This is a schematic diagram illustrating the synthesis principle of a composite metal-organic framework material according to an embodiment of the present invention; Figure 3 This is a schematic diagram illustrating the synthesis principle of a noble metal-modified conductive MOF material according to an embodiment of the present invention; Figure 4 These are schematic diagrams of XRD characterization of the composite metal-organic framework materials shown in Examples 1-4 of the present invention; Figure 5 This is an EDX elemental distribution diagram of the noble metal-modified conductive MOF material shown in Embodiment 3 of the present invention; Figure 6 This is an EDX elemental distribution diagram of the noble metal-modified conductive MOF material shown in Embodiment 5 of the present invention; Figure 7 This describes the gas-sensitive response characteristics of the noble metal-modified conductive MOF material shown in Embodiment 3 of the present invention. Figure 8 This describes the gas-sensitive response characteristics of the noble metal-modified conductive MOF material shown in Example 5 of the present invention. Figure 9 The variation of the gas-sensor response value of the noble metal-modified conductive MOF material shown in Example 3 of the present invention under different humidity conditions; Figure 10 The variation of the gas-sensor response value of the noble metal-modified conductive MOF material shown in Example 5 of the present invention under different humidity conditions; Figure 11 The results are the performance test results of the noble metal modified conductive MOF materials shown in Examples 3 and 5 of this invention during long-term use. Detailed Implementation
[0019] The technical solutions of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.
[0020] A preferred embodiment of this application shows a noble metal-modified conductive MOF material, which includes a composite metal-organic framework and noble metal nanoparticles loaded on the composite metal-organic framework. The chemical formula of the composite metal-organic framework is Cu. x Co 3-xHHTP2, where x is a positive number not greater than 3. Noble metals are uniformly distributed on the composite metal-organic framework. This composite metal-organic framework material has a periodic porous structure, which not only provides loading sites for noble metal nanoparticles but also ensures that these nanoparticles are uniformly dispersed on the composite metal-organic framework, making it an ideal carrier material. Noble metal modification, as one of the key means to improve the performance of gas-sensitive materials, also plays an important role in this material system. It can not only act as a catalyst to effectively reduce the reaction activation energy of target gas molecules but also significantly enhance the adsorption and dissociation capabilities of gas molecules on the material surface. These effects work together to enable this noble metal-modified conductive MOF material to exhibit excellent gas-sensing performance.
[0021] In one embodiment, such as Figure 1 As shown, the composite metal-organic framework comprises numerous composite nanosheets. These composite nanosheets are stacked in layers, forming a large number of mesoporous structures between them, within which noble metal nanoparticles are primarily loaded. During the synthesis of this noble metal-modified conductive MOF material, the mesoporous structures within the composite metal-organic framework act as nucleation sites for the noble metal nanoparticles. Through the dipole interaction between noble metal ions and oxygen groups in the composite metal-organic framework, the noble metal ions are effectively stabilized within the mesoporous structures. Subsequently, under the action of a reducing agent, the noble metal ions are reduced to noble metal nanoparticles, which are ultimately stably loaded within the mesopores of the composite metal-organic framework.
[0022] In one embodiment, to ensure the stability and reliability of the noble metal-modified conductive MOF material, the average size of the composite nanosheets is strictly limited. Specifically, the average size of the composite nanosheets needs to be controlled within the range of 30 nm to 40 nm. Within this size range, a large number of appropriately sized mesoporous structures can be formed in the composite metal-organic framework, providing sufficient loading space for the noble metal nanoparticles while ensuring that the mass ratio between the noble metal nanoparticles and the composite metal-organic framework is maintained within a reasonable range of 1:(15-50). In addition, the presence of a large number of mesoporous structures can also greatly promote the interaction between gas molecules and the material, further improving the gas-sensing performance of the material.
[0023] In one embodiment, the molar ratio of copper to cobalt in the composite metal-organic framework is precisely set to 1:1. In this and other embodiments, the noble metal element is limited to platinum or palladium to ensure the specific properties and functions of the material. A higher cobalt content is not necessarily better. The introduction of cobalt ions and an increase in their content do not cause the formation of impurity phases, but they do significantly weaken the intensity of their diffraction peaks. This phenomenon may be due to the different ionic radii of cobalt and copper ions; therefore, the introduction of cobalt ions into the organic framework structure may lead to a certain degree of lattice distortion. Furthermore, the random distribution of the two metal ions can, to some extent, disrupt the long-range order of the MOF crystal structure, thereby reducing the crystallinity of the material.
[0024] This application also provides applications of the above-mentioned noble metal-modified conductive MOF materials, including applications in the field of gas sensors. By utilizing their mesoporous structure and the properties of the loaded noble metal, they can achieve accurate detection and efficient identification of specific gases, thus promoting the development of gas sensing technology.
[0025] In one embodiment, this noble metal-modified conductive MOF material can be used for the accurate detection of hydrogen sulfide gas at room temperature. At room temperature, this noble metal-modified conductive MOF material exhibits excellent gas-sensitive response characteristics to hydrogen sulfide gas, enabling it to quickly and accurately detect the presence of hydrogen sulfide gas and changes in its concentration. This provides an effective means for related environmental monitoring and safety protection.
[0026] This application also provides a method for synthesizing the above-mentioned noble metal-modified conductive MOF material, which includes the following steps: S1. Dissolve the organic ligand in an organic solution, add an organic base to the organic solution and stir until homogeneous, then add a mixture including copper ions and cobalt ions to the organic solution and stir until homogeneous to form a reaction solution; wherein the organic ligand is a conjugated hexahydroxytriphenyl. S2. Place the reaction solution in an oven and heat it at 50℃-120℃. After the heating treatment is completed, remove the reaction solution and filter it. Collect the precipitate and dry it at 40℃-80℃ to obtain the composite metal-organic framework. S3. Completely dissolve the composite metal-organic framework in deionized water, add a noble metal salt solution and stir thoroughly to form a mixed solution, then add a reducing agent and continue stirring to carry out a reduction reaction to form a composite solution. S4. Centrifuge the mixed solution, collect the precipitate, wash and dry the precipitate to obtain the noble metal modified conductive MOF material.
[0027] Steps S1 and S2 employ traditional solvothermal synthesis techniques to synthesize composite metal-organic frameworks. The specific reaction principle is as follows: Figure 2 As shown, using copper and cobalt metal salts as the source of metal ions and conjugated hexahydroxytriphenyl (HHTP) as the organic ligand, a series of composite metal-organic framework materials with different copper and cobalt metal ion contents were synthesized by controlling the ratio of copper and cobalt ions during the synthesis process while ensuring that the total molar amount of metal ions remained constant, and reacting under heating conditions. Examples include Cu3HHTP2 and Cu... 2.5 Co0.5HHTP2, Cu 1.8 Co 1.2 HHTP2 and Cu 0.8 Co 2.2 HHTP2, etc. Regarding the selection of metal salts, metal acetate salts are preferred, such as copper acetate monohydrate and cobalt acetate tetrahydrate. These metal salts exhibit superior solubility in organic solvents, which facilitates the smooth progress of the synthesis reaction. Organic solvents can be one or more of methanol, ethanol, N,N-dimethylformamide (DMF), and acetone. Organic bases can be one of ammonia, triethylamine, tributylamine, dimethylethylenediamine, and isopropylethylenediamine.
[0028] Since copper and cobalt salts are more soluble in deionized water than in organic solvents, in step S1, the copper and cobalt salts are first dissolved in deionized water to form a mixture containing copper and cobalt ions. This mixture is then slowly added to the organic solution. This addition method helps the copper and cobalt ions to dissolve fully in the organic solvent, making the reaction solution more homogeneous and stable. Compared to directly adding the metal salts to the organic solution, this method effectively avoids the problem of uneven reaction caused by excessively high local concentrations. It also prevents potential problems such as reduced yield due to incomplete dissolution of the metal salts and uncertain metal ion content in the composite metal-organic framework product.
[0029] In step S2, the reaction solution is transferred to a Teflon liner, which is then placed inside the reactor. The entire reactor is then placed in an oven for heating to promote a complete reaction and ensure the successful synthesis of the composite metal-organic framework material. After heating, the reaction solution is allowed to cool naturally to room temperature before further processing to avoid structural damage or performance degradation caused by sudden temperature changes. The collected precipitate can also be washed multiple times by centrifugation with deionized water and acetone to remove surface impurities and unreacted raw materials. The main purpose of drying the precipitate in an oven is to thoroughly remove excess moisture and obtain a pure composite metal-organic framework material.
[0030] In step S3, such as Figure 3As shown, the synthesized composite metal-organic framework material (Cu) x Co 3-x The mesoporous structure in HHTP2 serves as a nucleation and growth site for noble metal nanoparticles, utilizing the interaction between noble metal ions and Cu. x Co 3-x The dipole interactions between the oxygen groups in HHTP2 effectively stabilize noble metal ions within the mesoporous structure. Then, using a reducing agent, the metal ions are reduced to metal nanoparticles, which are then loaded onto Cu. x Co 3-x A noble metal-modified conductive MOF material was obtained from the mesoporous structure of HHTP2. First, the noble metal salt was dissolved in deionized water to form a homogeneous noble metal salt solution. Then, the solution was slowly added to the composite metal-organic framework solution, and the two were thoroughly stirred to ensure uniform mixing. This prevented uneven distribution of the noble metal loaded on the composite metal-organic framework due to excessively high local noble metal concentrations, which could affect the overall performance of the noble metal-modified conductive MOF material.
[0031] In step S4, the purpose of repeatedly washing the collected precipitate is to thoroughly remove surface adsorbed or residual ionic impurities, ensuring the purity and performance stability of the final product.
[0032] In one embodiment, in step S3, the concentration of the noble metal salt solution is precisely limited to the range of 1 mg / mL to 3 mg / mL to ensure complete dissolution of the noble metal salt in subsequent operations. This ensures the loading efficiency of the noble metal in the composite material and lays the foundation for obtaining high-quality noble metal-modified conductive MOF materials. In this embodiment and other embodiments, potassium tetrachloropalladium, chloroplatinic acid, or their hydrated salts, which exhibit excellent solubility, are preferentially selected as the noble metal salt, enabling them to disperse rapidly and uniformly in the solution and creating favorable conditions for the subsequent full reaction with the composite metal-organic framework. Simultaneously, sodium borohydride or hydrazine hydrate can be selected as the reducing agent to ensure efficient reduction reaction, thereby ensuring that the noble metal is loaded onto the composite metal-organic framework in elemental form.
[0033] In one embodiment, in step S4, the drying temperature was controlled and limited to the range of 60℃-80℃. Drying within this temperature range ensures that excess moisture in the synthesized noble metal-modified conductive MOF material is removed sufficiently and rapidly, while avoiding structural damage and performance degradation caused by excessively high temperatures. This effectively guarantees the stability and reliability of the noble metal-modified conductive MOF material, providing a guarantee for its subsequent applications. In this embodiment and other embodiments, in step S1, the molar concentration of each component in the reaction solution was limited. The molar concentration of the organic ligand was strictly limited to the range of 0.05mol / L-0.2mol / L to ensure that the organic ligand can fully exert its bridging effect in the reaction and promote the stable formation of the composite metal-organic framework structure. Meanwhile, the molar concentration of copper ions is precisely limited to the range of 0.012 mol / L-0.04 mol / L to ensure that copper ions can fully react with other components in the reaction. This avoids incomplete reaction and low product yield due to excessively low concentration, and also avoids side reactions and affecting the purity and quality of the product due to excessively high concentration.
[0034] Example 1 S1. Weigh 65 mg of 2,3,6,7,10,11-hexahydroxytriphenyl (conjugated hexahydroxytriphenyl) and dissolve it in 5 mL of N,N-dimethylformamide solution. Add 0.12 mL of ammonia water to the organic solution and stir thoroughly until homogeneous to form solution A. Weigh 80 mg of copper acetate monohydrate and dissolve it in 5 mL of deionized water, stirring thoroughly until completely dissolved to obtain solution B. Then, mix solutions A and B and stir thoroughly to form the reaction solution.
[0035] S2. Transfer the above reaction solution to a Teflon liner, place the liner inside the reaction vessel, and then place the entire reaction vessel in an oven for heating at 85°C. After heating for 2 hours, allow the reaction solution to cool naturally to room temperature, remove the solution, filter it, and then wash the precipitate collected during filtration with deionized water and acetone by centrifugation. Finally, dry the precipitate at 60°C. The results are as follows. Figure 1 As shown in Figure a, a composite metal-organic framework with the chemical formula Cu3HHTP2 was obtained.
[0036] S3. Weigh 40 mg of the composite metal-organic framework obtained in step S2 and dissolve it completely in deionized water. Then add 2 mL of a 2.5 mg / mL hexachloroplatinic acid hexahydrate solution to the deionized water and stir thoroughly to form a mixed solution. Subsequently, add 3 mL of a 1 mg / mL sodium borohydride solution to the mixed solution and carry out the reduction reaction under continuous stirring.
[0037] S4. The above mixed solution is centrifuged to obtain and collect the precipitate. The precipitate is washed with deionized water by centrifugation. Then the precipitate is placed in a vacuum drying oven and dried at 70°C to obtain Pt-modified noble metal-modified conductive MOF material with the chemical formula Pt@Cu3HHTP2.
[0038] Example 2 The difference between this embodiment and Embodiment 1 is that in step S1, 53.4 mg of copper acetate monohydrate and 33.4 mg of cobalt acetate tetrahydrate are weighed and dissolved in 5 ml of deionized water, stirred thoroughly until completely dissolved, to obtain solution B. The results are as follows... Figure 1 As shown in Figure b, the composite metal-organic framework obtained in step S2 has the chemical formula Cu2CoHHTP2. The final Pt-modified noble metal-modified conductive MOF material has the chemical formula Pt@Cu2CoHHTP2.
[0039] Example 3 The difference between this embodiment and Embodiment 1 is that in step S1, 40 mg of copper acetate monohydrate and 50 mg of cobalt acetate tetrahydrate are weighed and dissolved in 5 ml of deionized water, stirred thoroughly until completely dissolved, to obtain solution B. The results are as follows... Figure 1 As shown in Figure c, the composite metal-organic framework obtained in step S2 has the chemical formula Cu. 1.5 Co 1.5 HHTP2. The final Pt-modified noble metal-modified conductive MOF material, such as... Figure 5 As shown, its chemical formula is Pt@Cu 1.5 Co 1.5 HHTP2.
[0040] Example 4 The difference between this embodiment and Embodiment 1 is that in step S1, 26.7 mg of copper acetate monohydrate and 66.7 mg of cobalt acetate tetrahydrate are weighed and dissolved in 5 ml of deionized water, stirred thoroughly until completely dissolved, to obtain solution B. The results are as follows... Figure 1 As shown in Figure d, the composite metal-organic framework obtained in step S2 has the chemical formula CuCo2HHTP2. The final Pt-modified noble metal-modified conductive MOF material has the chemical formula Pt@CuCo2HHTP2.
[0041] Example 5 S1. Weigh 65 mg of 2,3,6,7,10,11-hexahydroxytriphenyl (conjugated hexahydroxytriphenyl) and dissolve it in 5 mL of N,N-dimethylformamide solution. Add 0.12 mL of ammonia water to the organic solution and stir thoroughly until homogeneous to form solution A. Weigh 40 mg of copper acetate monohydrate and 50 mg of cobalt acetate tetrahydrate and dissolve them in 5 mL of deionized water. Stir thoroughly until completely dissolved to obtain solution B. Then, mix solution A and solution B and stir thoroughly to form the reaction solution.
[0042] S2. Transfer the above reaction solution to a Teflon liner, place the liner inside the reaction vessel, and then place the entire reaction vessel in an oven for heating at 85°C. After heating for 2 hours, allow the reaction solution to cool naturally to room temperature, remove the reaction solution, filter it, and then wash the precipitate collected during filtration with deionized water and acetone by centrifugation. Finally, dry the precipitate at 60°C to obtain a composite metal-organic framework with the chemical formula Cu. 1.5 Co 1.5 HHTP2.
[0043] S3. Weigh 40 mg of the composite metal-organic framework obtained in step S2 and dissolve it completely in deionized water. Then add 1.5 mL of a 2 mg / mL hexachloroplatinic acid hexahydrate solution to the deionized water and stir thoroughly to form a mixed solution. Subsequently, add 3 mL of a 1 mg / mL sodium borohydride solution to the mixed solution and carry out the reduction reaction under continuous stirring.
[0044] S4. Centrifuge the above mixed solution to obtain and collect the precipitate. Wash the precipitate with deionized water by centrifugation, then place the precipitate in a vacuum drying oven and dry it at 70°C. Figure 6 As shown, a Pd-modified noble metal-modified conductive MOF material with the chemical formula Pd@Cu was obtained. 1.5 Co 1.5 HHTP2.
[0045] Depend on Figure 1As can be seen, the composite metal-organic frameworks synthesized in Examples 1-4 are all composed of a large number of composite nanosheets stacked together. Furthermore, these composite nanosheets exhibit a typical layered aggregation structure, resulting in numerous and uniformly distributed mesoporous structures between them. In addition, the average size of these composite nanosheets is around 30-40 nm, which ensures that the size of the mesoporous structures formed in the composite metal-organic framework is suitable, providing ample loading space for noble metal nanoparticles. Simultaneously, it greatly promotes the interaction between gas molecules and the material, enhancing the gas-sensing performance of the noble metal-modified conductive MOF material.
[0046] from Figure 4 X-ray diffraction (XRD) analysis revealed that the Cu3HHTP2 synthesized in Example 1 exhibited distinct diffraction characteristic peaks at 4.6°, 9.6°, 12.6°, and 28.0°. These diffraction peaks correspond to the (100), (200), (210), and (001) crystal planes, respectively. Furthermore, the synthesized Cu3HHTP2 consisted of hexagonal two-dimensional sheets stacked parallel to the c-axis, with a space group of P6 / mmm, which is consistent with the MOF crystal structure characteristics reported in existing literature. Therefore, it can be inferred that the Cu3HHTP2 synthesized in Example 1 possesses a standard MOF crystal structure. Comparing the composite metal-organic frameworks synthesized in Examples 2 to 4 with the Cu3HHTP2 synthesized in Example 1, it was found that no new diffraction characteristic peaks were observed in the XRD patterns as cobalt ions were introduced and their content in the system gradually increased. This phenomenon strongly suggests that the introduction of cobalt ions did not lead to the formation of impurity phases; that is, throughout the synthesis process, cobalt ions were integrated into the crystal structure of Cu3HHTP2, forming a uniform composite metal-organic framework (MOF). However, with increasing cobalt ion content, the intensity of the diffraction peaks showed a significant weakening trend. This phenomenon may be due to two reasons: First, cobalt and copper ions have different ionic radii. When cobalt ions are introduced into the MOF structure, they may interfere with and distort the original lattice structure to a certain extent, causing lattice distortion. This lattice distortion disrupts the integrity of the crystal structure, affecting and weakening the intensity of the diffraction signal during X-ray diffraction. Second, copper and cobalt ions exhibit a random distribution within the MOF. This random distribution can disrupt the long-range order of the MOF crystal structure to some extent, interfering with the regular arrangement of the crystal structure and thus reducing the crystallinity of the material. The reduced crystallinity directly affects the intensity of the X-ray diffraction peaks, causing them to weaken.
[0047] from Figure 5 , Figure 6As can be clearly observed, in the Pt-modified and Pd-modified noble metal conductive MOF materials obtained in Examples 3 and 5, the noble metals platinum and palladium exhibit a uniform distribution. That is, the signals of the noble metals Pt and Pd are uniformly distributed throughout the entire noble metal-modified conductive MOF material region, without any obvious aggregation or segregation. This fully demonstrates that the noble metals platinum and palladium are uniformly loaded on the surface and inside the composite metal-organic framework material.
[0048] To test the gas-sensing performance of the noble metal-modified conductive MOF material, the noble metal-modified conductive MOF material obtained in Examples 1-5 above was used as the sensing material layer in a gas sensor. The fabrication method of this gas sensor is as follows: a. Take an appropriate amount of the noble metal-modified conductive MOF material obtained in Examples 1-5 and grind it thoroughly in an agate mortar until the powder particles are uniform. After grinding, add a small amount of deionized water and stir the powder thoroughly to disperse it evenly, thus obtaining a noble metal-modified conductive MOF material slurry.
[0049] b. Using a pipette, take an appropriate amount of slurry and drop it onto the electrode area of the Ag / Pd interdigitated electrode. The dimensions of the Ag / Pd interdigitated electrode are as follows: .
[0050] c. Place the interdigitated electrode containing the gas-sensitive material in a drying oven and dry it at 150°C for 24 hours to remove excess moisture from the sensitive material. Then, perform an aging treatment to obtain the gas sensor.
[0051] The gas-sensing performance of the gas sensor fabricated using the noble metal-modified conductive MOF material obtained in Examples 1-5 as the sensitive material layer was tested. Specifically, a dynamic testing method was used to test the gas-sensing performance of the noble metal-modified conductive MOF material obtained in Examples 1-5. The dynamic testing system was the CGS-MT optoelectronic integrated testing platform from Beijing Zhongju High-Tech Technology Co., Ltd. The testing platform mainly consists of four parts: a sensor data acquisition system, a temperature control system, a gas distribution system, and a testing chamber. During testing, the synthesized device was placed on the probe stage of the testing chamber. Air was used as the carrier gas, and a target gas of a specific concentration was introduced into the testing chamber using the dynamic gas distribution system. Simultaneously, real-time experimental data was collected and recorded through the data acquisition system. The formula for calculating the response value R is: ,in The change in resistance after the target gas is introduced. This is the baseline resistance value in air.
[0052] Depend on Figure 7It can be seen that the Pt-modified noble metal-modified conductive MOF material synthesized in Example 3 exhibits a response value as high as 336.8% to hydrogen sulfide gas at a concentration of 5 ppm at room temperature. This fully demonstrates that the Pt-modified noble metal-modified conductive MOF material possesses a keen sensing ability and significant response effect to low concentrations of hydrogen sulfide gas at room temperature. Figure 8 As can be seen, the Pd-modified noble metal-modified conductive MOF material synthesized in Example 5 exhibits a response value as high as 575.3% to hydrogen sulfide gas at a concentration of 5 ppm at room temperature. This demonstrates that the Pd-modified noble metal-modified conductive MOF material also possesses extremely excellent gas-sensing performance for hydrogen sulfide gas at room temperature. Therefore, the noble metal-modified conductive MOF material provided in this application demonstrates excellent sensing ability and response performance to low concentrations of hydrogen sulfide gas at room temperature, providing strong material support for the development of high-performance room-temperature hydrogen sulfide gas sensors.
[0053] Depend on Figure 9 It can be seen that with increasing humidity, the response value of the Pt-modified noble metal-modified conductive MOF material synthesized in Example 3 to hydrogen sulfide gas shows a certain decreasing trend. This phenomenon is mainly due to water molecules adsorbing onto the MOF material surface, thereby occupying the active sites that would otherwise be available for hydrogen sulfide gas adsorption. This reduces the number of adsorption sites, thus decreasing its adsorption capacity for hydrogen sulfide gas, ultimately reflected in a decrease in the response value. However, even in an extremely high humidity environment with a relative humidity as high as 97% RH, the response value of this Pt-modified noble metal-modified conductive MOF material can still maintain 81%. This indicates that the Pt-modified noble metal-modified conductive MOF material has good moisture resistance and can maintain effective detection of hydrogen sulfide gas under high humidity conditions. Figure 10 It can be seen that the response value of the Pd-modified noble metal-modified conductive MOF material synthesized in Example 5 to hydrogen sulfide gas under different humidity conditions changes similarly to that of the Pt-modified material, also decreasing with increasing humidity. However, under high humidity conditions of 97%RH, its response value is still relatively high at 351.1%. This fully demonstrates that the Pd-modified noble metal-modified conductive MOF material has excellent moisture resistance. Therefore, the noble metal-modified conductive MOF material provided in this application exhibits excellent sensing ability and response performance to low concentrations of hydrogen sulfide gas under different humidity conditions, providing strong material support for the development of high-performance room-temperature hydrogen sulfide gas sensors.
[0054] The long-term stability of the Pt-modified noble metal-modified conductive MOF material synthesized in Example 3 and the Pd-modified noble metal-modified conductive MOF material synthesized in Example 5 was tested and compared. Figure 11It is known that both Pt-modified noble metal conductive MOF materials and Pd-modified noble metal conductive MOF materials have good stability, which indicates that the noble metal-modified conductive MOF materials provided in this application generally have good long-term stability.
[0055] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0056] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.
Claims
1. A noble metal-modified conductive MOF material, characterized in that, This includes a composite metal-organic framework and noble metal nanoparticles supported on the composite metal-organic framework, wherein the chemical formula of the composite metal-organic framework is: Cu x Co 3-x HHTP2, where x is a positive number not greater than 3.
2. The noble metal-modified conductive MOF material as described in claim 1, characterized in that, The composite metal-organic framework comprises multiple composite nanosheets stacked in layers to form a mesoporous structure, in which the noble metal nanoparticles are loaded.
3. The noble metal-modified conductive MOF material as described in claim 2, characterized in that, The average size of the composite nanosheets is limited to the range of 30nm-40nm; in the noble metal modified conductive MOF material, the mass ratio of the noble metal nanoparticles to the composite metal-organic framework is in the range of 1:(15-50).
4. The noble metal-modified conductive MOF material as described in claim 2, characterized in that, In the noble metal-modified conductive MOF material, the molar ratio of copper to cobalt is 1:1, and the noble metal element is platinum or palladium.
5. The application of the noble metal-modified conductive MOF material according to any one of claims 1-4, characterized in that, Including applications in gas sensors.
6. The application of the noble metal-modified conductive MOF material according to claim 5, characterized in that, This includes the detection of hydrogen sulfide gas at room temperature.
7. The method for synthesizing the noble metal-modified conductive MOF material according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Dissolve the organic ligand in an organic solution, add an organic base to the organic solution and stir until homogeneous, then add a mixture including copper ions and cobalt ions to the organic solution and stir until homogeneous to form a reaction solution; wherein the organic ligand is a conjugated hexahydroxytriphenyl. S2. Place the reaction solution in an oven and heat it at a temperature of 50℃-120℃. After the heat treatment is completed, take out the reaction solution and filter it to collect the precipitate. Dry the precipitate at a temperature of 40℃-80℃ to obtain a composite metal-organic framework. S3. The composite metal-organic framework is completely dissolved in deionized water, a noble metal salt solution is added, and the mixture is stirred thoroughly to form a mixed solution. Then a reducing agent is added, and a reduction reaction is carried out under continuous stirring. S4. The mixed solution is centrifuged to collect the precipitate, which is then washed and dried to obtain a noble metal-modified conductive MOF material.
8. The synthesis method according to claim 7, characterized in that, In step S3, the content of the noble metal salt in the noble metal salt solution is any value between 1 mg / mL and 3 mg / mL, and the noble metal salt is potassium tetrachloropalladium or chloroplatinic acid; The reducing agent is sodium borohydride or hydrazine hydrate.
9. The synthesis method according to claim 7, characterized in that, In step S4, the drying temperature is controlled within the range of 60℃-80℃.
10. The synthesis method according to claim 7, characterized in that, In step S1, the molar concentration of the organic ligand in the reaction solution is limited to the range of 0.05 mol / L to 0.2 mol / L, and the molar concentration of the copper ion is limited to the range of 0.012 mol / L to 0.04 mol / L.