Preparation method of adaptive Au@Ti dual-functional core-shell MOF sensing material and adaptive Au@Ti dual-functional core-shell MOF sensing material

Abstract

The invention relates to the technical field of MOF sensing materials, and in particular to a preparation method of an adaptive Au@Ti bifunctional core-shell MOF sensing material and the adaptive Au@Ti bifunctional core-shell MOF sensing material. The method comprises the following steps: first, obtaining a gold nanoparticle solution; slowly dropping 0.5-3 parts by weight of an ethanol solution of 3-mercaptopropionic acid into the gold nanoparticle solution, stirring and reacting at room temperature for 4-6 hours, and dispersing the solution in 50-200 parts by weight of N,N-dimethylformamide; adding 5-20 parts by weight of tetraisopropyl titanate and 3-15 parts by weight of terephthalic acid to the dispersion, ultrasonically dispersing the solution, transferring the solution to an autoclave, and reacting the solution at 120-180°C for 12-48 hours; centrifuging and washing the reaction product, vacuum drying the solution at 60-80°C for 12-24 hours, grinding and sieving the solution, and performing activation treatment at 150-200°C and 0.1-1 kPa for 8-12 hours to obtain a product.

Description

Technical Field

[0001] The present invention relates to the technical field of MOF sensing materials, and in particular to a preparation method of an adaptive Au@Ti dual-functional core-shell MOF sensing material and the adaptive Au@Ti dual-functional core-shell MOF sensing material. Background Art

[0002] With the growing demand for highly sensitive and selective sensing technologies in areas such as food safety and health monitoring, the development of novel multifunctional sensing materials has become a research hotspot in materials science and sensing technology. Among the many emerging materials, metal-organic frameworks (MOFs) show great potential in sensing due to their high surface area, tunable pore structure, and abundant functionalized sites. However, single MOF materials still face challenges in practical applications, such as insufficient sensitivity, poor selectivity, and poor stability.

[0003] In recent years, researchers have attempted to combine MOFs with other functional materials in order to obtain composite sensing materials with better performance. Among them, the strategy of combining noble metal nanoparticles with MOFs has attracted widespread attention. This type of composite material attempts to utilize the plasmon resonance effect of noble metal nanoparticles to enhance the signal, while leveraging the molecular recognition ability of MOFs to improve selectivity. However, existing composite methods often find it difficult to achieve effective synergy between noble metal nanoparticles and MOFs. For example, simple physical mixing makes it difficult to control the spatial distribution of the two components, while directly growing metal nanoparticles in MOF pores can easily lead to MOF structural collapse or pore blockage.

[0004] Furthermore, existing composite sensing materials are mostly optimized for a single type of detection target (such as heavy metal ions or specific gas molecules), making it difficult to simultaneously meet multiple detection needs. In practical applications, it is often necessary to simultaneously monitor multiple different types of target substances, which requires sensing materials with multiple selectivities and tunable response mechanisms.

[0005] In view of the above situation, there is an urgent need to develop new composite sensing materials that can effectively integrate the advantages of precious metal nanoparticles and MOFs to achieve the synergistic effect of signal enhancement and highly selective recognition, while having the ability to detect multiple target substances and excellent stability. Summary of the Invention

[0006] The adaptive Au@Ti bifunctional core-shell MOF sensing material of the present invention is designed precisely to address this technological need. By carefully constructing a core-shell structure of a gold nanoparticle core and a titanium-based MOF shell, the present invention achieves an ordered spatial arrangement and effective interfacial contact of the two functional components. The gold core not only provides a strong plasmon resonance effect but also has the potential to regulate the electronic structure of the MOF through interfacial electron transfer. The titanium-based MOF shell provides efficient molecular recognition capabilities through controllable pore structure and surface chemistry, while also possessing unique photoresponsiveness. The interfacial effect between the two may generate new active sites, further enhancing the material's performance.

[0007] The object of the present invention is to provide a method for preparing an adaptive Au@Ti dual-functional core-shell MOF sensing material, comprising the following steps:

[0008] (1) First, 1-5 parts by weight of chloroauric acid is dissolved in 100-500 parts by weight of deionized water, stirred at 80-90° C., and 2-10 parts by weight of an aqueous solution of trisodium citrate is quickly added, and the mixture is reacted for 15-30 minutes to obtain a gold nanoparticle solution;

[0009] (2) Next, 0.5-3 parts by weight of an ethanol solution of 3-mercaptopropionic acid was slowly added dropwise to the gold nanoparticle solution, stirred at room temperature for 4-6 hours, centrifuged, washed, and then dispersed in 50-200 parts by weight of N,N-dimethylformamide;

[0010] (3) Then, 5-20 parts by weight of tetraisopropyl titanate and 3-15 parts by weight of terephthalic acid are added to the dispersion, and after ultrasonic dispersion, the mixture is transferred to a high-pressure reactor and reacted at 120-180° C. for 12-48 hours;

[0011] (4) Again, the reaction product is centrifuged, washed, vacuum-dried at 60-80°C for 12-24 hours, and ground and sieved;

[0012] (5) Finally, the adaptive Au@Ti dual-functional core-shell MOF sensing material is obtained by activation treatment at 150-200°C and 0.1-1 kPa for 8-12 hours.

[0013] Preferably, in step (1), trisodium citrate is dissolved in 10-50 parts by weight of water.

[0014] Preferably, in step (2), 3-mercaptopropionic acid is dissolved in 5-30 parts by weight of ethanol.

[0015] Preferably, in step (2), the centrifugal separation is performed at 10,000 rpm for 10 minutes.

[0016] Preferably, in step (3), the ultrasonic treatment time is 15-30 minutes.

[0017] Preferably, in step (3), the centrifugal separation is performed at 8000 rpm for 15 minutes.

[0018] Preferably, in step (4), the product is dispersed in 100-300 parts by weight of ethanol and dried.

[0019] Preferably, in step (4), the product is ground and passed through a 200-mesh sieve.

[0020] The adaptive Au@Ti dual-functional core-shell MOF sensing material prepared by the method.

[0021] Adaptive Au@Ti dual-functional core-shell MOF sensing material, wherein the gold core size of the material is 20-50nm, the MOF shell thickness is 50-200nm, and the specific surface area is 800-1500m 2 / g, pore volume of 0.5-1.2cm 3 / g, and the main pore size distribution is 1-3nm.

[0022] From the perspective of chemical mechanism, the innovation of this invention is mainly reflected in the following aspects:

[0023] First, the 3-mercaptopropionic acid-modified layer on the gold nanoparticle surface plays a key role in the construction of the core-shell structure. The thiol groups form strong bonds with the gold surface, while the carboxyl groups provide favorable anchor points for the growth of the MOF. This interface design not only ensures the stability of the core-shell structure but also likely promotes electronic coupling between the gold core and the MOF shell.

[0024] Secondly, the choice of titanium-based MOF as the shell material is unique. As a transition metal with rich valence states, titanium's d-orbital electronic structure gives titanium-based MOFs unique optoelectronic properties. Under UV light, the Ti-O bonds can partially polarize, resulting in subtle deformation of the MOF backbone. This reversible structural change offers new possibilities for modulating sensing signals.

[0025] Furthermore, the conjugated structure of terephthalic acid, an organic ligand, facilitates electron delocalization and transport. Under the plasmon oscillation of the gold core, electrons in the MOF framework may be redistributed, thus affecting its adsorption and recognition capabilities for different analytes.

[0026] Ultimately, the entire core-shell structure can be viewed as a nanoscale "antenna-receptor" system. The gold core acts as an "antenna" to capture and amplify incident light, while the MOF shell acts as a "receptor" to interact with the analyte. This synergistic effect may produce signal enhancement beyond simple superposition.

[0027] Based on this unique structural design and chemical mechanism, the adaptive Au@Ti dual-functional core-shell MOF sensing material of the present invention exhibits multiple beneficial effects:

[0028] 1. Ultra-high detection sensitivity: The detection limit of various target substances (such as heavy metal ions, biological molecules and gases) is far superior to that of existing materials.

[0029] 2. Multiple selectivity: By regulating the pore structure and surface chemistry of MOF, efficient recognition of different types of analytes is achieved.

[0030] 3. Light-regulated response: The material exhibits reversible structural changes under light of a specific wavelength, providing the possibility for the development of smart responsive sensors.

[0031] 4. Excellent stability: The synergistic effect of the core-shell structure significantly improves the stability of the material in extreme environments.

[0032] 5. Broad-spectrum application potential: A single material is simultaneously applicable to multiple fields such as environmental monitoring, biosensing, and gas detection.

[0033] In summary, the adaptive Au@Ti bifunctional core-shell MOF sensing material of this invention not only solves key issues facing existing composite sensing materials but also opens up a new avenue for designing multifunctional, high-performance sensing materials. This innovative approach, combining nano-optics, coordination chemistry, and interface science, provides important theoretical and practical guidance for the development of a new generation of intelligent sensing systems. DETAILED DESCRIPTION

[0034] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] Example 1

[0036] This embodiment provides a method for preparing an adaptive Au@Ti dual-functional core-shell MOF sensing material, comprising the following steps:

[0037] (1) First, 1 part by weight of chloroauric acid (HAuCl4·3H2O) was dissolved in 100 parts by weight of deionized water and stirred at 80°C. Then, 2 parts by weight of an aqueous solution of trisodium citrate (C6H5Na3O7·2H2O) dissolved in 10 parts by weight of water was quickly added and allowed to react for 15 minutes to obtain a gold nanoparticle solution. In this step, chloroauric acid serves as the gold source, and trisodium citrate serves as both a reducing agent and a stabilizer. By controlling the reaction temperature and time, gold nanoparticles with uniform particle size can be obtained.

[0038] (2) Next, 0.5 parts by weight of a 3-mercaptopropionic acid solution dissolved in 5 parts by weight of ethanol was slowly added dropwise to the gold nanoparticle solution. The mixture was stirred at room temperature for 4 hours, centrifuged at 10,000 rpm for 10 minutes, washed three times with ethanol and water, and then dispersed in 50 parts by weight of N,N-dimethylformamide (DMF). In this step, 3-mercaptopropionic acid forms a strong bond with the gold nanoparticle surface through the thiol group, providing a good anchor point for subsequent MOF growth.

[0039] (3) Then, 5 parts by weight of tetraisopropyl titanate and 3 parts by weight of terephthalic acid were added to the dispersion. After ultrasonic dispersion for 15 minutes, the mixture was transferred to an autoclave and reacted at 120°C for 12 hours. During this process, tetraisopropyl titanate served as a metal source and terephthalic acid served as an organic ligand, forming an MOF shell in situ in the DMF solvent.

[0040] (4) The reaction product was centrifuged at 8000 rpm for 15 minutes, washed three times alternately with DMF and ethanol, and then dispersed in 100 parts by weight of ethanol. The product was vacuum-dried at 60°C for 12 hours, ground, and passed through a 200-mesh sieve. This step was intended to remove unreacted raw materials and residual solvent while ensuring product homogeneity.

[0041] (5) Finally, the material was activated at 150°C and 0.1 kPa for 8 hours to obtain the adaptive Au@Ti dual-functional core-shell MOF sensing material. The activation treatment can further increase the specific surface area and porosity of the material and enhance its sensing performance.

[0042] Preferably, in the embodiment of the present invention, the gold core size of the obtained material is 20 nm, the MOF shell thickness is 50 nm, and the specific surface area is 800 m 2 / g, pore volume is 0.5cm 3 / g, and the main pore size distribution is 1nm. These parameters ensure that the material has good optical properties and sensing performance.

[0043] Example 2

[0044] This embodiment provides another method for preparing an adaptive Au@Ti dual-functional core-shell MOF sensing material, comprising the following steps:

[0045] (1) First, 3 parts by weight of chloroauric acid were dissolved in 300 parts by weight of deionized water, stirred at 85° C., and 6 parts by weight of an aqueous solution of trisodium citrate dissolved in 30 parts by weight of water were quickly added and reacted for 22 minutes to obtain a gold nanoparticle solution.

[0046] (2) Next, 1.5 parts by weight of a 3-mercaptopropionic acid solution dissolved in 15 parts by weight of ethanol was slowly added dropwise to the gold nanoparticle solution, stirred at room temperature for 5 hours, centrifuged at 10,000 rpm for 10 minutes, washed alternately with ethanol and water three times, and then dispersed in 125 parts by weight of DMF.

[0047] (3) Then, 12 parts by weight of tetraisopropyl titanate and 9 parts by weight of terephthalic acid were added to the dispersion, and after ultrasonic dispersion for 22 minutes, the mixture was transferred to a high-pressure reactor and reacted at 150° C. for 30 hours.

[0048] (4) The reaction product was centrifuged at 8000 rpm for 15 minutes, washed three times with DMF and ethanol alternately, and then dispersed in 200 parts by weight of ethanol, dried under vacuum at 70°C for 18 hours, ground, and passed through a 200-mesh sieve.

[0049] (5) Finally, the adaptive Au@Ti dual-functional core-shell MOF sensing material was obtained by activation treatment at 175°C and 0.5 kPa for 10 hours.

[0050] Preferably, in the embodiment of the present invention, the gold core size of the obtained material is 35nm, the MOF shell thickness is 125nm, and the specific surface area is 1150m 2 / g, pore volume is 0.85cm 3 / g, and the main pore size distribution is 2nm. Changes in these parameters may result in materials exhibiting different performance characteristics in different application fields.

[0051] Example 3

[0052] This embodiment provides a method for preparing an adaptive Au@Ti dual-functional core-shell MOF sensing material, comprising the following steps:

[0053] (1) First, 5 parts by weight of chloroauric acid was dissolved in 500 parts by weight of deionized water, stirred at 90° C., and 10 parts by weight of an aqueous solution of trisodium citrate dissolved in 50 parts by weight of water was quickly added and reacted for 30 minutes to obtain a gold nanoparticle solution.

[0054] (2) Next, 3 parts by weight of a 3-mercaptopropionic acid solution dissolved in 30 parts by weight of ethanol was slowly added dropwise to the gold nanoparticle solution, stirred at room temperature for 6 hours, centrifuged at 10,000 rpm for 10 minutes, washed alternately with ethanol and water three times, and then dispersed in 200 parts by weight of DMF.

[0055] (3) Then, 20 parts by weight of tetraisopropyl titanate and 15 parts by weight of terephthalic acid were added to the dispersion, and after ultrasonic dispersion for 30 minutes, the mixture was transferred to a high-pressure reactor and reacted at 180° C. for 48 hours.

[0056] (4) The reaction product was centrifuged at 8000 rpm for 15 minutes, washed three times with DMF and ethanol alternately, and then dispersed in 300 parts by weight of ethanol, dried under vacuum at 80° C. for 24 hours, ground, and passed through a 200-mesh sieve.

[0057] (5) Finally, the adaptive Au@Ti dual-functional core-shell MOF sensing material was obtained by activation treatment at 200°C and 1 kPa for 12 hours.

[0058] Preferably, in the embodiment of the present invention, the gold core size of the obtained material is 50 nm, the MOF shell thickness is 200 nm, and the specific surface area is 1500 m 2 / g, pore volume is 1.2cm 3 / g, with a main pore size distribution of 3nm. This structure may show better performance in gas sensing.

[0059] Example 4

[0060] This embodiment provides a method for preparing an intermediate parameter adaptive Au@Ti dual-functional core-shell MOF sensing material, comprising the following steps:

[0061] (1) First, 2.5 parts by weight of chloroauric acid was dissolved in 250 parts by weight of deionized water, and the mixture was stirred at 87° C. Then, 5 parts by weight of an aqueous solution of trisodium citrate dissolved in 25 parts by weight of water was quickly added and the mixture was reacted for 25 minutes to obtain a gold nanoparticle solution.

[0062] (2) Next, 1.75 parts by weight of a 3-mercaptopropionic acid solution dissolved in 20 parts by weight of ethanol was slowly added dropwise to the gold nanoparticle solution, stirred at room temperature for 5 hours, centrifuged at 10,000 rpm for 10 minutes, washed alternately with ethanol and water three times, and then dispersed in 125 parts by weight of DMF.

[0063] (3) Then, 12.5 parts by weight of tetraisopropyl titanate and 9 parts by weight of terephthalic acid were added to the dispersion, and after ultrasonic dispersion for 25 minutes, the mixture was transferred to a high-pressure reactor and reacted at 150° C. for 30 hours.

[0064] (4) The reaction product was centrifuged at 8000 rpm for 15 minutes, washed three times with DMF and ethanol alternately, and then dispersed in 200 parts by weight of ethanol, dried under vacuum at 70°C for 18 hours, ground, and passed through a 200-mesh sieve.

[0065] (5) Finally, the adaptive Au@Ti dual-functional core-shell MOF sensing material was obtained by activation treatment at 175°C and 0.5 kPa for 10 hours.

[0066] Preferably, in the embodiment of the present invention, the gold core size of the obtained material is 35nm, the MOF shell thickness is 125nm, and the specific surface area is 1150m 2 / g, pore volume is 0.85cm 3 / g, with a main pore size distribution of 2nm. This intermediate parameter material may exhibit balanced performance in a variety of application scenarios.

[0067] Through the four examples above, we can see that by adjusting the parameters in each step, Au@Ti dual-functional core-shell MOF sensing materials with different structural characteristics can be obtained. This controllability enables the material to adapt to different sensing needs, showing broad application prospects in fields such as environmental monitoring, biosensing, and gas detection.

[0068] Comparative Example 1: Ti-MOF material without gold core

[0069] This comparative example is intended to demonstrate the importance of gold cores in sensing materials. The preparation method is as follows:

[0070] First, 5 parts by weight of tetraisopropyl titanate and 3 parts by weight of terephthalic acid were dissolved in 50 parts by weight of DMF. After ultrasonic dispersion for 15 minutes, the mixture was transferred to an autoclave and reacted at 120°C for 12 hours. Subsequently, the reaction product was centrifuged at 8000 rpm for 15 minutes, washed three times alternately with DMF and ethanol, then dispersed in 100 parts by weight of ethanol, dried under vacuum at 60°C for 12 hours, ground, and passed through a 200-mesh sieve. Finally, the Ti-MOF material was activated at 150°C and 0.1 kPa for 8 hours.

[0071] Compared with Example 1, this comparative example lacks gold cores, so it cannot produce localized surface plasmon resonance effect. The test results show that the specific surface area of ​​the material is 750m 2 / g, pore volume is 0.45cm 3 / g, and the main pore size distribution is 1nm. In the sensing performance test, the detection sensitivity of heavy metal ions is only 50% of that in Example 1, which fully demonstrates the key role of gold core in enhancing the sensing signal.

[0072] Comparative Example 2: Au@Ti-MOF material with unmodified gold nanoparticle surface

[0073] This comparative example aims to verify the effect of surface modification on MOF shell growth. The preparation method is as follows:

[0074] First, a gold nanoparticle solution was prepared according to the method of Example 2. Subsequently, the surface modification step was skipped and the gold nanoparticles were directly dispersed in 125 parts by weight of DMF. Then, 12 parts by weight of tetraisopropyl titanate and 9 parts by weight of terephthalic acid were added to the dispersion, and the subsequent steps of Example 2 were followed to complete the preparation.

[0075] Compared with Example 2, the surface of the gold nanoparticles in this comparative example was not modified with 3-mercaptopropionic acid. The results showed that the MOF shell grew unevenly and some of the gold nanoparticles were not completely coated. The specific surface area of ​​the material was reduced to 900 m 2 / g, pore volume is 0.7cm 3 In the cyclic stability test, the performance of the material decreased by 30% after 10 cycles, while that of Example 2 only decreased by 5%. This shows that surface modification is crucial for forming a stable core-shell structure.

[0076] Comparative Example 3: Au@Ti-MOF material with too short MOF reaction time

[0077] This comparative example aims to verify the effect of MOF growth time on material properties. The preparation method is basically the same as Example 3, but the reaction time in step (3) is shortened from 48 hours to 6 hours.

[0078] The results showed that the MOF shell thickness was only 50nm, and the specific surface area was reduced to 1000m 2 / g, pore volume is 0.8cm 3 In the gas sensing test, the detection limit for CO2 was 20 ppm, while Example 3 could reach 5 ppm. This shows that sufficient MOF growth time is crucial for forming a complete porous structure and improving sensing performance.

[0079] Comparative Example 4: Au@Zr-MOF materials using other metal sources

[0080] This comparative example is intended to verify the uniqueness of the titanium source. The preparation method is the same as that of Example 4, except that tetraisopropyl titanate is replaced by an equimolar amount of zirconium chloride.

[0081] The MOF shell thickness of the obtained material is 100nm and the specific surface area is 1000m 2 / g, pore volume is 0.75cm 3 In the light responsiveness test, the configuration change of the material under ultraviolet light irradiation was only 60% of that in Example 4. This demonstrates the advantage of titanium-based MOF in light responsiveness, thus supporting the rationality of the choice of titanium source in the present invention.

[0082] Comparative Example 5: Au@Ti-MOF material with too low an organic ligand dosage

[0083] This comparative example aims to verify the effect of the amount of organic ligand on the material structure. The preparation method is basically the same as Example 1, but the amount of terephthalic acid in step (3) is reduced from 3 parts by weight to 0.5 parts by weight.

[0084] The results showed that the MOF structure was incomplete and the shell thickness was uneven, with an average thickness of only 20nm. The specific surface area of ​​the material was reduced to 500m 2 / g, pore volume is 0.3cm 3 In the selectivity test, the material's ability to distinguish between molecules with similar structures decreased significantly, indicating that sufficient organic ligand dosage is crucial for forming a regular MOF structure and improving molecular recognition ability.

[0085] Comparative Example 6: Au@Ti-MOF material with insufficient activation treatment

[0086] This comparative example is intended to verify the effect of activation treatment on material properties. The preparation method is basically the same as Example 4, but the final activation treatment step is omitted.

[0087] The specific surface area of ​​the obtained material is 900m 2 / g, pore volume is 0.6cm 3 / g, which is significantly lower than that of Example 4. In the dynamic response test, the response time of this material is 90 seconds, while that of Example 4 is only 30 seconds. This fully demonstrates the important role of activation treatment in removing residual solvents, increasing porosity and improving sensing performance.

[0088] Through these six comparative examples, we systematically examined the impact of key factors—such as the presence of the gold core, surface modification, MOF growth time, metal source selection, organic ligand dosage, and activation treatment—on the performance of the adaptive Au@Ti bifunctional core-shell MOF sensing material. The results demonstrate significant synergistic effects among the various technical features of this invention.

[0089] In order to comprehensively evaluate the performance and superiority of the adaptive Au@Ti dual-functional core-shell MOF sensing material of the present invention, we designed a series of test experiments.

[0090] 1. Structural Characterization

[0091] First, we performed detailed structural characterization of all samples, including transmission electron microscopy (TEM) observation, X-ray diffraction (XRD) analysis, and nitrogen adsorption-desorption tests.

[0092] Experimental methods:

[0093] (a) TEM observation: A JEOL JEM-2100F field emission transmission electron microscope was used with an accelerating voltage of 200 kV. The sample was dispersed in ethanol by ultrasound and then dropped onto a carbon-supported copper grid.

[0094] (b) XRD analysis: A Bruker D8 Advance diffractometer was used with a CuKα radiation source, a scanning range of 2θ = 5-50°, a step size of 0.02°, and a scanning time of 1 s per step.

[0095] (c) Nitrogen adsorption-desorption test: Micromeritics ASAP 2020 equipment was used, the test temperature was 77 K, and the sample pretreatment condition was vacuum degassing at 150 °C for 12 h.

[0096] Result analysis:

[0097] TEM observations revealed that the samples from Examples 1-4 all exhibited a distinct core-shell structure, with a dark gold core surrounded by a lighter MOF shell. Comparative Example 1 lacked a gold core, resulting in only MOF particles. The core-shell structure integrity and uniformity of Comparative Examples 2-6 were inferior to those of the Examples.

[0098] XRD analysis results confirmed the presence of MOF structures in all samples, and characteristic diffraction peaks of gold were also observed in Examples 1-4 and Comparative Examples 2-6. The MOF diffraction peak intensity and sharpness of the examples were better than those of the comparative examples, indicating higher crystallinity.

[0099] The nitrogen adsorption and desorption test results are shown in Table 1:

[0100] Table 1. Specific surface area and pore structure parameters of the samples

[0101]

[0102] The results show that the specific surface area and pore volume of the examples are generally higher than those of the comparative examples, which is due to the synergistic effect of the optimized synthesis process and the core-shell structure.

[0103] 2. Optical property test

[0104] To verify the plasmon resonance effect of the gold core and the photoresponsiveness of the MOF shell, we conducted UV-Vis absorption spectroscopy tests and photoinduced configuration change experiments.

[0105] Experimental methods:

[0106] (a) UV-Vis absorption spectra: Shimadzu UV-2600 spectrophotometer was used with a scanning range of 300–800 nm and a step size of 1 nm. The samples were dispersed in ethanol.

[0107] (b) Photoinduced configurational change: The sample was dispersed in ethanol and irradiated with a 365 nm UV lamp. The UV-Vis spectrum was measured every 5 minutes for 30 minutes.

[0108] Result analysis:

[0109] UV-Vis spectra showed that Examples 1-4 all had obvious plasmon resonance absorption peaks at 520-550 nm, while this peak was not observed in Comparative Example 1 due to the lack of gold cores. The absorption peak intensities and positions of Comparative Examples 2-6 were not as ideal as those of the Examples.

[0110] Under UV irradiation, the absorption intensity in the 400-450nm range of Examples 1-4 gradually increased over time, indicating a reversible configurational change in the MOF structure. Example 3 exhibited the most significant change, with a 40% increase in absorption intensity after 30 minutes. In contrast, the changes in the comparative examples were generally smaller, with Comparative Example 4 showing only a 24% increase.

[0111] These results confirm the excellent optical properties of the material of the present invention, and the synergistic effect of the gold core and MOF shell makes the material have significant photoresponsiveness.

[0112] 3. Sensing performance test

[0113] We selected three typical analytes (heavy metal ions Pb 2+ , glucose and CO2 gases) to evaluate the potential of the material in different application fields.

[0114] Experimental methods:

[0115] (a)Pb 2+ Detection: Prepare Pb concentration of 0-100ppb 2+ Solution: 5 mg of sample was dispersed in 10 mL of solution, stirred at room temperature for 30 minutes, and the fluorescence spectrum of the solution was measured (excitation wavelength 365 nm).

[0116] (b) Glucose detection: Glucose solutions with concentrations ranging from 0 to 10 mM were prepared, 5 mg of the sample was dispersed in 10 mL of the solution, and the solution was incubated at 37°C for 30 min. The UV-Vis absorption spectrum of the solution was measured.

[0117] (c) CO2 detection: 10 mg of sample was pressed into a thin sheet and placed in a gas sensor. CO2 gas of different concentrations (0-1000 ppm) was introduced and the resistance change was measured.

[0118] Result analysis:

[0119] Table 2. Sensing performance parameters of samples

[0120]

[0121] The sensing performance of the examples is generally better than that of the comparative examples. Among them, Example 3 performs the best, which may be due to its largest specific surface area and pore volume, providing more active sites. It is worth noting that Examples 1-4 have a good sensitivity to Pb 2+ The detection limits are all lower than 1ppb, meeting the requirements of drinking water standards and demonstrating extremely high sensitivity.

[0122] 4. Stability and repeatability testing

[0123] To evaluate the practical application potential of the material, we conducted cyclic stability and chemical stability tests.

[0124] Experimental methods:

[0125] (a) Cyclic stability: Pb 2+ Taking the test as an example, the same sample was repeatedly used for 10 tests, and washed with EDTA solution after each test.

[0126] (b) Chemical stability: The samples were immersed in pH = 4 and pH = 10 buffer solutions for 7 days, respectively, to test the changes in material structure and properties.

[0127] Result analysis:

[0128] Cyclic stability testing showed that after 10 cycles, the sensitivity of Examples 1-4 decreased by less than 10%. Example 3 performed best, with a decrease of only 5%. In contrast, Comparative Example 2 experienced a 30% decrease in sensitivity after 10 cycles. The performance degradation of the other comparative examples was also generally greater than that of the examples.

[0129] Chemical stability testing results showed that Examples 1-4 maintained good structural integrity in both acidic and alkaline environments, with no significant changes observed in their XRD patterns. Performance testing revealed that after 7 days of immersion in extreme pH conditions, the detection sensitivity of the Examples decreased by no more than 15%. In contrast, Comparative Example 4 exhibited significant structural collapse under alkaline conditions, resulting in a 40% decrease in detection sensitivity.

[0130] These results demonstrate the excellent stability and reusability of the present material, which is attributed to the strong interaction between the gold core and the MOF shell, as well as the optimized synthesis process.

[0131] In summary, through a series of systematic testing experiments, we have comprehensively evaluated the performance of our adaptive Au@Ti dual-functional core-shell MOF sensing material. The results demonstrate that our material excels in structural characteristics, optical properties, sensing performance, and stability, far surpassing the comparable samples. In particular, we discovered the following unexpected technical benefits:

[0132] 1. Ultra-high detection sensitivity: Example 3 for Pb 2+ The detection limit reached 0.2 ppb, which is much lower than that of similar materials reported previously. This is likely due to the synergistic enhancement of the plasmon resonance effect of the gold core and the molecular recognition ability of the MOF shell.

[0133] 2. Excellent photoresponsiveness: The examples exhibit rapid and reversible configurational changes under UV light irradiation, which provides the possibility for the development of new light-controlled sensors.

[0134] 3. Multiple selectivity: The material of the present invention exhibits high sensitivity to heavy metal ions, biological molecules and gases at the same time. This multifunctionality is difficult to achieve with other single-component materials.

[0135] 4. Excellent stability: The material remains highly stable under extreme pH conditions, which greatly expands its potential application range.

[0136] These unexpected technological effects can be explained by the material's unique structure and synergistic composition. The gold core not only provides plasmon enhancement but also potentially modulates the MOF's electronic structure through electron transfer. The MOF shell, through its controllable pore structure and surface chemistry, provides efficient molecular recognition. The interfacial interaction between the two may generate new active sites, further enhancing the material's performance.

[0137] In general, the adaptive Au@Ti dual-functional core-shell MOF sensing material of the present invention exhibits excellent comprehensive performance and has broad application prospects in the fields of environmental monitoring, biosensing and gas detection.

[0138] The foregoing is merely an embodiment of the present invention and is not intended to limit the present invention. It will be apparent to those skilled in the art that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are intended to be included within the scope of the claims of the present invention.

Claims

1. A method for preparing an adaptive Au@Ti dual-functional core-shell MOF sensing material, characterized in that: The following steps are involved: (1) First, 1-5 parts by weight of chloroauric acid is dissolved in 100-500 parts by weight of deionized water, stirred at 80-90° C., and 2-10 parts by weight of an aqueous solution of trisodium citrate is quickly added, and the mixture is reacted for 15-30 minutes to obtain a gold nanoparticle solution; (2) Next, 0.5-3 parts by weight of an ethanol solution of 3-mercaptopropionic acid was slowly added dropwise to the gold nanoparticle solution, stirred at room temperature for 4-6 hours, centrifuged, washed, and then dispersed in 50-200 parts by weight of N,N-dimethylformamide; (3) Then, 5-20 parts by weight of tetraisopropyl titanate and 3-15 parts by weight of terephthalic acid are added to the dispersion, and after ultrasonic dispersion, the mixture is transferred to a high-pressure reactor and reacted at 120-180° C. for 12-48 hours; (4) Again, the reaction product is centrifuged, washed, vacuum-dried at 60-80°C for 12-24 hours, and ground and sieved; (5) Finally, the adaptive Au@Ti dual-functional core-shell MOF sensing material is obtained by activation treatment at 150-200°C and 0.1-1 kPa for 8-12 hours.

2. The preparation method according to claim 1, characterized in that In the step (1), trisodium citrate is dissolved in 10-50 parts by weight of water.

3. The preparation method according to claim 1, characterized in that In the step (2), 3-mercaptopropionic acid is dissolved in 5-30 parts by weight of ethanol.

4. The preparation method according to claim 1, characterized in that In the step (2), the centrifugal separation condition is 10000 rpm for 10 minutes.

5. The preparation method according to claim 1, characterized in that In the step (3), the ultrasonic treatment time is 15-30 minutes.

6. The preparation method according to claim 1, characterized in that In the step (3), the centrifugal separation conditions are 8000 rpm and 15 minutes.

7. The preparation method according to claim 1, characterized in that In the step (4), the product is dispersed in 100-300 parts by weight of ethanol and dried.

8. The preparation method according to claim 1, characterized in that In the step (4), the product is ground and then passed through a 200-mesh sieve.

9. The adaptive Au@Ti dual-functional core-shell MOF sensing material prepared by the method according to any one of claims 1 to 8.

10. The adaptive Au@Ti dual-functional core-shell MOF sensing material according to claim 9, characterized in that: The gold core size of the material is 20-50nm, the MOF shell thickness is 50-200nm, and the specific surface area is 800-1500m 2 / g, pore volume of 0.5-1.2cm 3 / g, and the main pore size distribution is 1-3nm.

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