Conjugated microporous polymer material for detecting heavy metal iron in drinking water and its synthesis method and application

Abstract

The application discloses a conjugated microporous polymer material for detecting heavy metal iron in drinking water and a synthesis method and application thereof. The conjugated microporous polymer material for detecting heavy metal iron in drinking water is synthesized by a solvothermal reaction method of terephthalic dihydrazide and 2,5-dimethoxy terephthaldehyde. The mass ratio of terephthalic dihydrazide to 2,5-dimethoxy terephthaldehyde is 2:5 to 5:2 during the synthesis.

Description

Technical Field

[0001] This invention belongs to the field of food safety testing and new materials technology, specifically relating to a conjugated microporous polymer (CMP) material for detecting heavy metal iron in drinking water, its synthesis method, and its application. Background Technology

[0002] Fe 3+ While Fe is an essential trace element for the human body, excessive intake can lead to health problems such as liver damage and cardiovascular disease. Furthermore, as a common water pollutant, it may affect drinking water safety. Therefore, Fe in drinking water... 3+ The detection of Fe in drinking water is of great significance in environmental monitoring and public health. Currently, the detection of Fe in drinking water... 3+ The main sources of iron pollution are the natural dissolution of iron-bearing minerals (such as the oxidation of hematite and pyrite under acidic or low-oxygen conditions) and soil infiltration, as well as human pollution such as industrial wastewater discharge, pipeline corrosion, iron-based coagulant residues, and agricultural runoff. According to China's "Standards for Drinking Water Quality" (GB 5749-2022), the Fe content in drinking water... 3+ The concentration should not exceed 0.3 mg / L. Most existing detection methods employ atomic fluorescence spectrometry, atomic absorption spectrometry, and X-ray fluorescence spectrometry to determine metal content. However, these methods are often time-consuming, costly, and require skilled operators, limiting their application in routine analysis. In recent years, fluorescence sensing technology has become a research hotspot due to its high sensitivity, rapid response, and ease of operation. Therefore, exploring methods for selectively detecting Fe in drinking water using fluorescence is crucial. 3+ Novel functional nanomaterials are extremely important.

[0003] Conjugated microporous polymers (CMPs) are a class of porous organic materials with extended π-conjugated networks and permanent microporous structures. Their high specific surface area, tunable pore size distribution, and excellent photoelectric properties make them highly promising for adsorption, catalysis, and sensing. Compared to traditional fluorescent probes (such as small molecule dyes or metal-organic frameworks MOFs), CMPs offer advantages such as molecular designability, signal amplification, and good stability. Currently, Fe based on CMPs... 3+ Fluorescent sensors primarily achieve detection through electron transfer (ET) or energy competitive absorption (ACQ) mechanisms. For example, triazine-based CMPs can enhance fluorescence quenching efficiency through π-π stacking interactions, while fluorescein-based CMPs can enhance fluorescence quenching efficiency through Fe... 3+ Specific recognition is achieved through coordination with hydroxyl / carboxyl groups. Therefore, Fe based on CMPs is constructed. 3+ Specific fluorescent probes have promising applications.

[0004] According to GB 8538-2022, iron detection methods include flame atomic absorption spectrometry and phenanthrene spectrophotometry. While these methods offer high sensitivity, they also suffer from drawbacks such as high instrument costs and the need for specialized personnel to operate them. Given the limitations of these two methods, there is an urgent market need to develop a rapid, efficient, sensitive, and easy-to-operate detection method for Fe in water. 3+ Rapid and accurate detection.

[0005] Liaocheng University has synthesized a novel ultrasmall hydrazone covalent organic polymer (UHCOP) by reacting 2,4,6-trihydroxy-1,3,5-benzenetrialdehyde with 1,4-benzylhydrazine via a Schiff base reaction at room temperature. This UHCOP is then used as a sensitive fluorescent sensor for the rapid (<2 minutes) and selective detection of Fe in aqueous solutions. 3+ The prepared UHCOP exhibited an ultrasmall size, with a diameter of 7.98 ± 0.97 nm, and emitted stable fluorescence emission at 510 nm. UHCOP showed promise for Fe... 3+ It exhibits good sensitivity and high selectivity. UHCOP with Fe 3+ The coordination of UHCOP leads to significant aggregation and quenching of the reaction. The linear range is 5.0 μM to 1.4 mM (R0). 2 =0.999), with a detection limit of 2.5 μM. Finally, UHCOP has been successfully applied to the detection of Fe in actual water samples. 3+ The detection results demonstrate that the prepared UHCOP, as a sensitive fluorescent sensor, holds promise for the selective detection of Fe in aqueous solutions. 3+ Although UHCOP is effective against Fe 3+ It exhibits good selectivity, but in actual samples, other metal ions (such as Ni) show poor selectivity. 2+ Co 2+ (etc.) may be related to Fe 3+ Coexistence. These ions may have some impact on the detection results. Meanwhile, there is a lack of comprehensive validation of its anti-interference capabilities for practical applications. Furthermore, while UHCOP's detection limit of 2.5 μM is superior to many existing methods, in some practical applications, Fe... 3+ The concentration of Fe may be even lower, especially in clean natural water bodies or treated drinking water. For example, some environmental water samples contain Fe... 3+ The concentration may be below 1 μM.

[0006] Kaohsiung Medical University has developed a novel approach using cranberry bean-derived carbon dots (CB-CDs) as a potential fluorescent sensor for the selective detection of Fe in aqueous solutions. 3+The synthesis process of CB-CDs is non-toxic, convenient, and environmentally friendly. The resulting carbon dots exhibit stable fluorescence with a quantum yield of approximately 10.85%. By changing the excitation wavelength, the carbon dots emit a wide fluorescence emission range between 410 and 540 nm, which can be used to detect Fe under 380 nm excitation. 3+ The results showed that Fe 3+ The ion quenching effect on the fluorescence intensity of carbon dots is stronger than that of other heavy metals, and it can achieve Fe quenching within 3 minutes. 3+ The detection of Fe was demonstrated by spectral data, which showed that the obtained carbon dots could be detected over a wide concentration range of 30-600 μM. 3+ The detection limit is 9.55 μM. However, sample pretreatment is complex. Although the synthesis process of CB-CDs is simple and environmentally friendly, actual water samples may contain various impurities, requiring complex pretreatment to remove these impurities. For example, organic matter and suspended particles in the water sample may affect the fluorescence performance of CB-CDs.

[0007] Yanbian University has constructed a tetraphenylvinyl covalent organic framework (TTPE-COF) with a rhombic structure via a Schiff base reaction. TTPE-COF possesses a porous structure and high surface area, enabling selective detection of Fe. 3+ Fe 3+ The detection limit is 3.07 μM. TTPE-COF shows promise in fluorescence sensors. However, the detection performance of TTPE-COF under different pH conditions was not investigated in detail. 3+ The form and chemical properties of COF may differ at different pH values, which could affect the detection accuracy of COF. Furthermore, TTPE-COF has not been applied to Fe in real samples. 3+ The testing capabilities are insufficient for practical applications.

[0008] Jilin University has synthesized the first case of selective detection of Fe based on the porous organic polymer POP-HT using (p-aminophenyl)methane and chromogenic 2,5,8-trichloro-s-heptaazine. 3+ A light-emitting sensor. POP-HT in Fe 3+ It exhibits significant fluorescence quenching in the presence of ions. Furthermore, the luminescence intensity is related to the corresponding Fe... 3+ A good linear relationship was established between concentrations. The luminescence quenching mechanism was also investigated through experiments and theoretical calculations. The results indicate that, compared with other metal ions and organic solvents, POP-HT can serve as an effective luminescent indicator for the qualitative and quantitative detection of Fe in aqueous solutions. 3+ Although POP-HT is effective against Fe 3+The detection sensitivity of Fe³⁺ ions is high, but its linear detection range is 5–600 ppm. For higher concentrations of Fe³⁺ ions, sample dilution may be necessary. Furthermore, this technology primarily validates the effectiveness of POP-HT for Fe³⁺ ions through laboratory simulation experiments. 3+ It has good detection performance, but lacks the ability to detect Fe in actual water or biological samples. 3+ Detection and verification of ions. Summary of the Invention

[0009] In view of the shortcomings of the prior art, the purpose of this invention is to synthesize a novel CMP material (THDH-DMA) and to construct Fe based on this material. 3+ Fluorescence detection methods and fluorescent test strips were developed to detect Fe in drinking water. 3+ This highly efficient and specific detection method aims to solve the problems of low sensitivity, complex operation, and high cost in existing heavy metal detection methods, and provide a more convenient, accurate and economical means for food safety monitoring.

[0010] To achieve the above objectives, the technical solution provided by this invention is as follows: The detection of heavy metal iron (Fe) in drinking water 3+ The conjugated microporous polymer material is synthesized by a solvothermal reaction of terephthalic hydrazide (THDH) and 2,5-dimethoxyterephthalaldehyde (DMA). The mass ratio of terephthalic hydrazide to 2,5-dimethoxyterephthalaldehyde during synthesis is 2:5 to 5:2, preferably 1:1.

[0011] Preferably, the solvent used in the synthesis is o-dichlorobenzene and n-butanol, wherein the volume ratio of o-dichlorobenzene to n-butanol is 10:1 to 1:1, more preferably 17:3.

[0012] Preferably, acetic acid is also added during synthesis, and the mass-volume ratio of terephthalic hydrazide, 2,5-dimethoxyterephthalaldehyde, and acetic acid is (20-50) mg:(20-50) mg:(0.05-0.5) mL, more preferably 29.12 mg:29.12 mg:1 mL.

[0013] Preferably, the acetic acid concentration is 6M.

[0014] The synthesis method of the conjugated microporous polymer material for detecting heavy metal iron in drinking water includes the following steps: (1) Add terephthalic acid hydrazide and 2,5-dimethoxyterephthalaldehyde to a mixed solution consisting of o-dichlorobenzene and n-butanol, and sonicate for 10 min. Add acetic acid to the mixed solution, sonicate for 5 min, and then transfer the resulting mixture to a 10 mL Schlenk reaction tube. Perform three freeze-pump-thaw cycles and heat at 120 °C for 72 h. (2) After the reaction was complete, the solid was cooled to room temperature and then washed repeatedly with tetrahydrofuran (THF) and N,N-dimethylformamide (DMF). After washing, the product was dried under vacuum at 100°C to obtain a bright yellow powder.

[0015] The method for detecting iron in drinking water using conjugated microporous polymer materials involves adding the sample to be tested into a solution of the conjugated microporous polymer material and reacting for 0.5–10 min, preferably 1 min. The fluorescence intensity of the conjugated microporous polymer material is then measured, and the iron concentration is calculated using the functional relationship: Y = 0.278X + 1.1363, R... 2 The value is 0.997, where Y is the fluorescence intensity of the conjugated microporous polymer material, and X is the iron concentration value, with the concentration unit being mg / L. The conjugated microporous polymer material solution is an acetonitrile, ethanol, DMF, methanol, water, or dimethyl sulfoxide solution of the conjugated microporous polymer material, preferably DMF. The concentration of the conjugated microporous polymer material is 10~1000 μg / L, and the pH value of the conjugated microporous polymer material solution is 2.0~7.0, preferably 7. The fluorescence detection excitation wavelength is 350 nm, and the detection wavelength is 465 nm. The method can detect iron concentrations in the range of 0.01~9 mg / L.

[0016] The aforementioned conjugated microporous polymer material for detecting heavy metal iron in drinking water can be used to prepare test strips for detecting heavy metal iron in drinking water. Blank test strips are immersed in THDH-DMA suspension for 4 minutes, air-dried at room temperature, and this drying and immersion process is repeated three times to obtain THDH-DMA fluorescent test strips.

[0017] The method for detecting heavy metal iron in drinking water using the above-mentioned THDH-DMA fluorescent test strip involves irradiating the prepared yellow THDH-DMA test strip with a 365 nm ultraviolet lamp, causing the THDH-DMA test strip to turn blue. The THDH-DMA test strip is then immersed in an iron ion solution for 1 min. After the test strip dries, it is irradiated with a 365 nm ultraviolet lamp, and a fluorescence image is captured using the built-in camera of a smartphone. The RGB (red-R, green-G, and blue-B) signal values ​​in the fluorescence image are then automatically extracted using the Color Picker APP, and a G / B value is established relative to Fe. 3+ The linear functional relationship between concentrations is expressed as: G / B = 0.041X + 1.738, R 2The value is 0.995, where G / B is the RGB (red-R, green-G, and blue-B) signal value in the fluorescence image, and X is the iron concentration value. The linear range of the method is 0~10 mg / L, and the detection limit is 0.15 mg / L, which is lower than the limit standard of the World Health Organization. The irradiation angle of the ultraviolet lamp is 30~90°, preferably 45°, and the range of the ultraviolet lamp is 5~40 cm, preferably 20 cm.

[0018] The present invention will be further described below: This invention provides a novel conjugated microporous polymer (THDH-DMA) and its synthesis and application methods for Fe in drinking water. 3+ Rapid detection. This not only solves the existing Fe... 3+ The detection method suffers from problems such as low sensitivity, complex operation, and high cost, and it also significantly increases the concentration of Fe in water. 3+ The improved detection efficiency provides a new approach for efficient, convenient, and economical heavy metal detection. By preparing THDH-DMA materials, a fluorescent detection method for Fe was constructed based on THDH-DMA materials. 3+ The method was validated for linearity, specificity, and robustness, and its performance was tested on real water samples. Furthermore, a smartphone-based visualization platform was established to achieve Fe... 3+ Real-time on-site monitoring. The method is as follows: THDH-DMA was synthesized in this invention using terephthalohydrazide and 2,5-dimethoxyterephthalaldehyde via a solvothermal reaction. The physicochemical properties and fluorescence characteristics of the THDH-DMA material were studied, and it was found that THDH-DMA exhibits strong fluorescence emission at an excitation wavelength of 350 nm, and is sensitive to Fe... 3+ It exhibits high selectivity and anti-interference capabilities. Subsequently, a THDH-DMA-based fluorescence detection method for Fe was established. 3+ The method was found to have advantages such as a wide linear range and a low detection limit. To optimize this detection method, we systematically investigated the type of solvent, solution pH, and the relationship between THDH-DMA and Fe using a controlled variable method. 3+ The effects of factors such as reaction time on the detection results were investigated, and the optimal reaction conditions were finally determined as follows: N,N-dimethylformamide (DMF) as solvent, pH 7, and reaction time of 1 min. Finally, the THDH-DMA material was applied to spiked recovery experiments in tap water and mineral water. The results showed high recovery rates (97.99–104.55%) and good reproducibility (RSD ≤ 2.88%), indicating that the THDH-DMA-based Fe detection method... 3+ The method demonstrates good performance in practical applications. Finally, a visual monitoring platform based on fluorescent test strips and smartphones was established to realize Fe... 3+Real-time on-site monitoring. The THDH-DMA test strip showed its effectiveness in RGB analysis for Fe. 3+ The detection limit is 0.15 mg / L, which is lower than the maximum limit standard of my country and the World Health Organization (0.3 mg / L).

[0019] In summary, this invention synthesizes a novel conjugated microporous polymer, THDH-DMA. Fe based on THDH-DMA material... 3+ The fluorescence detection method and fluorescent test strips have the advantages of a wide linear range and a low detection limit. This method utilizes THDH-DMA for Fe... 3+ Its high selectivity and anti-interference capabilities enable the targeting of Fe 3+ Specific fluorescence detection for Fe in drinking water 3+ This invention provides a new technical means for rapid and accurate detection. The THDH-DMA test strip prepared in this invention has excellent stability and is easy to store, without relying on expensive laboratory equipment. It also establishes a portable visualization method based on visual tracking for real-time monitoring of Fe. 3+ This invention opens up new avenues for the application of CMPs materials in the detection of heavy metal pollution in drinking water. It not only provides valuable theoretical support and practical guidance for the advancement of drinking water safety testing technology, but also expands the application of Fe... 3+ The on-site real-time detection provides materials, methods, and test strips, and also inspires the detection of other metal ions, providing new methods for the development of subsequent fluorescence sensors. Attached Figure Description

[0020] Figure 1 SEM images (a, b) and TEM images (c, d) of THDH-DMA. Figure 2 (a) FT-IR spectra of THDH-DMA and monomers; (b) XPS spectra of THDH-DMA; (c) XPS spectra of THDH-DMA in the C1s region; (d) XPS spectra of THDH-DMA in the N 1s region; (e) XPS spectra of THDH-DMA in the O 1s region. Figure 3 (a) XRD pattern of THDH-DMA; (b) TGA curve of THDH-DMA measured under N2; (c) N2 adsorption-desorption isotherm of THDH-DMA; Figure 4 (a) Fluorescence spectrum of THDH-DMA (Inset: Image of THDH-DMA under UV light); (b) CIE chromaticity diagram of THDH-DMA; (c) Fluorescence spectra of THDH-DMA, DMA and THDH; Figure 5(a) Fluorescence intensity changes of THDH-DMA in different solvents; (b) Fluorescence intensity changes of Fe at different pH values. 3+ (c) Changes in fluorescence intensity of THDH-DMA after addition; 3+ The change in fluorescence intensity of THDH-DMA over time; Figure 6 (a) THDH-DMA in different Fe 3+ Fluorescence emission spectra at different concentrations of Fe (Illustration: Fe at different concentrations) 3+ (a) Image of THDH-DMA under UV light in the presence of (0-10 mg / L); (b) Effect of THDH-DMA on different Fe 3+ (c) Corresponding calibration curves (I0 / I) for concentrations (0.01-9 mg / L); (d) Fluorescence intensity of THDH-DMA in the presence of different metal ions (Inset: Images of THDH-DMA under UV light in the presence of different ions). Figure 7 (a) Schematic diagram of the preparation of THDH-DMA test strips; (b) Used for real-time monitoring of Fe 3+ (a) A schematic diagram of a smartphone-integrated portable device and system; (b) Fluorescence images of test strips processed with THDH-DMA at different times under a UV lamp. Detailed Implementation

[0021] 1. Experimental Methods 1.1 Experimental Reagents Terephthalyl hydrazide, 2,5-dimethoxytetraphenyl phthalaldehyde, acetic acid, o-dichlorobenzene, n-butanol, acetonitrile, ethanol, DMF, methanol, dimethyl sulfoxide, N,N-dimethylformamide, and tetrahydrofuran were purchased from Shanghai Maclean Biochemical Technology Co., Ltd., sodium hydroxide was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., hydrochloric acid was purchased from Xilong Scientific Co., Ltd., and all metal ion standard solutions were purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0022] 1.2 Experimental Equipment and Instruments Schlenk reaction tubes (10 mL) were purchased from Yongcheng Glassware Co., Ltd.; the analytical balance (BCE1241-1CCN) was purchased from Sartorius Instruments (Beijing) Co., Ltd.; the micropipette was purchased from Thermo Fisher Scientific (Shanghai) Co., Ltd.; the temperature-controlled ultrasonic cleaner (JP-040S) was purchased from Shenzhen Jiemeng Cleaning Equipment Co., Ltd.; the vacuum oven (DZF-6050) was purchased from Shanghai Jinghong Experimental Equipment Co., Ltd.; the pH meter (PHS-25-3C-3E-2F) was purchased from Shanghai Leici Technology Co., Ltd.; and the fluorescence spectrometer (F-7000) was purchased from Hitachi, Japan. The X-ray powder diffractometer (Empyrean) was purchased from Panaco GmbH, Netherlands; the field emission scanning electron microscope and energy dispersive spectrometer (JSM-7800F & TEAM) was purchased from NEC Corporation; the transmission electron microscope and energy dispersive spectrometer (JEM-2100 & X-Max80) was purchased from NEC Corporation; the surface area, micropore, and mesopore analyzer (BELSORP-max) was purchased from Mack Bayer GmbH; the X-ray photoelectron spectroscopy (K-Alpha+) was purchased from Thermo Fisher Scientific (Shanghai) Co., Ltd.; the Fourier transform infrared spectrometer (IR Affinity-1) was purchased from Shimadzu Corporation, Japan; and the synchronous thermal analyzer (STA449 F5) was purchased from Netzsch Instruments Manufacturing Co., Ltd.

[0023] 1.3 Preparation of THDH-DMA The synthesis of THDH-DMA was performed as follows: THDH (29.12 mg, 0.15 mmol) and DMA (29.12 mg, 0.15 mmol) were added to a mixed solution consisting of 1.7 mL of o-dichlorobenzene and 0.3 mL of n-butanol, and the mixture was sonicated for 10 min. 0.1 mL of 6 M acetic acid was added to the mixed solution, and the mixture was sonicated for 5 min. The resulting mixture was then transferred to a 10 mL Schlenk reaction tube, and three freeze-pump-thaw cycles were performed, followed by heating at 120 °C for 72 h. After cooling the solid to room temperature, it was washed repeatedly with alternating THF and DMF. Following washing, the product was dried under vacuum at 100 °C to obtain a bright yellow powder.

[0024] 1.4 Experimental Measurement Methods 1.4.1 Characterization of THDH-DMA materials (1) Field emission scanning electron microscopy A small amount of sample powder was sprinkled onto a sample stage coated with conductive adhesive, purged with N2, and then sputter-coated with gold. Next, SEM measurements were performed using electron microscopes at voltages of 5.0 kV and 20.0 kV.

[0025] (2) Transmission electron microscopy Take a small amount of THDH-DMA and place it in a 2 mL centrifuge tube. Add an appropriate amount of anhydrous ethanol. Drop the resulting solution onto a precision copper mesh and irradiate it with an infrared lamp for 20 min to dry it before testing.

[0026] (3) Fourier transform infrared spectroscopy Characteristic functional group information of the material was obtained using FT-IR. The sample was pretreated by pressing it into a pellet with potassium chloride, followed by FT-IR measurements in the range of 400-4000 nm with a resolution of 7.

[0027] (4) X-ray photoelectron spectroscopy Prepare a clean aluminum foil, cut double-sided tape and stick it to the surface of the aluminum foil, then evenly sprinkle an appropriate amount of material powder onto the tape area. Fold the aluminum foil in half and place it into a tablet press for pressing. Fix the pressed sample onto the XPS sample stage for testing.

[0028] (5) BET specific surface area determination method The THDH-DMA sample was ground into a uniform powder. 60 mg of the sample was weighed and placed into a clean, dry sample tube. The sample was degassed by heating in a N2 atmosphere for 12 h. After degassed, the heating was turned off, and the sample was allowed to cool naturally to room temperature. The sample tube was removed from the degassed station, and the total weight of the sample tube and sample was recorded. The sample tube was then connected to the test port of the BET analyzer. N2 was introduced into the sample tube, and gas adsorption testing was performed at liquid nitrogen temperature (-196°C).

[0029] (6) Powder X-ray diffraction method The scanning range was from 2° to 40°, with the tube current set to 100 mA and the tube voltage to 40 kV. The scanning rate was set to 10° per minute, the step angle to 0.01°, and Cu-Kα rays with a wavelength of 0.15406 nm were used as the radiation source.

[0030] (7) Thermogravimetric analysis First, the weight of the empty crucible is measured. Then, 2.0 mg of TAPA-BTT sample is accurately weighed and placed inside the crucible. Before starting the test program, sample loading and zeroing and temperature calibration are performed.

[0031] 1.5 Study on the fluorescence properties of THDH-DMA materials Weigh 1 mg of THDH-DMA and add it to 100 mL of DMF. Sonicate at room temperature for 30 min. Measure 2.5 mL of the THDH-DMA solution into a quartz cuvette and measure the fluorescence spectrum of THDH-DMA to determine the excitation and emission wavelengths.

[0032] 1.6 THDH-DMA fluorescence detection of Fe 3+Method establishment (1) Establishment of the standard curve By adding a series of different concentrations of Fe to the THDH-DMA suspension 3+ (0.01, 0.05, 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 mg / L), the fluorescence intensity of the mixture was measured using an F-7000 fluorescence spectrometer. The linear range of detection was determined using the Stern-Volmer formula I0 / I = 1 + Ksv[M] (where I0 is the concentration of added Fe). 3+ Fluorescence intensity of pre-THDH-DMA; I is the fluorescence intensity of Fe-added 3+ Fluorescence intensity of THDH-DMA afterward; M represents Fe 3+ The concentration (mg / L); Ksv is a constant in the Stern-Volmer equation) is calculated, and LOD is determined using the formula LOD=3σ / k.

[0033] (2) Sensitivity The limit of detection (LOD) was determined using a signal-to-noise ratio of 3. The LOD, which represents the concentration of the sample at both 3 and 10 times the signal-to-noise ratio, was determined using the formula LOD = 3σ / k.

[0034] (3) Selectivity and competitiveness By adding Fe 3+ The fluorescence quenching effect of THDH-DMA on Fe was analyzed by comparing it with that of other metal ions (10 mg / L). 3+ The selectivity of fluorescence quenching is expressed as I / I0, where I / I0=1 indicates constant fluorescence intensity, I / I0>1 indicates enhanced fluorescence, and I / I0<1 indicates fluorescence quenching. Furthermore, in the detection of Fe... 3+ An equal concentration of interfering ion solution was added, and the fluorescence intensity of THDH-DMA in the mixed system was measured to test Fe. 3+ The anti-interference performance of the test.

[0035] (4) Experimental conditions for optimizing the construction method The controlled variable method was used to study the material solvent, pH value, THDH-DMA and Fe in the constructed method. 3+ The reaction time was optimized. Solvents selected included DMF, acetonitrile, ethanol, DMF, methanol, water, and dimethyl sulfoxide. pH values ​​were set to 2, 3, 4, 5, 6, and 7, and reaction times were set to 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 min, respectively.

[0036] (5) Recovery rate and relative standard deviation Mineral water (Nongfu Spring Co., Ltd., Hangzhou, China) was purchased from a local supermarket in Shenzhen, while tap water was taken from the laboratory. All water samples were filtered through a 0.22 μm syringe filter, and then Fe was added at concentrations of 0.5, 2, and 5 mg / L, respectively. 3+ Ions. Fluorescence intensity was measured after adding THDH-DMA to the solution, and the recovery rate and relative standard deviation were calculated.

[0037] 1.7 Construction of a Smartphone Integrated Sensing Platform Based on Fluorescent Test Strips Based on the installed Color Picker Version 3.1 App smartphone (iOS Version 18.3.1) and fluorescent THDH-DMA test strips, a smartphone-integrated ratio sensing platform was developed for intelligent visual detection of Fe. 3+ The test strip was immersed in THDH-DMA suspension for 4 minutes, air-dried at room temperature, and the drying and immersion process was repeated 3 times to obtain the THDH-DMA fluorescent test strip. The test strip was then immersed in Fe at different concentrations. 3+ After immersing the test strip in a (0-10 mg / L) solution for 1 min and allowing it to dry, irradiate it with a 365 nm UV lamp at a 45° angle and a 20 cm range. A fixed mobile phone focus was used to capture fluorescence images, improving data accuracy and reproducibility. Fe was constructed using the Color Picker Version 3.1 App. 3+ The linear regression relationship between concentration and corresponding RGB values ​​was used to calculate the Fe concentration in the sample. 3+ Concentration, to achieve Fe 3+ Intelligent detection.

[0038] 1.8 The method of the present invention is as follows: In this invention, THDH-DMA was synthesized from phthalohydrazide and 2,5-dimethoxy-terephthalaldehyde via a solvothermal reaction. The fluorescence properties of the THDH-DMA material were studied, and subsequently, a fluorescence detection method for Fe based on THDH-DMA was established. 3+ The method was proposed and optimized. It was then applied to a spiked recovery experiment in drinking water, showing high recovery rate and good reproducibility. Finally, a smartphone sensing platform based on THDH-DMA test strips was established to achieve Fe... 3+ Real-time on-site monitoring.

[0039] 1.9 Characterization and Evaluation of THDH-DMA Material Preparation 1.9.1 Field Emission Scanning Electron Microscopy and Transmission Electron Microscopy First, the morphology of the synthesized THDH-DMA was analyzed. SEM images at different magnifications are shown below. Figure 1 a and Figure 1As shown in b, THDH-DMA exhibits a daisy-like nanoflower structure composed of rod-like aggregates, with uniform size and smooth surface. TEM image ( Figure 1 c) This further confirms the smooth rod-like structure of THDH-DMA. Figure 1 d shows that THDH-DMA exhibits a stacked porous structure.

[0040] FT-IR spectra of THDH-DMA and monomers are as follows Figure 2 As shown in figure a, after the reaction, the THDH monomer is at 3319 cm⁻¹. -1 and 3209cm -1 The characteristic peak (NH) disappears and shifts to a lower band at 1678 cm⁻¹, and the DMA monomer at this band is at 1678 cm⁻¹. -1 The stretching vibration at point C=O is reduced. THDH-DMA at 1618 cm⁻¹ -1 The appearance of a new C=N stretching vibration peak indicates that a Schiff base condensation reaction occurred between THDH and DMA monomers, further confirming the successful synthesis of THDH-DMA. The XPS spectrum of THDH-DMA (…) Figure 2 b) shows that THDH-DMA is composed of C, N, and O. The high-resolution XPS spectrum of C 1s ( Figure 2 c) Four peaks appear at 290.68, 287.84, 286.08, and 284.77 eV, representing C=O, CO, C=N, and C=C, respectively. The CO may originate from C-OCH3 on THDH-DMA. In the high-resolution XPS spectrum at N 1s (… Figure 2 In d), the binding energies of C=N and CN are 400.38 and 400.03 eV, respectively. In the high-resolution XPS spectrum at O ​​1s ( Figure 2 e) The two peaks, 532.99 eV and 531.15 eV, represent C=O and CO, respectively. C=O and NH form intramolecular hydrogen bonds, thereby improving the material's stability. These results indicate that THDH and DMA react to form C=N, and the THDH-DMA synthesis was successful.

[0041] The structure of the obtained THDH-DMA polymer was also identified by XRD analysis using Cu-Kα radiation. Figure 3 a). The results show that the broad diffraction peak appearing at 2θ = 23° confirms the amorphous nature of THDH-DMA, which is mainly attributed to its amorphous organic components. To determine the thermal stability of THDH-DMA, a TGA experiment was conducted under a continuous N2 flow. The results show that THDH-DMA exhibits excellent thermal stability, retaining approximately 90% of its mass even at 320 °C. Figure 3b). Furthermore, the microporous properties of THDH-DMA were measured using an N2 adsorption-desorption isotherm at 77 K. The THDH-DMA isotherm exhibits typical type II adsorption isotherms. (e.g.) Figure 3 As shown in Figure c, the N2 adsorption-desorption isotherm does not show a saturation adsorption plateau, indicating that the porous structure of the material is irregular. The pore size distribution curve of THDH-DMA was calculated using the Horvath-Kawazoe method. Figure 3 As shown in the inset, the pore size is mainly distributed at 0.86 nm. The surface area of ​​THDH-DMA was calculated to be 61.62 m² using the Brunauer-Emmet-Teller method. 2 g −1 .

[0042] When THDH-DMA is dissolved in DMF solution, the resulting THDH-DMA solution exhibits stable emission at 465 nm, with a maximum excitation wavelength of 350 nm. Figure 4 a). The CIE chromaticity diagram of THDH-DMA shows that THDH-DMA has blue fluorescence properties ( Figure 4 c), and Figure 4 In a, the color is consistent under ultraviolet light irradiation. Compared with THDH-DMA, the emission spectra of DMA and THDH do not have a significant emission peak at 465 nm. Figure 4 b).

[0043] 1.11 Fe 3+ Establishment of fluorescence detection method

[0044] The fluorescence properties of THDH-DMA in several common solvents were tested at an excitation wavelength of 350 nm. For example... Figure 5 As shown in Figure a, the fluorescence spectrum of THDH-DMA varies with the solvent. THDH-DMA exhibits the strongest fluorescence intensity in DMF and has excellent dispersibility in DMF; therefore, DMF was chosen as the solvent for subsequent fluorescence measurements. Alkaline pH may affect Fe... 3+ The detection of [the virus] caused severe interference, therefore only the fluorescence intensity changes of THDH-DMA under acidic and neutral conditions were tested. For example... Figure 5 As shown in b, an acidic environment causes a slight decrease in the fluorescence intensity of THDH-DMA. The addition of Fe... 3+ Subsequently, the fluorescence of THDH-DMA was quenched to some extent, with the quenching being most pronounced at pH=7; therefore, pH=7 was selected as the optimal detection condition. Furthermore, the reaction between THDH-DMA and Fe was tested. 3+ The reaction time. For example Figure 5 As shown in c, the fluorescence of THDH-DMA after the addition of Fe 3+The quenching was significant afterward, and remained essentially unchanged after 1 minute, indicating that THDH-DMA and Fe... 3+ The reaction is rapid. Simultaneously, Fe is added. 3+ Subsequently, under 365 nm ultraviolet light irradiation, the fluorescence of THDH-DMA changed from blue to green.

[0045] 1.11.2 Fe 3+ Establishment of fluorescence detection method Figure 6 a shows that, under optimal detection conditions, the fluorescence intensity of THDH-DMA increases with the addition of Fe. 3+ The concentration decreased significantly with increasing Fe. 3+ As the concentration of THDH-DMA gradually increases, its fluorescence changes from blue to green under ultraviolet light irradiation, and the intensity gradually decreases. Figure 6 a) Fit the data to the Stern-Volmer equation; the linear fitting curve is as follows: Figure 6 As shown in b, I0 / I and Fe were observed. 3+ There is a linear relationship between concentrations, and the linear fitting equation is y = 0.278x + 1.1363, R0. 2 =0.9970, linear range was 0.01-9 mg / L, LOD was 0.0038 mg / L. These results indicate that the prepared THDH-DMA has a good effect on Fe... 3+ It exhibits excellent fluorescence detection performance, with high correlation and low detection limit over a wide linear range.

[0046] By comparing the addition of Fe 3+ Other metal ions (K) + Na + As 3+ Mn 2+ Hg 2+ Co 2+ Ag + Cu 2+ Zn 2+ and Ni 2+ The fluorescence spectrum and quenching degree of THDH-DMA were used to analyze the effect of THDH-DMA on Fe. 3+ The selectivity. For example... Figure 6 As shown in c, add K + and Na + Subsequently, the fluorescence intensity of THDH-DMA increased after the addition of As. 2+ The fluorescence intensity was comparable after the addition of Fe, 3+Subsequently, the fluorescence intensity of THDH-DMA was significantly quenched. Other ions also reduced the fluorescence intensity of THDH-DMA, but the effect was minor. Fluorescence images of different metal ions under UV light irradiation (…) Figure 6 c) further confirms the above conclusion. All these results indicate that THDH-DMA has a significant effect on Fe... 3+ It exhibits good selectivity. The results of the anti-interference experiment are as follows: Figure 6 As shown in d, after adding Fe 3+ When Fe was mixed with other metal ions in the solution, the fluorescence of THDH-DMA was significantly quenched, indicating that THDH-DMA can still achieve fluorescence suppression of Fe even in the presence of other metal ions. 3+ Selective sensing with minimal interference.

[0047] 1.11.3 Fe in real samples 3+ Detection Fe was successfully detected in tap water and mineral water. 3+ This further confirms the potential of the synthesized THDH-DMA fluorescence sensor in practical applications. To ensure the accuracy and reliability of the experiment, considering that Fe may not exist in real samples... 3+ Ions, therefore need to be added. As shown in Table 1, Fe 3+ The recoveries in real water samples ranged from 97.99% to 104.55%, indicating extremely high accuracy. Furthermore, the RSD for all samples was ≤2.88%, demonstrating the method's excellent precision and good reproducibility.

[0048] Table 1. Detection of Fe in real water samples using THDH-DMA 3+ Performance (mean ± standard deviation) (n = 3) tap water 00.525 ND*0.49 ± 0.142.01 ± 0.225.11 ± 1.36 -2.881.082.67 -97.99100.73102.17 mineral water 00.525 ND0.52 ± 0.111.98 ± 0.545.16 ± 0.63 -2.152.721.21 -104.5599.20103.21 * ND: Not detectable

[0049] Design a ratio measurement sensing platform integrated with a smartphone for measuring Fe. 3+ Perform visual tracking detection ( Figure 7 First, the prepared yellow THDH-DMA test strip was irradiated with a 365 nm ultraviolet lamp. The THDH-DMA test strip turned blue. Figure 7 a). For example Figure 7As shown in b, the fluorescence image of the prepared THDH-DMA test strip at 21 days was consistent with that at the initial stage, indicating that the prepared test strip has excellent stability and can maintain its original properties within 21 days, which is beneficial for storage. Next, the test strips treated with THDH-DMA were immersed in Fe at different concentrations (0, 0.5, 2, 4, 6, 8, 10 mg / L). 3+ In the solution. After the test strip dries, it is irradiated with a 365 nm UV lamp, and a fluorescence image is captured using the built-in camera of a smartphone. Next, RGB analysis is performed. Since RGB analysis can effectively reduce human color perception errors, the free Color Picker app is used to automatically extract the RGB (Red-R, Green-G, and Blue-B) signal values ​​from the fluorescence image. Then, a linear relationship is calculated based on the acquired signal values. For example... Figure 7 As shown in c, different concentrations of Fe were used. 3+ After soaking in the solution, the THDH-DMA test strip showed a significant color change under UV light. After acquiring fluorescence images using an app, the G / B value and Fe ratio were established. 3+ Linear relationship between concentrations. Within the concentration range of 0-10 mg / L, the G / B value and Fe... 3+ The concentrations exhibit an excellent linear relationship (R0). 2 =0.995), the fitted linear equation is G / B = 0.041x + 1.738. Based on LOD = 3σ / k The calculated limit of detection was 0.15 mg / L, which is lower than the limits set by my country and the World Health Organization. Therefore, this experiment demonstrates a portable visualization method based on visual tracking for Fe [specific applications / treatments] without relying on expensive laboratory equipment. 3+ Testing.

Claims

1. The application of a conjugated microporous polymer material for detecting heavy metal iron in drinking water in the preparation of test strips for detecting heavy metal iron in drinking water, wherein the conjugated microporous polymer material for detecting heavy metal iron in drinking water is synthesized by a solvothermal reaction of terephthalohydrazide and 2,5-dimethoxyterephthalaldehyde, wherein the mass ratio of terephthalohydrazide to 2,5-dimethoxyterephthalaldehyde during synthesis is 2:5 to 5:

2.

2. The application as described in claim 1, characterized in that, During synthesis, the mass ratio of terephthalic hydrazide to 2,5-dimethoxyterephthalaldehyde is 1:

1.

3. The application as described in claim 1, characterized in that, The solvent used in the synthesis is o-dichlorobenzene and n-butanol, wherein the volume ratio of o-dichlorobenzene to n-butanol is 10:1 to 1:

1.

4. The application as described in claim 3, characterized in that, The solvents used in the synthesis are o-dichlorobenzene and n-butanol, with a volume ratio of o-dichlorobenzene to n-butanol of 17:

3.

5. The application as described in claim 1, characterized in that, Acetic acid was also added during the synthesis. The mass-to-volume ratio of terephthalic acid hydrazide, 2,5-dimethoxyterephthalaldehyde, and acetic acid was (20~50) mg:(20~50) mg:(0.05~0.5) mL.

6. The application as described in claim 5, characterized in that, The acetic acid concentration is 6M.

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