Three-dimensional microporous cadmium complex with active sites as well as preparation method and application of three-dimensional microporous cadmium complex

Abstract

The invention discloses a three-dimensional microporous cadmium compound with active sites and a preparation method and application thereof, and belongs to the technical field of chemical sensors, the chemical formula of the complex is [Cd3 (NTC) 2] n.0. 5DMF. 0.5 H2O, NTC is 5-nitrobenzene-1, 2, 3-tricarboxylate radical, and DMF is N, N '-dimethylformamide. The preparation method comprises the following steps: putting H3NTC, BPYP and Cd (CH3COO) 2.2 H2O into a reaction kettle, adding N, N '-dimethylformamide and N, N'-dimethylacetamide, dropwise adding an aqueous solution of HNO3 and H2O, continuously heating the reaction kettle, and cooling to room temperature to obtain the complex. The complex disclosed by the invention is novel in structure, has relatively good thermal stability, can stably exist in water with the pH value of 3.5-10.5, and can be used for high-selectivity and high-sensitivity fluorescence sensing of antibiotic furacilin.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical sensors, in particular to a three-dimensional microporous cadmium complex with active sites, a preparation method and application thereof, and more particularly to a three-dimensional microporous cadmium complex with active sites, a preparation method thereof and application thereof in a chemical sensor for fluorescent detection of furacilin. Background Art

[0002] Antibiotics have been widely used to combat bacterial infections and other microbial diseases since the 1940s. These important compounds are indispensable to human health due to their ability to target pathogenic microorganisms. However, people's increasing reliance on antibiotics has led to major environmental challenges. At present, measuring and detecting antibiotics in wastewater remains a daunting task. The content of furazolidinone in wastewater is often far above the standard, which makes it urgent to develop a highly sensitive and selective method to detect the content of furazolidinone in the environment. In order to limit the detection of furazolidinone to the ppb level, various effective methods have been developed. However, most of the current methods either require expensive equipment, complex techniques, or involve multiple sample operations and time consumption.

[0003] Metal organic frameworks (MOFs) are a class of materials characterized by their different structures, and their applications in CO2 capture, photoluminescence, dye adsorption, magnetism, drug delivery, sensing and photocatalysis have attracted attention. In particular, fluorescent metal-organic framework (LMOFs) compounds with active sites have been rapidly developed in new materials because they can be post-modified in structure, and they play an important role in chemical sensors in particular. Because LMOFs chemical sensors have the characteristics of fast response, convenient application and low cost, it is necessary to develop LMOFs-based chemical sensors to probe antibiotics in the environment.

[0004] Therefore, how to develop a three-dimensional microporous cadmium complex with active sites and its preparation method and application in a chemical sensor for fluorescent detection of furacilin is a technical problem that technical personnel in this field urgently need to solve. Summary of the invention

[0005] In view of this, the present invention provides a three-dimensional microporous cadmium complex with active sites, a preparation method thereof, and an application of the complex in a chemical sensor for fluorescent detection of furacilin.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A three-dimensional microporous cadmium complex with active sites, the chemical formula is: [Cd3(NTC)2] n·0.5DMF·0.5H2O, wherein NTC is 5-nitrobenzene-1,2,3-tricarboxylate and DMF is N,N'-dimethylformamide.

[0008] Furthermore, the three-dimensional microporous cadmium complex is monoclinic, with a space group of I2 / a and a unit cell parameter of α=90°, β=92.047°, γ=90°, Z=8.

[0009] The present invention also provides a method for preparing the three-dimensional microporous cadmium complex having active sites, comprising the following steps:

[0010] 5-nitrobenzene-1,2,3-tricarboxylic acid, 2,5-di(pyridin-4-yl)pyridine and Cd(CH3COO)2·2H2O are put into a reaction kettle, and then N,N'-dimethylformamide and N,N'-dimethylacetamide are added, and then HNO3 aqueous solution and H2O are added dropwise. The reaction kettle is continuously heated and then cooled to room temperature to obtain the above-mentioned three-dimensional microporous cadmium complex crystals with active sites.

[0011] Furthermore, the molar ratio of 5-nitrobenzene-1,2,3-tricarboxylic acid, 2,5-di(pyridin-4-yl)pyridine and Cd(CH3COO)2·2H2O is 2:2:3; 1.5 mL of N,N'-dimethylformamide and 1.5 mL of N,N'-dimethylacetamide are added for every 0.1 mmol of 5-nitrobenzene-1,2,3-tricarboxylic acid, and then 1.5 mL of HNO3 aqueous solution and 3.0 mL of H2O are added dropwise; the mass fraction of the HNO3 aqueous solution is 62%.

[0012] Furthermore, the reactor was heated to 108° C. and the heating was continued for 5 days.

[0013] Further, the temperature was lowered to room temperature at a rate of 5°C / h.

[0014] The present invention also provides an application of the three-dimensional microporous cadmium complex with active sites or the preparation method in a chemical sensor for fluorescent detection of furacilin.

[0015] Beneficial effects of the present invention: The present invention successfully designs and synthesizes a novel three-dimensional microporous cadmium complex with active sites.

[0016] The three-dimensional microporous cadmium complex of the invention has good thermal stability, can stably exist in water with a pH value of 3.5-10.5, and has good practical application value.

[0017] The three-dimensional microporous cadmium complex of the invention can fluorescently sense the antibiotic furacilin with high selectivity and high sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Coordination pattern diagram of two cadmium atoms in compound 1;

[0019] Figure 2 Three-dimensional structure of compound 1;

[0020] Figure 3 Topological diagram of compound 1;

[0021] Figure 4 IR image of compound 1;

[0022] Figure 5 Powder X-ray diffraction pattern of compound 1;

[0023] Figure 6 Thermogravimetric analysis results of compound 1;

[0024] Figure 7 (a) Photoluminescence spectra of compound 1 in pure phase and in the presence of antibiotics; (b) Bar graph showing the change in photoluminescence intensity of compound 1 in the presence of different antibiotics; (c) Photoluminescence spectrum of compound 1 recorded after incremental addition of NFZ; (d) Stern-Volmer plot of compound 1;

[0025] Figure 8 Fluorescence images of compound 1 in the presence of different antibiotics;

[0026] Fig. 9 (a) Interference experiment results of NFZ sensing in the presence of different interfering antibiotics; (b) Cyclic experiment results;

[0027] Fig.10 (a) HOMO-LUMO energies of all antibiotics and compound 1; (b) Hirshfeld surface analysis results;

[0028] Fig.11 The results of the fluorescent test paper experiment, where (a) shows the luminescence of the filter paper strip under visible light; (b) shows the luminescence of the filter paper strip under 365nm UV. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Example 1

[0031] Three-dimensional microporous cadmium complex [Cd3(NTC)2] with active sitesn The preparation method of 0.5DMF 0.5H2O comprises the following steps:

[0032] 0.10mmol of 5-nitrobenzene-1,2,3-tricarboxylic acid (H3NTC, 25.5mg), 0.10mmol of 2,5-di(pyridin-4-yl)pyridine (BPYP, 23.3mg, 0.10mmol) and 0.15mmol of Cd(CH3COO)2·2H2O (34.0mg) were put into a reactor, and then 1.5mL of N,N'-dimethylformamide (DMF) and 1.5mL of N,N'-dimethylacetamide (DMA) were added, and then three drops of 1.5mL of 62% HNO3 aqueous solution and six drops of 3.0mL of H2O were added dropwise. The reactor was heated to 108℃, heated for 5 days, and then cooled to room temperature at a rate of 5℃ / h to obtain a three-dimensional microporous cadmium complex [Cd3(NTC)2] with active sites. n ·0.5DMF·0.5H2O, denoted as compound 1, denoted as 1 in the attached figure. The molecular formula is C 19.5 H 8.5 Cd3N 2.5 O 17 , Elemental analysis (%): Calculated value: C, 26.43; H, 0.96; N, 3.95. Found value: C, 27.13; H, 0.94; N, 5.06.

[0033] 1. Complex [Cd3(NTC)2] n ·0.5DMF·0.5H2O structure determination

[0034] After the crystals of compound 1 were washed with DMF, the crystals with suitable quality and size were selected and placed on a Bruker-AXSSMART CCD X-single crystallometer. The two crystal data were scanned with monochromatic purified Mo-Kα rays (graphite monochromator), where λ is ω is 0.3°, and the diffraction data of two crystals are collected. The diffraction data are restored by SAINT software, and the absorption correction is performed using the SADABS route. The crystal structure is solved by the direct method using SHELXTL software, and (F 2 ) The coordinates of non-hydrogen atoms and hydrogen atoms, isotropic temperature factors and anisotropic temperature factors of compound 1 were refined to convergence by the least square method. The analysis and refinement of compound 1 were completed using the SHELXL-97 program package. The relevant crystallographic data of compound 1 are listed in Table 1.

[0035] Table 1 Crystal data of compound 1

[0036]

[0037]

[0038] 2. Complex [Cd3(NTC)2] n ·0.5DMF·0.5H2O structural description

[0039] The present invention obtains a three-dimensional microporous cadmium compound [Cd3(NTC)2] with active sites under hydrothermal synthesis conditions. n ·0.5DMF·0.5H2O. In compound 1, 2,5-di(pyridin-4-yl)pyridine (BPYP) is not coordinated, and 5-nitrobenzene-1,2,3-tricarboxylic acid is completely protonated and coordinated with the cadmium element. Structural analysis shows that MOF crystallizes in monoclinic space group I2 / a (Table 1). Each asymmetric unit of compound 1 contains two crystallographically independent Cd(II) ions, three NTC 3- Anion, 0.5 DMF and 0.5 free water molecules. NTC 3- The three carboxylates are separated by μ3-η 2 :η 1 , μ2-η 2 :η 1 , μ1-η 1 :η 1 Connecting four Cd(II) ions, NTC 3- This coordination mode of cadmium is rarely reported. Figure 1 The Cd1 center is composed of four different NTCs. 3- The seven oxygen atoms of Cd2 form a severely distorted pentagonal bipyramidal geometry. 3- The eight oxygen atoms of the 8-carbon cation complete the eight-coordination, except that the Cd2 ion is chelated by the eight oxygen atoms of the five carboxylates, with two μ3-η 2 :η 1 、Two μ2-η 2 :η 1 and a μ1-η 1 :η 1 Coordination mode. In compound 1, each Cd4(CO2)6 subunit is connected to four other subunits through four Cd2(CO2)2 units to produce a 3D framework, and the active site extends into the pore ( Figure 2 ). Topological analysis showed that compound 1 could form a 6 Diamond network of symbols ( Figure 3 ).

[0040] 3. Complex [Cd3(NTC)2] n IR, PXRD and TGA of 0.5DMF 0.5H2O

[0041] The infrared (IR) spectrum of compound 1 is as follows Figure 4 In the high frequency region, 3420cm -1 The broad and weak band at represents the hydroxyl group from the guest water molecule. - The groups are at 1631cm1 and 1456cm -1 There are strong bands at - The difference between these two frequencies is 175 cm -1 , indicating that the COO - Bidentate coordination and bridging modes of the groups to the metal center.

[0042] It is well known that the stability of MOFs is crucial to evaluate their sensing potential. In order to determine the stability of compound 1, powder X-ray diffraction (PXRD) analysis was performed, and the results showed that compound 1 has a well-ordered crystal structure ( Figure 5 ). The PXRD patterns simulated based on the crystal structure data were very consistent with those of the synthesized sample, confirming the phase purity of the material. The PXRD pattern of compound 1 remained unchanged after three days of immersion in water, and there was no loss of crystallinity in the sample even after multiple cycles of experiments, indicating the durability and stability of the synthesized MOF.

[0043] The thermal stability of compound 1 was evaluated by thermogravimetric analysis (TGA). Figure 6 The first weight loss of compound 1 occurred between 35°C and 250°C, with a weight loss of 5.05%, which can be attributed to the loss of 0.5 water molecules and 0.5 DMF molecules (theoretical value: 5.14%). The framework of compound 1 is stable up to 290°C, after which the organic matter decomposes.

[0044] 4. Complex [Cd3(NTC)2] n Fluorescence detection and mechanism of antibiotics by 0.5DMF·0.5H2O

[0045] The solid-state photoluminescence spectrum of compound 1 showed a 前 =295nm) emission band ( Figure 7a), attributed to the charge transfer transition from metal to ligand. After characterizing its photoluminescence properties, the fluorescence detection of compound 1 against various commonly used antibiotics, including thiamphenicol (THI), tetracycline (TCY), metronidazole (MDZ), dimetridazole (DTZ), secnidazole (SIZ), nitrofurazone (NFZ), tinidazole (TDZ), sulfasalazine (SLA), ornidazole (ODZ), oxytetracycline (OXY) and sulfadiazine (SMZ) was experimentally investigated. The results showed that the photoluminescence intensity changed to varying degrees when interacting with these antibiotics ( Figure 7 a-7b, Figure 8 Among them, NFZ caused the most significant decrease in photoluminescence intensity, indicating its superior sensing potential for NFZ. Therefore, further studies were conducted to evaluate the luminescence properties of compound 1 towards NFZ ( Figure 7 c). Titration experiments show that in the range of 0.00 to 6.70×10 -4 In addition, the nonlinear Stern-Volmer curves at higher NFZ concentrations indicate that both static and dynamic factors contribute to the quenching of fluorescence emission ( Figure 7 d). Limit of detection (LOD) and Stern-Volmer constant (K) of NFZ SV ) are 3.16×10 -5 M and 4393.6473M -1 .

[0046] Interference experiments were performed to confirm the selectivity of compound 1 for NFZ in the presence of competing antibiotics ( Fig. 9 a). An aqueous solution (1 mM) of each antibiotic was added to a suspension of compound 1, followed by the gradual addition of NFZ. The results showed that the luminescence intensity of compound 1 changed slightly due to the interference of the antibiotics. However, the subsequent introduction of NFZ led to a significant decrease in the photoluminescence intensity, demonstrating that compound 1 has good selectivity for NFZ.

[0047] The reusability of compound 1 as a NFZ sensor was evaluated by a recyclability test. After the sensing cycle, compound 1 was separated from the mixture, immersed in distilled water and subsequently immersed in methanol for 48 h, then filtered and dried under vacuum. The photoluminescence spectrum of the recycled material was measured at the same excitation wavelength of 280 nm, and the experiment showed that its luminescence response was similar to that of the original sample of compound 1 and did not change. In addition, the PXRD pattern of the recycled material was similar to that of the original sample. Figure 1 This demonstrates that compound 1 maintains its crystallinity and phase integrity throughout the sensing process ( Figure 5Moreover, the recycled material exhibited similar sensing performance towards NFZ over five cycles, highlighting its remarkable stability and reusability as a NFZ sensor ( Fig. 9 b).

[0048] To gain more insight into the possible sensing mechanism, computational studies were performed. The HOMO-LUMO energy levels of compound 1 and the studied antibiotics were calculated ( Fig.10 a). These calculations show that the LUMO energy levels of all antibiotics are lower than that of compound 1. Therefore, these antibiotics can potentially accept energy and charge from the photoexcited compound 1, resulting in a decrease in its photoluminescence intensity. However, the observed decrease in luminescence intensity is not completely related to the HOMO-LUMO energy arrangement, indicating that energy transfer alone cannot fully explain the quenching effect. Weak non-covalent interactions between compound 1 and the antibiotics also appear to play an important role in the observed photoluminescence reduction. To further elucidate these interactions, Hirshfeld surface analysis of compound 1 was performed ( Fig.10 b) Between -0.35 and The dnorm plot constructed for compound 1 in the range shows a prominent dark red region corresponding to a significant non-covalent interaction between compound 1 and the analyte ( Fig.10 b) In addition, the fingerprint shows that O…H interactions account for 21.6% of the total interactions. This is evidenced by the symmetrical peaks in the range of . Similarly, the N…H interactions account for 0.2% of the total interactions, characterized by These findings highlight the strong interaction between compound 1 and the antibiotic, which promotes energy transfer and contributes to the observed luminescence quenching. Void volume analysis further confirmed these results, indicating that compound 1 has a mesoporous structure with a void area and volume of and This provides ample active sites for interactions, especially with NFZ.

[0049] 5. Complex [Cd3(NTC)2] n Study on luminescent test paper of 0.5DMF·0.5H2O

[0050] The utility of compound 1 was evaluated using a blue luminescence visible technique. Filter paper strips were dipped into the aqueous suspension of compound 1 and air-dried at room temperature ( Fig.11 ). Under visible light, the test strips remained intact. However, when exposed to 365nm UV light, they exhibited strong blue luminescence. When the test strips were immersed in an aqueous solution of NFZ, the bright blue fluorescence was significantly attenuated, indicating the potential of compound 1 as a highly sensitive and rapid fluorescent probe for the detection of NFZ.

[0051] in conclusion:

[0052] The present invention uses a hydrothermal synthesis method to obtain a novel three-dimensional microporous cadmium metal-organic framework with active sites. The fluorescence sensing of compound 1 to the antibiotic furazolidinone (NFZ) was experimentally studied. It is worth noting that compound 1 shows an extremely low NFZ detection limit (LOD), which is 3.16×10 -5 M. Theoretical analysis showed that the energy transfer and non-covalent interaction between compound 1 and furazolidone drove the sensing mechanism. This study showed that compound 1 has important application prospects in environmental monitoring, health quality control and other fields.

[0053] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A three-dimensional microporous cadmium complex with active sites, characterized in that: The chemical formula is: [Cd3(NTC)2] n ·0.5DMF·0.5H2O, wherein NTC is 5-nitrobenzene-1,2,3-tricarboxylate and DMF is N,N'-dimethylformamide.

2. A three-dimensional microporous cadmium complex with active sites according to claim 1, characterized in that: The three-dimensional microporous cadmium complex is a monoclinic crystal with a space group of I2 / a and a unit cell parameter α=90°, β=92.047°, γ=90°, Z=8.

3. A method for preparing the three-dimensional microporous cadmium complex having active sites according to claim 1 or 2, characterized in that: The steps include: 5-nitrobenzene-1,2,3-tricarboxylic acid, 2,5-di(pyridin-4-yl)pyridine and Cd(CH3COO)2·2H2O are put into a reaction kettle, and then N,N'-dimethylformamide and N,N'-dimethylacetamide are added, and then HNO3 aqueous solution and H2O are added dropwise, the reaction kettle is continuously heated, and then cooled to room temperature to obtain the three-dimensional microporous cadmium complex crystal with active sites.

4. The method for preparing a three-dimensional microporous cadmium complex having active sites according to claim 3, characterized in that: The molar ratio of 5-nitrobenzene-1,2,3-tricarboxylic acid, 2,5-di(pyridin-4-yl)pyridine and Cd(CH3COO)2·2H2O is 2:2:3; 1.5 mL of N,N'-dimethylformamide and 1.5 mL of N,N'-dimethylacetamide are added to every 0.1 mmol of 5-nitrobenzene-1,2,3-tricarboxylic acid, and then 1.5 mL of HNO3 aqueous solution and 3.0 mL of H2O are added dropwise; the mass fraction of the HNO3 aqueous solution is 62%.

5. The method for preparing a three-dimensional microporous cadmium complex having active sites according to claim 3, characterized in that: The reactor was heated to 108°C and heating was continued for 5 days.

6. The method for preparing a three-dimensional microporous cadmium complex having active sites according to claim 3, characterized in that: The temperature was cooled to room temperature at a rate of 5°C / h.

7. Use of the three-dimensional microporous cadmium complex with active sites according to claim 1 or 2 or the preparation method according to any one of claims 3 to 6 in a chemical sensor for fluorescent detection of furacilin.

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