Zinc-based coordination polymer, preparation method and application thereof

Abstract

The present invention discloses a zinc-based coordination polymer, a preparation method and an application thereof. The chemical molecular formula of the zinc-based coordination polymer is: {Zn(dcb) 0.5 (papp) 0.5} n , where n represents the infinite alternating arrangement of the simplest molecular formula of the internal molecular composition of the zinc-based coordination polymer, dcb is 1,4-phthalic acid, and papp is 4-[4-(1H-pyrazol-4-yl)phenyl]-1H-pyrazole); the zinc-based coordination polymer has good water stability and luminescence properties and can be used as an effective fluorescent probe material for detecting Fe in water. 3+ 、CrO4 2‑ and Cr2O7 2‑ .

Description

Technical Field

[0001] The present invention relates to the technical field of metal organic framework materials, and in particular to a zinc-based coordination polymer, a preparation method and applications thereof. Background Art

[0002] Since the rapid rise of modern industry, heavy metal pollution of water and soil has been a problem due to the use of agricultural wastewater, including commercial and artificial waste. Chromium usually exists in oxidized forms, the most common forms are trivalent chromium (III) and hexavalent chromium (VI); among them, hexavalent chromium is considered the most toxic chromium and is usually present as chromate (CrO4 2- ) or dichromate (Cr2O7 2- ) are present in the environment. When ferric iron and chromate ions are present in large quantities in the environment, excess ferric iron can cause an imbalance in the body's oxidative and antioxidant systems, ultimately leading to more serious illnesses. Furthermore, due to the toxicity and carcinogenicity of chromate ions, they can also cause a deterioration in environmental balance and contribute to numerous human diseases. Therefore, the detection and removal of these heavy metal ions has become a hot topic.

[0003] Coordination polymers are a general term for a class of compounds that are self-assembled from metal ions or metal ion clusters and organic molecules. They have one-dimensional, two-dimensional, and three-dimensional structures, and possess variable topological structures and modifiable structures and functions. Azoles and polyazoles are promising ligands that appeared in neutral or anionic forms more than 40 years ago. Due to their multifunctionality, they still play an important role in coordination chemistry. In addition, as d 10 Metal cations, zinc ions are particularly suitable for constructing coordination polymers. Due to the stability of zinc complexes, the formation of coordination bonds is reversible, which allows metal ions and ligands to rearrange during the polymerization process to form a highly ordered network structure. Therefore, zinc can easily adapt to all types of structures and constitute the topological types of one-dimensional, two-dimensional and three-dimensional zinc polymers. However, there are still many challenges in constructing coordination polymers (CPs) as fluorescent probe materials. For example, the poor water stability of coordination polymers will limit the use of CPs to effectively identify metal pollutants in water. Therefore, there is an urgent need to develop a CPs with photodegradation properties and good water stability. Summary of the Invention

[0004] In order to solve the above problems, the present invention proposes a zinc-based coordination polymer, a preparation method and its application. The zinc-based coordination polymer has good water stability and luminescence performance, and can effectively detect Fe in water. 3+ 、CrO4 2- and Cr2O7 2- .

[0005] In order to achieve the above-mentioned object, the embodiment of the present invention provides a zinc-based coordination polymer in the first aspect, whose chemical formula is: {Zn(dcb) 0.5 (papp) 0.5} n , where n represents the infinite alternating arrangement of the simplest molecular formula of the internal molecular composition of the zinc-based coordination polymer, dcb is 1,4-benzenedicarboxylic acid, and papp is 4-[4-(1H-pyrazol-4-yl)phenyl]-1Hpyrazole).

[0006] A zinc-based coordination polymer according to an embodiment of the present invention has good water stability and good fluorescence properties, and can effectively detect trivalent iron, chromate ions and dichromate ions in wastewater.

[0007] Optionally, the zinc-based coordination polymer belongs to the monoclinic system, and the space group is C 2 / c , the unit cell parameters are a (Å) =19.2097 (16), b (Å) = 7.2441(5), c (Å) = 13.5749(12), α (°) = 90, β (°) = 109.098(10), γ (°) = 90; In the zinc-based coordination polymer, each Zn(Ⅱ) ion is bound to two papp - The two nitrogen atoms of the ligand and the 2- The two oxygen atoms of the ligand form a tetrahedral coordination configuration.

[0008] In a second aspect, an embodiment of the present invention provides a method for preparing the above-mentioned zinc-based coordination polymer, which comprises dissolving a mixture of 4-[4-(1H-pyrazol-4-yl)phenyl]-1H-pyrazole, 1,4-phthalic acid and Zn(NO3)2·6H2O in a mixed solution of acetonitrile and water, stirring for 15 minutes, placing the mixture in a polytetrafluoroethylene-lined reactor, and heating at 130°C for 12 hours to obtain a zinc-based coordination polymer with a crystalline structure.

[0009] According to the preparation method of the embodiment of the present invention, a Zn containing pyrazole ligand is synthesized through simple steps. 2+ -CP, the zinc-based coordination polymer has good water stability and good fluorescence properties, and can effectively detect trivalent iron, chromate ions and dichromate ions in wastewater.

[0010] Optionally, the ratio of acetonitrile to water is 2:3.

[0011] In a third aspect, an embodiment of the present invention proposes the use of the above-mentioned zinc-based coordination polymer in the preparation of a fluorescent probe material for detecting cations and / or anions in an aqueous solution.

[0012] According to the application of the embodiment of the present invention, the zinc-based coordination polymer can effectively detect trivalent iron, chromate ions and dichromate ions in wastewater, and can be used for the detection of toxic metal ion pollutants in water.

[0013] Optionally, the zinc-based coordination polymer is capable of detecting the luminescence of cations and / or anions in aqueous solution.

[0014] Optionally, the cation is a trivalent iron ion, and the anion is a chromate ion and / or a dichromate ion.

[0015] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Figures 1 and 2 are a diagram of the coordination environment of Compound 1 according to an embodiment of the present invention (a); a two-dimensional structure of Compound 1 (b); a three-dimensional structure of Compound 1 observed along the AB plane (c); and a topological diagram of Compound 1 (symmetry code: #1: -x+1, y, -z+1 / 2. #2: -x+1, -y+2, -z+1. #3: -x+1 / 2, -y-1 / 2, -z.) (d).

[0017] Figure 2 is an X-ray powder diffraction pattern of compound 1 according to an embodiment of the present invention;

[0018] Figure 3 Is a thermogravimetric analysis of compound 1 according to an embodiment of the present invention;

[0019] Figure 4 is the fluorescence spectrum of the ligand and compound 1 according to an embodiment of the present invention;

[0020] Figure 5 is the X-ray photoelectron spectrum of compound 1 according to an embodiment of the present invention;

[0021] Figure 6 is a high-resolution X-ray photoelectron spectrum of compound 1 according to an embodiment of the present invention;

[0022] Figure 7 is a comparison of the fluorescence intensity of compound 1 according to an embodiment of the present invention in different metal cation aqueous solutions (a); compound 1 for Fe 3+ Competition experiment (b); Compound 1 on Fe 3+Luminescence titration curve with concentration change (c); SV graph (d);

[0023] Figure 8 (a) is a comparison of the fluorescence intensity of compound 1 according to an embodiment of the present invention in different metal anion aqueous solutions; (b) is a comparison of the fluorescence intensity of compound 1 on Cr2O7 2- Competition experiment of compound 1 against CrO4 2- Competition experiments;

[0024] Figure 9 The luminescence titration curve according to the embodiment of the present invention is as follows: 2- and CrO4 2- The concentration change graph and SV graph. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is described below through specific examples. It should be understood that the one or more method steps mentioned in the present invention do not exclude the presence of other method steps before and after the combination step or the insertion of other method steps between these explicitly mentioned steps; it should also be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or to define the scope of the present invention. Changes or adjustments in their relative relationships, without substantially changing the technical content, should also be regarded as the scope of the present invention.

[0026] In order to better understand the above technical solutions, exemplary embodiments of the present invention are described in more detail below. Although exemplary embodiments of the present invention are shown, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0027] The test materials used in the present invention are all common commercial products and can be purchased in the market.

[0028] The present invention is described below with reference to specific examples. It should be noted that these examples are merely illustrative and do not limit the present invention in any way.

[0029] Example 1 {Zn(dcb) 0.5 (papp) 0.5} n (1) Synthesis

[0030] A mixture of 4-[4-(1H-pyrazol-4-yl)phenyl]-1H-pyrazole Hpapp (0.05 mmol, 11 mg), 1,4-benzenedicarboxylic acid H2dcb (0.05 mmol, 12 mg), and Zn(NO3)2·6H2O (0.1 mmol, 29.7 mg) was dissolved in 5 mL of a mixed solution of acetonitrile:water (2:3, v:v) and stirred for 15 min. The mixture was placed in a 25 mL polytetrafluoroethylene-lined reactor and heated at 130°C for 12 h. The reaction system was then cooled to room temperature at a rate of 5°C / h and filtered through filter paper to obtain colorless crystalline compound 1, namely {Zn(dcb) 0.5 (papp) 0.5} n (Wherein, dcb = 1,4-phthalic acid, papp = 4-[4-(1H-pyrazol-4-yl)phenyl]-1H-pyrazole), and n represents the infinite alternation of the compound's internal molecular composition into the simplest molecular formula).

[0031] Example 2

[0032] The product obtained in Example 1 was subjected to elemental analysis, single crystal X-ray diffraction analysis, powder X-ray diffraction (PXRD), and thermogravimetric analysis (TGA). The specific data are as follows:

[0033] Elemental analysis calcd (%): C 34.62; H 1.45; N 40.37; Found (%): C 34.5; H 1.48; N 40.43.

[0034] X-ray single crystal diffraction analysis: the crystals were measured on a Rigaku EosS2 diffractometer in Japan at room temperature and analyzed by Olex2 software.

[0035] X-ray single crystal diffraction showed that compound 1 was a monoclinic space group C 2 / c Medium crystallization. Figure 1 As shown in a, there is a Zn(Ⅱ) ion and a dcb in the asymmetric unit. 2- and a papp - Anion. In compound 1, each Zn(II) ion is bound to two papp - The two nitrogen atoms of the ligand and the two dcb 2- The two oxygen atoms of the ligand form a tetrahedral coordination configuration. The bond length of each Zn-N bond is 1.9858 (19) Å, and the bond length of each Zn-O bond is 1.9401 (17) Å. Zn1 adopts a slightly distorted tetrahedral [ZnN2O2] coordination geometry structure composed of two oxygen atoms and two nitrogen atoms. In addition, papp- and DCB 2- The ligand is attached to the adjacent Zn(II) ion. b A two-dimensional layer with infinite extension is formed on the axis ( Figure 1 b) Then, the two ligands ab stacked on each other on a plane to form an infinitely stacked three-dimensional network ( Figure 1 c) Topological analysis shows that compound 1 can be topologically simplified to ths Type 4 2 -c network, dot notation is {3 2 10 3 ·11}2{3 2 10 4}.

[0036] The purity of subsequent repeated samples of the compound is confirmed by X-ray powder diffraction (PXRD) patterns. At the same time, since the fluorescence sensing process mainly occurs in aqueous solution, the complex needs to have a certain degree of water stability. Figure 2 As shown, due to the high crystallinity of the experimental sample, the characteristic peaks of X-ray powder diffraction (PXRD) are very strong and highly consistent with the simulated PXRD results. In addition, after immersing compound 1 in aqueous solution for 5 days, the PXRD pattern obtained is consistent with that of the original sample, indicating that compound 1 has good water stability.

[0037] The thermal stability of compound 1 was verified by thermogravimetric analysis (TGA). Figure 3 As shown, the main skeleton remains stable up to 425°C, and losses above 425°C can be attributed to skeleton decomposition. PXRD and TGA results demonstrate that compound 1 possesses excellent stability, promising promising fluorescent sensing for the identification of toxic metal ions in water and other potential practical applications. Furthermore, there is no significant mass loss below 425°C, indicating the absence of free water or solvent molecules in compound 1, consistent with the X-ray single crystal diffraction results.

[0038] Example 3 Luminescent Properties of Ligands and Complexes

[0039] In order to explore the luminescence behavior of compound 1, the fluorescence spectra of the ligand and complex were studied at room temperature. Figure 4 As shown, when the ligand dcb 2- At 280 nm (λ ex =280 nm) when excited at 388 nm (λ em =388 nm) has a strong fluorescence emission peak. - At 278 nm (λ ex =278 nm) when excited at 376 nm (λ em=376 nm), which can be explained by the charge transfer within the ligand (π*→π or π*→n). Compared with the ligand, compound 1 has a stronger emission band at 394 nm (λ ex =244 nm). In addition, due to the d 10 The electronic configuration makes it difficult to be oxidized or reduced, so the emission band of compound 1 is neither metal-ligand charge transfer (MLCT) nor ligand-metal charge transfer (LMCT), but rather originates from charge transfer within the ligand, as similar emission bands are also observed in the fluorescence emission spectrum of the ligand. At the same time, compared with the ligand, the position of the maximum emission peak of compound 1 shows a slight red shift, which may be due to the increased π-electron overlap of the organic linker.

[0040] Example 4 XPS analysis

[0041] X-ray photoelectron spectroscopy (XPS) is used to study elemental composition and chemical bonding states. Figure 5 As shown in Figure 1, the survey spectrum shows that the main elements in the sample obtained are C, N, O, and Zn. Figure 6 As shown in a, in the high-resolution XPS spectrum, C 1s shows three characteristic peaks at 288.5, 285.4, and 284.6 eV, which can be attributed to C=O, C-C, and C=C bonds, respectively. The O 1s spectrum shows two different peaks, the peaks at 533.8 and 532.1 eV are attributed to C=O and Zn-O bonds ( Figure 6 b). In the N 1s spectrum, a clear peak is observed at 401.2 eV, which can be attributed to the C-N bond ( Figure 6 c). Figure 6 As shown in d, Zn 2p shows two binding energy peaks at 1022.2 eV and 1045.2 eV, which are respectively attributed to Zn2p 1 / 2 and Zn 2p 3 / 2 The spin-orbit splitting of Zn indicates that Zn is in the 2+ state.

[0042] Example 5 Ion Detection of Compound 1

[0043] Compound 1 was selected for the detection of cations in aqueous solution due to its good stability and excellent luminescence properties. Before the fluorescence sensing experiment, compound 1 was dispersed in M(NO3) with a concentration of 1 mM / L. x (3mL, M=Zn 2+ , Pb 2+ , Ni 2+ , Mn 2+ , Mg2+ , Fe 3+ , Cd 2+ , Ca 2+ , Ba 2+ To ensure uniform dispersion, the fluorescence spectra of compound 1 immersed in different metal ion aqueous solutions were recorded after ultrasonic treatment for 30 min. Figure 7 As shown in a, compared with other metal ions, compound 1 has a 3+ The fluorescence emission band in aqueous solution was almost quenched. The results showed that compound 1 can effectively recognize Fe in water. 3+ Further competition experiments were conducted under the same conditions to study the effect of compound 1 on Fe 3+ Selective recognition. Figure 7 As shown in b, after adding other metal ions in equal molar ratio, Fe 3+ It can still quench the fluorescence emission peak of compound 1, indicating that compound 1 can selectively recognize Fe in water. 3+ .

[0044] In order to further study the effect of compound 1 on Fe 3+ The detection limit of , a titration sensing experiment was carried out. Figure 7 As shown in c, with the Fe 3+ As the concentration gradually increased from 0 μL to 1000 μL, the emission band intensity of compound 1 gradually decreased. Within this range, the Stern-Volmer (SV) equation ( I 0 / I )=K SV [M]+1 calculated the corresponding quenching constant and obtained Fe 3+ K SV The value is 2.6 6×10 3 M -1 According to the formula 3δ / K SV (δ is the standard deviation) Calculate Fe 3+ The detection limit was 12.3 μM.

[0045] Next, the fluorescence sensing ability of compound 1 to anions was studied. Similarly, compound 1 was immersed in aqueous solutions containing different anions and the fluorescence spectra of compound 1 to different anions were recorded after ultrasonic treatment for 30 min. Figure 8 As shown in a, compared with other anions, CrO4 2- and Cr2O7 2- It has a strong quenching effect on the emission peak of compound 1. In order to study the effect of compound 1 on CrO4 2- and Cr2O7 2- For the selective detection of , a competition experiment was conducted at an equimolar ratio. Figure 8 b and Figure 8As shown in c, when adding CrO4 in equal molar ratio 2- 、Cr2O7 2- After other anions, CrO4 2- and Cr2O7 2- The emission peak intensity of compound 1 still has a strong quenching effect, indicating that compound 1 has a strong quenching effect on CrO4 2- and Cr2O7 2- Has good selective recognition.

[0046] The effect of compound 1 on Cr2O7 was studied by titration experiment. 2- and CrO4 2- The detection limit of Figure 9 a and Figure 9 As shown in c, with the 2- and CrO4 2- With the increase of concentration, the fluorescence emission peak intensity of compound 1 continues to decrease. According to the Stern-Volmer (SV) equation ( I 0 / I )=K SV [M] + 1, calculate Cr2O7 2- The Ksv is 5.87×10 3 M -1 , CrO4 2- The Ksv is 4.68×10 3 M -1 According to 3δ / K SV Formula to calculate Cr2O7 2- and CrO4 2- The detection limits were 5.57 μM and 6.99 μM, respectively.

[0047] In summary, according to the embodiment of the present invention, a Zn-containing pyrazole ligand was synthesized. 2+ -CP. Compound 1 has good stability and good fluorescence properties, and its preparation method is simple. At the same time, compound 1 can effectively detect trivalent iron and chromate ions in wastewater, providing an excellent detector for the detection of toxic metal ion pollutants in water.

[0048] In the description of this specification, reference to the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms should not be understood as necessarily referring to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification.

[0049] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A zinc-based coordination polymer, characterized in that The chemical formula is: {Zn(dcb) 0.5 (papp) 0.5 } n , where n represents the infinite alternating arrangement of the simplest molecular formula of the internal molecular composition of the zinc-based coordination polymer, dcb is 1,4-benzenedicarboxylic acid, and papp is 4-[4-(1H-pyrazol-4-yl)phenyl]-1Hpyrazole); the zinc-based coordination polymer belongs to the monoclinic system and has a space group of C 2 / c , the unit cell parameters are a (Å) = 19.2097 (16), b (Å) = 7.2441(5), c (Å) = 13.5749(12), α (°) = 90, β (°) = 109.098(10), γ (°) = 90; In the zinc-based coordination polymer, each Zn(Ⅱ) ion is bound to two papp - The two nitrogen atoms of the ligand and the 2- The two oxygen atoms of the ligand form a tetrahedral coordination configuration.

2. A method for preparing a zinc-based coordination polymer according to claim 1, characterized in that: include: A mixture of 4-[4-(1H-pyrazol-4-yl)phenyl]-1H-pyrazole, 1,4-benzenedicarboxylic acid and Zn(NO3)2·6H2O was dissolved in a mixed solution of acetonitrile and water, stirred for 15 min, placed in a polytetrafluoroethylene-lined reactor, and heated at 130°C for 12 h to obtain a zinc-based coordination polymer with a crystalline structure.

3. The preparation method according to claim 2, wherein The volume ratio of acetonitrile and water was 2:

3.

4. Use of the zinc-based coordination polymer according to claim 1 in preparing a fluorescent probe material for detecting cations and / or anions in an aqueous solution; wherein the cation is a trivalent iron ion and the anion is a chromate ion and / or a dichromate ion.

5. The use according to claim 4, characterized in that The zinc-based coordination polymer is used to detect the luminescence ability of cations and / or anions in aqueous solution.

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