Nickel-based complex as well as preparation method and application thereof

Abstract

The invention discloses a nickel-based complex as well as a preparation method and application thereof, and belongs to the technical field of functional materials. According to the nickel-based complex, N-(3-carboxyl phenyl) iminodiacetic acid, nickel salt and phenanthroline serve as raw materials, and the zero-dimensional mononuclear nickel-based complex is prepared. The preparation method of the nickel-based complex is mild in condition and simple in process. Crystal structure analysis shows that the complex belongs to a triclinic system space group, a three-dimensional supramolecular network is formed among molecules through O-H... O hydrogen bonds, and the complex has excellent structural stability and thermal stability. The nickel-based complex can be used as an efficient heterogeneous catalyst to activate peroxymonosulfate to degrade methylene blue dye, shows good catalytic activity and reusability, and has important application prospects in the field of dye wastewater treatment.

Description

Technical Field

[0001] This invention relates to the field of functional materials technology, specifically to a nickel-based complex, its preparation method, and its application. Background Technology

[0002] Organometallic complexes are porous crystalline materials composed of metal ions and organic ligands, possessing advantages such as high specific surface area, strong structural designability, and excellent functional properties. These properties make them a research hotspot in the interdisciplinary field of materials chemistry and coordination chemistry, and they are widely used in gas storage and separation, photoelectrocatalysis, proton conduction, chemical sensing, adsorption, and antibacterial applications.

[0003] The dye wastewater discharged during the production processes of traditional industries such as textiles and papermaking places enormous pressure on the current ecological environment. This type of wastewater contains a large amount of structurally stable, poorly biodegradable, and biotoxic dye substances, causing a sharp increase in the color of receiving water bodies and posing a persistent threat to ecosystem safety and human health. Based on sulfate (SO4) 2- Advanced oxidation processes (AOPs) demonstrate significant water purification potential due to their green, efficient, and convenient nature. Peroxymonosulfate (PMS, HSO5) - Due to its asymmetric molecular structure and low O / O bond dissociation energy (≈ 377 kJ·mol⁻¹), -1 It can catalytically decompose into various reactive oxygen species, including sulfate radicals (SO4). ·- ), hydroxyl radicals (·OH), superoxide radicals (O2) ·– ) and singlet oxygen ( 1 PMS exists in a water-soluble solid form, making it easy to store and transport. However, PMS has limited self-oxidizing capacity and requires external activation energy or a catalyst to break the O2-O2 bond, resulting in homogeneous transition metal ions (Ni). 2+ Co 2+ Mn 2+ Fe 2+ Although these substances (such as metal ions) are rapidly activated, they have problems such as easy dissolution of metal ions, difficulty in recycling, and easy secondary pollution.

[0004] Therefore, developing a novel material with stable structure that can efficiently activate peroxymonosulfate (PMS) to degrade organic pollutants is of great value in solving the problem of dye wastewater treatment. Summary of the Invention

[0005] To address the problems of difficult recovery and secondary pollution associated with homogeneous metal activators containing peroxymonosulfate, the present invention aims to provide a nickel-based complex with the chemical formula [Ni(3-Hcpida)(phen)(H2O)]·2H2O, where Ni represents a divalent nickel ion, and 3-Hcpida...2- represents a divalent anion of N-(3-carboxyphenyl) iminodiacetic acid losing two protons, phen represents orthophenanthroline which is electrically neutral, H2O represents a water molecule; the crystal structure of the nickel-based complex belongs to triclinic system space group, and the cell parameters are: a=9.078 Å, b=10.023 Å, c=14.302 Å; α = 82.44°, β = 72.39°, gamma = 79.72°.

[0006] Another object of the present application is to provide a preparation method of the nickel-based complex, specifically comprising the following steps: dissolving N-(3-carboxyphenyl) iminodiacetic acid in a mixed solution of water and methanol to obtain a mixed system, adjusting the pH of the mixed system, adding a nickel salt, stirring to react, then adding orthophenanthroline, continuing to stir to react at the same temperature, filtering, and standing to obtain the nickel-based complex.

[0007] Preferably, the molar ratio of the N-(3-carboxyphenyl) iminodiacetic acid, the nickel salt and the orthophenanthroline is (1-2):1:(1-2).

[0008] Preferably, the volume ratio of water and methanol in the mixed solution is (1-3):1.

[0009] Preferably, the concentration of the N-(3-carboxyphenyl) iminodiacetic acid ligand in the mixed system is 0.025-0.05 mol·L -1 .

[0010] Preferably, the adjustment of the pH of the mixed system specifically comprises: adjusting the pH of the mixed system to 4-6 by adding KOH or NaOH.

[0011] Preferably, the nickel salt is one of nickel chloride hexahydrate, nickel nitrate hexahydrate and nickel sulfate hexahydrate.

[0012] Preferably, the conditions of the stirring to react are all: stirring to react for 0.5-1 hour at room temperature; and the standing conditions are: sealing and standing for 3-7 days at room temperature.

[0013] Another object of the present application is to provide an application of the nickel-based complex in catalytic degradation of methylene blue dye by activated peroxy monosulfate.

[0014] The mechanism of the present application is: in the nickel-based complex, the Ni(II) ion presents a six-coordinated distorted octahedral {NiN3O3} configuration, the N-(3-carboxyphenyl) iminodiacetic acid (3-Hcpida 2-The O and N atoms of its flexible iminodiacetic acid group coordinate with Ni to form two five-membered chelate rings. This coordination mode helps stabilize the metal center and regulate its electronic structure. The o-phenanthroline, as a strong field chelating ligand, further enhances the stability of the Ni(II) center. Its electron-rich aromatic ring system may participate in the electron transfer process, thereby effectively inhibiting Ni ion leaching and optimizing the Ni(II) / Ni(III) redox couple, promoting the heterolytic activation of O–O bonds in peroxymonosulfate (PMS). The zero-dimensional mononuclear complex is extended into a three-dimensional supramolecular network through the O–H···O hydrogen bonding between the uncoordinated carboxyl oxygen and the coordinated water / crystallization water. The dense hydrogen bond network significantly improves the structural integrity, thermal stability and chemical stability of the material, which helps to fix the active center and enable the stable Ni(II) to efficiently and cyclically activate PMS. It may generate reactive oxygen species mainly composed of sulfate radicals and singlet oxygen through the electron transfer pathway. The hydrogen bond network formed between complex molecules and the π–π stacking interaction between o-phenanthroline and benzene ring work synergistically to provide an effective mass transfer channel and enrichment interface for the reactants (methylene blue) and reactive oxygen species, thereby accelerating surface reaction kinetics and achieving efficient degradation of pollutants.

[0015] This invention provides a nickel-based complex, its preparation method, and its application, which have the following beneficial effects: (1) The present invention uses N-(3-carboxyphenyl)iminodiacetic acid and o-phenanthroline as organic ligands to construct crystalline nickel-based complexes under normal temperature and pressure conditions. The method is simple, does not require high temperature and high pressure or special equipment, the reaction conditions are mild and controllable, the raw materials are readily available, and it is suitable for large-scale preparation. It has good process feasibility and economy.

[0016] (2) The nickel-based complex of the present invention has a zero-dimensional mononuclear structure, which forms a three-dimensional supramolecular network through hydrogen bonding. The crystal structure is well-defined and belongs to the triclinic crystal system. It is a space group and exhibits good thermal and chemical stability.

[0017] (3) The nickel-based complex provided by the present invention is a novel heterogeneous catalyst that exhibits the ability to efficiently activate peroxymonosulfate (PMS) and can efficiently degrade methylene blue dye. Compared with traditional homogeneous metal catalysts, this material can effectively inhibit the dissolution of metal ions, avoid secondary pollution, and has good recyclability and reusability. After being recycled 4 times, the degradation rate is still above 88.8%, which meets the requirements of green environmental protection and sustainable development. The present invention not only provides a high-performance PMS activator for advanced oxidation processes, but also expands the application prospects of crystalline complex materials in the field of wastewater treatment, and has important scientific value and engineering application potential. Attached Figure Description

[0018] Figure 1 This is a diagram of the asymmetric structural unit of the nickel-based complex prepared in Example 1 of the present invention.

[0019] Figure 2 This is a three-dimensional hydrogen bond packing diagram of the nickel-based complex prepared in Example 1 of the present invention.

[0020] Figure 3 The infrared spectrum of the nickel-based complex prepared in Example 1 of this invention is shown.

[0021] Figure 4 The image shows the powder X-ray diffraction (PXRD) pattern of the nickel-based complex prepared in Example 1 of this invention.

[0022] Figure 5 This is a scanning electron microscope (SEM) image of the nickel-based complex prepared in Example 1 of the present invention.

[0023] Figure 6 The thermogravimetric (TG) curve of the nickel-based complex prepared in Example 1 of this invention is shown.

[0024] Figure 7 This describes the activation of PMS to degrade MB by the nickel-based complex prepared in Example 1 of this invention.

[0025] Figure 8 The results of cycling the nickel-based complex prepared in Example 1 of this invention to activate PMS and degrade MB are shown.

[0026] Figure 9 The image shows a comparison of powder X-ray diffraction (PXRD) spectra of the nickel-based complex prepared in Example 1 of this invention before and after the activation of PMS to degrade MB. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1 The preparation of a nickel-based complex, wherein the molar ratio of N-(3-carboxyphenyl)iminodiacetic acid, nickel chloride hexahydrate, and o-phenanthroline is 2:1:2, specifically includes the following steps: N-(3-Carboxyphenyl)iminodiacetic acid was dissolved in a mixed solution of water and methanol (volume ratio of water to methanol was 1:1) to obtain a mixed system (the concentration of N-(3-carboxyphenyl)iminodiacetic acid in the mixed system was 0.05 mol·L⁻¹).-1 Add NaOH to adjust the pH of the mixture to 5, add nickel chloride hexahydrate, stir and react at room temperature for 1 hour, then add o-phenanthroline, and continue stirring and reacting at the same temperature for 0.5 hours to obtain a light blue solution. Filter the solution into a beaker, seal it at room temperature and let it stand for 3 days to obtain a nickel-based complex (light blue rod-shaped crystals).

[0029] X-ray diffraction analysis revealed that the crystal structure of this nickel-based complex belongs to the triclinic crystal system. Space group, cell parameters: a = 9.078 Å, b = 10.023 Å, c = 14.302 Å; α =82.44°, β =72.39° gamma =79.72°.

[0030] like Figure 1 and Figure 2 As shown, the asymmetric structural unit of the nickel-based complex [Ni(3-Hcpida)(phen)(H2O)]·2H2O prepared in this embodiment contains one Ni(II) ion and one 3-Hcpida ion. 2- The ligand consists of a chelated phen ligand, a coordinated water molecule, and two free water molecules. The six-coordinated Ni1 center is associated with 3-Hcpida. 2- The two oxygen atoms (O2, O5) and one nitrogen atom (N3) of the ligand, the two nitrogen atoms (N1, N2) from the phen ligand, and the one oxygen atom (O1) from the coordinated H2O molecule form a twisted octahedral {NiN3O3} coordination environment; structurally, 3-Hcpida 2- Two NiNC2O five-membered chelate rings are formed by the coordination of the nitrogen atom and two monodentate carboxylate groups on the flexible iminodiacetic acid ester group with Ni(II); simultaneously, the two nitrogen atoms of the phen ligand form a five-membered ring with Ni(II) through chelate coordination. Therefore, one Ni(II) ion and one 3-Hcpida 2- The ligand and a phen ligand constitute a zero-dimensional mononuclear complex, 3-Hcpida 2- The ligands and coordinating H2O molecules act as bridging units, connecting adjacent core units through O–H··O hydrogen bond interactions to form a three-dimensional hydrogen bond stacking structure.

[0031] Figure 3 The infrared spectrum of the nickel-based complex, 3500 cm⁻¹ -1 The broad and strong infrared peak corresponds to the OH stretching vibration of water molecules, indicating the presence of water molecules in the structure; 1606 cm⁻¹ -1 and 1427 cm -1The position corresponds to the asymmetric and symmetric (-COO) stretching vibrations of the carboxylic acid ligand; at approximately 1700 cm⁻¹ -1 The presence of a characteristic band at 1614 cm⁻¹ indicates partial deprotonation of 3-H₃cpida. -1 1521 cm -1 1490 cm -1 1433 cm -1 848 cm -1 727 cm -1 The characteristic peak of phenanthroline was observed at 400 cm⁻¹. -1 Up to 1000 cm -1 The absorption peaks in the range indicate the characteristic absorption of the CH bending vibration of the benzene ring skeleton. The above infrared analysis fully demonstrates that the two ligands have successfully coordinated with the central metal.

[0032] Figure 4 PXRD patterns and simulated single-crystal PXRD patterns of nickel-based complexes are shown. Figure 4 It can be seen that the position of the upper peak in the PXRD pattern of the complex is basically consistent with that in the simulated PXRD pattern of the single crystal, indicating that the obtained powder and the tested single crystal are the same substance and the powder has a high purity.

[0033] Figure 5 This is a scanning electron microscope (SEM) image of the nickel-based complex. Figure 5 It can be seen that the obtained nickel-based complex has a smooth cubic structure with clear edges, indicating high crystallinity.

[0034] Figure 6 This is the thermogravimetric curve of the nickel-based complex. Figure 6 It can be seen that the nickel-based complex shows that the initial dehydration occurs at 40°C, with an experimental mass loss of 12.0% (theoretical value: 9.92%), corresponding to the removal of two guest water molecules and one coordinated water molecule. Its structure then begins to collapse at 330°C, exhibiting good thermal stability.

[0035] The nickel-based complex prepared in Example 1 was used to degrade methylene blue (MB) in water. Both dark adsorption and photocatalytic reaction were carried out in a multi-channel photocatalytic reaction system. Specifically, the complex was added to 50 mL of MB dye wastewater (MB concentration was 20 mg·L⁻¹). -1 The nickel-based complex obtained in Example 1 was added to the mixture at an amount of 0.20 g·L⁻¹. -1 Stir for 30 minutes in the dark to reach adsorption-desorption equilibrium, then add 0.20 g·L⁻¹ -1A PMS (Probe-Modulated Microsphere) was used to simulate sunlight conditions at room temperature, with a 10 W xenon lamp as the source. At regular intervals, 2 mL of the supernatant was drawn using a syringe with a filter, and the absorbance of the mixture was measured using a UV-Vis spectrophotometer and compared with that of the control group.

[0036] Without the addition of PMS, the nickel-based complex exhibited extremely low degradation rates for methylene blue, reaching only 4.46% within 30 minutes. This inefficiency is primarily due to its limited adsorption capacity. When PMS was used alone, the degradation rate was only 24.4% within 30 minutes, indicating that PMS is difficult to activate without the complex. However, the nickel-based complex / PMS system significantly improved the MB degradation efficiency to 99.0% (see details). Figure 7 This indicates that the nickel-based complex is a good co-catalyst for activating PMS to degrade MB dyes and can be used to degrade pollutants in water.

[0037] Reusability testing of nickel-based complexes for MB dye degradation, such as... Figure 8 As shown, the nickel-based complex prepared in Example 1, after four cycles of activated PMS degradation of MB, still maintained a degradation efficiency of 88.8% for MB. Furthermore, by comparing the PXRD spectra of the freshly prepared nickel-based complex and those after four cycles (…),… Figure 9 It was found that although the intensity of the characteristic diffraction peaks decreased slightly, the positions of the main diffraction peaks remained basically unchanged, and no signs of impurity phase formation or framework structure collapse were observed, indicating that the catalyst maintained good structural stability and reusability during the reaction process.

[0038] Example 2 The preparation of a nickel-based complex, wherein the molar ratio of N-(3-carboxyphenyl)iminodiacetic acid, nickel nitrate hexahydrate, and o-phenanthroline is 1:1:2, specifically includes the following steps: The N-(3-carboxyphenyl)iminodiacetic acid ligand was dissolved in a mixed solution of water and methanol (volume ratio of water to methanol: 2:1) to obtain a mixed system (the concentration of N-(3-carboxyphenyl)iminodiacetic acid ligand in the mixed system was 0.04 mol·L⁻¹). -1 KOH was added to adjust the pH of the mixture to 4, nickel nitrate hexahydrate was added, and the mixture was stirred at room temperature for 0.5 hours. Then o-phenanthroline was added, and the mixture was stirred at the same temperature for another 0.75 hours to obtain a light blue solution. The solution was filtered into a beaker, sealed at room temperature, and allowed to stand for 5 days to obtain a nickel-based complex (light blue rod-shaped crystals).

[0039] The effect of the nickel-based complex prepared in this embodiment on activating PMS to degrade MB dye is similar to that in Example 1.

[0040] Example 3 The preparation of a nickel-based complex, wherein the molar ratio of N-(3-carboxyphenyl)iminodiacetic acid, nickel sulfate hexahydrate, and o-phenanthroline is 1:1:1, specifically includes the following steps: The N-(3-carboxyphenyl)iminodiacetic acid ligand was dissolved in a mixed solution of water and methanol (volume ratio of water to methanol: 3:1) to obtain a mixed system (the concentration of N-(3-carboxyphenyl)iminodiacetic acid ligand in the mixed system was 0.025 mol·L⁻¹). -1 Add NaOH to adjust the pH of the mixture to 6, add nickel sulfate hexahydrate, stir and react at room temperature for 0.75 hours, then add o-phenanthroline, and continue stirring and reacting at the same temperature for 1 hour to obtain a light blue solution. Filter the solution into a beaker, seal it at room temperature and let it stand for 7 days to obtain a nickel-based complex (light blue rod-shaped crystals).

[0041] The effect of the nickel-based complex prepared in this embodiment on activating PMS to degrade MB dye is similar to that in Example 1.

[0042] In summary, this invention uses N-(3-carboxyphenyl)iminodiacetic acid, nickel salt, and o-phenanthroline as raw materials to prepare a triclinic nickel-based complex. The synergistic effect of N-(3-carboxyphenyl)iminodiacetic acid and o-phenanthroline enhances the stability of the Ni(II) center. This complex expands to form a three-dimensional supramolecular network through O–H···O hydrogen bonding between uncoordinated carboxyl oxygen and coordinated water / water of crystallization. This dense hydrogen bond network greatly enhances the structural integrity and thermal / chemical stability of the crystal. During catalysis, this network can effectively fix the active center and prevent structural dissociation, achieving efficient degradation of MB. After recycling, it can still maintain high crystallinity and activity, and has good structural stability and reusability, showing significant application potential in the fields of dye wastewater treatment and environmental pollution control.

[0043] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A nickel-based complex, characterized in that, The nickel-based complex has the chemical formula [Ni(3-Hcpida)(phen)(H2O)]·2H2O, where Ni represents a divalent nickel ion, and 3-Hcpida 2- The symbol represents the divalent anion of N-(3-carboxyphenyl)iminodiacetic acid after losing two protons; phen represents the electrically neutral o-phenanthroline; and H2O represents a water molecule.

2. The nickel-based complex according to claim 1, characterized in that, The crystal structure of the nickel-based complex belongs to the triclinic crystal system. Space group, cell parameters: a = 9.078 Å, b = 10.023 Å, c = 14.302 Å; α =82.44°, β =72.39° γ =79.72°.

3. The method for preparing the nickel-based complex according to claim 1 or 2, characterized in that, Specifically, the following steps are included: N-(3-carboxyphenyl)iminodiacetic acid was dissolved in a mixed solution of water and methanol to obtain a mixed system. The pH of the mixed system was adjusted, a nickel salt was added, and the reaction was stirred. Then o-phenanthroline was added, and the reaction was continued to be stirred while maintaining the same temperature. After filtration and standing, a nickel-based complex was obtained.

4. The method for preparing the nickel-based complex according to claim 3, characterized in that, The molar ratio of N-(3-carboxyphenyl)iminodiacetic acid, nickel salt and o-phenanthroline is (1~2):1:(1~2).

5. The method for preparing the nickel-based complex according to claim 3, characterized in that, The volume ratio of water to methanol in the mixed solution is (1~3):

1.

6. The method for preparing the nickel-based complex according to claim 3, characterized in that, The concentration of N-(3-carboxyphenyl)iminodiacetic acid in the mixture is 0.025~0.05 mol·L⁻¹. -1 .

7. The method for preparing the nickel-based complex according to claim 3, characterized in that, The pH adjustment of the mixing system is specifically achieved by adding KOH or NaOH to adjust the pH of the mixing system to 4-6.

8. The method for preparing the nickel-based complex according to claim 3, characterized in that, The nickel salt is one of nickel chloride hexahydrate, nickel nitrate hexahydrate, and nickel sulfate hexahydrate.

9. The method for preparing the nickel-based complex according to claim 3, characterized in that, The stirring reaction conditions are as follows: stirring reaction at room temperature for 0.5 to 1 hour; the standing conditions are as follows: sealing and standing at room temperature for 3 to 7 days.

10. The application of the nickel-based complex according to claim 1 or 2 in the catalytic degradation of methylene blue dye by activated peroxymonosulfate.

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