A cobalt (II) complex single crystal and a preparation method and application thereof

Abstract

This invention belongs to the field of coordination chemistry and adsorption removal of pollutants in water, and discloses a cobalt complex single crystal, its preparation method, and its application. Its chemical formula is: {[Co3L(μ2-O)(DMF)2(H2O)4]·(DMF)3} n It belongs to the monoclinic crystal system and has the space group [missing information]. C 2 / c , a =29.732(6)Å, b =17.665(4)Å, c =31.723(6)Å, α =90°, β =96.99(3)°, gamma =90°, V =16538(6)Å 3 Wherein, L represents 5,11,17,23-tetra[(m-carboxyphenyl)azo]-25,26,27,28-tetrahydroxycalix[4]arene losing four H atoms. The single crystal of this Co(II) complex can rapidly adsorb and remove Pb from water. 2+ Cd 2+ To achieve a high adsorption capacity for Pb 2+ and Cd 2+ It exhibits high selectivity. The single crystals of this cobalt complex are stable in water and show great promise for applications.

Description

Technical Field

[0001] This invention relates to the fields of coordination chemistry and adsorption removal of pollutants in water, specifically to a cobalt complex single crystal, its preparation method, and its application. Background Technology

[0002] Lead (Pb) 2+ Pb is one of the most widely distributed and highly toxic industrial pollutants, capable of accumulating in the human body over a long period, causing serious damage to the brain, liver, kidneys, reproductive system, and immune system. Against the backdrop of rapid industrial and economic growth, Pb... 2+ Pollution has become a significant environmental problem, and almost all countries are focusing their efforts on finding ways to remove Pb from aqueous solutions. 2+ Effective strategies for capturing heavy metal ions include chemical precipitation, redox methods, electrolysis, membrane permeation, ion exchange, and adsorption. Among these, adsorption is highly efficient, simple to operate, and low in cost.

[0003] Trace amounts of cadmium (Cd) 2+ Cadmium is also highly toxic in aquatic media, causing respiratory irritation, and long-term exposure can lead to anosmia, yellowing of the gums, or the gradual formation of yellow rings. Although cadmium compounds are not easily absorbed by the intestines, they can be absorbed into the body through respiration, accumulating in the liver or kidneys and causing harm, especially to the kidneys. To date, a large number of adsorbents have been synthesized, such as alumina, zeolite molecular sieves, activated carbon materials, nanomaterials, and chelated polymers. Most adsorbents face the challenge of moderate selectivity and low absorption capacity due to a lack of structural and functional tunability. Therefore, to achieve effective absorption of Pb in aqueous solutions... 2+ and Cd 2+ The efficient removal of pollutants has led to widespread interest in developing novel adsorbents with tunable structure and function.

[0004] Metal-organic frameworks (MOFs) are framework structures composed of organic ligands and metal ions or metal cluster nodes. Due to their high specific surface area, tunable chemical composition, and tunable pore structure, they have been widely used in the adsorption field (Inorganic Chemistry, 2022, 61, 4, 2017-2030). By selecting ligands with specific functional groups or synthesizing and modifying porous MOFs with specific structures and properties, they can be endowed with special chemical and physical properties for removing heavy metal ions.

[0005] Therefore, by purposefully incorporating different functional groups (carboxylic acid groups, azo groups, etc.) into the pores of MOFs, more active adsorption sites can be obtained for the adsorption and removal of Pb. 2+This is the inventor's current research direction. The inventor's previously granted invention patent 2022104393339, "A single crystal of copper(II) complex and its synthesis method and application," uses it as an adsorbent to adsorb and remove lead ions and iodine from water. However, it has the following shortcomings: 1. The single crystal of copper(II) complex has limited effectiveness against Pb. 2+ The adsorption kinetics are slow, taking approximately 200 minutes to reach adsorption equilibrium; 2. Copper(II) complex single crystals are easily affected by interfering ions. Therefore, the inventors further researched and developed these compounds to achieve selective adsorption of various metal ions. Summary of the Invention

[0006] In view of the current state of technology, the purpose of this invention is to address the issue of Pb. 2+ and Cd 2+ One objective is to provide a single crystal of a cobalt complex with more active adsorption sites; another objective is to provide its preparation method and application.

[0007] To achieve the above-mentioned objectives, the technical solution is as follows:

[0008] The single crystal of the cobalt complex has the chemical formula: {[Co3L(μ2-O)(DMF)2(H2O)4]·(DMF)3} n n is a positive integer, it belongs to the monoclinic crystal system, and its space group is C2 / c. α=90°, β=96.99(3)°, γ=90°, Wherein, L represents 5,11,17,23-tetra[(m-carboxyphenyl)azo]-25,26,27,28-tetrahydroxycalix[4]arene losing four H atoms; DMF represents N,N'-dimethylformamide.

[0009] The method for preparing cobalt complex single crystals according to the present invention:

[0010] Cobalt chloride hexahydrate (0.05 mmol) and H4L (0.01 mmol) were dissolved in N,N'-dimethylformamide and distilled water, sealed in a reaction flask, sonicated at room temperature, placed in a constant temperature oven, and then cooled to room temperature to obtain red blocky crystals, which are the single crystals of the Co(II) complex.

[0011] This complex can be used as an adsorbent for the adsorption and removal of Pb from water. 2+ and Cd 2+ .

[0012] The advantages of this invention are: the three-dimensional framework structure of the Co(II) complex single crystal is modified with functional groups such as carboxylic acid groups and azo groups within the channels, which is beneficial for its interaction with Pb. 2+ This process allows for the rapid adsorption and removal of Pb from the water.2+ This compound achieves a high adsorption capacity, reaching 493.89 mg / g. Furthermore, it can rapidly adsorb and remove lead ions at room temperature; for example, with an initial lead ion concentration of 10 ppm, a single crystal of the Co(II) complex can adsorb and remove 99.44% of Pb within 8 minutes. 2+ Adsorption equilibrium is reached. And for Cd... 2+ It also exhibits good adsorption and removal effects: the adsorption capacity reaches 215.78 mg / g; Cd 2+ In an aqueous solution with an initial concentration of 10 ppm, 83.15% of Cd was removed by adsorption within 180 minutes. 2+ This achieves adsorption equilibrium. Furthermore, adding some common coexisting ions found in water (K+)... + Na + Ca 2+ Mg 2+ and Sr 2+ Under these conditions, the single crystal of this Co(II) complex reacts with Pb. 2+ and Cd 2+ It exhibits high selectivity.

[0013] The synthesis process of this invention is simple and yields a high rate. The cobalt complex single crystals prepared by this invention are stable in water and have excellent application prospects. Attached Figure Description

[0014] Figure 1 This is a diagram showing the coordination environment of cobalt in the cobalt complex crystal of the present invention.

[0015] Figure 2 This is a single-crystal structure diagram of the cobalt complex of the present invention.

[0016] Figure 3 These are diffraction patterns of the cobalt complex of the present invention, wherein 1 is a single-crystal simulated powder diffraction pattern and 2 is a powder diffraction pattern of the cobalt complex of the present invention.

[0017] Figure 4 The cobalt complex of the present invention is effective against Pb in water with different pH values. 2+ Adsorption isotherm diagram.

[0018] Figure 5 The cobalt complex of this invention adsorbs Pb from water 2+ Kinetic diagram of (10ppm).

[0019] Figure 6 The cobalt complex of the present invention has a Pb content of 10 ppm. 2+ Add kinetic curves of different interfering ions.

[0020] Figure 7 The cobalt complex of the present invention is for Cd 2+Adsorption isotherm diagram.

[0021] Figure 8 The cobalt complex of this invention adsorbs Cd from water + Kinetic diagram of (10ppm).

[0022] Figure 9 This is a selective adsorption diagram of the cobalt complex of the present invention. Detailed Implementation

[0023] The invention will be further illustrated by the following examples:

[0024] Example 1: Synthesis of Co(II) single crystal adsorbent

[0025] CoCl₂·6H₂O (0.05 mmol, 11.89 mg), H₄L (0.01 mmol, 10.44 mg), and a mixed solvent (DMF:water = 4.5 mL:4.5 mL) were added to a 10 mL glass bottle. After sonication for 10 minutes, the bottle was sealed and stored in an oven at 100 °C for 24 hours. Then, it was cooled to room temperature to obtain red, blocky Co-MOF crystals. The product was washed with a DMF / water solution (1:1, V / V) and dried at room temperature. Yield: 8.6 mg (45.5%, based on H₄L). The simulated powder diffraction pattern of the single crystal was consistent with the powder diffraction pattern of the actual cobalt complex, confirming the successful synthesis of the material. (See [link to article]). Figure 3 .

[0026] Example 2: Adsorption of Pb by the cobalt complex of the present invention 2+ test

[0027] The red blocky crystals obtained in Example 1 were activated at 120°C for 12 hours, and the powder obtained after grinding for 1 hour was used as an adsorbent. Pb at different pH values ​​(0-250 ppm) was then used in 80 mL of Pb. 2+ 10 mg of the above adsorbent was added to aqueous solutions (0, 10, 30, 40, 60, 100, and 250 ppm), and stirred at room temperature for 8 hours until adsorption equilibrium was reached. The concentration was then determined using atomic absorption spectrometry. Experiments showed that the adsorption capacity of the cobalt complex single crystal of this invention was optimal at pH 7, reaching 493.89 mg / g. (See [reference needed]). Figure 4 .

[0028] In 80 mL of Pb at a concentration of 10 ppm 2+ 10 mg of the above adsorbent was added to an aqueous solution and stirred at room temperature for 30 minutes. Samples were taken at different time points (0, 0.5, 1.5, 3, 5, 8, 15, 20, and 30 minutes) and their concentrations were determined using atomic absorption spectrometry. The experiment showed that 99.44% of the lead ions were adsorbed and removed within 8 minutes. Figure 5This is true for Pb 2+ The excellent removal performance can be attributed to the presence of a large number of accessible carboxylic acid oxygen adsorption sites in the adsorbent framework, demonstrating that the novel cobalt complex single crystal of the present invention has a fast adsorption rate.

[0029] When 10 times the amount of Ca is added to the solution... 2+ Ba 2+ Ni 2+ Mg 2+ 、Sr 2+ K + Na + At that time, it can be found that the adsorbent material is effective against Pb. 2+ The adsorption is slightly affected (Ca). 2+ Ba 2+ and Ni 2+ Three ion pairs of Pb 2+ The adsorption rate decreased slightly, Mg 2+ and Sr 2+ Two ion pairs for Pb 2+ The adsorption rate increased slightly, K + Na + Two ion pairs for Pb 2+ The adsorption rate did not change significantly, but it almost always reached equilibrium within twenty minutes, indicating that the adsorbent material effectively adsorbed Pb. 2+ It has excellent adsorption properties.

[0030] Example 3: Adsorption of Cd by the cobalt complex of the present invention 2+ test

[0031] Different Cd concentrations ranging from 0-200 ppm were measured in 80 mL. 2+ 10 mg of the above adsorbent was added to aqueous solutions (0, 10, 20, 30, 50, 100, and 200 ppm), respectively, and stirred at room temperature for 8 hours until adsorption equilibrium was reached. The concentration was then determined using atomic absorption spectrometry. Experiments showed that the adsorption capacity of the cobalt complex single crystal of this invention reached 215.78 mg / g. Figure 7 .

[0032] In 80 mL of Cd at a concentration of 10 ppm 2+ 10 mg of the above adsorbent was added to an aqueous solution and stirred at room temperature for 540 minutes. Samples were taken at different time points (0, 3, 5, 10, 30, 60, 180, 300, and 540 minutes), and their concentrations were determined using atomic absorption spectrometry. The experiment showed that the adsorbent effectively reduced Cd within 60 minutes. 2+ The adsorption capacity can reach 64.14 mg / g ( Figure 8 This is true for Cd. 2+The excellent removal performance can be attributed to the presence of a large number of accessible carboxylic acid oxygen adsorption sites in the adsorbent framework, demonstrating that the novel cobalt complex single crystal of the present invention has a fast adsorption rate.

[0033] Example 4: Selective adsorption test of the cobalt complex of the present invention

[0034] Add different metal ions (K, K, K) at a concentration of 10 ppm to 80 mL of solution. + Na + Ca 2+ Mg 2+ 、Sr 2+ Pb 2+ and Cd 2 + ), 10 mg of the above adsorbent was added to this solution, and after stirring at room temperature for 12 hours, samples were taken, and the concentrations of different ions were detected using an atomic absorption spectrometer. The experiment showed ( Figure 9 ) for Pb 2+ and Cd 2+ The removal efficiency of Pb remains at 99.53% and 87.34%, while the removal efficiency of other ions is less than 3%, demonstrating that the novel cobalt complex single crystal of this invention effectively removes Pb. 2+ and Cd 2+ It has a high degree of selectivity.

[0035] Further research and development yielded the following results:

[0036] 1. This cobalt(II) complex single-crystal Pb 2+ Adsorption equilibrium can be reached in just ten minutes, and the adsorption rate is extremely fast.

[0037] 2. Adding different interfering ions (Ca) 2+ Ba 2+ Ni 2+ Mg 2+ 、Sr 2+ K + Na + In the case of ), cobalt(II) complex single crystals on Pb 2+ The adsorption rate is not greatly affected, and adsorption equilibrium can be reached within fifteen minutes, indicating a fast adsorption rate.

[0038] 3. The single crystal of this cobalt(II) complex is effective against Cd. 2+ It has certain removal advantages, with a maximum adsorption capacity of 215.78 mg / g.

[0039] 4. The single crystal of this cobalt(II) complex is effective against Pb. 2+ and Cd 2+ It has excellent selective adsorption effect.

[0040] X-ray diffraction experiments were conducted at room temperature on a single crystal of appropriate size, selected under a microscope. The crystal was then monochromated using a Mo-K monochromator on a BrukerSmart Apex-II CCD diffractometer. α ray by Diffraction data were collected using [method name missing]. Data reconstruction was performed using the Bruker SAINT program. Absorption correction was performed on the diffraction data of some structures using the SADABS program. The crystal structure was obtained by direct method combined with Fourier difference synthesis. All non-hydrogen atom coordinates and anisotropy parameters were corrected using full matrix least squares method, and the C–H atom positions were determined according to theoretical models. The coordination environment of metallic cobalt in the complex is shown in [reference missing]. Figure 1 The crystal structure of the coordination compound is shown in [reference needed]. Figure 2 Detailed crystal measurement data are shown in Table 1.

[0041] Table 1. Main crystallographic data of the coordination compounds of the present invention

[0042]

[0043]

Claims

1. A single crystal of a cobalt complex, characterized in that, Its chemical formula is: {[Co3L(μ2-O)(DMF)2(H2O)4]·(DMF)3} n n is a positive integer, it belongs to the monoclinic crystal system, and its space group is C2 / c. β=96.99(3)°, γ=90°, Wherein, L represents 5,11,17,23-tetra[(m-carboxyphenyl)azo]-25,26,27,28-tetrahydroxycalix[4]arene losing four H atoms; DMF represents N,N'-dimethylformamide.

2. The application of the cobalt complex single crystal as described in claim 1, characterized in that, Used to remove Pb from water 2+ and Cd 2+ .

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