A two-dimensional coordination polymer material based on flexible ligands has good removal capacity for mercury ions

Abstract

A two-dimensional non-Hofmann type coordination polymer based on K2[Hg(SCN)4] and flexible bidentate sulfur-based pyridine ligand, which is formed by a neutral two-dimensional network of {Fe[Hg(SCN)4](L)} n (L represents bis (4-pyridylthio) methane). The preparation method is: the aqueous solution of K2[Hg(SCN)4], the ligand L and the methanol solution of FeCl2 are sequentially placed in a three-arm H-shaped tube, sealed and placed in dark for two weeks to obtain yellow maple leaf-shaped crystals. The advantages of the present application are: the non-Hofmann type structure of the complex provides sufficient adsorption sites, the bonding force between the sulfur element in the bridging ligand and the mercury ion serves as the adsorption driving force, so that the adsorption rate of the complex is stably maintained at 38±2% under the test conditions that the concentration of HgCl2 is 50-8500 ppm, when the concentration of HgCl2 reaches 8500 ppm, the adsorption amount of mercury ion per milligram of complex reaches 4.25 mg, and the complex maintains a good crystal lattice structure before and after adsorption, and has potential application value in the aspects of green chemical industry, clean chemical process production and the like.

Description

Technical Field

[0001] This invention belongs to the field of synthesis technology of non-Hoffmann coordination polymers with mercury ion removal performance, specifically involving the synthesis of a two-dimensional non-Hoffmann coordination polymer material based on K2[Hg(SCN)4] and flexible bidentate thiopyridine ligands and the study of its mercury ion removal capability. Background Technology

[0002] Mercury is a highly toxic heavy metal, exhibiting persistence, bioaccumulation, and toxicity. Mercury ions not only threaten natural ecosystems but also seriously affect human health. Researchers are actively exploring new strategies for the effective removal of these harmful ions. The total concentration of mercury in natural water ranges from approximately 0.2 to 100 mg / L, while China's industrial wastewater discharge standards strictly require that the concentration of mercury ions not exceed 0.05 mg / L. Therefore, for systems requiring ultra-low mercury ion concentrations, there is an urgent need to develop materials capable of effectively adsorbing and removing mercury ions. Adsorption materials are typically simple, efficient, and low-cost, thus possessing broad application prospects.

[0003] Coordination polymers are a typical type of advanced porous material. Constructing coordination polymers by functionalizing ligands and then combining them with metal ions / clusters often yields significant advantages, such as large specific surface area, flexible customizability, controllable structure, and high porosity, thus attracting considerable attention from researchers. The synergistic effect of functionalized ligands and unique porous structures in coordination polymers provides a powerful platform for constructing complete adsorbents. Based on these advantages, coordination polymers are increasingly being used in homogeneous / heterogeneous catalysis, selective capture, and adsorption. (Chen, DM, Zhang, NN, Liu, CS, Du, M. Acs Appl Mater Inter, 2017, 9(29), 24671-24677. Mon, M., Ferrando-Soria, J., Verdaguer, M., Train, C., Paillard, C., Dkhil, B., Pardo, E. J Am Chem Soc J, 2017, 139(24), 8098-8101.) Furthermore, non-Hoffmann coordination polymers exhibit good thermal and chemical stability in aqueous solutions over a wide pH range. They are simple to synthesize, easy to handle, and have high application value. This invention reveals the application potential of non-Hoffmann coordination polymers constructed using K2[Hg(SCN)4] and flexible bidentate thiopyridine ligands as modules for mercury ion adsorption. Summary of the Invention

[0004] This invention provides a two-dimensional non-Hoffmann coordination polymer material with good removal ability for mercury ions. To achieve the above objective, the technical solution adopted by this invention is as follows: the molecular formula of this non-Hoffmann coordination polymer with good removal ability for mercury ions is divided into C... 15 H 10 FeHgN6S6, with the general chemical formula: {Fe[Hg(SCN)4](L)} n (L represents bis(4-pyridinthio)methane).

[0005] The crystal structure of the complex is as follows: the complex belongs to the monoclinic crystal system, space group P21 / c, and the cell parameters are a = 7.62455(19) Å, b = 16.6928(4) Å, c = 17.5832(4) Å, α = 90°, β = 95.633(2)°, γ = 90°.

[0006] The preparation method of the complex is as follows: S1. Material preparation was carried out at room temperature and pressure. 3 mL of an aqueous solution of K2[Hg(SCN)4] (51.1 mg, 0.1 mmol) was added to the middle arm of a three-arm H-type tube; S2. Add 3 mL of a methanol solution of ligand L [L represents bis(4-pyridinylthio)methane] (23.4 mg, 0.1 mmol) to the right arm of the three-armed H-tube; S3. Add 3 mL of a methanol solution of FeCl2 (12.6 mg, 0.1 mmol) to the left arm of the three-arm H-type tube; S4. Fill each arm of the three-arm H-tube and the transverse connecting tube with methanol to seal them. Seal the opening of the three-arm H-tube with sealing film and place it in a dark and quiet place. After about two weeks, yellow maple leaf-shaped crystals will precipitate in the transverse connecting tube. S5. Separate the obtained crystals, wash them successively with methanol and diethyl ether, and then air dry them naturally to obtain the finished crystal product.

[0007] The steps for testing the adsorption performance of mercury ions are as follows: S1. Weigh out HgCl2 reagents of different concentration gradients in sequence, and dilute them to 1 L volumetric flasks to prepare HgCl2 test solutions of 50 ppm, 100 ppm, 600 ppm, 1300 ppm, 2200 ppm, 3000 ppm, 8500 ppm, and 12000 ppm. S2. Taking the 100 ppm adsorption test as an example, 5.0 mg of dried crystals was quantitatively weighed and placed in a glass bottle. 10 mL of a 100 ppm HgCl2 solution was accurately transferred using a pipette. After adding a magnetic stir bar, the bottle was placed in a magnetic stirrer for an 8-hour adsorption test. To improve adsorption efficiency, the crystals can be ground beforehand to increase the adsorption surface area, and ultrasonic vibration can be performed before placing the bottle in the magnetic stirrer to increase the dispersion of the crystals in the solution. S3. After centrifuging the adsorbed solution, collect the supernatant and perform inductively coupled atomic emission spectrometry on the collected solution to quantitatively analyze the mercury ion content in the adsorbed solution.

[0008] The advantages of this invention are: the complex possesses a unique two-dimensional non-Hoffmannian spatial structure, thus providing ample adsorption space during the adsorption process. Because the bridging ligand contains sulfur, the strong bond between sulfur and mercury acts as the driving force for adsorption, resulting in excellent mercury removal capabilities. Under test conditions with HgCl2 concentrations ranging from 50 to 12000 ppm, the adsorption rate of the complex for mercury ions remained stable at 39% ± 2%. When the HgCl2 concentration reached 12000 ppm, the adsorption capacity of each milligram of the complex for mercury ions reached 7.40 mg, maintaining a good lattice structure before and after adsorption. This invention has potential application value in green chemical engineering, clean chemical process production, and related materials research. Attached Figure Description

[0009] Figure 1 Perspective view of the complex along axis a. Figure 2 Images of the crystal sample before and after the adsorption test. Figure 3 Three-arm H-type tube crystal growth diagram Figure 4 Crystallographic structure parameter diagram. Detailed Implementation

[0010] To make the objectives and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0011] This invention provides a two-dimensional non-Hoffmann coordination polymer that exhibits good performance in the adsorption of mercury ions. The molecular formula of the material is C2. 15 H 10 FeHgN6S6, chemical formula: {Fe[Hg(SCN)4](L)} x} n(L represents bis(4-pyridinylthio)methane).

[0012] The crystal structure of the magnetic material is as follows: the complex belongs to the monoclinic crystal system, space group P21 / c, and the cell parameters are a=7.62455(19) Å, b=16.6928(4) Å, c=17.5832(4) Å, α=90°, β=95.633(2)°, γ=90°.

[0013] The non-Hoffmannian coordination polymer with mercury ion adsorption properties and its synthesis steps are as follows: S1. Material preparation was carried out at room temperature and pressure. 3 mL of an aqueous solution of K2[Hg(SCN)4] (51.1 mg, 0.1 mmol) was added to the middle arm of a three-arm H-type tube; S2. Add 3 mL of a methanol solution of ligand L [L represents bis(4-pyridinylthio)methane] (23.4 mg, 0.1 mmol) to the right arm of the three-armed H-tube; S3. Add 3 mL of a methanol solution of FeCl2 (12.6 mg, 0.1 mmol) to the left arm of a three-armed H-tube; S4. Fill each arm of the three-arm H-tube and the transverse connecting tube with methanol to seal them. Seal the opening of the three-arm H-tube with sealing film and place it in a dark and quiet place. After about two weeks, yellow maple leaf-shaped crystals will precipitate in the transverse connecting tube. S5. Separate the obtained crystals, wash them successively with methanol and diethyl ether, and then air dry them naturally to obtain the finished crystal product.

[0014] The steps for testing the adsorption performance of mercury ions are as follows: S1. Weigh out HgCl2 reagents of different concentration gradients in sequence, and dilute them to 1 L volumetric flasks to prepare HgCl2 test solutions of 50 ppm, 100 ppm, 600 ppm, 1300 ppm, 2200 ppm, 3000 ppm, 8500 ppm, and 12000 ppm. S2. Taking the 100 ppm adsorption test as an example, 5.0 mg of dried crystals was quantitatively weighed and placed in a glass bottle. 10 mL of a 100 ppm HgCl2 solution was accurately transferred using a pipette. After adding a magnetic stir bar, the bottle was placed in a magnetic stirrer for an 8-hour adsorption test. To improve adsorption efficiency, the crystals can be ground beforehand to increase the adsorption surface area, and ultrasonic vibration can be performed before placing the bottle in the magnetic stirrer to increase the dispersion of the crystals in the solution. S3. After centrifuging the adsorbed solution, collect the supernatant and perform inductively coupled atomic emission spectrometry on the collected solution to quantitatively analyze the mercury ion content in the adsorbed solution.

[0015] The prepared material was characterized using X-ray single-crystal diffraction. The crystallographic parameters of the material are shown in the appendix. Figure 4 .

Claims

1. A two-dimensional non-Hoffmann coordination polymer based on K2[Hg(SCN)4] and flexible bidentate thiopyridine ligands, wherein the elemental composition of the coordination polymer is C 15 H 10 FeHgN6S6, with the general chemical formula: {Fe[Hg(SCN)4](L)} n L represents bis(4-pyridinylthio)methane. The crystal structure of the coordination polymer is: monoclinic, space group P21 / c, with cell parameters a = 7.62455(19) Å, b = 16.6928(4) Å, c = 17.5832(4) Å, α = 90°, β = 95.633(2)°, γ = 90°.

2. A method for synthesizing the coordination polymer according to claim 1, characterized in that, Includes the following steps: S1. Material preparation was carried out at room temperature and pressure. 3 mL of an aqueous solution of 51.1 mg and 0.1 mmol K2[Hg(SCN)4] was added to the middle arm of a three-arm H-type tube. S2. Add 3 mL of a methanol solution containing 23.4 mg of 0.1 mmol ligand L to the right arm of a three-armed H-tube; S3. Add 3 mL of a methanol solution containing 12.6 mg of 0.1 mmol FeCl2 to the left arm of a three-armed H-tube; S4. Fill each arm of the three-arm H-type tube and the transverse connecting tube with methanol to seal the liquid seal. Seal the opening of the three-arm H-type tube with sealing film and place it in a dark and quiet place. After about two weeks, yellow maple leaf-shaped crystals will precipitate in the transverse connecting tube. S5. Separate the obtained crystals, wash them successively with methanol and diethyl ether, and then air dry them naturally to obtain the finished crystal product.

3. The application of the coordination polymer according to claim 1 in the mercury ion adsorption performance test, characterized in that, The testing steps are as follows: S1. Weigh out HgCl2 reagents of different concentration gradients in sequence, and dilute them to 1 L volumetric flasks to prepare HgCl2 test solutions of 50 ppm, 100 ppm, 600 ppm, 1300 ppm, 2200 ppm, 3000 ppm, 8500 ppm, and 12000 ppm. S2. Taking the 100 ppm adsorption test as an example, 5.0 mg of dried crystals were quantitatively weighed and placed in a glass bottle. 10 mL of 100 ppm HgCl2 solution was accurately transferred using a pipette. After adding a magnetic stir bar, the solution was placed in a magnetic stirrer for an 8-hour adsorption test. To improve the adsorption efficiency, the crystals were ground beforehand to increase the adsorption specific surface area, and ultrasonic vibration was performed in the magnetic stirrer to increase the dispersion of the crystals in the solution. S3. After centrifuging the adsorbed solution, collect the supernatant and perform inductively coupled atomic emission spectrometry on the collected solution to quantitatively analyze the mercury ion content in the adsorbed solution.

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