A three-dimensional coordination polymer molecular material with high adsorption performance for mercury ions

Abstract

A three-dimensional non-Hofmann type coordination polymer molecular material is constructed by taking divalent iron, potassium tetrathicyanate and bidentate pyridine sulfide ligand as modules, and a neutral three-dimensional grid is constructed by taking {Fe[Hg(SCN)4](L)2} n (L represents 4,4'-dipyridyl disulfide) as a unit. The preparation method is that the aqueous solution of potassium tetrathicyanate, the ligand L and the methanol solution of ferrous chloride are placed in a double-arm H-shaped tube, sealed and placed, and yellow block crystals are obtained after about two weeks. The advantages of the present application are that the non-Hofmann type space configuration of the complex and the bridged ligand modified by the sulfur element make it show good mercury ion adsorption performance. In a series of adsorption tests of mercury chloride solution with a concentration gradient, it is found that when the concentration of mercury ion reaches 8500 ppm, the adsorption amount of mercury ion per milligram of complex is as high as 4.16 mg. Therefore, the molecular material has extremely high potential application value in cleaning chemical production, sewage treatment and the like.

Description

Technical Field

[0001] This invention belongs to the field of synthesis technology of coordination polymers with high adsorption performance, specifically involving the preparation and adsorption performance study of a three-dimensional non-Hoffmann coordination polymer molecular material constructed using divalent iron, potassium tetrathiocyanomerate and bidentate pyridine sulfide ligands as modules. Background Technology

[0002] Various activities, such as battery and electronic device production, smelting, fossil fuel combustion, and mining, generate large amounts of industrial wastewater containing toxic heavy metal ions. Improper treatment and discharge of this wastewater can pose potential health risks to humans. It is estimated that millions of people in both developed and developing countries are affected by mercury pollution (Lubick N, Malakoff D. Science, 2013, 1443-1445). Mercury in industrial wastewater exists primarily as the inorganic ion form Hg(II) and in organic forms (methylmercury or ethylmercury) (Mondal, S., Chatterjee, S., Mondal, S., and Bhaumik, A. Asc Sustain Chem Eng, 2019, 7(7), 7353-7361). Mercury pollution has attracted global attention, especially in Asia, where anthropogenic activities related to mercury pollution are of paramount concern. Therefore, finding effective methods to remove mercury ions from water is crucial.

[0003] For decades, various technologies, such as coagulation, membrane filtration, flocculation, precipitation, ion exchange, and adsorption, have been developed for removing mercury ions from water. In comparison, adsorption is inexpensive and easy to operate, and is currently considered one of the most promising technologies for mercury ion removal. Various types of adsorbents exist, such as activated carbon, zeolite, clay, and functionalized materials, such as multilayer magnetic nanoparticles, layered double hydroxides, and coordination polymers. Among these, coordination polymers, as a novel type of multifunctional porous material, are highly malleable porous platforms with many advantages over traditional adsorbents such as activated carbon and zeolite, stemming from their versatility in synthesis and structural design. Furthermore, non-Hoffmann coordination polymers, due to their large surface area, tunable porosity, and good stability, show great potential for metal ion adsorption. The preparation method mentioned in this invention is simple, featuring a streamlined process and low production cost. The coordination polymer exhibits good selective adsorption capacity for mercury ions, is less affected by acidity or alkalinity, and possesses good chemical stability. Therefore, this molecular material has extremely high potential application value in clean chemical production, wastewater treatment, and other fields. Summary of the Invention

[0004] This invention provides a three-dimensional non-Hoffmann coordination polymer molecular material with high adsorption performance for mercury ions.

[0005] This three-dimensional non-Hoffmann coordination polymer, which exhibits good adsorption capacity for mercury ions, has the molecular formula C2. 14 H8FeHgN6S6, with the general chemical formula {Fe[Hg(SCN)4](L)2} n (L represents 4,4'-bipyridine disulfide).

[0006] The crystal structure of the complex is as follows: the complex belongs to the monoclinic crystal system, is located in the space group P21 / n, and has the following cell parameters: a = 10.4117(4) Å, b = 12.3240(5) Å, c = 17.7514(7) Å, α = 90°, β = 101.572(4)°, γ = 90°.

[0007] The preparation method of the complex is as follows: S1. All reactions were 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 left arm of a bi-arm H-tube; S2. Add 3 mL of methanol solution of ligand L [L represents (4,4'-bipyridine disulfide)] (22.0 mg, 0.1 mmol) and FeCl2 (12.6 mg, 0.1 mmol) to the right arm of the biarm H-tube; S3. Seal the two arms of the double-armed H-type tube and the transverse connecting tube with methanol. After sealing, place it in a dark and quiet place. After about two weeks, yellow blocky crystals will precipitate in the transverse connecting tube. S4. Separate the obtained crystals, wash them successively with methanol and diethyl ether, and then air dry them naturally to obtain the finished crystal product.

[0008] The steps for testing the adsorption performance of the complex for mercury ions are as follows: S1. Weigh 50 mg, 100 mg, 600 mg, 1200 mg, 2000 mg, and 8500 mg of HgCl2 reagent respectively, and dilute them to 1 L in volumetric flasks to prepare six HgCl2 test solutions with concentration gradients of 50-8500 ppm. S2. Taking the 50 ppm mercury ion adsorption test as an example, weigh 5.0 mg of dried crystals and place them in a container. Accurately transfer 10 mL of a 50 ppm HgCl2 solution using a pipette, place it in a magnetic stirrer, add a rotor, and conduct an adsorption test for 12 hours. To improve the adsorption efficiency, the crystals can be ground and then ultrasonically vibrated to increase the adsorption specific surface area and dispersion. S3. After centrifugation, the supernatant of the adsorbed mercury ion solution is collected. The collected solution is then subjected to inductively coupled atomic emission testing and quantitative analysis of the mercury ion content.

[0009] The advantages of this invention are: the prepared three-dimensional coordination polymer possesses a unique non-Hoffmannian spatial configuration and contains sulfur-modified bridging ligands, resulting in excellent mercury ion adsorption performance. Adsorption tests were conducted in mercuric chloride solutions of varying concentrations, revealing that when the mercuric chloride concentration reached 8500 ppm, the adsorption capacity of each milligram of the complex for mercury ions was as high as 4.16 mg. Therefore, this molecular material has extremely high potential application value in clean chemical production and wastewater treatment. Attached image description: Figure 1 Images of crystal samples before and after adsorption testing Figure 2 : Crystal growth diagram of a two-arm H-type tube Figure 3 Crystallographic structure parameters of the material. 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 method for synthesizing a non-Hoffmannian coordination polymer exhibiting a three-dimensional structure and good mercury ion adsorption properties. The molecular formula of the material is C2. 14 H8FeHgN6S6, chemical formula: {Fe[Hg(SCN)4](L)} x}2 (L represents 4,4'-bipyridine disulfide).

[0012] The crystal structure of the molecular material is as follows: the complex belongs to the monoclinic crystal system, is located in space group P21 / n, and has unit cell parameters a = 10.4117(4) Å, b = 12.3240(5) Å, c = 17.7514(7) Å, α = 90°, β = 101.572(4)°, and γ = 90°.

[0013] The three-dimensional non-Hoffmann coordination polymer and its synthesis steps are as follows: S1. All reactions were 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 left arm of a bi-arm H-tube; S2. Add 3 mL of methanol solution of ligand L [L represents (4,4'-bipyridine disulfide)] (22.0 mg, 0.1 mmol) and FeCl2 (12.6 mg, 0.1 mmol) to the right arm of the biarm H-tube; S3. Seal the two arms of the double-armed H-type tube and the transverse connecting tube with methanol. After sealing, place it in a dark and quiet place for crystal growth. About two weeks later, yellow blocky crystals precipitate in the transverse connecting tube. S4. 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 the complex for mercury ions are as follows: S1. Weigh out 50 mg, 100 mg, 600 mg, 1200 mg, 2000 mg, and 8500 mg of HgCl2 reagent respectively, and dilute to 1 L in volumetric flasks to prepare six HgCl2 test solutions with concentration gradients of 50-8500 ppm; S2. Taking the 50 ppm mercury ion adsorption test as an example, weigh 5.0 mg of dry crystals and place them in a container. Use a pipette to accurately transfer 10 mL of 50 ppm HgCl2 solution and place it in a magnetic stirrer with a rotor for 12 hours of adsorption test. To improve the adsorption efficiency, the crystals can be ground and then subjected to ultrasonic vibration to increase the adsorption specific surface area and dispersion. S3. After centrifugation, the supernatant of the adsorbed mercury ion solution was collected. The collected solution was subjected to inductively coupled atomic emission spectrometry (ICP-AES) for quantitative analysis of the mercury ion content. The prepared material was characterized using X-ray single-crystal diffraction. The crystallographic parameters of the obtained material are shown in the appendix. Figure 3 .

Claims

1. A three-dimensional non-Hoffmann coordination polymer material, characterized in that... The material is constructed using divalent iron, potassium tetrathiocyanate, and bidentate pyridine sulfide ligands as modules, and the general chemical formula of the coordination polymer material is: {Fe[Hg(SCN)4](L)2} n , where L represents 4,4'-bipyridine disulfide, and the crystal structure of the coordination polymer material is as follows: the crystal belongs to the monoclinic crystal system, the space group is P21 / n, and the cell parameters are a = 10.4117(4) Å, b = 12.3240(5) Å, c = 17.7514(7) Å, α = 90°, β = 101.572(4)°, γ = 90°.

2. A method for preparing the three-dimensional non-Hoffmann coordination polymer material according to claim 1, characterized in that, Its synthesis steps: S1. All reactions were carried out at room temperature and pressure. 3 mL of 51.1 mg, 0.1 mmol K2[Hg(SCN)4] solution was added to the left arm of the bi-arm H-tube. S2. Add 22.0 mg, 0.1 mmol of ligand L and 3 mL of 12.6 mg, 0.1 mmol of FeCl2 methanol solution to the right arm of the two-arm H-type tube; S3. Seal the two arms of the double-armed H-type tube and the transverse connecting tube with methanol. After sealing, place it in a dark and quiet place. After two weeks, yellow blocky crystals will precipitate in the transverse connecting tube. S4. Separate the obtained crystals, wash them successively with methanol and diethyl ether, and then air dry them naturally to obtain the finished crystal product.

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