Preparation and application of hollow co s2 nanospheres induced by polyoxometalates

Abstract

The present application relates to a hollow CoS2 nanosphere prepared by a polyacid and its application. The present application aims to solve the problem of difficulty in synthesizing pure phase cobalt sulfide by using the prior art, and provides a method for preparing a hollow CoS2 nanosphere by using a polyacid-based cobalt metal organic framework constructed by silicotungstate as a template and its photocatalytic application. The polyacid-induced hollow CoS2 nanosphere is prepared by the following steps: adding silicotungstate, cobalt acetate and 3,5-bis(triazole-1-yl)pyridine into distilled water and stirring until uniform, adjusting the pH value, and reacting at 160 DEG C for 8 h to prepare a polyacid-based cobalt metal organic framework material template, then adding the polyacid-based cobalt metal organic framework material and thiourea into distilled water and stirring until uniform, then transferring the reaction solution into a polytetrafluoroethylene reactor, and reacting at 200 DEG C for 24 h, and then washing the reaction solution after the temperature of the reaction solution is reduced to room temperature to obtain a black powder, i.e. the polyacid-induced hollow CoS2 nanosphere. The present application can obtain a polyacid-induced hollow CoS2 nanosphere material with colorimetric detection performance.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method and application of a hollow CoS2 nanosphere induced by a polyacid. BACKGROUND

[0002] Phenolic substances seriously affect the growth of animals and plants and the health of human beings due to their high stability, great toxicity and poor biodegradability at low concentrations. Common methods for detecting and degrading phenolic pollutants mainly include chromatography, electrochemical analysis, chemiluminescence, adsorption and chemical oxidation. Although these methods have high sensitivity and repeatability, they are time-consuming, high in cost, complex in operation and even produce secondary pollutants, which limits their wide application. Colorimetric detection shows unique advantages in the detection of common phenolic pollutants. When hydroquinone (HQ) is added to a catalyst-3,3',5,5'-tetramethylbenzidine (TMB)-H2O2 system, the oxidized TMB (oxTMB) can be reduced to 3,3',5,5'-tetramethylbenzidine (TMB), resulting in color fading. Therefore, the content of phenols can be determined by monitoring 3,3',5,5'-tetramethylbenzidine (TMB) through a simple colorimetric analysis.

[0003] Metal-organic frameworks (MOFs) are crystalline porous materials formed by connecting organic ligands and metal ions or metal clusters through coordination bonds. Due to its low cost, variable composition and flexible structure, it is considered to be a promising precursor. Polyoxometalates (POMs) are Bronsted acids that can etch MOFs to form open voids and expose internal surfaces, and are used as precursors together with surfactants to prepare materials with hollow morphology. Polyoxometalate-based metal-organic frameworks (POMOFs) are constructed by introducing polyoxometalates as guest molecules into the host of metal-organic frameworks. They not only retain the excellent physical and chemical properties of polyoxometalates themselves, but also provide a platform for the good dispersion of polyoxometalates and improve the exposure of active sites. As a precursor, polyoxometalate-based metal-organic frameworks (POMOFs) have uniformly distributed polyoxometalates, organic ligands and other transition metal centers, and have good prospects for preparing multi-component metal carbides and metal sulfides with heterogeneous structure interfaces. SUMMARY

[0004] The application aims to solve the problem of difficulty in synthesizing pure-phase cobalt-based sulfides by using the prior art, and provides a method for preparing a hollow CoS2 nanosphere by using a polyoxometalate-based cobalt metal-organic framework constructed from silicotungstate as a template and photocatalytic application.

[0005] To solve the above technical problems, the application is realized by the following technical scheme:

[0006] I. Preparation of a reaction solution with a pH value of 2.5: silicotungstic acid, cobalt acetate and 3,5-bis(triazole-1-yl)pyridine are added to distilled water and stirred until uniform, and then the pH value of the suspension is adjusted to 2.5 to obtain a reaction solution with a pH value of 2.5;

[0007] II. Preparation of a silicotungstate-constructed polyacid-based cobalt metal organic framework material: the reaction solution prepared in step I is transferred to a polytetrafluoroethylene reaction kettle, and then reacted at a temperature of 160 DEG C for 8 h, and after the reaction solution is cooled to room temperature, it is washed to obtain pink block crystals, i.e. a silicotungstate-constructed polyacid-based cobalt metal organic framework material with a double interpenetrating structure, and the chemical formula of the polymer is [Co2(btap)4(H2O)4][SiW 12 O 40 ], wherein btap is 3,5-bis(triazole-1-yl)pyridine; the crystal appears in the form of pink blocks; the crystal system is an orthorhombic system; the space group is Pbca; and the unit cell parameters are α = 90 DEG, β = 90 DEG, γ = 90 DEG,

[0008] III. Preparation of a polyacid-induced hollow CoS2 nanosphere: the silicotungstate-constructed polyacid-based cobalt metal organic framework material template prepared in step II and thiourea are added to distilled water and stirred until uniform, and then the reaction solution is transferred to a polytetrafluoroethylene reaction kettle, and then reacted at a temperature of 200 DEG C for 24 h, and after the reaction solution is cooled to room temperature, it is washed to obtain black powder, i.e. a polyacid-induced hollow CoS2 nanosphere, and the chemical formula of the nanosphere is CoS2, which appears in the form of black powder, and has characteristic peaks at 27.7 DEG, 32.1 DEG, 36.1 DEG, 39.7 DEG and 54.8 DEG, corresponding to (111), (200), (210), (220) and (311) crystal faces of CoS2 respectively;

[0009] IV. The polyacid-induced hollow CoS2 nanosphere can catalyze the discoloration reaction of oxTMB and hydroquinone, and has excellent catalytic performance as a colorimetric detection catalyst.

[0010] Compared with the prior art, the present application has the following beneficial effects:

[0011] I. The present application first uses 3,5-bis(triazole-1-yl)pyridine organic ligand to successfully prepare a silicotungstate-constructed polyacid-based cobalt metal organic framework precursor template through one-step hydrothermal synthesis together with cobalt acetate and silicotungstic acid. Single crystal X-ray diffraction results show that the three-dimensional porous double interpenetrating polyacid-based cobalt metal organic framework precursor prepared in the present application has a three-dimensional interpenetrating structure with pores formed by the mutual connection of metals and organic ligands, and polyacid as a guest molecule is inserted into the framework structure. This unique structure is stable, can be reused and maintains catalytic activity.

[0012] Secondly, the present application first successfully prepares pure-phase cobalt-based metal sulfide by one-step hydrothermal method using polyoxometalate metal-organic framework material and thiourea. X-ray powder diffraction results show that the polyacid-based cobalt metal-organic framework material template prepared by the present application has important influence on the formation of pure-phase CoS2, and the addition of silicon tungsten-based polyoxometalate is beneficial to the formation of CoS2.

[0013] Thirdly, in H2O2, TMB and aqueous solution of hydroquinone, the colorimetric detection performance is tested by ultraviolet spectrum, the absorbance value of hydroquinone at 625 nm decreases linearly with the increase of concentration in the range of 1-45 μM. According to the three times signal-to-noise ratio rule, the detection limit of hydroquinone is only 0.42 μM. Compared with other detection methods of HQ, CoS2 has a relatively low detection limit for the detection of hydroquinone. The polyacid-induced hollow CoS2 nanosphere material of the present application has excellent colorimetric detection performance. Through the colorimetric detection of hydroquinone, the cycle stability of the polyacid-induced hollow CoS2 nanosphere mimetic enzyme is evaluated, and after 3 cycles, the catalytic activity of CoS2 can be maintained at more than 90%, and the morphology has no obvious change, which shows that the polyacid-induced hollow CoS2 nanosphere has good cycle stability. CoS2 mimetic enzyme has excellent peroxidase-like activity, and has a stable curve platform in the catalytic reaction. Its catalytic performance mainly benefits from its special structure, forming a unique hollow microspherical morphology composed of half-octahedron, and having an open gap, which is beneficial to the entry of ions and reactants into the microsphere cavity, forming double active surfaces inside and outside the microsphere, providing more active sites for the reaction and improving the activity of the catalytic reaction. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 Figure 1 is a basic structural unit diagram of the polyacid-induced hollow CoS2 nanosphere material of the present application.

[0015] Figure 2 Figure 2 is a schematic diagram of the formation process of the polyacid-induced hollow CoS2 nanosphere material of the present application.

[0016] Figure 3 Figure 3 is an infrared spectrum diagram of the polyacid-induced hollow CoS2 nanosphere material of the present application.

[0017] Figure 4 Figure 4 is a powder X-ray diffraction diagram of the polyacid-induced hollow CoS2 nanosphere material of the present application.

[0018] Figure 5 Figure 5 is an ultraviolet spectrum diagram of the polyacid-induced hollow CoS2 nanosphere material of the present application in H2O2, TMB and hydroquinone solution. DETAILED DESCRIPTION

[0019] The technical scheme of the present application is not limited to the following specific embodiments, which are only used to illustrate the present application and are not limited to the technical scheme described in the embodiments. Those skilled in the art should understand that the present application can still be modified or replaced equivalently to achieve the same technical effect. As long as the use needs are met, it is within the protection scope of the present application.

[0020] Specific embodiment one: the preparation method of the polyacid-induced hollow CoS2 nanosphere material in the present embodiment is completed according to the following steps:

[0021] I. Preparation of a reaction solution with a pH value of 2.5: 0.15 g of silicotungstic acid, 0.16 g of cobalt acetate, and 0.04 g of 3,5-bis(triazole-1-yl)pyridine were added to distilled water and stirred until uniform, and then the pH value of the suspension was adjusted to 2.5 to obtain a reaction solution with a pH value of 2.5;

[0022] II. Preparation of a silicotungstate-constructed polyacid-based cobalt metal organic framework precursor: the reaction solution prepared in step I was transferred to a polytetrafluoroethylene reaction kettle, and then reacted at a temperature of 160°C for 8 h. After the temperature of the reaction solution was reduced to room temperature, it was washed to obtain a pink block crystal, which is a silicotungstic acid-cobalt polymer with a double interpenetrating metal organic framework, and the chemical formula of the polymer is [Co2(btap)4(H2O)4][SiW 12 O 40 ], wherein btap is 3,5-bis(triazole-1-yl)pyridine; the crystal appears as a pink block; the crystal system is an orthorhombic system; the space group is Pbca; the unit cell parameters are b=20.7638(16), α=90°, β=90°, γ=90°,

[0023] III. Preparation of a polyacid-induced hollow CoS2 nanosphere: 0.05 g of the silicotungstate-constructed polyacid-based cobalt metal organic framework precursor prepared in step II and 0.1 g of thiourea were added to distilled water and stirred until uniform, and then the reaction solution was transferred to a polytetrafluoroethylene reaction kettle, and then reacted at a temperature of 200°C for 24 h. After the temperature of the reaction solution was reduced to room temperature, it was washed to obtain a black powder, which is a polyacid-induced hollow CoS2 nanosphere, and the chemical formula of the nanosphere is CoS2, which appears as a black powder, and has characteristic peaks at 27.7°, 32.1°, 36.1°, 39.7°, and 54.8°, corresponding to the (111), (200), (210), (220), and (311) crystal planes of CoS2, respectively;

[0024] Four, the colorimetric detection performance of a hollow CoS2 nanosphere material induced by a polyacid: add TMB, hydroquinone, H2O2 and a hollow CoS2 nanosphere material induced by a polyacid in a centrifuge tube. The volume of the mixed solution is set to 2 mL, and after reaction at room temperature for 30 min, the absorbance of the reaction solution at 652 nm is recorded by a UV-visible spectrophotometer.

[0025] Specific embodiment two: the preparation method of a silicotungstate-constructed polyacid-based cobalt metal-organic framework precursor according to step one of the specific embodiment, and the molar ratio of 3,5-bis(triazole-1-yl)pyridine, cobalt acetate and silicotungstic acid is 1:(3.2-3.5):(0.26-0.5).

[0026] Specific embodiment three: the difference between this embodiment and specific embodiment one is that the metal cobalt salt in step one is cobalt chloride, cobalt nitrate or cobalt sulfate. The other steps are the same as specific embodiments one to two.

[0027] Specific embodiment four: the preparation method of a silicotungstate-constructed polyacid-based cobalt metal-organic framework precursor according to step one of the specific embodiment, and the molar number of silicotungstic acid to the volume of distilled water is 0.62 mmol: 15 mL.

[0028] Specific embodiment five: the difference between this embodiment and specific embodiment one is that in step one, the pH value of the reaction solution is adjusted to 2.5-3.0 by using HCl solution and NaOH solution with a molar concentration of 1 mol / L. The other steps are the same as specific embodiments one to four.

[0029] Specific embodiment six: the difference between this embodiment and specific embodiment one is that the reaction temperature in step two is 120-160°C, and the time is 0.5-48 h. The other steps are the same as specific embodiments one to five.

[0030] Specific embodiment seven: the difference between this embodiment and specific embodiment one is that the reaction time in step three is 4-36 h. The other steps are the same as specific embodiments one to six.

[0031] The following examples are used to verify the beneficial effects of the present application:

[0032] Example one: the preparation method of a hollow CoS2 nanosphere material induced by a polyacid, which is realized according to the following steps:

[0033] One, preparation of the reaction solution with pH value of 2.5: 0.05 mmol of silicotungstic acid, 0.62 mmol of cobalt acetate and 0.19 mmol of 3,5-bis(triazole-1-yl)pyridine were uniformly dispersed in 15 mL of distilled water, then the pH value of the reaction solution was adjusted to 2.5 using 1 mol / L HCl solution and 1 mol / L NaOH solution, to obtain the reaction solution with pH value of 2.5.

[0034] Two, the above prepared reaction solution with pH value of 2.5 was transferred to a 25 mL polytetrafluoroethylene reactor, and then reacted at a temperature of 160°C for 8 h. After the reaction solution was cooled to room temperature, it was washed to obtain a pink block crystal, which was a hollow CoS2 nanosphere material induced by a polyacid.

[0035] Three, 0.05 g of the silicotungstate-structured polyacid-based cobalt metal organic framework precursor prepared in step two and 0.1 g of thiourea were added to distilled water and stirred uniformly, then the reaction solution was transferred to a polytetrafluoroethylene reactor, and then reacted at a temperature of 200°C for 24 h. After the reaction solution was cooled to room temperature, it was washed to obtain a black powder, which was a hollow CoS2 nanosphere material induced by a polyacid.

[0036] (I) Structure determination of the hollow CoS2 nanosphere material induced by a polyacid prepared in example one:

[0037] Conclusion ① X-ray powder diffraction parameters:

[0038] The CoS2 crystal form was studied by X-ray powder diffraction, and the characteristic peaks at 27.7°, 32.1°, 36.1°, 39.7° and 54.8° correspond to the (111), (200), (210), (220) and (311) crystal planes of CoS2, respectively.

[0039] Conclusion ② X-ray diffraction structure description: X-ray powder diffraction analysis showed that,

[0040] When the reaction time was 4 h, the sample mainly existed in the form of an octahedron, which was wrapped by the (111) crystal plane of CoS2. The formation of this morphology may be because the (111) crystal plane is the most stable structure thermodynamically, because the surface energy of the (111) surface is relatively low compared to other crystal planes of CoS2. With the increase of the reaction time, the octahedron aggregated to form a sphere at 12 h. When the reaction time was 24 h, the surface of the sample formed a complete half-octahedral morphology. When the reaction time increased to 36 h, the morphology did not change much. At the same time, open gaps appeared on the surface of the sample after 12 h of reaction. Based on the above results, we speculate on the formation process of the CoS2 morphology. First, thiourea decomposes rapidly at high temperature, and the decomposition product S 2- Co of Co-POM 2+Ion coordination. In the reaction, Co ions re-nucleate to form precursor octahedral CoS2. This reaction occurs through the inward diffusion of S ions and the outward diffusion of Co ions. As the diffusion proceeds, Co ions form new nuclei on the surface of the precursor octahedral and grow into new octahedra. As the reaction time increases, the rate of outward diffusion of smaller Co ions increases, forming a gap between the newly formed octahedra and the precursor octahedra. When the gap expands to a certain extent, a hollowing process occurs in the center of the precursor octahedra. At the same time, as the reaction time increases, structures with large pores appear, which may be due to etching by the polyacid. This is because different faces of the particles can have different defect densities and surface energies. Through etching, unstable faces can be preferentially eliminated, resulting in an open structure. Based on the above analysis, the Ostwald ripening mechanism is considered to be the main mechanism for the formation of hollow spheres.

[0041] Figure 1 Figure for Example - Basic structural unit of a hollow CoS2 nanosphere material induced by a polyacid.

[0042] Figure 2 Figure for Example - Schematic diagram of the formation process of a hollow CoS2 nanosphere material induced by a polyacid

[0043] (II) Infrared spectroscopy was performed on the polyacid-based metal-organic framework precursor [Co2(btap)4(H2O)4] [SiW 12 O 40 ] of the polyacid-induced hollow CoS2 nanosphere material prepared in Example One, and the infrared spectrum of the silicotungstic acid metal-organic supramolecular polymer was obtained, as shown in Figure 3 The infrared spectrum indicates that the material contains both silicotungstic acid characteristic peaks and organic ligand characteristic peaks.

[0044] Figure 3 Figure for Example - Infrared spectrum of a hollow CoS2 nanosphere material induced by a polyacid.

[0045] (III) Powder X-ray diffraction was performed on the polyacid-induced hollow CoS2 nanosphere material of Example One, and the powder X-ray diffraction spectrum of the polyacid-induced hollow CoS2 nanosphere material was obtained, as shown in Figure 4 The powder X-ray diffraction spectrum shows that the peak positions of the experimental spectrum are consistent with those of the crystal simulation, indicating that the material has high purity.

[0046] Figure 4 Figure for Example - Powder X-ray diffraction spectrum of a hollow CoS2 nanosphere material induced by a polyacid.

[0047] (iv) Colorimetric detection performance test of the polyoxometalate-induced hollow CoS2 nanospheres prepared in Example 1. In the presence of H2O2, the colorimetric detection performance of the polyoxometalate-induced hollow CoS2 nanospheres was studied by catalyzing the color reaction of TMB and hydroquinone. TMB (2 mM), polyoxometalate-induced hollow CoS2 nanospheres (100 μg mL -1 ), hydroquinone (15 mM) and H2O2 (0.1 mM) were added in a centrifuge tube. The volume of the mixed solution was set to 2 mL, and after 30 min of reaction at room temperature, the absorbance of the reaction solution at 652 nm was recorded by a UV-Vis spectrophotometer.

[0048] Figure 5 Figure 8 is a UV spectrum of the polyoxometalate-induced hollow CoS2 nanospheres in H2O2, TMB and hydroquinone solution in Example 1.

[0049] In summary, the polyoxometalate-induced hollow CoS2 nanospheres in Example 1 were successfully prepared by a hydrothermal synthesis method, and were successfully prepared as colorimetric detection materials. The material has a unique hollow microspherical morphology composed of half-octahedrons, and has an open void, forming a double active surface inside and outside the microspheres, which improves the catalytic activity. It is a catalytic material with excellent performance, and at the same time provides a new strategy for polyoxometalate metal-organic framework (POMOFs) derived hollow materials with high activity mimicking peroxidase.

Claims

1. A hollow CoS2 nanosphere induced by polyacids, characterized in that, The product appears as a black powder with a unique hollow microsphere morphology composed of semi-octahedrons and highly open pores. The preparation method of a polyacid-induced hollow CoS2 nanosphere is carried out according to the following steps:

1. Preparation of reaction solution with pH value of 2.5: Add 0.15g silicotungstic acid, 0.16g cobalt acetate and 0.04g 3,5-bis(triazol-1-yl)pyridine to distilled water and stir evenly to obtain a suspension. Then adjust the pH value of the suspension to 2.5 to obtain a reaction solution with pH value of 2.

5. II. Preparation of a polyacid-based cobalt metal-organic framework material constructed from silicotungstenate: The reaction solution prepared in step I was transferred to a polytetrafluoroethylene reactor and reacted at 160°C for 8 hours. After the temperature of the reaction solution dropped to room temperature, it was washed to obtain pink blocky crystals, which is a silicotungstenate-cobalt polymer with a double interpenetrating metal-organic framework. The chemical formula of the polyacid-based cobalt metal-organic framework material constructed from silicotungstenate described in step two is [Co2(btap)4(H2O)4][SiW 12 O 40 [The following appears to be a separate, unrelated section:] where btap is 3,5-bis(triazol-1-yl)pyridine; the crystals appear as pink lumps; the crystal system is orthorhombic; the space group is Pbca; the cell parameters are... α=90°, β=90°, γ=90°, III. Preparation of a hollow CoS2 nanosphere induced by polyacids: 0.05g of the polyacid-based cobalt metal-organic framework material constructed by silicotungstenate prepared in step II and 0.1g of thiourea were added to distilled water and stirred evenly. The reaction solution was then transferred to a polytetrafluoroethylene reactor and reacted at 200℃ for 24h. After the temperature of the reaction solution dropped to room temperature, it was washed to obtain a black powder, which is a hollow CoS2 nanosphere induced by polyacids. The XRD spectrum of the nanospheres has characteristic peaks corresponding to the (111), (200), (210), (220) and (311) crystal planes of CoS2 at diffraction angles of 27.7°, 32.1°, 36.1°, 39.7° and 54.8°, respectively.

2. The hollow CoS2 nanosphere induced by polyacids according to claim 1, characterized in that, The molar ratio of silicotungstic acid to distilled water in step one is 0.62 mmol: 15 mL.

3. The hollow CoS2 nanosphere induced by polyacids according to claim 1, characterized in that, In step one, the pH of the reaction solution is adjusted to 2.5 using a 1 mol / L HCl solution and a 1 mol / L NaOH solution.

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