Preparation method of cobalt-based metal organic framework and application of cobalt-based metal organic framework in degradation of organic dyes by activated monopersulfate

Abstract

The application discloses a preparation method of a cobalt-based metal organic framework and application of the cobalt-based metal organic framework in degrading organic dyes by activating monopersulfate. The cobalt-based metal organic framework material with a chemical formula of [Co2(OH)(PBA)(AIP)]·3H2O·DMA is synthesized by a solvothermal reaction of mixed ligands 4-pyridine-4-yl benzoic acid and 5-amino isophthalic acid in a mixed solvent of N,N-dimethylacetamide and water, and the material has one-dimensional square nanochannels and a three-dimensional network connected by (3,10). The material can be used as an effective heterogeneous catalyst to efficiently degrade organic dye pollutants in wastewater by activating monopersulfate. In addition, the material can be recycled by simple centrifugal separation after the catalytic reaction is completed, so that recycling is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of porous materials, and particularly relates to a preparation method of a cobalt-based metal organic framework and application of the cobalt-based metal organic framework in degrading organic dyes by activating monopersulfate. BACKGROUND

[0002] With the rapid development of modern economy and industry, wastewater pollution has become one of the problems of global concern. Wastewater contains refractory organic pollutants. Among the main organic pollutants, organic dyes have attracted more attention, and are widely used in papermaking, printing, plastics, leather, textiles and other industries. Therefore, it is of great significance to remove organic dye pollutants in wastewater before discharge.

[0003] At present, a variety of methods have been applied to wastewater treatment and purification, including adsorption, sedimentation, membrane technology, photocatalytic degradation, etc. However, these methods all have the disadvantages of high operating cost, low efficiency, incomplete degradation, etc. In recent years, advanced oxidation processes (AOPs) using active oxygen species can efficiently and completely remove refractory organic pollutants, and are considered to be one of the most effective treatment technologies for wastewater treatment. Among AOPs, the advanced oxidation process based on sulfate radicals (SO4 - ·) has gained more and more recognition and is considered to have broad application prospects for efficient removal of organic pollutants in water. Generally, sulfate radicals (SO4 - ·) are generated from one of the most commonly used oxidants, monopersulfate (PMS). So far, some methods have been developed to activate PMS through heat treatment, ultrasonic treatment, ultraviolet (UV) irradiation, microwave irradiation, etc. However, none of the above methods meets the demand for high efficiency. In the past few years, it has been reported that PMS is activated by different transition metal ions (such as Co 2+ , Ni 2+ , Cu 2+ , Fe 2+ ) to generate sulfate radicals for degrading organic pollutants. However, in practical applications, these homogeneous catalyst materials will cause secondary pollution. Therefore, it is urgent to design and develop transition metal heterogeneous catalysts for PMS activation.

[0004] As crystalline porous materials, metal-organic frameworks (MOFs) have attracted widespread attention due to their large specific surface area, highly ordered and unique structure, and tunable porosity. Composed of inorganic metal centers (metal ions or metal clusters) and organic ligand units, MOFs have been widely applied in gas adsorption and separation, molecular sensing, drug delivery, and heterogeneous catalysis. Recently, MOFs have been introduced into aerosol catalysts (AOPs) for wastewater treatment. Several studies have reported on MOF materials as heterogeneous catalysts for activating PMS to produce active SO4. - • Research on the degradation of organic pollutants. Compared with traditional catalysts, MOF materials exhibit superior catalytic performance. Therefore, the rational design of MOF heterogeneous catalysts as potential catalysts for AOPs in wastewater treatment is of great significance. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems and needs in the prior art and to provide a method for preparing a cobalt-based metal-organic framework and its application in the degradation of organic dyes by activated monoperoxyhydrosulfate.

[0006] The chemical formula of the cobalt-based metal-organic framework material in this invention is [Co2(OH)(PBA)(AIP)]·3H2O·DMA, wherein PBA is 4-pyridin-4-ylbenzoate, AIP is 5-aminoisophthalate, and DMA is N,N-dimethylacetamide.

[0007] In one embodiment of the present invention, the cobalt-based metal-organic framework material has a monoclinic crystal system and a space group of P21 / n; the unit cell parameters are... α=90°, β=107.059°, γ=90°.

[0008] Each asymmetric unit cell in a cobalt-based metal-organic framework crystal contains two crystallographically independent Co ions and one deprotonated PBA. - Ligands and AIP 2- Ligands. Co1 adopts a six-coordinate octahedral geometry, interacting with ligands from PBA. - and AIP 2- The ligand has 3 carboxyl oxygens and 2 nitrogens, as well as OH groups. - One oxygen coordination site. Co2 is 5-coordinated with oxygen from PBA. - and AIP 2- The ligand is coordinated with 3 carboxyl oxygens and 2 oxygens from hydroxyl groups; symmetry codes: #1 1-x,1-y,1-z; #2 0.5-x,-0.5+y,0.5-z; #3-0.5+x,0.5-y,0.5+z; #4 0.5+x,0.5-y,0.5+z.

[0009] There is also a Co4O2 secondary building unit in the cobalt-based metal organic framework material, and the Co4O2 secondary building unit is connected by ligands PBA - and AIP 2- to form an infinite three-dimensional framework, and one-dimensional square nanochannels with a size of about 0.8 nm*0.8 nm are observed in the structure along the b-axis direction. From the perspective of topology, each AIP 2- The ligand can be regarded as a 3 connection point, and each Co4O2 secondary building unit can be regarded as a 10 connection point, so that the cobalt-based metal organic framework material can be regarded as a (3, 10) connected three-dimensional topological network.

[0010] The application also provides a preparation method of the cobalt-based metal organic framework material.

[0011] 1) Preparation of a reaction solution: dissolving cobalt nitrate hexahydrate and organic ligands into a mixed solution of N,N-dimethylacetamide and water to obtain a reaction solution; the organic ligands are 4-pyridin-4-yl benzoic acid and 5-amino isophthalic acid; the molar ratio of cobalt nitrate hexahydrate to 4-pyridin-4-yl benzoic acid and 5-amino isophthalic acid is (2-4) : 1: 1; the volume ratio of N,N-dimethylacetamide to water is 1:1; and the amount ratio of 4-pyridin-4-yl benzoic acid to N,N-dimethylacetamide is 1 mmol: (30-40) mL.

[0012] 2) The reaction solution obtained in step 1) is added into a high-pressure reaction kettle, the reaction kettle is heated from room temperature to 100-110 DEG C, and the reaction is carried out for 48-72 h; after the reaction is completed, the reaction kettle is cooled to room temperature, and the purple block crystal is separated by repeatedly washing with N,N-dimethylacetamide, and the purple block crystal is the cobalt-based metal organic framework material.

[0013] In an embodiment of the application, in step 2), the reaction kettle is heated from room temperature to 100-110 DEG C at a rate of 10 DEG C / hour.

[0014] The cobalt-based metal organic framework material provided in the application has the application of degrading organic dyes, and in the application, the cobalt-based metal organic framework material is used as a heterogeneous catalyst for activating monopersulfate (PMS) to degrade organic dye pollutants by advanced oxidation.

[0015] Preferably, the organic dye pollutants are rhodamine B (RhB).

[0016] Compared with the prior art, the application has the following beneficial effects:

[0017] The application adopts a simple solvothermal synthesis technology to design and synthesize a three-dimensional cobalt-based metal organic framework material with a nano-pore channel structure. The material can be used as an effective heterogeneous catalyst to realize efficient degradation of organic dye pollutants in water by activating PMS. In 100 mL of a rhodamine B aqueous solution with a concentration of 50 mg / L, when the cobalt-based metal organic framework (Co-MOF) loading is 10 mg and the PMS dosage is 1.0 mM, the removal rate of the dye rhodamine B reaches 99.8% in 6 minutes. In addition, the material can be recycled by simple centrifugal separation, realizing recycling. Therefore, the material is an efficient heterogeneous catalyst which can activate PMS to realize efficient degradation of organic dye pollutants. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 It is a coordination structure schematic diagram of the cobalt-based metal organic framework Co-MOF of the application.

[0019] Figure 2 It is a structure diagram of the Co-MOF of the application, wherein Figure 2 (a) is a Co4O2 secondary building unit; Figure 2 (b) is a one-dimensional square channel structure schematic diagram; Figure 2 (c) is a three-dimensional packing structure schematic diagram along the b-axis direction; Figure 2 (d) is a (3,10) connection topology structure schematic diagram.

[0020] Figure 3 It is a PXRD spectrum diagram of the Co-MOF simulation and synthesis of the application.

[0021] Figure 4 It is a degradation curve diagram of rhodamine B dye under different conditions (Co-MOF alone, PMS alone and Co-MOF / PMS).

[0022] Figure 5 It is a column chart of the recycling degradation efficiency of Co-MOF activated PMS to degrade RhB.

[0023] Figure 6 It is a curve diagram of the influence of different parameters of the Co-MOF / PMS system on the degradation of rhodamine B dye, wherein Figure 6 (a) is the influence of the catalyst Co-MOF dosage on the degradation of RhB; Figure 6 (b) is the influence of the initial concentration of RhB on the degradation of RhB; Figure 6 (c) is the influence of the PMS dosage on the degradation of RhB; Figure 6 (d) is the influence of the temperature on the degradation of RhB. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings Figures 1-6The specific embodiments of the present application are described in detail, but it should be understood that the scope of protection of the present application is not limited by the specific embodiments. Based on the examples in the present application, all other examples obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application.

[0025] Example 1 Preparation method of cobalt-based metal organic framework material (Co-MOF)

[0026] In this embodiment, a cobalt-based metal organic framework material can be obtained, and the preparation method is completed according to the following steps:

[0027] 1) Preparation of reaction solution: dissolve metal salt cobalt nitrate hexahydrate (0.058 g, 0.2 mmol) and organic ligand 4-pyridin-4-yl benzoic acid (0.020 g, 0.1 mmol) and 5-amino isophthalic acid (0.018 g, 0.1 mmol) into N,N-dimethylacetamide (3 mL) and water (3 mL) to obtain a reaction solution;

[0028] 2) The reaction solution is added to a polytetrafluoroethylene reaction kettle, and then a stainless steel autoclave is placed in an oven, which is heated at a rate of 10°C per hour from room temperature to 100°C, and reacted at a temperature of 100°C for 3 days, and then cooled to room temperature. The purple block crystal obtained by repeatedly washing and separating with N,N-dimethylacetamide is the cobalt-based metal organic framework crystalline material.

[0029] The chemical formula of the cobalt-based metal organic framework material is [Co2(OH)(PBA)(AIP)]·3H2O·DMA, wherein PBA is 4-pyridin-4-yl benzoate, AIP is 5-amino isophthalate, and DMA is N,N-dimethylacetamide; the yield is 83%.

[0030] Example 2 Crystal structure analysis

[0031] 1. Single crystal X-ray diffraction data was recorded using a German Bruker Apex II single crystal diffractometer, and molybdenum target was used for radiation (λ = 0.71069).

[0032] The cobalt-based metal organic framework material [Co2(OH)(PBA)(AIP)]·3H2O·DMA has a monoclinic crystal system and a P21 / n space group; the unit cell parameters are α = 90°, β = 107.059°, γ = 90°.

[0033] The asymmetric unit contains two crystallographically independent Co ions, one deprotonated PBA - ligand and AIP 2- ligand. Co1 adopts a hexacoordinated octahedral geometry, and PBA- and AIP 2- The ligand has 3 carboxyl oxygens and 2 nitrogens, as well as OH groups. - One oxygen coordination site. Co2 is 5-coordinated with oxygen from PBA. - and AIP 2- The ligand has three carboxyl oxygen groups and two oxygen groups from the hydroxyl group coordinated. For example... Figure 1 As shown, symmetry code: #1 1-x,1-y,1-z; #2 0.5-x,-0.5+y,0.5-z; #3 -0.5+x,0.5-y,0.5+z; #4 0.5+x,0.5-y,0.5+z.

[0034] Co-MOF contains Co4O2 secondary building units ( Figure 2 (a)). These Co4O2 secondary building units are connected via ligand PBA. - and AIP 2- The interconnected structures form an infinite three-dimensional framework. One-dimensional square nanopores, approximately [size missing], are observed within the structure along the b-axis. ( Figure 2 (b) and Figure 2 (c)). From a topology perspective, each AIP 2- The ligand can be viewed as a 3-connection point, and each Co4O2 secondary building unit can be viewed as a 10-connection point, thus the Co-MOF can be viewed as a (3,10) connected three-dimensional topological network. Figure 2 d).

[0035] 2. Powder X-ray Diffraction (PXRD)

[0036] At 293K, tests were conducted using the Rigaku model RINT Ultima III diffractometer, with an angle range of 3-50°. For example... Figure 3 As shown, the PXRD spectrum of the synthesized Co-MOF crystal matches well with the simulated spectrum, indicating that the synthesized crystal material has good phase purity.

[0037] Example 3: Catalytic performance of activated PMS for RhB degradation

[0038] The catalytic degradation experiment was performed as follows: The organic dye pollutant selected in this example is Rhodamine B (RhB).

[0039] At room temperature (20°C), 100 mL of a 50 mg / L RhB aqueous solution was prepared and placed in a 250 mL beaker. 10 mg of crystalline Co-MOF sample was added to the prepared RhB aqueous solution and stirred magnetically for 10 min to reach adsorption equilibrium.

[0040] Next, PMS (1.0 mM) was added to the system. The PMS used in this invention is potassium persulfate complex (KHSO5·0.5KHSO4·0.5K2SO4). After reacting for a certain period of time, 1.0 mL samples were taken at intervals. 1.0 mL of methanol was added to the sampled solution to quench the reaction. The solid substances were filtered off to obtain a clear solution.

[0041] The obtained clarified night was subjected to UV-Vis absorption spectroscopy using a Jasco V-770 spectrometer. The characteristic peak of RhB at 554 nm was monitored, and the concentration of RhB was analyzed.

[0042] like Figure 4 As shown, in 100 mL of a 50 mg / L RhB aqueous solution, the addition of only Co-MOF (10 mg) did not change the concentration of RhB dye, indicating that Co-MOF had almost no adsorption effect on RhB dye. Similarly, the addition of only PMS (1.0 mM) also resulted in almost no change in the concentration of RhB dye, indicating that PMS alone is difficult to oxidize and degrade RhB dye. In contrast, under the condition of Co-MOF / PMS co-existence, the concentration of RhB decreased significantly, and the dye color visibly became lighter. After 6 minutes of reaction, the removal rate of RhB dye reached 99.8%. This indicates that Co-MOF can act as an effective catalyst to activate PMS to generate sulfate radicals SO42-. - This leads to the efficient oxidative degradation of dye RhB. The Co-MOF prepared in this invention can serve as a highly efficient heterogeneous catalyst to activate PMS for the rapid degradation and removal of organic dye pollutants.

[0043] In addition, the tested crystal samples were centrifuged, washed repeatedly with DMA, and the recovered samples were reused for the cyclic degradation of RhB dye. Figure 5 A bar graph shows the degradation efficiency of RhB after four cycles of Co-MOF-catalyzed activation of PMS. The dye removal efficiency was determined using the formula (C0-C) / C0×100%, where C0 is the initial concentration of the prepared RhB dye, and C is the concentration of RhB dye corresponding to a certain catalytic degradation time. The dye removal rate did not change significantly after 6 minutes of reaction in four cycles, indicating that the Co-MOF of this invention is recyclable and can be used as a heterogeneous catalyst for the efficient and cyclical degradation of organic dye pollutants.

[0044] Example 4: Effect of different parameters on the catalytic degradation performance of RhB

[0045] The different parameters selected in this embodiment include: the amount of Co-MOF catalyst, the initial concentration of RhB, the amount of PMS, and the reaction temperature.

[0046] 1. Effect of Co-MOF catalyst dosage on degradation performance

[0047] Following the catalytic degradation experiment method in Example 3, without changing other reaction conditions, Co-MOF was used as the catalyst, PMS as the oxidant, a 250 mL beaker was used as the reaction vessel, and 100 mL of RhB aqueous solution with an initial concentration of 50 mg / L was prepared at a temperature of 20 °C. Four treatment groups were set up: the amount of Co-MOF catalyst added was adjusted to 5 mg, 10 mg, 15 mg, and 20 mg, respectively. Figure 6 The curves in (a) from top to bottom represent the effects of activated PMS on the oxidative degradation of RhB when the dosage of Co-MOF is 5 mg, 10 mg, 15 mg, and 20 mg. As the dosage of the catalyst Co-MOF increases, both the dye degradation efficiency and degradation rate improve. More catalyst provides more catalytic active sites, activating PMS to generate more free radicals, thus improving the dye degradation effect. The results indicate that the amount of catalyst added affects the oxidative degradation of organic dye pollutants by activated PMS. Therefore, adjusting the amount of Co-MOF added can regulate the degradation efficiency of pollutants based on the initial concentration of the pollutants and considering cost.

[0048] 2. Effect of RhB concentration on degradation performance

[0049] Following the catalytic degradation experiment method described in Example 3, without changing other reaction conditions, Co-MOF was used as the catalyst, PMS as the oxidant, a 250 mL beaker was used as the reaction vessel, 100 mL of RhB aqueous solution was prepared, and the temperature was 20 °C. Four treatment groups were set up: the initial concentrations of the prepared RhB were adjusted to 10 mg / L, 20 mg / L, 50 mg / L, and 100 mg / L, respectively. Figure 6 The curves in (b), from bottom to top, represent the effects of activated PMS on the degradation of RhB when the initial concentrations are 10 mg / L, 20 mg / L, 50 mg / L, and 100 mg / L. When the initial RhB concentration increases from 50 mg / L to 100 mg / L, both the dye degradation efficiency and degradation rate decrease. When the initial RhB concentration decreases from 50 mg / L to 10 mg / L and 20 mg / L, the dye degradation rate increases, while the degradation efficiency remains relatively unchanged. These results indicate that the initial concentration of organic pollutants affects the oxidation and degradation by activated PMS.

[0050] 3. Effect of PMS dosage on degradation performance

[0051] According to the execution method of the catalytic degradation experiment in Example 3, without changing other reaction conditions, Co-MOF is used as the catalyst, PMS is used as the oxidant, a 250 mL beaker is used as the reaction container, and 100 mL of RhB aqueous solution with an initial concentration of 50 mg / L is prepared. The temperature is 20℃. Four treatment groups are set: the amount of PMS added is adjusted to 0.50 mM, 0.75 mM, 1.00 mM, and 2.00 mM, respectively. Figure 6 The curves in (c) from top to bottom are the effect diagrams of the oxidative degradation of RhB when the amount of PMS is 0.50 mM, 0.75 mM, 1.00 mM, and 2.00 mM, respectively. When the amount of PMS increases from 0.50 mM to 1.00 mM, the dye degradation efficiency and degradation rate both increase, and the degradation efficiency reaches more than 99.8%. When it continues to increase to 2.00 mM, the dye degradation efficiency changes little. The results show that the amount of PMS input has an effect on the oxidative degradation of organic dye pollutants. In practical applications, according to the initial concentration of pollutants and the treatment requirements, the amount of PMS added is adjusted to save costs.

[0052] 4. Effect of temperature on degradation performance

[0053] According to the execution method of the catalytic degradation experiment in Example 3, without changing other reaction conditions, Co-MOF is used as the catalyst, PMS is used as the oxidant, a 250 mL beaker is used as the reaction container, and 100 mL of RhB aqueous solution with an initial concentration of 50 mg / L is prepared. Three treatment groups are set: the reaction temperature is adjusted to 20℃, 30℃, and 40℃, respectively. Figure 6 The curves in (d) from top to bottom are the effect diagrams of the oxidative degradation of RhB by Co-MOF activated PMS when the reaction temperature is 20℃, 30℃, and 40℃, respectively. The higher the reaction temperature, the faster the rate of dye degradation. The results show that the reaction temperature has an effect on the oxidative degradation of organic dye pollutants by Co-MOF activated PMS.

[0054] The above is only a preferred embodiment of the present application, and it should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered within the scope of protection of the present application.

Claims

1. A cobalt-based metal-organic framework material, characterized in that, The chemical formula of the cobalt-based metal-organic framework material is [Co2(OH)(PBA)(AIP)]·3H2O·DMA; wherein PBA is 4-pyridin-4-ylbenzoate, AIP is 5-aminoisophthalate, and DMA is N,N-dimethylacetamide; the cobalt-based metal-organic framework material has a monoclinic crystal system and a space group of [missing information]. P2 1 / n ; unit cell parameters are a = 15.649 (7) Å, b = 12.876 (6) Å, c = 17.677 (8) Å, V = 3405 (3)Å 3 , α = 90°, β = 107.059° γ = 90°; Each asymmetric unit in the cobalt-based metal-organic framework crystal contains two crystallographically independent Co ions and one deprotonated PBA. - Ligands and AIP 2- The ligand, Co1, adopts a six-coordinate octahedral geometry, interacting with ligands from PBA. - and AIP 2- The ligand has 3 carboxyl oxygens and 2 nitrogens, as well as OH groups. - One oxygen coordination site; Co2 is 5-coordinated with PBA. - and AIP 2- The ligand has 3 carboxyl oxygens and 2 oxygens from the hydroxyl group coordinated; symmetry codes: #1 1-x,1-y, 1-z; #2 0.5-x, -0.5+y, 0.5-z; #3 -0.5+x, 0.5-y, 0.5+z; #4 0.5+x, 0.5-y,0.5+z; Co4O2 secondary building units also exist in cobalt-based metal-organic framework materials, which are connected by the ligand PBA. - and AIP 2- Interconnected to form an infinite three-dimensional framework, the structure contains one-dimensional square nanopores with a size of 13.4 Å × 7.3 Å; from a topological perspective, each AIP... 2- The ligand can be viewed as a 3-connection point, and each Co4O2 secondary building unit can be viewed as a 10-connection point, thus the cobalt-based metal-organic framework material can be viewed as a three-dimensional topological network with (3,10) connections.

2. A method for preparing a cobalt-based metal-organic framework material as described in claim 1, characterized in that, The steps of this method are as follows: 1) Preparation of reaction solution: Cobalt nitrate hexahydrate and organic ligands were dissolved in a mixed solution of N,N-dimethylacetamide and water to obtain the reaction solution; the organic ligands were 4-pyridin-4-ylbenzoic acid and 5-aminoisophthalic acid, and the molar ratio of cobalt nitrate hexahydrate to 4-pyridin-4-ylbenzoic acid and 5-aminoisophthalic acid was (2-4):1:1; the volume ratio of N,N-dimethylacetamide to water was 1:1; the molar ratio of 4-pyridin-4-ylbenzoic acid to N,N-dimethylacetamide was 1 mmol:(30-40) mL; 2) Add the reaction solution obtained in step 1) into a high-pressure reactor, heat the reactor from room temperature to 100-110 ℃, and react for 48-72 h. After the reaction is completed, cool it to room temperature and wash it repeatedly with N,N-dimethylacetamide to separate purple blocky crystals, which are the cobalt-based metal-organic framework material.

3. The method for preparing the cobalt-based metal-organic framework material according to claim 2, characterized in that, In step 2), the reactor is heated from room temperature to 100-110 ℃ at a rate of 10 ℃ / hour.

4. The application of the cobalt-based metal-organic framework material as described in claim 1 in the degradation of organic dyes, characterized in that, In this application, cobalt-based metal-organic framework materials are used as heterogeneous catalysts for the advanced oxidation degradation of organic dye pollutants by activating monoperoxyhydrosulfate.

5. The application according to claim 4, characterized in that, The organic dye contaminant is Rhodamine B.

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