CN107930670A - Heterogeneous catalysis material that a kind of self-cradling type is homogeneously changed and its preparation method and application - Google Patents

Abstract

The invention provides a self-supporting homogeneous heterogeneous catalytic material and its preparation method and application. The preparation method comprises: mixing zinc salt, aromatic carboxylic acid and organic solvent to obtain MOF-i; using dimethylimidazole and cobalt nitrate as raw materials and water as solvent to synthesize ZIF-67 nanocrystals; ZIF-67 nanocrystals, Mix MOF‑i with solvent and stir at room temperature for 0.5h‑3h to obtain Zn/Co‑MOF‑i/ZIF‑67; under an inert atmosphere, pyrolyze Zn/Co‑MOF‑i/ZIF‑67 for 1h‑ After 8 hours, a self-supporting homogeneous heterogeneous catalytic material was obtained. The present invention also provides the catalytic material prepared by the above preparation method, the catalytic material of the present invention can be used to degrade organic pollutants in sewage.

Description

A self-supporting homogeneous heterogeneous catalytic material and its preparation method and application

technical field

The invention relates to a catalytic material and a preparation method thereof, in particular to a heterogeneous catalytic material capable of degrading organic pollutants in sewage and a preparation method thereof, belonging to the technical field of catalyst preparation.

Background technique

In recent years, the level of urbanization has been continuously improved, and the demand for chemical products has continued to increase, resulting in an increase in sewage discharge year by year, and the damage caused by organic pollutants to the environment, especially to water resources, has become increasingly serious. Nitro compounds and dyes are the main components of organic pollutants. Therefore, if organic pollutants in agricultural or industrial wastewater can be degraded, it will not only reduce environmental pollution, but also turn waste into treasure, providing raw materials for the production of fine chemicals .

At present, the methods of organic wastewater treatment mainly include biological, physical and chemical methods. Biological and physical methods based on adsorption, membrane separation, aerobic and anaerobic treatment, etc., can reduce the concentration of pollutants in water, but cannot fundamentally eradicate organic pollutants, resulting in environmental damage caused by adsorbed or separated organic pollutants. Secondary hazard. Therefore, only by fundamentally eliminating organic pollutants can we truly protect the environment. The chemical treatment method converts organic pollutants in wastewater into non-toxic and non-polluting substances by using catalytic materials, which can not only greatly improve the efficiency of sewage degradation, but also will not cause secondary pollution, and is expected to achieve sustainable development.

At present, the catalytic materials for sewage degradation mainly include Au, Pd, AuCu, PdCu and other noble metals or doped noble metal catalytic materials. Although these noble metal catalytic materials have high activity, their reserves are limited and the cost is high, making it impossible to achieve large-scale production and application.

In recent years, metal-free nitrogen-doped materials have been used for wastewater degradation. The study found that nitrogen-doped graphene was used for the reduction of 4-nitrophenol, and its activity was comparable to that of noble metal catalysts, which greatly reduced the production cost. However, this kind of nitrogen-doped graphene needs to undergo multi-step reaction preparation, and the effective utilization rate of nitrogen is low; at the same time, the microporous structure of graphene is not conducive to material transfer and transportation, and recycling is also very difficult (Xiang-kai Kong, Zhi -yuan Sun, Min Chen, Chang-le Chen, Qian-wang Chen. Metal-free catalytic reduction of 4-nitrophenol to 4-aminophenol by N-doped graphene, Energy & Environmental Science, 2013, 6:3260-3266).

Although transition metal (oxide) catalytic materials represented by Co are cheap and easy to magnetically recycle, their activity is usually lower than that of noble metal catalytic materials. Reinout Meijboom et al constructed mesoporous Co ₃ O ₄ and used it for the reduction of 4-nitrophenol, its activity is much higher than commercial Co ₃ O ₄ (Batsile M.Mogudi,Phendukani Ncube,ReinoutMeijboom.Catalytic activity of mesoporous cobalt oxides with controlled porosity and crystallite sizes: Evaluation using the reduction of 4-nitrophenol, Applied Catalysis B: Environmental, 2016, 198: 74-82). However, the structural stability _{of Co3O4} catalytic materials in cyclic use is worrying. Currently, one-step pyrolysis of cobalt-containing metal-organic frameworks (such as ZIF-67) as precursors to obtain Co-NCC catalytic materials has been proved to be an effective method. For example, Hocheol Song research group (Zubair Hasan, Dong-Wan Cho, Chul-Min Chon, Kwangsuk Yoon, Hocheol Song. Reduction of p-nitrophenol by magnetic Co-carbon composites derived from metal organic frameworks, Chemical Engineering Journal, 2016,298:183- 190) ZIF-67 metal-organic framework was synthesized by using dimethylimidazole and cobalt nitrate hexahydrate, and a nitrogen-doped cobalt-containing Co-NCC catalytic material was obtained by direct carbonization. Although this method can improve the stability of cobalt-based catalytic materials, the specific surface area of the material is small, the porosity is low, and the structure of the precursor collapses during the pyrolysis process, resulting in uneven morphology of Co-NCC. On the other hand, cobalt oxides were supported on porous (N-doped) carbon supports (Dong-Wan Cho, Kwang-Hwa Jeong, Sohyun Kima, Daniel C.W. Tsangc, Yong Sik Ok, Hocheol Song. Synthesis of cobalt -impregnated carboncomposite derived from a renewable resource: Characterization and catalytic performance evaluation, Science of the Total Environment, 2018, 612:103-110), or encapsulated in porous (N-doped) carbon shells (Xingyue Li, Chunmei Zeng, Jing Jiang and LunhongAi. Magnetic cobalt nanoparticles embedded in hierarchically porous nitrogen-doped carbon frameworks for highly efficient and well-recyclable catalysis, Journal of Materials Chemistry A, 2016, 4: 7476-7482), the obtained cobalt-based catalytic material has a large specific surface area, High porosity, regular shape. However, the former has a large number of exposed active sites and has high activity, but the active components are easy to lose; the latter has high stability, but the embedded active components cannot fully exert its catalytic performance, and usually have low activity.

Therefore, it is still a huge challenge to develop porous cobalt-based catalytic materials with both high activity and high stability for the degradation of organic matter in sewage.

Contents of the invention

In order to solve the above technical problems, the object of the present invention is to provide a porous cobalt-based catalytic material with high activity and high stability that can be used to degrade organic matter in sewage.

In order to achieve the above technical purpose, the invention provides a method for preparing a self-supporting homogeneous heterogeneous catalytic material, the preparation method comprising the following steps:

Mix zinc salt, aromatic carboxylic acid and organic solvent to obtain MOF-i;

ZIF-67 nanocrystals were synthesized with dimethylimidazole and cobalt nitrate as raw materials and water as solvent;

Mix ZIF-67 nanocrystals, MOF-i and solvent at a mass ratio of 0.07-0.1:1:10-30, and stir at room temperature for 0.5h-3h to obtain Zn/Co-MOF-i/ZIF-67;

Under an inert atmosphere, Zn/Co-MOF-i/ZIF-67 is pyrolyzed for 1h-8h to obtain a self-supporting homogeneous heterogeneous catalytic material.

According to a specific embodiment of the present invention, MOF-i and ZIF-67 nanocrystals are prepared by a solvothermal method; Zn/Co-MOF-i/ZIF-67 is obtained by a self-assembly method; finally, a self- Supported homogeneous heterogeneous catalytic materials. The self-supporting homogeneous heterogeneous catalytic material has the same core and shell components, has a unique three-dimensional superstructure, has high specific surface area, abundant pores, and is easy to recycle magnetically.

In the above preparation method, preferably, the solvent used includes one or a combination of water, ethanol and N,N'-dimethylformamide.

In the above preparation method, preferably, the pyrolysis temperature is 550°C-950°C; more preferably, the pyrolysis temperature is 800°C.

In the above preparation method, preferably, the mass ratio of ZIF-67 and MOF-i is 0.09:1.

According to a specific embodiment of the present invention, MOF-i can be prepared by a conventional solvothermal method in the field, including Zn-BTC (zinc trimesic acid) nanofibers, Zn-BTC nanodisks, MOF-5 (zinc-paraphenylene Zinc-containing metal-organic frameworks with one-dimensional, two-dimensional or three-dimensional structures, such as cubic nanocrystals.

In the above preparation method, preferably, the zinc salt used includes one or a combination of zinc acetate dihydrate, zinc nitrate tetrahydrate, zinc nitrate hexahydrate and zinc acetate anhydrous.

In the above preparation method, preferably, the aromatic carboxylic acid used includes trimesic acid, 1,3,5-benzenetribenzoic acid, terephthalic acid, 2-aminoterephthalic acid and 4,4'-biphenyl One or a combination of dicarboxylic acids.

In the above preparation method, preferably, the organic solvent used includes one of N,N'-dimethylformamide, N,N'-diethylformamide and N,N'-dimethylacetamide or Several combinations.

In the above preparation method, preferably, the inert atmosphere refers to an atmosphere of N ₂ , Ar or He.

In the above preparation method, ZIF-67 nanocrystals can be prepared according to the conventional solvothermal method in this field, preferably, according to the following steps:

Dissolve 0.45g of cobalt nitrate hexahydrate in 3mL of water to obtain mixed solution 1;

5.5g of 2-methylimidazole was dissolved in 20mL of water to obtain mixed solution 2;

The mixed solution 1 and the mixed solution 2 were mixed, stirred for 6 h, centrifuged and dried to obtain ZIF-67 nanocrystals.

The present invention also provides a self-supporting homogeneous heterogeneous catalytic material, the self-supporting homogeneous heterogeneous catalytic material is prepared by the preparation method of the self-supporting homogeneous heterogeneous catalytic material of.

The self-supporting homogeneous heterogeneous catalytic material is a self-supporting homogeneous CoOx-N-C heterogeneous catalytic material. The outer shell is composed of a plurality of CoOx-N-C nanorods, and the inner core is composed of CoOx-N-C with a specific shape. , with a three-dimensional superstructure, high specific surface area, rich pores and easy magnetic recovery.

The above-mentioned self-supporting homogeneous heterogeneous catalytic material of the present invention can be used for degrading organic pollutants in sewage, especially for adsorbing and activating 4-nitrophenol in sewage.

The preparation method of the self-supporting homogeneous heterogeneous catalytic material of the present invention does not use a second carbon source and does not need an external nitrogen source, but directly performs high-temperature pyrolysis of the self-assembled nitrogen-containing and cobalt metal organic framework , after high-temperature pyrolysis, a self-supporting homogeneous heterogeneous catalytic material is obtained. The preparation method is simple, the steps are economical, and the unique morphology can be controlled at the same time (the core and the shell have the same composition: the shell is composed of multiple CoOx- N-C nanorods, the inner core is composed of CoOx-N-C with specific morphology), which makes the catalytic material have high activity and high stability in sewage treatment.

The self-supporting homogeneous heterogeneous catalytic material for sewage degradation obtained by the above-mentioned preparation method of the present invention has a relatively high specific surface area, is distributed between 600-900m ² ·g ^-1 , and has a large number of mesopores. There are distributions between 2-10nm.

The above-mentioned self-supporting homogeneous heterogeneous catalytic material of the present invention is applied to sewage degradation, which can well adsorb and activate 4-nitrophenol in sewage, and can realize 4-nitrophenol within a few minutes. Complete degradation of phenols. Moreover, the catalytic material is convenient to recycle after repeated use, can be reused 11 times without significant decrease in activity, and has high stability.

Description of drawings

Figure 1 is a schematic diagram of the synthesis of the self-supporting homogeneous CoOx-N-C heterogeneous catalytic material of Example 1.

FIG. 2 a is a scanning electron microscope (SEM) image of the ZIF-67 nanocrystal of Example 1. FIG.

FIG. 2b is a scanning electron microscope (SEM) image of the Zn-BTC nanofibers of Example 1. FIG.

FIG. 2c is a scanning electron microscope (SEM) image of the Co/Zn-BTC/ZIF-67 precursor of Example 1. FIG.

2d is a scanning electron microscope (SEM) image of the self-supporting homogeneous CoOx-N-C heterogeneous catalytic material of Example 1.

Fig. 3a is a transmission electron microscope (TEM) image of the self-supporting homogeneous CoOx-N-C heterogeneous catalytic material of Example 1.

Fig. 3b is a surface distribution diagram of C and elements in the shell structure in the self-supporting homogeneous CoOx-N-C heterogeneous catalytic material of Example 1.

Fig. 3c is a surface distribution diagram of the N element of the shell structure in the self-supporting homogeneous CoOx-N-C heterogeneous catalytic material of Example 1.

Fig. 3d is a surface distribution diagram of the O element in the shell structure in the self-supporting homogeneous CoOx-N-C heterogeneous catalytic material of Example 1.

3e is a surface distribution diagram of the Co element in the shell structure in the self-supporting homogeneous CoOx-N-C heterogeneous catalytic material of Example 1.

Fig. 3f is a surface distribution diagram of the C element of the core structure in the self-supporting homogeneous CoOx-N-C heterogeneous catalytic material of Example 1.

3g is a surface distribution diagram of the N element of the core structure in the self-supporting homogeneous CoOx-N-C heterogeneous catalytic material of Example 1.

Fig. 3h is a surface distribution diagram of the O element in the core structure in the self-supporting homogeneous CoOx-N-C heterogeneous catalytic material of Example 1.

Fig. 3i is a surface distribution diagram of the Co element in the core structure in the self-supporting homogeneous CoOx-N-C heterogeneous catalytic material of Example 1.

4 is an X-ray diffraction (XRD) spectrum of the self-supporting homogeneous CoOx-N-C heterogeneous catalytic material of Example 1.

Figure 5a is the N1s X-ray photoelectron spectrum of the self-supporting homogeneous CoOx-N-C heterogeneous catalytic material of Example 1.

Fig. 5b is a Co2p X-ray photoelectron spectrum of the self-supporting homogeneous CoOx-N-C heterogeneous catalytic material of Example 1.

Fig. 6a is the N ₂ adsorption/desorption isotherm diagram of the self-supporting homogeneous CoOx-NC heterogeneous catalytic material of Example 1.

Fig. 6b is a graph showing the mesopore diameter distribution curve of the self-supporting homogeneous CoOx-N-C heterogeneous catalytic material of Example 1.

7 is a hysteresis loop diagram of the self-supporting homogeneous CoOx-N-C heterogeneous catalytic material of Example 1.

Fig. 8 is a graph showing the change of absorbance with time in the degradation of 4-nitrophenol of the self-supporting homogeneous CoOx-N-C heterogeneous catalytic material in Example 1.

9 is a fitting diagram of the pseudo-first-order kinetic number rate constant for the catalytic reaction of the self-supporting homogeneous CoOx-N-C heterogeneous catalytic material in Example 1.

Fig. 10 is the repeated use stability test result of the self-supporting homogeneous CoOx-N-C heterogeneous catalytic material of Example 1.

Detailed ways

In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solution of the present invention is described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

Example 1

This embodiment provides a method for preparing a self-supporting homogeneous CoOx-N-C heterogeneous catalytic material, as shown in Figure 1, which includes the following steps:

Preparation of ZIF-67 nanocrystals:

Dissolve 0.45g of cobalt nitrate hexahydrate and 5.5g of 2-methylimidazole in 3mL of deionized water and 20mL of deionized water respectively, then mix the above two solutions under stirring, and continue stirring the obtained mixture at room temperature for 6h , ZIF-67 nanocrystals were obtained after centrifugal drying.

Preparation of Zn-BTC nanofibers:

Dissolve 5mmol of zinc acetate dihydrate and 6mmol of trimesic acid in 50mL of N,N'-dimethylformamide, stir at room temperature for 30min, heat-treat at 140°C for 12h, filter, wash and dry to obtain Zn- BTC nanofibers.

Preparation method of self-supporting homogeneous CoOx-N-C heterogeneous catalytic material:

Weigh 0.045g of ZIF-67 and disperse it in 10mL of deionized water, weigh 0.5g of Zn-BTC nanofibers and add them to the above suspension, stir at room temperature for 1.5h, filter and dry to obtain the core and shell composition are both Zn Pre-body of /Co-MOF-i/ZIF-67;

The above precursor was placed in a quartz boat, and in a nitrogen atmosphere, the temperature was raised to 800°C at a rate of 5°C/min, and kept at this temperature for 2h to obtain a self-supporting homogeneous CoOx-N-C heterogeneous catalytic material.

The self-supporting homogeneous CoOx-NC heterogeneous catalytic material prepared in Example 1 was characterized by techniques such as SEM, TEM, XRD, XPS and low-temperature _N2 adsorption/desorption.

The scanning electron micrographs of ZIF-67 nanocrystals, Zn-BTC nanofibers, Co/Zn-BTC/ZIF-67 precursors and self-supporting homogeneous CoOx-N-C heterogeneous catalytic materials prepared in Example 1 are shown in Figure 2a , Figure 2b, Figure 2c, and Figure 2d, it can be seen from the figure that ZIF-67 nanocrystals are in the shape of polyhedrons, and Zn-BTC is in the shape of fibers. After the interaction between the two, the resulting Co/Zn-BTC/ZIF- The outer shell of the 67 precursor is composed of a large number of nanorods, and the inner shell is a fibrous structure, and the self-supporting homogeneous CoOx-N-C heterogeneous catalytic material obtained after high temperature pyrolysis still maintains the original shape.

The transmission electron microscope image of the self-supporting homogeneous CoOx-N-C heterogeneous catalytic material prepared in Example 1 is shown in Figure 3a, and the surface distribution of C, N, O, and Co elements in the shell structure is shown in Figure 3b and Figure 3c , Figure 3d, and Figure 3e, the surface distribution diagrams of C, N, O, and Co elements in the core structure are shown in Figure 3f, Figure 3g, Figure 3h, and Figure 3i. It can be seen that the shell of the catalytic material is composed of multiple CoOx-N-C nanorods , the inner core is composed of CoOx-N-C with a specific morphology, which has a three-dimensional superstructure, and it can be seen from the surface scan that there are high contents of C, N, O and Co in the core and the shell, and Co exists in the form of nanoparticles .

The X-ray diffraction pattern of the self-supporting homogeneous CoOx-N-C heterogeneous catalytic material prepared in Example 1 is shown in Figure 4. It can be seen from the figure that there are six diffraction peaks in the catalytic material, wherein the angles are 36.5 °, 42.4° and 61.5° correspond to the (111), (200) and (220) crystal planes of CoO, respectively, and the angles of 44.2°, 51.5°, and 75.9° correspond to the (111), (200) and (220) crystal planes of Co, respectively. noodle.

The N1s X-ray photoelectron spectrum of the self-supporting homogeneous CoOx-N-C heterogeneous catalytic material prepared in Example 1 is shown in Figure 5a, and the Co2p X-ray photoelectron spectrum is shown in Figure 5b. It can be seen from 5a that there are two types of doped nitrogen atoms in the catalytic material, namely: pyrrole N (400.9eV) and pyridine nitrogen (398.9eV), the contents of which are 76.2at% and 23.8at%, respectively. It can be seen from Figure 5b that there are mainly two valence states of cobalt in the catalytic material, namely: Co0 2p3/2 (778.5eV), Co0 2p1/2 (793.3eV), CoO 2p3/2 (780.5eV) and CoO 2p1/2 (796.4eV), the contents are: 10.8at%, 5.3at%, 37.5at% and 20.4at%.

The N2 adsorption/desorption isotherm of the self-supporting homogeneous CoOx-NC heterogeneous catalytic material prepared in Example 1 is shown in Figure 6a, and the pore distribution curve is shown in Figure 6b. It can be seen from Figure 6a that the low temperature The N ₂ adsorption isotherm is a type IV curve, indicating that the catalytic material has a mesoporous structure; it can be seen from Figure 6b that the average mesopore size of the catalytic material is 3.9nm, and the BET specific surface area of the catalytic material is calculated to be 731m ² · g ^-1 , the pore volume is 1.07cm ³ ·g ^-1 .

Example 1 prepares the magnetic loop of the self-supporting homogeneous CoOx-N-C heterogeneous catalytic material as shown in Figure 7. From Figure 7, it can be seen that the maximum magnetization of the catalytic material is 20.56emu/g, which is It shows that the catalytic material has strong magnetism, which is beneficial to the magnetic recycling after the catalytic reaction.

The above results show that the self-supporting homogeneous CoOx-N-C heterogeneous catalytic material prepared by the method of the present invention has a three-dimensional superstructure, the shell is composed of a plurality of CoOx-N-C nanorods, and the core is composed of CoOx-N-C with a specific shape , high specific surface area, abundant pores, and easy magnetic recovery. These unique structures and properties endow the material with high activity and high stability in sewage treatment.

Example 2

This embodiment provides a method for preparing a self-supporting homogeneous CoOx-N-C-1 heterogeneous catalytic material, which includes the following steps:

Preparation of MOF-5:

Pipette 40mL of N,N'-dimethylformamide into a flask, degas it with nitrogen for about 40min, then add 5.60mmol of zinc nitrate hexahydrate and 2.12mmol of terephthalic acid and stir until dissolved. The mixture was quickly transferred to a reaction kettle, heated to 130 °C for 2 h, and cooled to room temperature. Wash with DMF and dry.

Preparation method of self-supporting homogeneous CoOx-N-C-1 heterogeneous catalytic material:

Weigh 0.035 g of ZIF-67 and disperse it in a mixture of 15 mL of deionized water and 15 mL of ethanol, and stir at room temperature for 30 min. Weigh 0.5g of MOF-5, add to the above suspension, stir at room temperature for 2h, filter and dry.

The Zn/Co-MOF-5/ZIF-67 powder obtained above was placed in a quartz boat, and in a nitrogen atmosphere, the temperature was raised to 600°C at a rate of 5°C/min and kept for 6h to obtain a self-supporting homogeneous CoOx - N-C-1 heterogeneous catalytic materials.

Example 3

This embodiment provides a method for preparing a self-supporting homogeneous CoOx-N-C-2 heterogeneous catalytic material, which includes the following steps:

Preparation of IRMOF-3:

Weigh 1.568g of zinc nitrate tetrahydrate and 0.332g of 2-aminoterephthalic acid and dissolve in 30mL of DMF. The mixture was transferred to a reaction kettle at 100°C for 24 hours, cooled to room temperature, washed with DMF, and dried.

Preparation method of self-supporting homogeneous CoOx-N-C-2 heterogeneous catalytic material:

Weigh 0.05g of ZIF-67 and disperse it in 20mL of N,N'-dimethylformamide, and stir at room temperature for 30min. Weigh 0.5g of IRMOF-3, add to the above suspension, stir at room temperature for 1h, filter and dry.

The Zn/Co-IRMOF-3/ZIF-67 powder obtained above was placed in a quartz boat, and in a nitrogen atmosphere, the temperature was raised to 900 °C at a rate of 5 °C/min and kept for 1 h to obtain a self-supporting homogeneous CoOx - N-C-2 heterogeneous catalytic material.

Example 4

This embodiment provides a method for preparing a self-supporting homogeneous CoOx-N-C-3 heterogeneous catalytic material, which includes the following steps:

Preparation of Zn-BTC nanodisks:

Dissolve 5 mmol of zinc acetate dihydrate and 6 mmol of trimesic acid in 50 mL of N,N'-dimethylformamide, stir at room temperature for 1 min, filter, wash and dry.

Preparation method of self-supporting homogeneous CoOx-N-C-3 heterogeneous catalytic material:

Weigh 0.05 g of ZIF-67 and disperse it in a mixture of 15 mL of N,N'-dimethylformamide and 15 mL of ethanol, and stir at room temperature for 30 min. Weigh 0.5 g of Zn-BTC nanodisk, add it into the above suspension, continue to stir for 2 h, filter and dry.

The Co/Zn-BTC/ZIF-67 powder obtained above was placed in a quartz boat, and in a nitrogen atmosphere, the temperature was raised to 550°C at a rate of 5°C/min and kept for 8h to obtain a self-supporting homogeneous CoOx-N-C -2 heterogeneous catalytic materials.

Example 5

This example provides the application of the self-supporting homogeneous CoOx-N-C heterogeneous catalytic material for sewage degradation prepared in Example 1 in sewage degradation, including the following steps:

(1) Reduction reaction of 4-nitrophenol in sewage:

Weigh 0.1 mg self-supporting homogeneous CoOx-N-C heterogeneous catalytic material into a quartz cuvette, then add 25 μL of 0.01M 4-nitrophenol solution and 2.5 mL of 0.01M sodium borohydride solution, and ultrasonically In a few seconds, a uniformly dispersed solid-liquid mixture is obtained. Under this condition, the conversion rate of 4-nitrophenol can reach more than 90.0% after 10 minutes of reaction.

A 754PC ultraviolet spectrophotometer (single beam, produced by Shanghai Jinghua Co., Ltd.) was used to monitor the reaction process, the scanning speed was medium, and the scanning range was 200-500 nm. Quickly put the quartz cuvette into the sample tank, and record the change of absorbance over time in the wavelength range of 200-500nm; when the absorbance of the sample no longer changes, stop collecting. 0.1mg self-supporting type homogeneous CoOx-N-C heterogeneous catalytic material catalyzes the ultraviolet-visible spectrum (UV-vis) scanning result figure of 4-nitrophenol reduction as shown in Figure 8, and Figure 8 shows that as the reaction proceeds , the absorption at 400nm gradually weakens, while the absorption at 295nm gradually increases, indicating that the reactant 4-nitrophenol is continuously consumed, and the product 4-aminophenol is generated, and the product content is continuously accumulated; the reaction mixture is recovered magnetically , after washing, 2.5 mL of 0.01 M sodium borohydride solution and 25 μL of 0.01 M 4-nitrophenol solution were added, mixed evenly, and the next reaction was carried out. 0.1mg self-supporting homogeneous CoOx-N-C heterogeneous catalytic material recycling results are shown in Figure 10, Figure 10 shows that after 11 times of repeated use of the catalytic material, the conversion rate of 4-nitrophenol is still More than 89%.

(2) Evaluation of 4-nitrophenol reduction performance:

According to previous literature, the reduction rate of 4-nitrophenol conforms to the pseudo-first-order reaction (Zubair Hasan, Dong-WanCho, Chul-Min Chon, Kwangsuk Yoon, Hocheol Song. Reduction of p-nitrophenol by magnetic Co-carbon composites derived from metal organic frameworks, Chemical Engineering Journal., 2016, 298, 183-190). According to the linear relationship of -ln(Ct/C0) vs kt, calculate the pseudo-first-order kinetic rate constant.

The fitting curve of the pseudo-first-order kinetic rate constant for the reduction of 4-nitrophenol catalyzed by the self-supporting homogeneous CoOx-NC heterogeneous catalytic material is shown in Figure 9. It is known through calculation that the specific rate of degradation of the catalytic material The constant is 6.88s ^-1 ·g ^-1 , which is higher than that of Co-NCC (2.17s ^-1 ·g ^-1 ) obtained by direct pyrolysis of ZIF-67 and supported noble metal Au/CuO catalyst (0.25s ^-1 ·g ^-1 ).

The above examples illustrate that the self-supporting homogeneous heterogeneous catalytic material of the present invention can degrade sewage and completely degrade 4-nitrophenol in sewage, and the catalytic material has high activity and high stability.

Claims (10)

1. A kind of 1. preparation method for the heterogeneous catalysis material that self-cradling type is homogeneously changed, it is characterised in that the preparation method include with Lower step：

   Zinc salt, aromatic carboxylic acids, organic solvent are mixed, obtain MOF-i；

   Using methylimidazole, cobalt nitrate as raw material, water is nanocrystalline for solvent synthesis ZIF-67；

   By the ZIF-67 is nanocrystalline, the MOF-i and solvent are with 0.07-0.1：1：The mass ratio mixing of 10-30, at room temperature 0.5h-3h is stirred, obtains Zn/Co-MOF-i/ZIF-67；

   Under an inert atmosphere, by the Zn/Co-MOF-i/ZIF-67 be pyrolyzed 1h-8h, obtain the self-cradling type homogeneously change it is more Phase catalysis material.
2. 2. preparation method according to claim 1, it is characterised in that the solvent includes water, ethanol and N, N'- dimethyl One or more of combinations in formamide.
3. 3. preparation method according to claim 1, it is characterised in that the temperature of the pyrolysis is 550 DEG C -950 DEG C.
4. 4. preparation method according to claim 1, it is characterised in that the mass ratio of the ZIF-67 and the MOF-i is 0.09:1。
5. 5. preparation method according to claim 1, it is characterised in that the inert atmosphere, refers in N₂, Ar or He gas Under atmosphere.
6. 6. preparation method according to claim 1, it is characterised in that the zinc salt, aromatic carboxylic acids, organic solvent mass ratio For 1:0.1-1.2:15-44.
7. 7. the preparation method according to claim 1 or 6, it is characterised in that the zinc salt includes two water zinc acetates, four water nitre One or more of combinations in sour zinc, zinc nitrate hexahydrate and anhydrous zinc acetate；

   The aromatic carboxylic acids includes trimesic acid, three benzoic acid of 1,3,5- benzene, terephthalic acid (TPA), 2- amino terephthalic acid (TPA)s With one or more of combinations of 4,4'- diphenyl dicarboxylic acids；

   The organic solvent includes N, N'- dimethylformamides, N, in N'- diethylformamides and N, N'- dimethylacetylamide One or more of combinations.
8. 8. preparation method according to claim 1, it is characterised in that the ZIF-67 is nanocrystalline according to following steps system It is standby：

   The cobalt nitrate hexahydrate of 0.45g is dissolved in 3mL water, obtains mixed liquor one；

   The 2-methylimidazole of 5.5g is dissolved in 20mL water, obtains mixed liquor two；

   The mixed liquor one and the mixed liquor two are mixed, stir 6h, is centrifuged, to be dried to obtain the ZIF-67 nanocrystalline.
9. A kind of 9. heterogeneous catalysis material that self-cradling type is homogeneously changed, it is characterised in that the heterogeneous catalysis that the self-cradling type is homogeneously changed Material is that the preparation method for the heterogeneous catalysis material homogeneously changed by claim 1-8 any one of them self-cradling types is prepared 's.
10. 10. the application for the heterogeneous catalysis material that the self-cradling type described in claim 9 is homogeneously changed, it is characterised in that the self-supporting The heterogeneous catalysis material that type is homogeneously changed is for the organic pollution in sewage of degrading.