A bimetallic ZIFs-supported nanocatalyst and its preparation method and application

Abstract

The present invention provides a bimetallic ZIFs-supported nanocatalyst, a preparation method, and an application thereof. The bimetallic ZIFs-supported nanocatalyst of the present invention comprises a Zn-Cu bimetallic ZIFs material and metal Cu(0) supported on the Zn-Cu bimetallic ZIFs material. The preparation method of the catalyst of the present invention comprises: contacting a dispersion of the Zn-Cu bimetallic ZIFs material with a reducing agent to obtain the bimetallic ZIFs-supported nanocatalyst. The catalyst of the present invention exhibits high catalytic activity and stability in the catalytic degradation of p-nitrophenol.

Description

Technical Field

[0001] The present invention relates to the technical field of nanocatalytic materials, and in particular to a bimetallic ZIFs-supported nanocatalyst and a preparation method and application thereof. Background Art

[0002] Nitroaromatic compounds are an important class of chemical raw materials, widely used in the production of pharmaceuticals, pesticides, dyes, insecticides, and other chemical products. Most of these compounds are highly toxic and can oxidize hemoglobin to methemoglobin, causing it to lose its oxygen-carrying function. In severe cases, this can cause central nervous system excitation and other neurological symptoms, making them highly stable organic pollutants. Among them, p-nitrophenol (Pnp), an endocrine disruptor, can remain in water for long periods of time and can severely disrupt hormones in humans and animals, leading to endocrine dysfunction and impacting growth, development, reproductive function, and reproduction. Developing high-performance, stable catalysts to address p-nitrophenol in water poses a significant environmental challenge.

[0003] Nanomaterials refer to materials that have at least one dimension in the nanometer size (1-100nm) in three-dimensional space or are composed of nanometer-sized particles as basic units. Nanosized metal particles (such as Au, Ag, Cu, Pd, etc.) have unique physical properties such as light, electricity, sound, heat, and magnetism, as well as characteristics such as quantum size effect and quantum tunneling effect. Since their birth, they have attracted widespread attention in many fields. Due to the excellent electron conductivity and high surface energy of metals at the nanoscale, they have excellent catalytic properties and can be used to replace bulk catalysts. Among them, Cu nanocatalysts have greater development potential than other precious metal nanomaterials due to their abundant sources, low price and excellent performance. Cu nanoparticles have the characteristics of large specific surface area, and the surface atoms are obviously unstable. Once they encounter other atoms, they tend to quickly combine to stabilize them, greatly improving the efficiency of the participating reactions and obtaining highly selective products. However, the microenvironment for synthesizing copper nanoparticles is complex, growth control is difficult, and the synthesized size is often uneven. The high activity of Cu nanoparticles makes them easily inactivated, and they are extremely easily oxidized in an oxygen atmosphere, which also limits their development. It is necessary to find appropriate carriers to stabilize and disperse Cu nanoparticles so that they can ensure high activity while taking into account cyclic stability. Summary of the Invention

[0004] In order to solve one of the above technical problems existing in the prior art, the present invention provides a bimetallic ZIFs-supported nanocatalyst and a preparation method and application thereof.

[0005] A first aspect of the present invention provides a bimetallic ZIFs-supported nanocatalyst, which comprises a Zn-Cu bimetallic ZIFs material and metal Cu(0) supported on the Zn-Cu bimetallic ZIFs material.

[0006] Zeolitic imidazolate frameworks (ZIFs) are multifunctional MOFs based on imidazole ligands, such as ZIF-8 and ZIF-67. Given the excellent thermal and chemical stability of ZIFs, the present inventors have inventively discovered that using Zn-Cu bimetallic ZIFs as a support and loading metallic Cu, particularly in situ loading, can improve the stability and size uniformity of Cu nanoparticles, resulting in a wider range of Cu nanocomposites with unique morphologies, large specific surface areas, and enhanced adsorption and catalytic properties.

[0007] According to some embodiments of the present invention, the metal Cu(0) is supported on the Zn-Cu bimetallic ZIFs material by in-situ growth. According to some embodiments of the present invention, the metal Cu(0) is nano-copper. In some embodiments, the average particle size of the metal Cu(0) is 1-100 nm, for example, 1-50 nm.

[0008] According to some embodiments of the present invention, based on the total mass of the catalyst, the molar content of the Zn element in the catalyst is 5-15%, for example, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, etc.

[0009] According to some embodiments of the present invention, based on the total mass of the catalyst, the molar content of Cu element in the catalyst is 15-25%, for example, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, etc.

[0010] According to some embodiments of the present invention, in the catalyst, the mass ratio of Zn element to Cu element is 1:(1-3), for example, 1:1, 1:1.2, 1:1.5, 1:1.8:1:2, 1:2.2, 1:2.5, 1:2.8, 1:3, etc., preferably 1:(1.5-2).

[0011] According to some embodiments of the present invention, the Zn-Cu bimetallic ZIFs material also includes Zn ions, Cu ions and a ligand combined with the Zn ions and Cu ions, and the ligand includes an imidazole ligand. In some embodiments, the imidazole ligand includes imidazole or an imidazole substituted by an alkyl group of C1-C6. In some embodiments, the imidazole ligand includes imidazole or an imidazole substituted by an alkyl group of C1-C4 (such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, etc.). In some embodiments, the ligand includes the imidazole substituted by methyl. In some specific embodiments, the ligand includes 2-methylimidazole.

[0012] According to some embodiments of the present invention, the average particle size of the Zn-Cu bimetallic ZIFs material is 1-50 μm, preferably 1-20 μm. In some specific embodiments, the average particle size of the Zn-Cu bimetallic ZIFs material is 5-10 μm.

[0013] According to some embodiments of the present invention, the Zn-Cu bimetallic ZIFs material has a rose-shaped structure.

[0014] According to some embodiments of the present invention, the average particle size of the bimetallic ZIFs-supported nanocatalyst is 1-20 μm, preferably 5-15 μm. In some specific embodiments, the average particle size of the bimetallic ZIFs-supported nanocatalyst is 8-10 μm.

[0015] According to some embodiments of the present invention, the bimetallic ZIFs-supported nanocatalyst has a rose-shaped structure.

[0016] The second aspect of the present invention provides a method for preparing the bimetallic ZIFs-supported nanocatalyst according to the first aspect, comprising the following steps:

[0017] The dispersion of the Zn-Cu bimetallic ZIFs material is brought into contact with a reducing agent and reacted to obtain the bimetallic ZIFs supported nanocatalyst.

[0018] The present invention uses Zn-Cu bimetallic ZIFs as templates and selects appropriate reducing agents to prepare zinc-copper composite nanomaterials, which can well retain the advantages of the original components of ZIFs and give full play to the synergistic effect of different components, thereby overcoming the low conductivity of the original ZIFs and improving the catalytic activity. The method of the present invention grows Cu metal nodes in situ on ZIFs without the use of templates or the addition of exogenous Cu. 2+ Cu nanocomposites with uniform size and good stability can be prepared.

[0019] According to some embodiments of the present invention, in the dispersion of the Zn-Cu bimetallic ZIFs material, the concentration of the Zn-Cu bimetallic ZIFs material is 1 to 15 mg / mL, for example, 1 mg / mL, 2 mg / mL, 3 mg / mL, 5 mg / mL, 8 mg / mL, 10 mg / mL, 12 mg / mL, 15 mg / mL, etc., preferably 3 to 10 mg / mL.

[0020] According to some embodiments of the present invention, the dispersion of the Zn-Cu bimetallic ZIFs material further includes a solvent, and the solvent preferably includes water.

[0021] According to some embodiments of the present invention, the reducing agent comprises one or more of sodium borohydride, ascorbic acid, and hydrazine hydrate. In some embodiments, the reducing agent comprises one or more of sodium borohydride solution, ascorbic acid solution, and hydrazine hydrate solution. In some embodiments, the concentration of the reducing agent is 10 to 100 mM, preferably 15 to 50 mM. In some embodiments, the reducing agent comprises a sodium borohydride solution with a concentration of 10 to 100 mM, an ascorbic acid solution with a concentration of 10 to 100 mM, and a hydrazine hydrate solution with a concentration of 10 to 100 mM.

[0022] According to some embodiments of the present invention, the volume ratio of the dispersion of the Zn-Cu bimetallic ZIFs material to the reducing agent is 1:(1-1.2).

[0023] According to some embodiments of the present invention, the reaction temperature is 20-40° C., and the reaction time is 1-3 hours.

[0024] According to some embodiments of the present invention, the Zn-Cu bimetallic ZIFs material is prepared by a method comprising the following steps:

[0025] S1. Mixing a zinc precursor solution and a copper precursor solution to obtain a zinc-copper precursor mixture;

[0026] S2. Mixing the zinc-copper precursor mixture with the ligand solution to react, to obtain the Zn-Cu bimetallic ZIFs material.

[0027] According to some embodiments of the present invention, in step S1, the zinc precursor includes an inorganic acid salt of zinc and / or an organic acid salt of zinc, preferably including one or more of zinc nitrate, zinc chloride, zinc acetate, zinc sulfate, and zinc gluconate.

[0028] According to some embodiments of the present invention, in step S1, the copper precursor includes an inorganic acid salt of copper and / or an organic acid salt of copper, preferably including one or more of copper nitrate, copper chloride, copper acetate, copper sulfate, and copper gluconate.

[0029] According to some embodiments of the present invention, in step S1, the concentration of the zinc precursor solution is 0.0225-0.0275 mol / L.

[0030] According to some embodiments of the present invention, in step S1, the concentration of the copper precursor solution is 0.0675-0.0825 mol / L.

[0031] According to some embodiments of the present invention, in step S1, the volume ratio of the zinc precursor solution to the copper precursor solution is 1:(0.5-2), preferably 1:(0.8-1.7).

[0032] According to some embodiments of the present invention, in step S2, the concentration of the ligand in the ligand solution is 0.3-0.5 mol / L, preferably 0.35-0.45 mol / L, and more preferably 0.38-0.42 mol / L.

[0033] According to some embodiments of the present invention, in step S2, the volume ratio of the metal precursor mixture to the ligand solution is 1:(0.5-2), preferably 1:(0.8-1.5).

[0034] According to some embodiments of the present invention, in step S2, the volume ratio of the zinc-copper precursor mixture to the ligand solution is 2:(1.8-2.7).

[0035] According to some embodiments of the present invention, in step S2, the reaction temperature is 25-35° C., and the reaction time is 8-16 h.

[0036] According to some embodiments of the present invention, step S2 further comprises: mixing the zinc-copper precursor mixture with the ligand solution and then subjecting the mixture to ultrasonic treatment. In some embodiments, the ultrasonic treatment lasts for 10 to 60 minutes, preferably 15 to 40 minutes. In some embodiments, the ultrasonic treatment frequency is 20 kHz to 55 kHz, preferably 30 kHz to 40 kHz.

[0037] According to some embodiments of the present invention, in step S2, after the reaction is completed, the reaction liquid is subjected to solid-liquid separation, and the solid phase is dried to obtain the Zn-Cu bimetallic ZIFs material.

[0038] According to some embodiments of the present invention, the method for preparing the bimetallic ZIFs-supported nanocatalyst comprises the following steps:

[0039] mixing a zinc precursor solution and a copper precursor solution to obtain a zinc-copper precursor mixture;

[0040] The zinc-copper precursor mixture is mixed with the ligand solution to react to obtain the Zn-Cu bimetallic ZIFs material;

[0041] The dispersion of the Zn-Cu bimetallic ZIFs material is brought into contact with a reducing agent and reacted to obtain the bimetallic ZIFs supported nanocatalyst.

[0042] The third aspect of the present invention provides the use of the bimetallic ZIFs-supported nanocatalyst described in the first aspect or the bimetallic ZIFs-supported nanocatalyst obtained by the preparation method described in the second aspect in catalytic degradation of nitroaromatic compounds.

[0043] The nitro aromatic compound of the present invention includes p-nitrophenol.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] 1. First, the metal ion salts selected in the present invention are zinc salts and copper salts of non-noble metals, the raw materials are easily available and low in cost, and the synthesis method is simple and mild.

[0046] 2. The obtained MOFs material ZnCu-NR has high crystallinity, good hydrothermal stability and unique nano-roset morphology. It has a rich pore structure, a larger specific surface area, stronger adsorption and catalytic properties, exposes more accessible active sites, and has a higher carrier mobility during the catalytic process.

[0047] 3. Cu nanoparticles are partially reduced from in-situ Cu ion coordination nodes and spatially confined within the bimetallic MOFs, eliminating the need for an additional copper source. Unreduced Zn nodes provide support to prevent collapse of the framework. The synthesized Cu nanoparticles exhibit small size and excellent dispersibility, demonstrating high activity and stability in the catalytic degradation of PnP. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is a scanning electron microscope image of the nano-rose-shaped ZnCu-NR material prepared in Example 1 of the present invention.

[0049] Figure 2 This is a set of XRD patterns of ZnCu-NR and prepared in Example 1 of the present invention and a comparison group of Cu single substance standard cards.

[0050] Figure 3 These are low-magnification and high-magnification transmission electron microscope images of the Cu(0)@ZnCu-NR composite material prepared in Example 1 of the present invention, and the built-in illustration is a particle size distribution histogram of the nanoparticles.

[0051] Figure 4This is the element distribution diagram of the composite material Cu(0)@ZnCu-NR prepared in Example 1 under the high-angle annular dark field mode.

[0052] Figure 5 This is a high-resolution transmission electron microscope image of the composite material Cu(0)@ZnCu-NR prepared in Example 1 of the present invention.

[0053] Figure 6 This is an energy spectrum analysis diagram of the composite material Cu(0)@ZnCu-NR prepared in Example 1 of the present invention.

[0054] Figure 7 This is the ultraviolet absorption graph of the catalytic reduction of Pnp by the composite material Cu(0)@ZnCu-NR catalyst prepared in Example 1 of the present invention.

[0055] Figure 8 This is a time-tracking ultraviolet absorption spectrum of the degradation effect of the composite material Cu(0)@ZnCu-NR catalyst prepared in Example 1 of the present invention on the catalytic reduction of Pnp.

[0056] Figure 9 This is a schematic diagram of the circulation effect of the composite material Cu(0)@ZnCu-NR catalyst prepared in Example 1 of the present invention.

[0057] Figure 10 This is a scanning electron microscope image of the Cu(0)@Zn-ZIFs catalyst prepared in the comparative example of the present invention.

[0058] Figure 11 This is a time-tracking ultraviolet absorption spectrum of the degradation effect of the Cu(0)@Zn-ZIFs catalyst prepared in the comparative example of the present invention on the catalytic reduction of Pnp. DETAILED DESCRIPTION

[0059] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments and drawings. The specific embodiments described herein are only used to illustrate the present invention and are not intended to constitute any limitation to the present invention.

[0060] Unless otherwise specified, the reagents used in the examples are all commercially available products or reagents prepared according to conventional methods. Unless otherwise specified, the methods used in the examples are all conventional experimental methods. Unless otherwise specified, the instruments used in the examples are all commercially available.

[0061] Example 1

[0062] (1) Prepare 100 mL of zinc nitrate hexahydrate solution with a concentration of 0.025 mol / L as a zinc precursor solution; prepare 100 mL of copper nitrate trihydrate solution with a concentration of 0.078 mol / L as a copper precursor solution; take 30 mL of each of the colorless zinc precursor solution and the light blue copper precursor solution and mix them evenly to obtain a zinc-copper precursor mixture. Dissolve 2-methylimidazole in ultrapure water to prepare a colorless 2-methylimidazole precursor solution with a concentration of 0.40 mol / L.

[0063] (2) The zinc-copper precursor mixture was added to a 60 mL aqueous solution of 2-methylimidazole. The system was placed in an ultrasonic cleaning apparatus and the system temperature was controlled to maintain at 30 ± 5 °C for 25 minutes. The mixture was kept in a constant temperature water bath at 30 °C for 8 hours. A green precipitate was formed at the bottom of the flask.

[0064] (3) The product was collected by centrifugation at 10,000 rpm, washed three times alternately with ultrapure water and anhydrous ethanol, and placed in a vacuum drying oven at 80°C for 8 h. The product was a green powdery solid, namely ZnCu-NR.

[0065] (4) 100 mg of ZnCu-NR was dispersed in 30 mL of ultrapure water. 30 mL of a 28 mM NaBH4 aqueous solution was slowly added dropwise over 15 minutes with vigorous stirring. Bubbling was observed in the system, and the turbid liquid changed color from green to brown. After the reaction was continued for 1.5 h, the bubble generation rate had significantly decreased. The solid was centrifuged at 8000 rpm to collect the product and washed three times with ultrapure water to obtain the Cu(0)@ZnCu-NR catalyst.

[0066] Example 2

[0067] (1) Prepare 100 mL of zinc nitrate hexahydrate solution with a concentration of 0.026 mol / L as a zinc precursor solution; prepare 100 mL of copper nitrate trihydrate solution with a concentration of 0.080 mol / L as a copper precursor solution; take 30 mL of each of the colorless zinc precursor solution and the light blue copper precursor solution and mix them evenly to obtain a zinc-copper precursor mixture. Dissolve 2-methylimidazole in ultrapure water to prepare a colorless 2-methylimidazole precursor solution with a concentration of 0.40 mol / L.

[0068] (2) The zinc-copper precursor mixture was added to a 60 mL aqueous solution of 2-methylimidazole. The system was placed in an ultrasonic cleaning apparatus and the system temperature was controlled to maintain at 30 ± 5 °C for 30 minutes. The mixture was kept in a constant temperature water bath at 30 °C for 15 hours. A green precipitate was formed at the bottom of the flask.

[0069] (3) The product was collected by centrifugation at 10,000 rpm, washed three times alternately with ultrapure water and anhydrous ethanol, and placed in a vacuum drying oven at 80°C for 8 h. The product was a green powdery solid, namely ZnCu-NR.

[0070] (4) 100 mg of ZnCu-NR was dispersed in 20 ml of ultrapure water. 20 mL of a 15 mM aqueous hydrazine hydrate solution was slowly added dropwise over 10 minutes with vigorous stirring. The system was accompanied by a large amount of bubbling, and the color of the turbid liquid changed from green to brown. After the reaction was continued for 2 h, the bubble generation rate had significantly decreased. The solid was centrifuged at 8000 rpm to collect the product and washed three times with ultrapure water to obtain the Cu(0)@ZnCu-NR catalyst.

[0071] Example 3

[0072] (1) Prepare 100 mL of zinc acetate dihydrate solution with a concentration of 0.025 mol / L as a zinc precursor solution; prepare 100 mL of copper acetate monohydrate solution with a concentration of 0.075 mol / L as a copper precursor solution; take 20 mL of each of the colorless zinc precursor solution and the light blue copper precursor solution and mix them evenly to obtain a zinc-copper precursor mixture. Dissolve 2-methylimidazole in ultrapure water to prepare a colorless 2-methylimidazole precursor solution with a concentration of 0.396 mol / L.

[0073] (2) The zinc-copper precursor mixture was added to 40 mL of 2-methylimidazole aqueous solution. The system was placed in an ultrasonic cleaning instrument and the system temperature was controlled to maintain at 30 ± 5 °C for 15 minutes. The mixture was kept in a constant temperature water bath at 30 °C for 8 hours. A green precipitate was formed at the bottom of the flask.

[0074] (3) The product was collected by centrifugation at 10,000 rpm, washed three times alternately with ultrapure water and anhydrous ethanol, and placed in a vacuum drying oven at 80°C for 8 h. The product was a green powdery solid, namely ZnCu-NR.

[0075] (4) Disperse 100 mg of ZnCu-NR in 10 mL of aqueous solution, and slowly add 10 mL of 50 mM ascorbic acid aqueous solution dropwise over 10 minutes with vigorous stirring. The turbid liquid changes color from green to brown. After the reaction is continued for 1.5 hours, the solid is centrifuged at 8000 rpm to collect the product and washed three times with ultrapure water to obtain the Cu(0)@ZnCu-NR catalyst.

[0076] Comparative Example

[0077] (1) Prepare 100 mL of zinc nitrate hexahydrate solution with a concentration of 0.025 mol / L as a zinc precursor solution. Dissolve 2-methylimidazole in ultrapure water to prepare a colorless 2-methylimidazole precursor solution with a concentration of 0.42 mol / L. Add 30 mL of the zinc precursor solution to 60 mL of the 2-methylimidazole aqueous solution. Place the system in an ultrasonic cleaning apparatus and maintain the system temperature at 30±5°C for 25 minutes. Keep the temperature in a constant temperature water bath at 30°C for 8 hours. A white precipitate will form at the bottom of the flask.

[0078] (2) The product was collected by centrifugation at 10,000 rpm, washed three times alternately with ultrapure water and anhydrous ethanol, and placed in a vacuum drying oven at 80°C for 8 h. The product was a white powdery solid, namely Zn-ZIFs.

[0079] (3) Disperse 540 mg of blue copper nitrate trihydrate crystals in 30 mL of methanol to obtain a blue methanol solution. Disperse the Zn-ZIFs in step (2) in the copper nitrate trihydrate aqueous solution and stir with a magnetic stirrer for 3 h to fully immerse the Zn-ZIFs in the solution. Slowly drop 30 mL of a 28 mM NaBH4 aqueous solution over 15 minutes and stir vigorously. The system is accompanied by a large amount of bubbling, and the color of the turbid liquid changes from blue to brown. After the reaction is continued for 1.5 h, the bubble generation rate has greatly decreased. After stopping stirring, the supernatant is still blue. The solid is centrifuged at 8000 rpm to collect the product and washed three times with ultrapure water and methanol to obtain a Cu(0)@Zn-ZIFs catalyst.

[0080] Catalyst structure and composition characterization

[0081] Figure 1 This is a scanning electron microscope image of the nano-rose-shaped ZnCu-NR material obtained in Example 1 of the present invention. Figure 1 It can be seen that the morphology of ZnCu-NR under the scanning electron microscope is self-assembled nano-rose particles with a single and uniform morphology, and the size of a single particle is about 8-10μm.

[0082] Figure 2 The XRD patterns of the ZnCu-NR and Cu(0)@ZnCu-NR composite materials obtained in Example 1 of the present invention are compared with a standard Cu element card. The narrow and sharp peaks indicate that the formed MOFs have a long-range ordered structure, good crystallinity, and high purity. After in-situ reduction with a reducing agent, the XRD pattern of the composite material shows both the characteristic peaks of MOFs and the characteristic peaks of Cu element, achieving partial reduction of Cu ions to Cu atoms while maintaining the framework structure of the MOFs.

[0083] Figure 3Transmission electron microscopy images of the composite material Cu(0)@ZnCu-NR obtained in Example 1 of the present invention at different magnifications, where Figure 3 In the low-magnification image (a), we can see that the original MOFs material still maintains the morphology of the nano-rose after the reduction treatment, and the nanoparticles of the black substrate are evenly distributed on the MOFs sheet. Figure 3 (b) High-magnification image shows the detailed distribution of nanoparticles on the surface of the structure. The size of the formed nanoparticles is statistically analyzed in the inset, ranging from 10-13 nm.

[0084] Figure 4 This is the element distribution diagram of the composite material Cu(0)@ZnCu-NR prepared in Example 1 under the high-angle annular dark field mode.

[0085] The bright white contrast indicates the region where nanoparticles are formed. The elemental distribution shows that C, N, Cu, and Zn are evenly distributed throughout the material. The non-metallic element C originates from the carbon skeleton of the organic ligand, while N comes from the imidazole group, demonstrating the preservation of the framework structure. The metallic element Zn illustrates the node distribution, while the distribution of Cu matches the region where nanoparticles are formed and is evenly distributed.

[0086] Figure 5 This is a high-resolution transmission electron microscope image of the composite material Cu(0)@ZnCu-NR prepared in Example 1 of the present invention. In the image, the lattice spacing of the Cu nanoparticles can be observed and it matches the 111 crystal plane of Cu very well.

[0087] Figure 6 This is an energy spectrum analysis diagram of the composite material Cu(0)@ZnCu-NR prepared in Example 1 of the present invention. It can be seen that the material is composed of Zn, Cu, C, and N. The relative mass ratio of Zn element to Cu element in the composite material Cu(0)@ZnCu-NR prepared in Example 1 was tested by inductively coupled plasma (ICP) and was 4.37:7.803. The molar content of Zn element was 10.75%, and the molar content of Cu element was 19.66%.

[0088] Catalytic effect test example

[0089] The catalytic reduction of Pnp pollutants was used as a model reaction to verify the catalytic activity and cyclic stability of the composite catalyst Cu(0)@ZnCu-NR prepared in Example 1 of the present invention and the Cu(0)@Zn-ZIFs prepared in Comparative Example 1. The specific operation is as follows:

[0090] 0.5 mL of NaNH₄ solution (0.59 mol L⁻¹) was added to a cuvette containing 1.5 mL of 0.27 mmol L⁻¹ PnP and the mixture was shaken thoroughly. Then, 1 mL of a 2.2 mg / mL catalyst was added to the mixture. After thorough mixing, the degradation process was monitored using a UV-visible spectrophotometer.

[0091] Figure 7 This is the UV absorption graph of the catalytic reduction of Pnp by the Cu(0)@ZnCu-NR composite catalyst prepared in Example 1 of the present invention. In the absence of the catalyst, the system exhibits a characteristic absorption peak for Pnp at 400 nm. After the catalyst is added, the absorption peak at 400 nm disappears, and a characteristic absorption peak for p-aminophenol appears at 300 nm, indicating successful degradation of Pnp.

[0092] Figure 8 This is a time-tracking UV absorption spectrum of the degradation effect of the Cu(0)@ZnCu-NR composite material catalyst prepared in Example 1 of the present invention on the catalytic reduction of PnP. It can be seen that the intensity of the characteristic absorption peak of PnP gradually decreases with time, achieving an excellent catalytic effect in a short period of time. This is due to the effective contact of the material structure with the catalytic substrate and the ultrahigh activity of the in-situ prepared nano-Cu.

[0093] In addition, the catalyst can be recycled. Figure 9 This figure is a schematic diagram of the cyclic effect of the Cu(0)@ZnCu-NR composite material catalyst prepared in Example 1 on the catalytic reduction of Pnp. The results show that after more than five catalytic cycles, the catalyst still retains high activity and stability.

[0094] Figure 10 This is a scanning electron microscope image of the Cu(0)@Zn-ZIFs obtained by the Cu ion impregnation method in the comparative example of the present invention. As can be seen from the figure, the obtained Cu(0)@Zn-ZIFs has a polyhedral structure. Figure 11 This is a time-tracking ultraviolet absorption spectrum of the degradation effect of the Cu(0)@Zn-ZIFs catalyst prepared in Comparative Example 1 on the catalytic reduction of Pnp. It can be seen that the time for the degradation of the Cu(0)@Zn-ZIFs prepared in Comparative Example 1 is significantly increased compared with the Cu(0)@ZnCu-NR prepared in Example 1, indicating that the activity of the composite material Cu(0)@ZnCu-NR catalyst prepared by in-situ growth of copper in the present invention is far superior to that of the Cu(0)@Zn-ZIFs catalyst obtained by the conventional impregnation method.

[0095] The technical solution of the present invention is not limited to the above-mentioned specific embodiments. Any technical variations made according to the technical solution of the present invention fall within the protection scope of the present invention.

Claims

1. A bimetallic ZIFs-supported nanocatalyst comprising a Zn-Cu bimetallic ZIFs material and metallic Cu(0) supported on the Zn-Cu bimetallic ZIFs material; based on the total mass of the catalyst, the molar content of the Zn element in the catalyst is 5-15%, and the molar content of the Cu element is 15-25%; the metallic Cu(0) is nano-copper; The preparation method of the bimetallic ZIFs supported nanocatalyst comprises the following steps: allowing a dispersion of the Zn-Cu bimetallic ZIFs material to contact and react with a reducing agent to obtain the bimetallic ZIFs-supported nanocatalyst; The volume ratio of the dispersion of the Zn-Cu bimetallic ZIFs material to the reducing agent is 1:(1-1.2).

2. The catalyst according to claim 1, characterized in that In the catalyst, the mass ratio of Zn element to Cu element is 1:(1-3); and / or, The metal Cu(0) is loaded on the Zn-Cu bimetallic ZIFs material by in-situ growth; and / or, The average particle size of the metal Cu(0) is 1-100 nm.

3. The catalyst according to claim 2, characterized in that In the catalyst, the mass ratio of Zn element to Cu element is 1:(1.5-2); and / or, The average particle size of the metal Cu(0) is 1-50 nm.

4. The catalyst according to claim 1, characterized in that The Zn-Cu bimetallic ZIFs material includes Zn ions, Cu ions, and ligands combined with the Zn ions and Cu ions, and the ligands include imidazole ligands.

5. The catalyst according to claim 4, characterized in that The ligand includes 2-methylimidazole.

6. The catalyst according to any one of claims 1 to 5, characterized in that The Zn-Cu bimetallic ZIFs material has a rose-shaped structure; and / or the average particle size of the bimetallic ZIFs-supported nanocatalyst is 1-50 μm; and / or the bimetallic ZIFs-supported nanocatalyst has a rose-shaped structure.

7. The catalyst according to claim 6, characterized in that The average particle size of the bimetallic ZIFs supported nanocatalyst is 1-20 μm.

8. The catalyst according to any one of claims 1 to 5, characterized in that In the dispersion of the Zn-Cu bimetallic ZIFs material, the concentration of the Zn-Cu bimetallic ZIFs material is 1 to 15 mg / mL; and / or, The dispersion of the Zn-Cu bimetallic ZIFs material further includes a solvent; and / or, The reducing agent includes one or more of sodium borohydride solution, ascorbic acid solution, and hydrazine hydrate solution; and / or, The concentration of the reducing agent is 10 to 100 mM; and / or, The reaction temperature is 20-40° C., and the reaction time is 1-3 hours.

9. The catalyst according to claim 8, characterized in that The concentration of the Zn-Cu bimetallic ZIFs material is 3 to 10 mg / mL; and / or, The solvent comprises water; and / or, The concentration of the reducing agent is 15-50 mM.

10. The catalyst according to any one of claims 1 to 5, characterized in that The Zn-Cu bimetallic ZIFs material is prepared by a method comprising the following steps: S1. Mixing a zinc precursor solution and a copper precursor solution to obtain a zinc-copper precursor mixture; S2. Mixing and reacting the zinc-copper precursor mixture with the ligand solution to obtain the Zn-Cu bimetallic ZIFs material.

11. The catalyst according to claim 10, characterized in that In step S1: The zinc precursor includes an inorganic acid salt of zinc and / or an organic acid salt of zinc; and / or, The copper precursor includes an inorganic acid salt of copper and / or an organic acid salt of copper; and / or, The concentration of the zinc precursor solution is 0.0225 to 0.0275 mol / L; and / or, The concentration of the copper precursor solution is 0.0675 to 0.0825 mol / L; and / or, The volume ratio of the zinc precursor solution to the copper precursor solution is 1:(0.5-2).

12. The catalyst according to claim 11, characterized in that The zinc precursor includes one or more of zinc nitrate, zinc chloride, zinc acetate, zinc sulfate, and zinc gluconate; and / or, The copper precursor includes one or more of copper nitrate, copper chloride, copper acetate, copper sulfate, and copper gluconate; and / or, The volume ratio of the zinc precursor solution to the copper precursor solution is 1:(0.8-1.7).

13. The catalyst according to claim 10, characterized in that In step S2: The concentration of the ligand in the ligand solution is 0.3 mol / L to 0.5 mol / L; and / or, The volume ratio of the zinc-copper precursor mixture to the ligand solution is 1:(0.5-2); and / or, The reaction temperature is 25 to 35° C., and the reaction time is 8 to 16 hours; and / or, Step S2 further includes: mixing the zinc-copper precursor mixture with the ligand solution and then performing ultrasonic treatment, wherein the ultrasonic treatment time is 10 minutes to 60 minutes; and / or, Step S2 also includes: after the reaction is completed, the reaction liquid is subjected to solid-liquid separation, and the solid phase is dried to obtain the Zn-Cu bimetallic ZIFs material.

14. The catalyst according to claim 13, characterized in that The concentration of the ligand in the ligand solution is 0.38 mol / L to 0.42 mol / L; and / or, The volume ratio of the zinc-copper precursor mixture to the ligand solution is 1:(0.8-1.5).

15. Use of the bimetallic ZIFs-supported nanocatalyst according to any one of claims 1 to 14 in catalytic degradation of nitroaromatic compounds.

16. The use according to claim 15, characterized in that The nitroaromatic compound includes p-nitrophenol.

Images