A core-shell molecular sieve composite for oxygenate treatment and a method of making

Abstract

This invention discloses a core-shell molecular sieve composite material and its preparation method for treating oxygen-containing volatile organic compounds, relating to the field of catalyst preparation technology. The method includes: firstly, using ZSM-5 as the core, a ZIF-67 shell layer is grown on the surface of ZSM-5 via a mechanochemical method to obtain a core-shell precursor; then, the core-shell precursor is heated in an air atmosphere, causing the 2-methylimidazole to be oxidized, decomposed, and volatilized, and the metallic cobalt to be oxidized, resulting in a porous ZSM-5@Co3O4; finally, Cu and Pd are introduced into ZSM-5@Co3O4 via a stepwise impregnation method, followed by reduction with NaBH4, and then drying and activation to obtain the core-shell molecular sieve composite material. This invention can achieve time, space, and temperature matching between the adsorption process and the catalytic oxidation process, and is particularly suitable for treating large volumes of low-concentration industrial waste gas.

Description

Technical Field

[0001] This invention relates to the field of catalyst preparation technology, specifically to a core-shell molecular sieve composite material for treating oxygen-containing volatile organic compounds and its preparation method. Background Technology

[0002] OVOCs (oxygenated volatile organic compounds) contain oxygen-containing functional groups such as hydroxyl, carbonyl, and carboxyl groups. Examples include methanol, ethanol, and acetone, which are widely used in chemical production processes. Their release has a significant impact on the environment and is detrimental to human health. Therefore, the treatment of OVOCs is a core focus of atmospheric chemistry and environmental governance.

[0003] Currently, existing end-of-pipe treatment technologies for OVOCs mainly include adsorption and catalytic oxidation. Adsorption (using porous materials such as activated carbon and molecular sieves) is suitable for treating low-concentration, high-volume waste gas, offering advantages such as simple equipment and low initial investment. However, adsorbents are prone to saturation, requiring frequent desorption and regeneration. The desorption process often generates high-concentration waste gas, requiring further treatment, and also suffers from adsorbent deactivation and limited lifespan. Catalytic oxidation lowers the activation energy of OVOCs oxidation reactions through catalysts, converting them into harmless CO2 and H2O. It is particularly suitable for purifying medium- to high-concentration waste gas, with the potential for thorough removal and relatively low energy consumption. However, catalytic oxidation typically consumes more energy, and while adsorbents can efficiently adsorb and enrich low-concentration OVOCs at room temperature or lower, after adsorption saturation, the desorbed pollutants can be catalytically oxidized in situ in the shell layer by programmed temperature increase. However, VOCs easily escape during the heating process.

[0004] Therefore, existing technologies have studied catalysts with core-shell structures. For example, application number 202110793126.9 discloses a core-shell VOCs adsorbent and its preparation method. The preparation method is as follows: S1, Preparation of the adsorbent "core": Weigh cerium nitrate, titanium sulfate, magnesium oxide and aluminum nitrate and add them to a 500ml beaker. Slowly add deionized water to the beaker and stir on a stirrer. After the reaction is completed, heat and age the mixture. Finally, filter, wash and dry the slurry to obtain the desired Ce-Ti-Mg-Al-Ox composite oxide "core"; S2, Weigh Ce-Ti S3. Mg-Al-Ox composite oxide was placed in a 100ml beaker, and deionized water was added. The mixture was stirred to obtain a viscous sample A. S4. Organic and inorganic additives were added to sample A, and the mixture was stirred and dried. The sample was then placed in a crucible and calcined at high temperature in a muffle furnace to obtain sample B. S5. Preparation of the adsorbent "shell": A mixed solution containing silicon, calcium, and zinc was impregnated onto sample B and dried to obtain sample C. S6. Sample C was oxidatively calcined under an oxidizing atmosphere to obtain a core-shell VOCs adsorbent. This adsorbent has a double-layered core-shell structure, which improves the adsorption capacity of VOCs.

[0005] However, the above-mentioned core-shell structured adsorbents still have the following technical problems: The aforementioned adsorbents have difficulty constructing a continuous, complete, and firmly bonded metal oxide shell on the surface of molecular sieves through physical mixing or simple impregnation methods. This can easily lead to uneven shells, easy detachment, or active components being mainly loaded on the surface of the molecular sieve rather than on the shell, making them prone to aggregation and failing to form an ideal "core-shell" spatial isolation and functional partitioning. In addition, VOCs adsorbed during the temperature-raising catalytic stage are prone to premature desorption and escape, resulting in technical problems of incomplete purification and secondary pollution.

[0006] This shows that the existing technology needs further improvement. Summary of the Invention

[0007] One of the objectives of this invention is to provide a method for preparing a core-shell molecular sieve composite material for the treatment of oxygen-containing volatile organic compounds, which can achieve matching of the adsorption process and the catalytic oxidation process in terms of time, space and temperature, and can achieve high dispersion of precious metals, thereby improving the utilization efficiency and catalytic activity of precious metals.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a core-shell molecular sieve composite material for treating oxygen-containing volatile organic compounds includes the following steps: a. Using ZSM-5 as the core, a ZIF-67 shell is grown on the surface of ZSM-5 by mechanochemical method to obtain the ZSM-5@ZIF-67 core-shell precursor; The specific steps are as follows: ZSM-5, cobalt nitrate hexahydrate, and 2-methylimidazole are added to a ball mill jar. Zirconia grinding balls are added to the ball mill jar. The mixture is then subjected to mechanical and chemical ball milling at a speed of 300-500 rpm on a planetary ball mill for 60-120 minutes. After the reaction is completed, the mixture is washed and dried to obtain the final product. The mass ratio of ZSM-5 to cobalt nitrate hexahydrate is 1 to 4:1; the mass ratio of cobalt nitrate hexahydrate to 2-methylimidazole is 1:4. b. The ZSM-5@ZIF-67 core-shell precursor is heated in an air or oxygen atmosphere at a temperature of 350-550℃, so that the 2-methylimidazole in ZIF-67 is oxidized, decomposed and volatilized, and the metallic cobalt is oxidized to obtain a porous ZSM-5@Co3O4. c. Cu and Pd are introduced into ZSM-5@Co3O4 by a stepwise impregnation method, then reduced by NaBH4, and after drying and activation, ZSM-5@Pd-Cu / Co3O4 core-shell molecular sieve composite material is obtained.

[0009] In the above-mentioned method for preparing a core-shell molecular sieve composite material for treating oxygen-containing volatile organic compounds, step a involves adding 10 zirconium oxide grinding balls with a diameter of 10 mm into a ball mill jar.

[0010] In the preparation method of the above-mentioned core-shell molecular sieve composite material for treating oxygen-containing volatile organic compounds, in step a, the mass ratio of ZSM-5 to cobalt nitrate hexahydrate is 3:1, and the material is mechanically and chemically ball-milled at a speed of 400 rpm on a planetary ball mill for 60 min.

[0011] In the preparation method of the core-shell molecular sieve composite material for treating oxygen-containing volatile organic compounds, the specific steps of introducing Cu in step c of the stepwise impregnation method are as follows: ZSM-5@Co3O4 is dispersed in deionized water, ultrasonically treated, and then copper nitrate trihydrate is added to the resulting dispersion and stirred at room temperature; the resulting solid is dried and calcined to obtain ZSM-5@Cu / Co3O4, wherein the copper loading mass is 1%.

[0012] The above-mentioned method for preparing a core-shell molecular sieve composite material for treating oxygen-containing volatile organic compounds involves introducing Pd into ZSM-5@Cu / Co3O4. The specific steps are as follows: ZSM-5@Cu / Co3O4 is dispersed in ethanol, NaPdCl4 aqueous solution is dispersed in the resulting dispersion, and then NaBH4 solution is slowly added dropwise to the resulting mixture. The mixture is stirred continuously at room temperature, centrifuged and filtered, the filter cake is washed, dried and activated to obtain ZSM-5@Pd-Cu / Co3O4, with a Pd loading mass of 0.1%.

[0013] The above-mentioned method for preparing a core-shell molecular sieve composite material for treating oxygen-containing volatile organic compounds involves dispersing ZSM-5@Co3O4 in 5 mL of deionized water, ultrasonically treating for 20 min, stirring at room temperature for 3–4 h, drying at 90–110 °C, calcining at 350–450 °C, and calcining for 3–5 h.

[0014] The above-mentioned method for preparing a core-shell molecular sieve composite material for treating oxygen-containing volatile organic compounds involves dispersing ZSM-5@Cu / Co3O4 in 50 mL of ethanol by ultrasonic dispersion for 10–30 min, stirring at room temperature for 3–4 h, centrifuging and filtering, washing the filter cake with ethanol 3–5 times, vacuum drying at 50–70 °C for 12 h, and activation in a tube furnace at 400 °C under a nitrogen atmosphere for 2 h to obtain ZSM-5@Pd-Cu / Co3O4.

[0015] In the above-mentioned method for preparing a core-shell molecular sieve composite material for treating oxygen-containing volatile organic compounds, step b involves heating at 450°C, heating at a rate of 3°C / min, and holding at the same temperature for 4 hours.

[0016] Another object of the present invention is to provide a core-shell molecular sieve composite material for the treatment of oxygen-containing volatile organic compounds, which is prepared by the above-described preparation method.

[0017] A core-shell molecular sieve composite material for treating oxygen-containing volatile organic compounds (OVOCs) has an inner core that adsorbs OVOCs at room temperature, while the outer shell completely oxidizes and decomposes OVOCs into carbon dioxide and water at a temperature of 220–240 °C.

[0018] Compared with the prior art, the present invention brings the following beneficial technical effects: This invention proposes a method for preparing a core-shell molecular sieve composite material for treating oxygen-containing volatile organic compounds. In terms of raw material selection, ZSM-5 microporous molecular sieve is selected as the core, which can adsorb OVOCs at room temperature. The shell is a Pd-Cu / Co3O4 catalyst that can catalytically oxidize OVOCs. This composite catalyst can enrich OVOCs at room temperature, and after adsorption saturation, it can achieve efficient conversion of OVOCs by raising the temperature to the catalytic oxidation temperature.

[0019] In terms of preparation method, this invention employs a mechanochemical method to grow a ZIF-67 shell on the surface of ZSM-5. By controlling the mass ratio of raw materials ZSM-5, cobalt nitrate hexahydrate, and 2-methylimidazole, the rotation speed and milling time of the planetary ball mill are controlled. Mechanochemical ball milling is performed at a speed of 300-500 rpm for 60-120 min. This process yields a shell of suitable thickness. When the ZSM-5@ZIF-67 core-shell precursor is heated in an air or oxygen atmosphere, the cobalt nodes and organic ligands of ZIF-67 can be converted in situ to Co3O4 during heating. Because Co and N elements are atomically uniformly distributed in the ZIF-67 lattice, the Co3O4 obtained after pyrolysis typically possesses a high specific surface area, abundant porous structure, and highly dispersed active sites. Compared to traditional impregnation or precipitation methods, the method of this invention has significant advantages. Furthermore, during the heating process, the original polyhedral morphology of ZIF-67 can be preserved to a certain extent, while the internal organic matter decomposes to form a large number of mesopores. This results in the final Co3O4 shell not only having highly active nanocrystals, but also forming a multi-level porous network that facilitates mass transport. This structure allows for uniform dispersion of Pd-Cu during the later loading process, preventing the agglomeration of noble metals.

[0020] In the adsorption stage of the core-shell molecular sieve composite material prepared by this invention, waste gas containing low concentrations of OVOCs passes through the material at room temperature. The catalyst in the outer shell does not work at room temperature, allowing OVOCs to pass smoothly through the shell and be adsorbed and stored in large quantities by the molecular sieve in the core. This process does not require additional heating, making it very energy-efficient. When the core is saturated with adsorbed waste gas, heating begins. The shell is a dense catalyst layer of Pd-Cu / Co3O4, which catalyzes the process. When the OVOCs in the core are desorbed by heat, they cannot escape directly into the atmosphere but must first pass through the outer catalytic shell. During this process, the OVOCs are catalytically oxidized into harmless CO2 and H2O. This solves the problem of pollutant escape during desorption in traditional adsorption methods. After the pollutants are completely removed, the catalyst is cooled to room temperature, and the next "adsorption-oxidation" cycle can begin. Therefore, the catalyst of this invention can be reused repeatedly and has good cycle performance.

[0021] In summary, this invention offers advantages such as energy efficiency, high performance, and no secondary pollution, and enables the matching of the adsorption and catalytic oxidation processes in terms of time, space, and temperature. This invention is widely applicable and particularly suitable for treating large volumes of low-concentration industrial waste gas, offering significant economic and environmental benefits. Attached Figure Description

[0022] The present invention will be further described below with reference to the accompanying drawings: Figure 1The image shows an HR-TEM image of the core-shell molecular sieve composite material prepared in Example 1. Figure 2 This is a mapping diagram of the core-shell molecular sieve composite material prepared in Example 1. Figure 2 (a) shows the TEM morphology; Figure 2 In (b), the elements are distributed with overlap. Figure 2 In the middle (c), the distribution of Al elements is shown. Figure 2 In the middle (d), the distribution of Si elements is shown. Figure 2 In the middle (e), the distribution of O elements is shown. Figure 2 In the diagram (f), the distribution of Co elements is shown. Figure 2 (g) represents the distribution of Cu elements. Figure 2 In the middle (h), the distribution of Pd elements is shown.

[0023] Figure 3 The graph shows the nitrogen adsorption-desorption curves of the core-shell molecular sieve composite material prepared in Example 1.

[0024] Figure 4 The image shows the XRD pattern of the core-shell molecular sieve composite material prepared in Example 1. Detailed Implementation

[0025] This invention proposes a core-shell molecular sieve composite material for treating oxygen-containing volatile organic compounds and its preparation method. To make the advantages and technical solutions of this invention clearer and more explicit, the invention will be further described below with reference to specific embodiments.

[0026] The oxygen-containing volatile organic compounds (OVOCs) mentioned in this invention refer to methanol, ethanol, acetone, etc.

[0027] The ZSM-5 mentioned in this invention is hydrogen-form ZSM-5 with a silicon-to-aluminum ratio of 25.

[0028] All the raw materials mentioned in this invention can be purchased through commercial channels.

[0029] Example 1:

[0030] A method for preparing a core-shell molecular sieve composite material for treating oxygen-containing volatile organic compounds specifically includes the following steps: Step 1: Preparation of ZSM-5@ZIF-67 core-shell precursor: ZSM-5 molecular sieve, cobalt nitrate hexahydrate (Co(NO3)2·6H2O), and 2-methylimidazole (2-MeIm) were added to a 50 mL zirconia ball mill jar. The mass ratio of ZSM-5 molecular sieve to cobalt nitrate hexahydrate was 3:1, and the mass ratio of cobalt nitrate hexahydrate to 2-methylimidazole was 1:4. Ten zirconia grinding balls with a diameter of 10 mm were added. The mixture was mechanically and chemically ball-milled at 400 rpm for 90 minutes on a planetary ball mill. After the reaction was completed, the product was removed, washed several times with ethanol to remove unreacted raw materials from the surface, and then vacuum dried at 60 °C for 12 hours to obtain powdered ZSM-5@ZIF-67 core-shell precursor.

[0031] Step 2: In an air (or oxygen) atmosphere, heat to 450℃ at a heating rate of 3℃ / min and hold at the temperature for 4 hours to oxidize and decompose the organic ligand (2-methylimidazole) in ZIF-67 and volatilize it. At the same time, the metallic cobalt is oxidized, leaving a porous cobalt oxide framework, namely ZSM-5@Co3O4.

[0032] Step 3: Introduce Cu into ZSM-5@Co3O4 using a stepwise impregnation method. Disperse ZSM-5@Co3O4 in 5 mL of deionized water, sonicate for 20 min, add copper nitrate trihydrate to the resulting dispersion, and stir at room temperature for 3–4 h. Dry the resulting solid at 90–110 °C and calcine at 350–450 °C for 3–5 h to obtain ZSM-5@Cu / Co3O4, in which the copper loading mass is 1%.

[0033] The specific steps for introducing Pd into ZSM-5@Cu / Co3O4 are as follows: ZSM-5@Cu / Co3O4 is dispersed in ethanol, NaPdCl4 aqueous solution is dispersed in the resulting dispersion, and then NaBH4 solution is slowly added dropwise to the resulting mixture. The mixture is stirred continuously at room temperature, centrifuged and filtered, the filter cake is washed, dried and activated to obtain ZSM-5@Pd-Cu / Co3O4, with a Pd loading mass of 0.1%.

[0034] Figure 1 The image shows the HR-TEM image of the core-shell molecular sieve composite material prepared in Example 1.

[0035] Figure 2 This is a mapping diagram of the core-shell molecular sieve composite material prepared in Example 1. Figure 2 (a) shows the TEM morphology; Figure 2 In (b), the elements are distributed with overlap. Figure 2 In the middle (c), the distribution of Al elements is shown. Figure 2 In the middle (d), the distribution of Si elements is shown. Figure 2In the middle (e), the distribution of O elements is shown. Figure 2 In the diagram (f), the distribution of Co elements is shown. Figure 2 (g) represents the distribution of Cu elements. Figure 2 In the middle (h), the distribution of Pd elements is shown.

[0036] Figure 3 The graph shows the nitrogen adsorption-desorption curves of the core-shell molecular sieve composite material prepared in Example 1.

[0037] Figure 4 The image shows the XRD pattern of the core-shell molecular sieve composite material prepared in Example 1.

[0038] Example 2: The difference from Example 1 is that in step one, the mass ratio of ZSM-5 molecular sieve to cobalt nitrate hexahydrate is 1:1.

[0039] Example 3: The difference from Example 1 is that in step one, the mass ratio of ZSM-5 molecular sieve to cobalt nitrate hexahydrate is 2:1.

[0040] Example 4: The difference from Example 1 is that in step one, the mass ratio of ZSM-5 molecular sieve to cobalt nitrate hexahydrate is 4:1.

[0041] Example 5: The difference from Example 1 is that in step one, mechanical chemical ball milling is performed at 300 rpm for 60 minutes on a planetary ball mill.

[0042] Example 6: The difference from Example 1 is that in step one, mechanical chemical ball milling is performed at a speed of 500 rpm for 120 minutes on a planetary ball mill.

[0043] Comparative Example 1: The preparation method of the ZSM-5@ZIF-67 core-shell precursor adopts existing technology, specifically as follows: Step 1: Calcine ZSM-5 in air at 550℃ for 4 hours. After cooling, wash and dry by alternating centrifugation with anhydrous ethanol and deionized water. Disperse ZSM-5 in 20 ml of anhydrous ethanol, add cobalt nitrate hexahydrate (Co(NO3)2·6H2O), sonicate for 60 min, centrifuge, wash and dry to obtain ZSM-5@Co. 2+ Then ZSM-5@ Co 2+ Dispersed in 40 ml of anhydrous ethanol containing 2-methylimidazole, the mixture was thoroughly mixed and then transferred to a high-pressure reactor. The reaction was carried out at 150 °C for 15 h. After the reaction was completed, the mixture was allowed to cool naturally, centrifuged, washed, and vacuum dried to obtain ZSM-5@ZIF-67.

[0044] Step 2: In an air (or oxygen) atmosphere, heat to 450℃ at a heating rate of 3℃ / min and hold at the temperature for 4 hours to oxidize and decompose the organic ligand (2-methylimidazole) in ZIF-67 and volatilize it. At the same time, the metallic cobalt is oxidized, leaving a porous cobalt oxide framework, namely ZSM-5@Co3O4.

[0045] Step 3: Introduce Cu into ZSM-5@Co3O4 using a stepwise impregnation method. Disperse ZSM-5@Co3O4 in 5 mL of deionized water, sonicate for 20 min, add copper nitrate trihydrate to the resulting dispersion, and stir at room temperature for 3–4 h. Dry the resulting solid at 90–110 °C and calcine at 350–450 °C for 3–5 h to obtain ZSM-5@Cu / Co3O4, in which the copper loading mass is 1%.

[0046] The specific steps for introducing Pd into ZSM-5@Cu / Co3O4 are as follows: ZSM-5@Cu / Co3O4 is dispersed in ethanol, NaPdCl4 aqueous solution is dispersed in the resulting dispersion, and then NaBH4 solution is slowly added dropwise to the resulting mixture. The mixture is stirred continuously at room temperature, centrifuged and filtered, the filter cake is washed, dried and activated to obtain ZSM-5@Pd-Cu / Co3O4, with a Pd loading mass of 0.1%.

[0047] Comparative Example 2: In step three, only 1% by mass of copper is loaded, and Pd is not loaded.

[0048] Comparative Example 3: The difference from Example 1 is that NaBH4 solution is not added in step three.

[0049] The catalysts prepared in Examples 1-6 and Comparative Examples 1-3 were applied to the adsorption of methanol. The specific steps were as follows: The adsorption performance of the catalysts was evaluated in a fixed-bed quartz reactor with an inner diameter of 6 mm. For each test, 500 mg of catalyst was uniformly mixed with an appropriate amount of quartz sand and filled to a column height of 30 mm. The feed reactants consisted of 500 ppm CH3OH and 21 vol% O2, with N2 as the equilibrium gas. The total flow rate was controlled at 100 ml / min, and the gas hourly space velocity (GHSV) was approximately 15,000 h⁻¹. -1 Adsorption was performed at 30℃, and the results are shown in Table 1.

[0050] Table 1

[0051] The catalysts prepared in Examples 1-6 and Comparative Examples 1-3 were applied to the post-adsorption catalytic purification stage. Specifically, during the catalytic oxidation regeneration process, methanol-free reaction gas was introduced into the reaction tube and purged for 30 min to remove methanol molecules adsorbed on the tube and sample surface. Then, a programmed temperature ramp oxidation was performed, heating to 400℃ at a rate of 5℃ / min. The results are shown in Table 2.

[0052] Table 2

[0053] Any parts not mentioned in this invention can be achieved by referring to existing technologies.

[0054] Those skilled in the art should recognize that the above embodiments are merely illustrative of this application and are not intended to limit this application. Any appropriate changes and variations made to the above embodiments within the essential spirit and scope of this application fall within the scope of protection of the claims of this application.

Claims

1. A method for preparing a core-shell molecular sieve composite material for treating oxygen-containing volatile organic compounds, characterized in that, The steps are as follows: a. Using ZSM-5 as the core, a ZIF-67 shell is grown on the surface of ZSM-5 by mechanochemical method to obtain the ZSM-5@ZIF-67 core-shell precursor; The specific steps are as follows: ZSM-5, cobalt nitrate hexahydrate, and 2-methylimidazole are added to a ball mill jar. Zirconia grinding balls are added to the ball mill jar. The mixture is then subjected to mechanical and chemical ball milling at a speed of 300-500 rpm on a planetary ball mill for 60-120 minutes. After the reaction is completed, the mixture is washed and dried to obtain the final product. The mass ratio of ZSM-5 to cobalt nitrate hexahydrate is 1 to 4:1; the mass ratio of cobalt nitrate hexahydrate to 2-methylimidazole is 1:

4. b. The ZSM-5@ZIF-67 core-shell precursor is heated in an air or oxygen atmosphere at a temperature of 350-550℃, so that the 2-methylimidazole in ZIF-67 is oxidized, decomposed and volatilized, and the metallic cobalt is oxidized to obtain a porous ZSM-5@Co3O4. c. Cu and Pd are introduced into ZSM-5@Co3O4 by a stepwise impregnation method, then reduced by NaBH4, and after drying and activation, ZSM-5@Pd-Cu / Co3O4 core-shell molecular sieve composite material is obtained.

2. The method for preparing a core-shell molecular sieve composite material for treating oxygen-containing volatile organic compounds according to claim 1, characterized in that: In step a, 10 zirconium oxide grinding balls with a diameter of 10 mm are added to the grinding jar.

3. The method for preparing a core-shell molecular sieve composite material for treating oxygen-containing volatile organic compounds according to claim 1, characterized in that: In step a, the mass ratio of ZSM-5 to cobalt nitrate hexahydrate is 3:1, and the mixture is mechanically and chemically ball-milled at 400 rpm on a planetary ball mill for 60 min.

4. The method for preparing a core-shell molecular sieve composite material for treating oxygen-containing volatile organic compounds according to claim 1, characterized in that: In step c, the specific steps for introducing Cu in the stepwise impregnation method are as follows: ZSM-5@Co3O4 is dispersed in deionized water, ultrasonically treated, and then copper nitrate trihydrate is added to the resulting dispersion and stirred at room temperature; the resulting solid is dried and calcined to obtain ZSM-5@Cu / Co3O4, wherein the copper loading mass is 1%.

5. The method for preparing a core-shell molecular sieve composite material for treating oxygen-containing volatile organic compounds according to claim 4, characterized in that: The specific steps for introducing Pd into ZSM-5@Cu / Co3O4 are as follows: ZSM-5@Cu / Co3O4 is dispersed in ethanol, NaPdCl4 aqueous solution is dispersed in the resulting dispersion, and then NaBH4 solution is slowly added dropwise to the resulting mixture. The mixture is stirred continuously at room temperature, centrifuged and filtered, the filter cake is washed, dried and activated to obtain ZSM-5@Pd-Cu / Co3O4, with a Pd loading mass of 0.1%.

6. The method for preparing a core-shell molecular sieve composite material for treating oxygen-containing volatile organic compounds according to claim 4, characterized in that: ZSM-5@Co3O4 was dispersed in 5 mL of deionized water, sonicated for 20 min, stirred at room temperature for 3–4 h, dried at 90–110 °C, calcined at 350–450 °C for 3–5 h.

7. The method for preparing a core-shell molecular sieve composite material for treating oxygen-containing volatile organic compounds according to claim 5, characterized in that: ZSM-5@Cu / Co3O4 was dispersed in 50 mL of ethanol and ultrasonically dispersed for 10–30 min. After stirring at room temperature for 3–4 h, the filter cake was centrifuged and filtered, washed with ethanol 3–5 times, vacuum dried at 50–70 °C for 12 h, and activated in a tube furnace at 400 °C under nitrogen atmosphere for 2 h to obtain ZSM-5@Pd-Cu / Co3O4.

8. The method for preparing a core-shell molecular sieve composite material for treating oxygen-containing volatile organic compounds according to claim 1, characterized in that: In step b, the heating temperature is 450℃, the heating rate is 3℃ / min, and the temperature is maintained for 4 hours.

9. A core-shell molecular sieve composite material for treating oxygen-containing volatile organic compounds, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 8.

10. A core-shell molecular sieve composite material for treating oxygen-containing volatile organic compounds according to claim 9, characterized in that: Its core adsorbs OVOCs at room temperature, while the outer shell completely oxidizes and decomposes OVOCs into carbon dioxide and water at a temperature of 220–240°C.

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