Carbon-coated ZnO / CoO composite adsorbent and preparation method thereof

Abstract

The invention discloses a carbon-coated ZnO / CoO composite adsorbent and a preparation method thereof, the method comprises chloromethylation modification, amination modification, ZIFs in-situ growth and preparation of the carbon-coated ZnO / CoO composite adsorbent, and the invention relates to the technical field of adsorption materials. According to the invention, styrene resin microspheres are subjected to chloromethylation to introduce active functional groups, and amination is carried out to generate amino groups (-NH), so that active sites coordinated with metal ions are provided, and in-situ growth of ZIF-8 and ZIF-67 on the surface of resin is promoted. The crystal morphology and distribution are effectively controlled by optimizing the molar ratio of the zinc salt and the cobalt salt to the ligand and selecting the solvent and the nucleating agent. And finally, after the material is subjected to high-temperature calcination, the resin and the ZIFs are subjected to synergistic pyrolysis to form a structure that the nano oxide is uniformly embedded into the porous carbon skeleton, so that the stability, the active site density and the gas diffusion efficiency of the adsorbent are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of adsorption materials, and in particular to a carbon@ZnO / CoO composite adsorbent and a preparation method thereof. Background Art

[0002] In the high-process semiconductor industry, chip manufacturing requires extremely high environmental purity. Any trace of contamination can lead to chip performance degradation or even complete failure. Among the many gaseous molecular contaminants (AMCs), ammonia (NH3) has a particularly significant impact on semiconductor manufacturing processes. Due to its strong interaction with the silicon wafer surface, it can significantly reduce chip yield.

[0003] Activated carbon is widely used to remove ammonia and other organic pollutants due to its high specific surface area and porous structure. It mainly captures gas molecules by physical adsorption. For example, the preparation method of ammonia-protective impregnated carbon described in patent CN117942935A significantly improves its adsorption capacity for ammonia by using acid-modified and metal-impregnated activated carbon. However, activated carbon adsorbents have problems such as limited adsorption capacity and unadjustable structural properties, and their adsorption performance for low-concentration NH3 is poor. Another effective means of removing NH3 by cation exchange resin is to use cations and NH4 + Ion exchange occurs, thereby removing ammonia. However, compared to activated carbon, cation exchange resins have lower specific surface area and porosity, resulting in a very limited adsorption capacity for NH3. To address this issue, patent CN105174243B uses a saponification-free emulsion polymerization method to prepare polystyrene microspheres. This increases the resin's specific surface area to a certain extent, but it still struggles to effectively capture ammonia in low-concentration environments. Metal-organic frameworks (MOFs) are a new class of porous materials that show great potential in gas adsorption due to their adjustable pore size and high specific surface area. For example, patent CN113583251A discloses a copper-based MOF adsorbent for NH3 gas removal. By introducing -SO3H, it forms a chemical bond with NH3, achieving efficient filtration. However, current MOF materials have not yet overcome their poor chemical stability and may experience performance degradation over long-term use.

[0004] Therefore, it is necessary to develop an NH3 adsorbent with high adsorption capacity, adjustable structure and function, and stable chemical properties to achieve efficient removal of low-concentration NH3. Summary of the Invention

[0005] To address the shortcomings of the existing technology, the present invention provides a carbon@ZnO / CoO composite adsorbent and its preparation method. By chloromethylating styrene resin microspheres to introduce active functional groups and then aminating them to form amino groups (-NH2), these microspheres provide active sites for metal ion coordination and promote the in situ growth of ZIF-8 and ZIF-67 on the resin surface. By optimizing the molar ratio of zinc and cobalt salts to ligands, as well as the choice of solvent and nucleating agent, the crystal morphology and distribution are effectively controlled. After high-temperature calcination, the resin and ZIFs synergistically pyrolyze to form a structure in which the nano-oxides are uniformly embedded in a porous carbon framework, significantly improving the adsorbent's stability, active site density, and gas diffusion efficiency. Furthermore, the nano-ZnO and CoO particles act as Lewis acid sites, strongly interacting with alkaline gases and significantly enhancing adsorption performance.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0007] A method for preparing a carbon@ZnO / CoO composite adsorbent comprises the following steps:

[0008] Step 1, chloromethylation modification:

[0009] Step 1.1: Weigh 2-5 g of zinc chloride in dichloromethane, add 5-20 ml of chloromethyl methyl ether, and stir to form a uniform solution A;

[0010] Step 1.2: Add 30-100 g of styrene resin microspheres to Solution A and react with magnetic stirring at 30-100°C for 2-12 h.

[0011] Step 1.3: After the reaction is completed, pour the reaction solution into ice water, cool it quickly, and wash it alternately with dichloromethane and deionized water several times until the washing solution is neutral;

[0012] Step 1.4: After washing, the resin is dried to constant weight to obtain a styrene resin with chloromethyl groups, namely PS-CH2Cl.

[0013] Step 2, amination modification:

[0014] Step 2.1: Disperse 10-50 ml of ethylenediamine in 50-200 ml of methanol to obtain a mixed solution B, i.e., an amination reaction solution;

[0015] Step 2.2: Add the PS-CH2Cl prepared in step 1 to solution B and stir at 60-70°C for 2-24 hours.

[0016] Step 2.3: After the reaction of the chloromethyl groups in the resin with ethylenediamine is complete, the resin is washed with deionized water to remove unreacted reagents and by-products. Finally, the resin is dried to a constant weight to obtain a functionalized resin with amino groups, namely PS-NH2.

[0017] Step 3: In situ growth of ZIFs:

[0018] Step 3.1: Weigh 2–10 g of each zinc salt and cobalt salt and dissolve them in 50–250 mL of organic solvent under magnetic stirring to obtain metal salt solution C.

[0019] Step 3.2: Weigh 5–40 g of 2-methylimidazole and dissolve it in 50–100 mL of an organic solvent under magnetic stirring to obtain ligand solution D.

[0020] Step 3.3: Weigh 30-100 g of PS-NH2 and disperse it evenly in the metal salt solution C under magnetic stirring to obtain dispersion E;

[0021] Step 3.4: Add ligand solution D to dispersion E, and add 0-5 g of nucleating agent. React at 60-120 °C and 200-800 rpm for 2-12 h. After washing and drying, obtain the PS-NH2@ZIF-8 / ZIF-67 complex.

[0022] Step 4, preparation of carbon@ZnO / CoO composite adsorbent:

[0023] Step 4.1: The PS-NH2@ZIF-8 / ZIF-67 composite prepared above was weighed and ground in a mortar. The resulting powder was transferred to a magnetic boat and subjected to high-temperature heat treatment in a tube furnace.

[0024] Step 4.2: Under the protection of N2, the temperature was raised to 200-250°C at a rate of 5-7.5°C / min and maintained at this temperature for 1-1.5 hours; then the temperature was raised to 300-400°C at a rate of 7.5-10°C / min and maintained at this temperature for 2-4 hours; then the temperature was raised to 500-600°C at a rate of 10-15°C / min and maintained at this temperature for 4-6 hours. Finally, the temperature was naturally cooled to room temperature to prepare a carbon@ZnO / CoO composite adsorbent.

[0025] Preferably, the zinc salt in step 3.1 is one of Zn(NO3)2·6H2O, ZnSO4·7H2O and Zn(CH3COO)2·2H2O.

[0026] Preferably, the cobalt salt in step 3.1 is one of Co(NO3)2·6H2O, CoSO4·7H2O and CoCl2·6H2O.

[0027] Preferably, the organic solvent in step 3.1 and step 3.2 is one of deionized water, methanol, ethanol, DMAc and DMF.

[0028] Preferably, the nucleating agent in step 3.4 is one or more of sodium hydroxide, polyvinyl alcohol, sodium dodecylbenzenesulfonate, and polyvinyl pyrrolidone.

[0029] The present invention also provides a carbon@ZnO / CoO composite adsorbent, which is prepared by the above-mentioned preparation method of the carbon@ZnO / CoO composite adsorbent.

[0030] Beneficial effects

[0031] The present invention provides a carbon@ZnO / CoO composite adsorbent and a preparation method thereof. Compared with the prior art, it has the following advantages:

[0032] (1) The carbon@ZnO / CoO composite adsorbent prepared by the present invention has high adsorption efficiency. The MOF-derived porous carbon material inherits the advantages of large surface area and high porosity of MOF, providing a large number of active sites, so that ammonia molecules can fully contact with the Lewis acid sites constructed by nano-ZnO and CoO particles, thereby improving the adsorption efficiency.

[0033] (2) The carbon@ZnO / CoO composite adsorbent prepared by the present invention has good chemical stability. The MOF-derived material improves the stability of the parent MOF and has higher tolerance and recyclability under harsh reaction conditions, so that the adsorbent maintains its performance during long-term use and reduces the frequency of replacement.

[0034] (3) The carbon@ZnO / CoO composite adsorbent prepared by the present invention has good structural stability. MOF and resin are co-pyrolyzed to produce a rich multi-level pore structure, which provides excellent diffusion channels for gas molecules, thereby significantly improving the gas adsorption and separation performance of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 1 is the XRD spectrum of the carbon@ZnO / CoO composite adsorbent prepared in Examples 1-3 of the present invention. DETAILED DESCRIPTION

[0036] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0037] Example 1:

[0038] A method for preparing a carbon@ZnO / CoO composite adsorbent, comprising:

[0039] Step 1, chloromethylation modification:

[0040] Step 1.1: Weigh 4.5 g of zinc chloride in dichloromethane and add 18 ml of chloromethyl methyl ether. Stir to form a uniform solution A.

[0041] Step 1.2: Add 80 g of polystyrene resin microspheres (PS) to solution A and react at 60°C with magnetic stirring for 3 h.

[0042] Step 1.3: After the reaction is completed, pour the reaction solution into ice water, cool it quickly, and wash it alternately with dichloromethane and deionized water several times until the washing solution is neutral;

[0043] Step 1.4: After washing, the resin is dried to constant weight to obtain a styrene resin with chloromethyl (-CH2Cl) groups, namely PS-CH2Cl.

[0044] Step 2, amination modification:

[0045] Step 2.1: Disperse 40 ml of ethylenediamine in 160 ml of methanol to obtain a mixed solution B, i.e., an amination reaction solution;

[0046] Step 2.2: Add the PS-CH2Cl prepared in step 1 to solution B and stir at 60°C for 8 h;

[0047] Step 2.3: After the reaction of the chloromethyl groups in the resin with ethylenediamine is complete, the resin is washed with deionized water to remove unreacted reagents and by-products. Finally, the resin is dried to a constant weight to obtain a functionalized resin with amino groups, namely PS-NH2.

[0048] Step 3: In situ growth of ZIFs:

[0049] Step 3.1: Weigh 2.98 g of Zn(NO3)2·6H2O and 8.73 g of Co(NO3)2·6H2O and dissolve them in 200 mL of deionized water under magnetic stirring to obtain metal salt solution C.

[0050] Step 3.2: Weigh 26.24 g of 2-methylimidazole and dissolve it in 200 mL of deionized water under magnetic stirring to obtain ligand solution D.

[0051] Step 3.3: Weigh 80 g of PS-NH2 and disperse it evenly in the above metal salt solution C under magnetic stirring to obtain dispersion E;

[0052] Step 3.4: Add ligand solution D to dispersion E, and add 0.5 g of sodium hydroxide. React at 80°C and 500 rpm for 8 h. After washing and drying, obtain the PS-NH2@ZIF-8 / ZIF-67 complex.

[0053] Step 4, preparation of carbon@ZnO / CoO composite adsorbent:

[0054] Step 4.1: The PS-NH2@ZIF-8 / ZIF-67 composite prepared above was weighed and ground in a mortar. The resulting powder was transferred to a magnetic boat and subjected to high-temperature heat treatment in a tube furnace.

[0055] Step 4.2: Under the protection of N2, the temperature was raised to 220°C at a rate of 5°C / min and maintained at this temperature for 1.2 hours; then, the temperature was raised to 350°C at a rate of 7.5°C / min and maintained at this temperature for 2 hours; then, the temperature was raised to 550°C at a rate of 10°C / min and maintained at this temperature for 4 hours, and finally, the temperature was naturally cooled to room temperature to prepare a carbon@ZnO / CoO composite adsorbent.

[0056] Example 2:

[0057] The masses of Zn(NO3)2·6H2O and Co(NO3)2·6H2O in step 3.1 of Example 1 were adjusted to 5.96 g and 5.82 g, respectively, and the rest of the method remained unchanged to prepare a carbon@ZnO / CoO composite adsorbent.

[0058] Example 3:

[0059] The masses of Zn(NO3)2·6H2O and Co(NO3)2·6H2O in step 3.1 of Example 1 were adjusted to 8.94 g and 2.91 g, respectively, and the rest of the method remained unchanged to prepare a carbon@ZnO / CoO composite adsorbent.

[0060] Structural characterization and performance testing

[0061] 1.XRD test

[0062] The carbon@ZnO / CoO composite adsorbent prepared in Examples 1-3 was subjected to XRD test, and the test results are as follows: Figure 1As shown in the figure, the main characteristic peaks of zinc oxide (ZnO) are located at 31.7°, 34.4°, and 36.2°, corresponding to the (100), (002), and (101) crystal planes, respectively, while the main characteristic peaks of cobalt oxide (CoO) are located at 47.5°, 56.6°, and 62.9°, corresponding to the (200), (311), and (222) crystal planes, respectively. The intensities of these characteristic peaks vary under different Zn:Co molar ratios: when Zn:Co=1:3, the peak intensity of CoO is the highest and that of ZnO is the lowest; when Zn:Co=1:1, the peak intensities of ZnO and CoO are close, showing a uniform distribution of the bimetallic; when Zn:Co=3:1, the peak intensity of ZnO is the highest and that of CoO is the weakest. This trend reflects the change in the relative ratio of the two metal oxides and indicates that by adjusting the Zn:Co ratio, the microstructure and properties of the composite material can be precisely controlled.

[0063] 2.BET and NH3 adsorption performance test

[0064] (1) Analytical testing: The BET surface area and pore structure of the materials were tested using a Belsorp MAXⅡ analyzer with N2 adsorption and desorption at -195°C. The total surface area was determined using the Brunauer-Emmett-Taylor (BET) equation.

[0065] (2) NH3 adsorption performance test: The material was subjected to gas (NH3) adsorption test using the UTEST static adsorption device. Initial efficiency: Control the test air volume (12 L / min), test resistance (100 Pa), and test concentration (600 ppb); Dirt holding capacity: Control the test air volume (15 L / min), test resistance (100 Pa), and test concentration (10 ppm).

[0066] The test results are shown in Table 1.

[0067] Table 1 BET and NH3 adsorption performance test results of samples prepared in Examples 1-3

[0068] sample <![CDATA[BET(m 2 / g)]]> Initial efficiency (%) Mass adsorption ratio (%) Example 1 1378 94.2 3.36 Example 2 1344 92.8 3.01 Example 3 1273 91.7 2.93

[0069] Meanwhile, the contents not described in detail in this specification belong to the prior art known to those skilled in the art.

[0070] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0071] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a carbon@ZnO / CoO composite adsorbent, characterized in that: The following steps are involved: Step 1, chloromethylation modification: Step 1.1: Weigh 2-5 g of zinc chloride in dichloromethane, add 5-20 ml of chloromethyl methyl ether, and stir to form a uniform solution A; Step 1.2: Add 30-100 g of styrene resin microspheres to Solution A and react with magnetic stirring at 30-100°C for 2-12 h. Step 1.3: After the reaction is completed, pour the reaction solution into ice water, cool it quickly, and wash it alternately with dichloromethane and deionized water several times until the washing solution is neutral; Step 1.4: After washing, the resin is dried to constant weight to obtain a styrene resin with chloromethyl groups, namely PS-CH2Cl. Step 2, amination modification: Step 2.1: Disperse 10-50 ml of ethylenediamine in 50-200 ml of methanol to obtain a mixed solution B, i.e., an amination reaction solution; Step 2.2: Add the PS-CH2Cl prepared in step 1 to solution B and stir at 60-70°C for 2-24 hours. Step 2.3: After the reaction of the chloromethyl groups in the resin with ethylenediamine is complete, the resin is washed with deionized water to remove unreacted reagents and by-products. Finally, the resin is dried to a constant weight to obtain a functionalized resin with amino groups, namely PS-NH2. Step 3: In situ growth of ZIFs: Step 3.1: Weigh 2–10 g of each zinc salt and cobalt salt and dissolve them in 50–250 mL of organic solvent under magnetic stirring to obtain metal salt solution C. Step 3.2: Weigh 5–40 g of 2-methylimidazole and dissolve it in 50–100 mL of an organic solvent under magnetic stirring to obtain ligand solution D. Step 3.3: Weigh 30-100 g of PS-NH2 and disperse it evenly in the metal salt solution C under magnetic stirring to obtain dispersion E; Step 3.4: Add ligand solution D to dispersion E, and add 0-5 g of nucleating agent. React at 60-120 °C and 200-800 rpm for 2-12 h. After washing and drying, obtain the PS-NH2@ZIF-8 / ZIF-67 complex. Step 4, preparation of carbon@ZnO / CoO composite adsorbent: Step 4.1: The PS-NH2@ZIF-8 / ZIF-67 composite prepared above was weighed and ground in a mortar. The resulting powder was transferred to a magnetic boat and subjected to high-temperature heat treatment in a tube furnace. Step 4.2: Under the protection of N2, the temperature was raised to 200-250°C at a rate of 5-7.5°C / min and maintained at this temperature for 1-1.5 hours; then the temperature was raised to 300-400°C at a rate of 7.5-10°C / min and maintained at this temperature for 2-4 hours; then the temperature was raised to 500-600°C at a rate of 10-15°C / min and maintained at this temperature for 4-6 hours. Finally, the temperature was naturally cooled to room temperature to prepare a carbon@ZnO / CoO composite adsorbent.

2. The method for preparing a carbon@ZnO / CoO composite adsorbent according to claim 1, characterized in that: The zinc salt in step 3.1 is one of Zn(NO3)2·6H2O, ZnSO4·7H2O and Zn(CH3COO)2·2H2O.

3. The method for preparing a carbon@ZnO / CoO composite adsorbent according to claim 1, characterized in that: The cobalt salt in step 3.1 is one of Co(NO3)2·6H2O, CoSO4·7H2O and CoCl2·6H2O.

4. The method for preparing a carbon@ZnO / CoO composite adsorbent according to claim 1, characterized in that: The organic solvent in step 3.1 and step 3.2 is one of deionized water, methanol, ethanol, DMAc and DMF.

5. The method for preparing a carbon@ZnO / CoO composite adsorbent according to claim 1, characterized in that: In step 3.4, the nucleating agent is one or more of sodium hydroxide, polyvinyl alcohol, sodium dodecylbenzenesulfonate, and polyvinyl pyrrolidone.

6. A carbon@ZnO / CoO composite adsorbent, characterized in that: The carbon@ZnO / CoO composite adsorbent is prepared by the preparation method of any one of claims 1 to 5.

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