A carbon dioxide absorbent and a method of preparing the same

Abstract

This invention relates to the field of carbon dioxide capture technology and discloses a carbon dioxide absorbent and its preparation method, comprising the following weight components: 10-15 parts by weight of diethylenetriamine and 2-3 parts by weight of modified mesoporous silica. This invention achieves good CO2 capture capacity through the synergistic adsorption mechanism of diethylenetriamine and modified mesoporous silica. The cage-like structure of the modified mesoporous silica has a high specific surface area and ordered pores, providing sufficient loading sites and diffusion channels for diethylenetriamine. Simultaneously, the amine auxiliary agent (containing multiple primary and secondary amine groups) introduced during the modification process forms an "amine cluster" with the polyamine structure of diethylenetriamine, resulting in a better adsorption effect.

Description

Technical Field

[0001] This invention relates to the field of carbon dioxide capture technology, specifically to a carbon dioxide absorbent and its preparation method. Background Technology

[0002] In recent years, rapid industrialization in human society has led to the emission of large amounts of greenhouse gases such as carbon dioxide from the extensive use of fossil fuels. Excessive greenhouse gases contribute to the greenhouse effect, causing global warming, altering the ecological balance, and threatening human survival. Carbon dioxide capture and storage (CCS) technology is a key means of addressing global climate change, with important applications in industrial flue gas treatment, natural gas purification, and closed-space environmental control. Currently, carbon dioxide absorbents are mainly divided into two categories: liquid absorbents (such as alkanolamines) and solid absorbents (such as amine-functionalized mesoporous materials). However, existing technologies still have significant drawbacks: ordinary mesoporous silica has a disordered pore structure, limited specific surface area, and lacks functional groups on its surface, making it difficult to form stable bonds with amine groups, resulting in low amine loading and limiting the improvement of adsorption capacity. At the same time, non-cage-like pore structures are prone to collapse due to amine aggregation, further reducing material stability. Therefore, avoiding this phenomenon is the key to solving the problem. Summary of the Invention

[0003] (a) Technical problems to be solved

[0004] To address the shortcomings of existing technologies, this invention provides a carbon dioxide absorbent and its preparation method, which exhibits good absorption performance for carbon dioxide.

[0005] (II) Technical Solution

[0006] To achieve the above objectives, the present invention provides the following technical solution: a carbon dioxide absorbent comprising the following weight components: 10-15 parts by weight of diethylenetriamine and 2-3 parts by weight of modified mesoporous silica.

[0007] Furthermore, the method for preparing the modified mesoporous silica is as follows:

[0008] S1. Under a nitrogen atmosphere, add 5-6g glycidyl methacrylate, 4.3-5g itaconic acid, 0.10-0.11g triphenylphosphine, and 0.052-0.055g 4-methoxyphenol to the reactor. Place the reactor in an oil bath and heat the reaction for 1-1.5h. After the reaction is complete, vacuum distill the crude product at 85-90℃ for 0.8-1h to obtain alkenyl intermediate 1.

[0009] S2. Diethanolamine and alkenyl intermediate 1 are added to N,N-dimethylformamide solvent, stirred and mixed, and p-toluenesulfonic acid catalyst is added. The reaction is carried out at 85-90℃ for 6-7 hours. After the reaction is completed, the mixture is distilled under reduced pressure, washed, and dried to obtain intermediate 2.

[0010] S3. Add 4.5-6.3 mL of intermediate 2 to 40-50 mL of N,N-dimethylformamide solvent, stir and disperse, then add 18-25.2 mmol of mercaptoethylamine and 0.2-0.3 mmol of benzoin dimethyl ether photoinitiator, irradiate with 365 nm ultraviolet light at 20-30 °C, centrifuge after the irradiation, wash and dry to obtain the amine auxiliary agent;

[0011] S4. Add the amine additive to anhydrous ethanol, stir and dissolve at room temperature, then add cage-type mesoporous silica molecular sieve, continue stirring, and dry at 70-80℃ to obtain modified mesoporous silica.

[0012] Furthermore, the heating reaction temperature in S1 is 80-90℃.

[0013] Furthermore, the ratio of diethanolamine, alkenyl intermediate 1, N,N-dimethylformamide, and p-toluenesulfonic acid catalyst in S2 is 3-5 mmol: 6-10 mmol: 50-60 mL: 0.1-0.2 mmol.

[0014] Furthermore, the ultraviolet irradiation time in S3 is 2-2.5 hours.

[0015] Furthermore, the ratio of amine auxiliaries, anhydrous ethanol, and cage-type mesoporous silica molecular sieves in S4 is 3-5 mmol: 20-30 mL: 1-1.3 g.

[0016] Furthermore, the drying time in S4 is 20-24 hours.

[0017] Furthermore, the preparation method of the carbon dioxide absorbent is as follows: add diethylenetriamine and modified mesoporous silica to a stirrer, stir for 10-16 minutes, dry, and then press into tablets at 5-6 MPa to obtain the carbon dioxide absorbent.

[0018] (iii) Beneficial technical effects

[0019] In the above reaction process, the epoxy group in glycidyl methacrylate and the one-terminal carboxyl group in itaconic acid undergo a ring-opening reaction to generate a hydroxyl group, while simultaneously introducing an alkenyl group and a carboxyl group, thereby obtaining alkenyl intermediate 1; the dihydroxyl group in diethanolamine and the carboxyl group in alkenyl intermediate 1 undergo an esterification reaction (increasing the degree of substitution of alkenyl and hydroxyl groups), thereby obtaining intermediate 2; the alkenyl group in intermediate 2 and the mercapto group in mercaptoethylamine undergo a click reaction to introduce an amino group, thereby obtaining an amino auxiliary agent; the amino auxiliary agent and cage-type mesoporous silica are stirred and blended to obtain modified mesoporous silica.

[0020] This invention achieves good CO2 capture capacity through the synergistic adsorption mechanism of diethylenetriamine and modified mesoporous silica. The cage-like structure of the modified mesoporous silica has a high specific surface area and ordered channels, providing ample loading sites and diffusion channels for diethylenetriamine. Simultaneously, the amine auxiliary agent (containing multiple primary and secondary amine groups) introduced during the modification process forms an "amine cluster" with the polyamine structure of diethylenetriamine, resulting in a better adsorption effect. A click reaction is performed between the alkenyl group in intermediate 2 and the thiol group in mercaptoethylamine, introducing a large number of amino groups and increasing the degree of amino substitution, thus improving its carbon dioxide absorption effect. During the synthesis of modified mesoporous silica, the alkenyl group in intermediate 2 is chemically grafted and covalently bonded to the amine group in mercaptoethylamine, fixing the amine auxiliary agent within the cage-like channels. At the same time, the spatial confinement effect of the cage-like channels inhibits amine molecule aggregation, further enhancing its carbon dioxide absorption effect. Attached Figure Description

[0021] Figure 1 It is the reaction formula for intermediate 2. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] To better understand the above technical solutions, the following will provide a detailed description of the technical solutions in conjunction with the accompanying drawings and specific embodiments.

[0024] The preparation method of cage-type mesoporous silica molecular sieve is as follows: Referring to the literature "Preparation, Characterization and Adsorption Behavior of Polyethyleneimine Modified Cage-Type Mesoporous Molecular Sieves for Carbon Dioxide", 0.5 g of triblock copolymer (polyoxyethylene-polyoxypropylene-polyoxyethylene copolymer), 0.6 g of thiol, and 2.5 g of KCl were weighed into 30 mL of 2 mol / L HCl and stirred at 15 °C for 2 h. Then, 2.08 g of tetraethoxysilane was added, and stirring was continued for 24 h. The above reaction solution was transferred to a reaction vessel and reacted at 100 °C for 24 h. After cooling, the obtained reaction product was filtered, washed with water, and dried at room temperature. Finally, the organic template was removed by sintering at 550 °C for 6 h to obtain the cage-type mesoporous silica molecular sieve.

[0025] Example 1

[0026] S1. Under a nitrogen atmosphere, 5g of glycidyl methacrylate, 4.3g of itaconic acid, 0.10g of triphenylphosphine, and 0.052g of 4-methoxyphenol were added to the reactor. The reactor was placed in an oil bath and heated to 80℃ for 1h. After the reaction was completed, the crude product was vacuum distilled at 85℃ for 0.8h to obtain alkenyl intermediate 1.

[0027] S2. Add 3 mmol of diethanolamine and 6 mmol of alkenyl intermediate 1 to 50 mL of N,N-dimethylformamide solvent, stir and mix, and continue to add 0.1 mmol of p-toluenesulfonic acid catalyst. React at 85 °C for 6 h. After the reaction is completed, distill under reduced pressure, wash and dry to obtain intermediate 2.

[0028] S3. Add 4.5 mL of intermediate 2 to 40 mL of N,N-dimethylformamide solvent, stir and disperse, then add 18 mmol of mercaptoethylamine and 0.2 mmol of benzoin dimethyl ether photoinitiator, irradiate with 365 nm ultraviolet light at 20 °C for 2 h, centrifuge after the irradiation, wash and dry to obtain amine auxiliaries.

[0029] S4. Add 3 mmol of amine auxiliaries to 20 mL of anhydrous ethanol, stir and dissolve at room temperature, then add 1 g of cage-type mesoporous silica, continue stirring, and dry at 70 °C for 20 h to obtain modified mesoporous silica.

[0030] S5. Add 10 parts by weight of diethylenetriamine and 2 parts by weight of modified mesoporous silica to a stirrer, stir for 10 minutes, dry, and then press into tablets at 5 MPa to obtain carbon dioxide absorbent.

[0031] Example 2

[0032] S1. Under a nitrogen atmosphere, add 6g glycidyl methacrylate, 5g itaconic acid, 0.11g triphenylphosphine, and 0.055g 4-methoxyphenol to the reactor. Place the reactor in an oil bath and heat to 90℃ for 1.5h. After the reaction, vacuum distill the crude product at 90℃ for 1h to obtain alkenyl intermediate 1.

[0033] S2. Add 5 mmol of diethanolamine and 10 mmol of alkenyl intermediate 1 to 60 mL of N,N-dimethylformamide solvent, stir and mix, and continue to add 0.2 mmol of p-toluenesulfonic acid catalyst. React at 90 °C for 7 h. After the reaction is completed, distill under reduced pressure, wash and dry to obtain intermediate 2.

[0034] S3. Add 6.3 mL of intermediate 2 to 50 mL of N,N-dimethylformamide solvent, stir and disperse, then add 25.2 mmol of mercaptoethylamine and 0.3 mmol of benzoin dimethyl ether photoinitiator, irradiate with 365 nm ultraviolet light at 30 °C for 2.5 h, centrifuge, wash and dry to obtain amine auxiliaries;

[0035] S4. Add 5 mmol of amine auxiliaries to 30 mL of anhydrous ethanol, stir and dissolve at room temperature, then add 1.3 g of cage-type mesoporous silica, continue stirring, and dry at 80 °C for 24 h to obtain modified mesoporous silica.

[0036] S5. Add 15 parts by weight of diethylenetriamine and 3 parts by weight of modified mesoporous silica to a stirrer, stir for 16 minutes, dry, and then press into tablets at 6 MPa to obtain carbon dioxide absorbent.

[0037] Example 3

[0038] S1. Under a nitrogen atmosphere, 5.5 g glycidyl methacrylate, 4.7 g itaconic acid, 0.10 g triphenylphosphine, and 0.053 g 4-methoxyphenol were added to the reactor. The reactor was placed in an oil bath and heated to 85 °C for 1.2 h. After the reaction was completed, the crude product was vacuum distilled at 87 °C for 0.9 h to obtain alkenyl intermediate 1.

[0039] S2. Add 4 mmol of diethanolamine and 8 mmol of alkenyl intermediate 1 to 55 mL of N,N-dimethylformamide solvent, stir and mix, and continue to add 0.15 mmol of p-toluenesulfonic acid catalyst. React at 87 °C for 6.5 h. After the reaction is completed, distill under reduced pressure, wash and dry to obtain intermediate 2.

[0040] S3. Add 5.3 mL of intermediate 2 to 46 mL of N,N-dimethylformamide solvent, stir and disperse, then add 21.6 mmol of mercaptoethylamine and 0.25 mmol of benzoin dimethyl ether photoinitiator, irradiate with 365 nm ultraviolet light at 26 °C for 2.2 h, centrifuge, wash and dry to obtain amine auxiliaries;

[0041] S4. Add 4 mmol of amine auxiliaries to 25 mL of anhydrous ethanol, stir and dissolve at room temperature, then add 1.2 g of cage-type mesoporous silica, continue stirring, and dry at 75 °C for 22 h to obtain modified mesoporous silica.

[0042] S5. Add 13 parts by weight of diethylenetriamine and 2.5 parts by weight of modified mesoporous silica to a stirrer, stir for 13 minutes, dry, and then press into tablets at 5 MPa to obtain carbon dioxide absorbent.

[0043] Example 4

[0044] S1. Under a nitrogen atmosphere, 5g of glycidyl methacrylate, 4.3g of itaconic acid, 0.10g of triphenylphosphine, and 0.052g of 4-methoxyphenol were added to the reactor. The reactor was placed in an oil bath and heated to 80℃ for 1h. After the reaction was completed, the crude product was vacuum distilled at 85℃ for 0.8h to obtain alkenyl intermediate 1.

[0045] S2. Add 3 mmol of diethanolamine and 6 mmol of alkenyl intermediate 1 to 50 mL of N,N-dimethylformamide solvent, stir and mix, and continue to add 0.1 mmol of p-toluenesulfonic acid catalyst. React at 85 °C for 6 h. After the reaction is completed, distill under reduced pressure, wash and dry to obtain intermediate 2.

[0046] S3. Add 6.3 mL of intermediate 2 to 50 mL of N,N-dimethylformamide solvent, stir and disperse, then add 25.2 mmol of mercaptoethylamine and 0.3 mmol of benzoin dimethyl ether photoinitiator, irradiate with 365 nm ultraviolet light at 30 °C for 2.5 h, centrifuge, wash and dry to obtain amine auxiliaries;

[0047] S4. Add 4 mmol of amine auxiliaries to 25 mL of anhydrous ethanol, stir and dissolve at room temperature, then add 1.2 g of cage-type mesoporous silica, continue stirring, and dry at 75 °C for 22 h to obtain modified mesoporous silica.

[0048] S5. Add 13 parts by weight of diethylenetriamine and 2.5 parts by weight of modified mesoporous silica to a stirrer, stir for 13 minutes, dry, and then press into tablets at 5 MPa to obtain carbon dioxide absorbent.

[0049] Example 5

[0050] S1. Under a nitrogen atmosphere, add 6g glycidyl methacrylate, 5g itaconic acid, 0.11g triphenylphosphine, and 0.055g 4-methoxyphenol to the reactor. Place the reactor in an oil bath and heat to 90℃ for 1.5h. After the reaction, vacuum distill the crude product at 90℃ for 1h to obtain alkenyl intermediate 1.

[0051] S2. Add 5 mmol of diethanolamine and 10 mmol of alkenyl intermediate 1 to 60 mL of N,N-dimethylformamide solvent, stir and mix, and continue to add 0.2 mmol of p-toluenesulfonic acid catalyst. React at 90 °C for 7 h. After the reaction is completed, distill under reduced pressure, wash and dry to obtain intermediate 2.

[0052] S3. Add 5.3 mL of intermediate 2 to 46 mL of N,N-dimethylformamide solvent, stir and disperse, then add 21.6 mmol of mercaptoethylamine and 0.25 mmol of benzoin dimethyl ether photoinitiator, irradiate with 365 nm ultraviolet light at 26 °C for 2.2 h, centrifuge, wash and dry to obtain amine auxiliaries;

[0053] S4. Add 3 mmol of amine auxiliaries to 20 mL of anhydrous ethanol, stir and dissolve at room temperature, then add 1 g of cage-type mesoporous silica, continue stirring, and dry at 70 °C for 20 h to obtain modified mesoporous silica.

[0054] S5. Add 10 parts by weight of diethylenetriamine and 2 parts by weight of modified mesoporous silica to a stirrer, stir for 10 minutes, dry, and then press into tablets at 5 MPa to obtain carbon dioxide absorbent.

[0055] Comparative Example 1

[0056] The difference between this comparative example and Example 5 is that intermediate 2 is used instead of modified mesoporous silica.

[0057] Comparative Example 2

[0058] The difference between this comparative example and Example 5 is that cage-type mesoporous silica was used instead of modified mesoporous silica.

[0059] Performance testing

[0060] The performance of the carbon dioxide absorbents prepared in Examples 1-5 and Comparative Examples 1-2 was tested. The test method included the following steps: 20 mg of carbon dioxide absorbent supported by quartz wool was placed in the constant temperature heating zone of the fixed bed reactor. CO2 gas (50 mL / min) was introduced at room temperature to adsorb the absorbent. The test was performed by an online gas analyzer. After the carbon dioxide absorbent was saturated (adsorption time was 30 min), the amount of carbon dioxide adsorbed was calculated.

[0061] Table 1: Carbon dioxide adsorption test.

[0062]

[0063] As shown in Table 1, Examples 1-5 of the present invention have better adsorption effects than Comparative Examples 1-2.

[0064] The process of rapidly and in large quantities preparing high-performance carbon capture membranes by combining carbon dioxide adsorbents with membrane materials is as follows:

[0065] First, the adsorbent was selected according to the parameters in Examples 1-5;

[0066] Then, for the preparation of the membrane material, MOF-808 was selected as the inorganic filler because it has a pore size suitable for the CO2 molecule size (approximately 1.8 nm) and abundant unsaturated metal sites, which is beneficial for improving the CO2 permeation and selectivity of the membrane. To shorten the MOF synthesis cycle and obtain uniformly sized nanoparticles, microwave heating was used instead of traditional hydrothermal synthesis, utilizing the rapid and uniform heating characteristics of microwaves to complete MOF crystal growth in a short time. Simultaneously, a silane coupling agent (KH-560) and polyethyleneimine (PEI) were introduced to modify the MOF surface, aiming to improve the dispersibility of MOF particles in the polymer and increase their chemical affinity for CO2.

[0067] Microwave Synthesis of MOF-808: MOF-808 nanoparticles were rapidly synthesized using a microwave-assisted method. The specific steps were as follows: A zirconium source (e.g., ZrOCl2·8H2O) was dissolved in a mixed solvent of N,N-dimethylformamide (DMF) and formic acid (volume ratio approximately 1:1). The organic ligand, trimesic acid (H3BTC), was added at a stoichiometric ratio (Zr:tricarboxylic acid ≈ 3:1). The mixture was stirred at room temperature for 10–20 minutes to form a clear and transparent precursor solution. The solution was transferred to a polytetrafluoroethylene-lined microwave reactor (filling degree not exceeding 60%), sealed, and placed in the microwave reactor. Heating was performed using a 2.45 GHz single-mode microwave. The power-time program was set as follows: the temperature was raised to 120°C within 2 minutes at 600 W, then held at 120°C for 10 minutes at 400 W, after which the microwave was turned off and allowed to cool naturally to below 60°C. The total reaction time was approximately 25 minutes. The resulting white precipitate was centrifuged and washed twice each with DMF and anhydrous ethanol to remove unreacted ligands and zirconium salts. It was then vacuum-dried at 80 °C for 4 hours to obtain MOF-808 nanoparticles. The product was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) to confirm its crystal structure and particle size distribution. The microwave-synthesized MOF-808 exhibits a typical crystal structure with uniform particle size of approximately 50–80 nm, significantly reducing the preparation time compared to the traditional hydrothermal method (which requires more than 24 hours).

[0068] Rapid Synthesis of MOF-808 Nanoparticles Using Microwave-Assisted Method

[0069] Surface Functionalization of MOF-808: To improve the dispersibility of MOF in polymers and enhance its CO2 adsorption capacity, MOF-808 underwent surface functionalization modification. The aforementioned MOF-808 nanoparticles were dispersed in deionized water, and silane coupling agent KH-560 (γ-glycidoxypropyltrimethoxysilane) and polyethyleneimine (PEI) were added, with KH-560 concentrations ranging from 4.17 to 13.6 g / L and PEI concentrations ranging from 0.91 to 1.67 g / L. The reaction was stirred at 80°C for 12 hours, allowing the silane coupling agent to hydrolyze and bind to the hydroxyl groups on the MOF surface. Simultaneously, PEI adhered to the MOF surface through electrostatic interactions or covalent bonds. After the reaction, the particles were centrifuged and washed several times with deionized water to remove unreacted reagents, and then vacuum dried at 80°C. The modified MOF-808 surface, grafted with amino and epoxy groups, not only improves its compatibility with the polymer matrix but also increases the number of chemical affinity sites for CO2, which is beneficial for improving the CO2 selectivity of the membrane.

[0070] Coating solution preparation and composite membrane preparation: Surface-functionalized MOF-808 and PEI were mixed at a mass ratio of 1:5, and an appropriate amount of deionized water was added to prepare a coating solution with a solid content of 0.25%–1.0% (mass fraction). The low solid content formulation helps form a uniform, ultra-thin liquid film during ultrasonic spraying and reduces material waste. During spraying, parameters such as nozzle-substrate distance, spraying speed, and solution flow rate were controlled to obtain a wet film with a thickness of approximately 70–100 μm. After spraying, the film was dried at room temperature for 2 hours to allow the solvent to evaporate and form a dense MOF / PEI composite selective layer. The resulting composite membrane is the carbon capture membrane.

[0071] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0072] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0073] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments.

Claims

1. A carbon dioxide absorbent, characterized in that, It includes the following components by weight: 10-15 parts by weight of diethylenetriamine and 2-3 parts by weight of modified mesoporous silica; The method for preparing the modified mesoporous silica is as follows: S1. Under a nitrogen atmosphere, add 5-6g glycidyl methacrylate, 4.3-5g itaconic acid, 0.10-0.11g triphenylphosphine, and 0.052-0.055g 4-methoxyphenol to the reactor. Place the reactor in an oil bath and heat the reaction for 1-1.5h. After the reaction is complete, vacuum distill the crude product at 85-90℃ for 0.8-1h to obtain alkenyl intermediate 1. S2. Diethanolamine and alkenyl intermediate 1 are added to N,N-dimethylformamide solvent, stirred and mixed, and p-toluenesulfonic acid catalyst is added. The reaction is carried out at 85-90℃ for 6-7 hours. After the reaction is completed, the mixture is distilled under reduced pressure, washed, and dried to obtain intermediate 2. S3. Add 4.5-6.3 mL of intermediate 2 to 40-50 mL of N,N-dimethylformamide solvent, stir and disperse, then add 18-25.2 mmol of mercaptoethylamine and 0.2-0.3 mmol of benzoin dimethyl ether photoinitiator, irradiate with 365 nm ultraviolet light at 20-30 °C, centrifuge after the irradiation, wash and dry to obtain the amine auxiliary agent; S4. Add the amine additive to anhydrous ethanol, stir and dissolve at room temperature, then add cage-type mesoporous silica molecular sieve, continue stirring, and dry at 70-80℃ to obtain modified mesoporous silica. The ratio of amine auxiliaries, anhydrous ethanol, and cage-type mesoporous silica molecular sieves in S4 is 3-5 mmol: 20-30 mL: 1-1.3 g.

2. The carbon dioxide absorbent according to claim 1, characterized in that, The heating reaction temperature in S1 is 80-90℃.

3. The carbon dioxide absorbent according to claim 1, characterized in that, The ratio of diethanolamine, alkenyl intermediate 1, N,N-dimethylformamide, and p-toluenesulfonic acid catalyst in S2 is 3-5 mmol: 6-10 mmol: 50-60 mL: 0.1-0.2 mmol.

4. The carbon dioxide absorbent according to claim 1, characterized in that, The ultraviolet light irradiation time in S3 is 2-2.5h.

5. The carbon dioxide absorbent according to claim 1, characterized in that, The drying time in S4 is 20-24 hours.

6. A method for preparing a carbon dioxide absorbent as described in any one of claims 1-5, characterized in that, The preparation method of the carbon dioxide absorbent is as follows: add diethylenetriamine and modified mesoporous silica to a stirrer, stir for 10-16 minutes, dry, and then press into tablets at 5-6 MPa to obtain the carbon dioxide absorbent.

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