Alkali-doped carbon-based sorbents, methods of making, and uses thereof

Abstract

The application provides an alkali metal doped carbon-based adsorbent, a preparation method and application thereof, and the preparation method comprises the following steps: S1, adding deionized water, methanol, an alkali metal ion precursor and cyclodextrin into a ball milling tank for ball milling mixing, and after washing, an alkali metal-based cyclodextrin organic framework material is obtained; S2, the alkali metal-based cyclodextrin organic framework material is subjected to high-temperature heat treatment under an inert atmosphere or vacuum condition, and an alkali metal doped carbon-based adsorbent is obtained. The alkali metal ion precursor and the cyclodextrin are self-assembled through coordination to form the alkali metal-based cyclodextrin organic framework material with a regular porous structure, and the atomically dispersed alkali metal ions are used as an efficient in-situ activation agent and alkaline adsorption site, and then the alkali metal doped carbon-based adsorbent with highly dispersed adsorption sites and greatly improved texture parameters is obtained, and the alkali metal doped carbon-based adsorbent has the advantages of large adsorption capacity, fast adsorption rate, easy regeneration and high cycle stability for low-concentration carbon dioxide.

Description

Technical Field

[0001] This invention belongs to the field of carbon dioxide adsorption and capture technology, and in particular relates to an alkali metal-doped carbon-based adsorbent, its preparation method and its application. Background Technology

[0002] With the intensification of the global greenhouse effect, carbon emission reduction has become a global consensus. Carbon dioxide capture, utilization, and storage (CCUS) has become a key technological approach for large-scale carbon emission reduction and the low-carbon utilization of fossil energy. However, the cost of carbon dioxide capture accounts for about 70% of the entire CCUS process, severely restricting the large-scale application of CCUS. Therefore, low-cost carbon dioxide capture is a key bottleneck for the future promotion and application of CCUS technology. Compared with the currently used "first-generation" organic amine solution absorption method in industry, the solid adsorption method based on porous materials has the potential to significantly reduce capture costs due to its advantages such as long adsorbent life, low regeneration energy consumption, and simple process operation, becoming the "second-generation" carbon capture technology. The key lies in the development of highly efficient adsorbents.

[0003] Porous carbon materials possess immense application potential in carbon dioxide adsorption and separation due to their advantages such as well-developed pores, large surface area, easily modifiable pores, high thermal stability, acid and alkali resistance, low cost, and abundant sources. However, carbon materials suffer from low adsorption performance and selectivity for carbon dioxide due to their non-polar surface and limited adsorption sites. Introducing alkaline alkali metal species into carbon materials can effectively improve surface polarity and increase the number of alkaline adsorption sites, thereby significantly enhancing the adsorption performance of porous carbon materials for low-concentration carbon dioxide. Current methods for preparing alkali metal-modified carbon materials often employ impregnation, where alkali metal-containing substances are introduced into the pores of porous carbon materials. This method easily leads to uneven dispersion of alkali metal species and readily clogs the pore structure, causing a sharp decline in texture parameters such as pore volume and surface area, which is detrimental to rapid gas diffusion and improved adsorption performance during adsorption and desorption. Furthermore, the preparation of existing alkali metal-modified carbon materials uses large amounts of alkali metal species, such as potassium hydroxide, sodium hydroxide, and potassium carbonate, resulting in low alkali metal utilization, poor economic efficiency, and significant environmental pollution problems.

[0004] Therefore, there is a need to provide an improved technical solution that addresses the shortcomings of the existing technology. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide an alkali metal-doped carbon-based adsorbent, its preparation method and its application, to solve the problems of cumbersome preparation methods, uneven species dispersion, deterioration of texture parameters and large amount of alkali metal used in the preparation of alkali metal-modified carbon materials in the prior art.

[0006] To achieve the above and other related objectives, the present invention provides a method for preparing an alkali metal-doped carbon-based adsorbent, the method comprising the following steps:

[0007] S1. Deionized water, methanol, alkali metal ion precursor and cyclodextrin are added to a ball mill jar for ball milling and mixing. After washing, alkali metal-based cyclodextrin organic framework material is obtained.

[0008] S2. The alkali metal-based cyclodextrin organic framework material is subjected to high-temperature heat treatment under an inert atmosphere or vacuum to obtain an alkali metal-doped carbon-based adsorbent.

[0009] Preferably, the alkali metal ion precursor in step S1 is a salt or alkali containing alkali metal ions; wherein the alkali metal ions include one or a combination of lithium, sodium, potassium, rubidium, and cesium.

[0010] Preferably, the cyclodextrin in step S1 is one or a combination of α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin.

[0011] Preferably, the alkali metal ion precursor in step S1 is a salt or alkali containing potassium metal ions.

[0012] Preferably, the cyclodextrin in step S1 is γ-cyclodextrin.

[0013] Preferably, the molar ratio of deionized water, methanol, alkali metal ion precursor and cyclodextrin in step S1 is (0.05-2.0):(0.05-2.0):(4-10):1.

[0014] Preferably, the ball milling temperature in step S1 is 5 to 50°C.

[0015] Preferably, the ball milling time in step S1 is 4 to 168 hours.

[0016] Preferably, the ball milling speed in step S1 is 100 to 1000 rpm.

[0017] Preferably, the inert atmosphere in step S1 is one or a combination of nitrogen, argon, and helium.

[0018] Preferably, the temperature of the high-temperature heat treatment in step S1 is 500-1000°C, and the time of the high-temperature heat treatment is 0.5-5 hours.

[0019] Preferably, the heating rate of the high-temperature heat treatment in step S1 is 1 to 10 °C / min.

[0020] The present invention also provides an alkali metal-doped carbon-based adsorbent prepared according to the above-described method for preparing alkali metal-doped carbon-based adsorbents.

[0021] The present invention also provides an application of an alkali metal-doped carbon-based adsorbent in the field of carbon dioxide adsorption and capture, wherein the alkali metal-doped carbon-based adsorbent is prepared by the above-described preparation method.

[0022] As described above, the alkali metal-doped carbon-based adsorbent, its preparation method, and its application of the present invention have the following beneficial effects:

[0023] This invention addresses the shortcomings of existing porous carbon materials in adsorbing low-pressure, low-concentration carbon dioxide, as well as the cumbersome preparation methods, uneven species dispersion, deteriorated texture parameters, and large amounts of alkali metal precursors required in the preparation of existing alkali metal-modified carbon materials. The invention utilizes alkali metal ion precursors and cyclodextrin to form a well-structured porous alkali metal-based cyclodextrin organic framework material through coordination self-assembly. Using this framework as a precursor, the atomically dispersed alkali metal ions within the framework act as highly efficient in-situ activators and alkaline adsorption sites, resulting in an alkali metal-doped carbon-based adsorbent with highly dispersed adsorption sites and significantly improved texture parameters. This adsorbent exhibits advantages such as large adsorption capacity, fast adsorption rate, easy regeneration, and high cycle stability for low-concentration carbon dioxide, showing promising application prospects in the capture of low-concentration carbon dioxide in flue gas. Furthermore, the preparation method of this alkali metal-doped carbon-based adsorbent is simple, easy to scale up, and inexpensive, possessing significant potential for widespread application. Attached Figure Description

[0024] Figure 1 The image shown is a SEM image of the potassium-doped carbon-based adsorbent prepared in Example 2 of this invention.

[0025] Figure 2 The image shown is a SEM image of the potassium-doped carbon-based adsorbent prepared in Example 5 of this invention.

[0026] Figure 3 The image shown is a SEM image of the potassium-doped carbon-based adsorbent prepared in Example 8 of this invention.

[0027] Figure 4 The image shown is a SEM image of the potassium-doped carbon-based adsorbent prepared in Example 11 of this invention. Detailed Implementation

[0028] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0029] To address the shortcomings of existing porous carbon materials in adsorbing low-pressure, low-concentration carbon dioxide, as well as the cumbersome preparation methods, uneven species dispersion, deteriorated texture parameters, and large amounts of alkali metal precursors involved in the preparation of alkali metal-modified carbon materials, this paper proposes an alkali metal-based cyclodextrin organic framework material with a regular porous structure as a precursor. The atomically dispersed alkali metal ions within this framework material serve as highly efficient in-situ activators and alkaline adsorption sites, resulting in an alkali metal-doped carbon-based adsorbent with highly dispersed adsorption sites and significantly improved texture parameters. This adsorbent exhibits advantages such as large adsorption capacity, fast adsorption rate, easy regeneration, and high cycle stability for low-concentration carbon dioxide.

[0030] This invention provides a method for preparing an alkali metal-doped carbon-based adsorbent, the method comprising the following steps:

[0031] S1. Deionized water, methanol, alkali metal ion precursor and cyclodextrin are added to a ball mill jar for ball milling and mixing. After washing, alkali metal-based cyclodextrin organic framework material is obtained.

[0032] S2. The alkali metal-based cyclodextrin organic framework material is subjected to high-temperature heat treatment under an inert atmosphere or vacuum to obtain an alkali metal-doped carbon-based adsorbent.

[0033] Specifically, alkali metal ion precursors and cyclodextrins are coordinated and self-assembled to form a regular porous alkali metal-based cyclodextrin organic framework material. Using this as a precursor, the material is subjected to high-temperature heat treatment under certain conditions to form an alkali metal-doped carbon-based adsorbent with highly dispersed adsorption sites and greatly improved texture parameters.

[0034] As an example, in step S1, the alkali metal ion precursor is a salt or alkali containing alkali metal ions; wherein, the alkali metal ions include one or a combination of lithium, sodium, potassium, rubidium, and cesium.

[0035] As an example, alkali metal ion precursors are salts or bases containing potassium metal ions.

[0036] Preferably, the alkali metal ion precursor is potassium hydroxide.

[0037] As an example, in step S1, the cyclodextrin is one or a combination of α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin.

[0038] Preferably, the cyclodextrin is γ-cyclodextrin.

[0039] As an example, in step S1, the molar ratio between deionized water, methanol, alkali metal ion precursor, and cyclodextrin is (0.05~2.0):(0.05~2.0):(4~10):1.

[0040] Specifically, the molar ratio between deionized water, methanol, alkali metal ion precursor, and cyclodextrin can be any value within the range of 0.05:0.05:4:1, 0.05:0.05:10:1, 0.05:2:4:1, 0.05:2:10:1, 2:0.05:4:1:2:0.05:10:1, 2:2:4:1, 2:2:10:1, etc., and can be adjusted according to actual conditions.

[0041] As an example, the ball milling temperature in step S1 is 5–50°C.

[0042] As an example, the ball milling time in step S1 is 4 to 168 hours.

[0043] As an example, the ball milling speed in step S1 is 100 to 1000 rpm.

[0044] Specifically, the ball milling temperature in step S1 can be any value within a range of 5℃, 10℃, 20℃, 30℃, 40℃, 45℃, 50℃, etc., and can be adjusted according to actual conditions; the ball milling time can be any value within a range of 4h, 28h, 72h, 96h, 120h, 144h, 168h, etc., and can be adjusted according to actual conditions; the ball milling speed can be any value within a range of 100rpm, 300rpm, 500rpm, 700rpm, 900rpm, 1000rpm, etc., and can be adjusted according to actual conditions.

[0045] As an example, the inert atmosphere in step S2 is one or a combination of nitrogen, argon, and helium.

[0046] As an example, the temperature of the high-temperature heat treatment in step S2 is 500 to 1000°C, and the time of the high-temperature heat treatment is 0.5 to 5 hours.

[0047] Specifically, the temperature of the high-temperature heat treatment in step S2 can be any value within the range of 500℃, 600℃, 700℃, 800℃, 900℃, 1000℃, etc., and can be adjusted according to the actual situation; the time of the high-temperature heat treatment can be any value within the range of 0.5h, 1h, 2h, 3h, 4h, 4.5h, 5h, etc., and can be adjusted according to the actual situation.

[0048] As an example, the heating rate of the high-temperature heat treatment in step S2 is 1 to 10 °C / min.

[0049] Specifically, the heating rate of the high-temperature heat treatment in step S2 can be any value within the range of 1℃ / min, 3℃ / min, 5℃ / min, 7℃ / min, 9℃ / min, 10℃ / min, etc., and can be adjusted according to the actual situation.

[0050] The present invention also provides an alkali metal-doped carbon-based adsorbent, which is prepared by the above-described method for preparing alkali metal-doped carbon-based adsorbents.

[0051] In addition, the present invention also provides an application of an alkali metal-doped carbon-based adsorbent in the field of carbon dioxide adsorption and capture, wherein the alkali metal-doped carbon-based adsorbent is prepared by the above-described preparation method.

[0052] Preferably, the application of alkali metal-doped carbon-based adsorbents for the adsorption and capture of low-concentration carbon dioxide in flue gas under low-pressure conditions. The low-pressure conditions are 1–4 bar (e.g., any value within the range of 1 bar, 2 bar, 3 bar, 4 bar, etc.); the volume concentration of carbon dioxide is 4%–20% (e.g., any value within the range of 4%, 8%, 12%, 16%, 20%, etc.).

[0053] Specifically, this invention uses alkali metal-based cyclodextrin organic framework materials with regular porous structures as precursors, and utilizes atomically dispersed alkali metal ions in the alkali metal-based cyclodextrin organic framework materials as highly efficient in-situ activators and alkaline adsorption sites, thereby obtaining alkali metal-doped carbon-based adsorbents with highly dispersed adsorption sites and greatly improved texture parameters, thus exhibiting advantages such as large adsorption capacity, fast adsorption rate, easy regeneration, and high cycle stability for low concentrations of carbon dioxide.

[0054] To better understand the alkali metal-doped carbon-based adsorbent, its preparation method, and its application in this invention, specific embodiments are described below. It should be noted that these embodiments are merely descriptive and do not limit the invention in any way.

[0055] Example 1

[0056] This embodiment provides a method for preparing an alkali metal-doped carbon-based adsorbent and the alkali metal-doped carbon-based adsorbent prepared by the method.

[0057] The preparation method of the alkali metal-doped carbon-based adsorbent in this embodiment includes the following steps:

[0058] S1. Add 0.05 mmol deionized water, 0.1 mmol methanol, 5 mmol potassium bicarbonate and 1 mmol γ-cyclodextrin into a ball mill jar and ball mill at 100 rpm for 120 h at 20 °C. After ball milling, wash the mixture with methanol to obtain alkali metal-based cyclodextrin organic framework material (i.e., potassium-based γ-cyclodextrin organic framework material).

[0059] S2. The obtained alkali metal-based cyclodextrin organic framework material is placed in a tube furnace and heated to 500°C at a heating rate of 5°C / min under a nitrogen atmosphere, and held at that temperature for 3 hours to obtain an alkali metal-doped carbon-based adsorbent (i.e., potassium-doped carbon-based adsorbent).

[0060] Example 2

[0061] This embodiment provides a method for preparing an alkali metal-doped carbon-based adsorbent and the alkali metal-doped carbon-based adsorbent prepared by the method.

[0062] The preparation method of the alkali metal-doped carbon-based adsorbent in this embodiment includes the following steps:

[0063] S1. Add 0.2 mmol deionized water, 0.15 mmol methanol, 8 mmol potassium hydroxide and 1 mmol γ-cyclodextrin into a ball mill jar and ball mill at 400 rpm for 120 h at 25 °C. After ball milling, wash the mixture with methanol to obtain alkali metal-based cyclodextrin organic framework material (i.e., potassium-based γ-cyclodextrin organic framework material).

[0064] S2. The obtained alkali metal-based cyclodextrin organic framework material is placed in a tube furnace and heated to 600°C at a heating rate of 2°C / min under a nitrogen atmosphere, and held at that temperature for 5 hours to obtain an alkali metal-doped carbon-based adsorbent (i.e., potassium-doped carbon-based adsorbent).

[0065] Example 3

[0066] This embodiment provides a method for preparing an alkali metal-doped carbon-based adsorbent and the alkali metal-doped carbon-based adsorbent prepared by the method.

[0067] The preparation method of the alkali metal-doped carbon-based adsorbent in this embodiment includes the following steps:

[0068] S1. Add 0.2 mmol deionized water, 0.5 mmol methanol, 8 mmol sodium hydroxide and 1 mmol β-cyclodextrin into a ball mill jar and ball mill at 35 °C and 600 rpm for 144 h. After ball milling, wash the mixture with methanol to obtain alkali metal-based cyclodextrin organic framework material (i.e., sodium-based β-cyclodextrin organic framework material).

[0069] S2. The obtained alkali metal-based cyclodextrin organic framework material is placed in a tube furnace and heated to 800°C at a heating rate of 10°C / min under a nitrogen atmosphere, and held at that temperature for 3 hours to obtain an alkali metal-doped carbon-based adsorbent (i.e., sodium-doped carbon-based adsorbent).

[0070] Example 4

[0071] This embodiment provides a method for preparing an alkali metal-doped carbon-based adsorbent and the alkali metal-doped carbon-based adsorbent prepared by the method.

[0072] The preparation method of the alkali metal-doped carbon-based adsorbent in this embodiment includes the following steps:

[0073] S1. Add 1 mmol of deionized water, 1 mmol of methanol, 8 mmol of cesium hydroxide and 1 mmol of α-cyclodextrin into a ball mill jar, and ball mill at 35°C and 800 rpm for 96 h. After ball milling, the mixture is washed with methanol to obtain alkali metal-based cyclodextrin organic framework material (i.e., cesium-based α-cyclodextrin organic framework material).

[0074] S2. The obtained alkali metal-based cyclodextrin organic framework material is placed in a tube furnace and heated to 500°C at a heating rate of 5°C / min under a nitrogen atmosphere, and held at that temperature for 4 hours to obtain an alkali metal-doped carbon-based adsorbent (i.e., cesium-doped carbon-based adsorbent).

[0075] Example 5

[0076] This embodiment provides a method for preparing an alkali metal-doped carbon-based adsorbent and the alkali metal-doped carbon-based adsorbent prepared by the method.

[0077] The difference between the preparation method of the alkali metal-doped carbon-based adsorbent in this embodiment and that in Example 2 is that in step S2, the temperature is raised to 700°C at a heating rate of 2°C / min and held for 5 hours; the other methods and steps are the same as in Example 2 and will not be repeated here. Finally, the alkali metal-doped carbon-based adsorbent (i.e., potassium-doped carbon-based adsorbent) is prepared.

[0078] Example 6

[0079] This embodiment provides a method for preparing an alkali metal-doped carbon-based adsorbent and the alkali metal-doped carbon-based adsorbent prepared by the method.

[0080] The preparation method of the alkali metal-doped carbon-based adsorbent in this embodiment includes the following steps:

[0081] S1. Add 0.5 mmol deionized water, 0.8 mmol methanol, 10 mmol potassium fluoride and 1 mmol β-cyclodextrin into a ball mill jar and ball mill at 500 rpm for 120 h at 40 °C. After ball milling, wash the mixture with methanol to obtain alkali metal-based cyclodextrin organic framework material (i.e., potassium-based β-cyclodextrin organic framework material).

[0082] S2. The obtained alkali metal-based cyclodextrin organic framework material is placed in a tube furnace and heated to 700°C at a heating rate of 2°C / min under a nitrogen atmosphere, and held at that temperature for 2 hours to obtain an alkali metal-doped carbon-based adsorbent (i.e., potassium-doped carbon-based adsorbent).

[0083] Example 7

[0084] This embodiment provides a method for preparing an alkali metal-doped carbon-based adsorbent and the alkali metal-doped carbon-based adsorbent prepared by the method.

[0085] The preparation method of the alkali metal-doped carbon-based adsorbent in this embodiment includes the following steps:

[0086] S1. Add 0.2 mmol deionized water, 0.5 mmol methanol, 5 mmol potassium bicarbonate and 1 mmol γ-cyclodextrin into a ball mill jar and ball mill at 30°C and 400 rpm for 72 h. After ball milling, wash the mixture with methanol to obtain alkali metal-based cyclodextrin organic framework material (i.e., potassium-based γ-cyclodextrin organic framework material).

[0087] S2. The obtained alkali metal-based cyclodextrin organic framework material is placed in a tube furnace and heated to 600°C at a heating rate of 10°C / min under a nitrogen atmosphere, and held at that temperature for 4 hours to obtain an alkali metal-doped carbon-based adsorbent (i.e., potassium-doped carbon-based adsorbent).

[0088] Example 8

[0089] This embodiment provides a method for preparing an alkali metal-doped carbon-based adsorbent and the alkali metal-doped carbon-based adsorbent prepared by the method.

[0090] The difference between the preparation method of the alkali metal-doped carbon-based adsorbent in this embodiment and that in Example 2 is that in step S2, the temperature is raised to 800°C at a heating rate of 2°C / min and held for 5 hours; the other methods and steps are the same as in Example 2 and will not be repeated here. Finally, the alkali metal-doped carbon-based adsorbent (i.e., potassium-doped carbon-based adsorbent) is prepared.

[0091] Example 9

[0092] This embodiment provides a method for preparing an alkali metal-doped carbon-based adsorbent and the alkali metal-doped carbon-based adsorbent prepared by the method.

[0093] The preparation method of the alkali metal-doped carbon-based adsorbent in this embodiment includes the following steps:

[0094] S1. Add 1.5 mmol deionized water, 1.5 mmol methanol, 4 mmol lithium chloride and 1 mmol α-cyclodextrin into a ball mill jar and ball mill at 800 rpm for 24 h at 40 °C. After ball milling, wash the mixture with methanol to obtain alkali metal-based cyclodextrin organic framework material (i.e. lithium-based α-cyclodextrin organic framework material).

[0095] S2. The obtained alkali metal-based cyclodextrin organic framework material is placed in a tube furnace and heated to 1000℃ at a heating rate of 5℃ / min under a nitrogen atmosphere, and held at that temperature for 2 hours to obtain an alkali metal-doped carbon-based adsorbent (i.e., lithium-doped carbon-based adsorbent).

[0096] Example 10

[0097] This embodiment provides a method for preparing an alkali metal-doped carbon-based adsorbent and the alkali metal-doped carbon-based adsorbent prepared by the method.

[0098] The preparation method of the alkali metal-doped carbon-based adsorbent in this embodiment includes the following steps:

[0099] S1. Add 2 mmol of deionized water, 1 mmol of methanol, 10 mmol of lithium hydroxide and 1 mmol of γ-cyclodextrin into a ball mill jar, and ball mill at 500 rpm for 100 h at 50 °C. After ball milling, the mixture is washed with methanol to obtain alkali metal-based cyclodextrin organic framework material (i.e., lithium-based γ-cyclodextrin organic framework material).

[0100] S2. The obtained alkali metal-based cyclodextrin organic framework material is placed in a tube furnace and heated to 800°C at a heating rate of 4°C / min under a nitrogen atmosphere, and held at that temperature for 5 hours to obtain an alkali metal-doped carbon-based adsorbent (i.e., lithium-doped carbon-based adsorbent).

[0101] Example 11

[0102] This embodiment provides a method for preparing an alkali metal-doped carbon-based adsorbent and the alkali metal-doped carbon-based adsorbent prepared by the method.

[0103] The difference between the preparation method of the alkali metal-doped carbon-based adsorbent in this embodiment and that in Example 2 is that in step S2, the temperature is raised to 900°C at a rate of 2°C / min and held for 5 hours; the other methods and steps are the same as in Example 2 and will not be repeated here. Finally, the alkali metal-doped carbon-based adsorbent (i.e., potassium-doped carbon-based adsorbent) is prepared.

[0104] Example 12

[0105] This embodiment provides a method for preparing an alkali metal-doped carbon-based adsorbent and the alkali metal-doped carbon-based adsorbent prepared by the method.

[0106] The preparation method of the alkali metal-doped carbon-based adsorbent in this embodiment includes the following steps:

[0107] S1. Add 0.2 mmol of deionized water, 0.5 mmol of methanol, 6 mmol of rubidium hydroxide and 1 mmol of β-cyclodextrin into a ball mill jar, and ball mill at 35 °C and 600 rpm for 150 h. After ball milling, the mixture is washed with methanol to obtain alkali metal-based cyclodextrin organic framework material (i.e., rubidium-based β-cyclodextrin organic framework material).

[0108] S2. The obtained alkali metal-based cyclodextrin organic framework material is placed in a tube furnace and heated to 800°C at a heating rate of 10°C / min under a nitrogen atmosphere, and held at that temperature for 3 hours to obtain an alkali metal-doped carbon-based adsorbent (i.e., rubidium-doped carbon-based adsorbent).

[0109] See Figures 1-4 The figures show the potassium-doped carbon-based adsorbents prepared in Examples 2, 5, 8, and 11, respectively. As can be seen from the figures, the prepared potassium-doped carbon-based adsorbents have micron-sized particles and nano-sized pores. Especially when the heat treatment temperature is high, reaching 900°C, the prepared potassium-doped carbon-based adsorbents exhibit a highly developed porous structure. Furthermore, nitrogen adsorption-desorption experiments were conducted on the potassium-doped carbon-based adsorbents prepared in Examples 2, 5, 8, and 11. The test results showed that the specific surface areas of the potassium-doped carbon-based adsorbents prepared in Examples 2, 5, 8, and 11 were 476 m², respectively. 2 / g、542m 2 / g、629m 2 / g、1435m 2 / g.

[0110] Application examples

[0111] This application example provides an application of an alkali metal-doped carbon-based adsorbent in the field of carbon dioxide adsorption and capture. The alkali metal-doped carbon-based adsorbents prepared in Examples 1 to 12 were used to adsorb and capture carbon dioxide with a volume concentration of 15% at 40°C. The amount of carbon dioxide adsorbed is shown in Table 1.

[0112] Table 1. Adsorption capacity of the alkali metal-doped carbon-based adsorbents prepared in Examples 1-12 (numbered 1-12) for adsorption and capture of 15% carbon dioxide at 40°C.

[0113]

[0114] As shown in Table 1, the adsorption results of the alkali metal-doped carbon-based adsorbent at 40°C can achieve an adsorption capacity of up to 1.50 mmol / g for 15% carbon dioxide by volume, which is among the highest values ​​reported in the literature. During material preparation, the heat treatment temperature significantly affects the texture parameters and pore structure of the material, thus significantly influencing the final adsorption performance of the alkali metal-doped carbon-based adsorbent for carbon dioxide. Furthermore, compared to alkali metal doping with elements such as lithium, sodium, rubidium, and cesium, potassium-doped carbon-based adsorbents exhibit a significant advantage in adsorption performance. This may be because potassium has a better pore-activating effect on carbon materials during heat treatment.

[0115] In summary, this invention addresses the shortcomings of existing porous carbon materials in adsorbing low-pressure, low-concentration carbon dioxide, as well as the cumbersome preparation methods, uneven species dispersion, deteriorated texture parameters, and large amounts of alkali metal precursors required in the preparation of existing alkali metal-modified carbon materials. This invention utilizes the coordination self-assembly of alkali metal ion precursors and cyclodextrin to form a well-structured porous alkali metal-based cyclodextrin organic framework material. Using this framework as a precursor, the atomically dispersed alkali metal ions within the framework act as highly efficient in-situ activators and alkaline adsorption sites, resulting in an alkali metal-doped carbon-based adsorbent with highly dispersed adsorption sites and significantly improved texture parameters. This adsorbent exhibits advantages such as large adsorption capacity, fast adsorption rate, easy regeneration, and high cycle stability for low-concentration carbon dioxide, showing promising application prospects in the capture of low-concentration carbon dioxide in flue gas. Furthermore, the preparation method of this alkali metal-doped carbon-based adsorbent is simple, easy to scale up, and inexpensive, possessing significant potential for widespread application. Therefore, this invention effectively overcomes the various shortcomings of existing technologies and has high industrial applicability.

[0116] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing an alkali metal-doped carbon-based adsorbent, characterized in that: The preparation method includes the following steps: S1. Deionized water, methanol, alkali metal ion precursor, and cyclodextrin are added to a ball mill jar and ball-milled and mixed. After washing with methanol, an alkali metal-based cyclodextrin organic framework material is obtained. The alkali metal ion precursor is a salt or base containing potassium metal ions. The cyclodextrin is γ-cyclodextrin. The molar ratio of deionized water, methanol, alkali metal ion precursor, and cyclodextrin is (0.05~2.0):(0.05~2.0):(4~10):

1. S2. The alkali metal-based cyclodextrin organic framework material is heated to 900°C at a heating rate of 2°C / min under an inert atmosphere or vacuum to obtain an alkali metal-doped carbon-based adsorbent; the high-temperature heat treatment time is 0.5~5h.

2. The method for preparing the alkali metal-doped carbon-based adsorbent according to claim 1, characterized in that: Step S1 includes one or a combination of the following conditions: The temperature of the ball mill is 5~50℃; The ball milling time is 4~168h; The ball milling speed is 100~1000 rpm.

3. The method for preparing the alkali metal-doped carbon-based adsorbent according to claim 1, characterized in that: The inert atmosphere mentioned in step S2 is one or a combination of nitrogen, argon, and helium.

4. An alkali metal-doped carbon-based adsorbent prepared by the method for preparing an alkali metal-doped carbon-based adsorbent according to any one of claims 1 to 3.

5. An application of an alkali metal-doped carbon-based adsorbent in the field of carbon dioxide adsorption and capture, characterized in that: The alkali metal-doped carbon-based adsorbent is prepared by the preparation method of the alkali metal-doped carbon-based adsorbent according to any one of claims 1 to 3; the alkali metal-doped carbon-based adsorbent adsorbs and captures carbon dioxide with a volume concentration of 4% to 20% under low pressure conditions of 1 to 4 bar.

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