Porous metal-cyanide-based framework material having cation-gated effect, preparation method therefor, and use thereof in carbon-dioxide capture

Abstract

Provided in the present invention are a porous metal-cyanide-based framework material (MCF) having a cation-gated effect, a preparation method therefor, and the use thereof in carbon-dioxide capture. The framework material has a general structural formula of Mx[M'(CN)6]y•Az•nH2O, wherein n represents the water content of the material, and 0≤n≤10; when n≥1, the XRD pattern of the crystal structure has a single peak at 2θ=16±2° and 20±2°, respectively, and has a single peak or a double peak at 2θ=13±2°, 22±2° and 24±2°, respectively, the crystal structure belonging to the space group of formula (I) in a trigonal crystal system (space group number 167); and when 0≤n<1, the XRD pattern of the crystal structure has a single peak at 2θ=10±2° and 16.5±2°, respectively, and has a single peak or a double peak at 2θ=14.5±2° and 20.2±2°, respectively, the space group of the crystal structure changing into a P2 / c space group (space group number 13). The framework material has a cage-like structure, and each cage has six hexagonal pore windows and six quadrilateral pore windows. The monovalent cations at the hexagonal pore windows exhibit a gating effect and can selectively allow carbon dioxide molecules to pass through. The framework material has the highest CO2 adsorption capacity and selectivity in carbon dioxide capture, especially in carbon dioxide adsorption applications under low-pressure (≤0.15 bar) and high-humidity (≥40% RH) environments.

Description

A porous metal cyanide framework material with cation-gated effect, its preparation method and carbon dioxide capture application Technical Field

[0001] This invention belongs to the field of materials technology, specifically relating to a metal cyanide material, and more particularly to a porous metal cyanide material with cation-gated effect, its preparation method, and its carbon dioxide capture application. Background Technology

[0002] The increasing concentration of carbon dioxide in the atmosphere year by year has led to environmental problems such as the greenhouse effect. China has therefore set the goals of achieving "carbon peaking" before 2030 and "carbon neutrality" before 2060. Carbon capture and storage (CCS) technology is a key means of reducing carbon dioxide emissions into the atmosphere, with CO2 capture technology, as the upstream foundation, being crucial. Among numerous sources of carbon dioxide emissions, CO2 emitted from flue gas produced after the combustion of fossil fuels accounts for 65% of total emissions. Therefore, efficient CO2 capture from flue gas is of great significance for achieving the "dual carbon" goals. In addition to flue gas CO2 capture, the development of high-performance carbon capture materials is also urgently needed for biogas CO2 capture and confined space CO2 capture.

[0003] These scenarios involve low CO2 concentrations, falling under the category of low-pressure gas adsorption (Kolle, JM, Fayaz, M., Sayari, A. Chem. Rev. 121, 7280-7345 (2021)). For example, the CO2 concentration in flue gas is 3%–15% (15% is commonly used), and the N2 concentration is 65%–85% (85% is commonly used). In addition, it contains small amounts of water vapor, trace amounts of SO2 and NO, etc. Specifically, the CO2 concentration in flue gas produced after coal combustion is 11%, the N2 concentration is 76%, the H2O concentration is 6%, and the SO2 and NO concentrations are 300–500 ppm (R. Zevenhoven, et al. In Control of Pollutants in Flue Gases and Fuel Gases; Helsinki University of Technology: Helsinki (2021)). This low-pressure environment (≤15 bar) makes it difficult for adsorbents to achieve high low-pressure adsorption capacity and selectivity. On the other hand, water vapor in high-humidity environments (≥40% RH) has a negative impact on most adsorbents (A. Rajendran, et al. Adv. Mater. 2301730 (2023)). The competitive adsorption between H2O and CO2 causes H2O to occupy a large number of CO2 adsorption sites, resulting in a significant decrease in CO2 adsorption capacity and selectivity. Therefore, it is very difficult to selectively and with high adsorption capacity capture CO2 gas from low-pressure, high-humidity flue gas.

[0004] Currently, the most mature industrial method for capturing carbon dioxide is liquid amine absorption, which boasts high CO2 adsorption capacity and selectivity. However, it suffers from drawbacks such as high regeneration energy consumption, slow adsorption kinetics, easy equipment corrosion, and environmental unfriendliness, making further improvements difficult (MJ Lashaki, et al. Chem. Soc. Rev. 48, 3320-3405 (2019); RLSiegelman, et al. Nat. Mater. 20, 1060-1072 (2021)). In contrast, physical adsorption based on porous materials has become an ideal alternative technology due to its advantages such as low regeneration energy consumption, simple operation, and environmental friendliness.

[0005] The design and selection of adsorption materials are central to carbon dioxide physical adsorption technology. An ideal adsorption material should possess comprehensive and excellent properties, including adsorption performance (CO2 adsorption capacity, selectivity, and kinetics), desorption performance (adsorbent regeneration energy consumption), moisture resistance (CO2 adsorption capacity under water vapor conditions), and engineering performance (stability, scalability, cost, environmental friendliness, etc.), thereby meeting the requirements of practical applications. Although research on CO2 capture materials has been extensive over the past two decades, high-performance materials truly suitable for industrial CO2 capture remain scarce.

[0006] Traditional zeolite molecular sieve materials, such as 13X and 5A, typically have one-dimensional channel-shaped pores, and the pore structure is difficult to design precisely, making it difficult to achieve high CO2 adsorption capacity and selectivity. At the same time, zeolite materials have extremely poor moisture resistance, and the CO2 adsorption capacity will decrease significantly in the presence of water vapor (J. Merel, et al. Chem. Res. 47, 209-215 (2008)).

[0007] Porous framework materials, such as metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), are more likely to achieve high CO2 adsorption capacity and selectivity due to their advantages such as high porosity, precise structural design, and ease of functionalization. Currently, based on the pore size control and functionalization strategies of porous framework materials, many related materials have been developed (such as Mg-MOF-74, UTSA-16, SIFSIX-2-Cu-i, and ALF, etc.; SR Caskey, et al. J. Am. Chem. Soc. 130, 10870-10871 (2008); S. Xiang, et al. Nat. Commun. 3, 954 (2012); P. Nugent, et al. Nature 495, 80-84 (2013); HAEvans, et al. Sci. Adv. 8, et al. 1473 (2022)). However, they still have problems such as insufficient CO2 adsorption capacity at low pressure (0.15 bar, CO2 concentration in flue gas), low adsorption selectivity, and performance degradation due to water vapor competitive adsorption (Z. Zhang, et al. Energy). Environ. Sci. 7, 2868-2899 (2014); A. Rajendran, et al. Adv. Mater. 35, 2301730 (2023)); More importantly, most porous framework materials have poor engineering performance and usually suffer from problems such as poor stability, high cost, solvent toxicity or complex synthesis, making it difficult to realize industrial applications (D. Chakraborty, et al. Adv. Funct. Mater. 33, 2309089 (2023)).

[0008] To date, although CALF-20, a MOF material for CO2 capture in flue gas, has been reported, it exhibits relatively excellent overall performance, with CO2 adsorption capacity remaining unaffected under 40% RH humidity conditions (J.-B. Lin, et al. Science 374, 1464-1469 (2021)), and its commercial application has been promoted in collaboration with BASF and Svante (related patent: CA2904546A1), CALF-20 still suffers from insufficient low-pressure CO2 adsorption capacity (adsorption capacity of 2.7 mmol g at 298 K and 0.15 bar). -1 Its CO2 capture efficiency and application are severely limited by defects such as severe degradation of CO2 adsorption performance in high humidity environments (≥40%RH) and poor environmental friendliness (the synthesis uses toxic methanol solvent).

[0009] In summary, in the field of flue gas CO2 capture, existing framework materials still cannot overcome the trade-off effect between CO2 adsorption capacity and selectivity in low-pressure (≤0.15 bar) and high-humidity environments (≥40% RH), and the framework materials have poor moisture resistance. This is manifested in the fact that the carbon dioxide adsorption performance of the framework materials is severely degraded in high-humidity environments, making them unsuitable for efficient and low-energy CO2 capture in industry. Summary of the Invention

[0010] To address the shortcomings of existing technologies, this invention provides a metal cyanide-based framework (MCF) material with cation-gated effect, its preparation method, and its application in carbon dioxide capture. The framework material of this invention contains free monovalent cations, possesses a unique crystal structure and unit cell parameters, and multiple features work synergistically. This framework material exhibits a cation-gated effect, demonstrating a novel CO2 adsorption and separation mechanism, excellent moisture resistance, and exhibits the highest CO2 adsorption capacity and selectivity in carbon dioxide capture applications, especially in low-pressure (≤0.15 bar), high-humidity environments (≥40% RH). Under conditions of 296 K, 0.15 bar, and 40–80% RH, it can achieve a CO2 adsorption capacity of at least 3.5 mmol g / L. -1 (140cm 3 cm -3 The amount of carbon dioxide adsorbed, and the IAST selectivity (S) for CO2 / N2 (15 / 85, v / v) adsWith a value ≥500, this technology solves the problems of existing framework materials being unable to simultaneously achieve high carbon dioxide selectivity and high carbon dioxide adsorption capacity in low-pressure, high-humidity environments, as well as the poor moisture resistance of framework materials. The aforementioned metal cyanide framework material is a branch of metal-organic framework materials.

[0011] Some terms used herein are explicitly defined below, while others are illustrated with relevant examples. For any term not explicitly defined, it should be interpreted in conjunction with this specification before assigning it its conventional meaning as understood herein.

[0012] In this invention, "RH" is an abbreviation for relative humidity, which refers to the ratio of the actual partial pressure of water vapor to the equilibrium (or saturated) vapor pressure of water at a given temperature.

[0013] In this invention, "enclosed space" refers to an area with limited or even almost no air circulation. For example, the CO2 concentration of the enclosed space can be 5,000 to 10,000 ppm.

[0014] In this invention, "mmol g⁻¹" is the unit of molar adsorption capacity (QM), which refers to the ratio of the amount of CO₂ adsorbed (in mmol) to the mass of the adsorbent (in g). Similarly, "cm³ cm⁻³" is the unit of volumetric adsorption capacity (QV), representing the ratio of the volume of adsorbed CO₂ (in cm³) to the volume of the adsorbent (in cm³). The conversion formula is: Q V =Q M ×V m ×D cry

[0015] Where V M It is the molar volume of a gas, with units of L mol. -1 Under standard conditions, V M =22.4 L mol -1 ;D cry It is the crystal density of the material, measured in g / cm³. -3 The crystal density of the framework material described in this invention is 1.7–2 g cm⁻¹. -3 .

[0016] In this invention, "selectivity," "separation selectivity," or "IAST selectivity" is calculated based on the Ideal Adsorption Solution Theory (IAST). The Ideal Adsorption Solution Theory refers to the adsorption isotherm equation derived from thermodynamic laws when the mixture within the adsorption layer is treated as an ideal solution during gas adsorption. The specific calculation method is described in Myers, A.L. et al. (AIChE J. 1965, 11, 121–127). First, the single-component adsorption isotherm is fitted to the Dual Site Langmuir-Freundlich model, with the following expression:

[0017] Where q is the amount of gas adsorbed in the mixture; p is the equilibrium pressure, q A b A v A q B b B and v B These are constants, and these parameters are subsequently used for IAST calculations. Using the above formulas, the molar adsorption capacity q1 of CO2 and the molar adsorption capacity q2 of N2 in the mixed gas at different pressures can be calculated. Furthermore, the IAST selectivity (S) can be calculated using the formulas. ads The calculation formula is:

[0018] Where q1 and q2 are the adsorption amounts of CO2 and N2 in the mixed gas by the material, respectively, and p1 and p2 are the mole fractions of CO2 and N2 in the gas phase.

[0019] In this invention, "v / v" refers to the volume ratio of different gas components in a gas mixture.

[0020] Furthermore, existing materials struggle to achieve both high CO2 adsorption capacity and selectivity simultaneously, exhibiting a trade-off effect between the two. This is due to limitations in material design, specifically: on the one hand, microporous materials, with pore sizes larger than CO2 molecules but smaller than N2 molecules, can achieve complete molecular sieving, resulting in extremely high separation selectivity, but their limited pore volume leads to lower CO2 adsorption capacity; on the other hand, macroporous materials can achieve higher CO2 adsorption capacity, but they also adsorb more N2, resulting in lower selectivity. As shown in Figure 1, this figure summarizes the limitations of existing porous materials in terms of CO2 adsorption capacity and selectivity (Zhou, Y. et al. Science 373, 315-320 (2021); Hu, Y. et al. Adv. Funct. Mater. 33, 2213915 (2023)). The trade-offline refers to the equilibrium boundary between CO2 adsorption capacity and selectivity of existing porous materials, which is obtained by statistically analyzing data of materials with reported performance. Currently, the performance of traditional porous materials is limited to within the trade-offline, meaning that the combined performance of CO2 adsorption capacity and CO2 / N2 selectivity cannot reach the upper right of the trade-offline. However, the porous material obtained by this invention through specific design and control can overcome this limitation.

[0021] In this invention, "moisture resistance" refers to the adsorbent's ability to maintain its carbon dioxide adsorption performance in the presence of water vapor. This performance is determined by conducting breakthrough experiments under both dry and humid conditions.

[0022] The technical solution of the present invention is as follows:

[0023] This invention provides a metal cyanide-based framework material, the framework material having the general structural formula M. x [M′(CN)6] y ·A z ·nH₂O, where M is a tetracoordinate metal ion, 1≤x≤8, [M′(CN)₆] is a hexacyanide ion, 1≤y≤6, A is a monovalent cation, 1≤z≤6, and satisfies 2x-4y+z=0; n represents the water content of the material, 0≤n≤10; the framework material of the present invention is composed of a crystal structure, which has a unique crystal structure and unit cell parameters. When 1≤n≤10, the XRD pattern of the crystal structure has a single peak at 2θ=16±2°, 20±2°, and a single or double peak at 13±2°, 22±2°, 24±2°. The crystal structure belongs to the trigonal crystal system. Space group (space group number 167), cell parameters are When 0 ≤ n < 1, the XRD pattern of the crystal structure has a single peak at 2θ = 10 ± 2° and 16.5 ± 2°, and a single or double peak at 14.5 ± 2° and 20.2 ± 2°. The space group of the crystal structure is... The space group (space group number 167) is transformed into the P2 / c space group (space group number 13), with the cell parameters being... The framework material is a branch of metal-organic framework materials.

[0024] As is known to those skilled in the art, proportionally expanding or shrinking x, y, z, and n in the structural formula does not change the material composition, and therefore still falls within the scope of protection of this invention. The crystal structure and cell parameters are obtained by single-crystal X-ray diffraction or powder X-ray diffraction in a vacuum or inert gas atmosphere. Furthermore, the transformation of the crystal structure and cell parameters is reversible; when the water content of the framework material recovers to n≥1, the space group of the material can be restored from space group P2 / c (space group number 13) to... Space group (space group number 167).

[0025] Preferably, the crystal structure of the framework material is a dodecahedral-like porous cage structure. This dodecahedral-like porous cage structure refers to a spatial geometric body surrounded by atoms and chemical bonds. Its twelve geometric faces include six hexagonal geometric faces and six quadrilateral geometric faces. Each cage has twelve windows, and the cages are connected by these windows. The monovalent cation A is in a free state within the cages. The dodecahedral-like porous cage structure is verified by reduction, fitting, or refinement based on XRD test data. The windows are divided into quadrilateral windows and hexagonal windows. The twelve windows of the cage include six quadrilateral windows and six hexagonal windows, corresponding to the six hexagonal geometric faces and six quadrilateral geometric faces. Preferably, the diameter of the hexagonal windows is... The diameter of the quadrilateral window is The quadrilateral windows are too small to allow guest molecules (CO2, CH4, N2, etc.) to pass through, and only serve as a supporting frame; the hexagonal windows allow guest molecules to pass through and can serve as transport windows for guest molecules; the hexagonal and quadrilateral windows of the cage are rigid structures, and their size does not change with changes in external conditions (see Figure 4).

[0026] The framework material of this invention possesses a unique crystal structure and unit cell parameters. These unique crystal structure and unit cell parameters enable the framework material to have a larger dynamic pore volume and specific surface area, while simultaneously exposing more monovalent cation sites. The synergistic effect of multiple structural factors enables extremely high CO2 adsorption capacity and selectivity. Furthermore, the extremely high CO2 adsorption capacity and selectivity can be achieved through a cation-gated effect. The cation-gated effect described in this invention refers to the fact that a dodecahedral-like pore cage can accommodate guest molecules, while the hexagonal pore windows that allow guest molecule transport act as a "gate frame." Monovalent cations are located near the hexagonal pore windows and can selectively allow guest molecules to enter, thus having a "gating" effect. CO2 molecules can undergo strong electrostatic interactions with monovalent cations, causing the monovalent cations to shift, which is equivalent to opening the cation gate, allowing CO2 molecules to enter the pore cage through the hexagonal pore windows. Other molecules such as N2 and CH4 cannot undergo strong electrostatic interactions with monovalent cations and cannot open the cation gate, therefore they are difficult to enter the pore cage (Figure 5). This unique cation-gated effect is achieved through the synergistic effect of the dodecahedral porous cage structure and free cations. As a novel CO2 adsorption and separation mechanism, it is advantageous for simultaneously achieving extremely high CO2 adsorption capacity and selectivity, especially CO2 / N2 and CO2 / CH4 selectivity. The monovalent cations within the framework material can act as co-adsorption sites for CO2 / H2O, meaning that after adsorbing water molecules, the monovalent cations can still adsorb CO2 (Figure 6). This co-adsorption mechanism enables the framework material to efficiently co-adsorb large amounts of CO2 and H2O molecules from humid gases, maintaining a high CO2 adsorption capacity even under high humidity conditions (≥40% RH).

[0027] In summary, the framework material exhibits extremely high CO2 adsorption capacity and selectivity in carbon dioxide capture applications, especially in low-pressure (≤0.15 bar) and high-humidity environments (≥40% RH) for carbon dioxide adsorption.

[0028] In some embodiments of the present invention, the four-coordinated metal ion M is selected from the divalent transition metal ion Zn. 2+ Fe 2+ Co 2+ Cu 2+ Ni 2+ Cd 2+ Any one or more of the following;

[0029] In some embodiments of the present invention, the hexacyanide ion [M′(CN)6] is selected from [Fe(CN)6]. 4- [Ru(CN)6] 4- and [Os(CN)6] 4- Any one or more of the following;

[0030] In one embodiment of the present invention, the monovalent cation A is selected from H+. + NH4 + Li + Na + K + Rb + Cs + ,Fr + Any one or more of the following.

[0031] In some embodiments of the present invention, the frame material includes, but is not limited to, Zn. x [M′(CN)6] y (NH4) z ·nH2O、Zn x [M′(CN)6] y ·Na z ·nH2O、Zn x [M′(CN)6] y ·K z ·nH2O、Zn x [M′(CN)6] y ·Rb z ·nH₂O, wherein [M′(CN)₆] is selected from [Fe(CN)₆] 4- [Ru(CN)6] 4- and [Os(CN)6] 4- Any one or more of the following, 2.5≤x≤3.5, 1.5≤y≤2.5, 1.5≤z≤2.5, and satisfying 2x-4y+z=0.

[0032] In some embodiments of the present invention, the framework material comprises elements M, M′, C, N, A, H, and O, wherein the molar fraction of M is 5%–15%, the molar fraction of M′ is 3%–10%, the molar fraction of C is 30%–45%, the molar fraction of N is 30%–45%, the molar fraction of A is 3%–10%, the molar fraction of H is 0%–40%, and the molar fraction of O is 0%–20%. The molar fraction of the elements can be tested by a combination of one or more methods selected from atomic absorption spectrometry (AAS), inductively coupled plasma emission spectrometry (ICP), organic elemental analysis (EA), and energy-dispersive X-ray spectroscopy (EDS).

[0033] In some embodiments of the present invention, the BET specific surface area of ​​the frame material is between 200 and 1000 m². 2 g -1 The BET specific surface area can be determined by carbon dioxide, nitrogen or argon molecules.

[0034] In some embodiments of the present invention, when 0 ≤ n < 1, the metal cyanide framework material exhibits a cation-gated effect. This cation-gated effect selectively allows CO2 molecules to pass through the pores while essentially preventing N2 molecules from passing through, thereby achieving extremely high CO2 / N2 separation selectivity and extremely high CO2 adsorption capacity. Further, the cation-gated effect refers to a CO2 to N2 adsorption molar ratio greater than 10 and a CO2 adsorption capacity greater than 3 mmol g under the same temperature and pressure conditions. -1 Further, the temperature is 273–333 K; further, the pressure is 0.15–1 bar; further, when the temperature is 273–333 K and the pressure is 0.15–1 bar, the N2 adsorption capacity of the framework material is less than 0.3 mmol g. -1 Furthermore, when the temperature and pressure are 296 K and 1 bar, the molar ratio of CO2 to N2 adsorption capacity of the framework material reaches more than 20, and the CO2 adsorption capacity is greater than 4 mmol g. -1 .

[0035] In some embodiments of the present invention, when 0 ≤ n < 1, at a temperature of 296–313 K and a pressure of 1 bar, the IAST selectivity (Si) of the framework material for a CO2 / N2 ratio of 15 / 85 is calculated according to the Ideal Adsorption Solution Theory (IAST). ads ≥500.

[0036] In one embodiment of the present invention, when the framework material is Zn3[Fe(CN)6]2·K2, the CO2 adsorption capacity at 296 K and 1 bar is ≥4.5 mmol g. -1 N2 adsorption capacity ≤ 0.2 mmol g -1 For a CO2 / N2 separation selectivity of 15 / 85 (S ads ≥10,000.

[0037] Furthermore, when 0 ≤ n < 1, within the temperature range of 196 K to 333 K, the CO2 saturated adsorption capacity of the framework material is greater than 3 mmol g. -1 (116cm 3 cm -3 The saturated adsorption capacity of N2 is less than 0.3 mmol g. -1 (12cm 3 cm -3 ).

[0038] In one embodiment of the present invention, when the frame material is Zn 3 / 2[Ru(CN)6]·K, CO2 adsorption capacity at 296 K and 0.01 bar (10,000 ppm) ≥ 2.1 mmol g -1 The CO2 adsorption capacity at 296 K and 0.005 bar (5,000 ppm) is ≥1.4 mmol g. -1 Furthermore, the framework material exhibits IAST selectivity (S1) for a CO2 / N2 ratio of 1 / 99. ads ≥2,500.

[0039] In some embodiments of the present invention, when the CO2 pressure is 0.15 bar and the humidity is 40-80% RH, the metal cyanide framework material can achieve at least 3.5 mmol g at 296 K. -1 (140cm 3 cm -3 The carbon dioxide adsorption capacity decreased by less than 15% compared to the dry conditions, and the IAST selectivity (S) for CO2 / N2 (15 / 85, v / v) was [not specified]. ads ≥500.

[0040] This invention also provides a method for preparing a metal cyanide framework material, the method comprising the following steps:

[0041] (1) First, adjust the pH of the solution containing the tetracoordinated metal ion M and the solution containing the hexacyanide ion [M′(CN)6] to pH = 4-7 respectively. Then, mix and stir the two solutions to carry out the reaction. The molar concentration of both the M solution and the [M′(CN)6] solution is ≤1 mol / L. -1 After the reaction is complete, a framework material intermediate is obtained;

[0042] (2) The framework material intermediate is immersed in an aqueous or organic solution containing monovalent cation A for ion exchange, wherein the concentration of A ions in the solution is ≥0.05 mol / L. -1 Repeat the exchange steps multiple times until the molar fraction of monovalent cation A in the framework material is 3% to 10%, and obtain a framework material with a water content of 1 ≤ n ≤ 10.

[0043] Existing preparation methods typically employ simple room-temperature precipitation, which readily results in cubic structures with poor crystallinity and inherent defects. However, the preparation method described in this invention, by adjusting the pH to a weakly acidic and neutral environment (pH = 4–7) and preparing solutions of each component with specific molar concentrations, reduces the rate of coordination nucleation of M with [M′(CN)6], thereby improving crystal quality and crystal structure integrity. Furthermore, the solvothermal reaction under weakly acidic and neutral conditions facilitates the four-coordinate connection of M with the nitrogen atom in the cyano group, resulting in a unique crystal structure and unit cell parameters. Crystal structure detection, refinement, and software fitting revealed a dodecahedral porous cage structure. The high-temperature conditions used in the solvothermal reaction also promote crystal growth. In summary, the preparation method described in this invention, by precisely adjusting the temperature and pH of the reaction system, can produce framework materials with unique crystal structures and unit cell parameters.

[0044] In one embodiment of the present invention, the four-coordinated metal ion M is selected from Zn. 2+ Fe 2+ Co 2+ Cu 2+ Ni 2+ Cd 2+ Any one or more of the following; more preferably, the source of the tetracoordinate metal ion M is any one or more of zinc sulfate, zinc chloride, zinc nitrate, zinc acetate, ferrous chloride, and nickel chloride;

[0045] In one embodiment of the present invention, the hexacyanide ion [M′(CN)6] is selected from [Fe(CN)6]. 4- [Ru(CN)6] 4- and [Os(CN)6] 4- Any one or more of the following; more preferably, the source of the hexacyanide ion [M′(CN)6] is any one or more of K4[Fe(CN)6], Na4[Fe(CN)6], Li4[Fe(CN)6], H4[Fe(CN)6], Rb4[Fe(CN)6], and (NH4)4[Fe(CN)6];

[0046] In one embodiment of the present invention, in step (1), the solvent of the solution is selected from one or more of water, alcohols and DMF, more preferably water;

[0047] In one embodiment of the present invention, in step (1), the pH value is adjusted by an acidic regulator selected from one or more of hydrochloric acid, acetic acid, sulfuric acid or nitric acid;

[0048] In one embodiment of the present invention, in step (1), the molar concentrations of the M solution and the [M′(CN)6] solution are 0.05–0.5 mol / L.-1 ;

[0049] In one embodiment of the present invention, in step (1), the molar ratio of M to [M′(CN)6] is 1:0.1-2;

[0050] In one embodiment of the present invention, in step (1), the reaction temperature is room temperature or heating; the room temperature is generally considered to be 20±5℃; preferably, the heating temperature is ≤200℃; more preferably, the heating temperature is 50~150℃, and the heating reaction time is 1~72h; even more preferably, the heating temperature is 60~100℃, and the heating time is 3~24h.

[0051] In one embodiment of the present invention, in step (2), the molar ratio of the monovalent cation A to the tetracoordinate metal ion M is ≥0.67; more preferably, the molar ratio is 0.67 to 4.

[0052] In one embodiment of the present invention, in step (2), the concentration of A ions in the solution is 2 mol / L. -1 ;

[0053] In one embodiment of the present invention, in step (2), the monovalent cation A is selected from H+. + NH4 + Li + Na + K + Rb + Cs + ,Fr + Any one or more combinations thereof; more preferably, the aqueous or organic solution containing monovalent cation A is selected from aqueous solutions, alcoholic solutions, and DMF solutions of LiCl, NaCl, KCl, RbCl, CsCl, FrCl, HCl, NH4Cl.

[0054] In one embodiment of the present invention, in step (2), the ion exchange temperature is 25-150°C, preferably 25-60°C; the exchange time is 1-72h; and the number of exchanges is 1-8 times, preferably 1-3 times.

[0055] Furthermore, the above preparation method, after step (2), also includes an activation step to make the water content 0 ≤ n < 1;

[0056] In one embodiment of the invention, the activation step includes a combination of one or more methods selected from depressurization, heating, or gas purging;

[0057] In one embodiment of the present invention, the method of decompression is to maintain the material obtained in step (2) in a vacuum environment of 0.1 to 100 Pa; more preferably, the vacuum is 0.1 to 10 Pa.

[0058] In one embodiment of the present invention, the heating method is to maintain the ambient temperature of the material obtained in step (2) at 50 to 300°C; more preferably, the temperature is 150°C.

[0059] In one embodiment of the present invention, the gas purging method may use a combination of one or more gases selected from nitrogen, argon, helium, air or steam; more preferably nitrogen.

[0060] In one embodiment of the present invention, the activation time is 3 to 48 hours.

[0061] This invention's unique preparation method, combined with an activation method, can produce an activated crystal structure with the P2 / c space group. Compared to materials containing solvent molecules reported by other preparation methods, the solvent molecules (water, ethanol, etc.) in the activated material are completely removed, resulting in a larger dynamic pore volume and specific surface area. Furthermore, the complete removal of solvent molecules releases more cation sites and promotes cation migration to the vicinity of the hexagonal window, thereby utilizing a novel cation-gated effect to achieve high CO2 adsorption capacity, high selectivity, and high adsorption kinetics. In summary, this invention's unique activation method induces a structural transformation in the material while completely removing solvent molecules, significantly improving the material's adsorption capacity, selectivity, and kinetics for CO2 gas.

[0062] The present invention also provides a physical adsorbent for CO2 capture, comprising the framework material as described above or the framework material prepared by the preparation method described above.

[0063] The present invention also provides a method for adsorbing CO2, which involves contacting CO2 gas with a physical adsorbent as described above.

[0064] The present invention also provides a CO2 adsorption device, comprising the physical adsorbent as described above, or using the adsorption method as described above; preferably, the adsorption device includes, but is not limited to, an adsorption bed, an adsorption pipeline, and an adsorption chamber.

[0065] The present invention also provides an application for CO2 adsorption, using the physical adsorbent as described above, or using the adsorption method as described above, or using the adsorption device as described above; preferably, the application for CO2 adsorption includes, but is not limited to, flue gas CO2 capture (CO2 concentration of 3-15%), biogas CO2 capture (CO2 concentration of 15-50%), and confined space CO2 capture (CO2 concentration of 5,000-10,000 ppm).

[0066] Furthermore, the method for adsorbing CO2 is any one of fixed-bed adsorption, moving-bed adsorption, fluidized-bed adsorption, or rotary adsorption, specifically including but not limited to the following steps:

[0067] (1) Under adsorption temperature and pressure, the flue gas generated after combustion is passed into an adsorber containing adsorbent, and nitrogen is detected at the outlet.

[0068] (2) When the carbon dioxide concentration at the outlet is the same as the concentration at the inlet, stop the flue gas from flowing in and desorb the adsorbed carbon dioxide by one or more activation methods such as pressure reduction, heating or gas purging until no carbon dioxide gas can be detected at the outlet, so that the frame material can be regenerated.

[0069] Preferably, the adsorption temperature is 273–473 K and the adsorption pressure is 0–10 bar. More preferably, the adsorption temperature is 273–373 K, within which the separation effect is optimal.

[0070] The beneficial effects of this invention are as follows:

[0071] (1) The unique framework material of this invention contains free monovalent cations and has a unique crystal structure and unit cell parameters. The unique crystal structure and unit cell parameters enable the framework material to have a larger dynamic pore volume and specific surface area, while exposing more monovalent cation sites. The synergistic effect of multiple structural factors can simultaneously achieve extremely high CO2 adsorption capacity and selectivity, especially CO2 / N2 and CO2 / CH4 selectivity. This beneficial effect can be explained by the cation gate effect: the framework material of this invention has a unique dodecahedral cage structure composed of six hexagonal windows and six quadrilateral windows after XRD testing, which are geometric planes composed of multiple atoms and chemical bonds. The dodecahedral cage structure, the windows, and the monovalent cations in the cage work together to enable CO2 molecules to pass through the windows and be adsorbed in large quantities, while other molecules such as N2 and CH4 cannot pass through the windows, thereby achieving extremely high CO2 adsorption capacity and selectivity, especially CO2 / N2 and CO2 / CH4 selectivity, breaking through the trade-off line of adsorption capacity and selectivity of existing materials in the field of CO2 capture.

[0072] (2) The framework material described in this invention exhibits a unique CO2 / H2O co-adsorption mechanism and demonstrates superior moisture resistance compared to traditional zeolites and existing porous framework materials. It exhibits the highest CO2 adsorption capacity and selectivity in carbon dioxide capture applications in humid environments, particularly in low-pressure (≤0.15 bar) and high-humidity (≥40% RH) environments, achieving at least 3.5 mmol g adsorption at 296 K, 0.15 bar, and 40–80% RH. -1 (140cm 3 cm -3 The amount of carbon dioxide adsorbed, and the IAST selectivity (S) for CO2 / N2 (15 / 85, v / v) ads With a value of ≥500, it solves the problem that existing framework materials cannot simultaneously achieve high carbon dioxide selectivity and high carbon dioxide adsorption capacity in low-pressure and high-humidity environments, and its overall performance is superior to the currently reported adsorption materials.

[0073] (3) The preparation method of the present invention employs a unique pH adjustment step and prepares solutions of each component with specific molar concentrations, which can reduce the rate of coordination nucleation of M with [M′(CN)6], improve the crystallization quality and crystal structure integrity, and prepare the highly crystalline framework material with a specific crystal structure of the present invention.

[0074] (4) The unique activation step in the preparation method of the present invention can transform the crystal structure of the material into a P2 / c structure that is more conducive to adsorption. Due to the complete removal of solvent molecules, the activated structure has a larger dynamic pore volume and specific surface area. At the same time, it will expose more cation sites and promote the migration of cations to the vicinity of the pore window. Thus, by utilizing the novel cation-gated effect, higher CO2 adsorption capacity, selectivity and kinetics can be achieved.

[0075] (5) The framework material of the present invention does not contain complex and expensive organic ligands, but is composed of simple and inexpensive metal salts and inorganic ligands, and the raw material cost is low. At the same time, no toxic organic solvents are required during the synthesis process, and water can be used as the solvent, making the synthesis green and environmentally friendly. Furthermore, it can be synthesized by rapid stirring at a lower temperature (50°C), making it easy to mass-produce on a large scale, thus exhibiting excellent engineering performance.

[0076] In summary, the cation-gated metal cyanide framework material provided by this invention exhibits extremely high CO2 adsorption capacity and selectivity in CO2 adsorption applications, maintaining these high levels even under humid conditions. This successfully overcomes the trade-offs in CO2 adsorption capacity and selectivity of existing framework materials, as well as the inability to simultaneously achieve high CO2 selectivity and high CO2 adsorption capacity in low-pressure, high-humidity environments. Furthermore, it possesses excellent moisture resistance and engineering properties, surpassing all currently reported adsorption systems and becoming a new benchmark material. Using this material as a physical adsorbent, it can be applied to flue gas CO2 capture, biogas CO2 capture, and confined space CO2 capture, successfully achieving efficient, low-consumption, and low-cost CO2 capture, providing new methodological guidance for the field of CO2 capture. Attached Figure Description

[0077] Figure 1 shows the trade-off lines for CO2 adsorption capacity and selectivity of porous materials reported in existing literature (Zhou, Y. et al. Science 373, 315–320 (2021); Hu, Y. et al. Adv. Funct. Mater. 33, 2213915 (2023)) and the CO2 adsorption capacity and selectivity performance diagrams of Examples 1, 2, and 3 of the present invention.

[0078] Figure 2 shows the PXRD pattern of the material in Example 1 when it was not activated.

[0079] Figure 3 shows the PXRD pattern of the material after activation in Example 1.

[0080] Figure 4 is a schematic diagram of the structure of the material in Example 1, where A in Figure 4 is a schematic diagram of the structure of the synthetic raw material, B in Figure 4 is a schematic diagram of the crystal structure of the material, and C in Figure 4 is a schematic diagram of the structure of the cage and the window.

[0081] Figure 5 is a schematic diagram of the cation-gated effect.

[0082] Figure 6 is a schematic diagram of the CO2 / H2O co-adsorption crystal structure of the material in Example 1.

[0083] Figure 7 shows the 77K N2 total adsorption curve of the material in Example 1.

[0084] Figure 8 shows the single-component isothermal adsorption curves of CO2 and N2 at 296-373 K for the material in Example 1.

[0085] Figure 9 shows the adsorption heat curves of CO2 and N2 by the material in Example 1.

[0086] Figure 10 is a comparison of the performance of the material in Example 1 with other adsorbent materials.

[0087] Figure 11 shows the material in Example 1 at 200 mL min. -1 The adsorption kinetics curves for 296K 15 / 85CO2 / N2 under the specified flow rate conditions are shown in the figure.

[0088] Figure 12 shows the material in Example 1 at 200 mL min. -1 Desorption kinetics curves under N2 purging conditions at a flow rate of 373K.

[0089] Figure 13 shows the dynamic penetration curves of the material in Example 1 under dry and different humidity conditions for CO2 / N2 (15 / 85, v / v) mixture.

[0090] Figure 14 shows the CO2 adsorption capacity of the material in Example 1 under different humidity conditions.

[0091] Figure 15 shows the dynamic penetration cycle test curve of the material in Example 1 under simulated flue gas containing 50ppm SO2 and 100ppm NO.

[0092] Figure 16 shows the test curve of the material in Example 1 after 50 consecutive adsorption-desorption cycles under the conditions of 15% carbon dioxide concentration, 60% relative humidity, and 423K regeneration temperature.

[0093] Figure 17 shows the PXRD patterns of the material in Example 1 after treatment with acidic water and acidic gases such as SO2 and NO.

[0094] Figure 18 shows the CO2 adsorption curves of the material in Example 1 after treatment under various conditions.

[0095] Figure 19 shows the single-component adsorption isotherms of the material in Example 1 for CO2 and CH4 at 296 K.

[0096] Figure 20 shows the IAST selectivity of the material in Example 1 for CO2 / CH4 (50 / 50, v / v) at 296 K.

[0097] Figure 21 is a dynamic penetration curve of the material in Example 1 under dry conditions to a CO2 / CH4 (50 / 50, v / v) mixture.

[0098] Figure 22 is a SEM image of the single crystal sample of the material in Example 1.

[0099] Figure 23 is a SEM image of the material powder sample in Example 1.

[0100] Figure 24 shows the PXRD patterns of the materials in Examples 1-4.

[0101] Figure 25 shows the 77K N2 total adsorption curve of the material in Example 2.

[0102] Figure 26 shows the single-component isothermal adsorption curves of CO2 and N2 at 296K for the material in Example 2.

[0103] Figure 27 is a CO2 / N2 IAST selectivity curve of the material in Example 2 at 296K.

[0104] Figure 28 is a graph showing the adsorption heat curve of CO2 by the material in Example 2.

[0105] Figure 29 shows the 77K N2 total adsorption curve of the material in Example 3.

[0106] Figure 30 shows the single-component isothermal adsorption curves of CO2 and N2 at 296K for the material in Example 3.

[0107] Figure 31 is a CO2 / N2 IAST selectivity curve of the material in Example 3 at 296K.

[0108] Figure 32 shows the single-component isothermal adsorption curves of CO2 at 296-313K for the material in Example 3.

[0109] Figure 33 is a graph showing the adsorption heat curve of CO2 by the material in Example 3.

[0110] Figure 34 shows the PXRD pattern of the material in Example 5.

[0111] Figure 35 shows the single-component CO2 and N2 isothermal adsorption curves of the material in Example 5 at 296K.

[0112] Figure 36 shows the IAST separation selectivity of the material in Example 5 at 296 K for a CO2 / N2 (10 / 90, v / v) mixture.

[0113] Figure 37 shows the adsorption heat diagram of carbon dioxide and nitrogen at 296 K for the material in Example 5.

[0114] Figure 38 shows the PXRD pattern of the material in Example 9.

[0115] Figure 39 shows the single-component isothermal adsorption curves of CO2 and N2 at 296K for the material in Example 9.

[0116] Figure 40 is a comparison of the CO2 adsorption capacity and corresponding CO2 adsorption heat of the material in Example 9 with other adsorbents at 5,000 ppm.

[0117] Figure 41 is a dynamic penetration curve of the material in Example 9 under dry conditions for a CO2 / N2 mixture with a CO2 concentration of 5,000 ppm.

[0118] Figure 42 is a process diagram of the kilogram-scale synthesis of materials in Example 11.

[0119] Figure 43 shows the PXRD pattern of the material synthesized at the kilogram level in Example 11.

[0120] Figure 44 shows the 296K CO2 single-component isothermal adsorption curve of the kilogram-scale synthetic material in Example 11.

[0121] Figure 45 shows the PXRD pattern of the material in Comparative Example 1.

[0122] Figure 46 shows the single-component adsorption curve of N2 on the material in Comparative Example 1 at 77 K.

[0123] Figure 47 shows the single-component adsorption curve of CO2 for the material in Comparative Example 1 at 296 K.

[0124] Figure 48 shows the dynamic penetration test curves of 15 / 85(v / v) CO2 / N2 at 296 K for the material in Comparative Example 1 under both dry and wet conditions.

[0125] Figure 49 shows the single-component adsorption curve of N2 for the material in Comparative Example 2 at 77K.

[0126] Figure 50 shows the single-component adsorption curve of CO2 for the material in Comparative Example 2 at 296 K.

[0127] Figure 51 shows the dynamic penetration test curves of 15 / 85(v / v) CO2 / N2 at 296K for the material in Comparative Example 2 under both dry and wet conditions.

[0128] Figure 52 shows the PXRD pattern of the material in Comparative Example 3.

[0129] Figure 53 shows the single-component adsorption curve of N2 for the material in Comparative Example 3 at 77 K.

[0130] Figure 54 shows the single-component adsorption curves of CO2 and N2 of the material in Comparative Example 3 at 296 K.

[0131] Figure 55 shows the dynamic penetration test curves of 15 / 85(v / v) CO2 / N2 at 296K for the material in Comparative Example 3 under both dry and wet conditions.

[0132] Figure 56 is a comparison of the CO2 adsorption capacity of the materials in Example 1 and Comparative Examples 1-3 under dry and 40% RH conditions.

[0133] Figure 57 is a comparison of the CO2 adsorption capacity of the materials in Example 1 and Comparative Examples 1-3 under dry and different humidity conditions.

[0134] Figure 58 shows the PXRD pattern of the material in Comparative Example 4. Detailed Implementation

[0135] The present invention will be further illustrated below with reference to the embodiments. However, these embodiments do not limit the scope of protection of the present invention. Based on the technical solution of the present invention, various modifications or variations that can be made by those skilled in the art without creative effort are still within the scope of protection of the present invention.

[0136] The detection method of the present invention is as follows:

[0137] The crystal structure and cell parameters of the framework material of this invention can be obtained by single-crystal X-ray diffraction or powder X-ray diffraction in a vacuum or inert gas atmosphere.

[0138] The dodecahedral pore cage structure, hexagonal pore window structure, and quadrilateral pore window structure of the frame material of the present invention can be obtained from X-ray diffraction (XRD) data by restoration, fitting, or refinement to obtain the structural morphology of the frame material.

[0139] The testing conditions for powder X-ray diffraction (PXRD) were as follows: the radiation source was Cu-Kα radiation. The scanning range is 2–45°, and the scanning speed is 5° / min. -1 .

[0140] The testing conditions for single-crystal X-ray diffraction (SCXRD) were as follows: a Bruker D8 single-crystal diffractometer was used, with a Cu or Mo target as the radiation source, a testing temperature of 200–300 K, and a testing step size of 1–2°. APEX3 software was used to collect, integrate, scale, and average the SCXRD test data, and SHELX software was used for structural analysis and refinement to obtain the material's crystal structure data (CIF file).

[0141] Testing of the dodecahedral-like porous cage structure: Crystal structure data (CIF file) of the material obtained through XRD testing is used to determine the dodecahedral-like porous cage structure of the material using crystal structure processing software. Atoms and chemical bonds are displayed using a ball-and-stick model. The dodecahedral-like porous cage structure refers to a spatial geometry surrounded by atoms and chemical bonds. Its twelve geometric faces include six hexagonal and six quadrilateral geometric faces. Each cage has twelve windows, and the cages are connected by these windows. The monovalent cation A is in a free state within the cage. The windows are divided into quadrilateral and hexagonal windows. The twelve windows of the cage include six quadrilateral and six hexagonal windows, corresponding to the six hexagonal and six quadrilateral geometric faces. The crystal structure processing software includes, but is not limited to, Diamond, Materials Studio, and Olex software.

[0142] Determination of aperture dimensions: The dimensions of quadrilateral and hexagonal apertures were measured using measurement tools in Diamond, Materials Studio, and Olex software. The aperture dimension is defined as the distance from a vertex atom to the opposite vertex atom of a quadrilateral or hexagonal aperture.

[0143] The molar ratio of elements can be determined by a combination of one or more methods, such as atomic absorption spectroscopy (AAS), inductively coupled plasma emission spectroscopy (ICP), X-ray fluorescence spectroscopy (XRF), organic elemental analysis (EA), and energy-dispersive X-ray spectroscopy (EDS).

[0144] BET specific surface area can be determined by carbon dioxide, nitrogen or argon molecules;

[0145] Gas adsorption isotherm test: The adsorption isotherms of different gases on the activated material were tested using an ASAP 2020 physical adsorption instrument, and the temperature of the test sample was maintained constant by a circulating water bath. The test temperature range was 273–373 K, and the pressure range was 0.001–1 bar, to obtain the amount of gas adsorbed by the activated material at specific temperatures and pressures.

[0146] The breakthrough experiments under dry and humid conditions were conducted as follows: The sample was loaded into a stainless steel sample column. The inlet of the sample column was used to introduce a mixed gas, and the outlet was connected to a gas chromatograph to detect the composition and concentration of the outlet gas. Before the test, the sample column was heated to 100°C and purged with nitrogen to remove solvent molecules from the material pores, thus activating the material. Subsequently, under ambient conditions, mixed gas containing carbon dioxide at different humidity levels (relative humidity of 0%, 40%, 60%, and 80%) was introduced into the sample column, and the composition and concentration of the gas exiting at the outlet were recorded. The test was terminated when carbon dioxide was detected exiting at the outlet. Based on the obtained breakthrough curves, the adsorption capacity of the material for carbon dioxide under different humidity conditions could be calculated.

[0147] Naming rules for samples of this invention:

[0148] The structural formula of the frame material of this invention is M. x [M′(CN)6] y ·A z For ease of representation in the embodiments and figures, nH₂O is named ZJU-XXX-A, where ZJU is an abbreviation for Zhejiang University, and XXX represents the metal cyanide framework M. x [M′(CN)6] y A represents a monovalent cation A. zFor example, ZJU-200-K is Zn3[Fe(CN)6]2·K2·nH2O, ZJU-200-Na is Zn3[Fe(CN)6]2·Na2·nH2O, ZJU-201-K ​​is Zn3[Os(CN)6]2·K2·nH2O, and ZJU-202-K is Zn3[Ru(CN)6]2·K2·nH2O, where 0≤n≤10.

[0149] To distinguish between the material before and after activation, ZJU-XXXa-A specifically refers to the material after the activation step (a is an abbreviation for activated, i.e., activated). For example, ZJU-200a-K is Zn3[Fe(CN)6]2·K2·nH2O, where 0≤n<1. The activation step is used to remove solvent molecules such as water molecules from the material pores as much as possible, so that the material exhibits a larger dynamic pore volume and specific surface area, and releases more cation sites, thereby enabling it to be used for gas adsorption, especially CO2 adsorption.

[0150] Example 1 ZJU-200-K

[0151] Material preparation: Prepare 9 mL of 0.05 M zinc sulfate aqueous solution and 6 mL of 0.05 M potassium ferrocyanide aqueous solution, and adjust the pH of the two solutions to 6-7 with 2 M CH3COOH. Then mix the two solutions and carry out a hydrothermal reaction at 60℃ for 3 hours. After the reaction is completed, filter and wash to obtain the intermediate product. Then soak the intermediate product in 9 mL of 0.2 M potassium chloride aqueous solution and place it at 60℃ for 2 days and 3 times. Then filter and wash to obtain the powder product, ZJU-200-K.

[0152] Structural characterization of the unactivated sample ZJU-200-K: The PXRD results of the unactivated ZJU-200-K are shown as the red spectral line in Figure 2, with single peaks at 2θ = 16.4°, 19.7°, and 21.8°, and double peaks at 2θ = 13.5–14.2° and 24.3–24.6°. The PXRD spectrum of the unactivated sample can be tested in an air environment.

[0153] The SCXRD test data of ZJU-200-K were collected, integrated, scaled, and averaged using APEX3 software, and the structure was analyzed and refined using SHELX software to obtain the crystal structure data of ZJU-200-K, and its crystal space group was confirmed to be [missing information]. Space group (space group number 167), cell parameters are The structural formula is Zn3[Fe(CN)6]2·K2·8H2O. Based on the obtained crystal structure data, the corresponding PXRD spectrum (black lines in Figure 2) was simulated using Materials Studio software. Comparing the black simulated spectrum with the red experimental spectrum in Figure 2, the characteristic peaks of the two are basically consistent, confirming the reliability of the ZJU-200-K crystal structure data.

[0154] Structural characterization of the activated sample ZJU-200a-K: ZJU-200-K was further activated by first evacuating the sample to room temperature under vacuum for 12 hours, then evacuating it to 150°C under vacuum for 4 hours, resulting in fully activated ZJU-200a-K. The PXRD pattern of ZJU-200a-K is shown as the red line in Figure 3, with single peaks at 2θ = 10°, 14.5°, and 16.6°, and a double peak at 2θ = 20.1°. The PXRD pattern of the activated sample can be tested in an inert atmosphere. The activation process aims to remove water molecules from the material as much as possible; complete activation means that no water molecules are detectable in the material. The detection can be performed using PXRD and SCXRD tests.

[0155] SCXRD test data of ZJU-200a-K were collected, integrated, scaled, and averaged using APEX3 software, and structural analysis and refinement were performed using SHELX software to obtain the crystal structure data of ZJU-200a-K. Its crystal space group was confirmed as P2 / c (space group number 13), and its cell parameters were determined to be... The structural formula is Zn3[Fe(CN)6]2·K2. This crystal structure and cell parameters enable the material to have a larger dynamic pore volume and specific surface area, while exposing more monovalent cation sites. The synergistic effect of multiple structural factors enables both high CO2 / N2 selectivity and CO2 adsorption capacity. Based on the obtained crystal structure data, the corresponding PXRD spectrum (black lines in Figure 3) was simulated using Materials Studio software. Comparing the black simulated spectrum with the red experimental spectrum in Figure 3, the characteristic peaks of the two are basically consistent, confirming the reliability of the ZJU-200a-K crystal structure data.

[0156] Based on the crystal structure data of ZJU-200a-K, the dodecahedral porous cage structure of ZJU-200a-K was determined using Diamond software (Figure 4). Each cage (yellow sphere in Figure 4) has twelve windows: six hexagonal windows (6R windows) and six quadrilateral windows (4R windows). The monovalent cation A is in a free state within the cage. The cage is a geometric body formed by atoms and chemical bonds, and the windows are the geometric faces that make up the body. The diameter of the hexagonal windows was determined using the measurement tools in Diamond software. The diameter of the quadrilateral window is Quadrilateral windows, due to their small size, cannot allow guest molecules (such as CO2 and N2 gas molecules) to pass through and only serve as a supporting framework. Hexagonal windows, on the other hand, allow guest molecules to pass through and can serve as transport windows for guest molecules. Furthermore, both hexagonal and quadrilateral windows are rigid structures, and their sizes remain largely unchanged regardless of external conditions.

[0157] Cation-gating effect study: The unique crystal structure parameters and dodecahedral-like porous cage structure of ZJU-200a-K endow it with a cation-gating effect. To visually represent this effect, a schematic diagram of the cation-gating effect was constructed using Diamond software based on the crystal structure data of ZJU-200a-K (Figure 5). As shown in the figure, the cation-gating effect refers to the fact that the dodecahedral-like porous cage can accommodate guest molecules, while the hexagonal pores that allow guest molecules to pass through are equivalent to "door frames." Monovalent cations are located near the hexagonal pores and can selectively allow guest molecules to enter, thus having a "gating" effect. CO2 molecules can interact strongly with monovalent cations, causing the monovalent cations to shift, which is equivalent to opening the cation gate, allowing CO2 molecules to enter the porous cage through the hexagonal pores. However, N2 molecules cannot interact strongly with monovalent cations and cannot open the cation gate, thus making it difficult for them to enter the porous cage. This unique cation-gating effect, as a novel CO2 adsorption and separation mechanism, is beneficial for simultaneously achieving extremely high CO2 / N2 selectivity and CO2 adsorption capacity.

[0158] The mole fractions of each element in ZJU-200a-K were obtained by AAS, ICP and EA analysis as follows: Zn mole fraction 10%, Fe mole fraction 6.5%, C mole fraction 39%, N mole fraction 39%, K mole fraction 6.5%, H mole fraction 0%, and O mole fraction 0%.

[0159] Study on CO2 / H2O co-adsorption mechanism: A single crystal of ZJU-200a-K was placed in a capillary glass tube with an inner diameter of 0.1 mm. The crystal was subjected to vacuum treatment at 393 K for 4 hours. Then, the capillary glass tube was pressurized to 1 bar with a CO2 / H2O mixed gas and sealed, and transferred to a single crystal diffractometer for testing. The SCXRD test data were collected, integrated, scaled, and averaged using APEX3 software, and the structure was analyzed and refined using SHELX software to obtain the crystal structure data of CO2 / H2O co-adsorption of ZJU-200-K. A schematic diagram of CO2 / H2O co-adsorption of ZJU-200-K was constructed using Diamond software (Figure 6). As shown in the figure, the monovalent cations in the pore cages of ZJU-200a-K can serve as co-adsorption sites for CO2 / H2O. That is, after adsorbing H2O, the cations can still adsorb CO2. This overcomes the problem that the adsorption sites of traditional adsorption materials cannot adsorb CO2 after adsorbing H2O. As a result, ZJU-200-K can still have extremely high CO2 adsorption capacity and selectivity in high humidity environments (≥40%RH), which is superior to the current material system.

[0160] CO2 adsorption capacity: A total nitrogen adsorption test was performed on ZJU-200a-K at 77K, and the results are shown in Figure 7. Further calculations showed that the BET specific surface area of ​​ZJU-200a-K was 633.7 m². 2 g -1 This demonstrates that the material has good porosity and can accommodate a large number of CO2 molecules.

[0161] The single-component adsorption curves of ZJU-200a-K for CO2 and N2 were tested under conditions of 296–373 K, and the results are shown in Figure 8. At 296 K and 1 bar, the adsorption capacity of ZJU-200a-K for CO2 was 5.02 mmol g. -1 (196cm 3 cm -3 This value exceeds that of currently reported materials, with an N2 adsorption capacity of only 0.17 mmol g. -1 (6.6cm 3 cm -3 The ratio of CO2 to N2 adsorption is 30.

[0162] IAST Selectivity: The IAST selectivity of ZJU-200a-K for CO2 / N2 (15 / 85, v / v) mixture was further calculated according to the formulas listed in the detection method. The corresponding IAST calculation parameters are shown in Table 1.

[0163] Table 1: Parameters for IAST selectivity calculation obtained by ZJU-200a-K based on the Dual Site Langmuir Freundlich model fitting.

[0164] Based on the parameters in Table 1, the IAST selectivity of ZJU-200a-K for CO2 / N2 (15 / 85, v / v) at 296 K and 1 bar is calculated to be 5.6 × 10⁻⁶. 6 This value far exceeds that of currently reported materials. This simultaneous high CO2 adsorption capacity and CO2 / N2 selectivity break through the trade-off line of existing technologies (see Figure 1), confirming the cation-gated effect of ZJU-200a-K.

[0165] ZJU-200a-K successfully solves the problem that existing technologies cannot simultaneously achieve high carbon dioxide selectivity and high carbon dioxide adsorption capacity, with both high adsorption capacity and high adsorption capacity. The performance comparison with other benchmark materials is shown in Figure 9, which confirms the technological breakthrough brought about by the cation-gated framework material created in this invention.

[0166] Based on the single-component adsorption curves at different temperatures, the adsorption heats of ZJU-200a-K for CO2 and N2 were calculated (Figure 10). It can be seen that the initial adsorption heat of ZJU-200a-K for CO2 is 43.6 kJ mol. -1 It is significantly higher than the initial adsorption heat of N2 (18.7 kJ mol). -1 ).

[0167] The adsorption-desorption kinetics of CO2 by ZJU-200a-K were further tested, as shown in Figures 11 and 12. For a mixed gas of 15 / 85 CO2 / N2 at room temperature, ZJU-200a-K approached adsorption saturation in about 2.5 min; under nitrogen purging conditions of 373 K, ZJU-200a-K was basically completely desorbed within 8 min. These test results indicate that ZJU-200a-K has excellent CO2 adsorption-desorption kinetics.

[0168] Breakthrough test and moisture resistance: A dynamic fixed-bed breakthrough test was used to evaluate the actual separation effect of ZJU-200a-K on a 15 / 85 CO2 / N2 mixed gas. As shown in Figure 13, CO2 at 212 min g -1 The calculated dynamic CO2 adsorption capacity is 4.30 mmol g. -1 .

[0169] To evaluate the material's resistance to moisture, a humid 15 / 85 CO2 / N2 mixed gas was passed into the adsorption bed until CO2 was observed to escape. The dynamic CO2 adsorption capacity at high relative humidity (80% RH) was determined to be 4.1 mmol g. -1 The attenuation rate was less than 10% compared to dry conditions. The nitrogen adsorption capacity was 0.01 mmol g. -1 The IAST selectivity calculation reached 2323, further confirming that the material has a strong CO2 adsorption capacity even in humid environments. The CO2 adsorption capacity at different humidity levels is shown in Figure 14, indicating that the material has a high CO2 adsorption capacity in high-humidity flue gas CO2 capture applications. Cyclic breakthrough experiments on a mixed gas containing 50 ppm SO2 and 100 ppm NO showed that ZJU-200a-K maintained good separation performance even under conditions containing acidic gas impurities (see Figure 15).

[0170] Stability Testing: The cyclic stability of ZJU-200-K was tested. The test procedure included CO2 adsorption under humid CO2 / N2 (15 / 85, v / v) conditions and desorption via heating in an N2 stream at 423 K. This process was carried out continuously for 50 cycles (Figure 16). The results showed that there was no significant loss in the CO2 adsorption capacity of the material, indicating that ZJU-200a-K has excellent cyclic stability under humid conditions.

[0171] To characterize the chemical stability of ZJU-200-K, freshly synthesized samples were exposed to acidic gases (50 ppm SO2 and 100 ppm NO) or immersed in boiling water, pH=3 and pH=11 solutions for 3 days. The PXRD patterns and CO2 adsorption curves of the samples were then tested, and the results are shown in Figures 17 and 18. It can be seen that the position and intensity of the diffraction peaks and the CO2 adsorption performance remained basically unchanged, indicating that it has excellent chemical stability.

[0172] CO2 / CH4 Selectivity in Biogas CO2 Capture Applications: The main component of biogas is methane (CH4), typically containing 50%–80% CH4, 15%–50% CO2, and 0%–5% N2. To evaluate the material's ability to selectively capture CO2 from biogas, we determined the adsorption isotherms of ZJU-200a-K for carbon dioxide and methane (Figure 19). Further calculations showed that ZJU-200a-K exhibited an IAST selectivity of 1149 for a CO2 / CH4 (50 / 50, v / v) mixture (Figure 20), indicating that the material can selectively adsorb CO2 from biogas. Dynamic fixed-bed breakthrough experiments with a CO2 / CH4 (50 / 50, v / v) mixture demonstrated that ZJU-200a-K can efficiently capture CO2 from the CO2 / CH4 mixture (Figure 21).

[0173] Microstructure: To characterize the morphology of ZJU-200-K, SEM images of single-crystal and powder samples were taken (Figures 22 and 23). As shown in the figures, well-crystallized ZJU-200-K can be in the form of bulk particles, with single-crystal particle size greater than 20 μm and powder particle size greater than 1 μm.

[0174] Example 2 ZJU-200-Na

[0175] Material preparation: Prepare 6 mL of 1M zinc sulfate aqueous solution and 9 mL of 1M sodium ferrocyanide aqueous solution, and adjust the pH of the two solutions to 5-6 with 2M CH3COOH. Then, mix the two solutions and carry out a solvothermal reaction at 80℃ for 6 hours. After the reaction is completed, filter, wash and dry to obtain the intermediate product. Then, soak the intermediate product in 6 mL of 0.67M sodium chloride aqueous solution and place it at 25℃ for 2 days and 3 times. Then filter and wash to obtain the powder product ZJU-200-Na.

[0176] Structural Characterization: Using the method described in Example 1, the structural formula of ZJU-200-Na was determined to be Zn3[Fe(CN)6]2·Na2·8H2O. The PXRD pattern of ZJU-200-Na is shown in Figure 24. It has single peaks at 2θ = 16.3° and 19.7°, and double peaks at 13.5–14.2°, 21.5–21.9°, and 24.3–24.7°. ZJU-200-Na was activated by first evacuating the sample at room temperature for 12 hours, and then evacuating it at 165°C for 4 hours, resulting in the fully activated material ZJU-200a-Na with the structural formula Zn3[Fe(CN)6]2·Na2, whose crystal structure is similar to that of ZJU-200a-K.

[0177] The N2 adsorption curve of ZJU-200a-Na at 77 K was tested, and the results are shown in Figure 25. The calculated BET specific surface area is 31 m². 2 g -1 Therefore, the 273K CO2 adsorption test was used to characterize the BET specific surface area (644m²) of the material. 2 g -1 ).

[0178] CO2 adsorption capacity and selectivity: The single-component adsorption curves of CO2 and N2 for ZJU-200a-Na at 296 K were tested (Figure 26). At 296 K and 1 bar, the adsorption capacity of CO2 for ZJU-200a-Na was 5.76 mmol g. -1 The adsorption capacity for N2 is only 0.08 mmol g. -1The CO2 to N2 adsorption ratio was 72. As shown in Figure 27, the IAST selectivity of ZJU-200a-Na for CO2 / N2 (15 / 85, v / v) was calculated based on the adsorption curve at 296 K, reaching as high as 1211 at 1 bar. Its CO2 adsorption capacity and selectivity broke through the trade-off line of the prior art (see Figure 1), proving the cation-gated effect. The adsorption heat of CO2 (41.4 kJ mol) was calculated based on the adsorption curves of the material at different temperatures. -1 (Figure 28).

[0179] Example 3 ZJU-200-Rb

[0180] Material preparation: 6 mL of 0.5 M zinc sulfate aqueous solution and 12 mL of 0.5 M sodium ferrocyanide aqueous solution were respectively adjusted to pH 4-5 with 2 M acetic acid. The mixture was stirred and reacted at 100 °C for 72 hours. After the reaction was completed, the powder sample was obtained by filtration, washing and drying. The powder sample was then immersed in 6 mL of 0.5 M rubidium chloride solution and placed in a 60 °C oven for 3 days. During this period, the ions were exchanged three times with fresh rubidium chloride solution. After the ion exchange was completed, the powder sample ZJU-200-Rb was obtained by filtration, washing and drying.

[0181] Structural Characterization: Using the method described in Example 1, the structural formula of ZJU-200-Rb was determined to be Zn3[Fe(CN)6]2·Rb2·8H2O. The PXRD results of ZJU-200-Rb are shown in Figure 24. It exhibits a single peak at 2θ = 16.3° and 19.7°, and double peaks at 13.5–14.2°, 21.6–21.9°, and 24.3–24.7°. ZJU-200-Rb was activated by first evacuating the sample at room temperature for 12 hours, then evacuating it at 120°C for 4 hours, resulting in the fully activated material ZJU-200a-Rb with the structural formula Zn3[Fe(CN)6]2·Rb2, whose crystal structure is similar to that of ZJU-200a-K.

[0182] The N2 adsorption curve of ZJU-200a-Rb at 77 K was tested, and the results are shown in Figure 29. The calculated BET specific surface area is 566 m². 2 g -1 .

[0183] CO2 adsorption capacity and selectivity: The single-component adsorption curves of CO2 and N2 by ZJU-200a-Rb at 296 K were tested (Figure 30). At 296 K and 1 bar, the adsorption capacity of CO2 by ZJU-200a-Rb was 3.92 mmol g. -1 The adsorption capacity for N2 is only 0.20 mmol g. -1The CO2 to N2 adsorption ratio was 20. As shown in Figure 31, the IAST selectivity of ZJU-200a-Rb for CO2 / N2 (15 / 85, v / v) was calculated based on the adsorption curve at 296 K, and it was 602 at 1 bar. Its CO2 adsorption capacity and selectivity broke through the trade-off line of the existing technology (see Figure 1), proving the cation-gated effect. The single-component adsorption curves of ZJU-200a-Rb for CO2 at 296 K, 313 K and 333 K were tested (Figure 32), and the adsorption heat of the material for CO2 (37.4 kJ mol) was calculated. -1 (Figure 33).

[0184] Example 4 ZJU-200-Li

[0185] Prepare 10 mL of 0.1 M Li₄[Fe(CN)₆] solution; mix it with 1 mL of 0.1 M zinc sulfate aqueous solution with pH adjusted to 6-7 using acetic acid, and stir the mixture at 50 °C for 72 h. After the reaction, filter, wash, and dry to obtain an intermediate product; then soak the intermediate product in 10 mL of 0.067 M lithium chloride aqueous solution, place it at 60 °C for 2 days and exchange 3 times, then filter and wash to obtain the powder product ZJU-200-Li. Test according to the method in Example 1, and determine the structural formula of ZJU-200-Li as Zn₃[Fe(CN)₆]₂·Li₂·8H₂O. Activate the material by first vacuuming the sample at room temperature for 12 hours, then vacuuming at 105 °C for 4 hours to obtain the fully activated material ZJU-200a-Li, with the structural formula Zn₃[Fe(CN)₆]₂·Li₂, whose crystal structure is similar to ZJU-200a-K.

[0186] Example 5 ZJU-200-NH4

[0187] Prepare 9 mL of 0.05 M zinc sulfate aqueous solution and 6 mL of 0.05 M sodium ferrocyanide aqueous solution. Adjust the pH to 6-7 with 2 M acetic acid and react at 150 °C for 1 h. After the reaction, filter, wash and dry to obtain the intermediate product. Then soak the powder sample in 9 mL of 0.2 M ammonium chloride solution and place it in a 150 °C oven for 1 h. During this time, exchange the ions once with fresh ammonium chloride solution. After the ion exchange is completed, filter, wash and dry to obtain the powder sample ZJU-200-NH4. Test according to the method in Example 1 to determine the structural formula of ZJU-200-NH4 as Zn3[Fe(CN)6]2·(NH4)2·6H2O. The PXRD results of ZJU-200-NH4 are shown in Figure 34. It has single peaks at 2θ = 16.2°, 19.7°, and 21.7°, and double peaks at 2θ = 13.6–14.1° and 24.3–24.6°. The material was activated by first evacuating the sample to room temperature for 12 hours, then evacuating it to 120°C for 4 hours, resulting in fully activated ZJU-200a-NH4 with the structural formula Zn3[Fe(CN)6]2·(NH4)2, whose crystal structure is similar to that of ZJU-200a-K.

[0188] The single-component adsorption curves of carbon dioxide and nitrogen for ZJU-200a-NH4 at 296 K were tested, and the results are shown in Figure 35. The CO2 adsorption capacity at 296 K and 1 bar was 4.15 mmol g. -1 The IAST separation ratio was 2348 (Figure 36); as shown in Figure 37, the calculated heat of adsorption of carbon dioxide was 37.1 kJ / mol. -1 The heat of adsorption for nitrogen is 27.6 kJ / mol. -1 The low heat of carbon dioxide adsorption is very beneficial for the recycling and regeneration of materials.

[0189] Example 6 ZJU-200-H

[0190] 2 mmol of potassium hexacyanoferrate was dissolved in 10 mL of water, and 1.2 mL of hydrochloric acid was added. After cooling to 0 °C, 10 mL of diethyl ether was added to precipitate the product. The precipitate was dissolved in 8 mL of methanol and then precipitated with another 10 mL of diethyl ether. The mixture was filtered three times to obtain H4[Fe(CN)6]. 9 mL of 0.1 M zinc sulfate aqueous solution was adjusted to pH 4-5 with 2 M CH3COOH, and then added dropwise to 6 mL of 0.1 M H4[Fe(CN)6] aqueous solution at 60 °C. The mixture was stirred continuously for 3 hours. After the reaction was completed, the product was filtered, washed, and dried to obtain the powdered product ZJU-200-H. The structure of ZJU-200-H was determined to be Zn3[Fe(CN)6]2·H2·8H2O according to the method in Example 1. To activate the material, the sample was first vacuumed at room temperature for 12 hours, and then vacuumed at 105℃ for 4 hours to obtain the fully activated material ZJU-200a-H, with the structural formula Zn3[Fe(CN)6]2·H2, whose crystal structure is similar to that of ZJU-200a-K.

[0191] Example 7 ZJU-200-Cs

[0192] Prepare 10 mL of 0.1 M zinc sulfate aqueous solution and 10 mL of 0.1 M sodium ferrocyanide aqueous solution. Then, adjust the pH of the solutions to 6-7 with 2 M CH3COOH. Mix the two solutions and carry out a hydrothermal reaction at 70 °C. After the reaction, filter, wash, and dry to obtain a powder sample. Immerse the powder sample in 10 mL of 0.4 M cesium chloride solution and place it in a 60 °C oven for 2 days. During this period, exchange the ions with fresh cesium chloride solution 8 times. After the ion exchange is completed, filter, wash, and dry to obtain the powder sample ZJU-200-Cs. Test according to the method in Example 1, and determine the structural formula of ZJU-200-H as Zn3[Fe(CN)6]2·Cs2·8H2O. To activate the material, the sample was first vacuumed at room temperature for 12 hours, and then vacuumed at 105℃ for 4 hours to obtain the fully activated material ZJU-200a-Cs, with the structural formula Zn3[Fe(CN)6]2·Cs2, whose crystal structure is similar to that of ZJU-200a-K.

[0193] Example 8 ZJU-201-K

[0194] Prepare 10 mL of 0.1 M zinc sulfate aqueous solution and 10 mL of 0.1 M potassium hexacyanosmium tetroxide aqueous solution. Then, adjust the pH of the solutions to 6-7 with 2 M CH3COOH. Mix the two solutions and carry out a hydrothermal reaction at 70 °C. After the reaction, filter, wash, and dry to obtain a powder sample. Immerse the powder sample in 10 mL of 1 M potassium chloride aqueous solution and perform ion exchange at 60 °C. Repeat this ion exchange operation three times over two days. After the ion exchange is complete, filter, wash, and dry to obtain the powder sample ZJU-201-K. Test according to the method in Example 1, and the structural formula of ZJU-201-K ​​is determined to be Zn3[Os(CN)6]2·K2·8H2O. To activate the material, the sample was first vacuumed at room temperature for 12 hours, and then vacuumed at 105℃ for 4 hours to obtain the fully activated material ZJU-201a-K with the structural formula Zn3[Os(CN)6]2·K2, whose crystal structure is similar to that of ZJU-200a-K.

[0195] Example 9 ZJU-202-K

[0196] Materials Preparation: 9 mL of 0.05 M zinc sulfate aqueous solution and 6 mL of 0.05 M potassium hexacyanorubate aqueous solution were prepared separately. The two solutions were then mixed and subjected to a hydrothermal reaction at 50 °C with continuous stirring for 5 hours. After the reaction was complete, the intermediate product was separated by filtration and thoroughly washed. The obtained intermediate product was then immersed in 9 mL of 2 M potassium chloride aqueous solution for ion exchange at 60 °C. This ion exchange operation was repeated three times over two days. Finally, after filtration and washing, the powdered product ZJU-202-K was obtained.

[0197] Structural characterization: Following the method described in Example 1, the structural formula of ZJU-202-K was determined to be Zn3[Ru(CN)6]2·K2·8H2O. The PXRD results of the unactivated ZJU-202-K are shown in Figure 38. It exhibits single peaks at 2θ = 16.5°, 19.7°, 21.8°, and 23.9°, and double peaks in the range of 13.5°–14.2°.

[0198] To activate ZJU-202-K, the sample was evacuated at room temperature for 12 hours, followed by evacuation at 100°C for another 12 hours, thus obtaining the activated material ZJU-202a-K with the structural formula Zn3[Ru(CN)6]2·K2. The structure of ZJU-202a-K is similar to that of ZJU-200a-K.

[0199] The nitrogen adsorption isotherm of ZJU-202a-K was tested at 77 K. Based on the test results, its BET specific surface area was calculated to be 654 m². 2 g -1 .

[0200] CO2 Adsorption Capacity and Selectivity: The single-component adsorption curves of carbon dioxide and nitrogen for ZJU-202a-K at 296 K were tested (Figure 39). At 296 K and 1 bar, the CO2 adsorption capacity of ZJU-202a-K was 4.98 mmol g. -1 However, the adsorption capacity for N2 was only 0.32 mmol g. -1 Under conditions of 296 K and 0.01 bar (i.e., 10,000 ppm), ZJU-202a-K can adsorb up to 2.16 mmol g of CO2. -1 At 0.005 bar (i.e., 5,000 ppm), the material still adsorbs as much as 1.44 mmol g of CO2. -1 This fully demonstrates the excellent CO2 adsorption performance of ZJU-202a-K under low-pressure conditions.

[0201] Calculations showed that, at 296 K, ZJU-202a-K exhibited IAST selectivity of 2859 and 2771 for CO / N2 mixtures at concentrations of 5,000 ppm and 10,000 ppm, respectively. Furthermore, the adsorption heats of ZJU-202a-K for CO2 and N2 were 39.3 kJ·mol⁻¹, respectively. -1 and 17.7 kJ·mol -1 As shown in Figure 40, the CO2 adsorption capacity and adsorption heat value of the current material under 5,000 ppm conditions are compared. ZJU-202a-K simultaneously achieves high CO2 adsorption capacity and low regeneration energy consumption under low pressure conditions.

[0202] Breakthrough test and moisture resistance: To simulate the CO2 capture process in a confined space, a dynamic fixed-bed breakthrough test was conducted to evaluate the separation performance of ZJU-202a-K for a CO2 / N2 mixture with a CO2 content of 5,000 ppm. As shown in Figure 41, the breakthrough performance was tested at 530 min g. -1 CO2 begins to escape, and the calculated CO2 adsorption capacity is 1.4 mmol·g. -1 (51.8cm 3 cm -3 This indicates that ZJU-202a-K can efficiently capture CO2 from a confined space.

[0203] Dynamic fixed-bed breakthrough experiments under humid conditions show that ZJU-202a-K can still efficiently capture CO2 from a CO2 / N2 mixed gas of 5,000 ppm under 40% RH conditions, with a corresponding CO2 adsorption capacity attenuation rate of less than 15%.

[0204] Similarly, after structural characterization and performance testing, ZJU-200a-Na, ZJU-200a-Rb, ZJU-200a-Li, ZJU-200a-NH4, ZJU-200a-H, ZJU-200a-Cs, ZJU-201a-K, and ZJU-202a-K of Examples 2-9 also have the crystal structure described in this invention. They all exhibit excellent CO2 adsorption capacity and selectivity, as well as excellent moisture resistance in gas adsorption tests.

[0205] Example 10 M x [M′(CN)6] y ·A z Regulation of M in nH2O

[0206] The synthesis method was followed as described in Example 1, with the only difference being that the zinc sulfate aqueous solution was replaced with ferrous zinc sulfate aqueous solution, cobalt sulfate aqueous solution, copper sulfate aqueous solution, nickel sulfate aqueous solution, and cadmium sulfate aqueous solution, respectively. The SCXRD and PXRD data of the fully activated samples were tested according to the method in Example 1, confirming the activated structural formulas of these materials as Fe3[Fe(CN)6]2·K2, Co3[Fe(CN)6]2·K2, Cu3[Fe(CN)6]2·K2, Ni3[Fe(CN)6]2·K2, and Cd3[Fe(CN)6]2·K2, respectively. The crystal structures of these materials are similar to those of ZJU-200a-K. Similarly, the CO2 adsorption isotherms and mixed gas breakthrough curves of the above materials were tested according to the method in Example 1. The results showed that these materials all exhibited excellent CO2 adsorption capacity and selectivity, and possessed excellent moisture resistance.

[0207] As shown in Examples 1-10, the metal ions M selected in this invention are all tetracoordinate metal ions, with highly similar coordination abilities and coordination configurations, forming a similar framework structure after coordination with the hexacyanometallic ion M′(CN)6. The cations A selected in this invention are all monovalent cations, and all can be distributed in a free state within the pores. Therefore, by utilizing the synergistic effect of the structural characteristics of the tetracoordinate metal ion M, the hexacyanometallic ion M′(CN)6, and the monovalent cation A, the material M of this invention… x [M′(CN)6] y ·A z nH₂O possesses specific crystal structure parameters and a dodecahedral porous cage structure; even when the types of M, M′, and A are adjusted within the scope defined by this invention, Mx [M′(CN)6] y ·A z The structural parameters of nH2O will not change significantly beyond the scope of this invention. For example, M is selected from Zn. 2+ Fe 2+ Co 2+ Cu 2+ Ni 2+ Cd 2+ Any one or more combinations thereof; [M′(CN)6] is selected from [Fe(CN)6]. 4- [Ru(CN)6] 4- and [Os(CN)6] 4- Any one or more combinations of H; A is selected from H + NH4 + Li + Na + K + Rb + Cs + ,Fr + Any one or more combinations thereof; thus obtaining M x [M′(CN)6] y ·A z All nH2O materials possess the crystal structure parameters and dodecahedral-like porous cage structure described in this invention. Furthermore, the unique crystal structure parameters and dodecahedral-like porous cage structure of these materials enable cation-gated effects, thereby exhibiting the excellent CO2 adsorption capacity, selectivity, and moisture resistance described in this invention.

[0208] In summary, the framework materials described in this invention can solve the problems of not being able to simultaneously achieve high carbon dioxide selectivity and high carbon dioxide adsorption capacity in low-pressure, high-humidity environments, as well as the poor moisture resistance of framework materials. Their overall performance is superior to that of currently reported adsorption materials.

[0209] Example 11 Industrial Scale-up Test

[0210] Taking the sample from Example 1 as an example, ZJU-200-K was prepared at the kilogram level. Strictly following the raw materials and process parameters of Example 1, a specific large-scale reaction device was used, and the amount of each reactant was increased proportionally by 1500 times. The sample was activated according to the method of Example 1, and tested according to the test methods of various parameters in Example 1. The synthesis of kilogram-level ZJU-200-K powder samples was successfully achieved (Figure 42). The position and intensity of the diffraction peaks in the PXRD pattern showed almost no change (Figure 43), and the change in CO2 adsorption was less than 1% (Figure 44). This proves that the kilogram-level sample still maintains the original crystal structure and adsorption performance, thus demonstrating that the material and preparation method of the present invention have the potential for industrial application.

[0211] Comparative Example 1: CALF-20

[0212] CALF-20, the CO2-capturing MOF material with the best overall performance to date, was selected for comparison (J.-B. Lin, et al. Science 374, 1464-1469 (2021)). Following the literature method, 6.60 g of zinc oxalate, 5.00 g of 1,2,4-triazole, and 66.0 mL of methanol were added to a 100 mL autoclave. The resulting reaction solution was stirred for ten minutes and then stored in a high-temperature oven at 180 °C for 48 hours. The resulting precipitate was filtered, washed repeatedly with methanol, and dried to obtain CALF-20. The PXRD pattern, 77 K N2 adsorption curve, and 296 K CO2 adsorption curve of CALF-20 are shown in Figures 45-47, consistent with the literature results, proving the successful synthesis of the material; its CO2 adsorption capacity at 296 K and 0.15 bar was only 2.7 mmol g. -1 The reported CO2 / N2 IAST selectivity was 230, which is lower than that of the material in Example 1 of this invention.

[0213] Dynamic breakthrough experiments were used to evaluate the separation performance of CALF-20 for a 15 / 85 CO2 / N2 mixture under dry and wet conditions, as shown in Figure 48. The CO2 capture capacity of CALF-20 under dry conditions was 2.6 mmol g. -1 It can maintain 68% (CO2 adsorption capacity of 1.77 mmol g) under 40% RH conditions. -1 Its moisture resistance is significantly weaker than that of the material in Example 1 of this invention.

[0214] Comparative Example 2: Zeolite 13X

[0215] Commercial CO2 adsorbent zeolite 13X was selected for comparison. The test results of the 77K N2 adsorption curve and the 296K CO2 adsorption curve of zeolite 13X are shown in Figures 49 and 50; the CO2 adsorption capacity of zeolite 13X at 296K and 0.15 bar was only 2.7 mmol g. -1 The IAST selectivity of 15 / 85CO2 / N2 was 146, which is lower than that of the material in Example 1 of this invention.

[0216] Dynamic breakthrough experiments were used to evaluate the separation efficiency of zeolite 13X for a 15 / 85 CO2 / N2 mixture under dry and wet conditions. As shown in Figure 51, the CO2 capture capacity of zeolite 13X under dry conditions was 2.5 mmol g. -1 The CO2 capacity decayed by more than 90% under 40% RH humidity conditions, and its moisture resistance was extremely poor, significantly weaker than the material in Example 1 of this invention.

[0217] Comparative Example 3 Ni-MOF-74

[0218] The classic CO2-capturing MOF material Ni-MOF-74 was selected for comparison (SR Caskey, et al. J. Am. Chem. Soc. 2008, 130, 10870–10871). Following the literature method, 142.5 mg of nickel nitrate and 33.6 mg of 2,5-dihydroxyterephthalic acid (H4dobdc) were dissolved in a 15:1:1 (v / v / v) DMF-ethanol-water mixture (15 mL). The mixture was sonicated for 30 min and then transferred to a 20 mL reactor. After reacting at 398 K for 26 h, the product was obtained by filtration, washing, and drying.

[0219] The PXRD pattern, 77K N2 adsorption curve, and 296K CO2 adsorption curve of Ni-MOF-74 are shown in Figures 52-54, which are consistent with the results reported in the literature, proving the successful synthesis of the material; its CO2 adsorption capacity at 296K and 0.15 bar is 3.71 mmol g. -1 The selectivity of 15 / 85CO2 / N2IAST is only 44, and both the adsorption capacity and selectivity are lower than those of the material in Example 1 of this invention.

[0220] Dynamic breakthrough experiments were used to evaluate the separation performance of Ni-MOF-74 for a 15 / 85 CO2 / N2 mixture under dry and humid conditions. As shown in Figure 55, the CO2 capture capacity of Ni-MOF-74 under 40% RH humid conditions decreased by more than 90% compared to the dry conditions, which is significantly weaker than the material in Example 1 of this invention.

[0221] The comparison results of CO2 adsorption capacity at 0.15 bar for the materials of Example 1 and Comparative Examples 1-3 under dry and different humidity conditions are shown in Figures 56 and 57. The comparison results show that the CO2 adsorption capacity of the material of Example 1 is significantly higher than that of the comparative materials under both dry and humid environments, which fully demonstrates that the material of the present invention has extremely high CO2 adsorption capacity, especially CO2 capture under low pressure (≤0.15 bar) and high humidity (≥40%RH) conditions.

[0222] Comparative Example 4

[0223] Comparative Example 4 followed the same preparation and detection methods as Example 1, except that the pH adjustment step was replaced with adding excess hydrochloric acid solution to adjust the solution pH < 1. The PXRD pattern of the material is shown in Figure 58, demonstrating that the material cannot be synthesized in a strongly acidic environment. At 296 K, the material adsorbed 0.5 mmol / g of CO2. -1 The adsorption capacity for N2 is 0.3 mmol g. -1 It cannot achieve highly selective adsorption of CO2.

[0224] Comparative Example 5

[0225] Comparative Example 5 followed the same preparation and detection methods as Example 1, except that the pH adjustment step was replaced with adding NaOH to adjust the solution pH > 8. The product exhibited decreased crystallinity and reduced CO2 adsorption performance, with an adsorption capacity of < 4.5 mmol g at 296 K 1 bar. -1 Compared with the material in Example 1, the CO2 adsorption capacity decreased by more than 10%.

[0226] Comparative Example 6

[0227] Comparative Example 6 followed the preparation and detection methods of Example 1, except that the molar concentrations of the zinc sulfate aqueous solution and the potassium ferrocyanide aqueous solution were changed to 2M. As a result, a large amount of precipitate was immediately formed upon contact between the two reaction solutions, resulting in a low reaction yield. Furthermore, the crystals agglomerated before they had time to grow, resulting in small crystal sizes (<100nm), poor crystallinity of the product, and broadened diffraction peaks in the PXRD pattern, with the double peaks at 2θ = 13±2° and 24±2° both broadening into peaks resembling steamed buns.

[0228] Comparative Example 7

[0229] Comparative Example 7 followed the same preparation and detection methods as Example 1, except that the concentration of the potassium chloride solution used for ion exchange was changed to 0.015 M. The result was insufficient ion exchange, with the measured molar fraction of A being less than 3%; the BET specific surface area, as measured by the 77K N2 adsorption curve, was less than 500 m². 2 g -1Compared with the material in Example 1, the specific surface area decreased by more than 20%.

[0230] In summary, the above embodiments and comparative data demonstrate that the framework material of the present invention exhibits superior CO2 adsorption performance compared to existing CALF-20, zeolite 13X, and Ni-MOF-74 materials, especially in capturing CO2 in humid environments, where it demonstrates excellent moisture resistance. Comparative Examples 4-7 prove that the characteristic parameters of the preparation method of this application have a synergistic effect, resulting in a framework material with a unique structure containing free monovalent cations, possessing a unique crystal structure and unit cell parameters, and exhibiting outstanding performance in carbon dioxide adsorption in low-pressure (≤0.15 bar) and high-humidity environments (≥40% RH).

[0231] The above embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A metal cyanide-based framework material, characterized in that, The structural formula of the frame material is M. x [M′(CN)6] y ·A z ·nH₂O, where M is a tetracoordinate metal ion, 1≤x≤8, [M′(CN)₆] is a hexacyanide ion, 1≤y≤6, A is a monovalent cation, 1≤z≤6, and satisfies 2x-4y+z=0; n represents the water content of the material, 0≤n≤10; the framework material is composed of a crystal structure, and when 1≤n≤10, the XRD pattern of the crystal structure has a single peak at 2θ=16±2°, 20±2°, and a single or double peak at 13±2°, 22±2°, 24±2°, and the crystal structure belongs to the trigonal crystal system. Space group (space group number 167), cell parameters are When 0 ≤ n < 1, the XRD pattern of the crystal structure has a single peak at 2θ = 10 ± 2° and 16.5 ± 2°, and a single or double peak at 14.5 ± 2° and 20.2 ± 2°. The space group of the crystal structure is... The space group (space group number 167) is transformed into the P2 / c space group (space group number 13), with the cell parameters being... Preferably, the four-coordinated metal ion M is selected from Zn. 2+ Fe 2+ Co 2+ Cu 2+ Ni 2+ Cd 2+ Any one or more combinations thereof; Preferably, the hexacyanide ion [M′(CN)6] is selected from [Fe(CN)6]. 4- [Ru(CN)6] 4- and [Os(CN)6] 4- Any one or more combinations thereof; Preferably, the monovalent cation A is selected from H + NH4 + Li + Na + K + Rb + Cs + ,Fr + Any one or more combinations thereof; Preferably, the frame material comprises elements M, M′, C, N, A, H, and O, wherein the mole fraction of M is 5%–15%, the mole fraction of M′ is 3%–10%, the mole fraction of C is 30%–45%, the mole fraction of N is 30%–45%, the mole fraction of A is 3%–10%, the mole fraction of H is 0%–40%, and the mole fraction of O is 0%–20%. Preferably, the BET specific surface area of ​​the frame material is 200–1000 m². 2 g -1 .

2. The metal cyanide framework material according to claim 1, characterized in that: The frame material includes, but is not limited to, Zn. x [M′(CN)6] y (NH4) z ·nH2O、Zn x [M′(CN)6] y ·Na z ·nH2O、Zn x [M′(CN)6] y ·K z ·nH2O、Zn x [M′(CN)6] y ·Rb z ·nH₂O, wherein [M′(CN)₆] is selected from [Fe(CN)₆] 4- [Ru(CN)6] 4- and [Os(CN)6] 4- Any one or more of the following, where 2.5 ≤ x ≤ 3.5, 1.5 ≤ y ≤ 2.5, 1.5 ≤ z ≤ 2.5, and satisfying 2x - 4y + z = 0; more preferably, the frame material is Zn3[Fe(CN)6]2·A2, where A is selected from H + NH4 + Li + Na + K + Rb + Cs + One or more of the following; more preferably, the frame material is Zn3[Fe(CN)6]2·K2.

3. The metal cyanide framework material according to claim 1, characterized in that, The crystal structure of the framework material is a dodecahedral porous cage structure, with each cage having twelve pore windows. The monovalent cation A is in a free state within the cage. The dodecahedral porous cage structure is restored, fitted, or refined based on XRD test data. Preferably, the 12 openings include 6 hexagonal openings and 6 quadrilateral openings, wherein the diameter of the hexagonal openings is [missing information]. The diameter of the quadrilateral window is Preferably, when the water content of the material is 0 ≤ n < 1, the metal cyanide framework material exhibits a cation-gated effect. This cation-gated effect selectively allows CO2 molecules to pass through the pores while essentially preventing other molecules such as N2 and CH4 from passing through, thereby achieving extremely high CO2 adsorption capacity and selectivity. Further, the cation-gated effect refers to a CO2 to N2 adsorption molar ratio greater than 10 and a CO2 adsorption capacity greater than 3 mmol g under the same temperature and pressure conditions. -1 Further, the temperature is 273–333 K; further, the pressure is 0.15–1 bar; further, when the temperature is 273–333 K and the pressure is 0.15–1 bar, the N2 adsorption capacity of the framework material is less than 0.3 mmol g. -1 Furthermore, when the temperature and pressure are 296 K and 1 bar, the molar ratio of CO2 to N2 adsorption capacity of the framework material reaches more than 20, and the CO2 adsorption capacity is greater than 4 mmol g. -1 ; Preferably, when the CO2 pressure is 0.15 bar and the humidity is 40-80% RH, the metal cyanide framework material can achieve at least 3.5 mmol g at 296 K. -1 (140cm 3 cm -3 The amount of carbon dioxide adsorbed.

4. The metal cyanide framework material according to claim 1, characterized in that, When 0 ≤ n < 1, at a temperature of 296–313 K and a pressure of 1 bar, according to the Ideal Adsorbed Solution Theory (IAST), the IAST selectivity (Si) of the framework material for CO2 / N2 with a volume ratio (volume / volume, abbreviated as v / v) of 15 / 85 is calculated. ads ≥500; Preferably, when the framework material is Zn3[Fe(CN)6]2·K2, the CO2 adsorption capacity at 296 K and 1 bar is ≥4.5 mmol g. -1 N2 adsorption capacity ≤ 0.2 mmol g -1 For a CO2 / N2 separation selectivity of 15 / 85 (S ads ≥10000; Preferably, when the CO2 pressure is 0.15 bar and the humidity is 40-80% RH, the metal cyanide framework material can achieve at least 3.5 mmol g at 296 K. -1 (140cm 3 cm -3 The amount of carbon dioxide adsorbed, and the IAST selectivity (S) for CO2 / N2 (15 / 85, v / v) ads ≥500.

5. A method for preparing a metal cyanide-based framework material, characterized in that, The method steps are as follows: (1) First, adjust the pH of the solution containing the tetracoordinated metal ion M and the solution containing the hexacyanide ion [M′(CN)6] to pH = 4-7 respectively. Then, mix and stir the two solutions to carry out the reaction. The molar concentration of both the M solution and the [M′(CN)6] solution is ≤1 mol / L. -1 After the reaction is complete, a framework material intermediate is obtained; (2) The framework material intermediate is immersed in an aqueous or organic solution containing monovalent cation A for ion exchange, wherein the concentration of A ions in the solution is ≥0.05 mol / L. -1 Repeat the exchange steps multiple times until the molar fraction of monovalent cation A in the framework material is 3% to 10%, and obtain a framework material with a water content of 1≤n≤10. Preferably, the four-coordinated metal ion M is selected from Zn. 2+ Fe 2+ Co 2+ Cu 2+ Ni 2+ Cd 2+ Any one or more of the following; more preferably, the source of the tetracoordinate metal ion M is any one or more of zinc sulfate, zinc chloride, zinc nitrate, zinc acetate, ferrous chloride, and nickel chloride; Preferably, the hexacyanide ion [M′(CN)6] is selected from [Fe(CN)6]. 4- [Ru(CN)6] 4- and [Os(CN)6] 4- Any one or more of the following; more preferably, the source of the hexacyanide ion [M′(CN)6] is any one or more of K4[Fe(CN)6], Na4[Fe(CN)6], Li4[Fe(CN)6], H4[Fe(CN)6], Rb4[Fe(CN)6], and (NH4)4[Fe(CN)6]; Preferably, in step (1), the solvent of the solution is selected from one or more of water, alcohols and DMF, and more preferably water; Preferably, in step (1), the pH value is adjusted using an acidic regulator selected from one or more of hydrochloric acid, acetic acid, sulfuric acid, or nitric acid; Preferably, in step (1), the molar concentrations of the M solution and the [M′(CN)6] solution are 0.05–0.5 mol / L. -1 ; Preferably, in step (1), the molar ratio of M to [M′(CN)6] is 1:0.1 to 2; Preferably, in step (1), the reaction temperature is room temperature or heating; preferably, the heating temperature is ≤200℃; more preferably, the heating temperature is 50~150℃ and the heating time is 1~72h; even more preferably, the heating temperature is 60~100℃ and the heating time is 3~24h. Preferably, in step (2), the molar ratio of the monovalent cation A to the tetracoordinate metal ion M is ≥0.67; more preferably, the molar ratio is 0.67 to 4. Preferably, in step (2), the concentration of A ions in the solution is 2 mol / L. -1 ; Preferably, in step (2), the monovalent cation A is selected from H + NH4 + Li + Na + K + Rb + Cs + ,Fr + Any one or more combinations thereof; more preferably, the aqueous or organic solution containing monovalent cation A is selected from aqueous solutions, alcoholic solutions, and DMF solutions of LiCl, NaCl, KCl, RbCl, CsCl, FrCl, HCl, NH4Cl. Preferably, in step (2), the ion exchange temperature is 25-150℃, more preferably 25-60℃; the exchange time is 1-72h; and the number of exchanges is 1-8 times, more preferably 1-3 times.

6. The preparation method according to claim 5, characterized in that, Following step (2), an activation step is also included to make the water content 0 ≤ n < 1; Preferably, the activation step includes a combination of one or more methods selected from depressurization, heating, or gas purging; Preferably, the method of reducing pressure is to maintain the material obtained in step (2) in a vacuum environment of 0.1 to 100 Pa; more preferably, the vacuum degree is 0.1 to 10 Pa. Preferably, the heating method is to maintain the ambient temperature of the material obtained in step (2) at 50 to 300°C; more preferably, the temperature is 150°C. Preferably, the gas purging method can use a combination of one or more gases selected from nitrogen, argon, helium, air, or steam; more preferably, nitrogen. Preferably, the activation time is 3 to 48 hours.

7. A physical adsorbent for CO2 capture, comprising a framework material as described in any one of claims 1-4 or a framework material prepared by the preparation method as described in any one of claims 5-6.

8. A method for adsorbing CO2, characterized in that, The physical adsorbent described in claim 7 is used to contact CO2 gas.

9. A CO2 adsorption device, characterized in that, Includes the physical adsorbent of claim 7, or uses the adsorption method of claim 8; preferably, the adsorption device includes, but is not limited to, an adsorption bed, adsorption pipeline, and adsorption chamber.

10. An application for adsorbing CO2, characterized in that, The adsorbent described in claim 7, the adsorption method described in claim 8, or the adsorption device described in claim 9 may be used; preferably, the application of CO2 adsorption includes, but is not limited to, flue gas CO2 capture, biogas CO2 capture, and confined space CO2 capture.

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