Preparation method of graded porous MOF (Metal Organic Framework) nanofiber aerogel for capturing CO2
Hierarchical porous MOF nanofiber aerogels were prepared by combining electrospinning and in-situ growth, which solved the problems of insufficient binding strength and low pore utilization of MOF-based fiber adsorbent materials, and achieved efficient CO2 capture and stable adsorption.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- DONGHUA UNIV
- Filing Date
- 2026-04-14
- Publication Date
- 2026-05-19
AI Technical Summary
Existing MOF-based fiber adsorbent materials suffer from problems such as insufficient MOF binding strength, easy agglomeration, low effective pore utilization, and easy blockage of gas channels during CO2 capture.
A hierarchical porous MOF nanofiber aerogel was prepared by combining electrospinning and in-situ growth. By controlling the gradient temperature and vacuum, the MOF was grown in situ on the fiber substrate, forming a honeycomb-like gas transport channel and abundant adsorption sites.
It significantly enhances the material's affinity for CO2, improves CO2 transport efficiency and adsorption performance, exhibits strong material stability, and has a simple and efficient synthesis process.
Smart Images
Figure CN122057451A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of nanofiber materials technology, specifically to a method for preparing hierarchical porous MOF nanofiber aerogel for CO2 capture. Background Technology
[0002] Global warming is increasingly becoming an urgent threat to the environment and public health. Greenhouse gas emissions are considered the main cause of global warming, with carbon dioxide (CO2) emissions playing a dominant role. Therefore, exploring new materials, technologies, and processes to develop effective and economical CO2 capture technologies has received widespread attention.
[0003] Porous solid adsorbents are highly favored in the field of efficient CO2 capture due to their advantages such as low energy consumption, high selectivity, and large specific surface area. Metal-organic frameworks (MOFs), with their high specific surface area, stable topology, and tunable pore size, show great potential in gas capture and separation. Among them, classic MOF materials such as Mg-MOF-74 and SIFSIX-2-Cu-i not only possess excellent structural properties but also exhibit superior CO2 adsorption performance, making them promising candidates for CO2 adsorption. However, most MOF materials are in crystalline powder form, which presents challenges in practical applications such as high pressure drop, large mass transfer resistance, difficult recovery, and easy particle dispersion. To address these issues, current research primarily uses porous materials as carriers and employs composite preparation methods to develop MOF-based composite adsorbent materials that combine excellent adsorption performance with good engineering applicability. The preparation of MOF-based adsorbent materials mainly relies on the physical or chemical bonding of MOF powder and substrate, using methods such as blend spinning and in-situ synthesis to prepare macroscopically continuous MOF-based composite adsorbent materials. Existing technologies have attempted to co-mix MOF powders such as MOF-274 and EMM-44 with polymers such as AO-PIM-1 and polyethersulfone in specific solvents to form spinning solutions, and then extrude and spin them through a syringe to obtain MOF-based fiber adsorbent materials for CO2 capture. However, these materials have problems such as insufficient MOF binding strength, easy agglomeration, low effective pore utilization, and easy blockage of gas channels. Summary of the Invention
[0004] The purpose of this invention is to provide a hierarchical porous MOF nanofiber aerogel for CO2 capture and its preparation method, so as to solve the problems mentioned in the background art.
[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:
[0006] In a first aspect, the present invention provides a method for preparing hierarchical porous MOF nanofiber aerogel for CO2 capture, comprising the following steps:
[0007] S1. Dissolve the inherent microporous polymer and organic ligands in a solvent to obtain a spinning solution, electrospin the solution, and cut it to obtain inherent microporous polymer nanofibers A rich in organic ligand sites;
[0008] S2. After mixing the metal salt, crosslinking agent, catalyst and solvent to prepare a reaction solution, add the inherently microporous polymer nanofibers A rich in organic ligand sites to the reaction solution and disperse them to obtain nanofiber dispersion B.
[0009] S3. Gradient temperature control and vacuum regulation are applied to nanofiber dispersion B to achieve an integrated continuous process of in-situ growth, freeze-drying, and MOF activation, resulting in hierarchical porous MOF nanofiber aerogel.
[0010] Furthermore, in step S1, the inherently microporous polymer is at least one of PIM-1, PIM-1-COOH, PIM-1-AM, or AO-PIM-1.
[0011] Wherein, the molecular weight of PIM-1 is 40,000-100,000 da; the molecular weight of PIM-1-COOH is 40,000-100,000 da; the molecular weight of PIM-1-AM is 40,000-100,000 da; and the molecular weight of AO-PIM-1 is 40,000-100,000 da.
[0012] The organic ligand is at least one of 4,4'-bipyridine, 1,2-dipyridineacetylene, and pyrazine;
[0013] The solvent is at least one selected from tetrachloromethane, dimethyl sulfoxide, and N,N-dimethylacetamide.
[0014] Furthermore, in step S1, the mass ratio of the inherently microporous polymer to the organic ligand is 1:0.3-1;
[0015] The concentration of the inherently microporous polymer in the spinning solution is 20-25 wt%.
[0016] Furthermore, in step S1, during electrospinning, the spinning voltage is 15-18kV, the spinning solution propulsion rate is 0.1-1mL / h, the receiving distance is 10-20cm, the working temperature during spinning is 20-25℃, and the relative humidity is 40-50%, so as to obtain intrinsically microporous polymer nanofibers A with a diameter of 500-900nm and internal mesopores with a diameter of 10-50nm and micropores with a diameter of 0.6-1nm, which are rich in organic ligand sites.
[0017] The material used to accept the fiber membrane is any one of oil-absorbing paper, tin foil, aluminum foil, or non-woven fabric.
[0018] Furthermore, in step S2, during dispersion, high-speed shear dispersion is adopted. The high-speed shear dispersion parameters are: rotation speed 5000-10000 rpm, time 0.5-1.5 min, and the temperature of the dispersion system is maintained at 0-10℃.
[0019] Furthermore, in step S2, the metal salt is at least one of copper tetrafluoroborate, copper hexafluorosilicate, and zinc hexafluorosilicate;
[0020] The crosslinking agent is at least one of methyltrimethoxysilane, trimethoxy(3-methoxypropyl)silane, 3-aminopropyltriethoxysilane and 1,4-butanediol diglycidyl ether;
[0021] The catalyst is oxalic acid; the solvent is at least one of water, isopropanol, acetone and tert-butanol.
[0022] Furthermore, in step S2, the concentration of the inherently microporous polymer nanofibers A rich in organic ligand sites in the nanofiber dispersion B is 0.8-1 wt%, the concentration of the metal salt is 0.4-0.6 wt%, the concentration of the catalyst is 0.001-0.004 wt%, and the concentration of the crosslinking agent is 0.7-0.9 wt%.
[0023] Furthermore, in step S3, the gradient temperature control and vacuum degree regulation include the in-situ growth stage, the freeze-drying stage, and the MOF activation stage.
[0024] During the in-situ growth stage, the reaction parameters are: temperature 20-30℃, vacuum degree 90000-100000Pa, and time 5-10min.
[0025] During the freeze-drying stage, the reaction parameters were: temperature -60℃ to -40℃, vacuum degree 1-10Pa, and time 48-72h.
[0026] During the MOF activation stage, the reaction parameters are: temperature 50-60℃, vacuum degree 1-10Pa, and time 10-16h.
[0027] Secondly, the present invention provides a hierarchical porous MOF nanofiber aerogel for CO2 capture prepared by the above preparation method.
[0028] Thirdly, the present invention also provides an application of hierarchical porous MOF nanofiber aerogel for CO2 capture in CO2 adsorption.
[0029] Compared with the prior art, the beneficial effects achieved by the present invention are:
[0030] (1) The hierarchical porous MOF nanofiber aerogel provided by the present invention constructs a honeycomb-shaped anisotropic gas transport channel and combines the inherent microporous polymer with the abundant CO2 affinity groups (-NH2, SiF6) provided by MOF. 2- The adsorption sites formed by these adsorption sites significantly enhance the material's affinity for CO2, thereby enabling preferential CO2 transport in the mixed gas.
[0031] (2) The hierarchical porous MOF nanofiber aerogel provided by this invention has a structure in which the inherent microporous polymer fibers and MOF synergistically form a rich hierarchical porous system. This system specifically includes: macropores formed by the entanglement between nanofibers, mesopores formed on the surface / cross-section of nanofibers by non-solvent-induced phase separation electrospinning technology, and micropores inherent in the microporous polymer and MOF itself. This hierarchical porous structure greatly improves the mass transfer efficiency of CO2 molecules in the aerogel.
[0032] (3) The hierarchical porous MOF nanofiber aerogel provided by the present invention has MOF crystals growing directly on the fiber substrate in situ, forming an interface structure with strong mechanical interlocking effect, thereby effectively preventing MOF particles from falling off and providing abundant and stable CO2 adsorption sites for the aerogel.
[0033] (4) The hierarchical porous MOF nanofiber aerogel provided by this invention achieves integrated continuous processing of in-situ growth, freeze-drying, and MOF activation in stages by controlling the concentration of organic ligands in the spinning solution, the concentration of metal salts and crosslinking agents in the dispersion, and adjusting the temperature and vacuum degree in stages during the aerogel forming process, thereby obtaining hierarchical porous MOF nanofiber aerogel. This synthesis process is simple, efficient, and has a short procedure.
[0034] (5) The hierarchical porous MOF nanofiber aerogel material obtained by the preparation method provided by the present invention has an MOF loading of up to 50%, and has the advantages of high porosity, excellent CO2 adsorption performance and strong application stability. Attached Figure Description
[0035] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:
[0036] Figure 1 X-ray diffraction (XRD) patterns of Example 1 and Comparative Example 1.
[0037] Figure 2 This is a SEM image of Example 1.
[0038] Figure 3The nitrogen adsorption-desorption isotherms and CO2 adsorption performance curves of Examples 1-3 and Comparative Example 1 of this invention are shown.
[0039] Figure 4 The images show the finished product appearance of Example 1 and Comparative Example 3. Detailed Implementation
[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0041] The mechanism of this invention is as follows:
[0042] The hierarchical porous MOF nanofiber aerogel prepared by this invention needs to meet three conditions:
[0043] The first aspect is the stable preparation of intrinsically microporous polymer nanofibers A rich in organic ligand sites. The mixed spinning solution of the intrinsically microporous polymer and organic ligands is jet-drawn into fibers under a high-voltage electric field through non-solvent-induced phase separation. The different contents of the intrinsically microporous polymer and organic ligands determine important parameters such as the ease of fiber formation and microstructure of the intrinsically microporous polymer nanofibers rich in organic ligand sites.
[0044] Secondly, the preparation of a uniform and stable nanofiber dispersion is crucial. This requires nanofibers with a diameter of 500-900 nm and a length of 200-400 μm to ensure inter-fiber entanglement without excessive aggregation, while also providing necessary and sufficient fiber bonding points for subsequent crosslinking. Maintaining the dispersion temperature within the range of 0-10℃ is essential; excessively high temperatures may cause MOFs to grow prematurely during dispersion and detach from the fibers under high-speed homogenization.
[0045] Thirdly, the in-situ growth of MOFs and the bonding and cross-linking of the three-dimensional aerogel network are carried out during the gradient temperature control and vacuum degree regulation stages. A certain amount of metal salt is added to the dispersion to regulate the MOF loading. A certain amount of cross-linking agent is added to the dispersion to stabilize the structural stability of the three-dimensional aerogel network. Excessive cross-linking agent can easily cause pore blockage, sealing CO2 adsorption active sites and leading to a decrease in adsorption performance; insufficient cross-linking agent makes it difficult to ensure the structural stability of the aerogel, easily causing the three-dimensional network to collapse during application. Therefore, the choice of cross-linking agent amount determines the structural and application stability of the hierarchical porous MOF nanofiber aerogel.
[0046] Furthermore, this invention limits the amount of intrinsically microporous polymer nanofibers A rich in organic ligand sites added. In this invention, if the concentration of intrinsically microporous polymer nanofibers A rich in organic ligand sites exceeds 1 wt%, the excessively dense entanglement structure may significantly reduce the porosity of the aerogel and block some adsorption active sites, thereby affecting CO2 adsorption performance. Conversely, if the concentration is below 0.8 wt%, the degree of nanofiber entanglement will be insufficient to effectively support the three-dimensional network structure, causing collapse during drying and preventing proper shaping.
[0047] The technical solutions provided by the present invention will be described in detail below with reference to specific embodiments, but they should not be construed as limiting the scope of protection of the present invention.
[0048] All raw materials and reagents used in the examples are commercially available.
[0049] Example 1
[0050] A method for preparing hierarchical porous MOF nanofiber aerogel for CO2 capture includes the following steps:
[0051] S1. Preparation of intrinsically microporous polymer nanofibers A rich in organic ligand sites;
[0052] 0.3 g of AO-PIM-1 (66135 da) and 0.3 g of 1,2-dipyridine acetylene powder were mixed in 1.5 mL of DMSO and then magnetically stirred at 500 rpm for 8 h to obtain the spinning solution.
[0053] The obtained spinning solution was subjected to electrospinning with the following parameters: spinning voltage 18kV, spinning solution feed rate 1mL / h, receiving distance 15cm, ambient temperature 23℃, relative humidity 50%, and the receiving fiber membrane material was tin foil. After the obtained nanofibers were vacuum dried at 60℃ for 4h, the obtained fibers were cut to obtain intrinsically microporous polymer nanofibers A rich in organic ligand sites.
[0054] The average diameter of the intrinsically microporous polymer nanofiber A, which is rich in organic ligand sites, is 750 nm.
[0055] S2. Preparation of nanofiber dispersion B;
[0056] The intrinsically microporous polymer nanofibers A rich in organic ligand sites obtained in step S1 were added to a mixed solution system containing Cu(BF4)2·xH2O, methyltrimethoxysilane and oxalic acid. The solvent of the mixed solution system was deionized water and tert-butanol in a volume ratio of 9:1. After the above raw materials were mixed, they were dispersed by high-speed shearing using a homogenizer to obtain nanofiber dispersion B.
[0057] The concentrations of Cu(BF4)2·xH2O in nanofiber dispersion B were 0.6 wt%, methyltrimethoxysilane in nanofiber dispersion B were 0.8 wt%, and oxalic acid in nanofiber dispersion B were 0.004 wt%; the concentration of intrinsically microporous polymer nanofibers A, rich in organic ligand sites, in nanofiber dispersion B was 0.8 wt%.
[0058] The conditions for the high-speed dispersion process were: rotation speed 8000 rpm, time 1.5 min, and solution temperature 5℃.
[0059] S3. Transfer the nanofiber dispersion B obtained in step S2 to the mold, and then place the mold into a freeze dryer to undergo gradient temperature control and vacuum degree regulation for reaction;
[0060] The reaction is divided into three stages.
[0061] During the in-situ growth stage, the reaction parameters were: temperature 25℃, vacuum degree 90000-100000Pa, and time 10min;
[0062] During the freeze-drying stage, the reaction parameters were: temperature -45℃, vacuum degree 3-10Pa, and time 60h.
[0063] During the MOF activation stage, the reaction parameters were: temperature 60℃, vacuum degree 3-10Pa, and time 8h.
[0064] After the reaction, a hierarchical porous MOF nanofiber aerogel for CO2 capture was obtained, with a bulk density of 8.04 mg / cm³. 3 Specific surface area is 491m² 2 / g, CO2 adsorption capacity is 4.03mmol / g.
[0065] Example 2
[0066] A method for preparing hierarchical porous MOF nanofiber aerogel for CO2 capture includes the following steps:
[0067] S1. Preparation of intrinsically microporous polymer nanofibers A rich in organic ligand sites;
[0068] 0.3 g of AO-PIM-1 (molecular weight 66135 da) and 0.2 g of 1,2-dipyridineacetylene powder were mixed in 1.5 mL of DMSO and then magnetically stirred at 500 rpm for 8 h to obtain the spinning solution.
[0069] The obtained spinning solution was subjected to electrospinning with the following parameters: spinning voltage 18kV, spinning solution feed rate 1mL / h, receiving distance 15cm, ambient temperature 23℃, relative humidity 50%, and the receiving fiber membrane material was tin foil. After the obtained nanofibers were vacuum dried at 60℃ for 4h, the obtained fibers were cut to obtain intrinsically microporous polymer nanofibers A rich in organic ligand sites.
[0070] The average diameter of the intrinsically microporous polymer nanofiber A, which is rich in organic ligand sites, is 750 nm.
[0071] S2. Preparation of nanofiber dispersion B;
[0072] The intrinsically microporous polymer nanofibers A rich in organic ligand sites obtained in step S1 were added to a mixed solution system containing Cu(BF4)2·xH2O, methyltrimethoxysilane and oxalic acid. The solvent of the mixed solution system was deionized water and tert-butanol in a volume ratio of 9:1. After the above raw materials were mixed, they were dispersed by high-speed shearing using a homogenizer to obtain nanofiber dispersion B.
[0073] The concentrations of Cu(BF4)2·xH2O in nanofiber dispersion B were 0.5 wt%, methyltrimethoxysilane in nanofiber dispersion B were 0.8 wt%, and oxalic acid in nanofiber dispersion B were 0.004 wt%; the concentration of intrinsically microporous polymer nanofibers A, rich in organic ligand sites, in nanofiber dispersion B was 0.8 wt%.
[0074] The conditions for the high-speed dispersion process were: rotation speed 8000 rpm, time 1.5 min, and solution temperature 5℃.
[0075] S3. Transfer the nanofiber dispersion B obtained in step S2 to the mold, and then place the mold into a freeze dryer to undergo gradient temperature control and vacuum degree regulation for reaction;
[0076] The reaction is divided into three stages.
[0077] During the in-situ growth stage, the reaction parameters were: temperature 25℃, vacuum degree 90000-100000Pa, and time 10min;
[0078] During the freeze-drying stage, the reaction parameters were: temperature -45℃, vacuum degree 3-10Pa, and time 60h.
[0079] During the MOF activation stage, the reaction parameters were: temperature 60℃, vacuum degree 3-10Pa, and time 16h.
[0080] After the reaction was completed, a hierarchical porous MOF nanofiber aerogel for CO2 capture was obtained, with a bulk density of 8.07 mg / cm³. 3 Specific surface area is 484 m² 2 / g, CO2 adsorption capacity is 3.71mmol / g.
[0081] Example 3
[0082] A method for preparing hierarchical porous MOF nanofiber aerogel for CO2 capture includes the following steps:
[0083] S1. Preparation of intrinsically microporous polymer nanofibers A rich in organic ligand sites;
[0084] 0.3 g of AO-PIM-1 (molecular weight 66135 da) and 0.15 g of 1,2-dipyridineacetylene powder were mixed in 1.5 mL of DMSO and then magnetically stirred at 500 rpm for 8 h to obtain the spinning solution.
[0085] The obtained spinning solution was subjected to electrospinning with the following parameters: spinning voltage 18kV, spinning solution feed rate 1mL / h, receiving distance 15cm, ambient temperature 23℃, relative humidity 50%, and the receiving fiber membrane material was tin foil. After the obtained nanofibers were vacuum dried at 60℃ for 4h, the obtained fibers were cut to obtain intrinsically microporous polymer nanofibers A rich in organic ligand sites.
[0086] The average diameter of the intrinsically microporous polymer nanofiber A, which is rich in organic ligand sites, is 750 nm.
[0087] S2. Preparation of nanofiber dispersion B;
[0088] The intrinsically microporous polymer nanofibers A rich in organic ligand sites obtained in step S1 were added to a mixed solution system containing Cu(BF4)2·xH2O, methyltrimethoxysilane and oxalic acid. The solvent of the mixed solution system was deionized water and tert-butanol in a volume ratio of 9:1. After the above raw materials were mixed, they were dispersed by high-speed shearing using a homogenizer to obtain nanofiber dispersion B.
[0089] The concentration of Cu(BF4)2·xH2O in nanofiber dispersion B is 0.4wt%, the concentration of methyltrimethoxysilane in nanofiber dispersion B is 0.8wt%, and the concentration of oxalic acid in nanofiber dispersion B is 0.004wt%; the concentration of intrinsically microporous polymer nanofiber A rich in organic ligand sites in nanofiber dispersion B is 0.8wt%.
[0090] The conditions for the high-speed dispersion process were: rotation speed 8000 rpm, time 1.5 min, and solution temperature 5℃.
[0091] S3. Transfer the nanofiber dispersion B obtained in step S2 to the mold, and then place the mold into a freeze dryer to undergo gradient temperature control and vacuum degree regulation for reaction;
[0092] The reaction is divided into three stages.
[0093] During the in-situ growth stage, the reaction parameters were: temperature 25℃, vacuum degree 90000-100000Pa, and time 10min;
[0094] During the freeze-drying stage, the reaction parameters were: temperature -45℃, vacuum degree 3-10Pa, and time 60h.
[0095] During the MOF activation stage, the reaction parameters were: temperature 60℃, vacuum degree 3-10Pa, and time 16h.
[0096] After the reaction, a hierarchical porous MOF nanofiber aerogel for CO2 capture was obtained, with a bulk density of 8.02 mg / cm³. 3 Specific surface area is 475m² 2 / g, CO2 adsorption capacity is 3.44mmol / g.
[0097] Comparative Example 1
[0098] A method for preparing hierarchical porous MOF nanofiber aerogel for CO2 capture includes the following steps:
[0099] S1. Preparation of intrinsically microporous polymer nanofibers A rich in organic ligand sites;
[0100] 0.3 g of AO-PIM-1 (molecular weight 66135 da) was mixed in 1.5 mL of DMSO and then magnetically stirred at 500 rpm for 8 h to obtain the spinning solution.
[0101] The obtained spinning solution was subjected to electrospinning with the following parameters: spinning voltage 18kV, spinning solution feed rate 1mL / h, receiving distance 15cm, ambient temperature 23℃, relative humidity 50%, and the receiving fiber membrane material was tin foil. After the obtained nanofibers were vacuum dried at 60℃ for 4h, the obtained fibers were cut to obtain intrinsically microporous polymer nanofibers A rich in organic ligand sites.
[0102] The average diameter of the intrinsically microporous polymer nanofiber A, which is rich in organic ligand sites, is 750 nm.
[0103] S2. Preparation of nanofiber dispersion B;
[0104] The intrinsically microporous polymer nanofibers A rich in organic ligand sites obtained in step S1 were added to a mixed solution system containing methyltrimethoxysilane and oxalic acid, wherein the solvent of the mixed solution system was deionized water and tert-butanol in a volume ratio of 9:1. After the above raw materials were mixed, they were dispersed by high-speed shearing using a homogenizer to obtain nanofiber dispersion B.
[0105] The concentration of methyltrimethoxysilane in nanofiber dispersion B is 0.8 wt%, and the concentration of oxalic acid in nanofiber dispersion B is 0.004 wt%; the concentration of intrinsically microporous polymer nanofibers A, rich in organic ligand sites, in nanofiber dispersion B is 0.8 wt%.
[0106] The conditions for the high-speed dispersion process were: rotation speed 8000 rpm, time 1.5 min, and solution temperature 5℃.
[0107] S3. Transfer the nanofiber dispersion B obtained in step S2 to a mold, then place the mold in a freeze dryer, cool to -45℃, evacuate to 3-10 Pa, and freeze-dry for 60 h. After the reaction is complete, a hierarchical porous MOF nanofiber aerogel for CO2 capture is obtained, with a bulk density of 7.98 mg / cm³. 3 Specific surface area is 423 m² 2 / g, CO2 adsorption capacity is 2.21mmol / g.
[0108] Comparative Example 2
[0109] A method for preparing hierarchical porous MOF nanofiber aerogel for CO2 capture includes the following steps:
[0110] S1. Preparation of intrinsically microporous polymer nanofibers A rich in organic ligand sites;
[0111] 0.3 g of AO-PIM-1 (molecular weight 66135 da) was mixed in 1.5 mL of DMSO and then magnetically stirred at 500 rpm for 8 h to obtain the spinning solution.
[0112] The obtained spinning solution was subjected to electrospinning with the following parameters: spinning voltage 18kV, spinning solution feed rate 1mL / h, receiving distance 15cm, ambient temperature 23℃, relative humidity 50%, and the receiving fiber membrane material was tin foil. After the obtained nanofibers were vacuum dried at 60℃ for 4h, the obtained fibers were cut to obtain intrinsically microporous polymer nanofibers A rich in organic ligand sites.
[0113] The average diameter of the intrinsically microporous polymer nanofiber A, which is rich in organic ligand sites, is 750 nm.
[0114] S2. Preparation of nanofiber dispersion B;
[0115] The intrinsically microporous polymer nanofibers A rich in organic ligand sites obtained in step S1 were added to a mixed solution system containing methyltrimethoxysilane and oxalic acid, wherein the solvent of the mixed solution system was deionized water and tert-butanol in a volume ratio of 9:1. After the above raw materials were mixed, they were dispersed by high-speed shearing using a homogenizer to obtain nanofiber dispersion B.
[0116] The concentrations of Cu(BF4)2·xH2O, methyltrimethoxysilane, and oxalic acid in nanofiber dispersion B were 1.5 wt% and 1.5 wt% respectively, respectively; the concentration of intrinsically microporous polymer nanofibers A, rich in organic ligand sites, in nanofiber dispersion B was 1.5 wt%.
[0117] The conditions for the high-speed dispersion process were: rotation speed 8000 rpm, time 1.5 min, and solution temperature 5℃.
[0118] S3. Transfer the nanofiber dispersion B obtained in step S2 to a mold, then place the mold in a freeze dryer, cool to -45℃, evacuate to 3-10 Pa, and freeze-dry for 60 h. After the reaction is complete, a hierarchical porous MOF nanofiber aerogel for CO2 capture is obtained, with a bulk density of 15.11 mg / cm³. 3 Specific surface area is 395m² 2 / g, CO2 adsorption capacity is 2.05mmol / g.
[0119] Comparative Example 3
[0120] This comparative example only changed the addition concentration (0.6 wt%) of the intrinsically microporous polymer nanofibers A rich in organic ligand sites in step S2; all other aspects were the same as in Example 1.
[0121] Detection:
[0122] XRD patterns of Example 1 and Comparative Example 1 were analyzed, and the results are shown in [the table below]. Figure 1 .
[0123] SEM imaging was performed on Example 1, and the results are shown in [the table below]. Figure 2 .
[0124] For Comparative Example 1, by Figure 1 As can be seen, Comparative Example 1 is a control sample of pure intrinsic microporous fiber aerogel without SIFSIX-2-Cu-i crystals. SIFSIX-2-Cu-i should be understood as: obtained by mixing organic ligand DPA solution and metal salt Cu(BF4)2·xH2O solution.
[0125] For Example 1, by Figure 1 , 2 As can be seen, the XRD pattern of Example 1 shows that the added characteristic peaks compared to Comparative Example 1 are in good agreement with the standard spectrum of SIFSIX-2-Cu-i crystal, confirming that SIFSIX-2-Cu-i has been successfully formed on the aerogel framework. The SEM image shows that the aerogel has an interconnected porous network structure and presents unique vertical channels. At the same time, SIFSIX-2-Cu-i can be seen to be uniformly distributed on the fiber surface.
[0126] The nitrogen adsorption-desorption isotherms and CO2 adsorption performance of Examples 1-3 and Comparative Examples 1-2 were tested. The test results are shown in the figure. Figure 3 .
[0127] The appearance of the finished products of Example 1 and Comparative Example 3 were inspected. Specific results are shown in [link to results]. Figure 4 .
[0128] For dispersions containing intrinsically microporous polymer nanofibers A rich in organic ligand sites at concentrations less than 0.8 wt%, the following applies: Figure 4 As can be seen, when the concentration is 0.6wt%, the sample collapses significantly during the drying process, making it difficult to form an effective three-dimensional network support structure.
[0129] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.
[0130] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for preparing hierarchical porous MOF nanofiber aerogel for CO2 capture, characterized in that: Includes the following steps: S1. Dissolve the inherent microporous polymer and organic ligands in a solvent to obtain a spinning solution, electrospin the solution, and cut it to obtain inherent microporous polymer nanofibers A rich in organic ligand sites; S2. After mixing the metal salt, crosslinking agent, catalyst and solvent to prepare a reaction solution, add the inherently microporous polymer nanofibers A rich in organic ligand sites to the reaction solution and disperse them to obtain nanofiber dispersion B. S3. Gradient temperature control and vacuum regulation are applied to nanofiber dispersion B to achieve an integrated continuous process of in-situ growth, freeze-drying, and MOF activation, resulting in hierarchical porous MOF nanofiber aerogel.
2. The method for preparing a hierarchical porous MOF nanofiber aerogel for CO2 capture according to claim 1, characterized in that: In step S1, the inherently microporous polymer is at least one of PIM-1, PIM-1-COOH, PIM-1-AM, or AO-PIM-1; The organic ligand is at least one of 4,4'-bipyridine, 1,2-dipyridineacetylene, and pyrazine; The solvent is at least one selected from tetrachloromethane, dimethyl sulfoxide, and N,N-dimethylacetamide.
3. The method for preparing a hierarchical porous MOF nanofiber aerogel for CO2 capture according to claim 1, characterized in that: In step S1, the mass ratio of the inherently microporous polymer to the organic ligand is 1:0.3-1; The concentration of the inherently microporous polymer in the spinning solution is 20-25 wt%.
4. The method for preparing a hierarchical porous MOF nanofiber aerogel for CO2 capture according to claim 1, characterized in that: In step S1, during electrospinning, the spinning voltage is 15-18kV, the spinning solution propulsion rate is 0.1-1mL / h, the receiving distance is 10-20cm, the working temperature during spinning is 20-25℃, and the relative humidity is 40-50%, so as to obtain intrinsically microporous polymer nanofibers A with a diameter of 500-900nm and internal mesopores of 10-50nm and micropores of 0.6-1nm rich in organic ligand sites. The material used to accept the fiber membrane is any one of oil-absorbing paper, tin foil, aluminum foil, or non-woven fabric.
5. The method for preparing a hierarchical porous MOF nanofiber aerogel for CO2 capture according to claim 1, characterized in that: In step S2, high-speed shear dispersion is used during dispersion. The parameters for high-speed shear dispersion are: rotation speed 5000-10000 rpm, time 0.5-1.5 min, and the temperature of the dispersion system is maintained at 0-10℃.
6. The method for preparing a hierarchical porous MOF nanofiber aerogel for CO2 capture according to claim 1, characterized in that: In step S2, the metal salt is at least one of copper tetrafluoroborate, copper hexafluorosilicate, and zinc hexafluorosilicate; The crosslinking agent is at least one of methyltrimethoxysilane, trimethoxy(3-methoxypropyl)silane, 3-aminopropyltriethoxysilane and 1,4-butanediol diglycidyl ether; The catalyst is oxalic acid; the solvent is at least one of water, isopropanol, acetone and tert-butanol.
7. The method for preparing a hierarchical porous MOF nanofiber aerogel for CO2 capture according to claim 1, characterized in that: In step S2, the concentration of the inherently microporous polymer nanofibers A rich in organic ligand sites in the nanofiber dispersion B is 0.8-1 wt%, the concentration of the metal salt is 0.4-0.6 wt%, the concentration of the catalyst is 0.001-0.004 wt%, and the concentration of the crosslinking agent is 0.7-0.9 wt%.
8. The method for preparing a hierarchical porous MOF nanofiber aerogel for CO2 capture according to claim 1, characterized in that: In step S3, gradient temperature control and vacuum degree regulation include the in-situ growth stage, the freeze-drying stage, and the MOF activation stage; During the in-situ growth stage, the reaction parameters are: temperature 20-30℃, vacuum degree 90000-100000Pa, and time 5-10min. During the freeze-drying stage, the reaction parameters were: temperature -60℃ to -40℃, vacuum degree 1-10Pa, and time 48-72h. During the MOF activation stage, the reaction parameters are: temperature 50-60℃, vacuum degree 1-10Pa, and time 10-16h.
9. A hierarchical porous MOF nanofiber aerogel for CO2 capture prepared by the preparation method according to any one of claims 1-8.
10. The application of the hierarchical porous MOF nanofiber aerogel for CO2 capture as described in claim 9 in CO2 adsorption.