A carbon fiber-based flower-shaped MXene / CH3-MIL-101(Fe) three-dimensional inorganic foam, its preparation method and its application

Abstract

The present application belongs to the technical field of photo-thermal synergistic catalytic materials, and specifically relates to a carbon fiber-based flower-shaped MXene / CH3-MIL-101(Fe) three-dimensional inorganic foam, a preparation method and application thereof. The preparation method comprises the following steps: after carbon fibers are cleaned by an alkaline solution and pretreated by plasma, the carbon fibers are combined with a few-layer Ti3C2T x MXene colloidal solution, a substrate is constructed through ice-bath ultrasonic adsorption and freeze-drying; CH3-MIL-101(Fe) is in-situ grown on the surface of the substrate by hydrothermal reaction of 2-methyl-1,4-benzene dicarboxylic acid and FeCl3 6H2O in a DMF / acetic acid system, and a composite three-dimensional inorganic foam is prepared. The three-dimensional inorganic foam prepared by the present application exhibits high-efficiency catalytic oxidation performance on benzene series VOCs as a photo-thermal catalyst, and the three-dimensional foam structure is convenient for recycling and reuse, and has a wide application prospect in the fields of industrial waste gas treatment and indoor air purification.

Description

Technical Field

[0001] This invention belongs to the field of photothermal synergistic catalytic materials technology. Specifically, it relates to a carbon fiber-based flower-shaped MXene / CH3-MIL-101(Fe) three-dimensional inorganic foam, its preparation method, and its application. Background Technology

[0002] Volatile organic compounds (VOCs) can lead to the formation of regional photochemical smog, haze, ozone, and other polluting weather, posing a serious threat to the atmospheric environment. VOCs mainly originate from industrial production, with benzene compounds accounting for 30%. Photothermal synergistic catalytic degradation of VOCs is characterized by its green, environmentally friendly, and low-energy consumption nature, and has broad application prospects. The technical feature of photothermal catalytic oxidation is that the catalyst itself possesses excellent thermocatalytic performance and a good ability to absorb solar radiation and convert it into heat energy. Driven by solar energy, it can raise the temperature to achieve the oxidation of low-concentration benzene-based VOCs. The current challenge of this technology is that during the catalytic degradation of benzene-based VOCs, while benzene-based VOCs, oxygen molecules, and water molecules are all reactants, their different polarities make it difficult for them to be uniformly adsorbed on the surface of a single polar catalyst, leading to a decrease in catalytic reaction efficiency. Summary of the Invention

[0003] To address the shortcomings of the existing technologies, the present invention aims to provide a carbon fiber-based flower-like MXene / CH3-MIL-101(Fe) three-dimensional inorganic foam with uniformly distributed hydrophilic and hydrophobic sites on its surface, its preparation method, and its applications. This three-dimensional inorganic foam acts as a "photothermal" catalyst. Due to the superhydrophilic nature of the MXene surface and the hydrophobic and oleophilic nature of CH3-MIL-101(Fe), the uniform distribution of these two components on the material surface results in a uniform distribution of hydrophilic and hydrophobic sites on the composite material surface. This ultimately achieves uniform adsorption of organic compound molecules, oxygen molecules, and water molecules of different polarities, enabling efficient, energy-saving, and stable degradation of volatile organic compounds (VOCs), particularly low-concentration benzene-based VOCs. The technical solution of the present invention is described in detail below.

[0004] This invention provides a method for preparing carbon fiber-based flower-shaped MXene / CH3-MIL-101(Fe) three-dimensional inorganic foam, comprising the following steps:

[0005] (1) Carbon fiber pretreatment: The carbon fiber is cut into small segments and washed in an ultrapure water washing solution containing NaOH, Triton X-100 and citric acid under hot water bath conditions to remove surface impurities; then the carbon fiber is ultrasonically cleaned and dried with anhydrous ethanol, and then placed in a plasma treatment machine for compressed air plasma treatment to introduce polar groups including hydroxyl and carboxyl groups; finally, the treated carbon fiber is dried.

[0006] (2) MXene preparation: 0.3-0.7g Ti3AlC2 was etched with hydrochloric acid and lithium fluoride to obtain multilayer MXene; the multilayer MXene was then ultrasonically dispersed in 80-100mL deionized water to form a colloidal solution, and ultrasonically exfoliated using a cell disruptor under an inert atmosphere to obtain a few-layer Ti3C2T with ≤6 layers. x Colloidal solutions of MXene-based materials;

[0007] (3) Three-dimensional substrate construction: The carbon fibers pretreated in step (1) are immersed in the MXene colloidal solution obtained in step (2) and ultrasonically cooled in an ice bath under inert gas protection to promote the adsorption and aggregation of MXene on the carbon fiber surface; then they are taken out and dried, and then re-immersed in the MXene colloidal solution for freeze drying to form a flower-shaped three-dimensional porous substrate; in the obtained flower-shaped three-dimensional porous substrate, MXene and carbon fibers are combined through Ti-OC bonds, hydrogen bonds or van der Waals forces to ensure structural stability and mass transfer efficiency.

[0008] (4) CH3-MIL-101(Fe) in situ loading: FeCl3•6H2O and 2-methyl-1,4-phthalic acid were first dissolved in DMF, and acetic acid was added and stirred to obtain a precursor solution; then the substrate was immersed in the precursor solution and hydrothermal reaction was carried out to achieve in situ growth; after the reaction was completed, the substrate was washed and dried in sequence to obtain a composite three-dimensional inorganic foam with uniformly distributed hydrophilic and hydrophobic sites; in the obtained composite three-dimensional inorganic foam, methyl groups were introduced through 2-methyl-1,4-phthalic acid to give the material hydrophobic and oleophilic properties, and formed a uniformly distributed hydrophilic and hydrophobic composite structure with hydrophilic MXene.

[0009] In this invention, in step (1), the hot water bath temperature is 85-95℃, the length of the carbon fiber is 1-5cm, the mass-to-volume ratio of the carbon fiber to the ultrapure water washing solution is 1:20~1:30g / mL, and the washing time is 45-75 minutes; in the ultrapure water washing solution, the mass-to-volume concentration of NaOH is 6-10g / L, the volume concentration of Triton X-100 is 0.2%-0.6%, and the mass-to-volume concentration of citric acid is 0.8-1.2g / L; during plasma treatment, the treatment is carried out at a power of 100-150W for 60-180 seconds; the drying temperature is 50-85℃, and the drying time is 6-10 hours.

[0010] In this invention, in step (2), the concentration of hydrochloric acid is 8-10 mol / L, the molar ratio of HCl to LiF in hydrochloric acid is 1:0.2-1:0.3, the etching temperature is 30-40℃, and the etching time is 20-28 hours.

[0011] In this invention, during step (2), the ultrasonic stripping is performed using an intermittent pulse mode, with a single ultrasonic session lasting 3-5 seconds, an interval of 2-4 seconds, a total ultrasonic time of 3.5-6.5 hours, an ultrasonic power of 190-210W, and an inert atmosphere of nitrogen with a nitrogen flow rate of 40-80mL / min.

[0012] In this invention, in step (2), by precisely controlling the etching time and ultrasonic parameters, the number of MXene layers is controlled and the surface defects are minimized, thereby optimizing its photothermal conversion performance.

[0013] In this invention, in step (3), the ice bath is ultrasonic for 20-40 minutes; the drying temperature is 60±5℃ and the drying time is 1.5-2.5 hours.

[0014] In this invention, in step (3), the freeze-drying temperature is -65℃ to -55℃, the vacuum degree is <12Pa, the drying time is 20-50 hours, and the freezing rate is 4-8℃ / min.

[0015] In this invention, in step (4), the feed ratio of FeCl3•6H2O, 2-methyl-1,4-phthalic acid, DMF and acetic acid in the precursor solution is (3-5) mmol: (3-5) mmol: (70-90) mL: (0.5-1.5) mL; the stirring time is 0.5-1.5 hours.

[0016] In this invention, in step (4), the hydrothermal reaction temperature is 75-85℃ and the hydrothermal reaction time is 5-13 hours; after the reaction is completed, DMF and ethanol are washed alternately 2-4 times, and vacuum dried at 55-65℃ for 10-14 hours.

[0017] This invention also provides a carbon fiber-based flower-like MXene / CH3-MIL-101(Fe) three-dimensional inorganic foam prepared by the above method, wherein the three-dimensional inorganic foam has a hierarchical porous structure and a specific surface area of ​​2500-3000 m². 2 / g, with a pore size distribution range of 1.2-40nm, wherein the number of MXene layers is ≤6, and the surface of MXene has abundant functional groups such as hydroxyl and carboxyl groups, which are combined with carbon fibers and CH3-MIL-101(Fe) crystals through hydrogen bonds or van der Waals forces; MXene and CH3-MIL-101(Fe) are uniformly distributed on the surface of the composite material.

[0018] Furthermore, the present invention also provides an application of the above-mentioned carbon fiber-based flower-shaped MXene / CH3-MIL-101(Fe) three-dimensional inorganic foam in photothermal catalytic oxidation of VOCs; wherein, the CH3-MIL-101(Fe) introduces methyl groups by replacing traditional terephthalic acid with 2-methyl-1,4-phthalic acid to achieve hydrophobic and oleophilic properties, and forms a uniformly distributed hydrophilic-hydrophobic composite structure with hydrophilic MXene, thereby achieving uniform adsorption of reaction gases of different polarities such as water vapor, oxygen, and benzene series VOCs, and solving the problem of low reaction gas contact efficiency caused by the uneven hydrophilic-hydrophobic sites of traditional catalysts.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] ① This invention uses the hydrophilic surface of MXene to adsorb water vapor and oxygen, and the hydrophobic and oleophilic surface of CH3-MIL-101(Fe) to adsorb benzene series VOCs, forming a uniformly distributed hydrophilic-hydrophobic composite structure, which solves the problem of low reaction gas contact efficiency caused by the uneven hydrophilic-hydrophobic sites of traditional catalysts.

[0021] ②The plasmon effect of MXene endows the material with excellent photothermal conversion capability (the surface temperature of the material reaches about 130°C after 15 minutes of irradiation with a 500W xenon lamp). In synergy with the uniformly distributed hydrophilic and hydrophobic active sites of the composite material, the photothermal catalytic oxidation reaction is carried out with high efficiency. The toluene conversion rate is significantly improved compared with photocatalysis and thermal catalysis alone, with a toluene conversion rate ≥83%, and the catalyst deactivation rate is <10% after 60 hours of continuous operation.

[0022] ③ The flower-shaped three-dimensional porous substrate design provides a hierarchical porous structure and network channels, which enhances mass transfer efficiency and gas contact area. At the same time, the macroscopic structure of the three-dimensional inorganic foam facilitates recycling and reuse, solving the problems of difficult recovery and easy deactivation of powdered catalysts. It has significant application advantages in industrial waste gas treatment, indoor air purification and other fields. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 Preparation method of carbon fiber-based flower-shaped MXene / CH3-MIL-101(Fe) three-dimensional inorganic foam.

[0025] Figure 2SEM image of carbon fiber-based flower-shaped MXene / CH3-MIL-101(Fe) three-dimensional inorganic foam prepared in Example 1.

[0026] Figure 3 XRD diffraction pattern of carbon fiber-based flower-shaped MXene / CH3-MIL-101(Fe) three-dimensional inorganic foam prepared in Example 2.

[0027] Figure 4 Contact angle test of carbon fiber-based flower-shaped MXene three-dimensional substrate (a) and carbon fiber-based flower-shaped MXene / CH3-MIL-101(Fe) three-dimensional inorganic foam prepared in Example 3 (b).

[0028] Figure 5 Catalytic activity curve (a) and conversion temperature curve (b) of the carbon fiber-based flower-shaped MXene / CH3-MIL-101(Fe) three-dimensional inorganic foam prepared in Example 1 as a catalyst. Detailed Implementation

[0029] This invention details the preparation method and performance characterization of carbon fiber-based flower-shaped MXene / CH3-MIL-101(Fe) three-dimensional inorganic foam through the following embodiments. The parameters of each embodiment are optimized and adjusted within the scope defined in the claims to form a three-dimensional foam structure with uniform hydrophilic and hydrophobic distribution, thereby achieving the application effect of highly efficient photothermal catalytic oxidation of VOCs.

[0030] Example 1

[0031] Preparation method of carbon fiber-based flower-shaped MXene / CH3-MIL-101(Fe) three-dimensional inorganic foam as follows Figure 1 20g of carbon fiber was cut into 2cm segments and placed in a 90℃ constant temperature water bath. It was then immersed in a 500mL ultrapure aqueous solution containing 4.0g NaOH, 2mL Triton X-100, and 0.5g citric acid for 60 minutes to remove surface impurities. Subsequently, it was transferred to anhydrous ethanol for ultrasonic cleaning for 30 minutes, dried at 50℃ for 8 hours, and then placed in a plasma treatment machine. Compressed air was used at 100W power for 60-180 seconds to activate the surface. Finally, the treated carbon fiber was dried at 80℃ for 8 hours to obtain pretreated carbon fiber.

[0032] Weigh 0.5g of Ti3AlC2 powder and add 100mL of a mixed solution of 9mol / L HCl and LiF prepared at a molar ratio of 1:0.25. Etch at 35℃ with a stirring rate of 400rpm for 24 hours. Centrifuge at 3500rpm and wash until pH=6.0 to obtain a multilayer MXene precipitate. Add 90mL of deionized water and sonicate. Then, use a cell disruptor under nitrogen protection and sonicate at 200W power with an intermittent pulse mode of "on for 3 seconds / off for 2 seconds" for 6 hours to obtain a few-layer MXene colloidal solution with ≤6 layers.

[0033] Pretreated carbon fibers were immersed in MXene colloidal solution and sonicated in an ice bath for 30 minutes under N2 protection to promote adsorption and aggregation. After drying at 60°C for 2 hours, they were re-immersed in the solution and freeze-dried (pre-freezing temperature -60°C, vacuum degree <10Pa, drying time 36 hours, freezing rate 5°C / min) to form a flower-shaped three-dimensional porous substrate.

[0034] 4 mmol FeCl3•6H2O and 4 mmol 2-methyl-1,4-phthalic acid were dissolved in 80 mL DMF, and 1 mL acetic acid was added and stirred for 1 hour. The substrate was immersed in the solution and then transferred to a hydrothermal reactor, where it was reacted at 80 °C for 8 hours to achieve in-situ growth. After the reaction, the substrate was washed three times alternately with DMF and ethanol, and then vacuum dried at 60 °C for 12 hours to obtain carbon fiber-based flower-like MXene / CH3-MIL-101(Fe) three-dimensional inorganic foam. The specific surface area of ​​the composite material was measured to be 2750 m² using an Autosorb-1 fully automated surface area and pore size distribution analyzer from Quantachrome, USA. 2 / g, with a pore size distribution ranging from 1.5 to 25 nm. The microstructure shows that MXene and CH3-MIL-101(Fe) are uniformly distributed on the surface of the composite material. Figure 2 ).

[0035] Example 2

[0036] After cutting the carbon fiber into 1cm segments, take 18g of the segments and place them in an 85℃ water bath. Immerse them in a 400mL ultrapure aqueous solution containing 3g NaOH, 1mL Triton X-100, and 0.4g citric acid for 45 minutes. Then, transfer them to anhydrous ethanol for ultrasonic cleaning for 20 minutes, dry them at 60℃ for 10 hours, and then place them in a plasma treatment machine. Treat them with compressed air at 150W power for 60-180 seconds. Finally, dry the treated carbon fiber at 75℃ for 6 hours.

[0037] Weigh 0.3g of Ti3AlC2 powder and add 80mL of a mixed solution of 8mol / L HCl and LiF prepared at a molar ratio of 1:0.22. Etch at 30℃ with a stirring rate of 350rpm for 20 hours. Centrifuge at 3000rpm and wash until pH=5.8 to obtain a multilayer MXene precipitate. Add 80mL of deionized water and sonicate. Then, use a cell disruptor under nitrogen protection and sonicate at 190W power with an intermittent pulse mode of "4 seconds on / 3 seconds off" for 5.5 hours to obtain a few-layer MXene colloid.

[0038] Carbon fibers were immersed in a colloid and then sonicated in an ice bath for 40 minutes, followed by drying at 60°C for 2.5 hours. A flower-like substrate was formed by freeze-drying at -55°C under a vacuum of <12 Pa for 50 hours. 5 mmol of FeCl3•6H2O and 5 mmol of 2-methyl-1,4-phthalic acid were dissolved in 90 mL of DMF, and 1.5 mL of acetic acid was added and stirred for 1.5 hours. After immersion in the substrate, a hydrothermal reaction was carried out at 85°C for 13 hours. After washing and drying, a three-dimensional inorganic foam was obtained. The specific surface area of ​​this composite material was measured to be 2600 m² using an Autosorb-1 fully automated surface area and pore size distribution analyzer from Quantachrome (USA). 2 / g, with a pore size distribution ranging from 1.2 to 20 nm. The X-ray diffraction peaks show the presence of carbon fibers, MXene, and CH3-MIL-101(Fe) components on the surface. Figure 3 ).

[0039] Example 3

[0040] After cutting the carbon fiber into 3cm segments, take 22g of each segment and immerse it in a 550mL ultrapure aqueous solution containing 4.5g NaOH, 2.5mL Triton X-100, and 0.55g citric acid in a 90℃ water bath for 60 minutes. Then, transfer it to anhydrous ethanol for ultrasonic cleaning for 30 minutes, dry it at 75℃ for 9 hours, and then place it in a plasma treatment machine. Treat it with compressed air at 100W power for 60-180 seconds. Finally, dry the treated carbon fiber at 80℃ for 9 hours.

[0041] Weigh 0.6g of Ti3AlC2 powder and add 100mL of a mixed solution of 9.5mol / L HCl and LiF prepared at a molar ratio of 1:0.26. Etch at 35℃ with a stirring rate of 400rpm for 24 hours. Centrifuge at 3500rpm and wash until pH=6.0 to obtain a multilayer MXene precipitate. Add 95mL of deionized water and sonicate. Then, use a cell disruptor under nitrogen protection and sonicate at 210W power with an intermittent pulse mode of "5 seconds on / 4 seconds off" for 6 hours to obtain a few layers of MXene colloid.

[0042] Carbon fibers were immersed in a colloid and then sonicated in an ice bath for 30 minutes, followed by drying at 60°C for 2 hours. A freeze-drying process was then performed, pre-freezing at -60°C under a vacuum of <10 Pa and drying for 48 hours to form a carbon fiber-based flower-like MXene three-dimensional substrate. 4.5 mmol FeCl3•6H2O and 4.5 mmol 2-methyl-1,4-phthalic acid were dissolved in 85 mL DMF, and 1.2 mL acetic acid was added and stirred for 1 hour. After immersion in the substrate, a hydrothermal reaction was carried out at 80°C for 10 hours. After washing and drying, a three-dimensional inorganic foam was obtained. The specific surface area of ​​this material was measured to be 2890 m² using an Autosorb-1 fully automated surface area and pore size distribution analyzer from Quantachrome (USA). 2 / g, with a pore size distribution ranging from 1.5 to 35 nm. Contact angle tests showed that the contact angle of the carbon fiber-based flower-shaped MXene surface was 0°, indicating its superhydrophilicity, while the contact angle of the carbon fiber-based flower-shaped MXene / CH3-MIL-101(Fe) surface was 120°, indicating that the introduction of CH3-MIL-101(Fe) improved the surface hydrophobicity. Figure 4 Based on the uniform distribution of MXene and CH3-MIL-101(Fe) in the SEM image, it can be concluded that the surface has a uniform distribution of hydrophilic and hydrophobic sites.

[0043] Example 4 (Catalytic Performance Test)

[0044] The composite three-dimensional inorganic foam obtained in Example 1 was placed in a photoreactor and irradiated with a 500W xenon lamp for 30 minutes, raising the catalyst surface temperature to 130°C. The xenon lamp emitted wavelengths in the range of 300-920 nm, with main emission peak wavelengths at 465 nm, 823 nm, and 882 nm. The catalyst's absorption spectrum ranged from 250-900 nm. Toluene gas was introduced, with an initial concentration controlled at 100 mg / m³. 3 The total gas flow rate is 50 mL / min. -1 The air humidity was approximately 50%. The toluene conversion rate was measured at 85.7%, a significant improvement compared to the combined rates of photocatalysis (31.5%) and thermal catalysis (8.7%). Figure 5 ); Ignition temperature (T) 10 The conversion temperature is 105℃, and the 90% conversion temperature is (T). 90 The catalyst surface temperature was set at 133°C, and after 60 hours of continuous operation, the catalyst deactivation rate was 8.2%, achieving efficient catalytic oxidation degradation of low-concentration VOCs. The composite three-dimensional inorganic foam obtained in Example 2 was placed in a photoreactor and irradiated with a 500W xenon lamp for 35 minutes, raising the catalyst surface temperature to 133°C. Toluene gas was then introduced, with an initial concentration controlled at 100 mg / m³. 3 The total gas flow rate is 50 mL / min. -1The air humidity was approximately 50%. The toluene conversion rate was measured at 82.4%, a significant improvement compared to the combined rates of photocatalysis (30.2%) and thermal catalysis alone (8.6%); the ignition temperature (T0) was [not specified]. 10 The temperature is 104℃, and the 90% conversion temperature (T) is... 90 At 131℃, after 60 hours of continuous operation, the catalyst deactivation rate was 9.4%, achieving highly efficient catalytic oxidation degradation of low-concentration VOCs. Figure 5 ).

[0045] The composite three-dimensional inorganic foam obtained in Example 3 was placed in a photoreactor and irradiated with a 500W xenon lamp for 30 minutes, raising the catalyst surface temperature to 128°C. Toluene gas was then introduced, with an initial concentration controlled at 100 mg / m³. 3 The total gas flow rate is 50 mL / min. -1 The air humidity was approximately 50%. The toluene conversion rate was measured at 83.5%, a significant improvement compared to the combined rates of photocatalysis (30.6%) and thermocatalysis (7.5%). The ignition temperature (T0) was [not specified]. 10 The temperature is 102℃, and the 90% conversion temperature (T) is... 90 At 135℃, after 60 hours of continuous operation, the catalyst deactivation rate was 9.7%, achieving efficient catalytic oxidation degradation of low-concentration VOCs.

[0046] The present invention provides a carbon fiber-based flower-shaped MXene / CH3-MIL-101(Fe) three-dimensional inorganic foam. MXene has a superhydrophilic surface, while CH3-MIL-101(Fe) is hydrophobic and oleophilic. The uniform distribution of both on the material surface ensures a uniform distribution of hydrophilic and hydrophobic sites on the composite material surface. The plasmon resonance effect of MXene endows the three-dimensional inorganic foam with excellent photothermal conversion capabilities, promoting the photothermal catalytic reaction of water vapor, oxygen, and VOCs such as benzene series compounds. The hydrophilic properties of MXene are beneficial for the adsorption of water vapor and oxygen, while the hydrophobic and oleophilic properties of CH3-MIL-101(Fe) are beneficial for the adsorption of hydrophobic VOCs. The uniform distribution of both solves the problem of low contact efficiency of reaction gases caused by the uneven distribution of hydrophilic and hydrophobic sites in traditional catalysts. As a photothermal catalyst, this three-dimensional inorganic foam exhibits highly efficient catalytic oxidation performance for benzene series VOCs. Moreover, the three-dimensional foam structure facilitates recycling and reuse, and has broad application prospects in industrial waste gas treatment, indoor air purification, and other fields. It achieves synergistic optimization of high contact area, rapid mass transfer, and efficient reaction in the photothermal catalytic oxidation process of VOCs.

Claims

1. A method for preparing carbon fiber-based flower-shaped MXene / CH3-MIL-101(Fe) three-dimensional inorganic foam, characterized in that, Includes the following steps: (1) Carbon fiber pretreatment: Cut the carbon fiber into small pieces and wash them in an ultrapure water washing solution containing NaOH, Triton X-100 and citric acid under hot water bath conditions to remove surface impurities. The carbon fibers were then ultrasonically cleaned and dried with anhydrous ethanol, and then placed in a plasma treatment machine for plasma treatment with compressed air to introduce polar groups, including hydroxyl and carboxyl groups; finally, the treated carbon fibers were dried. (2) MXene preparation: 0.3-0.7g Ti3AlC2 was etched with hydrochloric acid and lithium fluoride to obtain multilayer MXene; the multilayer MXene was then ultrasonically dispersed in 80-100mL deionized water to form a colloidal solution, and ultrasonically exfoliated using a cell disruptor under an inert atmosphere to obtain few-layer Ti3C2T with ≤6 layers. x Colloidal solutions of MXene-based materials; (3) Three-dimensional substrate construction: The carbon fibers pretreated in step (1) are immersed in the MXene colloidal solution obtained in step (2) and ultrasonically cooled in an ice bath under inert gas protection to promote the adsorption and aggregation of MXene on the carbon fiber surface; then they are taken out and dried, and then re-immersed in the MXene colloidal solution for freeze-drying to form a flower-shaped three-dimensional porous substrate. (4) CH3-MIL-101(Fe) in situ loading: FeCl3•6H2O and 2-methyl-1,4-phenylenediamine were first dissolved in DMF, and acetic acid was added and stirred to obtain a precursor solution; then the substrate was immersed in the precursor solution and hydrothermal reaction was carried out to achieve in situ growth; after the reaction was completed, the substrate was washed and dried in sequence to obtain a composite three-dimensional inorganic foam with uniformly distributed hydrophilic and hydrophobic sites.

2. The preparation method according to claim 1, characterized in that, In step (1), the hot water bath temperature is 85-95℃, the length of the carbon fiber is 1-5cm, the mass-to-volume ratio of the carbon fiber to the ultrapure water washing solution is 1:20~1:30g / mL, and the washing time is 45-75 minutes; in the ultrapure water washing solution, the mass-to-volume concentration of NaOH is 6-10g / L, the volume concentration of Triton X-100 is 0.2%-0.6%, and the mass-to-volume concentration of citric acid is 0.8-1.2g / L; during plasma treatment, the treatment is carried out at a power of 100-150W for 60-180 seconds; the drying temperature is 50-85℃, and the drying time is 6-10 hours.

3. The preparation method according to claim 1, characterized in that, In step (2), the concentration of hydrochloric acid is 8-10 mol / L, the molar ratio of HCl to LiF in hydrochloric acid is 1:0.2-1:0.3, the etching temperature is 30-40℃, and the etching time is 20-28 hours.

4. The preparation method according to claim 1, characterized in that, In step (2), during ultrasonic stripping, intermittent pulse mode ultrasound is used, with a single ultrasound time of 3-5 seconds, an interval time of 2-4 seconds, a total ultrasound time of 3.5-6.5 hours, an ultrasound power of 190-210W, and an inert atmosphere of nitrogen with a nitrogen flow rate of 40-80mL / min.

5. The preparation method according to claim 1, characterized in that, In step (3), the ice bath is ultrasonic for 20-40 minutes; the drying temperature is 60±5℃ and the drying time is 1.5-2.5 hours.

6. The preparation method according to claim 1, characterized in that, In step (3), the freeze-drying temperature is -65℃ to -55℃, the vacuum degree is <12Pa, the drying time is 20-50 hours, and the freezing rate is 4-8℃ / min.

7. The preparation method according to claim 1, characterized in that, In step (4), the feed ratio of FeCl3•6H2O, 2-methyl-1,4-phthalic acid, DMF and acetic acid in the precursor solution is (3-5) mmol: (3-5) mmol: (70-90) mL: (0.5-1.5) mL; the stirring time is 0.5-1.5 hours.

8. The preparation method according to claim 1, characterized in that, In step (4), the hydrothermal reaction temperature is 75-85℃ and the hydrothermal reaction time is 5-13 hours. After the reaction is completed, DMF and ethanol are washed alternately 2-4 times, and vacuum dried at 55-65℃ for 10-14 hours.

9. A carbon fiber-based flower-shaped MXene / CH3-MIL-101(Fe) three-dimensional inorganic foam prepared by the preparation method according to any one of claims 1-8, characterized in that, The three-dimensional inorganic foam has a hierarchical porous structure and a specific surface area of ​​2500-3000 m². 2 / g, with a pore size distribution ranging from 1.2 to 40 nm.

10. The application of the carbon fiber-based flower-shaped MXene / CH3-MIL-101(Fe) three-dimensional inorganic foam according to claim 9 as a photothermal catalyst in the photothermal catalytic oxidation of VOCs.

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