Method for preparing a mesoporous carbon film with photo-thermal conversion function using block copolymer

Abstract

The application discloses a method for preparing a uniform-pore carbon film with a photo-thermal conversion function by using a block copolymer, and comprises the following steps: S1, a concentrated solution of the block copolymer is scraped to form a film, and after volatilization for 5-35 seconds, the film is immersed in water, and a uniform-pore film is obtained after drying; S2, a fluorine-containing super strong liquid acid and a crosslinking agent are configured into a reaction solution according to a molar ratio of 1:1-10:1, the uniform-pore film is immersed in the reaction solution, after the reaction is completed, the film is taken out, washed with an aqueous solution with a pH value of 10-13, and a super-crosslinked uniform-pore film is obtained after drying; and S3, the super-crosslinked uniform-pore film is transferred to a tube furnace, carbonized by high-temperature calcination under an inert atmosphere, taken out after cooling to room temperature, and a uniform-pore carbon film is obtained. The uniform-pore carbon film prepared by the method has a good photo-thermal conversion capacity, and the superior stability of the crosslinked uniform-pore film in harsh media is preserved, and the preparation method is simple and has strong universality.

Description

Technical Field

[0001] This invention relates to the fields of membrane separation and new materials, and in particular to a method for preparing a uniformly porous carbon membrane with photothermal conversion function using block copolymers. Background Technology

[0002] Solar energy is a clean, renewable, and green energy source. Its efficient development and utilization have garnered global attention and are also a crucial direction for my country's sustainable development strategy. Solar-driven evaporation, converting light energy into heat energy, is a highly efficient and emerging method of solar energy utilization. Using solar-driven evaporation technology for media separation and purification is a low-cost, low-energy-consumption, and pollution-free separation method with broad application prospects in seawater desalination, wastewater treatment, and organic matter separation.

[0003] Photothermal materials are the core of solar-driven evaporation technology. Photothermal film materials are among the most promising photothermal materials currently available. As a photothermal film material for solar-driven water evaporation technology, it should possess characteristics such as good light absorption, a rough porous surface, abundant interconnected pore structure, and a good heat insulation layer. Related technologies often use carbon nanotubes, noble metal nanomaterials, semiconductor materials, or organic polymers as light-absorbing materials to prepare photothermal conversion films. However, these materials suffer from problems such as complex preparation processes, high costs, and poor stability. Their application in extreme environments such as high temperature, high humidity, and high corrosion, such as in the separation of multiple media including organic solvents, highly acidic and alkaline solutions, and oil-water emulsions, is limited. Therefore, a photothermal conversion film material with a simple preparation process, broad applicability, and high stability is highly anticipated.

[0004] Block copolymers stand out among many materials due to their ability to self-assemble into various precisely controlled periodic nanostructures. In recent years, uniformly porous membranes based on block copolymers have developed rapidly. Due to their high porosity, uniform pore size, and controllable pore dimensions, they are considered high-performance separation membranes with great development potential. Furthermore, their high surface porosity, vertically penetrating channels throughout the separation layer, and interconnected porous support layer structure demonstrate great potential for development into photothermal conversion membranes. The vertical cylindrical channels in the separation layer exhibit strong capillary effects, and the interconnected pores in the support layer ensure smooth medium transport and supply during evaporation; these structural features are among the preferred structures for photothermal conversion membranes. These results indicate that uniformly porous membranes have great potential to be transformed into highly stable photothermal conversion membranes. However, because purely polymer-based uniformly porous membrane materials themselves do not possess photothermal conversion capabilities, and the currently disclosed uniformly porous membranes have low crosslinking degrees, they cannot undergo non-destructive carbonization; therefore, they have not been used as photothermal conversion membranes in the field of solar-driven evaporation. In summary, a highly stable, photothermal-converting, uniformly porous carbon membrane is still needed to achieve material separation in harsh environments. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention proposes a method for preparing uniformly porous carbon membranes with photothermal conversion capabilities using block copolymers. This method uses block copolymers as raw materials to prepare uniformly porous membranes. While maintaining the uniform porous structure, a highly cross-linked uniformly porous membrane with ultra-high cross-linking degree is prepared through efficient catalysis with a fluorine-containing super-strong liquid acid. Finally, the ultra-cross-linked uniformly porous membrane is subjected to high-temperature carbonization treatment to obtain the uniformly porous carbon membrane. The uniformly porous carbon membrane prepared by this method has self-supporting characteristics, customizable pore size, and excellent photothermal conversion efficiency, showing promising applications in the thermal evaporation and separation of homologous compounds, solvent recovery, and chemical microreactors.

[0006] The specific technical solution of the present invention is as follows:

[0007] A method for preparing a uniformly porous carbon film with photothermal conversion function using block copolymers includes the following steps:

[0008] S1: A concentrated solution of the block copolymer is coated onto a film, evaporated in air for 5-35 seconds, then immersed in water and dried to obtain a uniformly porous membrane; the block copolymer is selected from any one of polystyrene-block-polyacrylic acid, polystyrene-block-poly4-vinylpyridine, polyisobutylene-block-polystyrene-block-poly4-vinylpyridine, and polystyrene-block-poly4-vinylpyridine-block-polyethylene glycol;

[0009] S2: A reaction solution is prepared by mixing a fluorinated super-strong liquid acid and a crosslinking agent in a molar ratio of 1:1 to 10:1. The uniformly porous membrane is then immersed in the reaction solution. After the reaction is complete, the membrane is removed, washed with an aqueous solution at pH 10-13, and dried to obtain a super-crosslinked uniformly porous membrane. The molar ratio of the fluorinated super-strong liquid acid to the crosslinking agent is in the range of 1:1 to 10:1. If the reaction solution ratio is lower than the minimum ratio limit, the crosslinking of the super-crosslinked uniformly porous membrane will be too low, and it will not be able to maintain the uniformly porous structure well. If the reaction solution ratio is too high, i.e., higher than the maximum ratio limit, the super-crosslinked uniformly porous membrane will be brittle and its mechanical properties will decrease.

[0010] S3: The dried hypercrosslinked uniformly porous membrane is transferred to a tube furnace and calcined at high temperature in an inert atmosphere to carbonize it. After cooling to room temperature, it is taken out to obtain a uniformly porous carbon membrane.

[0011] Furthermore, the molecular weight of the block copolymer ranges from 80 to 750 kg / mol, and the mass content of polystyrene in the block copolymer ranges from 70 to 90 wt%. Within the preferred molecular composition range, the block copolymer can better exert its self-assembly capability and form a well-defined uniform porous structure.

[0012] Furthermore, the concentration range of the concentrated solution of the block copolymer is 12.5–30 wt%. Only within a suitable concentration range can the block copolymer effectively self-assemble into regular, periodic nanostructures. When the concentration is too low, the assembly driving force is weak, making it difficult to form a uniform porous structure; when the concentration is too high, the polymer solution viscosity is high, making it difficult for the molecular chains to move, thus affecting the self-assembly process.

[0013] Further, in step S1, the thickness of the uniformly porous membrane layer ranges from 20-300 nm, and the pore size ranges from 5-100 nm. After different types of block copolymer raw materials are used to prepare uniformly porous membranes, uniformly porous layers of corresponding sizes and thicknesses will form on the surface. By selecting the appropriate block copolymer composition and concentration ratio, a separation layer with a thickness in the range of 20-300 nm and surface pores with a size in the range of 5-100 nm can be pre-formed. The separation layer of the uniformly porous membrane has a vertical cylindrical channel structure, exhibiting a strong capillary effect, which is beneficial for rapid water transport during photothermal conversion. If the transport channel is too short, the capillary effect will be weak, hindering water transport; however, if the transport channel is too long, the transport time will increase, reducing efficiency. The pore size range of the uniformly porous membrane is limited to 5-100 nm, which is constrained by the characteristics of the block copolymer itself and represents the achievable pore size range through self-assembly technology.

[0014] Further, in S2, the fluorinated super-strong liquid acid is selected from any one of trifluoromethanesulfonic acid, trifluoromethanesulfonic anhydride, and bis(trifluoromethanesulfonamide), and the crosslinking agent is selected from dimethylformaldehyde or diethanolformaldehyde. Compared with solid Lewis acids, fluorinated super-strong liquid acids have higher catalytic activity in the crosslinking process of homogeneous porous membranes based on Friedel-Crafts chemistry. As a liquid acid, it does not form solid residues on the membrane surface to block the membrane pores during the reaction, and it also avoids the possibility of metal ions being introduced onto the membrane surface by metal salt catalysts. Among fluorinated super-strong liquid acids, the three preferred ones mentioned above have better catalytic effects. Dimethylformaldehyde and diethanolformaldehyde, as low-cost and highly active bifunctional crosslinking agents, can rapidly establish connecting bridges between the molecular chains of homogeneous porous membranes under the catalysis of fluorinated super-strong acids, enabling the homogeneous porous membrane to be rapidly crosslinked. Other alkyl halide crosslinking agents have low reactivity and generate harmful byproducts such as hydrochloric acid during the reaction.

[0015] Furthermore, in step S2, the reaction temperature ranges from 90 to 150°C, and the reaction time ranges from 6 to 24 hours. The reaction process determines the degree of crosslinking of the hypercrosslinked uniformly porous membrane. If the reaction temperature is too low or the reaction time is too short, the degree of crosslinking of the hypercrosslinked uniformly porous membrane will be low, resulting in the inability to maintain the membrane pore structure after carbonization. If the reaction temperature is too high or the reaction time is too long, the hypercrosslinked uniformly porous membrane will also become brittle, and its mechanical properties will decrease.

[0016] Furthermore, in step S3, the isothermal carbonization temperature range is 200-1300℃, the heating rate from room temperature to the carbonization temperature ranges from 1-10℃ / min, and the isothermal carbonization time ranges from 0.5-10 hours. As a key step in preparing a uniformly porous carbon film, the carbonization temperature and isothermal duration determine the degree of carbonization and photothermal conversion capability of the prepared hypercrosslinked uniformly porous film after its transformation into a uniformly porous carbon film. If the carbonization conditions are too weak, the degree of carbonization will be low, resulting in poor light absorption and low photothermal conversion efficiency of the prepared uniformly porous carbon film; if the carbonization conditions are too strong, the pore structure of the prepared uniformly porous carbon film will be difficult to maintain, resulting in poor medium transport capability and low photothermal conversion effect. Carbonization within the preferred range can achieve a balance between the two.

[0017] A uniformly porous carbon membrane with photothermal conversion function is prepared according to the method for preparing a uniformly porous carbon membrane with photothermal conversion function using block copolymers.

[0018] Furthermore, the pore size of the uniformly porous carbon membrane changes by less than 15% compared to before carbonization. During the transformation of the hypercrosslinked uniformly porous membrane to carbonization, the membrane area shrinks and the pore size decreases due to changes in molecular structure. The uniformly porous membrane prepared by the method of this invention has an ultra-high degree of crosslinking, and the pore size changes little during carbonization, with the maximum change not exceeding 15%, ensuring that the uniformly porous structure does not undergo significant changes.

[0019] Furthermore, the ratio of the D-band to G-band peak intensities of the uniformly porous carbon film in the Raman spectrum is not less than 0.5; under standard solar radiation, the photothermal conversion efficiency of the uniformly porous carbon film is greater than 0.33.

[0020] The beneficial effects of this invention are:

[0021] (1) The method of the present invention prepares a highly cross-linked uniform porous membrane under the catalysis of a fluorine-containing super strong liquid acid. The super strong fluorine-containing liquid acid is used as the catalyst for cross-linking the uniform porous membrane. It has the advantages of high cross-linking efficiency, high cross-linking density and no pore blockage, and solves the problems of low cross-linking efficiency and difficulty in maintaining uniform porous structure during carbonization caused by conventional cross-linking catalysts.

[0022] (2) The uniformly porous carbon membrane prepared by the method of the present invention is obtained by high-temperature carbonization of a highly cross-linked super-cross-linked uniformly porous membrane, which preserves the excellent structural stability of the super-cross-linked uniformly porous membrane in harsh media, including strong protic solvents such as dimethylformamide and acid and alkaline solutions at room temperature or high temperature.

[0023] (3) The uniformly porous carbon membrane prepared by the method of the present invention has good photothermal conversion ability, which makes it promising for application in the thermal evaporation separation of homologous substances, solvent recovery, water purification, chemical microreactors and other fields.

[0024] (4) The uniformly porous carbon membrane prepared by the method of the present invention retains the original excellent structural features of the uniformly porous membrane during the carbonization process, including high surface porosity, uniform pore size, vertically penetrating separation layer and interconnected porous support layer.

[0025] (5) The method of the present invention is simple and universal, and can be cross-linked and carbonized in block copolymers with different molecular weights and chemical compositions. Furthermore, the pore size of the uniformly porous carbon membrane can be customized within a certain range. Attached Figure Description

[0026] Figure 1 These are scanning electron microscope (SEM) images of the surface of the super-crosslinked uniformly porous membrane and the uniformly porous carbon membrane prepared in Example 1 of the present invention, wherein (a) is a scanning electron microscope image of the surface of the super-crosslinked uniformly porous membrane and (b) is a scanning electron microscope image of the surface of the uniformly porous carbon membrane.

[0027] Figure 2 These are cross-sectional scanning electron microscope (SEM) images of the hypercrosslinked uniformly porous membrane and the uniformly porous carbon membrane prepared in Example 1 of this invention, wherein (a) is a surface SEM image of the hypercrosslinked uniformly porous membrane and (b) is a surface SEM image of the uniformly porous carbon membrane.

[0028] Figure 3 These are X-ray diffraction patterns of uniformly porous carbon films prepared under different carbonization conditions in Examples 1 and 3 of this invention.

[0029] Figure 4 These are Raman spectra of uniformly porous carbon films prepared under different carbonization conditions in Examples 1 and 3 of this invention.

[0030] Figure 5 The figure shows the results of a liquid evaporation experiment on solar-driven photothermal conversion using the uniformly porous membrane, the hypercrosslinked uniformly porous membrane, and the uniformly porous carbon membrane prepared in Example 1 of this invention.

[0031] Figure 6 These are scanning electron microscope (SEM) images of the surface of the super-crosslinked uniformly porous membrane and the uniformly porous carbon membrane prepared in Example 2 of the present invention, wherein (a) is a scanning electron microscope image of the surface of the super-crosslinked uniformly porous membrane and (b) is a scanning electron microscope image of the surface of the uniformly porous carbon membrane.

[0032] Figure 7 These are cross-sectional scanning electron microscope (SEM) images of the hypercrosslinked uniformly porous membrane and the uniformly porous carbon membrane prepared in Example 2 of the present invention, wherein (a) is a surface SEM image of the hypercrosslinked uniformly porous membrane and (b) is a surface SEM image of the uniformly porous carbon membrane.

[0033] Figure 8 These are the Fourier transform infrared spectra of the hypercrosslinked uniformly porous membrane and the uniformly porous carbon membrane prepared in Example 2 of this invention. Detailed Implementation

[0034] The present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments. The objectives and effects of the present invention will become clearer as a result. The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0035] Example 1

[0036] A method for preparing a uniformly porous carbon film with photothermal conversion function using block copolymers includes the following steps:

[0037] S1: Preparation of the uniformly porous membrane: A polystyrene-block-polyacrylic acid (PS-b-PAA) block copolymer with a molecular weight of 83 kg / mol, wherein PS accounts for 84.3 wt%, was dissolved in 1,4-dioxane at a concentration of 22 wt% to prepare a casting solution (i.e., a concentrated solution of the block copolymer). After complete dissolution, the casting solution was coated onto a clean glass plate using a 150 μm thick doctor blade. After evaporation for 10 s, the plate was immersed in water for phase inversion to form a membrane. The formed film was removed from the coagulation bath and dried to obtain a uniformly porous membrane. The separation layer thickness of the uniformly porous membrane was 300 nm, and the pore size was 13 nm.

[0038] S2: Crosslinking: Prepare a reaction solution with a molar ratio of trifluoromethanesulfonic acid to dimethylformaldehyde of 7:1. Immerse the prepared uniformly porous membrane in the reaction solution and react at 100℃ for 12 h. After the reaction, remove the membrane, rinse it three times with an aqueous solution of pH=13, and then air dry to obtain the hypercrosslinked uniformly porous membrane. Electron microscopy characterizes the surface structure of the hypercrosslinked uniformly porous membrane as follows: Figure 1 As shown in (a), the cross-sectional structure of the hypercrosslinked uniformly porous membrane is characterized by electron microscopy as follows: Figure 2 As shown in (a), its surface pore size is 13.2 nm, and the cross-section shows a clearly visible uniformly porous separation layer.

[0039] S3: Carbonization: The dried, hypercrosslinked, uniformly porous membrane was placed flat in a quartz boat, covered with a quartz sheet, and then transferred to a tube furnace. Under a nitrogen atmosphere, the temperature was increased to 800°C at a rate of 5°C / min, and carbonized at 800°C for 30 min. After cooling to room temperature, the membrane was removed to obtain a uniformly porous carbon membrane. The structure of the uniformly porous carbon membrane was characterized using electron microscopy, as shown below. Figure 1 As shown in (b), the surface exhibits a hexagonal ordered pore morphology consistent with the hypercrosslinked uniformly porous membrane, indicating that the high degree of crosslinking of the hypercrosslinked uniformly porous membrane allows it to maintain its surface pore morphology unchanged during carbonization. The surface pores were quantified, and the pore size was found to be 12.4 nm, representing a 6% change in size compared to the hypercrosslinked uniformly porous membrane. Figure 2 As shown in (b), the cross-section of the uniformly porous carbon membrane exhibits a separation layer and support layer structure similar to that of the hypercrosslinked uniformly porous membrane, further demonstrating the stability of the hypercrosslinked membrane structure during the carbonization process.

[0040] like Figure 3 As shown, X-ray diffraction (XRD) reveals that the carbonized uniformly porous carbon film exhibits two sets of peaks at 23.6 and 43.7, indicating the presence of amorphous carbon components. Figure 4 As shown, the Raman spectrum reveals D and G band peaks with a peak intensity ratio of 0.93, indicating a high degree of graphitization in the uniformly porous carbon film.

[0041] Photothermal conversion test:

[0042] The prepared uniformly porous carbon membrane was floated on water using a heat-insulating foam board. After stabilizing under standard sunlight for 30 minutes, the change in water mass was recorded over one hour. Simultaneously, an infrared thermometer was used to record the change in membrane surface temperature during evaporation. The results are as follows: Figure 5 As shown, the water evaporation rate of the original membrane (i.e., the uniformly porous membrane prepared in S1) is 1.7 kg m³. -2 h -1 The water evaporation rate of the hypercrosslinked uniformly porous membrane is 2.8 kg m³. -2 h -1 The water evaporation rate of the uniformly porous carbon film is 4.2 kg m³. -2 h -1 This demonstrates that the uniformly porous carbon film prepared in this embodiment has good photothermal conversion capability.

[0043] Example 2

[0044] A method for preparing a uniformly porous carbon film with photothermal conversion function using block copolymers includes the following steps:

[0045] S1: Preparation of the uniformly porous membrane: A polystyrene-block-polyacrylic acid (PS-b-PAA) block copolymer with a molecular weight of 80 kg / mol, wherein the PS content is 70 wt%, was dissolved at a concentration of 22 wt% in a mixed solution of 1,4-dioxane (DOX) and tetrahydrofuran (THF) to prepare a casting solution (DOX / THF = 1:1). After complete dissolution, the solution was coated onto a clean glass plate using a doctor blade with a thickness of 150 μm. After evaporation for 10 s, the plate was immersed in water for phase inversion to form a membrane. The formed membrane was removed from the coagulation bath and dried to obtain a uniformly porous membrane. The separation layer thickness of the uniformly porous membrane was 300 nm, and the pore size was 13 nm.

[0046] S2: Crosslinking: Prepare a reaction solution with a molar ratio of trifluoromethanesulfonic acid to dimethylformaldehyde of 7:1. Immerse the prepared uniformly porous membrane in the reaction solution and react at 100℃ for 24 h. After the reaction, remove the membrane, rinse it three times with an aqueous solution of pH=13, and then air dry to obtain the hypercrosslinked uniformly porous membrane. Electron microscopy characterizes the surface structure of the hypercrosslinked uniformly porous membrane as follows: Figure 6 As shown in (a), the cross-sectional structure of the hypercrosslinked uniformly porous membrane is characterized by electron microscopy as follows: Figure 7As shown in (a), its surface pore size is 13.8 nm, and the cross-section shows a clearly visible uniformly porous separation layer.

[0047] S3: Carbonization: The dried, hypercrosslinked, uniformly porous membrane was placed flat in a quartz boat, covered with a quartz sheet, and then transferred to a tube furnace. Under a nitrogen atmosphere, the temperature was increased to 800°C at a rate of 5°C / min, and carbonized at 800°C for 30 min. After cooling to room temperature, the membrane was removed to obtain a uniformly porous carbon membrane. The structure of the uniformly porous carbon membrane was characterized using electron microscopy, as shown below. Figure 6 As shown in (b), the surface exhibits a hexagonal ordered pore morphology consistent with the hypercrosslinked uniformly porous membrane, indicating that the hypercrosslinked uniformly porous membrane possesses an ultra-high degree of crosslinking, enabling it to maintain its surface pore morphology during the membrane carbonization transition. The surface pores were quantified, with a pore size of 12.1 nm, representing a 12% change in size compared to the hypercrosslinked uniformly porous membrane. Figure 7 As shown in (b), the cross-sectional image of the uniformly porous carbon membrane shows a separation layer and support layer structure similar to that of the hypercrosslinked uniformly porous membrane, further demonstrating the stability of the hypercrosslinked membrane structure during carbonization.

[0048] like Figure 8 As shown, Fourier transform infrared spectroscopy characterized the chemical composition of the hypercrosslinked uniform porous membrane and the uniform porous carbon membrane, confirming that the hypercrosslinked uniform porous membrane was carbonized.

[0049] X-ray diffraction (XRD) characterization confirmed that the carbonized uniformly porous carbon film had an amorphous carbon composition. Raman spectroscopy characterized the degree of graphitization in the uniformly porous carbon film.

[0050] Photothermal conversion test:

[0051] The prepared uniformly porous carbon membrane was floated on an emulsion of octane and water through a heat-insulating foam board. After stabilizing for 30 minutes under standard sunlight, the change in water mass was recorded over one hour. At the same time, the change in membrane surface temperature during evaporation was recorded using an infrared thermometer, demonstrating that the uniformly porous carbon membrane has good photothermal conversion capability.

[0052] Example 3

[0053] A method for preparing a uniformly porous carbon film with photothermal conversion function using block copolymers includes the following steps:

[0054] S1: Preparation of the uniformly porous membrane: A polystyrene-block-polyacrylic acid (PS-b-PAA) block copolymer with a molecular weight of 83 kg / mol, wherein PS accounts for 70 wt%, was dissolved in 1,4-dioxane at a concentration of 22 wt% to prepare a casting solution. After complete dissolution, the solution was coated onto a clean glass plate using a doctor blade with a thickness of 150 μm. After evaporation for 10 s, the plate was immersed in water for phase inversion to form a membrane. The formed membrane was removed from the coagulation bath and dried to obtain a uniformly porous membrane. The separation layer thickness of the uniformly porous membrane was 200 nm, and the pore size was 12 nm.

[0055] S2: Crosslinking: A reaction solution with a molar ratio of trifluoromethanesulfonic acid to dimethylformaldehyde of 7:1 was prepared. The uniformly porous membrane prepared above was immersed in the reaction solution and reacted at 100℃ for 12 h. After the reaction was completed, the membrane was removed, rinsed three times with an aqueous solution of pH=13, and then dried to obtain a hypercrosslinked uniformly porous membrane. Its surface and cross-sectional structure were characterized by electron microscopy.

[0056] S3: Carbonization: The dried, hypercrosslinked, uniformly porous membrane was placed flat in a quartz boat, covered with a quartz sheet, and then transferred to a tube furnace. Under a nitrogen atmosphere, the temperature was increased to 600°C at a rate of 5°C / min, and carbonized at 600°C for 30 min. After cooling to room temperature, the membrane was removed to obtain a uniformly porous carbon membrane. The structure of the uniformly porous carbon membrane was characterized by electron microscopy, confirming that the surface morphology remained unchanged during the carbonization transition.

[0057] like Figure 3 As shown, X-ray diffraction (XRD) revealed two sets of peaks at 23.6 and 43.7 Å after carbonization, indicating amorphous carbon components. Figure 4 As shown, the Raman spectrum reveals D and G band peaks with a peak intensity ratio of 0.87, indicating a high degree of graphitization in the uniformly porous carbon film.

[0058] Photothermal conversion test:

[0059] The prepared uniformly porous carbon membrane was floated on water using a heat-insulating foam board. After stabilizing for 30 minutes under standard sunlight, the change in water quality was recorded over one hour. Simultaneously, an infrared thermometer was used to record the change in membrane surface temperature during evaporation, demonstrating that the uniformly porous carbon membrane has good photothermal conversion capabilities.

[0060] Example 4

[0061] A method for preparing a uniformly porous carbon film with photothermal conversion function using block copolymers includes the following steps:

[0062] S1: Preparation of the uniformly porous membrane: A polystyrene-block-polyacrylic acid (PS-b-PAA) block copolymer with a molecular weight of 101 kg / mol, wherein PS accounts for 90 wt%, was dissolved in 1,4-dioxane at a concentration of 20 wt% to prepare a casting solution. After complete dissolution, the solution was coated onto a clean glass plate using a doctor blade with a thickness of 100 μm. After evaporation for 15 s, the plate was immersed in water for phase inversion to form a membrane. The formed membrane was removed from the coagulation bath and dried to obtain the uniformly porous membrane. The separation layer thickness of the uniformly porous membrane was 150 nm, and the pore size was 15 nm.

[0063] S2: Crosslinking: A reaction solution with a molar ratio of trifluoromethanesulfonic anhydride to dimethylformaldehyde of 10:1 was prepared. The uniformly porous membrane prepared above was immersed in the reaction solution and reacted at 90℃ for 12 h. After the reaction was completed, the membrane was removed, rinsed three times with an aqueous solution of pH=13, and then dried to obtain a hypercrosslinked uniformly porous membrane. Its surface and cross-sectional structure were characterized by electron microscopy.

[0064] S3: Carbonization: The dried, hypercrosslinked, uniformly porous membrane was placed flat in a quartz boat, covered with a quartz sheet, and then transferred to a tube furnace. Under a nitrogen atmosphere, the temperature was increased to 400℃ at a rate of 3℃ / min, and carbonized at 400℃ for 10 hours. After cooling to room temperature, the membrane was removed to obtain a uniformly porous carbon membrane. The surface and cross-sectional structure of the uniformly porous carbon membrane were characterized by electron microscopy. The morphology of carbon in the uniformly porous carbon membrane was characterized by XRD. Raman spectroscopy was used to characterize the intensity ratio of the D and G band peaks, quantifying the degree of graphitization.

[0065] Photothermal conversion test:

[0066] The prepared uniformly porous carbon membrane was floated in a mixed solvent of dimethylformamide and water through a heat-insulating foam board. After stabilizing for 30 minutes under standard sunlight, the change in the mass of the liquid was recorded over one hour. At the same time, the change in the membrane surface temperature during evaporation was recorded using an infrared thermometer, demonstrating that the uniformly porous carbon membrane has good photothermal conversion capability.

[0067] Example 5

[0068] A method for preparing a uniformly porous carbon film with photothermal conversion function using block copolymers includes the following steps:

[0069] S1: Preparation of the uniformly porous membrane: A polystyrene-block-poly4-vinylpyridine (PS-b-P4VP) block copolymer with a molecular weight of 115 kg / mol, wherein PS accounts for 70 wt%, was dissolved at a concentration of 25 wt% in a mixed solvent of dimethylformamide and tetrahydrofuran to prepare a casting solution. After complete dissolution, the solution was coated onto a clean glass plate using a doctor blade with a thickness of 150 μm. After evaporation for 5 seconds, the plate was immersed in water for phase inversion to form a membrane. The formed membrane was removed from the coagulation bath and dried to obtain a uniformly porous membrane. The separation layer thickness of the uniformly porous membrane was 70 nm, and the pore size was 30 nm.

[0070] S2: Crosslinking: A reaction solution with a molar ratio of bis(trifluoromethanesulfonamide) to diethanolformal of 1:1 was prepared. The uniformly porous membrane prepared above was immersed in the reaction solution and reacted at 150°C for 24 h. After the reaction was completed, the membrane was removed, rinsed three times with an aqueous solution of pH=13, and then dried to obtain a hypercrosslinked uniformly porous membrane. Its surface and cross-sectional structure were characterized by electron microscopy.

[0071] S3: Carbonization: The dried, hypercrosslinked, uniformly porous membrane was placed flat in a quartz boat, covered with a quartz sheet, and then transferred to a tube furnace. Under a nitrogen atmosphere, the temperature was increased to 600℃ at a rate of 5℃ / min, and carbonized at 600℃ for 30 min. After cooling to room temperature, the membrane was removed to obtain a uniformly porous carbon membrane. The surface and cross-sectional structure of the uniformly porous carbon membrane were characterized by electron microscopy. The morphology of carbon in the uniformly porous carbon membrane was characterized by XRD. Raman spectroscopy was used to characterize the intensity ratio of the D-band and G-band peaks, quantifying the degree of graphitization.

[0072] Photothermal conversion test:

[0073] The prepared uniformly porous carbon membrane was floated in a mixed solvent of tetrahydrofuran and water through a heat-insulating foam board. After stabilizing for 30 minutes under standard sunlight, the change in the mass of the liquid was recorded over one hour. At the same time, the change in the membrane surface temperature during evaporation was recorded using an infrared thermometer, demonstrating that the uniformly porous carbon membrane has good photothermal conversion capability.

[0074] Example 6

[0075] A method for preparing a uniformly porous carbon film with photothermal conversion function using block copolymers includes the following steps:

[0076] S1: Preparation of the uniformly porous membrane: A polystyrene-block-poly4-vinylpyridine (PS-b-P4VP) block copolymer with a molecular weight of 290 kg / mol, wherein PS accounts for 75 wt%, was dissolved at a concentration of 25 wt% in a mixed solvent of dimethylformamide and tetrahydrofuran to prepare a casting solution. After complete dissolution, the solution was coated onto a clean glass plate using a doctor blade with a thickness of 100 μm. After evaporation for 5 seconds, the plate was immersed in water for phase inversion to form a membrane. The formed membrane was removed from the coagulation bath and dried to obtain a uniformly porous membrane. The separation layer thickness of the uniformly porous membrane was 20 nm, and the pore size was 100 nm.

[0077] S2: Crosslinking: A reaction solution with a molar ratio of bis(trifluoromethanesulfonamide) to diethanolformal of 1:1 was prepared. The uniformly porous membrane prepared above was immersed in the reaction solution and reacted at 150°C for 24 h. After the reaction was completed, the membrane was removed, rinsed three times with an aqueous solution of pH=13, and then dried to obtain a hypercrosslinked uniformly porous membrane. Its surface and cross-sectional structure were characterized by electron microscopy.

[0078] S3: Carbonization: The dried, hypercrosslinked, uniformly porous membrane was placed flat in a quartz boat, covered with a quartz sheet, and then transferred to a tube furnace. Under a nitrogen atmosphere, the temperature was increased to 600℃ at a rate of 5℃ / min, and carbonized at 600℃ for 30 min. After cooling to room temperature, the membrane was removed to obtain a uniformly porous carbon membrane. The surface and cross-sectional structure of the uniformly porous carbon membrane were characterized by electron microscopy. The morphology of carbon in the uniformly porous carbon membrane was characterized by XRD. Raman spectroscopy was used to characterize the intensity ratio of the D-band and G-band peaks, quantifying the degree of graphitization.

[0079] Photothermal conversion test:

[0080] The prepared uniformly porous carbon membrane was floated in a mixed solvent of tetrahydrofuran and water through a heat-insulating foam board. After stabilizing for 30 minutes under standard sunlight, the change in the mass of the liquid was recorded over one hour. At the same time, the change in the membrane surface temperature during evaporation was recorded using an infrared thermometer, demonstrating that the uniformly porous carbon membrane has good photothermal conversion capability.

[0081] Example 7

[0082] A method for preparing a uniformly porous carbon film with photothermal conversion function using block copolymers includes the following steps:

[0083] S1: Preparation of the uniformly porous membrane: A polystyrene-block-poly(4-vinylpyridine)-block-polyethylene glycol block copolymer with a molecular weight of 750 kg / mol, wherein PS accounts for 90 wt%, was dissolved in a mixed solvent of dimethylformamide and tetrahydrofuran at a concentration of 12.5 wt% to prepare a casting solution. After complete dissolution, the solution was coated onto a clean glass plate using a doctor blade with a thickness of 150 μm. After evaporation for 35 s, the plate was immersed in water for phase inversion to form a membrane. The formed membrane was removed from the coagulation bath and dried to obtain a uniformly porous membrane. The separation layer thickness of the uniformly porous membrane was 150 nm, and the pore size was 5 nm.

[0084] S2: Crosslinking: A reaction solution with a molar ratio of trifluoromethanesulfonic anhydride to dimethylformaldehyde of 10:1 was prepared. The uniformly porous membrane prepared above was immersed in the reaction solution and reacted at 120℃ for 6 hours. After the reaction was completed, the membrane was removed, rinsed three times with an aqueous solution of pH=10, and then dried to obtain a hypercrosslinked uniformly porous membrane. Its surface and cross-sectional structure were characterized by electron microscopy.

[0085] S3: Carbonization: The dried, hypercrosslinked, uniformly porous membrane was placed flat in a quartz boat, covered with a quartz sheet, and then transferred to a tube furnace. Under a nitrogen atmosphere, the temperature was increased to 200°C at a rate of 1°C / min, and carbonized at 200°C for 10 hours. After cooling to room temperature, the membrane was removed to obtain a uniformly porous carbon membrane. The surface and cross-sectional structure of the uniformly porous carbon membrane were characterized by electron microscopy. The morphology of carbon in the uniformly porous carbon membrane was characterized by XRD. Raman spectroscopy was used to characterize the intensity ratio of the D and G band peaks, quantifying the degree of graphitization.

[0086] Photothermal conversion test:

[0087] The prepared uniformly porous carbon membrane was floated on a mixed solvent of heptane and octane through a heat-insulating foam board. After stabilizing for 30 minutes under standard sunlight, the change in the mass of the liquid was recorded over one hour. At the same time, the change in the membrane surface temperature during evaporation was recorded using an infrared thermometer, demonstrating that the uniformly porous carbon membrane has good photothermal conversion capability.

[0088] Example 8

[0089] A method for preparing a uniformly porous carbon film with photothermal conversion function using block copolymers includes the following steps:

[0090] S1: Preparation of uniformly porous membrane: Polyisobutylene-block-polystyrene-block-poly4-vinylpyridine block copolymer with a molecular weight of 300 kg / mol, wherein PS accounts for 85 wt%, is dissolved in a mixed solvent of dimethylformamide and tetrahydrofuran at a concentration of 30 wt% to prepare a casting solution. After complete dissolution, it is coated onto a clean glass plate with a thickness of 150 μm using a doctor blade. After evaporation for 35 s, it is immersed in water for phase inversion to form a membrane. The formed film is removed from the coagulation bath and dried to obtain a uniformly porous membrane.

[0091] S2: Crosslinking: A reaction solution with a molar ratio of trifluoromethanesulfonic acid to dimethylformaldehyde of 7:1 was prepared. The uniformly porous membrane prepared above was immersed in the reaction solution and reacted at 150℃ for 24 h. After the reaction was completed, the membrane was removed, rinsed three times with an aqueous solution of pH=13, and then dried to obtain a hypercrosslinked uniformly porous membrane. Its surface and cross-sectional structure were characterized by electron microscopy.

[0092] S3: Carbonization: The dried, hypercrosslinked, uniformly porous membrane was placed flat in a quartz boat, covered with a quartz sheet, and then transferred to a tube furnace. Under a nitrogen atmosphere, the temperature was increased to 800℃ at a rate of 5℃ / min, and carbonized at 800℃ for 5 hours. After cooling to room temperature, the membrane was removed to obtain a uniformly porous carbon membrane. The surface and cross-sectional structure of the uniformly porous carbon membrane were characterized by electron microscopy. The morphology of carbon in the uniformly porous carbon membrane was characterized by XRD. Raman spectroscopy was used to characterize the intensity ratio of the D and G band peaks, quantifying the degree of graphitization.

[0093] Photothermal conversion test:

[0094] The prepared uniformly porous carbon membrane was floated in a mixed solution of heptane and water through a heat-insulating foam board. After stabilizing for 30 minutes under standard sunlight, the change in the mass of the liquid was recorded over one hour. At the same time, the change in the membrane surface temperature during evaporation was recorded using an infrared thermometer, demonstrating that the uniformly porous carbon membrane has good photothermal conversion capability.

[0095] Example 9

[0096] A method for preparing a uniformly porous carbon film with photothermal conversion function using block copolymers includes the following steps:

[0097] S1: Preparation of uniformly porous membrane: Polyisobutylene-block-polystyrene-block-polyethylene oxide block copolymer with a molecular weight of 200 kg / mol, wherein PS accounts for 70 wt%, is dissolved in a mixed solvent of dimethylformamide and 1,4-dioxane at a concentration of 28 wt% to prepare a casting solution. After complete dissolution, the solution is coated onto a clean glass plate using a doctor blade with a thickness of 150 μm. After evaporation for 35 s, the plate is immersed in water for phase inversion to form a membrane. The formed membrane is removed from the coagulation bath and dried to obtain a uniformly porous membrane.

[0098] S2: Crosslinking: A reaction solution with a molar ratio of trifluoromethanesulfonic acid to dimethylformaldehyde of 10:1 was prepared. The uniformly porous membrane prepared above was immersed in the reaction solution and reacted at 150℃ for 24 h. After the reaction was completed, the membrane was removed, rinsed three times with an aqueous solution of pH=11, and then dried to obtain a hypercrosslinked uniformly porous membrane. Its surface and cross-sectional structure were characterized by electron microscopy.

[0099] S3: Carbonization: The dried, hypercrosslinked, uniformly porous membrane was placed flat in a quartz boat, covered with a quartz sheet, and then transferred to a tube furnace. Under a nitrogen atmosphere, the temperature was increased to 1300℃ at a rate of 10℃ / min, and carbonized at 1300℃ for 10 min. After cooling to room temperature, the membrane was removed to obtain a uniformly porous carbon membrane. The surface and cross-sectional structure of the uniformly porous carbon membrane were characterized by electron microscopy. The morphology of carbon in the uniformly porous carbon membrane was characterized by XRD. Raman spectroscopy was used to characterize the intensity ratio of the D and G band peaks, quantifying the degree of graphitization.

[0100] Photothermal conversion test:

[0101] The prepared uniformly porous carbon membrane was floated in a mixture of crude oil and water emulsion through a heat-insulating foam board. After stabilizing for 30 minutes under standard sunlight, the change in the mass of the liquid was recorded over one hour. At the same time, the change in the membrane surface temperature during the evaporation process was recorded using an infrared thermometer, demonstrating that the uniformly porous carbon membrane has good photothermal conversion capability.

[0102] It will be understood by those skilled in the art that the above descriptions are merely preferred examples of the invention and are not intended to limit the invention. Although the invention has been described in detail with reference to the foregoing examples, those skilled in the art can still modify the technical solutions described in the foregoing examples or make equivalent substitutions for some of the technical features. All modifications and equivalent substitutions made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A method for preparing a uniformly porous carbon film with photothermal conversion function using block copolymers, characterized in that, Includes the following steps: S1: A concentrated solution of the block copolymer is coated onto a film, evaporated in air for 5-35 seconds, then immersed in water and dried to obtain a uniformly porous membrane; the block copolymer is selected from any one of polystyrene-block-polyacrylic acid, polystyrene-block-poly4-vinylpyridine, polyisobutylene-block-polystyrene-block-poly4-vinylpyridine, and polystyrene-block-poly4-vinylpyridine-block-polyethylene glycol; S2: Prepare a reaction solution by mixing a fluorine-containing super strong liquid acid and a crosslinking agent in a molar ratio of 1:1 to 10:

1. Immerse the uniformly porous membrane in the reaction solution. After the reaction is complete, remove the membrane, wash it with an aqueous solution of pH=10-13, and dry it to obtain a super-crosslinked uniformly porous membrane. In S2, the fluorine-containing super liquid acid is selected from any one of trifluoromethanesulfonic acid, trifluoromethanesulfonic anhydride, and bis(trifluoromethanesulfonamide), and the crosslinking agent is selected from dimethylformaldehyde or diethanolformaldehyde. S3: The dried hypercrosslinked uniformly porous membrane is transferred to a tube furnace and calcined at high temperature in an inert atmosphere to carbonize it. After cooling to room temperature, it is taken out to obtain a uniformly porous carbon membrane.

2. The method for preparing a uniformly porous carbon film with photothermal conversion function using block copolymers according to claim 1, characterized in that, The block copolymer has a molecular weight range of 80 to 750 kg / mol, and the polystyrene content in the block copolymer ranges from 70 to 90 wt%.

3. The method for preparing a uniformly porous carbon film with photothermal conversion function using block copolymers according to claim 1, characterized in that, The concentration range of the concentrated solution of the block copolymer is 12.5~30 wt%.

4. The method for preparing a uniformly porous carbon film with photothermal conversion function using block copolymers according to claim 1, characterized in that, In step S1, the thickness of the uniformly porous layer of the prepared uniformly porous membrane ranges from 20 to 300 nm, and the pore size ranges from 5 to 100 nm.

5. The method for preparing a uniformly porous carbon film with photothermal conversion function using block copolymers according to claim 1, characterized in that, In S2, the reaction temperature range is 90-150℃, and the reaction time range is 6-24 hours.

6. The method for preparing a uniformly porous carbon film with photothermal conversion function using block copolymers according to claim 1, characterized in that, In S3, the temperature range of the isothermal carbonization treatment is 200-1300℃, the heating rate from room temperature to the carbonization temperature ranges from 1-10℃ / min, and the isothermal carbonization time ranges from 0.5-10 hours.

7. A uniformly porous carbon membrane with photothermal conversion function, characterized in that, The carbon membrane with photothermal conversion function is prepared by the method of block copolymer preparation according to any one of claims 1-6.

8. The uniformly porous carbon membrane with photothermal conversion function according to claim 7, characterized in that, The pore size of the uniformly porous carbon film changes by less than 15% compared to that before carbonization.

9. The uniformly porous carbon membrane with photothermal conversion function according to claim 7, characterized in that, The uniformly porous carbon film exhibits a Raman spectrum with a peak intensity ratio of not less than 0.5 for the D and G bands; under standard solar radiation, the photothermal conversion efficiency of the uniformly porous carbon film is greater than 0.33.

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