Preparation method and application of bamboo cellulose nanocrystalline composite photocatalyst
By constructing a spiral three-dimensional network structure of bamboo cellulose nanocrystals and ZIF-8, the problems of high cost, low visible light response and insufficient stability of bio-based photocatalysts were solved, and efficient photocatalytic reduction of carbon dioxide was achieved.
Patent Information
- Application Number
- CN202510561893.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-30
- Publication Date
- 2025-09-23
AI Technical Summary
Existing bio-based photocatalysts have problems such as high production cost, low visible light response intensity and insufficient long-term stability.
By combining the hydroxyl groups on the surface of cellulose nanocrystals with the molecular-level anchoring interface of ZIF-8, a spirally arranged three-dimensional network structure is formed. Ultrasonic treatment and freeze-drying processes are used to construct a composite material with a chiral stress field, thereby achieving improved electron transmission efficiency and photogenerated carrier separation.
The visible light response efficiency is significantly improved, the efficiency of photocatalytic reduction of carbon dioxide is enhanced, the production cost is reduced, and the structural stability of the material is maintained.
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Figure CN120679602A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of photocatalytic materials, and in particular to a preparation method and application of a visible light responsive bamboo cellulose nanocrystal composite material photocatalyst. Background Art
[0002] Since the commercialization of titanium dioxide (TiO2) photocatalytic materials in the 1990s, photocatalysts based on inorganic semiconductors have dominated the fields of environmental pollution control (such as organic pollutant degradation) and energy conversion (such as photocatalytic water splitting to produce hydrogen), achieving remarkable results in industrial wastewater treatment, air purification, and clean energy generation. However, traditional photocatalytic materials (such as TiO2, ZnO, and CdS) face three key bottlenecks: First, a limited spectral response range. Most semiconductors, due to their large band gaps (e.g., 3.2 eV for TiO2), can only utilize ultraviolet light, which accounts for 4% of the solar spectrum, and have low absorption efficiency for the 43% of visible light, limiting their practical applications. Second, resource and cost issues are prominent. Precious metal co-catalysts (such as Pt and Au) drive up costs, and some materials (such as CdS) contain heavy metals, posing environmental toxicity risks. Third, insufficient stability, high recombination rates of photogenerated carriers, and the susceptibility of active components (such as Ag3PO4) to photocorrosion, lead to reduced cycle life.
[0003] In recent years, bio-based materials have become a research hotspot due to their renewability, low cost and environmental friendliness. Among them, bamboo nanofibrillated cellulose (BNFC) stands out due to its unique advantages: bamboo has a short growth cycle and is widely distributed around the world, which allows for large-scale extraction of nanocellulose, avoiding dependence on scarce resources; its high specific surface area and porous structure (>200 m 2 / g) provides dense loading sites for photoactive components, inhibiting the agglomeration of nanoparticles. At the same time, the rich surface functional groups (such as hydroxyl and carboxyl groups) facilitate chemical bonding with semiconductor materials (such as metal-organic framework materials, oxide nanoparticles, g-C3N4, etc.) to form a stable interface, thereby improving the charge transfer efficiency. In addition, its excellent mechanical strength (elastic modulus > 100 GPa) and green degradability give it both structural stability and sustainable development potential.
[0004] However, at present, some of the bio-based photocatalysts prepared in the existing technology require the use of precious metals, which has a high production cost; the light response intensity of some bio-based photocatalysts is still low, and the utilization rate of visible light is low. At the same time, the long-term stability of the catalyst is also insufficient and needs further improvement. Summary of the Invention
[0005] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the above background technology and provide a preparation method and application of a visible light responsive bamboo cellulose nanocrystal composite material photocatalyst.
[0006] The present invention utilizes the hydrophobic interaction between the hydroxyl groups on the surface of cellulose nanocrystals and the benzene rings to form a molecular anchoring interface. The cavitation effect generated by ultrasonic treatment induces the directional deposition of ZIF-8 on the surface of the nanocrystals. 2+ It forms a bidentate coordination structure with cellulose hydroxyl groups; ice crystal growth during freeze-drying induces a helical arrangement of cellulose nanocrystals, which molecular dynamics simulations confirm generates a chiral stress field. When ZIF-8 crystallizes in a confined space, its metal nodes are subjected to chiral stress, forming an asymmetric coordination environment. In the composite, the cellulose nanocrystals act as electron transport bridges, and their surface hydroxyl arrays form a proton gradient that accelerates the separation of photogenerated carriers. The electron-deficient zinc nodes of ZIF-8 and the electron-rich regions of cellulose create a built-in electric field, and the cellulose nanocrystals are embedded in the ZIF-8 lattice to form an interpenetrating network. This structure disperses local stress into the three-dimensional framework, and the interfacial hydrogen bond network maintains dynamic equilibrium during the photocatalytic cycle.
[0007] In order to solve the above technical problems, the technical solution proposed by the present invention is: A method for preparing a bamboo cellulose nanocrystal composite material photocatalyst comprises the following steps: (1) Bamboo powder is pre-treated by dewaxing, and then lignin and hemicellulose are removed by acid and alkali to obtain crude bamboo cellulose; (2) hydrolyzing the crude bamboo cellulose; (3) ultrasonically dispersing, purifying, and freeze-drying the hydrolyzed product after step (2) to obtain bamboo cellulose nanocrystals; (4) The bamboo cellulose nanocrystals and the metal organic framework ZIF-8 material are mixed and homogenized, and freeze-dried to obtain a bamboo cellulose nanocrystal composite material photocatalyst, wherein the metal organic framework ZIF-8 material is obtained by adding a 2-methylimidazole solution and a hexadecyltrimethylammonium bromide solution to a solution containing a zinc source and stirring and aging. The nitrogen atom of 2-methylimidazole reacts with Zn 2+ The coordination effect of α-D-H-pyrrolidone forms the ZIF-8 framework, hexadecyltrimethylammonium bromide (CTAB) acts as a structure-directing agent to regulate pore development, and the aging process promotes the formation of crystal defect sites.
[0008] In the above preparation method, preferably, in step (4), the mass ratio of the bamboo cellulose nanocrystals to the metal organic framework ZIF-8 material is 3:7~7:3; and the bamboo cellulose nanocrystals include at least one of bamboo microcrystalline cellulose (MC), bamboo cellulose nanocrystals (CNC), and bamboo cellulose nanofibrils (CNF).
[0009] In the above preparation method, preferably, in step (4), the zinc source includes at least one of zinc nitrate, zinc acetate or zinc chloride; The molar ratio of the zinc source to 2-methylimidazole is 1:6 to 1:8, and the amount of hexadecyltrimethylammonium bromide added is 5% to 15% of the molar amount of zinc ions in the zinc source.
[0010] In the above preparation method, preferably, in step (4), the aging temperature is 25 to 35°C, and the aging time is 12 to 24 hours.
[0011] In the above preparation method, preferably, in step (4), the mixing and homogenization is carried out in a high shear mixer at a rotation speed of 15,000 to 25,000 rpm and a processing time of 5 to 8 min; the freeze-drying includes pre-freezing at a temperature of -50 to -40°C for 4 to 5 hours, and then freeze-drying at -20 to -10°C and a pressure of 10 to 30 Pa for 24 to 36 hours.
[0012] In the above preparation method, preferably, in step (4), the solvent in the solution containing the zinc source is at least one of methanol, ethanol or N,N-dimethylformamide, In the above preparation method, preferably, in step (3), the ultrasonic dispersion is performed using a probe ultrasonic instrument with a power density of 300 to 500 W / cm² and a processing time of 10 to 15 min; the purification is performed using centrifugal purification with a centrifugal purification speed of 12,000 to 15,000 rpm.
[0013] In the above preparation method, preferably, in step (2), the hydrolysis is carried out using a sulfuric acid solution with a concentration of 60% to 64%, the hydrolysis temperature is 45 to 50°C, and the hydrolysis time is 30 to 60 min.
[0014] In the above preparation method, preferably, in step (1), the dewaxing pretreatment is performed using a benzene-ethanol mixed solution, the volume ratio of benzene to ethanol in the benzene-ethanol mixed solution is 2:1 to 4:1, and the dewaxing pretreatment is performed in a Soxhlet extractor under reflux treatment, the reflux temperature is 80 to 110°C, and the reflux time is 6 to 8 hours.
[0015] In the above-mentioned preparation method, preferably, in step (1), the use of acid and alkali to remove lignin and hemicellulose includes using a sodium hydroxide solution with a mass fraction of 8% to 12% in an oil bath at 80 to 95°C for 10 to 12 hours, and using a NaClO2 solution with a mass fraction of 3% to 5%, adjusting the pH to 4 to 6 with glacial acetic acid, and then treating it in an oil bath at 80 to 95°C for 4 to 6 hours.
[0016] In the above preparation method, preferably, in step (1), the particle size of the bamboo powder is 40 to 60 mesh.
[0017] Based on a general inventive concept, the present invention also provides an application of a bamboo cellulose nanocrystal composite material photocatalyst prepared by the above-mentioned preparation method in carbon dioxide reduction and degradation of organic pollutants in water.
[0018] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention utilizes the strong hydrophobicity of benzene to effectively dissolve the wax layer on the surface of bamboo, and ethanol as a polar solvent assists in penetrating the cell wall structure. The use of a benzene-ethanol mixed solution to pretreat bamboo powder can significantly improve the separation efficiency of subsequent components; then, a strong alkaline solution is used to break the phenolic ether bond of lignin through saponification reaction, and the β-1,4-glycosidic bond of hemicellulose is hydrolyzed under acidic conditions. The two can synergistically achieve the purification and separation of bamboo cellulose to obtain crude bamboo cellulose; then, the crude bamboo cellulose is hydrolyzed, and the protonation of concentrated sulfuric acid during the hydrolysis process destroys the amorphous region of cellulose. The microjets generated by the ultrasonic cavitation effect separate the cellulose microfibrils, and finally form bamboo cellulose nanocrystals with a high aspect ratio; the abundant hydroxyl groups on the surface of the bamboo cellulose nanocrystals form coordination bonds with the metal nodes of ZIF-8, and the fluid shear force generated by high shear homogenization is combined to achieve nanoscale dispersion. The template effect of ice crystals during freeze-drying constructs a three-dimensional porous structure, and finally forms a bamboo cellulose nanocrystal composite material photocatalyst with visible light response.
[0019] (2) The present invention combines cellulose nanocrystals with ZIF-8 to construct a three-dimensional network material with a special helical structure (topological chirality). This structure significantly improves the efficiency of photocatalytic reduction of carbon dioxide (CO2) and can: ① Improve electron transfer: Cellulose nanocrystals act as a bridge to help ZIF-8 transfer photogenerated electrons faster, reduce the recombination of electrons and holes, and improve reaction activity; ② Promote CO2 adsorption: The optical rotation (α) of the material is as high as +21.290, indicating that it has a significant chiral helical structure, combined with a high specific surface area (226.25~733.56 m 2 / g), providing abundant active sites and a larger contact area, significantly enhancing the adsorption capacity of CO2 on the material surface; ③ High-efficiency photocatalysis: Without the addition of additional catalysts, the CO generation efficiency of CNCs@ZIF-8 is 9.43 times that of pure ZIF-8, and the more obvious the helical structure (the higher the optical rotation), the higher the efficiency; ④ Enhanced photosensitivity: The special three-dimensional structure makes the material more polarized to light, especially improving the response to ultraviolet light, further optimizing the catalytic effect.
[0020] (3) The preparation process of the present invention is simple and easy to mass-produce. The use of cheap bamboo material enables the batch preparation of visible light-responsive materials, which effectively reduces the production cost of the materials compared with the traditional precious metal photocatalysts. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.
[0022] Figure 1 This is a SEM image of the bamboo cellulose nanocrystal composite material catalyst prepared in Example 1 of the present invention. DETAILED DESCRIPTION
[0023] To facilitate understanding of the present invention, the present invention will be described in more comprehensive and detailed form below in conjunction with the accompanying drawings and preferred embodiments. However, the protection scope of the present invention is not limited to the following specific embodiments.
[0024] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.
[0025] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.
[0026] Performance of the photocatalysts involved in the following examples: The prepared materials were analyzed for data using an automatic polarimeter and a fully automatic specific surface area and porosity analyzer to measure the optical rotation and specific surface area; a CO2 photocatalytic reduction test was conducted in a Labsolar-6A photocatalytic system: 100 mg of the prepared sample was first dispersed in 10 mL of water, a 500 mL closed gas system was vacuum-treated, and then high-purity CO2 was gradually introduced into the system under 0.08 MPa conditions. A 300W xenon lamp was used as the light source, and samples were taken every 1 hour for a total irradiation time of 6 hours. The temperature was maintained at around 25°C throughout the reaction process. The amount of CO produced was measured using a gas chromatograph, and the yield was calculated.
[0027] Example 1: A method for preparing a bamboo cellulose nanocrystal composite material photocatalyst of the present invention comprises the following steps: (1) Cut the bamboo into sections, grind them and pass them through a 60-mesh sieve to obtain bamboo powder.
[0028] (2) Take 100 g of bamboo powder and place it in a Soxhlet extractor. Add a benzene-ethanol mixed solution (200 mL of benzene and 100 mL of ethanol) and reflux at 85 °C for 6 hours. After filtration, vacuum dry for 12 hours to obtain dewaxed bamboo powder.
[0029] (3) Dewaxed bamboo powder was mixed with 8% by mass NaOH solution at a solid-liquid ratio of 1 g:50 mL, stirred and reacted in an oil bath at 85 °C for 12 h, filtered and washed with deionized water until neutral; then 50 mL of 3% by mass NaClO2 solution (adjusted to pH = 4.5 with glacial acetic acid) was added, and the mixture was continued to react at 85 °C for 4 h, filtered and washed until neutral, and dried to obtain crude bamboo cellulose.
[0030] (4) 10 g of crude bamboo cellulose was mixed with 64% sulfuric acid solution at a ratio of 1 g:15 mL. The mixture was hydrolyzed at 50 °C for 45 min, and then centrifuged (12,000 rpm, 15 min). The precipitate was collected and washed with deionized water until the solution became neutral. The neutralized cellulose nanocrystal suspension was treated with a probe ultrasonicator (power density 500 W / cm², frequency 20 kHz) for 15 min, centrifuged again for purification, and freeze-dried to obtain bamboo cellulose nanocrystals (CNCs).
[0031] (5) 2-Methylimidazole (6 mmol) and hexadecyltrimethylammonium bromide (CTAB, 0.05 mmol) were dissolved in 40 mL of methanol, and a methanol solution containing zinc acetate dihydrate (1 mmol) was slowly added. After stirring at room temperature for 30 min, the mixture was transferred to a polytetrafluoroethylene reactor, aged at 35 °C for 24 h, and centrifuged to obtain the metal-organic framework ZIF-8 material.
[0032] (6) The metal organic framework ZIF-8 material and bamboo cellulose nanocrystals (CNC) were dispersed in deionized water at a mass ratio of 7:3, treated with a high shear homogenizer (speed 20,000 rpm) for 8 min, then pre-frozen at -50 °C for 4 h, and transferred to a freeze dryer (pressure 20 Pa, sublimation temperature -15 °C) for freeze drying for 24 h to obtain a bamboo cellulose nanocrystal composite material catalyst.
[0033] The SEM image of the bamboo cellulose nanocrystal composite catalyst prepared in this example is as follows: Figure 1 As shown by Figure 1 It can be seen that bamboo cellulose nanocrystals build bridges and weave into a huge CNCs@ZIF-8 3D network by orderly connecting single ZIF-8 crystals.
[0034] According to the test material, the optical rotation is α = +12.224 and 733.56m 2 / g specific surface area, and the yield of CO2 photoreduction to CO within 6 h was 136.37 μmol·g ‒ 1 .
[0035] Example 2: A method for preparing a bamboo cellulose nanocrystal composite material photocatalyst of the present invention comprises the following steps: (1) Cut the bamboo into sections, grind them and pass them through a 60-mesh sieve to obtain bamboo powder.
[0036] (2) Take 100 g of bamboo powder and place it in a Soxhlet extractor. Add a benzene-ethanol mixed solution (200 mL of benzene and 100 mL of ethanol) and reflux at 85 °C for 6 hours. After filtration, vacuum dry for 12 hours to obtain dewaxed bamboo powder.
[0037] (3) Dewaxed bamboo powder was mixed with 8% by mass NaOH solution at a solid-liquid ratio of 1 g:50 mL, stirred and reacted in an oil bath at 85 °C for 12 h, filtered and washed with deionized water until neutral; then 50 mL of 3% by mass NaClO2 solution (adjusted to pH = 4.5 with glacial acetic acid) was added, and the mixture was continued to react at 85 °C for 4 h, filtered and washed until neutral, and dried to obtain crude bamboo cellulose.
[0038] (4) 10 g of crude bamboo cellulose was mixed with 64% sulfuric acid solution at a ratio of 1 g:15 mL. The mixture was hydrolyzed at 50 °C for 45 min, and then centrifuged (12,000 rpm, 15 min). The precipitate was collected and washed with deionized water until the solution became neutral. The neutralized cellulose nanocrystal suspension was treated with a probe ultrasonicator (power density 500 W / cm², frequency 20 kHz) for 15 min, centrifuged again for purification, and freeze-dried to obtain bamboo cellulose nanocrystals (CNCs).
[0039] (5) 2-Methylimidazole (7 mmol) and hexadecyltrimethylammonium bromide (CTAB, 0.1 mmol) were dissolved in 40 mL of methanol, and a methanol solution containing zinc nitrate (1 mmol) was slowly added. After stirring at room temperature for 30 min, the mixture was transferred to a polytetrafluoroethylene reactor, aged at 30 °C for 18 h, and centrifuged to obtain the metal-organic framework ZIF-8 material.
[0040] (6) The metal organic framework ZIF-8 material and bamboo cellulose nanocrystals (CNC) were dispersed in deionized water at a mass ratio of 5:5, treated with a high shear homogenizer (speed 18000 rpm) for 8 min, then pre-frozen at -50 °C for 4 h, and transferred to a freeze dryer (pressure 20 Pa, sublimation temperature -15 °C) for freeze drying for 24 h to obtain a bamboo cellulose nanocrystal composite material catalyst.
[0041] The bamboo cellulose nanocrystal composite catalyst prepared in this embodiment has an optical rotation of α = +15.448 and a wavelength of 427.25 nm according to the test material. 2 / g specific surface area, and the yield of CO2 photoreduction to CO within 6 h was 179.59 μmol·g ‒ 1 .
[0042] Example 3: A method for preparing a bamboo cellulose nanocrystal composite material photocatalyst of the present invention comprises the following steps: (1) Cut the bamboo into sections, grind them and pass them through a 60-mesh sieve to obtain bamboo powder.
[0043] (2) Take 100 g of bamboo powder and place it in a Soxhlet extractor. Add a benzene-ethanol mixed solution (150 mL of benzene and 50 mL of ethanol) and reflux it at 90 °C for 7 hours. After filtration, vacuum dry it for 12 hours to obtain dewaxed bamboo powder.
[0044] (3) Dewaxed bamboo powder was mixed with 10% by mass NaOH solution at a solid-liquid ratio of 1 g:50 mL, stirred and reacted in an 85°C oil bath for 12 h, filtered and washed with deionized water until neutral; then 50 mL of 3% by mass NaClO2 solution (adjusted to pH = 4.5 with glacial acetic acid) was added, and the reaction was continued at 90°C for 5 h. The mixture was filtered and washed until neutral, and dried to obtain crude bamboo cellulose.
[0045] (4) 10 g of crude bamboo cellulose was mixed with 64% sulfuric acid solution at a ratio of 1 g:15 mL. The mixture was hydrolyzed at 50 °C for 45 min, and then centrifuged (12,000 rpm, 15 min). The precipitate was collected and washed with deionized water until the solution became neutral. The neutralized cellulose nanocrystal suspension was treated with a probe ultrasonicator (power density 500 W / cm², frequency 20 kHz) for 15 min, centrifuged again for purification, and freeze-dried to obtain bamboo cellulose nanocrystals (CNCs).
[0046] (5) 2-Methylimidazole (6 mmol) and hexadecyltrimethylammonium bromide (CTAB, 0.05 mmol) were dissolved in 40 mL of methanol, and a methanol solution containing zinc acetate dihydrate (1 mmol) was slowly added. After stirring at room temperature for 30 min, the mixture was transferred to a polytetrafluoroethylene reactor, aged at 35 °C for 24 h, and centrifuged to obtain the metal-organic framework ZIF-8 material.
[0047] (6) The metal organic framework ZIF-8 material and bamboo cellulose nanocrystals (CNC) were dispersed in deionized water at a mass ratio of 3:7, treated with a high shear homogenizer (speed 20,000 rpm) for 8 min, then pre-frozen at -45 °C for 5 h, and transferred to a freeze dryer (pressure 20 Pa, sublimation temperature -15 °C) for freeze drying for 30 h to obtain a bamboo cellulose nanocrystal composite material catalyst.
[0048] The bamboo cellulose nanocrystal composite catalyst prepared in this embodiment has an optical rotation of +21.290 and a 2 / g specific surface area, and the yield of CO2 photoreduction to CO within 6 h was 301.16 μmol·g ‒ 1 .
[0049] Comparative Example 1: The catalyst of this comparative example is prepared as follows: (1) 2-Methylimidazole (6 mmol) and hexadecyltrimethylammonium bromide (CTAB, 0.05 mmol) were dissolved in 40 mL of methanol, and a methanol solution containing zinc acetate dihydrate (1 mmol) was slowly added. After stirring at room temperature for 30 min, the mixture was transferred to a polytetrafluoroethylene reactor, aged at 35 °C for 24 h, and centrifuged to obtain the metal-organic framework ZIF-8 material.
[0050] (2) Then, the product was pre-frozen at -50 °C for 4 h and transferred to a freeze dryer (pressure 20 Pa, sublimation temperature -15 °C) for freeze-drying for 24 h to obtain pure ZIF-8 material.
[0051] The pure metal organic framework ZIF-8 material prepared in this comparative example has an optical rotation of +0.000 and a molecular weight of 1084.27m 2 / g specific surface area, and the yield of CO2 photoreduction to CO within 6 h was 31.94 μmol·g ‒ 1 .
[0052] Comparative Example 2: The catalyst of this comparative example is prepared as follows: (1) preparing bamboo cellulose nanocrystals (CNC) according to steps (1) to (4) of Example 1; (2) The metal organic framework material ZIF-67 and bamboo cellulose nanocrystals (CNC) were dispersed in deionized water at a mass ratio of 7:3, treated with a high shear homogenizer (speed 20,000 rpm) for 8 min, then pre-frozen at -50 °C for 4 h, and transferred to a freeze dryer (pressure 20 Pa, sublimation temperature -15 °C) for freeze-drying for 24 h to obtain the bamboo cellulose nanocrystal composite material catalyst CNC@ZIF-67.
[0053] Experimental testing revealed that CNC@ZIF-67 exhibits an optical rotation of +5.340, a specific surface area of 485.72 m² / g, and a CO photoreduction yield of 97.08 μmol·g⁻¹ (yield of 16.17 μmol·g⁻¹·h⁻¹) in 6 hours for CO₂ photoreduction. Compared to the yield and optical rotation of CNC@ZIF-8 in Example 1, the catalytic performance of the ZIF-67 composite system is significantly reduced, demonstrating the unique advantages of the coordination environment and pore structure of ZIF-8 in synergy with CNC.
[0054] As shown in Table 1, the optical rotations of the bamboo cellulose nanocrystal composite photocatalysts prepared in the above examples were α = +12.224, +15.448, and +21.290, respectively, and their specific surface areas ranged from 226.25 to 733.56 m² / g. The CNCs@ZIF-8 photocatalyst exhibited significantly better CO2 evolution activity than pure ZIF-8 (α = 0.000). The CNCs@ZIF-8 (α = +21.290) in Example 3 photoreduced CO2 to CO at a yield of 301.16 μmol·g within 6 hours. -1 , which is 9.43 times that of pure ZIF-8 (α = 0.000) (31.94 μmol·g ‒1 ), and the yield of CNCs@ZIF-8 (α = +21.290) was 50.19 μmol·g -1 ·h -1 .
[0055] The bamboo cellulose nanocrystal composite material photocatalyst material prepared in the above embodiments was subjected to a cycle test. The results showed that after five cycles, the CO yield was still high, indicating that it still maintained good catalytic activity.
[0056] Table 1 Photocatalyst effect data of implementation cases
Claims
1. A method for preparing a bamboo cellulose nanocrystal composite material photocatalyst, characterized in that: The following steps are involved: (1) Bamboo powder is pre-treated by dewaxing, and then lignin and hemicellulose are removed by acid and alkali to obtain crude bamboo cellulose; (2) hydrolyzing the crude bamboo cellulose; (3) ultrasonically dispersing, purifying, and freeze-drying the hydrolyzed product after step (2) to obtain bamboo cellulose nanocrystals; (4) The bamboo cellulose nanocrystals and the metal organic framework ZIF-8 material are mixed and homogenized, and freeze-dried to obtain a bamboo cellulose nanocrystal composite material photocatalyst, wherein the metal organic framework ZIF-8 material is obtained by adding 2-methylimidazole solution and hexadecyltrimethylammonium bromide solution to a solution containing a zinc source and stirring and aging.
2. The preparation method according to claim 1, wherein In step (4), the mass ratio of the bamboo cellulose nanocrystals to the metal organic framework ZIF-8 material is 3:7 to 7:
3.
3. The preparation method according to claim 1, wherein In step (4), the zinc source includes at least one of zinc nitrate, zinc acetate or zinc chloride; The molar ratio of the zinc source to 2-methylimidazole is 1:6 to 1:8, and the amount of hexadecyltrimethylammonium bromide added is 5% to 15% of the molar amount of zinc ions in the zinc source.
4. The preparation method according to claim 1, wherein In step (4), the aging temperature is 25 to 35°C, and the aging time is 12 to 24 hours.
5. The preparation method according to claim 1, wherein In step (4), the mixing and homogenization is carried out in a high shear mixer at a rotation speed of 15,000 to 25,000 rpm and a processing time of 5 to 8 minutes; the freeze-drying includes pre-freezing at a temperature of -50 to -40°C for 4 to 5 hours, and then freeze-drying at -20 to -10°C and a pressure of 10 to 30 Pa for 24 to 36 hours.
6. The preparation method according to claim 1, wherein In step (3), the ultrasonic dispersion is performed using a probe ultrasonic instrument with a power density of 300 to 500 W / cm² and a processing time of 10 to 15 min; the purification is performed using centrifugal purification with a centrifugal purification speed of 12,000 to 15,000 rpm.
7. The preparation method according to claim 1, wherein In step (2), the hydrolysis is carried out using a sulfuric acid solution with a concentration of 60% to 64%, a hydrolysis temperature of 45 to 50°C, and a hydrolysis time of 30 to 60 min.
8. The preparation method according to claim 1, wherein In step (1), the dewaxing pretreatment is performed using a benzene-ethanol mixed solution, the volume ratio of benzene to ethanol in the benzene-ethanol mixed solution is 2:1 to 4:1, and the dewaxing pretreatment is performed in a Soxhlet extractor under reflux treatment at a reflux temperature of 80 to 110°C and a reflux time of 6 to 8 hours.
9. The preparation method according to claim 1, wherein In step (1), the acid-base removal of lignin and hemicellulose includes using a sodium hydroxide solution with a mass fraction of 8% to 12% in an oil bath at 80 to 95°C for 10 to 12 hours, and using a NaClO2 solution with a mass fraction of 3% to 5%, adjusting the pH to 4 to 6 with glacial acetic acid, and then treating in an oil bath at 80 to 95°C for 4 to 6 hours.
10. Use of the bamboo cellulose nanocrystal composite material photocatalyst prepared by the preparation method according to any one of claims 1 to 9 in photocatalytic carbon dioxide reduction and organic pollutant degradation.