Method for loading metal nanoparticles based on cellulose nanosheets

Abstract

The invention belongs to the technical field of nano materials and functional composite materials, and relates to a method for loading metal nanoparticles based on cellulose nanosheets. Cellulose reacts with a zwitterionic catalyst containing an acidic group and a basic group at the same time to obtain the two-dimensional cellulose nanosheet which is more uniform in thickness, more controllable in size and more complete in crystal form, and the two-dimensional cellulose nanosheet has better dispersity and functionalization potential; and then the cellulose nanosheets and a metal precursor are subjected to the complexing action between surface functional groups and metal ions / metal precursors, the processes of uniform loading, controllable reduction, stable anchoring and the like are achieved, and the nanometal and cellulose nanosheet composite material which is stable in structure and good in dispersity is formed. The composite material has the advantages of being high in structural stability, good in metal dispersity, high in catalytic activity and the like, and is suitable for the fields of electro-catalysis, thermocatalysis, environment purification, energy conversion and the like.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials and functional composite materials technology, and relates to a method for loading metal nanoparticles based on cellulose nanosheets. Background Technology

[0002] With the rapid development of nanomaterials and green sustainable development technologies, metal nanoparticles, due to their excellent catalytic, electrochemical, and optical properties, are widely used in energy conversion, environmental remediation, and functional materials. To improve their stability and activity, they need to be loaded onto highly dispersible, high-surface-area support materials. Currently, commonly used two-dimensional supports include graphene oxide, MoS2, and layered double hydroxides (LDHs), but these materials often lack natural active sites and require cumbersome chemical modification to achieve uniform metal anchoring, and their dispersibility and scalability are limited.

[0003] Cellulose nanosheets (CNS), as an abundant, renewable, and environmentally friendly natural polymer material, have attracted widespread attention in recent years. This material exhibits high dispersibility and film-forming properties, and its surface is naturally rich in polar functional groups such as hydroxyl (-OH) groups. Theoretically, it can serve as a metal carrier, enabling the loading of metal nanoparticles with controllable particle size and uniform dispersion. Currently, common methods for extracting cellulose nanosheets include acid hydrolysis, TEMPO oxidation, enzymatic hydrolysis, mechanical exfoliation, and selective chemical catalytic fragmentation. Acid hydrolysis requires strong acids and generates large amounts of wastewater pollution; TEMPO oxidation relies on expensive organic reagents and is complex; enzymatic hydrolysis is inefficient and involves high enzyme costs; mechanical exfoliation is energy-intensive and requires high temperature and pressure conditions; and chemical catalytic methods often use non-green catalysts. Current methods struggle to simultaneously meet the industrialization requirements of low cost, environmental friendliness, and process control.

[0004] Therefore, developing a green method to prepare cellulose nanosheets with regular structure and controllable thickness, and then loading them with metal, is of great significance for realizing the practical application of green and sustainable materials in high-end catalysis, energy storage, biomedicine and other fields. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, the present invention aims to provide a method for loading metal nanoparticles onto cellulose nanosheets, thereby overcoming the shortcomings of the prior art. The present invention employs the following technical solutions to achieve its objective:

[0006] One aspect of the present invention provides a method for loading metal nanoparticles onto cellulose nanosheets, comprising the following steps:

[0007] (1) Cellulose was reacted with zwitterionic catalyst in a polar solvent, and then the reactants were mechanically treated in a polar solvent to obtain cellulose nanosheets.

[0008] (2) The cellulose nanosheets are uniformly mixed with the metal precursor and then subjected to reduction treatment to obtain cellulose nanosheets loaded with metal nanoparticles.

[0009] Amphoteric catalysts contain both acidic and basic groups;

[0010] The monomers used to prepare the zwitterionic catalysts are one or more of the following: phenol, hydroquinone, resorcinol, catechol, 1,3,5-trihydroxybenzene, bisphenol A, benzoic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, p-aminophenol, phenylenediamine, p-aminobenzamide, imidazole, pyrrole, benzimidazole, benzenesulfonic acid, 4-mercaptophenol, 1,3,5-benzenetrisulfonic acid, phenylphosphonic acid, aniline, dimethylaniline, pyridine aromatic hydrocarbons, carbazole, triazine, benzidine, 4-aminobenzenesulfonic acid, aminobenzoic acid, imidazolesulfonic acid, carbazole-carboxylic acids, phenylboronic acid, p-aminophenylboronic acid, p-nitrophenylboronic acid, 2-hydroxyphenylboronic acid, naphthaleneboronic acid, anthraquinone, vinylphenylboronic acid, 3,4-ethylenedioxythiophene, indole, pyrrole formaldehyde, pyrrole amino acids, chloropyridine, p-nitrophenol, p-nitroaniline, and 3-hydroxypyridine.

[0011] When preparing a zwitterionic catalyst, if there is only one monomer, the monomer must contain both acidic and basic groups. When there are two or more monomers, it is only necessary to ensure that the system composed of all monomers contains both acidic and basic groups.

[0012] Preferably, the monomers for preparing the zwitterionic catalyst are phenylboronic acid and pyrrole.

[0013] Preferably, the zwitterionic catalyst is a coupling product formed by one or more monomers through a Friedel-Crafts alkylation polymerization reaction.

[0014] Preferably, the preparation method of the zwitterionic catalyst includes the following steps:

[0015] One or more monomers, a Lewis acid catalyst, and an acetal are reacted in a weak / nonpolar solvent, and the mixture is filtered, washed, and dried to obtain a zwitterionic catalyst.

[0016] In the preparation of the above-mentioned zwitterionic catalyst, preferably, the molar ratio of monomer, Lewis acid catalyst, and acetal is 1:1 to 6:1 to 10. The Lewis acid is one or more of FeCl3 (ferric chloride), AlCl3 (aluminum chloride), SnCl4 (tin tetrachloride), BF3·OEt3 (boron difluoride ether complex), ZnCl2 (zinc chloride), TiCl4, SbCl5, GaCl3, InCl3, and Sc(OTf)3. The acetal is one or more of dimethylformaldehyde, diethanolformaldehyde, and acetaldehyde-dimethylformaldehyde. The weak / nonpolar solvent is one or more of dichloroethane, dichloromethane, p-dichlorobenzene, chlorobenzene, CS2 (carbon disulfide), carbon tetrachloride (CCl4), o-dichlorobenzene, m-dichlorobenzene, 1,2,4-trichlorobenzene, o-xylene, p-xylene, nitrobenzene, 1,3,5-tris(bromomethyl)benzene, and 1,4-bis(chloromethyl)benzene. The reaction temperature is 80–120℃, and the reaction time is 10–30 h.

[0017] The cellulose of this invention is one or more of the following: corn cob cellulose, straw cellulose (including rice straw cellulose, wheat straw cellulose, bean straw cellulose, etc.), cotton cellulose, distiller's grains cellulose, wood cellulose, hemp cellulose, bamboo cellulose, bacterial cellulose, viscose fiber, cuprammonium cellulose, acetate cellulose, modal fiber, lyocell fiber, Tencel fiber, nanocellulose, microcrystalline cellulose, cellulose ethers, red algae cellulose, brown algae cellulose, green algae cellulose, blue algae cellulose, Euglena cellulose, Congo red algae cellulose, Nostoc cellulose, Chlamydomonas cellulose, Chlorella cellulose, and Spirulina cellulose. Bacterial cellulose can be derived from species of the genus *Komagataeibacter*, such as *Komagataeibacter xylinus*, *Komagataeibacter hansenii*, *Komagataeibacter rhaeticus*, *Komagataeibacter medellinensis*, and *Komagataeibacter nataicola*; species of the genus *Acetobacter*, such as *Acetobacter xylinum*, *Acetobacter pasteurianus*, and *Acetobacter aceti*; species of the genus *Gluconacetobacter*, such as *Gluconacetobacter entanii*, *Gluconacetobacter xylinus*, and *Gluconacetobacter hansenii*; species of the genus *Sarcina*, such as *Sarcina ventriculi*; species of the genus *Rhizobium*, such as *Rhizobium leguminosarum*; species of the genus *Agrobacterium*, such as *Agrobacterium tumefaciens*; and species of the genus *Achromobacter*, such as *Achromobacter*. Bacterial cellulose produced by strains such as xylosoxidans.

[0018] Before reacting with the zwitterionic catalyst, cellulose undergoes a pretreatment process, which includes any one or both of steps (1) and (2):

[0019] (1) Add cellulose to water and / or alcohol solvents and stir at 70-150℃ for 1-24h to dissolve water-soluble polysaccharides such as agar, alginate, and carrageenan in cellulose;

[0020] (2) Cellulose is treated with one or more of acids, alkalis, and enzymes to reduce crystallinity and remove non-cellulose impurities. Then, the solid is precipitated and washed with water until pH = 7 ± 0.1.

[0021] Optionally, acid treatment is carried out using an aqueous solution of phosphoric acid, with a concentration of 70–90 wt%, at a temperature of 30–70 °C for 1–5 h. Alkali treatment is carried out using an aqueous solution of sodium hydroxide and / or potassium hydroxide, with a concentration of 0.1–5 mol / L, at a temperature of 80–120 °C for 1–24 h.

[0022] In step (1), preferably, the mass ratio of zwitterionic catalyst to cellulose is 0.5–3:1. Preferably, the mass ratio of cellulose to polar solvent is 1:1–500, more preferably 1:2–200, and even more preferably 1:5–100. Preferably, the polar solvent is one or more of water, DMSO, ionic liquid, ethanol, methanol, and isopropanol. Preferably, the reaction temperature is 30–400°C, more preferably 120–400°C, and even more preferably 150–200°C. Preferably, the reaction time is 5 min–10 h, more preferably 5–300 min, and even more preferably 5–200 min. Preferably, the apparatus used for the reaction can be a ball mill, ultrasonic treatment, mechanical crushing, high-pressure reactor, microwave reactor, ultrasonic reactor, electric heating reactor, steam explosion machine, etc.

[0023] In step (1), the reactants are placed in a polar solvent to swell for 1 to 20 hours, then subjected to mechanical treatment by sonication for 10 to 100 minutes, and finally filtered and dried to obtain exfoliated cellulose nanosheets.

[0024] In step (2), preferably, the metal precursor is H2PtCl6·6H2O, platinum acetylacetonate (Pt(acac)2), PdCl2, Pd(acac)2, RuCl3·xH2O, Ru(acac)3, RhCl3·xH2O, Rh(acac)3, HAuCl4·3H2O, AgNO3, Ni(NO3)2·6H2O, Ni(acac)2, NiCl2·6H2O, or Fe(NO3)3·9H2O. , Fe(acac)3, FeCl3·6H2O, Co(NO3)2·6H2O, Co(acac)2, Mn(NO3)2·4H2O, Mn(acac)3, Cu(NO3)2·3H2O, C u(acac)2, Zn(NO3)2·6H2O, Zn(acac)2, Ce(NO3)3·6H2O, Ce(acac)3, Ga(NO3)3, Ga(acac)3, (NH4)6Mo7O 24 ·4H2O, MoO2(acac)2, Na2WO4, WO3, WCl6, phosphotungstic acid H3PW 12 O 40 xH2O, H3PMo12 O 40 ·xH2O、H4SiW 12 O 40 ·xH2O, H4SiMo 12 O 40 ·xH2O、H5[PMo 10 V2O 40 ], H3[PMo 11 RuO 40 ]、(NH4)3PW 12 O 40 (CH3NH3)3PW 12 O 40 Fe3PMo 12 O 40 Cu3PMo 12 O 40 Cs x H 3-x PW 12 O 40 (0 <x≤3)、K3PW 12 O 40 Na3PMo 12 O 40 Cs 2.5 H 0.5 PW 12 O 40 Fe3Mo 12 O 40 LaPMo 12 O 40 Ce3PW 12 O 40 ,PBu4PW 12 O 40 CTA-PW 12 O 40 Cs-NH4-PW 12 O 40 One or more of the following. Metal precursors are anchored, confined, and reduced to metal nanoparticles / quantum dots by functional groups such as -OH on the surface of cellulose nanosheets.

[0025] Preferably, the mixing method of cellulose nanosheets and metal precursors includes one or more of the following: liquid phase mixing, impregnation, gelation, sol-gel, evaporation-induced assembly, spray drying, spray freeze drying, and freeze mixing.

[0026] Further preferred, the mixing method is an impregnation method. Cellulose nanosheets are impregnated in a metal precursor for 10–100 min.

[0027] Preferably, the reduction treatment is one or more of carbonization treatment, hydrothermal treatment, and microwave heating.

[0028] When the reduction treatment is replaced by carbonization, the heating rate is 1–10 °C / min, the carbonization temperature is 250–1500 °C, and the holding time is 1–8 h. The entire process is protected by an inert gas, such as nitrogen or argon. The carbonization process can be performed in stages. First, carbonize at 250–500 °C for 20–200 min, then carbonize at 600–1500 °C for 40 min–5 h.

[0029] When the reduction treatment is hydrothermal treatment, the hydrothermal temperature is 150-300℃ and the hydrothermal treatment time is 2-24h.

[0030] A second aspect of the present invention provides a composite material prepared by the above-described preparation method, the composite material comprising cellulose nanosheets and metal nanoparticles, wherein the metal nanoparticles are loaded on the surface of the cellulose nanosheets.

[0031] Preferably, the cellulose nanosheets have a length of 1–40 μm and a thickness of 2–50 nm.

[0032] Preferably, the average diameter of the metal nanoparticles is 0.5–100 nm, more preferably 0.5–50 nm, and even more preferably 1–10 nm.

[0033] Preferably, the metal loading is 0.1 to 30 wt%, more preferably 0.1 to 10 wt%.

[0034] A third aspect of the present invention provides the application of the composite material in electrocatalysis, conductive frameworks for capacitors or lithium batteries, catalytic degradation of organic pollutants, adsorption of heavy metals or water purification, antibacterial dressings or bioelectronic devices.

[0035] The composite material is prepared into forms such as membrane material, coating, electrode sheet, and powder adsorbent according to application requirements.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] 1. The cellulose nanosheets prepared by this invention are rich in natural hydroxyl groups on their surface, which can strongly bind with metal ions to form stable coordination, promote the in-situ reduction and confined nucleation of metal ions, effectively prevent their aggregation and deactivation, and achieve metal nanoparticle loading with controllable particle size and uniform dispersion. High performance can be achieved under low metal loading conditions. In contrast, carbon materials such as graphene require the introduction of additional functional groups (such as oxide and nitrogen doping) to achieve similar effects.

[0038] 2. The cellulose nanosheets prepared by this invention have good two-dimensional structure and film-forming properties. After carbonization, they can form a porous carbon support with high specific surface area, which improves electron transport performance and catalytic stability.

[0039] 3. The metal-OC bridging structures formed during the heat treatment of cellulose nanosheets with loaded metal enhance the bonding strength between the metal and the support, and maintain structural stability under conditions such as electrocatalysis and high-temperature pyrolysis, thereby improving the thermal stability and catalytic life of the material.

[0040] 4. The cellulose nanosheets prepared by this invention have a very strong binding force with metals, and the types of metals can be flexibly changed (such as W, Ag, Ni, Fe, Ru, Pt, etc.), and even bimetallic synergistic loading can be carried out, giving the composite material excellent electrocatalytic performance, adsorption performance, antibacterial performance, etc., and it is widely applicable to energy storage, catalysis, biomedical fields and other fields.

[0041] 5. This invention uses a zwitterionic catalyst to achieve efficient exfoliation without damaging the cellulose crystal structure, preserving the crystal integrity and excellent physical properties of cellulose, and can obtain two-dimensional cellulose nanosheets with smaller thickness, more uniform size, and better dispersion.

[0042] 6. The composite material of metal nanoparticles supported on cellulose nanosheets prepared by this invention has the advantages of high structural stability, good metal dispersion, and strong catalytic activity. Moreover, cellulose nanosheets are used as carriers, and the source is green and renewable, making them suitable for fields such as electrocatalysis, thermocatalysis, environmental purification, and energy conversion. The entire preparation method is simple and environmentally friendly, providing a green, efficient, and scalable metal loading platform. Attached Figure Description

[0043] Figure 1 The structural formula of the catalyst prepared in Example 1 is shown below;

[0044] Figure 2 SEM image of the bacterial cellulose nanosheets prepared in Example 1;

[0045] Figure 3 TEM image of cellulose nanosheets supported by W nanoparticles;

[0046] Figure 4 TEM images of unsuccessfully loaded cellulose nanosheets and aggregated W metal;

[0047] Figure 5 This is a schematic diagram of the band structure of the W metal in CNS@W of Example 1 and CNS / W of Comparative Example 1, which is confined by cellulose nanosheets.

[0048] Figure 6XPS spectra of W metal in CNS@W of Example 1 and CNS / W of Comparative Example 1 reduced by cellulose nanosheets;

[0049] Figure 7 The performance of W nanoparticles confined and reduced from W cellulose nanosheets in CNS@W of Example 1 and CNS / W of Comparative Example 1 in the hydrogen evolution reaction;

[0050] Figure 8 POM of cellulose nanosheets extracted from various plant celluloses;

[0051] Figure 9 The performance of the CNS@Ni catalyst in the hydrogen evolution reaction of Example 3;

[0052] Figure 10 The performance of the CNS@Pt catalyst in Example 5 is shown in the hydrogen evolution reaction. Detailed Implementation

[0053] In the description of this invention, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, and includes both a and b. "Multiple" includes two, three, four, five, or more.

[0054] The technical solution of the present invention will be further described and illustrated below with reference to specific embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are only for the purpose of helping to understand the present invention and are not intended to limit the specific scope of the present invention. Furthermore, the accompanying drawings used herein are merely for better illustrating the content disclosed in the present invention and do not limit the scope of protection. Unless otherwise specified, the raw materials used in the embodiments of the present invention are all commonly used in the art, and the methods used in the embodiments are all conventional methods in the art.

[0055] Example 1

[0056] The method for loading metal nanoparticles onto cellulose nanosheets in this embodiment includes the following steps:

[0057] (1) 0.08 mol of phenylboronic acid and 0.08 mol of pyrrole were mixed at room temperature (25±℃ in this article, which will not be repeated below) for 4 h. 200 mL of 1,2-dichloroethane, 0.16 mol of FeCl3 catalyst, and 0.32 mol of dimethylformaldehyde were added, and the mixture was stirred at 100℃ for 16 h. The mixture was then vacuum filtered, washed, and dried to obtain the catalyst.

[0058] Figure 1 The structure of the catalyst prepared in Example 1 is shown below; two monomers are linked by methylene bonds in dimethylformaldehyde under catalytic conditions to form a zwitterionic catalyst.

[0059] (2) 10g of bacterial cellulose was added to 100mL of 85% H3PO4 aqueous solution and stirred at 40℃ for 2h. Then it was placed in a refrigerator at 4℃ overnight, while 400mL of anhydrous ethanol was refrigerated in the refrigerator. The refrigerated anhydrous ethanol was poured into the refrigerated cellulose solution and stirred at room temperature for 14h to precipitate solid. The solution was diluted and washed with deionized water multiple times until the pH of the washing solution was 7. The pretreated bacterial cellulose was obtained by filtration. 0.05g of the pretreated bacterial cellulose and 0.05g of the catalyst were placed in 20mL of deionized water and hydrolyzed in a microwave reactor at 190℃ for 10min to obtain cellulose hydrolysate. The cellulose hydrolysate was placed in DMSO and stirred at room temperature for 10h to swell. It was then sonicated at 40KHz for 1h, filtered, washed, and freeze-dried to obtain exfoliated bacterial cellulose nanosheets.

[0060] Figure 2 The images show SEM images of the bacterial cellulose nanosheets prepared in Example 1. The top two images show the cellulose nanosheets that were not peeled apart, and the bottom two images show the peeled cellulose nanosheets.

[0061] (3) The bacterial cellulose nanosheets were immersed in a 0.5 mol / L phosphotungstic acid (HPW) aqueous solution for 60 min with stirring, freeze-dried, placed in a tube furnace, carbonized at 300℃ for 1 h, carbonized at 700℃ for 2 h, with a heating rate of 10℃ / min, to obtain cellulose nanosheets loaded with W nanoparticles (CNS@W).

[0062] Figure 3 The TEM image shows cellulose nanosheets loaded with W nanoparticles, indicating that the W nanoparticles are uniformly dispersed and loaded on the nanosheets.

[0063] The average particle size of the W nanoparticles is 2–5 nm, and the loading is 12 wt%.

[0064] Comparative Example 1

[0065] Steps (1) and (2) of Comparative Example 1 are the same as those of Example 1, and step (3) includes:

[0066] Bacterial cellulose nanosheets were mixed with phosphotungstic acid in a undried manner, placed in a tube furnace, and carbonized at 300℃ for 1 h and 700℃ for 2 h, with a heating rate of 10℃ / min, to obtain agglomerated large-sized W metal sheets (CNS / W).

[0067] Figure 4 TEM images of unsuccessfully loaded cellulose nanosheets and aggregated W metal.

[0068] Figure 5This is a schematic diagram of the band structure of the W metal in CNS@W of Example 1 and CNS / W of Comparative Example 1, confined by cellulose nanosheets. After the W metal nanoparticles are anchored and loaded on the surface of the cellulose nanosheets, compared with the unloaded metal, the band gap is increased, the work function is increased, and the valence band is closer to the Fermi level, exhibiting a quantum confinement effect. This shows that the cellulose nanosheets confine the metal nanoparticles, and the crystal growth is restricted to the nanoscale.

[0069] Figure 6 XPS spectra of the reduction of W metal in CNS@W of Example 1 and CNS / W of Comparative Example 1 by cellulose nanosheets. After the metal nanoparticles are anchored, loaded, and confined to the surface of the cellulose nanosheets for nucleation, W changes from an oxidized state to a non-oxidized state. 6+ Restore to generate W 4 + The decrease in CO bonds and the increase in C=O bonds in cellulose indicate the reduction of surface hydroxyl groups.

[0070] Figure 7 The performance of W nanoparticles reduced from W cellulose nanosheets in the CNS@W of Example 1 and the CNS / W of Comparative Example 1 in the hydrogen evolution reaction is shown. Compared with unreduced W metal and cellulose nanosheets, the W nanoparticles on the surface of cellulose nanosheets exhibit a smaller overpotential and a smaller Tafel slope in the hydrogen evolution reaction, indicating enhanced catalytic performance.

[0071] Example 2

[0072] (1) Mix 0.08 mol benzoic acid and 0.08 mol carbazole at room temperature for 5 h. Add 250 mL of 1,2-dichloroethane, 0.16 mol FeCl3 catalyst, and 0.32 mol dimethylformaldehyde, and stir at 100 °C for 15 h. Vacuum filter, wash, and dry to obtain the catalyst.

[0073] (2) 10g of wood pulp cellulose was added to 100mL of 85% H3PO4 aqueous solution and stirred at 45℃ for 3h. Then, it was refrigerated overnight at 4℃, while simultaneously refrigerating 500mL of anhydrous ethanol in the refrigerator. The refrigerated anhydrous ethanol was poured into the refrigerated cellulose solution and stirred at room temperature for 12h to precipitate a solid. The solution was repeatedly diluted and washed with deionized water until the pH of the washing solution was 7. The pretreated bacterial cellulose was then filtered. 0.1g of the pretreated wood pulp cellulose and 0.1g of the catalyst were placed in 50mL of deionized water and hydrolyzed at 180℃ for 15min in a microwave reactor to obtain cellulose hydrolysate. The cellulose hydrolysate was then placed in DMSO and stirred at room temperature for 8h to swell, followed by sonication at 40kHz for 1h. The solution was filtered, washed, and freeze-dried to obtain exfoliated wood pulp cellulose nanosheets. The POM of the cellulose nanosheets extracted from wood pulp cellulose is shown in [reference needed]. Figure 8 .

[0074] (3) Immerse the wood pulp cellulose nanosheets in a 0.5 mol / L AgNO3 aqueous solution for 70 min with stirring, freeze dry, place in a tube furnace, carbonize at 750℃ for 2 h with a heating rate of 10℃ / min to obtain Ag nanoparticle-loaded cellulose nanosheets.

[0075] Example 3

[0076] (1) Mix 0.08 mol benzenesulfonic acid and 0.08 mol benzimidazole by stirring at room temperature for 6 h. Add 300 mL of 1,2-dichloroethane, 0.16 mol FeCl3 catalyst, and 0.32 mol dimethylformaldehyde, and stir at 90 °C for 20 h. Vacuum filter, wash, and dry to obtain the catalyst.

[0077] (2) 10g of cotton cellulose was added to 100mL of 85% H3PO4 aqueous solution and stirred at 50℃ for 3h. Then, it was refrigerated overnight at 4℃, while simultaneously refrigerating 500mL of anhydrous ethanol. The refrigerated anhydrous ethanol was poured into the refrigerated cellulose solution and stirred at room temperature for 12h to precipitate a solid. The solution was repeatedly diluted and washed with deionized water until the pH of the washing solution was 7. The pretreated bacterial cellulose was then filtered. 0.1g of the pretreated cotton cellulose and 0.1g of the catalyst were placed in 50mL of deionized water and hydrolyzed at 200℃ for 12min in a microwave reactor to obtain cellulose hydrolysate. The cellulose hydrolysate was placed in DMSO and stirred at room temperature for 7h, then sonicated at 40kHz for 1.5h. After filtration, washing, and freeze-drying, the exfoliated cotton cellulose nanosheets were obtained. The POM of the cellulose nanosheets extracted from cotton cellulose is shown in [reference needed]. Figure 8 .

[0078] (3) The cotton cellulose nanosheets were immersed in 0.05mol / L Ni(NO3)2·6H2O aqueous solution for 60min with stirring, freeze-dried, placed in a tube furnace, carbonized at 800℃ for 2h, with a heating rate of 10℃ / min, to obtain Ni nanoparticle-loaded cellulose nanosheets (CNS@Ni).

[0079] Figure 9 The performance of the CNS@Ni catalyst in Example 3 in the hydrogen evolution reaction is shown.

[0080] Example 4

[0081] Step (1) of Example 4 is the same as step (1) of Example 1. The only difference between step (2) and Example 1 is that bamboo cellulose is used in Example 4 instead of bacterial cellulose in Example 1. Step (3) is as follows:

[0082] Bamboo cellulose nanosheets were immersed in an aqueous solution of 0.5 mol / L AgNO3 and 0.5 mol / L Ni(NO3)2·6H2O for 60 min with stirring, freeze-dried, and then carbonized at 800℃ for 2 h in a tube furnace with a heating rate of 10℃ / min to obtain cellulose nanosheets supported by Ag-Ni bimetallic nanoparticles.

[0083] The POM of cellulose nanosheets extracted from bamboo cellulose is shown in [reference needed]. Figure 8 .

[0084] Example 5

[0085] Step (1) of Example 5 is the same as step (1) of Example 1. The only difference between step (2) and Example 1 is that: in Example 5, corn distillers' grains cellulose is used instead of bacterial cellulose in Example 1. Step (3) is as follows:

[0086] The cellulose nanosheets supported on Pt metal nanoparticles (CNS@Pt) were obtained by immersing corn distillers grains cellulose nanosheets in a 0.02 mol / L H2PtCl6·6H2O aqueous solution for 90 min with stirring, freeze-drying, carbonizing at 900℃ for 2 h in a tube furnace with a heating rate of 10℃ / min.

[0087] The POM of cellulose nanosheets extracted from corn distillers grains cellulose is shown in [link to POM]. Figure 8 .

[0088] Figure 10 The performance of the CNS@Pt catalyst in Example 5 is shown in the hydrogen evolution reaction.

[0089] Example 6

[0090] Step (1) of Example 6 is the same as step (1) of Example 1. The only difference between step (2) and Example 1 is that in step (2) of Example 6, rice straw cellulose is used instead of bacterial cellulose in Example 1. Step (3) is as follows:

[0091] Rice straw cellulose nanosheets were immersed in 0.5 mol / L Fe(NO3)3·9H2O aqueous solution for 100 min with stirring, freeze-dried, placed in a tube furnace, and carbonized at 780℃ for 3 h with a heating rate of 10℃ / min to obtain cellulose nanosheets supported by Fe metal nanoparticles.

[0092] The POM of cellulose nanosheets extracted from rice straw cellulose is shown in [reference needed]. Figure 8 .

[0093] Example 7

[0094] Step (1) of Example 7 is the same as step (1) of Example 1. The only difference between step (2) and Example 1 is that in step (2) of Example 7, straw cellulose is used instead of bacterial cellulose in Example 1. Step (3) is as follows:

[0095] Cellulose nanosheets loaded with Co metal nanoparticles were obtained by immersing straw cellulose nanosheets in a 0.5 mol / L Co(NO3)2·6H2O aqueous solution for 60 min with stirring, freeze-drying, and then carbonizing in a tube furnace at 800℃ for 2 h with a heating rate of 10℃ / min.

[0096] The POM of cellulose nanosheets extracted from wheat straw cellulose is shown in [reference needed]. Figure 8 .

[0097] Example 8

[0098] The difference between Example 8 and Example 1 is that in step (2) of Example 8, soybean stalk cellulose is used instead of bacterial cellulose in Example 1. Everything else is the same as in Example 1.

[0099] The POM of cellulose nanosheets extracted from soybean stalk cellulose is shown in [reference needed]. Figure 8 .

[0100] Example 9

[0101] The difference between Example 9 and Example 1 is that in step (2) of Example 9, microcrystalline cellulose is used instead of bacterial cellulose in Example 1. Everything else is the same as in Example 1.

[0102] The POM of cellulose nanosheets extracted from microcrystalline cellulose is shown in [reference needed]. Figure 8 .

[0103] All aspects, embodiments, and features of this invention should be considered illustrative in all respects and not limiting of the invention; the scope of the invention is defined only by the claims. Other embodiments, modifications, and uses will become apparent to those skilled in the art without departing from the spirit and scope of the invention as claimed.

[0104] In the preparation method of this invention, the order of the steps is not limited to the listed order. For those skilled in the art, variations in the order of the steps without creative effort are also within the scope of protection of this invention. Furthermore, two or more steps or actions can be performed simultaneously.

[0105] Finally, it should be noted that the specific embodiments described herein are merely illustrative examples of the invention and are not intended to limit the implementation of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them; it is neither necessary nor possible to exemplify all embodiments here. However, these obvious variations or modifications derived from the essential spirit of the invention still fall within the scope of protection of the invention, and interpreting them as any additional limitation would contradict the spirit of the invention.

Claims

1. A method for loading metal nanoparticles onto cellulose nanosheets, characterized in that, Includes the following steps: (1) Cellulose was reacted with zwitterionic catalyst in a polar solvent, and then the reactants were mechanically treated in a polar solvent to obtain cellulose nanosheets. (2) The cellulose nanosheets are uniformly mixed with the metal precursor and then subjected to reduction treatment to obtain cellulose nanosheets loaded with metal nanoparticles. Amphoteric catalysts contain both acidic and basic groups; The monomers used to prepare the zwitterionic catalysts are one or more of the following: phenol, hydroquinone, resorcinol, catechol, 1,3,5-trihydroxybenzene, bisphenol A, benzoic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, p-aminophenol, phenylenediamine, p-aminobenzamide, imidazole, pyrrole, benzimidazole, benzenesulfonic acid, 4-mercaptophenol, 1,3,5-benzenetrisulfonic acid, phenylphosphonic acid, aniline, dimethylaniline, pyridine aromatic hydrocarbons, carbazole, triazine, benzidine, 4-aminobenzenesulfonic acid, aminobenzoic acid, imidazolesulfonic acid, carbazole-carboxylic acids, phenylboronic acid, p-aminophenylboronic acid, p-nitrophenylboronic acid, 2-hydroxyphenylboronic acid, naphthaleneboronic acid, anthraquinone, vinylphenylboronic acid, 3,4-ethylenedioxythiophene, indole, pyrrole formaldehyde, pyrrole amino acids, chloropyridine, p-nitrophenol, p-nitroaniline, and 3-hydroxypyridine.

2. The preparation method according to claim 1, characterized in that, The preparation method of zwitterionic catalysts includes the following steps: One or more monomers, a Lewis acid catalyst, and an acetal are reacted in a weak / nonpolar solvent, and the mixture is filtered, washed, and dried to obtain a zwitterionic catalyst.

3. The preparation method according to claim 2, characterized in that, The molar ratio of monomer, Lewis acid catalyst, and acetal is 1:1 to 6:1 to 10; And / or, the Lewis acid is one or more of FeCl3, AlCl3, SnCl4, BF3·OEt3, ZnCl2, TiCl4, SbCl5, GaCl3, InCl3, and Sc(OTf)3; And / or, the acetal is one or more of dimethylformaldehyde, diethanolformaldehyde, and acetaldehyde-dimethylformaldehyde; And / or, the weak / nonpolar solvent is one or more of the following: dichloroethane, dichloromethane, p-dichlorobenzene, chlorobenzene, CS2, carbon tetrachloride, o-dichlorobenzene, m-dichlorobenzene, 1,2,4-trichlorobenzene, o-xylene, p-xylene, nitrobenzene, 1,3,5-tris(bromomethyl)benzene, and 1,4-bis(chloromethyl)benzene; And / or, in the preparation of zwitterionic catalysts, the reaction temperature is 80–120℃ and the reaction time is 10–30 h.

4. The preparation method according to claim 1, characterized in that, Before reacting with the zwitterionic catalyst, cellulose undergoes a pretreatment process, which includes any one or both of steps (1) and (2): (1) Add cellulose to water and / or alcohol solvents and extract at 70-150℃ for 1-24 hours with stirring. (2) Cellulose is treated with one or more of acids, alkalis, and enzymes, and then a solid is precipitated. It is washed with water until pH = 7 ± 0.

1.

5. The preparation method according to claim 1, characterized in that, The mass ratio of zwitterionic catalyst to cellulose is 0.5–3:1; And / or, the mass ratio of cellulose to polar solvent is 1:1 to 500; And / or, the polar solvent is one or more of water, DMSO, ionic liquid, ethanol, methanol, and isopropanol; And / or, the reaction temperature is 30–400℃, and the reaction time is 5 min–10 h; And / or, the apparatus used for the reaction is one of the following: ball mill, ultrasonic treatment, mechanical crushing, high-pressure reactor, microwave reactor, ultrasonic reactor, electric heating reactor, or steam explosion machine; And / or, the reactants are placed in a polar solvent to swell for 1–20 h, then subjected to mechanical treatment by sonication for 10–100 min, filtered, and dried to obtain exfoliated cellulose nanosheets.

6. The preparation method according to claim 1, characterized in that, The cellulose is one or more of the following: corn cob cellulose, straw cellulose, cotton cellulose, distiller's grains cellulose, wood cellulose, hemp cellulose, bamboo cellulose, bacterial cellulose, viscose fiber, cuprammonium cellulose, acetate cellulose, modal fiber, lyocell fiber, Tencel fiber, nanocellulose, microcrystalline cellulose, cellulose ethers, red algae cellulose, brown algae cellulose, green algae cellulose, blue algae cellulose, Euglena cellulose, Congo red algae cellulose, Nostoc cellulose, Chlamydomonas cellulose, Chlorella cellulose, and Spirulina cellulose; And / or, the metal precursor is H2PtCl6·6H2O, platinum acetylacetonate, PdCl2, Pd(acac)2, RuCl3·xH2O, Ru(acac)3, RhCl3·xH2O, Rh(acac)3, HAuCl4·3H2O, AgNO3, Ni(NO3)2·6H2O, Ni(acac)2, NiCl2·6H2O, Fe(NO3)3·9H2O, Fe(acac)3, FeCl3·6H2O, Co(NO3)2·6H2O, Co(acac)2, Mn(NO3)2·4H2O, Mn(acac)3, Cu(NO3)2·3H2O, Cu(acac)2, Zn(NO3)2·6H2O, Zn(acac)2, Ce(NO3)3·6H2O, Ce(acac)3, Ga(NO3)3, Ga(acac)3, (NH4)6Mo7O 12 , 12 , 12 , 12 , 12 , 12 , 12 , 11 , 12 , 12 , 10 , 12 , x , 2.5 , 12 , 40 , 40 , 40 , 40 , 40 , 40 , 40 , 40 , 3-x , 40 , 40 , 40 , 40 , 40 , 0.5 ·4H2O, MoO2(acac)2, Na2WO4, WO3, WCl6, H3PW 12 O 40 ·xH2O, H3PMo 12 O 40 ·xH2O, H4SiW 12 O 40 ·xH2O, H4SiMo 12 O 40 ·xH2O, H5[PMo 10 V2O 40 , H3[PMo[[ID=​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​Ce3PW 12 O 40 ,PBu4PW 12 O 40 CTA-PW 12 O 40 Cs-NH4-PW 12 O 40 One or more of the following; And / or, the methods for mixing cellulose nanosheets with metal precursors include one or more of the following: liquid phase mixing, impregnation, gelation, sol-gel, evaporation-induced assembly, spray drying, spray lyophilization, and freeze-mixing.

7. The preparation method according to claim 1, characterized in that, The reduction treatment is one or more of carbonization treatment, hydrothermal treatment, and microwave heating. When the reduction treatment is carbonization treatment, the heating rate is 1-10℃ / min, the carbonization temperature is 250-1500℃, and the holding time is 1-8h. When the reduction treatment is hydrothermal treatment, the hydrothermal temperature is 150-300℃ and the hydrothermal treatment time is 2-24h.

8. A composite material, characterized in that, It is prepared by any one of the preparation methods described in claims 1-7, wherein the composite material comprises cellulose nanosheets and metal nanoparticles, wherein the metal nanoparticles are loaded on the surface of the cellulose nanosheets.

9. A composite material according to claim 8, characterized in that, The cellulose nanosheets have a length of 1–40 μm and a thickness of 2–50 nm; And / or, the average diameter of the metal nanoparticles is 0.5–50 nm; And / or, the metal loading is 0.1 to 30 wt%.

10. The application of the composite material as described in claim 8 in electrocatalysis, conductive frameworks for capacitors or lithium batteries, catalytic degradation of organic pollutants, adsorption of heavy metals or water purification, antibacterial dressings or bioelectronic devices.

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