A CDs-loaded MIL-53(Fe)-NO2 oxide nanozyme and its preparation method and application

Abstract

The present invention provides a CDs-loaded MIL-53(Fe)-NO2-type oxide nanozyme and its preparation method and application, which belong to the technical field of carbon-based nanomaterials. The present invention uses MIL-53(Fe)-NO2 as a carrier matrix, and through a one-step microwave method, carbon dots rich in nitrogen and oxygen functional groups are loaded into MIL-53(Fe)-NO2 to obtain CDs@MIL-53(Fe)-NO2-type oxide nanozymes. The preparation process of the present invention is simple and fast, which solves the problem that the existing CDs@MOFs-type oxide nanozymes do not have oxidase-like activity in the absence of external stimulation. The obtained CDs@MIL-53(Fe)-NO2 has excellent oxidase activity in the absence of external stimulation, and can be applied to the fields of biosensing, pharmaceuticals, food, antibacterial, environmental protection, etc., and can be further applied to the fields of bioanalysis and food safety.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon-based nanomaterials, and in particular to a CDs-loaded MIL-53(Fe)-NO2 type oxide nanozyme, a preparation method thereof, and applications thereof. Background Art

[0002] Nanozymes are a class of nanomaterials with intrinsic enzyme-like properties. Compared to natural enzymes, they offer unique advantages such as low cost, high stability, and scalable production. They are a key research front in 2022. Since Yan et al. unexpectedly discovered in 2007 that Fe₃O₄ nanoparticles exhibit peroxidase-like activity, over 1,100 nanozymes have been created, including peroxidase (POD) mimics, oxidase (OXD) mimics, catalase mimics, and superoxide dismutase mimics. To date, only POD mimics have been widely reported, while research on oxidase mimics is extremely scarce.

[0003] Metal-organic frameworks (MOFs) are three-dimensional (3D) network materials connected by organic ligands and metal nodes. As a rising star among oxide-like nanozymes, MOFs have attracted much attention due to their porous structure, excellent stability and rich active sites composed of transition metals. However, the catalytic activity of original MOFs is usually very low. Therefore, researchers have adopted several modification methods to improve the catalytic performance of MOFs. One is based on the modifiability of organic ligands, and the catalytic performance is improved by changing the functional groups on the ligands. Benefiting from the porosity of MOFs, another feasible strategy is to introduce relevant metal nanoparticles, natural enzymes and other substances into MOFs to form complexes or hybrids.

[0004] Carbon dots (CDs) are quasi-spherical nanoparticles less than 10 nm in size and represent a new type of zero-dimensional carbon-based nanomaterial discovered in recent years. CDs possess favorable physicochemical properties, such as ease of synthesis, low toxicity, and good biocompatibility, as well as a rich array of surface groups and nanoscale size. These unique properties make them ideal dopants for the fabrication of nanocomposites. Furthermore, CDs can act as electron donors / acceptors, accelerating electron transfer and thereby enhancing the catalytic performance of the composites. Furthermore, CDs rich in nitrogen and oxygen functional groups typically possess smaller band gaps, further enhancing the catalytic activity of the composites. Therefore, the rational preparation of CDs@MOFs composites and their use as highly efficient biomimetic enzymes is feasible. However, research on CDs@MOFs nanozymes is extremely limited, with only five reports. Regarding oxidase mimics, the only existing documented method is the successful synthesis of NCDs / UiO-66, but its oxidase-like activity requires stimulation from an external xenon lamp. Summary of the Invention

[0005] In view of this, the present invention aims to provide a CDs-loaded MIL-53(Fe)-NO2-like oxide nanozyme and its preparation method and application. The CDs-loaded MIL-53(Fe)-NO2-like oxide nanozyme provided by the present invention has excellent oxidase-like activity in the absence of external stimulation.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing CDs-loaded MIL-53(Fe)-NO2-type oxide nanozyme, comprising the following steps:

[0008] A soluble ferric iron source, nitroterephthalic acid, acetic acid, carbon dots containing nitrogen oxide functional groups, and an organic solvent were mixed and subjected to ultrasound and microwave heating in sequence to obtain CDs-loaded MIL-53(Fe)-NO2-like oxide nanozymes.

[0009] The microwave heating time is 20 to 40 minutes.

[0010] Preferably, the surface of the carbon dots contains nitrogen-containing and oxygen-containing functional groups, and the particle size of the carbon dots is 1 to 3 nm.

[0011] Preferably, the method for preparing carbon dots comprises the following steps:

[0012] Citric acid, ethylenediamine and water are mixed and subjected to a hydrothermal reaction to obtain carbon dots containing nitrogen and oxygen functional groups.

[0013] Preferably, the mass ratio of the soluble ferric iron source to nitroterephthalic acid is 1.3-1.4:0.5-0.6;

[0014] The volume ratio of the soluble ferric iron source to acetic acid is 1.3-1.4 g:1-2 mL.

[0015] Preferably, the mass ratio of the soluble ferric iron source to the carbon dots is 1.3-1.4:0.0046-0.016.

[0016] Preferably, the power of the ultrasound is 90 to 180 W, and the time is 15 to 20 minutes;

[0017] The microwave heating temperature is 160-180° C., and the power is 300-400W.

[0018] The present invention provides a CDs-loaded MIL-53(Fe)-NO2-type oxide nanozyme prepared by the above-mentioned preparation method, comprising MIL-53(Fe)-NO2 and carbon dots loaded on the surface and internal pores of the MIL-53(Fe)-NO2.

[0019] Preferably, the CDs-loaded MIL-53(Fe)-NO2-type oxide nanozyme has a spindle shape with a length of 3 to 5 μm and a width of 0.5 to 1 μm.

[0020] The present invention provides the application of the above-mentioned CDs-loaded MIL-53(Fe)-NO2-like oxide nanozyme as an oxide-like nanozyme.

[0021] Preferably, the CDs-loaded MIL-53(Fe)-NO2-type oxide nanozyme is used in the fields of biological analysis and food safety.

[0022] The present invention provides a method for preparing CDs-loaded MIL-53(Fe)-NO2-type oxide nanozyme (abbreviated as CDs@MIL-53(Fe)-NO2), comprising the following steps: mixing a soluble trivalent iron source, nitroterephthalic acid, acetic acid, carbon dots rich in nitrogen and oxygen functional groups, and an organic solvent, followed by ultrasonic and microwave heating to obtain the CDs-loaded MIL-53(Fe)-NO2-type oxide nanozyme. The present invention uses MIL-53(Fe)-NO2 as a carrier matrix and replaces the traditional solvent thermal method with a simple and time-saving one-step microwave method to dope the carbon dots rich in nitrogen and oxygen functional groups into MIL-53(Fe)-NO2 to obtain the CDs@MIL-53(Fe)-NO2-type oxide nanozyme. The present invention has achieved for the first time that the existing CDs@MOFs nanozymes have oxidase-like activity in the absence of external stimulation. The obtained CDs-loaded MIL-53(Fe)-NO2-like oxidase nanozyme can be applied to biosensing, pharmaceuticals, food, antibacterial, environmental protection and other fields, and can be further applied to bioanalysis and food safety.

[0023] The preparation method provided by the present invention is simple to operate, requires mild conditions, and is suitable for industrial large-scale production. Furthermore, the preparation method provided by the present invention is fast, and CDs@MIL-53(Fe)-NO2 can be successfully obtained in just 20 to 40 minutes. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The high-resolution transmission electron microscopy image and X-ray photoelectron spectroscopy spectrum of CDs obtained in Example 1 are shown;

[0025] Figure 2 The structural simulation and experimental XRD patterns of MIL-53(Fe)-NO2 obtained in Comparative Example 1 and the experimental XRD pattern of CDs@MIL-53(Fe)-NO2 obtained in Example 1;

[0026] Figure 3 This is a scanning electron microscope image of MIL-53(Fe)-NO2 obtained in Comparative Example 1;

[0027] Figure 4 This is a scanning electron microscope image of CDs@MIL-53(Fe)-NO2 obtained in Example 1;

[0028] Figure 5 This is a high-resolution transmission electron microscopy image of CDs@MIL-53(Fe)-NO2 obtained in Example 1;

[0029] Figure 6 The oxidase-like catalytic performance of the MIL-53(Fe)-NO2 obtained in Comparative Example 1 and the CDs@MIL-53(Fe)-NO2 composite material obtained in Example 1;

[0030] Figure 7 The oxidase-like catalytic performance of the MIL-53(Fe)-NO2 obtained in Comparative Example 1 and the CDs@MIL-53(Fe)-NO2 composite materials doped with different amounts of CDs obtained in Examples 1 and 2;

[0031] Figure 8 The oxidase-like catalytic properties of MIL-53(Fe), CDs@MIL-53(Fe), Fe-BTC, Cu-BDC obtained in Comparative Example 2 and CDs@MIL-53(Fe)-NO2 composite material obtained in Example 1. DETAILED DESCRIPTION

[0032] The present invention provides a method for preparing CDs-loaded MIL-53(Fe)-NO2-type oxide nanozyme, comprising the following steps:

[0033] A soluble ferric iron source, nitroterephthalic acid, acetic acid, carbon dots containing nitrogen oxide functional groups, and an organic solvent were mixed and subjected to ultrasound and microwave heating in sequence to obtain CDs-loaded MIL-53(Fe)-NO2-like oxide nanozymes.

[0034] The microwave heating time is 20 to 40 minutes.

[0035] Unless otherwise specified, the raw materials used in the present invention are all commercially available.

[0036] In the present invention, the carbon dots contain nitrogen- and oxygen-containing functional groups on their surfaces and have a particle size of 1 to 3 nm. The present invention requires the following properties for the carbon dots: ease of synthesis, abundance of nitrogen and oxygen functional groups on their surfaces, and ease of complexing with the MOF matrix. The present invention has no particular requirements for the source of the carbon dots; commercially available carbon dots or self-prepared carbon dots can be used. When self-preparing the carbon dots, the preparation method preferably includes the following steps:

[0037] Citric acid, ethylenediamine and water are mixed and subjected to a hydrothermal reaction to obtain carbon dots containing nitrogen and oxygen functional groups.

[0038] In the present invention, the mass ratio of the citric acid to the volume ratio of ethylenediamine is preferably 4.6-5.2 g:1.5-1.7 mL, more preferably 5 g:1.6 mL. In the present invention, the mass ratio of the citric acid to the volume ratio of water is preferably 4.6-5.2 g:50 mL, more preferably 5 g:50 mL.

[0039] In the present invention, the mixing method is preferably stirring mixing, and the stirring time is preferably 5 to 15 minutes, more preferably 8 to 10 minutes.

[0040] In the present invention, the hydrothermal reaction is preferably carried out in a stainless steel reactor lined with polytetrafluoroethylene. The temperature of the hydrothermal reaction is preferably 180-200° C., more preferably 190° C.; the time is preferably 5-6 h, more preferably 5.5 h.

[0041] After the hydrothermal reaction, the present invention preferably performs post-treatment on the obtained hydrothermal reaction solution, and the post-treatment preferably includes the following steps:

[0042] The hydrothermal reaction solution is cooled, microfiltered, dialyzed and freeze-dried to obtain carbon dot powder.

[0043] In the present invention, the cooling is preferably natural cooling to room temperature. A 0.22-micron filter is preferably used for microfiltration to obtain a brownish-yellow solution. The molecular weight cutoff for dialysis is preferably 500-1000, more preferably 600-800. The dialysis duration is preferably 1-2 days. After dialysis, the dialyzed product is preferably dispersed in water. The freeze-drying method is not particularly specified; freeze-drying methods familiar to those skilled in the art may be used.

[0044] In the present invention, the soluble ferric iron source is preferably ferric chloride, more preferably hexahydrate and ferric chloride. In the present invention, the mass ratio of the soluble ferric iron source to nitroterephthalic acid is preferably 1.3-1.4:0.5-0.6, and the volume ratio of the mass of the soluble ferric iron source to acetic acid is preferably 1.3-1.4 g:1-2 mL, more preferably 1.3-1.4 g:1.5 mL.

[0045] In the present invention, the mass ratio of the soluble ferric iron source to the carbon dots is preferably 1.3-1.4:0.0046-0.016, and more preferably 1.3-1.4:0.008-0.012.

[0046] In the present invention, the organic solvent is preferably N,N-dimethylformamide. In the present invention, the volume ratio of the soluble ferric iron source to the organic solvent is preferably 1.3-1.4 g:15-20 mL.

[0047] In the present invention, the mixing method is preferably stirring, and the stirring time is preferably 20 to 30 minutes, more preferably 25 minutes.

[0048] In the present invention, the power of the ultrasound is 90 to 180 W, preferably 140 to 160 W; the time is preferably 15 to 20 min, more preferably 16 to 18 min.

[0049] In the present invention, the microwave heating temperature is preferably 160-180° C., more preferably 170° C.; the power is preferably 300-400 W, more preferably 350 W; and the time is 20-40 min, preferably 30 min.

[0050] In the present invention, after the microwave heating, the obtained suspension is preferably subjected to post-treatment, and the post-treatment preferably comprises the following steps:

[0051] The suspension is sequentially cooled, centrifugally washed and dried.

[0052] In the present invention, the cooling is preferably natural cooling to room temperature. In the present invention, the detergent used in the centrifugal washing is preferably N,N-dimethylformamide and ethanol, and the centrifugal speed is preferably 8000-10000 rpm, more preferably 9000 rpm. In the present invention, the drying is preferably vacuum drying, and the drying temperature is preferably 60-80°C, more preferably 70°C.

[0053] The present invention provides a CDs-loaded MIL-53(Fe)-NO2-type oxide nanozyme prepared by the above-mentioned preparation method, comprising MIL-53(Fe)-NO2 and carbon dots loaded on the surface and internal pores of the MIL-53(Fe)-NO2.

[0054] In the present invention, the CDs-loaded MIL-53(Fe)-NO2-type oxide nanozyme has a spindle shape, with a length of preferably 3 to 5 μm, more preferably 4 μm; and a width of preferably 0.5 to 1 μm, more preferably 0.6 to 0.8 μm.

[0055] The present invention provides the use of the CDs-loaded MIL-53(Fe)-NO2-like oxide nanozyme as an oxide-like nanozyme. This invention demonstrates for the first time that existing CDs@MOFs nanozymes exhibit oxidase-like activity in the absence of external stimulation. The resulting CDs-loaded MIL-53(Fe)-NO2-like oxide nanozyme can be applied in biosensing, pharmaceuticals, food, antimicrobial, and environmental protection fields, and specifically in bioanalysis and food safety.

[0056] In the present invention, the CDs-loaded MIL-53(Fe)-NO2-type oxidase nanozyme is preferably used to catalyze one or more of oxidase substrates such as 3,3',5,5'-tetramethylbenzidine (TMB), o-phenylenediamine (OPD), and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS).

[0057] The following examples describe in detail the CDs-loaded MIL-53(Fe)-NO2-type oxide nanozyme provided by the present invention, its preparation method, and application, but they should not be understood as limiting the scope of protection of the present invention.

[0058] Example 1

[0059] (1) Preparation of carbon dots CDs

[0060] 4.8 g of citric acid was dissolved in 50 mL of water, followed by the addition of 1.675 mL of ethylenediamine and stirring for 10 minutes. The homogeneously mixed, clear solution was transferred to a Teflon-lined stainless steel reactor and heated statically in a 200°C oven for 6 hours. The reactor was removed, cooled naturally, and filtered through a 0.22 μm filter to yield a brownish-yellow solution. This solution was then dialyzed for one day using a 500 molecular weight cutoff dialysis bag to obtain CDs directly dispersed in water. The solution was then freeze-dried to yield a brownish-black, quasi-spherical CD powder with a particle size of 1 to 3 nm.

[0061] (2) Preparation of CDs@MIL-53(Fe)-NO2-like oxide nanozymes

[0062] CDs@MIL-53(Fe)-NO2 was prepared via a time-saving, one-step microwave method. First, 1.35 g of hexahydrate, ferric chloride, and 0.524 g of nitroterephthalic acid were dissolved in 15 mL of N,N-dimethylformamide. Then, 1 mL of acetic acid was added. Then, 10.8 mg of CDs solid powder was added to the mixture, stirred for 30 minutes, ultrasonicated for 15 minutes, and microwave-heated at 300 W at 170°C for 30 minutes to obtain a suspension containing the product. The suspension was cooled to room temperature and washed several times by centrifugation at 9000 rpm with N,N-dimethylformamide and ethanol. The suspension was then dried in vacuo at 70°C to obtain spindle-shaped CDs@MIL-53(Fe)-NO2 solid powders measuring 3 to 5 μm in length and 0.5 to 1 μm in width.

[0063] Example 2

[0064] Preparation of CDs@MIL-53(Fe)-NO2-like oxide nanozymes doped with different amounts of CDs

[0065] 1.35 g hexahydrate, ferric chloride and 0.524 g nitroterephthalic acid were dissolved in 15 mL N,N-dimethylformamide, and then 1 mL acetic acid solution was added thereto. Then, 4.6 mg, 13 mg and 16 mg of CDs solid powder were weighed respectively and added to the above mixed solution, stirred for 30 minutes, ultrasonicated for 15 minutes, and heated with a 300 W microwave at 170°C for 30 minutes. The suspension containing the product was naturally cooled to room temperature and centrifuged and washed several times with N,N-dimethylformamide and ethanol at 8000 rpm. Then, it was vacuum dried at 60°C to obtain CDs@MIL-53(Fe)-NO2 solid powder doped with different amounts of CDs.

[0066] Comparative Example 1

[0067] Preparation of Metal-Organic Framework Material MIL-53(Fe)-NO2

[0068] The preparation method of MIL-53(Fe)-NO2 is the same as that in Example 1, except that CDs solid powder is not added, and spindle-shaped MIL-53(Fe)-NO2 solid powder is obtained with a length of 9 to 12 microns and a width of 1 to 3 microns.

[0069] Comparative Example 2

[0070] Preparation of Metal-Organic Framework Materials MIL-53(Fe), CDs@MIL-53(Fe), Fe-BTC, and Cu-BDC

[0071] In order to highlight the good pre-design and reasonable screening of MOF matrices in the present invention, other MOFs with different metals and different ligands than CDs@MIL-53(Fe)-NO2 were synthesized in the present invention.

[0072] The preparation of MIL-53(Fe) is basically the same as that in Comparative Example 1, except that nitroterephthalic acid is replaced by terephthalic acid.

[0073] The preparation of CDs@MIL-53(Fe) was basically the same as that in Example 1, and the amount of doped CDs was 10.8 mg. The difference was that nitroterephthalic acid was replaced by terephthalic acid.

[0074] Preparation of Fe-BTC: Dissolve 0.264 g of hexahydrate, ferric chloride, and 0.168 g of phthalic acid in a mixture of 10 mL of N,N-dimethylformamide, 2 mL of ethanol, and 1 mL of water. Transfer the solution to a 25 mL stainless steel Teflon-sealed reactor and react at 150°C for 24 hours. After cooling to room temperature, the mixture was centrifuged and washed several times with N,N-dimethylformamide and ethanol at 8000 rpm to obtain Fe-BTC.

[0075] Preparation of Cu-BDC: Dissolve 2.41 g of copper nitrate trihydrate and 0.83 g of terephthalic acid in 60 mL of N,N-dimethylformamide. Transfer the solution to a 100 mL stainless steel Teflon-sealed reactor and react at 110°C for 36 h. After cooling to room temperature, the mixture was centrifuged and washed several times with N,N-dimethylformamide and ethanol at 8000 rpm to obtain Cu-BDC.

[0076] Structural characterization

[0077] Figure 1 The high-resolution transmission electron microscope image and X-ray photoelectron spectroscopy spectrum of CDs obtained in Example 1 are shown in FIG. Figure 1 It can be seen that the CDs prepared in the present invention are uniformly dispersed quasi-spherical particles with a particle size of about 2 nm and rich in nitrogen and oxygen elements.

[0078] Figure 2 The figure is a comparison of the structure simulation XRD pattern and experimental XRD pattern of MIL-53(Fe)-NO2 obtained in comparative example 1 and CDs@MIL-53(Fe)-NO2 obtained in example 1. Figure 2 It can be seen that the diffraction peak positions of the experimentally measured powder X-ray diffraction spectrum of the solid sample and the simulated XRD spectrum are basically consistent, which indicates that MIL-53(Fe)-NO2 and CDs@MIL-53(Fe)-NO2 composite materials are successfully prepared, and the doping of CDs will not affect the crystallization of MIL-53(Fe)-NO2.

[0079] Figure 3 The scanning electron microscope image of MIL-53(Fe)-NO2 obtained in Comparative Example 1 is shown in FIG. Figure 3 It can be seen that the morphology of the MIL-53(Fe)-NO2 prepared in the present invention is spindle-shaped, with a length of 9 to 12 microns and a width of 1 to 3 microns.

[0080] Figure 4 This is a scanning electron microscope image of CDs@MIL-53(Fe)-NO2 obtained in Example 1. Figure 4 It can be seen that the morphology of CDs@MIL-53(Fe)-NO2 prepared in the present invention is spindle-shaped, with a length of 3 to 5 microns and a width of 0.5 to 1 micron.

[0081] Figure 5 This is a high-resolution transmission electron micrograph of CDs@MIL-53(Fe)-NO2 obtained in Example 1. Figure 5 It can be seen that the CDs@MIL-53(Fe)-NO2 prepared by the present invention contains black carbon particles smaller than 10 nm, which indicates that CDs are successfully loaded on MIL-53(Fe)-NO2.

[0082] Performance Testing

[0083] The oxidase-like activity of MIL-53(Fe)-NO2, CDs@MIL-53(Fe)-NO2 and comparative MOFs (MIL-53(Fe), CDs@MIL-53(Fe), Fe-BTC and Cu-BDC) was confirmed by using 3,3',5,5'-tetramethylbenzidine (TMB) as a chromogenic substrate.

[0084] 40 μg / mL MIL-53(Fe)-NO2, CDs@MIL-53(Fe)-NO2, comparative MOFs and 0.5 mM TMB were added to acetate buffer solution (pH 3.0). After 25 minutes of reaction, the UV-visible absorption spectrum of the mixed solution was recorded.

[0085] Figure 6 The oxidase-like catalytic performance of the MIL-53(Fe)-NO2 obtained in Comparative Example 1 and the CDs@MIL-53(Fe)-NO2 composite material obtained in Example 1.

[0086] Depend on Figure 6It can be seen that both the MIL-53(Fe)-NO2 and CDs@MIL-53(Fe)-NO2 composite materials prepared by the present invention absorb at 652nm, and the absorption of the CDs@MIL-53(Fe)-NO2 composite material is stronger than that of MIL-53(Fe)-NO2. This shows that both the MIL-53(Fe)-NO2 and CDs@MIL-53(Fe)-NO2 composite materials prepared by the present invention have oxidase-like properties, and the doping of CDs significantly enhances the oxidase-like properties of MIL-53(Fe)-NO2.

[0087] Figure 7 The oxidase-like catalytic performance of the MIL-53(Fe)-NO2 composite material obtained in Comparative Example 1 and the CDs@MIL-53(Fe)-NO2 composite material obtained in Example 2.

[0088] Depend on Figure 7 As can be seen, the CDs@MIL-53(Fe)-NO2 composites prepared in this invention, with varying CDs doping levels, all exhibit absorption at 652 nm, and the absorption value varies with the CDs doping level. This indicates that the CDs@MIL-53(Fe)-NO2 composites prepared in this invention all exhibit oxidase-like properties, and this can be adjusted by doping with varying CDs levels.

[0089] Figure 8 The oxidase-like catalytic properties of MIL-53(Fe), CDs@MIL-53(Fe), Fe-BTC, Cu-BDC obtained in Comparative Example 2 and CDs@MIL-53(Fe)-NO2 composite material obtained in Example 1.

[0090] Depend on Figure 8 It can be seen that Fe-BTC, MIL-53(Fe), and CDs@MIL-53(Fe) all absorb at 652nm. The absorption of Fe-BTC is very weak, while the absorption of MIL-53(Fe) and CDs@MIL-53(Fe) is strong, which shows the influence of the ligand on the performance of MOF-based oxidases. In addition, the absorption of CDs@MIL-53(Fe) is stronger than that of MIL-53(Fe), which shows that the CDs used in the present invention can not only enhance the oxidase activity of MIL-53(Fe)-NO2, but also enhance the oxidase activity of other MOFs. In addition, compared with MIL-53(Fe)(Fe-BDC), Cu-BDC has no absorption at 652nm, which shows that the metal center has an impact on the performance of MOF-based oxidases. The above synergistically illustrates that the present invention has carried out good pre-design and reasonable screening of MOF matrices. Compared with other similar MOFs and CDs@MOF, the CDs@MIL-53(Fe)-NO2 composite material prepared by the present invention has excellent oxidase-like properties that are superior to them.

[0091] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing CDs-loaded MIL-53(Fe)-NO2-type oxide nanozyme, comprising the following steps: A soluble ferric iron source, nitroterephthalic acid, acetic acid, carbon dots containing nitrogen oxide functional groups, and an organic solvent were mixed and subjected to ultrasound and microwave heating in sequence to obtain CDs-loaded MIL-53(Fe)-NO2-like oxide nanozymes. The microwave heating time is 20 to 40 minutes; the microwave heating temperature is 160 to 180°C, and the power is 300 to 400W; The surface of the carbon dots contains nitrogen-containing and oxygen-containing functional groups, and the particle size of the carbon dots is 1 to 3 nm; The mass ratio of the soluble ferric iron source to the carbon dots is 1.3-1.4:0.0046-0.016; The volume ratio of the soluble ferric iron source to acetic acid is 1.3-1.4 g:1-2 mL.

2. The preparation method according to claim 1, characterized in that The method for preparing carbon dots comprises the following steps: Citric acid, ethylenediamine and water are mixed and subjected to a hydrothermal reaction to obtain carbon dots containing nitrogen and oxygen functional groups.

3. The preparation method according to claim 1, characterized in that The mass ratio of the soluble ferric iron source to nitroterephthalic acid is 1.3-1.4:0.5-0.

6.

4. The preparation method according to claim 1, characterized in that The power of the ultrasound is 90 to 180 W, and the time is 15 to 20 minutes.

5. The CDs-loaded MIL-53(Fe)-NO2-type oxide nanozyme prepared by the preparation method according to any one of claims 1 to 4 comprises MIL-53(Fe)-NO2 and carbon dots loaded on the surface and internal pores of the MIL-53(Fe)-NO2.

6. The CDs-loaded MIL-53(Fe)-NO2-type oxide nanozyme according to claim 5, characterized in that The CDs-loaded MIL-53(Fe)-NO2-type oxide nanozyme has a spindle shape, a length of 3 to 5 μm, and a width of 0.5 to 1 μm.

7. Use of the CDs-loaded MIL-53(Fe)-NO2-like oxide nanozyme according to claim 5 or 6 as an oxide-like nanozyme.

8. The use according to claim 7, characterized in that The CDs-loaded MIL-53(Fe)-NO2 oxide nanozyme is used in the fields of biological analysis and food safety.

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