A MOF-Derived Three-Dimensional CA-CoNiMn-CLDHs Nanozyme and Its Preparation Method

Abstract

The present invention provides a MOF-derived three-dimensional CA-CoNiMn-CLDHs nanozyme and its preparation method, which relates to the technical field of artificial nanozymes. The method includes: dissolving Co(NO3)2·6H2O and 2-methylimidazole (2-MIM) in methanol to prepare ZIF-67; dispersing ZIF-67 in a mixed solvent composed of N,N-dimethylformamide (DMF) and ethanol (EtOH), and stirring evenly at room temperature to form solution A; successively adding Ni(NO3)2·6H2O and MnCl2·4H2O to 10 mL of distilled water, and magnetically stirring evenly to form solution B; quickly adding solution B to solution A, stirring evenly, and carrying out a hydrothermal reaction to form CoNiMn-LDHs; placing CoNiMn-LDHs in a tubular furnace for high-temperature calcination to form CoNiMn-CLDHs, and successfully preparing CA-CoNiMn-CLDHs after modification with citric acid (CA). A MOF-derived three-dimensional CA-CoNiMn-CLDHs nanozyme and its preparation method of the present invention have excellent peroxidase-like activity, and a visual detection platform established based on this nanozyme can realize the visual and sensitive detection of trace phenol in water bodies.

Description

Technical Field

[0001] The present invention relates to the technical field of artificial nanozymes, and in particular, to a MOF-derived three-dimensional CA-CoNiMn-CLDHs nanozyme and a preparation method thereof. Background Art

[0002] Phenol is a common water pollutant, mainly from plastics, dyes, chemical plants and pharmaceutical enterprises. It has high toxicity and carcinogenicity and is difficult to degrade and remove by itself under natural conditions, causing cumulative pollution to human health and the ecological environment. Therefore, rapid and sensitive detection of phenol pollutants in water is the key to effectively repairing phenol-polluted water bodies. Currently, the methods for phenol detection mainly include chromatography, electrochemistry, fluorescence and spectrophotometry. The above methods usually require sophisticated instruments, complex processing procedures and professional technicians, and it is difficult to achieve on-site detection. The colorimetric detection method based on nanozymes has the advantages of simple operation, low cost and on-site visualization, and is an effective method for on-site detection of phenol in water.

[0003] As a nanomaterial with excellent enzyme-like catalytic activity, nanozymes have significant advantages such as low cost, high stability and easy storage, and are widely used in sensors with high catalytic efficiency. In particular, inorganic nanozymes with peroxidase-like activity have been successfully used for colorimetric detection of pollutants, including carbon-based nanozymes, metal-based nanozymes, metal oxide-based nanozymes and other nanozymes. Among them, nanozymes derived from metal-organic frameworks (MOFs) have received extensive attention due to their large specific surface area, rich pores and highly exposed active sites, and have been successfully applied to the preparation of biosensors. However, the narrow pores and easy aggregation of MOF materials are not conducive to the diffusion of pollutant molecules in MOF materials, and also hinder the effective contact between pollutants and active sites, resulting in a significant reduction in their catalytic efficiency. In the prior art, it is impossible to achieve sensitive on-site visualization detection of phenol in water; ZIF-67 has poor stability in acidic environments and cannot fully exert the catalytic role of Co active sites; and there is less research on the low-cost large-scale preparation of MOF-derived hollow-structured ternary synergistic inorganic nanozymes. Summary of the Invention

[0004] Aiming at the above technical problems, the present invention provides a preparation method of a MOF-derived three-dimensional CA-CoNiMn-CLDHs nanozyme. Using ZIF-67 as a template, three-dimensional multi-level hollow-structured CoNiMn-LDHs are prepared by a simple one-step solvothermal method. After high-temperature calcination and surface functionalization modification with CA, the catalytic activity and chemical stability of the nanozyme are further improved; by using the excellent peroxidase-like activity of the CA-CoNiMn-CLDHs nanozyme, sensitive visualization detection of trace phenol in water can be effectively achieved.

[0005] To solve the above problems, the present invention provides a method for preparing MOF-derived three-dimensional CA-CoNiMn-CLDHs nanozyme, which is used to prepare any of the above-mentioned three-dimensional CA-CoNiMn-CLDHs nanozymes, and includes the following steps:

[0006] Step S1: Dissolve Co(NO3)2•6H2O and 2-methylimidazole (2-MIM) in methanol respectively to prepare ZIF-67;

[0007] Step S2: Disperse ZIF-67 in a mixed solvent composed of N,N-dimethylformamide (DMF) and ethanol (EtOH), and stir evenly at room temperature to form solution A;

[0008] Step S3: Add Ni(NO3)2•6H2O and MnCl2•4H2O to distilled water in sequence, and stir magnetically to form solution B evenly;

[0009] Step S4: Quickly add solution B to solution A, stir evenly, and carry out hydrothermal reaction in a reaction kettle to form CoNiMn-LDHs;

[0010] Step S5: Place CoNiMn-LDHs in a tube furnace for high-temperature calcination to form CoNiMn-CLDHs, and successfully prepare CA-CoNiMn-CLDHs after modification with citric acid (CA).

[0011] Optionally, in step S1, the mass range of Co(NO3)2•6H2O is 500-600 mg, the mass range of 2-methylimidazole is 600-700 mg, the volume of methanol is 40-80 mL, the reaction temperature is room temperature, and the reaction time is 12-40 h.

[0012] Optionally, in step S2, the mass of ZIF-67 is 80-100 mg, the volume of DMF is 20-50 mL, and the volume of EtOH is 20-50 mL.

[0013] Optionally, in step S3, the mass ratio of Ni(NO3)2•6H2O to MnCl2•4H2O is 1:1, and the volume of distilled water is 5-20 mL.

[0014] Optionally, in step S4, the solvent thermal reaction temperature is 90-120 °C, and the reaction time is 1-3 h.

[0015] Optionally, in step S5, the calcination temperature is 350-500 °C, the calcination time is 1-3 h, the heating rate is 1-5 °C / min, the concentration of citric acid is 5-20 mM, the volume of citric acid concentration is 50-100 mL, and the reaction time is 20-90 min.

[0016] Another object of the present invention is to provide a MOF-derived three-dimensional CA-CoNiMn-CLDHs nanozyme, which is prepared by the preparation method described in any one of the above.

[0017] Optionally, the nanozyme includes CoNiMn-CLDHs and a citric acid (CA) modification layer. The CoNiMn-CLDHs are prepared by ion-exchange derivation using ZIF-67 as a template, and the citric acid (CA) modification layer is fixed on the surface of the CoNiMn-CLDHs by chemical adsorption.

[0018] Optionally, the application of the CA-CoNiMn-CLDHs nanozyme in phenol detection.

[0019] Layered double hydroxides (LDHs) are an important class of inorganic layered materials, which have the advantages of adjustable host lamellar metal ions and large specific surface area, and are ideal nanosheet units with multi-level structures. Calcination of LDHs (CLDHs) at an appropriate temperature can form mixed metal oxides with higher dispersibility and activity, and their catalytic performance is further improved.

[0020] The CA-CoNiMn-CLDHs nanozyme prepared by the present invention has a three-dimensional multi-level hollow structure. Using ZIF-67 as a template, two-dimensional nanosheets are vertically derived on the surface of the ZIF-67 shell and interpenetrate to form a large number of mesopores, fully exposing the Co, Ni, and Mn metal active sites, and having excellent peroxidase-like activity; after surface modification with CA, the surface of the CA-CoNiMn-CLDHs nanozyme is negatively charged and has a higher affinity for positively charged substrate molecules, and has a high detection sensitivity for trace phenol in water.

[0021] In order to maximize the avoidance of the inherent disadvantages of MOFs materials, constructing derivative nanozymes with MOFs as templates or precursors can not only retain the advantages of MOFs, but also endow the derivatives with unique properties. In particular, by modulating the types of metal ions and controlling the reaction conditions, MOF-derived nanozymes with a three-dimensional multi-level hollow structure with unique structural morphology and excellent physical and chemical properties can be obtained. Combining the synergistic effects of multiple transition metal ions, the cross-assembly of two-dimensional nanosheets, and surface functionalization modification can further improve the catalytic activity of MOF-derived nanozymes, contribute to the on-site visual and sensitive detection of trace phenol in water, and also provide a new design idea for the design and development of MOF-derived nanozymes with multi-metal synergistic effects. Description of the Drawings

[0022] Figure 1It is the SEM image of the CA-CoNiMn-CLDHs nanozyme prepared in Example 3 of the present invention.

[0023] Figure 2 It is the SEM image of the CA-CoNiMn-CLDHs nanozyme prepared in Example 4 of the present invention.

[0024] Figure 3 It is the SEM image of the CA-CoNiMn-CLDHs nanozyme prepared in Example 5 of the present invention. Among them, Figure (a) is the SEM image of ZIF-67, Figure (b) is the SEM image of CoNiMn-LDHs, and Figure (c) is the SEM image of CA-CoNiMn-CLDHs.

[0025] Figure 4 It is the XRD pattern of the CA-CoNiMn-CLDHs nanozyme in Example 5 of the present invention.

[0026] Figure 5 It is the activity analysis diagram of the CA-CoNiMn-CLDHs nanozyme in Example 6 of the present invention. Figure (a) is the UV-Vis absorption spectrum diagram of different color development systems, and Figure (b) is the UV-Vis absorption spectrum diagram of the color development system with different radical scavengers added.

[0027] Figure 6 It is the UV-Vis absorption spectrum diagram of the colorimetric detection of phenol by the CA-CoNiMn-CLDHs in Example 7 of the present invention. Figure (a) is the UV-Vis absorption spectrum diagram of the colorimetric detection of different concentrations of phenol, and Figure (b) is the relationship curve diagram between the absorbance at 525 nm and the phenol concentration. Detailed implementation manners

[0028] To make the above objects, features, and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The embodiments described are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0029] Example 1:

[0030] This example provides a preparation method of MOF-derived three-dimensional CA-CoNiMn-CLDHs nanozyme. The specific method is as follows:

[0031] Step S1: Accurately weigh 500 mg of Co(NO3)2•6H2O and 600 mg of 2-MIM, dissolve them in 40 mL of methanol, stir magnetically for 10 min to form a homogeneous solution, and let it stand at room temperature for 24 h. After the reaction, centrifuge (6000 rpm, 3 min) to collect the purple product, wash it three times with methanol, and dry it at 60 °C to obtain ZIF-67;

[0032] Step S2: Accurately weigh 80 mg of ZIF-67 and disperse it evenly in a mixed solvent composed of 20 mL of DMF and 20 mL of EtOH, stir magnetically until homogeneous to form a uniform suspension A;

[0033] Step S3: Accurately weigh 80 mg of Ni(NO3)2•6H2O and 80 mg of MnCl2•4H2O, add them to 5 mL of distilled water, stir magnetically for 10 min to form a homogeneous solution B;

[0034] Step S4: Quickly pour the solution B in Step S3 into the suspension A in Step S2, continue to stir magnetically for 10 min to form a homogeneous solution, transfer it to a stainless steel autoclave, keep it at 90 °C for 1 h. After the reaction, cool it naturally to room temperature, centrifuge (6000 rpm, 3 min) to collect the product, wash it three times with distilled water, and dry it at 60 °C to obtain CoNiMn-LDHs;

[0035] Step S5: Place CoNiMn-LDHs in a tubular furnace, calcine it at 350 °C for 1 h in an air atmosphere, collect the product after calcination to obtain CoNiMn-CLDHs. Weigh 100 mg of CoNiMn-CLDHs and disperse it evenly in 50 mL of a 5 mM CA solution, stir magnetically at room temperature for 30 min, filter to collect the product, wash it 3 times with distilled water, and dry it at 60 °C to obtain CA-CoNiMn-CLDHs.

[0036] Example 2:

[0037] This example provides a method for preparing MOF-derived three-dimensional CA-CoNiMn-CLDHs nanozyme. The specific method is as follows:

[0038] Step S1: Accurately weigh 600 mg of Co(NO3)2•6H2O and 700 mg of 2-MIM, dissolve them in 80 mL of methanol, stir magnetically for 10 min to form a homogeneous solution, and let it stand at room temperature for 24 h. After the reaction, centrifuge (6000 rpm, 3 min) to collect the purple product, wash it three times with methanol, and dry it at 60 °C to obtain ZIF-67;

[0039] Step S2: Accurately weigh 100 mg of ZIF-67 and uniformly disperse it in a mixed solvent composed of 50 mL of DMF and 50 mL of EtOH, and stir magnetically until uniform to form a homogeneous suspension A;

[0040] Step S3: Accurately weigh 80 mg of Ni(NO3)2•6H2O and 80 mg of MnCl2•4H2O and add them to 20 mL of distilled water, and stir magnetically for 10 min to form a uniform solution B;

[0041] Step S4: Quickly pour the solution B in Step S3 into the suspension A in Step S2, continue to stir magnetically for 10 min to form a uniform solution, transfer it to a stainless-steel autoclave, keep it at 90 °C for 1 h, after the reaction is completed, naturally cool it to room temperature, centrifuge (6000 rpm, 3 min) to collect the product, wash it three times with distilled water, and dry it at 60 °C to obtain CoNiMn-LDHs;

[0042] Step S5: Place CoNiMn-LDHs in a tube furnace and calcine it at 500 °C for 3 h in an air atmosphere. After the calcination is completed, collect the product to obtain CoNiMn-CLDHs. Weigh 100 mg of CoNiMn-CLDHs and uniformly disperse it in 100 mL of a CA solution with a concentration of 20 mM, stir magnetically at room temperature for 90 min, filter and collect the product, wash it 3 times with distilled water, and dry it at 60 °C to obtain CA-CoNiMn-CLDHs.

[0043] Example 3:

[0044] This example provides a method for preparing MOF-derived three-dimensional CA-CoNiMn-CLDHs nanozyme. The specific method is as follows:

[0045] Step S1: Accurately weigh 582 mg of Co(NO3)2•6H2O and 656 mg of 2-MIM and dissolve them in 50 mL of methanol, stir magnetically for 10 min to form a uniform solution, and let it stand at room temperature for 12 h. After the reaction is completed, centrifuge (6000 rpm, 3 min) to collect the purple product, wash it three times with methanol, and dry it at 60 °C to obtain ZIF-67;

[0046] Step S2: Accurately weigh 80 mg of ZIF-67 and uniformly disperse it in a mixed solvent composed of 20 mL of DMF and 20 mL of EtOH, and stir magnetically until uniform to form a homogeneous suspension A;

[0047] Step S3: Accurately weigh 80 mg of Ni(NO3)2•6H2O and 80 mg of MnCl2•4H2O, add them to 10 mL of distilled water, and stir magnetically for 10 min to form a uniform solution B;

[0048] Step S4: Quickly pour the solution B in Step S3 into the suspension A in Step S2, continue to stir magnetically for 10 min to form a uniform solution, transfer it to a stainless steel autoclave, keep it at 100 °C for 2 h. After the reaction is completed, naturally cool it to room temperature, centrifuge (6000 rpm, 3 min) to collect the product, wash it three times with distilled water, and dry it at 60 °C to obtain CoNiMn-LDHs;

[0049] Step S5: Place CoNiMn-LDHs in a tubular furnace, calcine it at 350 °C for 2 h in an air atmosphere. After the calcination is completed, collect the product to obtain CoNiMn-CLDHs. Weigh 100 mg of CoNiMn-CLDHs and disperse it evenly in 50 mL of a 5 mM CA solution, stir magnetically at room temperature for 30 min, filter and collect the product, wash it 3 times with distilled water, and dry it at 60 °C to obtain CA-CoNiMn-CLDHs.

[0050] Figure 1 It is the SEM image of the prepared CA-CoNiMn-CLDHs nanozyme. As can be seen from Figure (a), ZIF-67 has a regular rhombic dodecahedron structure. Due to the short reaction time, the size of ZIF-67 is small, and there are a large number of small-sized ZIF-67 crystal nuclei. Figure (b) is the SEM image of CA-CoNiMn-CLDHs. It can be seen from the figure that the rhombic dodecahedron structure collapses and agglomeration occurs, resulting in the coverage of a large number of active sites.

[0051] Example 4:

[0052] This example provides a method for preparing MOF-derived three-dimensional CA-CoNiMn-CLDHs nanozyme. The specific method is as follows:

[0053] Step S1: Accurately weigh 582 mg of Co(NO3)2•6H2O and 656 mg of 2-MIM, dissolve them in 50 mL of methanol, stir magnetically for 10 min to form a uniform solution, and let it stand at room temperature for 24 h. After the reaction is completed, centrifuge (6000 rpm, 3 min) to collect the purple product, wash it three times with methanol, and dry it at 60 °C to obtain ZIF-67;

[0054] Step S2: Accurately weigh 80 mg of ZIF-67 and disperse it evenly in a mixed solvent composed of 20 mL of DMF and 20 mL of EtOH. Stir magnetically until homogeneous to form a uniform suspension A;

[0055] Step S3: Accurately weigh 80 mg of Ni(NO3)2•6H2O and 80 mg of MnCl2•4H2O and add them to 10 mL of distilled water. Stir magnetically for 10 min to form a homogeneous solution B;

[0056] Step S4: Quickly pour the solution B in Step S3 into the suspension A in Step S2, continue to stir magnetically for 10 min to form a homogeneous solution, transfer it to a stainless-steel autoclave, keep it at 90 °C for 2 h. After the reaction is completed, cool it naturally to room temperature, centrifuge (6000 rpm, 3 min) to collect the product, wash it three times with distilled water, and dry it at 60 °C to obtain CoNiMn-LDHs;

[0057] Step S5: Place CoNiMn-LDHs in a tubular furnace and calcine it at 350 °C for 2 h in an air atmosphere. After the calcination is completed, collect the product to obtain CoNiMn-CLDHs. Weigh 100 mg of CoNiMn-CLDHs and disperse it evenly in 50 mL of a CA solution with a concentration of 5 mM. Stir magnetically at room temperature for 30 min, filter to collect the product, wash it 3 times with distilled water, and dry it at 60 °C to obtain CA-CoNiMn-CLDHs.

[0058] Figure 2 It is the SEM image of the prepared CA-CoNiMn-CLDHs nanozyme. As can be seen from Figure (a), after extending the reaction time, the diameter of ZIF-67 becomes larger, and the size is uniform, showing a regular rhombic dodecahedron structure with a smooth surface. Figure (b) is the SEM image of CA-CoNiMn-CLDHs. As can be seen from the figure, after the hydrothermal reaction temperature decreases, the surface of the ZIF-67-derived nanozyme consists of a large number of two-dimensional nanosheets, and a large number of narrow pores formed by the interlaced growth of nanosheets can be clearly seen, but the three-dimensional hollow rhombic dodecahedron structure is destroyed.

[0059] Based on the experiments and the above embodiments, a preparation method of CA-CoNiMn-CLDHs nanozyme is finally determined, including the following steps:

[0060] Step S1: Dissolve Co(NO3)2•6H2O and 2-methylimidazole (2-MIM) in methanol respectively to prepare ZIF-67;

[0061] Specifically, Co(NO3)2•6H2O and 2-MIM were separately dissolved in methanol and stirred until dissolved. After forming a homogeneous solution, the methanol solution of Co(NO3)2•6H2O was slowly poured into the methanol solution of 2-MIM, and then continuously stirred magnetically until homogeneous, and left standing at room temperature.

[0062] In this example, the concentration range of Co(NO3)2•6H2O was 500 - 600 mg, and the concentration range of 2-methylimidazole was 600 - 700 mg. Preferably, it was 582 mg of Co(NO3)2•6H2O and 656 mg of 2-MIM. The magnetic stirring time after mixing the methanol solution of Co(NO3)2•6H2O and the methanol solution of 2-MIM was 10 min, and the standing time at room temperature was preferably 24 h.

[0063] Step S2: ZIF-67 was dispersed in a mixed solvent composed of N,N-dimethylformamide (DMF) and ethanol (EtOH), and stirred at room temperature until homogeneous to form solution A;

[0064] In this example, when adding ZIF-67, the addition amount of ZIF-67 was controlled so that its derivative was a three-dimensional hollow structure formed by the cross-linking of two-dimensional nanosheets, and the size was controlled to be about 1 μm.

[0065] Specifically, 80 mg of ZIF-67 was weighed and uniformly dispersed in a mixed solvent composed of 20 mL of DMF and 20 mL of EtOH, and stirred magnetically until homogeneous to form a uniform suspension A.

[0066] Step S3: Ni(NO3)2•6H2O and MnCl2•4H2O were successively added to distilled water and stirred magnetically until homogeneous to form solution B;

[0067] Specifically, 80 mg of Ni(NO3)2•6H2O and 80 mg of MnCl2•4H2O were accurately weighed and added to 10 mL of distilled water, and stirred magnetically for 10 min to form a homogeneous solution B.

[0068] Step S4: Solution B was quickly added to solution A, stirred until homogeneous, and subjected to a solvothermal reaction in a reaction kettle to form CoNiMn-LDHs;

[0069] The solvothermal reaction temperature and reaction time have an important influence on the morphology of the product. Appropriate reaction temperature and time can control the size of the two-dimensional nanosheets and the final morphology of the product, and MOF derivative CoNiMn-LDHs with rich porosity and large specific surface area can be obtained.

[0070] Specifically, the solvothermal reaction temperature was 90 °C and the reaction time was 1 h.

[0071] Step S5: Place CoNiMn-LDHs in a tubular furnace for high-temperature calcination to form CoNiMn-CLDHs, and successfully prepare CA-CoNiMn-CLDHs after modification with citric acid (CA).

[0072] High-temperature calcination can further optimize the physicochemical properties of LDHs-based catalysts. High-temperature calcination in an air atmosphere converts metal ions in the main layer of LDHs into composite metal oxides with adjustable acid-base properties. At the same time, the lattice confinement effect of the main layer induces highly dispersed metal active sites introduced into the interlayer. The specific surface area of the LDHs-derived catalyst obtained by high-temperature topological transformation is larger, the redox property is better, and the structure is more stable.

[0073] Surface functionalization modification is an effective way to improve the catalytic performance of materials. CA is rich in carboxyl functional groups and is negatively charged. After being fixed on the surface of CoNiMn-CLDHs through chemisorption, the surface of CoNiMn-CLDHs is negatively charged, while the chromogenic substrate with amino groups is positively charged. The two are quickly combined through electrostatic adsorption, which can further improve the catalytic activity of the nanozyme.

[0074] Specifically, the calcination temperature of CoNiMn-LDHs is 350 °C, the calcination time is 2 h, the heating rate is 1 °C / min, the CA concentration is 5 mM, the CA concentration volume is 50 mL, and the reaction time is 30 min.

[0075] The MOF-derived three-dimensional CA-CoNiMn-CLDHs nanozyme described in this example has a three-dimensional hollow structure, and its surface is composed of interlaced two-dimensional nanosheets, which fully exposes the metal active sites. The three-metal active sites act synergistically, and combined with surface functionalization modification, the prepared nanozyme has very excellent enzyme-like catalytic activity. The CA-CoNiMn-CLDHs nanozyme is prepared by a simple method combining solvothermal and high-temperature calcination, without expensive instruments and equipment. The preparation process is simple, the cost is low, and it is easy to realize batch synthesis.

[0076] The present invention first proposes to use ZIF-67 as a template to prepare a three-metal synergistic catalytic LDHs-based nanozyme. Through surface modification with CA, the enzyme-like catalytic activity of the nanozyme is further enhanced. Using ZIF-67 with rich pores and a large specific surface area as a template, through Ni 2+ , Mn 2+ and Co 2+The exchange interaction forms two-dimensional nanosheets that grow vertically on the surface of the ZIF-67 shell, cross each other, and form a hollow cage-like structure. At the same time, the original rhombic dodecahedron structure of ZIF-67 is also maintained. The three-dimensional porous material constructed by the two-dimensional nanosheets has highly exposed active sites, which is conducive to the efficient contact between substrate molecules and pollutant molecules, and has high sensitivity for the detection of trace pollutants in water. The three-dimensional LDHs prepared by this method have high dispersibility, effectively improving the agglomeration of two-dimensional LDHs. Moreover, high-temperature calcination reduction can transform LDHs into mixed metal oxides, and the strong interaction generated between metal oxides prevents the aggregation of metal nanoparticles, further improving the dispersibility of metal active sites. High-temperature calcination also helps to improve the structural stability of LDH-based catalysts.

[0077] Example Five:

[0078] Based on the above conclusions, this example provides a method for preparing MOF-derived three-dimensional CA-CoNiMn-CLDHs nanozyme. The specific method is as follows:

[0079] Step S1: Accurately weigh 582 mg of Co(NO3)2•6H2O and 656 mg of 2-MIM and dissolve them in 50 mL of methanol. Stir magnetically for 10 min to form a uniform solution, and let it stand at room temperature for 24 h. After the reaction is completed, centrifuge (6000 rpm, 3 min) to collect the purple product, wash it three times with methanol, and dry it at 60 °C to obtain ZIF-67;

[0080] Step S2: Accurately weigh 80 mg of ZIF-67 and disperse it evenly in a mixed solvent composed of 20 mL of DMF and 20 mL of EtOH. Stir magnetically to form a uniform suspension A;

[0081] Step S3: Accurately weigh 80 mg of Ni(NO3)2•6H2O and 80 mg of MnCl2•4H2O and add them to 10 mL of distilled water. Stir magnetically for 10 min to form a uniform solution B;

[0082] Step S4: Quickly pour the solution B in Step S3 into the suspension A in Step S2, continue to stir magnetically for 10 min to form a uniform solution, transfer it to a stainless steel autoclave, keep it at 90 °C for 1 h. After the reaction is completed, naturally cool it to room temperature, centrifuge (6000 rpm, 3 min) to collect the product, wash it three times with distilled water, and dry it at 60 °C to obtain CoNiMn-LDHs;

[0083] Step S5: Place CoNiMn-LDHs in a tubular furnace and calcine at 350 °C for 2 h in an air atmosphere. After the calcination is completed, collect the product to obtain CoNiMn-CLDHs. Weigh 100 mg of CoNiMn-CLDHs and disperse it evenly in 50 mL of a CA solution with a concentration of 5 mM. Stir magnetically at room temperature for 30 min, filter and collect the product, wash it 3 times with distilled water, and dry it at 60 °C to obtain CA-CoNiMn-CLDHs.

[0084] Based on the above embodiments, this embodiment provides a CA-CoNiMn-CLDHs nanozyme.

[0085] Figure 3 It is the SEM image of the prepared CA-CoNiMn-CLDHs nanozyme. As can be seen from Figure (a), ZIF-67 has a regular rhombic dodecahedron structure, with a smooth surface, uniform size, about 895 nm. Figure (b) shows that CoNiMn-LDHs maintains the rhombic dodecahedron morphology of ZIF-67, which is a hollow structure. Two-dimensional ultrathin nanosheets grow vertically on the surface and cross each other to form a dense shell layer. The thickness of the nanosheets is about 10 nm. Figure (c) is the SEM image of CA-CoNiMn-CLDHs. As can be seen from the figure, after high-temperature calcination, the structure and morphology of the nanozyme have not changed significantly, still being a three-dimensional multi-level hollow rhombic dodecahedron structure, and a large number of long and narrow pores formed by the interlaced growth of nanosheets can be clearly seen on the surface.

[0086] Figure 4 It is the XRD pattern of the prepared CA-CoNiMn-CLDHs nanozyme. In the ZIF-67 pattern, the characteristic diffraction peaks located at 7.53°, 10.64°, 12.91°, 16.69°, 18.29°, 22.36°, 24.81° and 26.88° correspond to the (011), (002), (112), (013), (222), (114), (233) and (134) crystal planes of ZIF-67 respectively. No other diffraction peaks are found, indicating that ZIF-67 has a high crystallinity. In the CoNiMn-LDHs pattern, after Ni 2+ and Mn 2+The exchange showed characteristic diffraction peaks of hydrotalcite-like compounds. The diffraction peaks at 11.02°, 22.45°, 33.88° and 59.95° corresponded to the (003), (006), (009) and (110) crystal planes of hydrotalcite-like compounds, respectively. At the same time, the diffraction peaks of ZIF-67 disappeared, indicating a crystal structure transformation during the solvothermal reaction process. After high-temperature calcination, the diffraction peaks at 31.15°, 36.39°, 44.24°, 59.09° and 64.98° in the CA-CoNiMn-CLDHs spectrum corresponded to the (220), (311), (400), (511) and (440) crystal planes of NiCo2O4 (PDF#20-0781), respectively. The diffraction peaks at 30.54°, 35.99°, 43.76°, 57.91° and 63.62° corresponded to the (220), (311), (400), (511) and (440) crystal planes of MnCo2O4 (PDF#23-1237), respectively. The changes in these diffraction peaks confirmed the crystal structure transformation during the calcination process and the formation of spinel-phase mixed metal oxides.

[0087] Example Six:

[0088] The activity of the CA-CoNiMn-CLDHs nanozyme in Example 1 was measured. The specific method is as follows:

[0089] 400 μL of TMB ethanol solution (5 mM), 300 μL of CA-CoNiMn-CLDHs suspension (0.5 mg / mL), and 300 μL of H2O2 (0.1 M) were added successively to 2 mL of NaAc-HAc buffer solution (0.2 M, pH 4.0). The total reaction volume was 3 mL. After mixing evenly, it was incubated at room temperature for 20 min, and the absorbance value of the reaction system at 652 nm was measured using a UV-visible spectrophotometer.

[0090] 1.80 mg of isopropanol, 0.54 mg of p-benzoquinone, and 0.59 mg of NaN3 were accurately weighed and added to centrifuge tubes containing 2 mL of NaAc-HAc buffer solution (0.2 M, pH 4.0). 400 μL of TMB ethanol solution (5 mM), 300 μL of CA-CoNiMn-CLDHs suspension (0.5 mg / mL), and 300 μL of H2O2 (0.1 M) were added to each centrifuge tube in turn. It was incubated at room temperature for 20 min, and the absorbance value of the reaction system at 652 nm was measured using a UV-visible spectrophotometer.

[0091] Figure 5The UV-visible absorption spectra of different color development systems with TMB as the color development substrate. As can be seen from Figure (a), there is no obvious color change in the TMB and TMB+H2O2 reaction systems, and there is no obvious absorption peak at 652 nm. However, after adding CoNi-CLDHs, CoMn-CLDHs and CoNiMn-CLDHs to the TMB+H2O2 reaction system, the colorless TMB is transformed into blue oxTMB, and an obvious absorption peak appears at 652 nm, indicating that the catalyst has peroxidase-like activity. It is worth noting that the absorption peak intensity of the CoNiMn-CLDHs+TMB+H2O2 reaction system at 652nm is significantly enhanced, and is significantly higher than other reaction systems under the same conditions, indicating that the modification of CA enhances the peroxidase-like activity of CA-CoNiMn-CLDHs. Figure 3 (b) is the UV-visible absorption spectrum of the color system after adding different free radical scavengers. It can be seen from the figure that the addition of isopropyl alcohol (IPA) inhibits the color change of the color system and significantly reduces the absorbance of the reaction system at 652 nm. IPA is a scavenger of •OH, indicating that •OH plays a major role in the color reaction. When p-benzoquinone (BQ) is added to the color system, the absorption peak intensity at 652 nm also shows a downward trend, indicating that a small amount of O2 is generated in the reaction system. •- After adding NaN3, the absorbance of the reaction system did not decrease significantly, indicating that no 1 O2. Therefore, the main active species in the color development system is •OH, which further confirms that CA-CoNiMn-CLDHs has excellent peroxidase-like activity.

[0092] Embodiment seven:

[0093] Based on the CA-CoNiMn-CLDHs nanozyme in Example 1, phenol colorimetric detection is performed, and the specific method is shown in the following specific steps:

[0094] Phenol solutions of different concentrations (1-100 μM) were prepared (the curve is from bottom to top, and the samples correspond to 1 μM, 3 μM, 5 μM, 7 μM, 10 μM, 30 μM, 50 μM, 70 μM, and 100 μM phenol solutions from left to right), and 700 μL of 4-AAP, 150 μL of H2O2 (50 mM M), 150 μL of CA-CoNiMn-CLDHs suspension (0.5 mg / mL) and 900 μL of phenol solutions of different concentrations were added to 1.1 mL of NaAc-HAc buffer solution (0.2 M, pH 4.0) in sequence. The total reaction volume was 3 mL, and the mixture was incubated at room temperature for 20 min. The absorbance of the reaction system at 525 nm was measured using a UV-visible spectrophotometer.

[0095] Figure 6 are the UV-visible absorption spectra and linear relationship diagrams of the colorimetric detection of phenol by CA-CoNiMn-CLDHs nanozyme. It can be seen from the figure that in the range of 1-100 μM, as the concentration of phenol increases, the absorbance at 525 nm gradually increases (Figure a), the color of the solution changes from colorless to pink, and there is a good linear relationship between the phenol concentration and the absorbance (R 2 = 0.99158). According to the 3σ rule (3σ / slope), the detection limit of phenol was calculated to be 0.163 μM (Figure b).

[0096] Although the present disclosure is disclosed as above, the protection scope of the present disclosure is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present disclosure, and these changes and modifications will all fall within the protection scope of the present invention.

Claims

1. A preparation method of MOF-derived three-dimensional CA-CoNiMn-CLDHs nanozyme, characterized in that, It includes the following steps: Step S1: Dissolve Co(NO3)2•6H2O and 2-methylimidazole in methanol respectively to prepare ZIF-67; Step S2: Disperse ZIF-67 in a mixed solvent composed of N,N-dimethylformamide and ethanol, and stir evenly at room temperature to form solution A; Step S3: Add Ni(NO3)2•6H2O and MnCl2•4H2O to distilled water in sequence, and stir magnetically evenly to form solution B; Step S4: Quickly add solution B to solution A, stir evenly, and carry out hydrothermal reaction in a reaction kettle to form CoNiMn-LDHs; Step S5: Place CoNiMn-LDHs in a tubular furnace for high-temperature calcination to form CoNiMn-CLDHs, and successfully prepare CA-CoNiMn-CLDHs after being modified by citric acid.

2. The preparation method of the CA-CoNiMn-CLDHs nanozyme according to claim 1, wherein In step S1, the mass range of Co(NO3)2•6H2O is 500-600 mg, the mass range of 2-methylimidazole is 600-700 mg, the volume of methanol is 40-80 mL, the reaction temperature is room temperature, and the reaction time is 12-40 h.

3. The preparation method of the CA-CoNiMn-CLDHs nanozyme according to claim 1, wherein In step S2, the mass of ZIF-67 is 80-100 mg, the volume of N,N-dimethylformamide is 20-50 mL, and the volume of ethanol is 20-50 mL.

4. The preparation method of CA-CoNiMn-CLDHs nanozyme according to claim 1, wherein, In step S3, the mass ratio of Ni(NO3)2•6H2O to MnCl2•4H2O is 1:1, and the volume of distilled water is 5-20 mL.

5. The preparation method of CA-CoNiMn-CLDHs nanozyme according to claim 1, characterized in that, In step S4, the hydrothermal reaction temperature is 90-120 °C, and the reaction time is 1-3 h.

6. The preparation method of CA-CoNiMn-CLDHs nanozyme according to claim 1, characterized in that, In step S5, the calcination temperature is 350-500 °C, the calcination time is 1-3 h, the heating rate is 1-5 °C / min, the citric acid concentration is 5-20 mM, the volume of citric acid concentration is 50-100 mL, and the reaction time is 20-90 min.

7. A CA-CoNiMn-CLDHs nanozyme, characterized in that, The CA-CoNiMn-CLDHs nanozyme is prepared by the preparation method described in any one of claims 1-6.

8. The CA-CoNiMn-CLDHs nanozyme according to claim 7, wherein The nanozyme includes CoNiMn-CLDHs and a citric acid modification layer. The CoNiMn-CLDHs is prepared by ion exchange derivation using ZIF-67 as a template, and the citric acid modification layer is fixed on the surface of the CoNiMn-CLDHs through chemical adsorption.

9. Application of the CA-CoNiMn-CLDHs nanozyme described in claim 7 in phenol detection.

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