Nitrogen-doped MOF-derived hollow porous carbon-rare earth metal doped MnO2-graphene aerogel composite material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of air purification, and discloses a nitrogen-doped MOF derived hollow porous carbon-rare earth metal doped MnO2-graphene aerogel composite material as well as a preparation method and application thereof. The preparation method provided by the invention comprises the following steps: taking a nitrogen-containing organic heterocyclic ligand, a nitrogen doping agent, a non-noble metal salt compound and chitosan, carrying out a first hydrothermal reaction, carrying out tannic acid etching and first calcination treatment, carrying out MnO2 in-situ growth on the obtained nitrogen-doped MOF derived hollow porous carbon material, and introducing a rare earth metal salt compound to obtain the nitrogen-doped MOF derived hollow porous carbon material. And finally, taking the obtained nitrogen-doped MOF derived hollow porous carbon-rare earth metal doped MnO2 composite material, graphene oxide and a reducing agent to carry out second hydrothermal reaction, ethanol soaking, freezing and freeze-drying treatment to obtain the nitrogen-doped MOF derived hollow porous carbon-rare earth metal doped MnO2 composite material. The nitrogen-doped MOF-derived hollow porous carbon-rare earth metal doped MnO2-graphene aerogel composite material has excellent adsorption and catalytic degradation activity on TVOC (Total Volatile Organic Compounds) such as formaldehyde and the like, and the composite material has a good application prospect in air purification.

Description

Technical Field

[0001] The present invention belongs to the technical field of air purification, and in particular relates to a nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material, a preparation method and an application thereof. Background Art

[0002] At present, existing indoor air purification methods mainly include ventilation, biological purification, adsorption, etc. However, the above methods have disadvantages such as poor effect, high time cost and possible secondary pollution, and have great limitations.

[0003] In recent years, catalytic oxidation technology has become well-known, and more researchers have applied it to air purification. Catalysts used for the catalytic oxidation of volatile organic gases are mainly divided into two types: precious metal-based catalysts and non-precious metal-based catalysts. Among them, precious metal-based catalysts refer to a type of catalyst with precious metal elements such as platinum, palladium, rhodium, iridium, ruthenium, osmium and their compounds as the main active ingredients, but they have disadvantages such as high prices and easy poisoning. Non-precious metal-based catalysts refer to catalysts with non-precious metal elements such as iron, cobalt, nickel, copper, manganese and their compounds as the main active ingredients. Compared with precious metal catalysts, they have advantages such as low cost and abundant resources, and have received more attention. However, non-precious metal-based catalysts have problems such as low catalytic activity, weak adsorption capacity of volatile organic gases, and the need for additional external energy for the catalytic reaction.

[0004] Therefore, obtaining a catalyst that has both excellent adsorption capacity and catalytic activity for volatile organic gases such as formaldehyde and benzene series is of great significance for achieving the purification of indoor air pollution. Summary of the Invention

[0005] The first purpose of the present invention is to obtain a catalyst that has excellent adsorption capacity and catalytic degradation activity for volatile organic gases such as formaldehyde and benzene series, and to provide a method for preparing a nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material.

[0006] The second object of the present invention is to provide a nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material prepared by the above preparation method.

[0007] The third object of the present invention is to provide an application of the above-mentioned nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material in air purification.

[0008] Specifically, the preparation method of the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material provided by the present invention specifically includes: S1, taking a nitrogen-containing organic heterocyclic ligand, a nitrogen dopant, a non-noble metal salt compound and chitosan, performing a first hydrothermal reaction to obtain a first hydrothermal reaction product, taking the first hydrothermal reaction product and mixing it with a tannic acid solution, performing an etching treatment to obtain an etching product, and taking the etching product and performing a first calcination treatment to obtain a nitrogen-doped MOF-derived hollow porous carbon material; S2, taking the nitrogen-doped MOF-derived hollow porous carbon material, manganese nitrate and a rare earth metal salt compound, mixing them, and performing a calcination treatment on the etching product to obtain a nitrogen-doped MOF-derived hollow porous carbon material; Slowly add potassium permanganate solution under strong stirring to carry out precipitation reaction to obtain a precipitation product, and take the precipitation product for a second calcination treatment to obtain a nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2 composite material; S3, take the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2 composite material, graphene oxide and a reducing agent, mix them, and carry out a second hydrothermal reaction to obtain a second hydrothermal reaction product, and take the second hydrothermal reaction product for ethanol solution immersion treatment, freezing treatment and freeze-drying treatment to obtain the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material.

[0009] Furthermore, in step S1, the nitrogen-containing organic heterocyclic ligand includes one or more of imidazoles and their derivatives, pyridines and their derivatives, and triazoles and their derivatives.

[0010] Furthermore, in step S1, the imidazoles and their derivatives are selected from one or more of imidazole, 2-methylimidazole, 4-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, benzimidazole and 2-mercaptoimidazole.

[0011] Furthermore, in step S1, the pyridine and its derivatives are selected from one or more of 2-methylpyridine, 2,6-dimethylpyridine, 2-hydroxy-6-methylpyridine, 2-chloro-5-trifluoromethylpyridine and quinoline.

[0012] Furthermore, in step S1, the triazoles and their derivatives are selected from one or more of 1,2,3-triazole, 1,2,4-triazole, 1,4-diphenyl-1,2,3-triazole and 2-mercapto-1,2,4-triazole.

[0013] Furthermore, in step S1, the nitrogen dopant includes one or more of urea, cyanamide compounds and ammonium salts.

[0014] Furthermore, in step S1, the cyanamide compound is selected from one or more of cyanamide, cyanuramide, dicyandiamide and melamine.

[0015] Furthermore, in step S1, the ammonium salt is selected from one or more of ammonium chloride, ammonium sulfate, ammonium nitrate and ammonium bicarbonate.

[0016] Furthermore, in step S1, the non-noble metal salt compound is selected from one or more of zinc salts, copper salts, iron salts, cobalt salts, nickel salts, manganese salts and magnesium salts.

[0017] Furthermore, in step S1, the chitosan has a deacetylation degree of not less than 95% and a weight average molecular weight of 50,000-60,000.

[0018] Furthermore, in step S1, the added mass ratio of the nitrogen-containing organic heterocyclic ligand, the nitrogen dopant, the metal salt compound and the chitosan is (0.1-200):(0.1-200):(0.1-200):(0.5-3).

[0019] Furthermore, in step S1, in the solution system of the first hydrothermal reaction, the total added concentration of the nitrogen-containing organic heterocyclic ligand, the nitrogen dopant, the non-noble metal salt compound and chitosan is 0.01 wt% to 50 wt%.

[0020] Furthermore, in step S1, acetic acid is added to the first hydrothermal reaction, and the added concentration of the acetic acid is 0.03% (v / v) to 6% (v / v).

[0021] Furthermore, in step S1, the temperature of the first hydrothermal reaction is 80° C. to 180° C., and the time is 2 h to 10 h.

[0022] Furthermore, in step S1, the concentration of the tannic acid solution is 1 g / L to 10 g / L.

[0023] Furthermore, in step S1, the mixing ratio of the first hydrothermal reaction product and the tannic acid solution is (0.1-1) g: (10-100) mL.

[0024] Furthermore, in step S1, the etching process is performed at a temperature of 10°C to 40°C, a rotation speed of 100 rpm to 300 rpm, and a time of 5 to 60 min.

[0025] Furthermore, in step S1, the atmosphere of the first calcination treatment is nitrogen, the nitrogen flow rate is 50 mL / min to 100 mL / min, the heating rate is 3°C / min to 10°C / min, the holding temperature is 500°C to 1000°C, and the holding time is 1 h to 5 h.

[0026] Furthermore, in step S2, the rare earth metal salt compound includes one or more of yttrium salt, lanthanum salt, cerium salt and samarium salt.

[0027] Furthermore, in step S2, the added mass ratio of the nitrogen-doped MOF-derived hollow porous carbon material, manganese nitrate, rare earth metal salt compound and potassium permanganate is (1-10):(2.5-15):(0.5-5):(1-5).

[0028] Furthermore, in step S2, in the solution system of the precipitation reaction, the total added concentration of the nitrogen-doped MOF-derived hollow porous carbon material, manganese nitrate, rare earth metal salt compound and potassium permanganate is 1 wt% to 25 wt%.

[0029] Furthermore, in step S2, the stirring speed of the vigorous stirring is 200 r / min to 500 r / min, and the dropping speed of the potassium permanganate solution is 1 mL / min to 2 mL / min.

[0030] Furthermore, in step S2, the precipitation reaction temperature is 10°C to 40°C, and the time is 1h to 6h.

[0031] Furthermore, in step S2, the atmosphere of the second calcination treatment is air, the heating rate is 3°C / min to 10°C / min, the holding temperature is 300°C to 800°C, and the holding time is 3h to 8h.

[0032] Furthermore, in step S3, the oxidation degree of the graphene oxide is 10% to 50%, the thickness of the flakes is 0.1 nm to 3 nm, and the particle size is 50 μm to 300 μm.

[0033] Furthermore, in step S3, the reducing agent includes one or more of ascorbic acid, ethylenediamine, hydrazine, hydroiodic acid, sodium borohydride and ammonia.

[0034] Furthermore, in step S3, the added mass ratio of the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2 composite material, graphene oxide and reducing agent is (1-5):(0.5-3):(0.25-6).

[0035] Furthermore, in step S3, in the solution system of the second hydrothermal reaction, the total added concentration of the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2 composite material, graphene oxide and reducing agent is 0.4wt% to 10wt%.

[0036] Furthermore, in step S3, the temperature of the second hydrothermal reaction is 60° C. to 120° C., and the time is 2 h to 10 h.

[0037] Furthermore, in step S3, during the ethanol solution soaking treatment, the concentration of the ethanol solution is 5% (v / v) to 30% (v / v).

[0038] Furthermore, in step S3, the mixing ratio of the second hydrothermal reaction product and the ethanol solution is (1-10))g:(100-1000)mL.

[0039] Furthermore, in step S3, the soaking treatment is performed at a temperature of 10° C. to 40° C. and for a time of 12 hours to 48 hours.

[0040] Furthermore, in step S3, the freezing treatment temperature is -80°C to -15°C, and the time is 5h to 24h.

[0041] Furthermore, in step S3, the freeze-drying treatment is performed at a temperature of -80°C to -60°C, a pressure of 1 Pa to 10 Pa, and a time of 12 hours to 72 hours.

[0042] The nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material provided by the present invention is prepared by the above-mentioned preparation method of the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material.

[0043] Furthermore, the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material has a multi-porous structure, and the multi-porous structure is formed by stacking circular cluster structures.

[0044] Furthermore, the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material is loaded with 0.5 wt% to 1 wt% of rare earth metal elements.

[0045] The present invention also provides the use of the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material in air purification.

[0046] Beneficial effects:

[0047] In the preparation method of the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material provided by the present invention, a nitrogen-containing organic heterocyclic ligand and a non-noble metal salt compound are first used as raw materials, and a nitrogen dopant and chitosan are simultaneously introduced on this basis to carry out a first hydrothermal reaction to prepare a metal-organic framework material (MOFs), and a first calcination treatment is carried out using the metal-organic framework material (MOFs) etched with tannic acid as a template, and carbonization is carried out to prepare a nitrogen-doped MOF-derived hollow porous carbon material; Then, under conditions of vigorous stirring, rare earth metal salt compounds are introduced at the same time by slowly adding the materials in a coordinated manner, and MnO2 is in situ grown on the nitrogen-doped MOF-derived hollow porous carbon material, so that MnO2 and rare earth metals are carried on the nitrogen-doped MOF-derived hollow porous carbon material, and the composite is used as a template for a second calcination treatment to prepare a nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2 composite material; finally, the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2 composite material is used as a base The method is based on the above-mentioned structure, and graphene oxide and a reducing agent are introduced to carry out a second hydrothermal reaction. The graphene oxide is stably loaded on the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2 composite material through ethanol solution immersion treatment, freezing treatment and freeze-drying treatment. Finally, a nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material is prepared. The composite material has a multi-porous structure formed by the accumulation of circular cluster structures, and is stably loaded with MnO2, rare earth metals and graphene oxide. It has rich adsorption sites and catalytic active sites, and has excellent adsorption and catalytic degradation capabilities of volatile organic pollutants such as formaldehyde in the air. The formaldehyde removal rate is as high as 99.1%, and the total volatile organic pollutant removal rate is as high as 97.2%. It can achieve thorough treatment of volatile organic pollutants in the air, and the composite material has excellent stability. After repeated use, it can still maintain excellent adsorption and catalytic degradation capabilities of volatile organic pollutants such as formaldehyde in the air, and has good application prospects in air purification.

[0048] It is speculated that the reasons why the preparation method has the above technical effects include: first, in the preparation of nitrogen-doped MOF-derived hollow porous carbon materials, a nitrogen-containing organic heterocyclic ligand containing heteroatom N is used as an organic ligand, and chitosan is introduced as a secondary carbon source and nitrogen source in addition to the nitrogen dopant, so that the nitrogen element can be doped into MOFs in a more uniform and stable state, while also improving the orderliness of the pore structure and reducing the collapse of the structure in subsequent treatments, and combined with tannic acid etching, the nitrogen-doped MOF-derived hollow porous carbon material has an ideal three-dimensional spatial structure and rich metal loading sites, which is conducive to the loading of manganese and rare earth metal elements; second, the rare earth metal salt compound is introduced while slowly adding the corresponding feeding method under vigorous stirring conditions, which can well realize the growth of MnO2 in the nitrogen-doped MOF-derived hollow porous carbon material and the doping of rare earth metals on the nitrogen-doped MOF-derived hollow porous carbon material and MnO2, and the second calcination treatment is performed to further improve the MnO2 and nitrogen-doped MOF-derived hollow porous carbon. The bonding stability between the materials is improved and the heterogeneous interface between the two is strengthened, and the doped nitrogen elements, MnO2 and rare earth metals cooperate to form rich graphene oxide bonding and carrying sites in the structure of the composite material; thirdly, through the introduction of nitrogen doping atoms, MnO2 and rare earth metals, the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2 composite material has excellent reactivity with graphene oxide, so that the composite material can better combine with graphene oxide to obtain a multi-porous structure formed by the accumulation of circular cluster structures. In this structure, a variety of materials are combined to produce an interface hybridization effect, increase the distortion energy of the lattice and increase the electron density on the surface of the material, promote surface oxygen activity, and form more adsorption and catalytic active sites while also improving the bonding stability between the materials, so as to give the final nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material excellent adsorption, catalytic degradation of volatile organic pollutants such as formaldehyde and performance stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 One of the SEM images of the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material provided in Example 1 of the present invention (scale: 50 μm);

[0050] Figure 2 This is the second SEM image of the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material provided in Example 1 of the present invention (scale is 500 nm). DETAILED DESCRIPTION

[0051] The preparation method of the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material provided by the present invention specifically comprises the following steps: S1, mixing a nitrogen-containing organic heterocyclic ligand, a nitrogen dopant, a non-precious metal salt compound and chitosan, performing a first hydrothermal reaction to obtain a first hydrothermal reaction product, mixing the first hydrothermal reaction product with a tannic acid solution, performing an etching treatment to obtain an etching product, and performing a first calcination treatment on the etching product to obtain a nitrogen-doped MOF-derived hollow porous carbon material; S2, mixing the nitrogen-doped MOF-derived hollow porous carbon material, manganese nitrate and a rare earth metal salt compound, and stirring vigorously. Slowly add potassium permanganate solution under stirring conditions to carry out precipitation reaction to obtain a precipitation product, and take the precipitation product for a second calcination treatment to obtain a nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2 composite material; S3, take the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2 composite material, graphene oxide and a reducing agent, mix them, and carry out a second hydrothermal reaction to obtain a second hydrothermal reaction product, and take the second hydrothermal reaction product for ethanol solution immersion treatment, freezing treatment and freeze-drying treatment to obtain the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material.

[0052] In the present invention, in step S1, the nitrogen-containing organic heterocyclic ligand refers to a class of organic compounds having a nitrogen-containing heterocyclic ring in the structure, which can be used as a ligand to form a coordination bond with a metal ion. Specific examples of the nitrogen-containing organic heterocyclic ligand include, but are not limited to, one or more of imidazoles and their derivatives, pyridines and their derivatives, and triazoles and their derivatives. Among them, the imidazoles and their derivatives refer to a class of organic compounds having an imidazole ring structure in the structure, and specific examples thereof include, but are not limited to, one or more of imidazole, 2-methylimidazole, 4-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, benzimidazole, and 2-mercaptoimidazole. The pyridines and their derivatives refer to a class of organic compounds having a pyridine ring structure in the structure, and specific examples thereof include, but are not limited to, one or more of 2-methylpyridine, 2,6-dimethylpyridine, 2-hydroxy-6-methylpyridine, 2-chloro-5-trifluoromethylpyridine, and quinoline. The triazoles and their derivatives refer to a class of organic compounds having a triazole ring structure, and specific examples thereof include but are not limited to: one or more of 1,2,3-triazole, 1,2,4-triazole, 1,4-diphenyl-1,2,3-triazole and 2-mercapto-1,2,4-triazole.

[0053] In the present invention, in step S1, the nitrogen dopant refers to a class of nitrogen-containing organic substances introduced into the MOF preparation process to achieve nitrogen doping, in addition to the nitrogen-containing organic heterocyclic ligand and chitosan. Specific examples of the nitrogen dopant include, but are not limited to, one or more of urea, cyanamide compounds, and ammonium salts. The cyanamide compound refers to a class of organic compounds containing a cyanamide group or a functional group derived therefrom in its structure, and specific examples thereof include, but are not limited to, one or more of cyanamide, cyanuramide, dicyandiamide, and melamine. The ammonium salt refers to a class of ionic compounds formed by the ionic bonding of ammonium ions and acid ions, and specific examples thereof include, but are not limited to, one or more of ammonium chloride, ammonium sulfate, ammonium nitrate, and ammonium bicarbonate.

[0054] In the present invention, in step S1, the non-precious metal salt compound refers to an ionic compound formed by cations formed from non-precious metal elements and acid ions through ionic bonding. Specific examples include, but are not limited to, one or more of zinc salts, copper salts, iron salts, cobalt salts, nickel salts, manganese salts, and magnesium salts. In some specific embodiments, the non-precious metal salt compound is preferably a zinc salt; in this case, the zinc atoms volatilize during the first calcination treatment, which facilitates the formation of a more ideal hollow porous structure.

[0055] In the present invention, in step S1, the chitosan refers to the product obtained by deacetylation of chitin, and its structure contains D-glucosamine and N-acetyl-D-glucosamine, which are introduced as secondary carbon sources and nitrogen sources in the preparation of nitrogen-doped MOF-derived hollow porous carbon materials.

[0056] In some specific embodiments, the degree of deacetylation of the chitosan is preferably not less than 95%, specifically 95%, 96%, 97%, 98%, 99%, 99.9999%, 100%, or any value therebetween; the weight-average molecular weight is preferably 50,000-60,000, specifically 50,000, 51,000, 52,000, 53,000, 55,000, 57,000, 60,000, or any value therebetween. This further optimizes the nitrogen doping state in the hollow porous carbon material, facilitating the preparation of nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composites with superior adsorption and catalytic degradation properties.

[0057] In the present invention, in step S1, the added mass ratio of the nitrogen-containing organic heterocyclic ligand, the nitrogen dopant, the metal salt compound and the chitosan is preferably (0.1-200):(0.1-200):(0.1-200):(0.5-3), specifically 0.1:0.1:0.1:0.5, 0.5:0.5:1:1, 10:1:1:1, 50:80:100:2.3, 100:100:1:1, 200:200:200:3 or any value therebetween.

[0058] In some preferred embodiments, in the solution system of the first hydrothermal reaction, the total added concentration of the nitrogen-containing organic heterocyclic ligand, nitrogen dopant, non-precious metal salt compound and chitosan is preferably 0.01wt% to 50wt%, specifically 0.01wt%, 0.05wt%, 0.07wt%, 0.1wt%, 0.5wt%, 1wt%, 3wt%, 8wt%, 10wt%, 15wt%, 20wt%, 35wt%, 40wt%, 45wt%, 50wt% or any value therebetween.

[0059] In the present invention, in step S1, acetic acid is added to the first hydrothermal reaction, and the concentration of the acetic acid is preferably 0.03% (v / v) to 6% (v / v), specifically 0.03% (v / v), 0.05% (v / v), 0.08% (v / v), 0.1% (v / v), 0.25% (v / v), 0.5% (v / v), 0.8% (v / v), 1% (v / v), 1.2% (v / v), 2% (v / v), 3% (v / v), 5% (v / v), 6% (v / v), or any value therebetween. At this time, the introduction of the acetic acid can adjust the coordination rate to improve the orderliness of the structure of the obtained first hydrothermal reaction product.

[0060] In the present invention, in step S1, the conditions of the first hydrothermal reaction include a temperature of preferably 80°C to 180°C, specifically 80°C, 83°C, 82°C, 90°C, 100°C, 120°C, 150°C, 160°C, 180°C or any value therebetween; and a time of preferably 2h to 10h, specifically 2h, 2.5h, 2.8h, 3h, 3.5h, 4h, 5h, 7.5h, 9h, 10h or any value therebetween.

[0061] In the present invention, in step S1, the present invention does not impose any particular limitation on the mixing order and mixing method of the nitrogen-containing organic heterocyclic ligand, nitrogen dopant, non-precious metal salt compound and chitosan, that is, the mixing method of the nitrogen-containing organic heterocyclic ligand, nitrogen dopant, non-precious metal salt compound and chitosan is not limited to the method described in the following embodiments.

[0062] In the present invention, in step S1, the concentration of the tannic acid solution is preferably 1 g / L to 10 g / L, and specifically can be 1 g / L, 1.5 g / L, 2 g / L, 4 g / L, 6 g / L, 8 g / L, 10 g / L, or any value therebetween. In this case, the tannic acid solution has a better etching effect on the first hydrothermal reaction product.

[0063] In the present invention, in step S1, the mixing ratio of the first hydrothermal reaction product and the tannic acid solution is preferably (0.1-1) g:(10-100) mL, specifically 0.1 g:10 mL, 0.2 g:20 mL, 0.2 g:30 mL, 0.5 g:50 mL, 0.8 g:80 mL, 0.9 g:90 mL, 1 g:100 mL, or any value therebetween. In this case, the tannic acid solution has a better etching effect on the first hydrothermal reaction product.

[0064] In the present invention, in step S1, the conditions of the etching treatment include a temperature of preferably 10°C to 40°C, specifically 10°C, 13°C, 15°C, 18°C, 20°C, 25°C, 30°C, 35°C, 40°C or any value therebetween; a rotation speed of preferably 100r / min to 300r / min, specifically 100r / min, 110r / min, 120r / min, 150r / min, 170r / min, 200r / min, 250r / min, 300r / min or any value therebetween; and a time of preferably 5 to 60min, specifically 5min, 8min, 10min, 15min, 20min, 25min, 30min, 40min, 50min, 60min or any value therebetween.

[0065] In the present invention, in step S1, the conditions of the first calcination treatment include that the atmosphere is preferably nitrogen, and the nitrogen flow rate is preferably 50 mL / min to 100 mL / min, specifically 50 mL / min, 55 mL / min, 60 mL / min, 78 mL / min, 90 mL / min, 100 mL / min or any value therebetween; the heating rate is preferably 3°C / min to 10°C / min, specifically 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, 10°C / min or any value therebetween; the holding temperature is preferably 500°C to 1000°C, specifically 500°C, 520°C, 560°C, 600°C, 700°C, 800°C, 1000°C or any value therebetween; and the holding time is preferably 1 h to 5 h, specifically 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 4 h, 5 h or any value therebetween.

[0066] In the present invention, in step S2, the rare earth metal salt compound refers to a type of ionic compound formed by cations formed by non-precious metal elements and acid radical ions through ionic bonding, and specific examples thereof include but are not limited to: one or more of yttrium salts, lanthanum salts, cerium salts and samarium salts.

[0067] In the present invention, in step S2, the added mass ratio of the nitrogen-doped MOF-derived hollow porous carbon material, manganese nitrate, rare earth metal salt compound and potassium permanganate is preferably (1-10):(2.5-15):(0.5-5):(1-5), specifically 1:2.5:0.5:1, 2:3:1:1, 4:3:2:1, 8:10:5:5, 10:15:5:5 or any value therebetween.

[0068] In the present invention, in step S2, in the solution system of the precipitation reaction, the total added concentration of the nitrogen-doped MOF-derived hollow porous carbon material, manganese nitrate, rare earth metal salt compound and potassium permanganate is preferably 1 wt% to 25 wt%, and specifically can be 1 wt%, 1.5 wt%, 2 wt%, 4 wt%, 8 wt%, 10 wt%, 12 wt%, 16 wt%, 18 wt%, 20 wt%, 22 wt%, 25 wt% or any value therebetween. At this time, the reaction solution system contains the reaction raw materials at an appropriate concentration, which is conducive to the in-situ growth of MnO2 in the nitrogen-doped MOF-derived hollow porous carbon material and the doping of rare earth metal elements.

[0069] In the present invention, in step S2, the stirring speed of the vigorous stirring is preferably 200r / min to 500r / min, specifically 200r / min, 220r / min, 250r / min, 300r / min, 350r / min, 400r / min, 500r / min or any value therebetween; the dropping acceleration of the potassium permanganate solution is preferably 1mL / min to 2mL / min, specifically 1mL / min, 1.1mL / min, 1.3mL / min, 1.5mL / min, 1.8mL / min, 2mL / min or any value therebetween.

[0070] In the present invention, in step S2, the conditions of the precipitation reaction include a temperature preferably of 10°C to 40°C, specifically 10°C, 12°C, 15°C, 18°C, 20°C, 22°C, 25°C, 28°C, 30°C, 35°C, 40°C or any value therebetween; and a time preferably of 1h to 6h, specifically 1h, 1.5h, 1.8h, 2h, 3h, 4.5h, 5h, 6h or any value therebetween. At this time, it is conducive to the continued growth of MnO2 on the nitrogen-doped MOF-derived hollow porous carbon material, so that the obtained nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2 composite material has a more ideal structure.

[0071] In the present invention, in step S2, the conditions of the second calcination treatment include that the atmosphere is specifically air, the heating rate is preferably 3°C / min to 10°C / min, specifically 3°C / min, 5°C / min, 7°C / min, 9°C / min, 10°C / min or any value therebetween; the holding temperature is preferably 300°C to 800°C, specifically 300°C, 350°C, 400°C, 500°C, 600°C, 800°C or any value therebetween; the holding time is preferably 3h to 8h, specifically 3h, 4h, 5h, 6h, 7h, 8h or any value therebetween.

[0072] In the present invention, in step S2, the present invention does not impose any particular limitation on the mixing order and mixing method of the nitrogen-doped MOF-derived hollow porous carbon material, manganese nitrate and rare earth metal salt compound, that is, the mixing method of the nitrogen-doped MOF-derived hollow porous carbon material, manganese nitrate and rare earth metal salt compound is not limited to the method described in the following embodiments.

[0073] In the present invention, in step S3, the graphene oxide refers to a complex compound generated after graphene undergoes an oxidation reaction. The oxidation degree of the graphene oxide is preferably 10% to 50%, specifically 10%, 12.5%, 18%, 20%, 25%, 30%, 35%, 40%, 50% or any value therebetween; the sheet thickness is preferably 0.1nm to 3nm, specifically 0.1nm, 0.5nm, 0.8nm, 1nm, 1.5nm, 2nm, 2.3nm, 2.8nm, 3nm or any value therebetween; the particle size is preferably 50μm to 300μm, specifically 50μm, 80μm, 100μm, 120μm, 140μm, 180μm, 200μm, 250μm, 300μm or any value therebetween.

[0074] In the present invention, in step S3, the reducing agent refers to a class of chemical substances used to donate electrons to other substances in a chemical reaction. Specific examples of the reducing agent include but are not limited to: one or more of ascorbic acid, ethylenediamine, hydrazine, hydroiodic acid, sodium borohydride and ammonia.

[0075] In the present invention, in step S3, the added mass ratio of the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2 composite material, graphene oxide and reducing agent is preferably (1-5):(0.5-3):(0.25-6), specifically 1:0.5:0.25, 1:0.7:1, 2:0.5:0.6, 2.5:3:1, 5:3:6 or any value therebetween.

[0076] In the present invention, in step S3, the total added concentration of the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2 composite material, graphene oxide, and reducing agent is preferably 0.4 wt% to 10 wt%, and specifically can be 0.4 wt%, 0.8 wt%, 1 wt%, 1.5 wt%, 2 wt%, 4 wt%, 6 wt%, 8 wt%, 10 wt%, or any value therebetween. In this case, it is beneficial to achieve sufficient contact between the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2 composite material, graphene oxide, and reducing agent, thereby achieving better bonding and loading effects.

[0077] In the present invention, in step S3, the conditions of the second hydrothermal reaction include a temperature of preferably 60°C to 120°C, specifically 60°C, 63°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 100°C, 110°C, 120°C or any value therebetween; and a time of preferably 2h to 10h, specifically 2h, 2.5h, 3h, 4h, 5h, 8h, 10h or any value therebetween.

[0078] In the present invention, in step S3, the present invention does not limit the mixing order and mixing method of the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2 composite material, graphene oxide and reducing agent, that is, the mixing method of the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2 composite material, graphene oxide and reducing agent is not limited to the method described in the following embodiments.

[0079] In the present invention, in step S3, during the ethanol solution immersion treatment, the concentration of the ethanol solution is preferably 5% (v / v) to 30% (v / v), specifically 5% (v / v), 8% (v / v), 10% (v / v), 12% (v / v), 15% (v / v), 18% (v / v), 20% (v / v), 25% (v / v), 30% (v / v), or any value therebetween. At this point, the ethanol solution can further optimize the surface state of the second hydrothermal reaction product and enhance the interfacial interaction between the materials to further improve the structural stability.

[0080] In the present invention, in step S3, the mixing ratio of the second hydrothermal reaction product and the ethanol solution is preferably (1-10) g:(100-1000) mL, specifically 1 g:100 mL, 1 g:200 mL, 1 g:300 mL, 2 g:200 mL, 3 g:300 mL, 4 g:400 mL, 5 g:500 mL, 7 g:700 mL, 8 g:800 mL, 10 g:1000 mL or any value therebetween.

[0081] In the present invention, in step S3, the conditions for the immersion treatment include a temperature preferably of 10°C to 40°C, specifically 10°C, 12°C, 15°C, 18°C, 20°C, 25°C, 28°C, 30°C, 35°C, 40°C or any value therebetween; and a time preferably of 12h to 48h, specifically 12h, 14h, 16h, 20h, 25h, 28h, 30h, 36h, 48h or any value therebetween.

[0082] In the present invention, the conditions for the freezing treatment include a temperature preferably of -80°C to -15°C, specifically -80°C, -75°C, -60°C, -45°C, -30°C, -15°C or any value therebetween; a time preferably of 5h to 24h, specifically 5h, 8h, 10h, 12h, 16h, 18h, 20h, 24h or any value therebetween.

[0083] The present invention also provides a nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material prepared by the above preparation method. The composite material has a multi-porous structure, and the multi-porous structure is formed by stacking circular cluster structures.

[0084] In the present invention, the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material is preferably loaded with 0.5 wt% to 1 wt% of rare earth metal elements.

[0085] The present invention also provides the use of the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material in air purification.

[0086] The embodiments of the present invention are described in detail below. The examples of the embodiments are intended to explain the present invention and are not to be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this area or according to the product specifications. Reagents or instruments used that do not specify the manufacturer are all conventional products that can be obtained commercially.

[0087] Example 1

[0088] This example is used to illustrate a method for preparing a nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material, which specifically includes:

[0089] S1. Preparation of nitrogen-doped MOF-derived hollow porous carbon materials

[0090] (1) 49.266 g of 2-methylimidazole was added to 1500 mL of deionized water and stirred at 200 r / min for 30 min. Then, 18.018 g of urea was added and stirring was continued for 30 min to obtain solution A.

[0091] (2) 13.761 g of anhydrous zinc acetate was added to 600 mL of deionized water and stirred at 200 rpm for 30 min to obtain solution B.

[0092] (3) 1.4718 g of chitosan (95% deacetylation degree, 50,000 weight-average molecular weight) was added to 900 mL of 1% (v / v) acetic acid solution and stirred at 200 rpm for 4 h to obtain Solution C.

[0093] (4) Mix solution B and solution C, and stir at 200 r / min for 30 min to obtain solution D.

[0094] (5) Under the conditions of stirring speed of 200 r / min and dropping speed of 25 mL / min, liquid A was slowly added dropwise to liquid D. After the addition of liquid A was completed, stirring was continued for 2 h to obtain liquid E.

[0095] (6) Liquid E was added to a reactor and subjected to a first hydrothermal reaction at 120°C for 6 h. The solid was collected by centrifugation and washed three times with deionized water. The washed solid was then dried at 5 Pa and 60°C for 15 h, crushed, and passed through a 200-mesh sieve to obtain 41.021 g of a first hydrothermal reaction product.

[0096] (7) The first hydrothermal reaction product was added to 600 mL of a 5 g / L tannic acid aqueous solution, and etched at room temperature and 200 r / min for 10 min. The solid was collected by centrifugation and washed three times with deionized water. The washed solid was then dried at 5 Pa and 60° C. for 15 h to obtain an etching reaction product.

[0097] (8) The etching reaction product was added to a muffle furnace and subjected to a first calcination treatment in a nitrogen atmosphere to obtain 27.352 g of a calcined product; wherein the calcination treatment conditions include: a nitrogen flow rate of 50 mL / min, a heating rate of 5°C / min, and calcination at 800°C for 3 h.

[0098] (9) The calcined product was added to 200 mL of 2 mol / L sulfuric acid solution, stirred at 200 r / min for 30 min, and then dried at 5 Pa and 60 °C for 15 h. The product was crushed and passed through a 200-mesh sieve to obtain a nitrogen-doped MOF-derived hollow porous carbon material.

[0099] S2. Preparation of nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2 composites

[0100] (1) Add 2.528 g of potassium permanganate to 60 mL of deionized water and stir at 200 rpm for 30 min to obtain solution A.

[0101] (2) 11.2 mL of a 50 wt% manganese nitrate solution was added to 160 mL of deionized water, and the mixture was stirred at 200 rpm for 30 min. Subsequently, 0.8684 g of cerium nitrate hexahydrate and 0.8889 g of samarium nitrate hexahydrate were added, and the mixture was stirred at 200 rpm for 30 min to obtain Solution B.

[0102] (3) 3.4476 g of nitrogen-doped MOF-derived hollow porous carbon material was added to solution B, and stirred at room temperature and 200 r / min for 2 h to generate solution C. Solution C was vigorously stirred at room temperature and 400 r / min, and solution A was slowly added at a drop rate of 1.3 mL / min. After the addition was completed, stirring was continued at 200 r / min to perform precipitation reaction for 4 h to obtain solution D. Solution D was allowed to stand at room temperature for 20 min, the supernatant was removed, the precipitate was filtered and washed until it was neutral and the TDS value was <10, and then dried at 80°C for 17 h until the water content was <5%, to obtain a precipitated product.

[0103] (4) Under the conditions of a heating rate of 5°C / min, a calcination temperature of 400°C and an air atmosphere, the precipitated product was subjected to a second calcination treatment for 5 hours, crushed, and passed through a 200-mesh sieve to obtain a nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2 composite material.

[0104] S3. Preparation of nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composites

[0105] (1) 0.75 g of graphene oxide (Hummers method, oxidation degree 40%, water content 20%, sheet thickness 0.5-1 nm, particle size 175 μm) was mixed with deionized water and fixed to 250 mL. Ultrasonication was performed for 8 h to obtain a graphene oxide dispersion with a concentration of 3 mg / mL.

[0106] (2) 3 g of nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2 composite material was added to the graphene oxide dispersion and ultrasonicated for 8 h. Then, 1 mL of ethylenediamine (the addition ratio of graphene oxide to ethylenediamine was 3 mg:4 μL) was added and stirred at room temperature and 200 r / min for 30 min. Then, a second hydrothermal reaction was carried out at 95 °C for 6 h. The solid was collected and washed three times with deionized water to obtain 3.235 g of the second hydrothermal reaction product.

[0107] (3) 3.235 g of the second hydrothermal reaction product was added to 500 mL of 15% ethanol, soaked for 24 h, and then frozen at -20 ° C for 12 h. Then, freeze-dried at a pressure of <10 Pa and 80 ° C for 24 h to obtain a nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material.

[0108] The prepared nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material was analyzed by scanning electron microscopy and EDS spectrometer. Figure 1 and 2 And shown in Table 1.

[0109] Table 1.

[0110] element Wt% At% C 82.76 86.66 N 0.18 0.16 O 7.27 5.69 Mn 8.65 7.38 La 0.4 0.04 Ce 0.74 0.07

[0111] Depend on Figure 1 and 2 From the results shown, it can be seen that the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material prepared in this embodiment has a complex multi-porous structure typical of aerogels; and, further increasing the magnification, the pore structure of the composite material is formed by the accumulation of circular cluster structures.

[0112] From the results shown in Table 1, it can be seen that the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material prepared in this embodiment effectively presents the various elements introduced during the preparation process, and the weight percentages and atomic percentages of the different elements C, N, O, Mn, La, and Ce are in line with expectations, and the doping effect is excellent.

[0113] Example 2

[0114] This example uses the method provided in Example 1 to prepare a nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material. The difference is that in step (2) of "1. Preparation of nitrogen-doped MOF-derived hollow porous carbon material", 30.3 g of ferric nitrate nonahydrate is used instead of 13.761 g of anhydrous zinc acetate, and other conditions remain the same to obtain a nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material.

[0115] Example 3

[0116] This example uses the method provided in Example 1 to prepare a nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material. The difference is that in step (2) of "S1, preparation of nitrogen-doped MOF-derived hollow porous carbon material", 21.827 g of cobalt nitrate hexahydrate is used instead of 13.761 g of anhydrous zinc acetate, and other conditions remain the same to obtain a nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material.

[0117] Example 4

[0118] This example uses the method provided in Example 1 to prepare a nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material. The difference is that in step (1) of "S1, preparation of nitrogen-doped MOF-derived hollow porous carbon material", 70.884 g of benzimidazole is used instead of 49.266 g of 2-methylimidazole, and other conditions remain the same to obtain a nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material.

[0119] Example 5

[0120] This example uses the method provided in Example 1 to prepare a nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material. The difference is that in step (1) of "S1, preparation of nitrogen-doped MOF-derived hollow porous carbon material", 65.478 g of 2-hydroxy-6-methylpyridine is used instead of 49.266 g of 2-methylimidazole, and other conditions remain the same to obtain a nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material.

[0121] Example 6

[0122] This example adopts the method provided in Example 1 to prepare nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material, except that in step (3) of "S1, preparation of nitrogen-doped MOF-derived hollow porous carbon material", the amount of chitosan added is 0.5 g, and other conditions remain the same to obtain nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material.

[0123] Example 7

[0124] This example adopts the method provided in Example 1 to prepare nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material, except that in step (3) of "S1, preparation of nitrogen-doped MOF-derived hollow porous carbon material", the amount of chitosan added is 3.0 g, and other conditions remain the same to obtain nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material.

[0125] Example 8

[0126] This example adopts the method provided in Example 1 to prepare nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material, except that in step (2) of "S2, preparation of nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2 composite material", 1.532 g of yttrium nitrate hexahydrate is used instead of 0.8684 g of cerium nitrate hexahydrate and 0.8889 g of samarium nitrate hexahydrate, and other conditions remain the same to obtain nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material.

[0127] Example 9

[0128] This example adopts the method provided in Example 1 to prepare nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material, except that, in step (1) of "S3, preparation of nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material", the amount of graphene oxide added is 3 g, and other conditions remain the same, thereby obtaining a nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material.

[0129] Example 10

[0130] This example adopts the method provided in Example 1 to prepare nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material, except that, in step (3) of "S3, preparation of nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material", the immersion treatment time is 12 hours, and other conditions remain the same, thereby obtaining a nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material.

[0131] Comparative Example 1

[0132] This comparative example adopts the method provided in Example 1 to prepare nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material, except that in step (4) of "S1, preparation of nitrogen-doped MOF-derived hollow porous carbon material", an equal volume of 1% (v / v) acetic acid solution is used instead of liquid C, that is, chitosan is not introduced, and other conditions remain consistent to obtain nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material.

[0133] Comparative Example 2

[0134] This comparative example adopts the method provided in Example 1 to prepare nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material, except that, in step (3) of "S1, preparation of nitrogen-doped MOF-derived hollow porous carbon material", an equal mass of glucose is used instead of chitosan, and other conditions remain the same to obtain nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material.

[0135] Comparative Example 3

[0136] This comparative example adopts the method provided in Example 1 to prepare nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material, except that in step (3) of "S3, nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material", an equal volume of deionized water is used instead of 15% ethanol, and other conditions remain the same to obtain nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material.

[0137] Test Case

[0138] This test example is used to illustrate the performance of the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material provided in the above embodiment, and the comparative example is used as a control. The test specifically includes: catalytic degradation stability: the test is repeated 5 times according to the method provided in QB / T 2761-2006 "Determination of purification effect of indoor air purification products", and after each test is completed, the composite material is dried at 80°C and then subjected to ultraviolet irradiation treatment for 6 hours to complete regeneration. The results are shown in Table 2.

[0139] The test conditions specifically include: the cabin volume is 1.5m 3 , room temperature, the initial formaldehyde concentration in the formaldehyde test is 1mg / m 3 , TVOC initial concentration in TVOC test is 6.5mg / m 3 And the test time is 6h.

[0140] Table 2.

[0141]

[0142]

[0143] It can be seen from the results shown in Table 2 that, compared with comparative examples 1 to 3, the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material prepared by the method provided in Examples 1 to 10 of the present invention has excellent adsorption capacity for volatile organic pollutants such as formaldehyde, and the composite material also has excellent ability to catalyze the degradation of volatile organic pollutants to produce carbon dioxide, and can achieve thorough treatment of volatile organic pollutants in the air; moreover, the composite material still maintains excellent adsorption and catalytic degradation performance during repeated use, and the loss of adsorption active sites and catalytic active sites during the recycling process is small. The multi-porous structure formed by the accumulation of circular cluster structures is highly stable, has excellent performance stability, can be used repeatedly, and shows excellent application potential in the purification treatment of volatile organic pollutants such as formaldehyde.

[0144] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and purpose of the present invention.

Claims

1. A method for preparing a nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material, characterized in that: The preparation method comprises: S1. Mixing a nitrogen-containing organic heterocyclic ligand, a nitrogen dopant, a non-noble metal salt compound, and chitosan, performing a first hydrothermal reaction to obtain a first hydrothermal reaction product, mixing the first hydrothermal reaction product with a tannic acid solution, and performing an etching treatment to obtain an etched product, and performing a first calcination treatment on the etched product to obtain a nitrogen-doped MOF-derived hollow porous carbon material; S2. Mixing the nitrogen-doped MOF-derived hollow porous carbon material, manganese nitrate, and a rare earth metal salt compound, slowly adding a potassium permanganate solution dropwise under vigorous stirring to perform a precipitation reaction to obtain a precipitated product, and performing a second calcination treatment on the precipitated product to obtain a nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2 composite material; S3. Take the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2 composite material, graphene oxide and a reducing agent, mix them, and perform a second hydrothermal reaction to obtain a second hydrothermal reaction product. Take the second hydrothermal reaction product and perform an ethanol solution soaking treatment, freezing treatment and freeze-drying treatment to obtain the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material.

2. The method for preparing the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material according to claim 1, characterized in that: In step S1, the nitrogen-containing organic heterocyclic ligand includes one or more of imidazoles and their derivatives, pyridines and their derivatives, and triazoles and their derivatives; Optionally, the imidazoles and their derivatives are selected from one or more of imidazole, 2-methylimidazole, 4-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, benzimidazole and 2-mercaptoimidazole; Optionally, the pyridine and its derivatives are selected from one or more of 2-methylpyridine, 2,6-lutidine, 2-hydroxy-6-methylpyridine, 2-chloro-5-trifluoromethylpyridine and quinoline; Optionally, the triazoles and their derivatives are selected from one or more of 1,2,3-triazole, 1,2,4-triazole, 1,4-diphenyl-1,2,3-triazole and 2-mercapto-1,2,4-triazole; Optionally, the nitrogen dopant includes one or more of urea, cyanamide compounds and ammonium salts; Optionally, the cyanamide compound is selected from one or more of cyanamide, cyanuramide, dicyandiamide and melamine; Optionally, the ammonium salt is selected from one or more of ammonium chloride, ammonium sulfate, ammonium nitrate and ammonium bicarbonate; Optionally, the non-noble metal salt compound is selected from one or more of zinc salts, copper salts, iron salts, cobalt salts, nickel salts, manganese salts and magnesium salts; Optionally, the chitosan has a degree of deacetylation of not less than 95% and a weight average molecular weight of 50,000-60,000; Optionally, the added mass ratio of the nitrogen-containing organic heterocyclic ligand, the nitrogen dopant, the metal salt compound and the chitosan is (0.1-200):(0.1-200):(0.1-200):(0.5-3); Optionally, in the solution system of the first hydrothermal reaction, the total added concentration of the nitrogen-containing organic heterocyclic ligand, the nitrogen dopant, the non-noble metal salt compound and chitosan is 0.01 wt% to 50 wt%; Optionally, acetic acid is added to the first hydrothermal reaction, and the concentration of the acetic acid is 0.03% (v / v) to 6% (v / v); Optionally, the temperature of the first hydrothermal reaction is 80° C. to 180° C., and the time is 2 h to 10 h.

3. The method for preparing the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material according to claim 1, characterized in that: In step S1, the concentration of the tannic acid solution is 1 g / L to 10 g / L; Optionally, the mixing ratio of the first hydrothermal reaction product and the tannic acid solution is (0.1-1) g: (10-100) mL; Optionally, the etching treatment is performed at a temperature of 10° C. to 40° C., a rotation speed of 100 r / min to 300 r / min, and a time of 5 to 60 min.

4. The method for preparing the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material according to claim 1, characterized in that: In step S1, the atmosphere of the first calcination treatment is nitrogen, the nitrogen flow rate is 50 mL / min to 100 mL / min, the heating rate is 3°C / min to 10°C / min, the holding temperature is 500°C to 1000°C, and the holding time is 1 hour to 5 hours.

5. The method for preparing the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material according to claim 1, characterized in that: In step S2, the rare earth metal salt compound includes one or more of yttrium salt, lanthanum salt, cerium salt and samarium salt; Optionally, the added mass ratio of the nitrogen-doped MOF-derived hollow porous carbon material, manganese nitrate, rare earth metal salt compound and potassium permanganate is (1-10):(2.5-15):(0.5-5):(1-5); Optionally, in the solution system of the precipitation reaction, the total added concentration of the nitrogen-doped MOF-derived hollow porous carbon material, manganese nitrate, rare earth metal salt compound and potassium permanganate is 1 wt% to 25 wt%; Optionally, the stirring speed of the vigorous stirring is 200 r / min to 500 r / min, and the dropping speed of the potassium permanganate solution is 1 mL / min to 2 mL / min; Optionally, the precipitation reaction temperature is 10° C. to 40° C., and the time is 1 h to 6 h.

6. The method for preparing the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material according to claim 1, characterized in that: In step S2, the atmosphere of the second calcination treatment is air, the heating rate is 3°C / min to 10°C / min, the holding temperature is 300°C to 800°C, and the holding time is 3h to 8h.

7. The method for preparing the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material according to claim 1, characterized in that: In step S3, the oxidation degree of the graphene oxide is 10% to 50%, the thickness of the flake is 0.1 nm to 3 nm, and the particle size is 50 μm to 300 μm; Optionally, the reducing agent comprises one or more of ascorbic acid, ethylenediamine, hydrazine, hydroiodic acid, sodium borohydride and ammonia; Optionally, the addition mass ratio of the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2 composite material, graphene oxide and reducing agent is (1-5):(0.5-3):(0.25-6); Optionally, in the solution system of the second hydrothermal reaction, the total added concentration of the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2 composite material, graphene oxide and reducing agent is 0.4wt% to 10wt%; Optionally, the temperature of the second hydrothermal reaction is 60° C. to 120° C., and the time is 2 h to 10 h.

8. The method for preparing the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material according to claim 1, characterized in that: In step S3, during the ethanol solution soaking treatment, the concentration of the ethanol solution is 5% (v / v) to 30% (v / v); Optionally, the mixing ratio of the second hydrothermal reaction product and the ethanol solution is (1-10) g: (100-1000) mL; Optionally, the soaking treatment is performed at a temperature of 10°C to 40°C and for a time of 12h to 48h; Optionally, the freezing treatment temperature is -80°C to -15°C, and the time is 5h to 24h; Optionally, the freeze-drying treatment is performed at a temperature of -80°C to -60°C, a pressure of 1 Pa to 10 Pa, and a time of 12 hours to 72 hours.

9. A nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material has a multi-porous structure, and the multi-porous structure is formed by the accumulation of circular cluster structures; Optionally, the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material is loaded with 0.5 wt% to 1 wt% of rare earth metal elements.

10. Use of the nitrogen-doped MOF-derived hollow porous carbon-rare earth metal-doped MnO2-graphene aerogel composite material according to claim 9 in air purification.

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