CN107790102B

CN107790102B - Three-dimensional folded spherical MOFs @ rGO oil absorption material and preparation method thereof

Info

Publication number: CN107790102B
Application number: CN201711060092.2A
Authority: CN
Inventors: 顾佳慧; 范红玮; 孟洪
Original assignee: Beijing University of Chemical Technology
Current assignee: Beijing University of Chemical Technology
Priority date: 2017-11-01
Filing date: 2017-11-01
Publication date: 2020-05-19
Anticipated expiration: 2037-11-01
Also published as: CN107790102A

Abstract

A three-dimensional folded spherical MOFs @ rGO oil absorption material and a preparation method thereof belong to the technical field of oil-water separation. The graphene oxide composite material comprises three-dimensional reduced graphene oxide spheres with folded structures and metal organic framework materials fixedly supported between folded reduced graphene oxide sheets; the specific method comprises the following steps: dispersing graphene oxide, metal salt and an organic ligand into deionized water, enabling a metal organic framework material to grow on a graphene oxide nano sheet in situ, and adding a reducing agent to form a suspension A; or directly adding a metal organic framework material into the graphene oxide aqueous solution, and adding a reducing agent to form a suspension B; and pressing the suspension A or the suspension B into an ultrasonic spray head, dispersing the suspension A or the suspension B into micro-nano-scale liquid drops under the action of ultrasonic waves, depositing the micro-nano-scale liquid drops into a high-temperature organic solvent, and carrying out self-assembly on the graphene oxide nanosheets under the action of high temperature and a reducing agent. The composite material prepared by the invention has high oil absorption and cycling stability.

Description

Three-dimensional folded spherical MOFs @ rGO oil absorption material and preparation method thereof

Technical Field

The invention belongs to the technical field of oil-water separation, and particularly relates to a three-dimensional folded spherical MOFs @ rGO oil absorption material and a preparation method thereof.

Background

In recent years, the amount of oily wastewater generated by industrial production is increasing, and oil leakage at sea is frequent, and oil-water separation technology is receiving attention, but is a great challenge. The common oil-water separation technology, such as flocculation, flotation, slag scraping, emulsion breaking, gravity separation and the like, has the problems of more additives, easy chemical pollution, secondary pollution and the like, and has high separation cost and low separation efficiency. The adsorption method has the advantages of high separation efficiency, low cost, recyclability and the like, and the core of the adsorption method is to develop a high-performance adsorbent which has high adsorption capacity and can be recycled and stably used.

The graphene is formed by the SP of carbon atoms²The novel two-dimensional atomic crystal formed by the hybridized and connected monoatomic layers has the theoretical thickness of only 0.34nm, is the thinnest nano material discovered so far, and has an ultra-large specific surface area and excellent mechanical property. Because the binding energy between water molecules in the water drops is far larger than the adsorption between the water drops and the surface of the single-layer grapheneGraphene itself can exhibit a certain hydrophobic property, and can be used as a construction element of a super-hydrophobic-super-oleophilic adsorption material, such as Nguyen and the like (d.d.nguyen, n.h.tai, s.b.lee, w.s.kuo, Energy environ.sci.,2012,5: 7908-7912.) and Gao and the like (y.liu, j.k.ma, t.wu, x.r.wang, g.b.huang, y.liu, h.x.qiu, y.li, w.wang, j.p.gao, ACS appl.mater.interfaces.,2013,5: 10018-10026.) all adopt a solution impregnation method to cover a graphene sheet layer on the surface of a commercial sponge, so that the sponge material has the super-hydrophobic property, and the composite material can absorb about 40-165 times of organic solvent or oil product weight. But oil molecules can only be transferred through the pore channels of the sheet layer, and due to the two-dimensional characteristic of the oil molecules, the mass transfer path is longer, and the adsorption efficiency still has a space for further improvement. If two-dimensional sheet graphene is converted into a three-dimensional wrinkled structure through physical or chemical action, a shorter molecular transfer channel is expected to be created, and meanwhile, the hydrophobicity of the graphene can be further improved, and the separation performance of the adsorption material is improved.

The Metal-Organic Frameworks (MOFs) are porous crystal materials formed by self-assembling oxygen or nitrogen-containing rigid Organic ligands and inorganic Metal ion clusters, and are high in thermal stability, large in specific surface area, high in porosity and light in density, and also are potential super-wettability oil-absorbing materials. For example, the fluorine-containing metal organic Framework Material (FMOF) is used as a potential oil absorbent in reversible adsorption experiments of n-hexane, cyclohexane, benzene, toluene and p-xylene by Omary et al (Yang, C., Kaipa, U., Mather, Q.Z., Wang, X., Nesterov, V., Venero, A.F., Omary, M.A., J.Am.Chem.Soc.,133(45):18094-18097.) to prove that the water adsorption cannot be detected even under the relative humidity of nearly 100 percent, and the hydrophobic performance of the activated carbon and the zeolite porous material is better. Therefore, the proper MOFs material is selected and doped into the graphene oxide, so that the advantages of the MOFs material and the graphene oxide can be combined, the MOFs material and the graphene oxide can be self-assembled into a composite material, and the possibility for constructing a three-dimensional graphene adsorption material is provided. Jayaramulu et al [ Jayaramulu, K., Datta, K.K.R.,

C.,Petr,M.,Otyepka,M.,Zboril,R.,Fischer,R.A.,Angew.Chem.Int.Edit.,2016,55(3):1178-1182.]the composite material combining fluorine-containing graphene oxide and ZIF-8 is impregnated on the sponge, so that the sponge has super-hydrophobicity-super-lipophilicity, and the sponge can absorb 1.5-6 times of organic solvent by weight. There still exist a series of bottleneck problems such as: the separation efficiency and durability of the material still remain to be further improved; the preparation of some materials needs fluorine polymers or modifiers, so that the cost is high, secondary pollution is easy to cause, and the like.

Disclosure of Invention

The invention aims to solve the technical problem of providing a preparation method of a three-dimensional folded spherical MOFs @ rGO material, converting graphene into a folded three-dimensional structure, enriching molecular transfer channels of the graphene, exerting the advantages of abundant MOF pore channel structures and ultrahigh mechanical property of the graphene, and obtaining a super-hydrophobic-super-oleophylic oil-water separation material with strong durability. The specific technical scheme is as follows:

the invention provides a three-dimensional folded spherical MOFs @ rGO oil absorption material which is characterized by comprising three-dimensional reduced graphene oxide spheres with folded structures and a metal organic framework material fixedly carried between folded reduced graphene oxide lamella.

In the three-dimensional folded spherical MOFs @ rGO oil absorption material, the three-dimensional folded spherical reduced graphene oxide is formed by self-assembling two-dimensional graphene oxide nanosheets through high-temperature reduction; the metal organic framework material is grown on the surface of the reduced graphene oxide sheet in situ or is immobilized in the three-dimensional folded reduced graphene oxide ball through the physical wrapping effect of the reduced graphene oxide sheet.

Specifically, the particle size range of the three-dimensional folded spherical MOFs @ rGO oil absorption material is 1-10 μm; the particle size range of the metal organic framework material is 1 nm-1 mu m.

Preferably, the metal organic framework material is selected from the group consisting of Zeolitic Imidazolate Framework (ZIFs) materials including ZIF-1, ZIF-2, ZIF-3, ZIF-4, ZIF-5, ZIF-6, ZIF-7, ZIF-8, ZIF-9, ZIF-10, ZIF-11, ZIF-12, ZIF-20, ZIF-22, ZIF-67, ZIF-68, ZIF-69, ZIF-71, ZIF-78, ZIF-90, ZIF-95, IRMOF materials including IRMOF-0, IRMOF-1, IRMOF-2, IRMOF-3, IRMOF-4, IRMOF-5, IRMOF-6, IRMOF-7, IRMOF-8, IRMOF-9, IRMOF-10, IRMOF-12, IRMOF-14, IRMOF-16, IRMOF-18, CPL-1, and CPL-1, CPL-2), MIL series materials (including MIL-23, MIL-24, MIL-47, MIL-53, MIL-68, MIL-77, MIL-88, MIL-100, MIL-101), PCN series materials (including PCN-11, PCN-13, PCN-61, PCN-46, PCN-94, PCN-105, PCN-124, PCN-222, PCN-888), UiO series materials (including UiO-66, UiO-67).

Specifically, in the three-dimensional folded spherical MOFs @ rGO oil absorption material, the loading capacity of a metal organic framework material on reduced graphene oxide is 0.1-5 g/g.

The invention provides a preparation method of the composite material, which comprises the following steps:

step a, dispersing a certain amount of graphene oxide into deionized water, ultrasonically peeling the graphene oxide, adding a certain amount of metal salt and organic ligand to enable the synthesized metal organic framework material to grow on a graphene oxide nanosheet in situ, centrifugally cleaning the graphene oxide nanosheet by using the deionized water, and then adding a certain amount of reducing agent to form a suspension A; or directly adding a certain amount of metal organic framework material into the uniformly dispersed graphene oxide aqueous solution, and then adding a certain amount of reducing agent to form a suspension B;

b, sucking the formed suspension A or suspension B into an injector with ultrasound, pressing the suspension A or suspension B into an ultrasonic nozzle through an injection pump, dispersing the suspension into micro-nano-scale droplets under the action of ultrasound and depositing the droplets into an organic solvent at 100-200 ℃, carrying out self-assembly on graphene oxide nanosheets under the action of high temperature and a reducing agent, and fixedly loading a metal organic framework material between reduced graphene oxide nanosheets;

and c, centrifugally separating and cleaning the synthesized material to obtain the three-dimensional folded spherical MOFs @ rGO oil absorption material.

Specifically, in the step a, the concentration of the original graphene oxide in the suspension A and the suspension B is 1-2 g/L; further preferably, the concentration of the metal salt added into the suspension A is 0.004-0.080 mol/L, and the concentration of the organic ligand is 0.008-6.00 mol/L; the mass ratio of the addition amount of the metal organic framework directly added into the suspension B to the graphene oxide is 0.1: 1-5: 1. After the reducing agent is added into the suspension A and the suspension B in the step a, only the surface layer part of graphene oxide is reduced at room temperature.

Specifically, in the step a, carrying out ultrasonic treatment on the graphene oxide solution for 2-18h, wherein the ultrasonic power is not lower than 300w, stirring once every half hour, and carrying out ultrasonic treatment for 2-3h every time to enable the graphene oxide to have a sheet diameter of 50-500 nm; the rotation speed during centrifugation is 6000-10000 rpm, and the time is 15-30 minutes.

Preferably, in the step b, the reducing agent is at least one of ascorbic acid, hydrazine hydrate, ethylenediamine, sodium citrate, L-cysteine, ammonia water vapor, sodium borohydride, hydroiodic acid and the like, and the mass ratio of the reducing agent to the graphene oxide is 7: 10-100: 10.

Specifically, in the step b, the ultrasonic power of the spray head is 0.5-1.5 w; the injection rate of the injection pump is 0.2-0.7 ml/min; the ultrasonic power of the injector is 0.5-1.5 w; the direction of the spray head is a vertical downward direction.

Specifically, in the step b, the organic solvent is at least one of water-immiscible organic solvents with the boiling point higher than 150 ℃, such as polydimethylsiloxane, n-octanol and the like, and the temperature of the organic solvent is preferably 120-200 ℃.

The technical scheme provided by the embodiment of the invention has the following beneficial effects: the three-dimensional folded spherical MOFs @ rGO oil absorption material formed by rapidly transforming graphene oxide and MOFs through high-temperature reduction synchronous self-assembly can fully exert the advantages of rich MOFs pore channel structures and ultra-strong performance of graphene, so that a multi-level pore channel structure is formed, an oil molecule transfer channel is optimized, and the material has the characteristics of stable structure, large specific surface area, high porosity, super-hydrophobicity and the like, does not need fluorine polymers, is environment-friendly, low in cost and free of secondary pollution.

Drawings

FIG. 1 is a scanning electron microscope image of a three-dimensional folded spherical ZIF-8@ rGO material prepared in example 3 of the present invention;

FIG. 2 is a scanning electron microscope image of a three-dimensional folded spherical ZIF-7@ rGO material prepared in example 4 of the present invention;

FIG. 3 is a scanning electron microscope image (3-1) and (3-2) of a three-dimensional folded spherical ZIF-67@ rGO material prepared in example 5 of the present invention, with the surface structure enlarged;

the scanning electron micrograph was observed and measured by a Hitachi S-4800 Scanning Electron Microscope (SEM).

The invention is further described with reference to the following drawings and detailed description.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention clearer, the following will describe embodiments of the present invention in further detail with reference to the accompanying drawings, but the present invention is not limited to the following examples.

In a first aspect, the embodiment of the invention provides a three-dimensional folded spherical MOFs @ rGO oil absorption material, which comprises three-dimensional reduced graphene oxide spheres with folded structures and a metal organic framework material fixedly supported between folded reduced graphene oxide lamella;

Specifically, preferably, the particle size range of the metal organic framework complex material is 1 nm-1 μm, and can be 10nm, 50nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm and 1 μm, and the surface properties of the three-dimensional folded spherical MOFs @ rGO material can be regulated and controlled by immobilizing the metal organic framework material with different particle sizes, so that the oil-water separation performance of the material can be regulated and controlled.

Specifically, in the three-dimensional folded spherical MOFs @ rGO oil absorption material, the loading amount of the metal organic framework material is 0.1-5 g/g, and can be 0.1g/g, 0.2g/g, 0.3g/g, 0.4g/g, 0.5g/g, 0.6g/g, 0.7g/g, 0.8g/g, 0.9g/g, 1.0g/g, 2g/g, 3g/g, 4g/g or 5 g/g; the oil absorption material has the advantages that the loading capacity is too low, the effect of the metal-organic framework material is not obvious, the loading capacity is too high, the mechanical property effect of the graphene material is limited, the material is easy to be unstable, and the surface property and the pore structure of the oil absorption material can be regulated and controlled by controlling the loading capacity of the metal-organic framework material, so that the oil-water separation performance of the oil absorption material is optimized.

In a second aspect, an embodiment of the present invention provides a preparation method of the oil absorption material, including:

step a, dispersing a certain amount of graphene oxide into deionized water, ultrasonically peeling the graphene oxide, adding a certain amount of metal salt and organic ligand to enable the synthesized metal organic framework material to grow on a graphene oxide nanosheet in situ, centrifugally cleaning the graphene oxide nanosheet by using the deionized water, and then adding a certain amount of reducing agent to form MOFs @ rGO suspension A; or directly adding a certain amount of metal organic framework material into the uniformly dispersed graphene oxide aqueous solution, and then adding a certain amount of reducing agent to form a suspension B;

Preferably, in the step a, the concentration of the graphene oxide in the suspension A and the suspension B is 0.1-2 g/L; the amount of graphene oxide in the suspension with the concentration lower than 0.1g/L is less, and the self-assembly difficulty is increased during high-temperature reduction; the concentration is higher than 2g/L, and the graphene oxide is difficult to be uniformly dispersed in the aqueous solution. Specifically, the concentration can be 0.1g/L, 0.2g/L, 0.3g/L, 0.4g/L, 0.5g/L, 0.6g/L, 0.7g/L, 0.8g/L, 0.9g/L, 1g/L, 1.1g/L, 1.2g/L, 1.3g/L, 1.4g/L, 1.5g/L, 1.6g/L, 1.7g/L, 1.8g/L, 1.9g/L or 2g/L, and the size of the composite material formed by in-situ growth or doping of the metal framework material can be controlled by regulating graphene oxide solutions with different concentrations, so that the size of the three-dimensional folded spherical material after high-temperature reduction assembly can be controlled.

Preferably, the concentration of the metal salt added into the suspension A is 0.004-0.080 mol/L, and can be 0.004mol/L, 0.006mol/L, 0.008mol/L, 0.010mol/L, 0.020mol/L, 0.030mol/L, 0.040mol/L, 0.050mol/L, 0.060mol/L, 0.070mol/L or 0.080 mol/L; the concentration of the organic ligand is 0.008-6.00 mol/L, and can be 0.008mol/L, 0.010mol/L, 0.020mol/L, 0.03mol/L, 0.040mol/L, 0.05mol/L, 0.060mol/L, 0.070mol/L, 0.080mol/L, 0.090mol/L, 0.100mol/L, 0.200mol/L, 0.300mol/L, 0.400mol/L, 0.500mol/L, 0.600mol/L, 0.700mol/L, 0.800mol/L, 0.900mol/L, 1.000mol/L, 2.00mol/L, 3.000mol/L, 4.000mol/L, 5.000mol/L or 6.000 mol/L; the mass ratio of the metal organic framework material to the graphene oxide is 0.1: 1-5: 1, which can be 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1.0:1, 2:1, 3:1, 4:1 or 5: 1. When the immobilization amount of the metal organic framework is too low, the surface regulation effect is not obvious, the immobilization amount is too high, the amount of graphene oxide is small, and the advantage of the super-strong performance is difficult to exert.

Preferably, in the step a, the graphene oxide solution is subjected to ultrasonic treatment for 2-18h, the ultrasonic power is not lower than 300w, the graphene oxide solution is stirred once every half hour, and the graphene oxide solution is subjected to ultrasonic treatment for 2-3h every time, so that the sheet diameter of the graphene oxide is about 50-500 nm. The agglomerated sheets of the graphene oxide dispersion liquid can be dispersed by ultrasonic treatment, so that the size of the formed composite material is controlled.

Preferably, in the step a, the rotation speed during centrifugation is 6000-10000 rpm, which can be 6000rpm, 7000rpm, 8000rpm, 9000rpm or 10000 rpm; the centrifugation time is 15-30 minutes, and can be 15 minutes, 20 minutes, 25 minutes or 30 minutes; the graphene oxide/metal organic framework material suspension can be fully washed by increasing the rotating speed and the centrifugal time, and unbound materials are completely removed, so that the graphene oxide/metal organic framework material suspension is more stable.

Preferably, in the step b, the reducing agent is at least one of ascorbic acid, hydrazine hydrate, ethylenediamine, sodium citrate, L-cysteine, ammonia water vapor, sodium borohydride, hydroiodic acid, and the like, the mass ratio of the reducing agent to graphene oxide is 7: 10-100: 10, and may be 7:10, 8:10, 9:10, 10:10, 20:10, 30:10, 40:10, 50:10, 60:10, 70:10, 80:10, 90:10, or 100:10, and the different mass ratios of the reducing agent enable the reduction degrees to be different, so that the surface hydrophilicity and hydrophobicity of the composite material can be adjusted.

Preferably, in the step b, the ultrasonic power of the nozzle is 0.5-1.5 w, and may be 0.5w, 0.6w, 0.7w, 0.8w, 0.9w, 1.0w, 1.1w, 1.2w, 1.3w, 1.4w or 1.5 w; the injection rate of the injection pump is 0.2-0.7 ml/min, and can be 0.2ml/min, 0.3ml/min, 0.4ml/min, 0.5ml/min, 0.6ml/min or 0.7 ml/min; the ultrasonic power of the injector is 0.5-1.5 w, and can be 0.5w, 0.6w, 0.7w, 0.8w, 0.9w, 1.0w, 1.1w, 1.2w, 1.3w, 1.4w or 1.5 w; the direction of the ultrasonic spray head is a vertical downward direction; the size and atomization effect of the liquid drops can be controlled by controlling different injection rates and ultrasonic powers, and further the size of the formed composite material is controlled.

Preferably, in the step b, the organic solvent is at least one of water-immiscible organic solvents having a boiling point higher than 150 ℃ such as polydimethylsiloxane, n-octanol and the like, and the temperature of the organic solvent is 120 to 200 ℃, and may be 120 ℃, 125 ℃, 130 ℃, 135 ℃, 140 ℃, 145 ℃, 150 ℃, 155 ℃, 160 ℃, 165 ℃, 170 ℃, 175 ℃, 180 ℃, 185 ℃, 190 ℃, 195 ℃ or 200 ℃; the different temperature of the organic solvent can control the different folding degrees formed by the graphene, and the surface property of the oil absorption material is controlled.

The present invention will be further described below by way of specific examples.

In the following examples, those whose operations are not subject to the conditions indicated, are carried out according to the conventional conditions or conditions recommended by the manufacturer. The raw materials are conventional products which can be obtained commercially by manufacturers and specifications.

The following examples are for the test of adsorption properties, provided that pure solvents are used, and tested under normal temperature and pressure conditions.

Example 1

Zeolite-like imidazole ester framework material ZIF-8 is adopted, ascorbic acid is selected as a reducing agent, and Polydimethylsiloxane (PDMS) is selected as an organic solvent.

The preparation method comprises the following steps:

step a, dispersing 150mg of graphene oxide into 100ml of deionized water, carrying out ultrasonic treatment for 8 hours to peel off the graphene oxide, adding 0.117g of zinc nitrate hexahydrate, stirring to uniformly disperse the zinc nitrate, adding 2.27g of 2-methylimidazole, stirring to react, carrying out centrifugal washing at 6000rpm for three times, each time for 15 minutes, and adding 750mg of reducing agent to form a suspension A;

and b, sucking the formed suspension A into a 1.0w ultrasonic injector, pressing the suspension A into a 1.1w ultrasonic nozzle at the speed of 0.5ml/min through a syringe pump, and dispersing the suspension into micro-nano-scale droplets under the action of ultrasonic waves and depositing the droplets into PDMS at 165 ℃.

And c, centrifugally separating and cleaning the synthesized material for 3 times (rotating speed of 6000rpm), so as to obtain the three-dimensional folded spherical ZIF-8@ rGO oil absorption material.

SEM photograph (figure 1) shows that the particle size of the ZIF-8 doped three-dimensional folded spherical ZIF-8@ rGO oil absorption material is about 5 mu m.

The prepared three-dimensional folded spherical ZIF-8@ rGO oil absorption material is subjected to an adsorption performance test under the following test conditions: chloroform.

The adsorption performance is measured as follows: adsorbing 3.01g/g of trichloromethane.

Comparative example 1

Adopts zeolite-like imidazole ester framework material ZIF-8

The preparation method comprises the following steps:

adding 0.117g of zinc nitrate hexahydrate into 100ml of deionized water, and stirring to uniformly disperse the zinc nitrate hexahydrate; then 2.27g of 2-methylimidazole is added and stirred to generate ZIF-8; and (3) centrifugally washing for 3 times by using deionized water, wherein the centrifugal rotation speed is 10000rpm, and the time is 30min, so that the stable ZIF-8 material is obtained.

And (3) carrying out an adsorption performance test on the prepared ZIF-8 material, wherein the test conditions are as follows: chloroform.

The adsorption performance is measured as follows: adsorbing 1.91g/g of trichloromethane.

Example 2

Zeolite-like imidazole ester framework material ZIF-7 is adopted, ascorbic acid is selected as a reducing agent, and Polydimethylsiloxane (PDMS) is selected as an organic solvent.

The preparation method comprises the following steps:

step a, dispersing 150mg of graphene oxide into 100ml of deionized water, carrying out ultrasonic treatment for 8 hours to peel off the graphene oxide, adding 80mg of ZIF-7 powder, stirring to react, carrying out centrifugal washing at 6000rpm for three times, carrying out 15 minutes each time, and adding 750mg of reducing agent to form a suspension B;

and B, sucking the formed suspension B into a 1.0w ultrasonic syringe, pressing the suspension B into a 1.1w ultrasonic nozzle at the speed of 0.5ml/min through a syringe pump, and dispersing the suspension into micro-nano-scale droplets under the action of ultrasonic waves and depositing the droplets into PDMS at 165 ℃.

And c, centrifugally separating and cleaning the synthesized material for 3 times (rotating speed of 6000rpm), so as to obtain the three-dimensional folded spherical ZIF-7@ rGO oil absorption material.

SEM pictures (FIG. 2) show that the size of the ZIF-7@ rGO material doped with ZIF-7 in a three-dimensionally folded spherical shape is about 4 μm.

The prepared three-dimensional folded spherical ZIF-7@ rGO oil absorption material is subjected to an adsorption performance test under the following test conditions: chloroform.

The adsorption performance is measured as follows: adsorbing 3.30g/g of trichloromethane.

Example 3

Zeolite-like imidazole ester framework material ZIF-67 is adopted, ascorbic acid is selected as a reducing agent, and Polydimethylsiloxane (PDMS) is selected as an organic solvent.

The preparation method comprises the following steps:

step a, dispersing 150mg of graphene oxide into 100ml of deionized water, carrying out ultrasonic treatment for 8 hours to peel off the graphene oxide, adding 80mg of ZIF-67 powder, stirring to react, carrying out centrifugal washing at 6000rpm for three times, carrying out 15 minutes each time, and adding 750mg of reducing agent to form a suspension B;

And c, centrifugally separating and cleaning the synthesized material for 3 times (rotating speed of 6000rpm), so as to obtain the three-dimensional folded spherical ZIF-67@ rGO oil absorption material.

SEM photograph (FIG. 3) shows that the size of the ZIF-67 doped three-dimensional folded spherical ZIF-67@ rGO oil absorption material is about 4 μm.

The prepared three-dimensional folded spherical ZIF-67@ rGO oil absorption material is subjected to an adsorption performance test under the following test conditions: chloroform.

The adsorption performance is measured as follows: adsorbing trichloromethane 3.21 g/g.

Example 4

Zeolite-like imidazole ester framework material ZIF-11 is adopted, ascorbic acid is selected as a reducing agent, and Polydimethylsiloxane (PDMS) is selected as an organic solvent.

The preparation method comprises the following steps:

step a, dispersing 150mg of graphene oxide into 100ml of deionized water, carrying out ultrasonic treatment for 8 hours to peel off the graphene oxide, adding 80mg of ZIF-11 powder, stirring to react, carrying out centrifugal washing at 6000rpm for three times, carrying out 15 minutes each time, and adding 750mg of reducing agent to form a suspension B;

And c, centrifugally separating and cleaning the synthesized material for 3 times (rotating speed of 6000rpm), so as to obtain the three-dimensional folded spherical ZIF-11@ rGO oil absorption material.

The prepared three-dimensional folded spherical ZIF-11@ rGO oil absorption material is subjected to an adsorption performance test under the following test conditions: chloroform.

The adsorption performance is measured as follows: adsorbing the trichloromethane by 3.05 g/g.

Example 5

Zeolite-like imidazole ester framework material ZIF-12 is adopted, ascorbic acid is selected as a reducing agent, and Polydimethylsiloxane (PDMS) is selected as an organic solvent.

The preparation method comprises the following steps:

step a, dispersing 150mg of graphene oxide into 100ml of deionized water, carrying out ultrasonic treatment for 8 hours to peel off the graphene oxide, adding 80mg of ZIF-12 powder, stirring to react, carrying out centrifugal washing at 6000rpm for three times, carrying out 15 minutes each time, and adding 750mg of reducing agent to form a suspension B;

And c, centrifugally separating and cleaning the synthesized material for 3 times (rotating speed of 6000rpm), so as to obtain the three-dimensional folded spherical ZIF-12@ rGO oil absorption material.

The prepared three-dimensional folded spherical ZIF-12@ rGO oil absorption material is subjected to an adsorption performance test under the following test conditions: chloroform.

The adsorption performance is measured as follows: adsorbing 3.55g/g of trichloromethane.

Example 6

Zeolite-like imidazole ester framework material MOF-5 is adopted, ascorbic acid is selected as a reducing agent, and Polydimethylsiloxane (PDMS) is selected as an organic solvent.

The preparation method comprises the following steps:

step a, dispersing 150mg of graphene oxide into 100ml of deionized water, carrying out ultrasonic treatment for 8 hours to peel off the graphene oxide, adding 80mg of MOF-5 powder, stirring to react, carrying out centrifugal washing at 6000rpm for three times, carrying out 15 minutes each time, and adding 750mg of reducing agent to form a suspension B;

And c, centrifugally separating and cleaning the synthesized material for 3 times (at the rotating speed of 6000rpm), so as to obtain the three-dimensional folded spherical MOF-5@ rGO oil absorption material.

The prepared three-dimensional folded spherical MOF-5@ rGO oil absorption material is subjected to an adsorption performance test under the following test conditions: chloroform.

The adsorption performance is measured as follows: adsorbing the trichloromethane by 3.80 g/g.

Example 7

The preparation method comprises the following steps:

step a, dispersing 150mg of graphene oxide into 100ml of deionized water, carrying out ultrasonic treatment for 8 hours to peel the graphene oxide, adding 0.585g of zinc nitrate hexahydrate, stirring to uniformly disperse the graphene oxide, adding 11.35g of 2-methylimidazole, stirring to react, carrying out centrifugal washing at 6000rpm for three times, each time for 15 minutes, and adding 750mg of reducing agent to form a suspension A;

and b, sucking the formed suspension A into a 1.0w ultrasonic injector, pressing the suspension A into a 1.5w ultrasonic nozzle at the speed of 0.3ml/min through a syringe pump, and dispersing the suspension into micro-nano-scale droplets under the action of ultrasonic waves and depositing the droplets into PDMS at 165 ℃.

The adsorption performance of the prepared adsorption sponge of the three-dimensional folded spherical ZIF-8@ rGO material is tested, and the test conditions are as follows: chloroform.

Example 8

Zeolite-like imidazole ester framework material ZIF-68 is adopted, ascorbic acid is selected as a reducing agent, and Polydimethylsiloxane (PDMS) is selected as an organic solvent.

The preparation method comprises the following steps:

step a, dispersing 150mg of graphene oxide into 100ml of deionized water, carrying out ultrasonic treatment for 8 hours to peel off the graphene oxide, adding 80mg of ZIF-68 powder, stirring to react, carrying out centrifugal washing at 6000rpm for three times, carrying out 15 minutes each time, and adding 750mg of reducing agent to form a suspension B;

And c, centrifugally separating and cleaning the synthesized material for 3 times (rotating speed of 6000rpm), so as to obtain the three-dimensional folded spherical ZIF-68@ rGO oil absorption material.

The prepared three-dimensional folded spherical ZIF-68@ rGO oil absorption material is subjected to an adsorption performance test under the following test conditions: chloroform.

The adsorption performance is measured as follows: adsorbing trichloromethane 3.65 g/g.

Comparative example 2

The metal organic framework material is not doped, the reducing agent is ascorbic acid, and the organic solvent is Polydimethylsiloxane (PDMS).

The preparation method comprises the following steps:

step a, dispersing 150mg of graphene oxide into 100ml of deionized water, uniformly stirring, carrying out ultrasonic treatment for 8 hours, and adding 750mg of reducing agent to obtain a stable graphene oxide dispersion liquid.

And b, sucking the graphene oxide dispersion liquid into a 10ml injector, spraying the blending solution into PDMS (polydimethylsiloxane) at 165 ℃ through an ultrasonic spray head, and completing reduction and self-assembly of the graphene oxide so as to obtain the three-dimensional folded spherical rGO material.

And (3) carrying out adsorption performance test on the prepared three-dimensional folded spherical rGO material under the test conditions of: chloroform.

The adsorption performance is measured as follows: adsorbing 1.52g/g of trichloromethane.

The above description is only exemplary of the present invention and should not be taken as limiting the scope of the present invention, as any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. A three-dimensional folded spherical MOFs @ rGO oil absorption material is characterized by comprising three-dimensional reduced graphene oxide spheres with folded structures and a metal organic framework material fixedly supported between folded reduced graphene oxide sheets; the three-dimensional folded spherical reduced graphene oxide is formed by self-assembling two-dimensional graphene oxide nanosheets through high-temperature reduction; the metal organic framework material is grown on the surface of the reduced graphene oxide sheet in situ or is immobilized in the three-dimensional folded reduced graphene oxide ball through the physical wrapping effect of the reduced graphene oxide sheet; the particle size range of the three-dimensional folded spherical MOFs @ rGO oil absorption material is 1-10 micrometers; the particle size range of the metal organic framework material is 1 nm-1 mu m;

the preparation method of the three-dimensional folded spherical MOFs @ rGO oil absorption material comprises the following steps:

step c, centrifugally separating and cleaning the synthesized material to obtain the three-dimensional folded spherical MOFs @ rGO oil absorption material;

in the step a, the concentration of original graphene oxide in the suspension A and the suspension B is 1-2g/L, the concentration of metal salt added into the suspension A is 0.004-0.080 mol/L, and the concentration of an organic ligand is 0.008-6 mol/L; the mass ratio of the metal organic framework material directly added into the suspension B to the graphene oxide is 0.1: 1-5: 1;

in the step a, carrying out ultrasonic treatment on the graphene oxide solution for 2-18h, wherein the ultrasonic power is not lower than 300W, stirring once every half hour, and carrying out ultrasonic treatment for 2-3h every time to ensure that the sheet diameter of the graphene oxide is 50-500 nm; the rotation speed during centrifugation is 6000-10000 rpm, and the time is 15-30 minutes;

in the step b, the reducing agent is at least one of ascorbic acid, hydrazine hydrate, ethylenediamine, sodium citrate, L-half-fat ammonia acid, ammonia water steam, sodium borohydride and hydroiodic acid, and the mass ratio of the reducing agent to the graphene oxide is 7: 10-100: 10;

in the step b, the ultrasonic power of the spray head is 0.5-1.5W; the injection rate of the injection pump is 0.2-0.7 mL/min; the ultrasonic power of the injector is 0.5-1.5W; the direction of the spray head is a vertical downward direction;

in the step b, the organic solvent is at least one of polydimethylsiloxane and n-octanol.

2. The three-dimensional folded spherical MOFs @ rGO oil absorption material according to claim 1, wherein the metal organic framework material is at least one selected from zeolite-like imidazole ester framework (ZIFs) materials, IRMOF materials, CPL series materials, MIL series materials, PCN series materials and UiO series materials.

3. The three-dimensional folded spherical MOFs @ rGO oil absorption material according to claim 1, wherein the loading amount of the metal organic framework material on the reduced graphene oxide is 0.1-5 g/g.

4. A method for preparing the three-dimensional folded spherical MOFs @ rGO oil absorption material as claimed in any one of the claims 1 to 3, which is characterized by comprising the following steps: