CN107158964A - A kind of composite film material based on metal organic framework nanometer sheet and graphene oxide, preparation method and the application in gas separation - Google Patents

Abstract

The invention discloses a composite membrane material based on metal-organic framework nanosheets and graphene oxide and its application in gas separation, belonging to the technical field of membrane materials and separation thereof. Firstly, metal oxide nanosheets are prepared at room temperature, and the composite film material is paved with graphene oxide dispersion liquid by layer-by-layer method. Graphene oxide is used as the main body of the film, and metal oxide nanosheets are doped in it. The obtained composite membrane material is reacted with an organic ligand to convert it into a graphene oxide composite membrane material doped with metal-organic framework nanosheets. Through this strategy, the metal-organic framework material with uniform pores was successfully introduced into the membrane material while maintaining the ultra-thin thickness, thereby improving the separation selectivity by 6 times compared with the pure graphene oxide membrane, and compared with the direct method. Membrane materials have also improved significantly. Comparing the membrane materials with different numbers of layers, it can be found that the selectivity of the membrane increases significantly with the increase of the number of cycles. It is the best value at 4 cycles, and decreases at 5 cycles.

Description

A composite membrane material based on metal-organic framework nanosheets and graphene oxide, Preparation method and application in gas separation

technical field

The invention belongs to the technical field of membrane materials and their separation, and in particular relates to a composite membrane material based on metal organic framework nanosheets and graphene oxide and its application in gas separation.

Background technique

The separation and purification process of mixed substances is an important step in industrial production, which consumes a lot of energy and produces pollution. Mixed gases generally have similar physical properties and molecular sizes, so the separation process is challenging. Compared with traditional separation methods, the membrane separation process has the advantages of energy saving, high efficiency, easy operation, continuous work and small space. Membrane material is one of the cores of membrane separation process, ideal separation membrane material should have high gas permeability and selectivity at the same time. Membrane materials that are currently studied mainly include polymer membranes and inorganic membrane materials. Polymer membranes have been widely used in the separation field because of their advantages such as easy processing and low cost. The pore size distribution of the polymer membrane is not uniform and is prone to plasticization, which affects the stability of the gas separation performance and cannot achieve high selectivity and permeability at the same time. Molecular sieves and metal-organic framework membrane materials are mainly used in the research of inorganic separation membranes for gas separation. They have uniform pore size distribution, which can overcome the shortcomings of polymer membranes and achieve high selectivity and permeability at the same time. Such inorganic microporous membrane materials are generally synthesized by hydrothermal or solvothermal methods, which are difficult to process and high in cost. The researchers prepared a mixed matrix membrane by combining polymers and inorganic microporous materials as a short-term solution.

In recent years, researchers have prepared two-dimensional materials (graphene oxide, molybdenum disulfide, molecular sieves and metal-organic framework nanosheets) into films to reduce the thickness of the film and improve the performance of the film. There are still some problems in the composition of a single material. For example, graphene oxide (GO) membranes use layer gaps and defects to penetrate gas molecules, which affects selectivity, while inorganic microporous material nanosheets with uniform pores mainly pass through top-to-bottom exfoliation. Process preparation, scale and yield are all affected.

Contents of the invention

The object of the present invention is to provide a composite membrane material based on metal-organic framework nanosheets and graphene oxide, a preparation method and its application in gas separation. Firstly, metal oxide nanosheets are prepared at room temperature, and the composite film material is paved with graphene oxide dispersion liquid by layer-by-layer method. Graphene oxide is used as the main body of the film, and metal oxide nanosheets are doped in it. The obtained composite membrane material is reacted with an organic ligand to convert it into a graphene oxide composite membrane material doped with metal-organic framework nanosheets. Through this strategy, the metal-organic framework material with uniform pores was successfully introduced into the membrane material while maintaining the ultra-thin thickness, thereby improving the separation selectivity by 6 times compared with the pure graphene oxide membrane.

The involved metal-organic framework material HKUST-1 (Stephen S.-Y.Chui, Samuel M.-F.Lo, Jonathan PHCharmant, A.Guy Orpen, Ian D.Williams, "A ChemicallyFunctionalizable Nanoporous Material [Cu ₃ (TMA ) ₂ (H ₂ O) ₃ ] _n ”, Science, 1999, 283, 5405, 1148-1150) is a propeller-like three-dimensional skeleton structure formed by metal copper ions and organic ligand trimellitic acid (BTC). Each copper ion has a weakly coordinated water molecule that can be removed to form an unsaturated metal site, which has an adsorption effect on carbon dioxide molecules, and improves the gas separation selectivity of the membrane material through selective adsorption.

A kind of preparation method of the composite membrane material based on metal-organic framework nanosheet and graphene oxide of the present invention, its steps are as follows:

(1) Prepare graphene oxide solution

Graphene oxide (analytical pure) and deionized water were mixed to prepare a graphene oxide solution with a concentration of 0.05-0.2 g·L ^-1 , and the solution was ultrasonically dispersed, labeled as solution A, sealed and left standing;

(2) Preparation of copper oxide nanosheet solution

Add copper nitrate to deionized water to prepare a copper nitrate solution with a concentration of 1-3 mmol L- ¹ ; add ethanolamine to deionized water to prepare an ethanolamine solution with a concentration of 1-2 mmol L ^-1 ; combine the above two The solutions are mixed in equal volumes, reacted under airtight and magnetic stirring for 0.5 to 3 hours, and then airtightly allowed to stand at room temperature for 20 to 30 hours to obtain a solution of copper oxide nanosheets, which is marked as solution B;

(3) Preparation of ligand solution

Dissolve trimesic acid in a mixed solvent of ethanol and water to prepare a solution of trimesic acid with a concentration of 0.5-2mmol L ^-1 , which is marked as solution C; the volume ratio of ethanol and water is 1:1, and sealed stand still;

(4) Preparation of two-dimensional composite membranes by layer-by-layer method

Add 5mL of solution A and solution B to the suction filtration device in turn for suction filtration, and complete 2 to 5 cycles; when the last cycle is completed and completely drained, add another layer of 1 to 10mL of solution A to cap and completely drain Finally, the preliminary membrane formation is completed; then 10-50mL solution C is added to the suction filtration device to convert copper oxide nanosheets into HKUST-1, thereby obtaining a composite membrane material based on metal organic framework nanosheets and graphene oxide.

The composite membrane material of the invention can be widely used in the separation of mixed gases (H ₂ /CO ₂ , CH ₄ /CO ₂ , N ₂ /CO ₂ ), especially for the separation of hydrogen and carbon dioxide.

Relevant test conditions and methods involved in the present invention:

Scanning Electron Microscope (SEM) photos: S4800 scanning electron microscope from Hitachi, Japan was used for SEM.

X-ray electron diffraction (XRD) spectrum: The XRD test uses the LabX XRD-6000 X-ray diffractometer of SHIMAZU, Japan. Using a Cu emission field, the scan 2theta range is 4-40°.

Atomic force microscope (AFM) photo: MultiMode Scanning Probe Microscope.

Transmission electron microscope (TEM) image: JEM-2100 from JEOL, JEOL.

Gas separation test, using the Wicke-Kallenbach Technique device (Angew.Chem.Int.Ed.2006, 45, 7053–7056), two kinds of gas, water vapor and carrier gas Ar from the gas under the control of the mass flow controller The bottle enters the membrane module, and the pressure difference between the two ends of the membrane is controlled by the back pressure valve at the gas outlet. The permeated gas is purged by the carrier gas into the gas chromatograph to check the content of various gases to determine the separation effect.

Gas chromatography (GC) analysis: Shimadzu GC2014; column temperature: 50°C; detector: TCD, the composition of the mixed gas is carbon dioxide and hydrogen at a volume ratio of 1:1.

Description of drawings

Figure 1: XRD spectrum of HKUST-1@GO composite film in Example 1-4;

Figure 2: Front SEM photos of the HKUST-1@GO composite membrane in Examples 1-4;

Figure 3: SEM photos of the cross-section of the HKUST-1@GO composite membrane in Examples 1-4;

Comparing the simulated standard spectrum in Figure 1, it can be found that the peak position of the synthesized spectrum is consistent with the simulated standard spectrum, indicating that the membrane materials prepared in Examples 1-4 are doped with HKUST-1.

Figure 2 is the front SEM photo of the HKUST-1@GO composite membrane prepared in Example 1-4 (the right picture is the enlarged picture of the left picture), a and b are 2 cycles, c and d are 3 cycles, e and f are 4 loops, g and h are 5 loops. From the figure, we can find that, except for two cycles of HKUST-1@GO-2, defects were found, and the other cycles obtained continuous and flat membrane materials.

Fig. 3 is a cross-sectional SEM photo of the HKUST-1@GO composite membrane prepared in Examples 1-4. a is 2 cycles, b is 3 cycles, c is 4 cycles, and d is 5 cycles. From the figure, we get that the thickness of the film is in the range of 100-300 nanometers, which shows that we have maintained an ultra-thin film thickness while introducing HKUST-1 with uniform channels.

detailed description

Example 1

(1) Prepare graphene oxide solution (solution A)

Purchase graphene oxide (analytical pure) products from Pioneer Nano, and prepare graphene oxide and deionized water to prepare a graphene oxide original concentration solution of 0.1 g L ⁻¹ . Place the prepared original graphene oxide solution in an ultrasonic disperser for ultrasonic dispersion, seal it and let it stand for later use.

(2) Preparation of copper oxide nanosheet solution (solution B)

Accurately weigh copper nitrate in beaker A with an electronic balance, add deionized water and stir to accelerate dissolution to make 2mmolL ^-1 ; take another beaker B, prepare 1.6mmol·L ^-1 ethanolamine solution with deionized water, and put beaker A, The solutions in B were mixed in equal volumes. Put the cleaned and dried magnets into the mixed solution beaker along the wall of the cup, and cover with a layer of parafilm to prevent a large amount of water from evaporating. The sealed mixed solution beaker was placed on an electronic stirrer, and after stirring for 1 hour, it was placed in a vacuum drying oven at 25 degrees Celsius for 24 hours at a constant temperature. After the copper oxide nanosheet solution is prepared, it is sealed and left to stand for later use.

(3) Preparation of ligand solution (solution C)

Weigh the BTC solid with an electronic balance to prepare a 1 mmol L ^-1 BTC ethanol/water solution, the volume ratio of ethanol and water is 1:1, seal it and let it stand for later use.

(4) Preparation of two-dimensional composite membranes by layer-by-layer method

Clean the suction filter device and rinse it with deionized water. After drying, assemble the suction filter device reasonably. Use the nylon filter membrane (diameter 47mm, pore size 200nm) as the base. After ensuring that the clip is clamped, turn on the water pump and use a large beaker Take an appropriate amount of tap water and deionized water to rinse three times respectively, remove the suction filter head, pour out the water in the filtrate bottle, and reassemble the suction filter device. After the preparation work is completed, add a thin layer of deionized water on the sand core of the suction filter head, so that the nylon support layer can be placed smoothly without air bubbles when the nylon support layer is placed in the next step. After placing the nylon support layer, put the rubber gasket immediately, the purpose is to prevent liquid leakage, assemble the remaining parts, turn on the water pump of the suction filter device, pour in an appropriate amount of deionized water to test the leak, if it leaks, remove the device backwards and wipe it on the interface Apply a little vacuum grease; if there is no water leakage, continue to the next step.

Add 5mL of solutions A and B sequentially to the suction filtration device to complete 2 cycles. After completing the last cycle and waiting for complete draining, continue to add another layer of 5mL solution A to cap, and wait for complete draining. After the initial film formation, 25mL solution C was added for conversion, and the copper oxide nanosheets were converted into HKUST-1 to obtain a composite film HKUST-1@GO-2.

(5) Characterization of membrane

It was subjected to powder X-ray diffraction pattern test, scanning electron microscope, transmission electron microscope, atomic force microscope characterization and mixed gas separation test. The gas test results are shown in Table 1.

Example 2

Steps (1) to (3) are the same as in Example 1.

(4) Preparation of two-dimensional composite membranes by layer-by-layer method

The installation and leak testing of the suction filtration device are the same as in Example 1. Add 5mL of solutions A and B sequentially to the suction filtration device to complete 3 cycles. After completing the last cycle and waiting for complete draining, continue to add another layer of 5mL solution A to cap, and wait for complete draining. After the initial film formation is completed, 25mL solution C needs to be added to convert the copper oxide nanosheets doped with re-oxidized graphene into HKUST-1 to obtain a composite film HKUST-1@GO-3.

(5) Characterization of membrane

It was subjected to powder X-ray diffraction pattern test, scanning electron microscope, transmission electron microscope, atomic force microscope characterization and mixed gas separation test. The gas test results are shown in Table 1.

Example 3

Steps (1) to (3) are the same as in Example 1.

(4) Preparation of two-dimensional composite membranes by layer-by-layer method

The installation and leak testing of the suction filtration device are the same as in Example 1. Add 5mL of solutions A and B sequentially to the suction filtration device to complete 4 cycles. After completing the last cycle and waiting for complete draining, continue to add another layer of 5mL solution A to cap, and wait for complete draining. After the initial film formation, 25mL solution C needs to be added for conversion, and the copper oxide nanosheets doped with re-oxidized graphene are converted into HKUST-1, and the composite film HKUST-1@GO-4 is obtained.

(5) Characterization of membrane

It was subjected to powder X-ray diffraction pattern test, scanning electron microscope, transmission electron microscope, atomic force microscope characterization and mixed gas separation test. The gas test results are shown in Table 1.

Example 4

Steps (1) to (3) are the same as in Example 1.

(4) Preparation of two-dimensional composite membranes by layer-by-layer method

The installation and leak testing of the suction filtration device are the same as in Example 1. Add 5mL of solutions A and B sequentially to the suction filtration device to complete 5 cycles. After completing the last cycle and waiting for complete draining, continue to add another layer of 5mL solution A to cap, and wait for complete draining. After the initial film formation, 25mL solution C needs to be added for conversion, and the copper oxide nanosheets in the doped re-oxidized graphene are converted into HKUST-1, and the composite film HKUST-1@GO-5 is obtained.

(5) Characterization of membrane

It was subjected to powder X-ray diffraction pattern test, scanning electron microscope, transmission electron microscope, atomic force microscope characterization and mixed gas separation test. The gas test results are shown in Table 1.

Comparative example 1

Step (1) is identical with embodiment 1.

(2) Preparation of pure GO two-dimensional membrane

The installation and leak testing of the suction filtration device are the same as in Example 1. Add 25mL of solution A to the suction filtration device, and wait until it is completely drained to obtain a pure GO membrane.

(3) Characterization of the membrane

The mixed gas separation test was carried out on it, and the gas test results are shown in Table 1.

Comparative example 2

Steps (1) to (3) are the same as in Example 1.

(4) Preparation of two-dimensional composite membranes by direct mixing method

The installation and leak testing of the suction filtration device are the same as in Example 1. After mixing equal volumes of solutions A and B, take 40mL and add it to the suction filtration device, and wait for it to be completely drained. After the initial film formation is completed, 25mL of solution C needs to be added to convert the copper oxide nanosheets doped with re-oxidized graphene into HKUST-1 to obtain a composite film HKUST-1@GO-m.

(5) Characterization of membrane

It was subjected to powder X-ray diffraction pattern test, scanning electron microscope, and mixed gas separation test, and the gas test results are shown in Table 1.

Table 1: Gas separation performance data of the membranes of Examples 1-4 and Comparative Examples 1-2

Through comparison, it can be found that compared with the pure GO membrane, the gas separation selectivity of the HKUST-1@GO-4 membrane material has increased by about 6 times, and the membrane material obtained by the direct method has also improved significantly. Comparing the membrane materials with different layers, it can be found that the selectivity of the membrane increases significantly with the increase of the number of cycles. It is the best value at 4 cycles, and it decreases at 5 cycles.

Claims (4)

1. a kind of preparation method of the composite film material based on metal organic framework nanometer sheet and graphene oxide, its step is such as Under：

(1) graphene oxide solution is prepared

Graphene oxide (analysis is pure) and deionized water are hybridly prepared into concentration for 0.05~0.2gL^-1Graphene oxide Solution, the solution ultrasonic disperse is uniform, labeled as solution A, sealing and standing；

(2) cupric oxide nano piece solution is prepared

Copper nitrate is added into deionized water, concentration is made into for 1~3mmolL^-1Copper nitrate solution；By monoethanolamine add go from Sub- water, is made into concentration for 1~2mmolL^-1Ethanolamine solutions；Above two solution is mixed in equal volume, in closed, magnetic force The lower reaction of stirring 0.5~3 hour, it is then closed at room temperature to stand 20~30 hours, so that cupric oxide nano piece solution is obtained, Labeled as solution B；

(3) ligand solution is prepared

Trimesic acid is dissolved in the mixed solvent of second alcohol and water, concentration is made into for 0.5~2mmolL^-1Trimesic acid solution, Labeled as solution C；Wherein the volume ratio of second alcohol and water is 1：1, sealing and standing；

(4) layer-by-layer methods prepare two-dimentional composite membrane

Using nylon leaching film as substrate, the solution A and solution B that 5mL is sequentially added into Suction filtration device carry out suction filtration, complete 2~5 Circulation；After completing last time circulation and draining completely, then add one layer of 1~10mL solution A to bind, completed just after draining completely Step film；Then 10~50mL solution Cs are added into Suction filtration device again, cupric oxide nano piece is converted into HKUST-1, so that To the composite film material based on metal organic framework nanometer sheet and graphene oxide.

2. a kind of composite film material based on metal organic framework nanometer sheet and graphene oxide, it is characterised in that：It is by right It is required that the method described in 1 is prepared.

3. a kind of composite film material based on metal organic framework nanometer sheet and graphene oxide described in claim 2 is in gas Application in separation.

4. a kind of composite film material based on metal organic framework nanometer sheet and graphene oxide as claimed in claim 3 is in gas Application in body separation, it is characterised in that：For separating hydrogen and carbon dioxide.