LU503905B1

LU503905B1 - Carbon aerogel prepared by calcining mofs wafer, method and application in environmental protection and energy storage

Info

Publication number: LU503905B1
Application number: LU503905A
Authority: LU
Inventors: Zuoxi Li
Original assignee: Soochow Mofs Science And Tech Ltd
Priority date: 2023-04-11
Filing date: 2023-04-11
Publication date: 2023-10-16

Abstract

The invention relates to a carbon aerogel prepared by calcining a MOFs wafer and a method thereof, as well as its application in environmental protection and energy storage. The steps are as follows: synthesizing bibp, respectively dissolving it with Zn (ClO4)2·6H2O in a solvent, then mixing and stirring it at room temperature, filtering, washing and vacuum drying to obtain Zn-MOF white powder, pressing it into a circular wafer, putting it into a tube furnace, and heating at 5°C min-1 under nitrogen atmosphere. The carbon aerogel obtained by this method is the first MOF-derived carbon aerogel, which is light and porous, and has a wide range of practical application values in oil leakage, sewage treatment, formaldehyde purification and energy storage.

Description

DESCRIPTION LU503905

CARBON AEROGEL PREPARED BY CALCINING MOFS WAFER, METHOD AND

APPLICATION IN ENVIRONMENTAL PROTECTION AND ENERGY STORAGE

TECHNICAL FIELD

The invention relates to carbon aerogels, in particular to a carbon aerogel prepared by calcining a MOFs wafer and its methods, as well as its application in environmental protection and energy storage.

BACKGROUND

Carbon aerogels are a kind of porous and lightweight material with high specific surface area and pore volume, which usually shows good chemical, mechanical and thermal stability. Since its appearance in 1980s, carbon aerogels have often appeared in the

Guinness Book of World Records as the lowest density solid. The excellent porous properties make carbon aerogels appear in many cutting-edge research fields, such as water treatment adsorbent, oil spill cleaning, sound insulation materials, stationary phase of liquid chromatography column and energy storage. Diversified uses mean that carbon aerogels have penetrated into all aspects of people's lives. The study of carbon aerogel not only has important scientific value, but also has a far-reaching impact on the global economy.

Nowadays, carbon aerogels are obtained from wet gel by excluding a large number of liquid components. However, in the conventional evaporation process, the liquid-solid surface tension in the capillary is enough to destroy the fragile gel network, which will cause serious structural shrinkage after drying. In order to prevent the matrix from collapsing and maintain the gel structure, people have developed a supercritical drying process, but it has a dangerous operating environment such as high pressure, and the instrument cost is very expensive. In order to avoid high-pressure conditions, freeze-

drying technology came into being, which can prevent the formation of liquid-solid surfadé/503905 and capillary force, and the solid ice sublimates directly with the temperature rise, leaving carbon aerogels products. Freeze-drying requires a long period of carbon dispersion and gelation. In addition, the freeze-drying process is also time-consuming and laborious.

Although carbon aerogels with excellent performance are occasionally reported, the very expensive raw materials of carbon nanotubes or graphene will deter developers.

Therefore, it is still a great challenge to develop a simple, economical and effective carbon aerogels production process to expand its practical application value.

Calcining organic matter in Na atmosphere is an important method to prepare carbon materials. But so far, all the samples obtained by this method are powder samples. Metal- organic frameworks (MOF s) are an important kind of ordered porous crystalline materials, which are rich in organic components and carbon sources. Therefore, using the precursor strategy, MOFs raw materials can be easily prepared into carbon materials after calcination. Moreover, the inorganic components of MOFs can also modify the derived carbon materials. We have found that perchloric acid and zinc ions have pore-forming effect, which can increase the porosity of MOF-derived carbon materials. Therefore, we combine the pore-forming effects of the two to skillfully synthesize a Zn-MOF containing perchlorate ions. A light and porous carbon aerogel (CA-1NMOF) is obtained by pressing

Zn-MOF powder into a circular sheet, followed by calcination and pyrolysis.

SUMMARY LU503905

The invention aims to provide a carbon aerogel prepared by calcining a MOFs wafer and its method, as well as its application in environmental protection and energy storage.

The technical scheme adopted by the invention is as follows: a method for preparing carbon aerogel based on MOFs wafer calcination is characterized in that: it is realized by the following steps: step 1: synthesizing 4,4'-bisimidazole biphenyl, which is called bibp; step 2: synthesize {[Zn(bibp)2] :(Cl04)2(CHCI3)2(CH30H)} ..(Zn-MOF); 3.6 mmol bibp and 1.8 mmol Zn (ClO4)2-6H20 are dissolved in the solvent respectively, then the two solutions are mixed and stirred at room temperature, and then filtered, and the filter cake is washed with ethanol; finally, vacuum drying to obtain Zn-MOF white powder; step 3: preparing carbon aerogel CA-1NMOF: 40.0 mg of Zn-MOF white powder is pressed into round pieces, put into a tube furnace, heated to 1,000°C at the rate of 5°C min” in nitrogen atmosphere, and naturally cooled to room temperature after 3 h, thus obtaining a strip-shaped monolithic carbon material, namely carbon aerogel CA-1NMOF.

In the step 2, 3.6 mmol of bibp and 1.8 mmol of Zn (CIO4)2-6H20 are dissolved in 100 mL of chloroform and 50 mL of methanol, respectively.

In the step 2, the two solutions are mixed at room temperature and then stirred for 4 h.

In the step 2, the filter cake is washed with ethanol for 3 times, and then dried in vacuum at 80°C for 4 h to obtain Zn-MOF white powder.

In the step 3, the Zn-MOF white powder is pressed into a © 6.0x0.9 mm disc at 6 MPa.

In the step 3, the size of the strip-shaped monolithic carbon material is ® 6.0x50.0 mm.

A carbon aerogel obtained by the method for preparing carbon aerogel based on MOFs wafer calcination.

An application of the carbon aerogel in environmental protection is characterized in that:

as a green adsorbent, the carbon aerogel is applied to the adsorption treatment of dy&J503905 pollution, the purification of formaldehyde in the air and the treatment of oil leakage.

An application of the carbon aerogel in energy storage is characterized in that: the carbon aerogel is used as an electrode material to prepare a supercapacitor, start a hybrid vehicle with high power, and supply power to precision instruments for a long time.

The invention has the following advantages:

The invention obtains a light and porous carbon aerogel CA-1NMOF (density 5.6 mg-cm- 3, porosity 98.3%, specific surface area 1,515.2 m? g°") by calcining a Zn-MOF wafer. CA- 1NMOF has excellent environmental protection and energy storage performance. 9.1 kg

CA-1NMOF can absorb 1 ton of gasoline, and the oil absorption value reaches 109.9 g/g.

After 5 cycles, it still maintains 90.1% absorption capacity. At the same time, CA-1NMOF shows strong adsorption capacity of methylene blue, and 1 g Ca-1NMOF could purify 3.2

L of methylene blue solution. CA-1NMOF also has a high absorption efficiency for formaldehyde, and 1 g CA-1NMOF can absorb 0.1353 formaldehyde gas, which is higher than the formaldehyde absorption materials on the market, and can be directly popularized and applied. In addition, through the electrochemical performance test, the capacitance value of CA-1-NMOF is as high as 313 F g', and the corresponding symmetrical battery energy density reaches 20.7 Wh kg, and only 4.8% of the capacity value is lost after 10,000 cycles, which opens up a new era for the development of supercapacitors. Generally speaking, we obtain the first MOF-derived carbon aerogel CA- 1NMOF by simple wafer calcination method, which has a wide range of practical application values in oil spill, sewage treatment, formaldehyde purification and energy storage.

BRIEF DESCRIPTION OF THE FIGURES LU503905

FIG. 1 is a flow chart for preparing CA-1-NMOF by calcining Zn-MOF wafer.

FIG. 2 shows xrd(a), Raman(b) and XPS(c) spectra of Zn-MOF-derived carbon materials.

FIG. 3 shows the adsorption-desorption curve and pore size distribution of nitrogen.

FIG. 4 shows the test results of mercury intrusion method.

FIG. 5 is a field emission scanning image of CA-1NMOF.

FIG. 6 is the lens electron diffraction image of CA-1NMOF.

FIG. 7 shows the adsorption decoloration process of methylene blue (a) and the UV-Vis spectrum (b) in different time periods.

FIG. 8 is a comparison chart of formaldehyde purification capacity of three carbon materials (Green Source Company and Greensky Company).

FIG. 9 shows CV curve (a) of three-electrode system at different scanning speeds, GCD curve (b) of two-electrode battery at different current densities, Ragone diagram (c) and cycle stability curve (d) of SSC.

DESCRIPTION OF THE INVENTION

The present invention will be described in detail with reference to specific embodiments.

The invention relates to a method for preparing carbon aerogel based on MOFs wafer calcination. By calcining Zn-MOF wafer, a light and porous carbon aerogel CA-1NMOF (density 5.6 mg:cm”, porosity 98.3%, specific surface area 1, 515.2 m? g') is obtained.

The method is specifically realized by the following steps: step 1: synthesis of 4,4'-bis(imidazol-1-yl)-biphenyl (abbreviated as bibp)

It is prepared by the copper-catalyzed N-arylation of azoles with aryl bromides. We have optimized the synthesis process of bibp, and only need simple precipitation and filtration steps to purify it. The specific operations are as follows: add a mixture of 4,4'- dibromobipheny! (120 mmol, 37.44 g), imidazole (480 mmol, 32.68 g), Cul (6 mmol, 1.14 g), 1,10-phenanthroline (12 mmol, 2.16 g) and K:CO> (600 mmol, 800g) into 800 mL of

DMF. The mixture is heated to reflux for 4 days and cooled to room temperature, followed by filtering to remove solid reactants, pouring DMF solution into 4L distilled water, and)503905 rapidly stirring to form white precipitate; continue stirring for 1 h, filter again, and wash the filter cake with ethanol for 3 times, and finally get the white powder of bibp (yield: about 75.0%). 400-MHz 'H NMR (à, CDCIs): 7.93(2H, s), 7.72(4H, d, 8.4), 7.51(4H, d, 8.7), 7.35(2H, s), 7.25(2H, s). step 2: synthesize {[Zn(bibp)2] -(CIO4)2(CHCI3)2(CH30H)} -(Zn-MOF): 3.6 mmol bibp and 1.8 mmol Zn (CIO4)2-6H20 are dissolved in the solvent respectively, then the two solutions are mixed and stirred at room temperature, and then filtered, and the filter cake is washed with ethanol; finally, ZN-MOF white powder is obtained by vacuum drying, and the yield is about 83%. step 3: preparing carbon aerogel CA-1NMOF: 40.0 mg of Zn-MOF white powder is pressed into round pieces, put into a tube furnace, heated to 1,000°C at the rate of 5 °C min” in nitrogen atmosphere, and naturally cooled to room temperature after 3 h of constant temperature to obtain 7.8 mg of strip-shaped monolithic carbon material, that is, carbon aerogel CA-1NMOF ("CA-1" stands for "carbon aerogel derived from the first MOF".

In the above method: in the step 2, 3.6 mmol of bibp and 1.8 mmol of Zn (ClO4)2-6H20 are dissolved in 100 mL of chloroform and 50 mL of methanol, respectively. The two solutions are mixed at room temperature and stirred for 4 h. The filter cake is washed with ethanol for three times, and then dried in vacuum at 80°C for 4 h to obtain Zn-MOF white powder.

In the step 3, the Zn-MOF white powder is pressed into a ® 6.0x0.9 mm disc at 6 MPa.

CA-1NMOF has excellent environmental protection and energy storage performance. 9.1 kg CA-1NMOF can absorb 1 ton of gasoline, and the oil absorption value reaches 109.9 g/g. After five cycles, it still maintains 90.1% absorption capacity. At the same time, CA- 1NMOF shows strong adsorption capacity of methylene blue, and 1 g Ca-1NMOF can purify 3.2 L of methylene blue solution. CA-1NMOF also has a high absorption efficiency for formaldehyde, and 1 g CA-1NMOF can absorb 0.1353 formaldehyde gas, which is higher than the formaldehyde absorption materials on the market, and can be directly popularized and applied. In addition, through the electrochemical performance test, tH&/503905 capacitance value of CA-1-NMOF is as high as 313 F g', and the corresponding symmetrical battery energy density reaches 20.7 Wh kg, and only 4.8% of the capacity value is lost after 10,000 cycles, which opens up a new era for the development of supercapacitors. Generally speaking, we obtained the first MOF-derived carbon aerogel

CA-1NMOF by simple wafer calcination method, which has a wide range of practical application values in oil spill, sewage treatment, formaldehyde purification and energy storage.

The application of carbon aerogel CA-1NMOF obtained by the present invention are described in detail below:

Zn-MOF presents a wave-like 2d (4,4) layer, and the wave-like 2d (4,4) layers are embedded with each other to form a microporous supramolecular structure that can accommodate chloride ions. Using Zn-MOF wafer as precursor, black rod-shaped block material is obtained by calcination in Na atmosphere, which shows sufficient mechanical strength and can be easily grasped by tweezers. The diameter of the rod-shaped block is almost the same as that of the Zn-MOF wafer, but its thickness is increased from 0.9 mm to 50.0 mm (FIG. 1). Compared with the wafer precursor, the derivative material expanded violently by about 55.6 times. Considering that the yield is only 19.5%, the density of the block is equivalent to 1/285 of that of Zn-MOF wafer. We accurately measured the density of the block as 5.6 mg-cm and the porosity as 98.3%. Its XRD shows two weak broad peaks at 25° and 44°, corresponding to the (002) and (101) diffraction peaks of carbon (FIG. 2a). The Raman spectra of black blocks show D and G peaks of carbon materials at 1,355 and 1,590 cm”! (FIG. 2b). In addition, XPS spectrum strongly shows the peak of C1s at 284.2eV and another weak O1s peak at 531.5eV (FIG. 2c). Therefore, it is a light and porous carbon block material doped with oxygen. The bulk shape, extremely low density and high porosity show that we successfully prepared a kind of carbon aerogel by pyrolysis of Zn-MOF wafer at high temperature, and named it

CA-1NMOF. Although there are many strategies to synthesize carbon aerogel, such as template method, supercritical drying method and freeze drying method, the existing methods all need a long time and consume a lot of liquid to prepare the master gel or remove the template. Significantly, our wafer calcination process is very simple and fagtJy503905 and the most important thing is that no solvent is needed. In addition, our raw materials are very cheap, and the cost of synthesizing CA-1NMOF in a small laboratory is $2.6/gram. Although perchlorate ion is potentially explosive, this experiment has been carried out safely for 2 years and 1,000 times without any safety accidents. Generally speaking, we found a simple, rapid, solvent-free and low-cost synthesis method of carbon aerogel.

The porosity of CA-1NMOF is first characterized by nitrogen adsorption/desorption experiments at 77 K, showing a classic type Il adsorption curve (FIG. 3). The adsorption capacity of gas increases sharply with the increase of pressure, and reaches a high value at very low pressure, which means that there are a large number of micropores in CA- 1NMOF. Starting from 0.01P0, because the adsorption rate of mesopores is slower than that of micropores, the adsorption curve becomes gentle and the adsorption capacity gradually increases. When the pressure rises to 0.70Po, the mesopores are also saturated with nitrogen, and the macropores begin to fill with gas, which further reduces the adsorption rate. However, when the pressure is close to Po, the gas adsorption capacity increases abnormally, which is caused by capillary condensation effect of macropores. Interestingly, during the desorption process, there is an obvious H3 hysteresis curve between 0.4P, and Po, indicating that CA-1NMOF has macropores, mesopores and micropores at the same time. According to the t-plot algorithm, the BET specific surface area of CA-1NMOF is 1,515.2 m? g‘', the pore volume of BJH is 1.39 cm? g”, and the micropore volume is 0.13 cm? g”. Obviously, the pore volume of CA-1NMOF is mainly composed of mesopores and macropores. From the pore size distribution diagram, there are two peaks at 1.5 nm and 3.3 nm, which confirms the existence of micropores and mesopores in CA-1NMOF. In addition, mesopores and macropores are widely distributed in the range of 20-200 nm, and the most probable pore size exists between 80-200 nm.

In order to better understand the macroporous structure in CA-1NMOF, we conducted mercury intrusion test. As shown in FIG. 4, mercury vapor is easily pressed into CA- 1NMOF at low pressure, and the amount of mercury pressed increases rapidly. When the pressure reaches 25 psia, the super-large pores begin to saturate, and mercury vapbi)503905 enters the macropores, and there is an obvious inflection point on the mercury injection curve. We tried to inject mercury vapor into the intermediate hole by further increasing the pressure. However, when the pressure reached 3,000 psia, the aerogel frame began to collapse. Therefore, we only completed the mercury injection experiment at 2,500 psia, and then carried out the mercury removal experiment. Obviously, the mercury removal value is larger than the corresponding mercury injection value. This is because when the pressure is relieved, the stress disappears and the hole expands, which in turn leads to the increase of steam filling. According to the pore size distribution, there are two large pores at 120.9 nm and 183.1 nm. In addition, we also found a super-large pore of 8.1 um, revealing the highly crosslinked aerogel structure in CA-1NMOF.

In order to explain the multi-stage pore structure intuitively, we studied the morphology of

CA-1NMOF by field emission scanning electron microscope. A thin slice is cut from the block CA-1NMOF. At low resolution, it is found that the block structure is very loose, just like a sponge (FIG. 5a). Through further amplification, we observed that CA-1NMOF is composed of carbon sheets and fibers, and abundant super-large pores run through it.

Interestingly, the flakes and fibers are covered with bubbles, making them look like screens and slubs (FIG. 5b). These sheets and fibers are assembled into some cages, and wormlike macropores under the carbon substrate can be vaguely observed (FIG. 5c).

At the maximum resolution, we clearly captured the macropore structure hidden on the inner surface (FIG. 5d). Finally, EDX spectrum only shows C and O elements, and

Mapping reveals that these two elements are uniformly distributed in CA-1NMOF.

Then we studied the fine structure of CA-1-NMOF at nanometer scale by high resolution transmission electron microscope. First of all, we see that there are a large number of medium/large pores in the carbon matrix, and the sheets are interconnected by carbon fibers (FIG. 6a). Through further amplification, we found that the macropore size is mainly in the range of 80-200 nm (FIG. 6b). We selected the red circle region for selective electron diffraction, and the results showed that there are two bright diffraction rings and one dim diffraction ring (FIG. 6c), corresponding to the (002), (101) and (110) crystal planes of graphite material, respectively, indicating that CA-1NMOF had a certain degree of crystallinity. More significantly, we have obtained a high-resolution image of Judk/503905

Zhang, which is full of stripe structures, and the spacing of 0.34 nm is just the plane spacing of graphite (002) crystal planes (FIG. 6d). Therefore, CA-1NMOF exhibits short- range ordered and long-range disordered graphite structure. 1. Carbon aerogel CA-1NMOF cleans up oil spill:

CA-1NMOF is super-hydrophobic, with a contact angle of 121.1° in water. It can always float on the water surface, but it will be immediately immersed in organic solvents. We have tested the oil absorption value Qm (the ratio of absorbed weight to initial weight) of

CA-1NMOF for various organic solvents and oils, which is in the range of 74.3-212.0 g/g (Table 1). It is found that the liquid density has a great influence on the oil absorption value, but it is not a simple proportional relationship. In order to eliminate the influence of density, we divide Qm by density to get Qu, and the dispersion range is 98.2-134.9 mL/g.

According to the pore volume of CA-1NMOF of 175.5 mL/g, we calculated that the pore utilization rate is 55.9- 76.8%, which is far from 100%, because the gas in the nanopore is difficult to be completely eliminated by simple soaking. Significantly, the oil absorption capacity of CA-1NMOF is 109.9 g/g, and the absorption speed is very fast. 0.3 mL of oil can be completely absorbed by 2.8 mg of CA-1NMOF within 8 seconds. It is worth noting that the price of CA-1NMOF is very low compared with graphene or carbon nanotube aerogel. Less than 9.1 kg of CA-1NMOF can absorb 1 ton of oil, and its cost is about $23,600 according to the scale of small laboratory. In addition, the oil-saturated CA- 1NMOF is easily ignited in the air, and the CA-1NMOF that removes oil by combustion can be reused. After 8 cycles, CA-1NMOF still maintains 87.1% oil absorption capacity.

Therefore, CA-1NMOF has a broad application prospect in dealing with oil spill.

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2. Adsorption of pollutants by CA-1NMOF in carbon aerogel: LU503905

Dyes are widely used in textile industry, and they are discharged at will, causing serious pollution to rivers and lakes. We evaluated the adsorption capacity of CA-1NMOF for methylene blue (MB). When CA-1NMOF is added, the MB solution gradually faded (FIG. 7a), and we tracked the decoloration process by using UV-Vis spectrum. As shown in

FIG. 7b, with the passage of time, the maximum absorbance of MB solution gradually decreased, and it is basically colorless after 48 h, which indicated that CA-1NMOF had significant MB adsorption activity. We calculated the adsorption efficiency according to the following formula:

Adsrption efficiency (%) = (Co-C)/Co x 100%.

According to the initial and final concentration, about 97.5% MB molecules are adsorbed after 48 h, which is much better than many photocatalytic degradation MB decolorization effects. Generally speaking, MB molecules are difficult to be completely degraded into carbon dioxide and water by catalysts, and most of them will be converted into other toxic substances, especially reduced to colorless H2MB molecules. Even if a small part of the catalyst can be completely degraded, it will be accompanied by sulfate and nitrate ions, resulting in secondary pollution. In addition, almost all photocatalysts used for dye degradation are metal compounds, and heavy metal pollution is inevitable in the degradation process. However, the carbon material CA-1NMOF is more stable and healthier. After MB adsorption, it can be completely filtered out to obtain pure harmless liquid. 1.0 g CA-1NMOF is enough to remove 3.2 L MB waste liquid with a concentration of 5 mg L”*, and the cost is $2.6. Therefore, CA-1NMOF is a green adsorbent and has great application potential in dye pollution.

3. Carbon aerogel CA-1NMOF for air purification: LU503905

Strong carcinogenic formaldehyde is an important source of air pollution in new houses, and long-term inhalation of this toxic gas is very fatal. Porous CA-1NMOF has oxygen- doped elements, which is expected to provide adsorption sites for HCHO through hydrogen bonds. We use a dryer filled with 4.93 ppm HCHO to simulate a house polluted by formaldehyde gas. After testing, CA-1NMOF showed a very high uptake capacity of

HCHO (0.1353 g/g). Due to the very low concentration of HCHO and the interference of air, the experimental equilibrium time takes 4 days, but after 24 h, CA-1-NMOF can complete 86.3% saturated intake. According to the pore volume of CA-1NMOF, the packing density of HCHO in CA-1NMOF reached 757.68 mg L", which is about 1.54 x 10° times of the concentration of HCHO in the dryer. Therefore, CA-1NMOF can enrich and capture HCHO molecules. As shown in FIG. 8, CA-1NMOF not only has a reabsorption capacity (2.8 or 2.2 times), but also greatly exceeds the commercial HCHO purification materials purchased from Green Source Company and Green Source

Company. Significantly, HCHO adsorbed by CA-1NMOF can be discharged after slight heating (45°C) or sun exposure, and the uptake capacity of CA-1NMOF will be weakened after five cycles, which indicates that the uptake process of HCHO is completely reversible. Generally speaking, CA-1NMOF has the advantages of high intake of formaldehyde and good cycle stability, and can be directly extended to the formaldehyde purification market.

4. Carbon aerogel CA-1NMOF as supercapacitor: LU503905

According to XPS analysis, CA-1NMOF contains rich hydroxyl and carbonyl functional groups, which can form rich hydrogen bonds with hydroxyl ions in alkaline solution, and improve the hydrophilicity and wettability of CA-1NMOF. In addition, we measured the electrical conductivity of CA-1NMOF tablet by double probe method, which is 0.05 S-mm- 1 despite the existence of insulating PVDF adhesive, a large number of grain boundaries and contact resistance. The electrical conductivity of acetylene black tablets is 0.14

S-mm” by the same method. Acetylene black is a widely used conductive agent in supercapacitors, and CA-1NMOF has the same conductivity as acetylene black, which shows that CA-1NMOF is also a good conductive material. Therefore, we directly coated

PVDF-doped CA-1NMOF powder on nickel foam to test the performance of supercapacitors.

At first, we measured the CV curves of CA-1NMOF in 6M KOH solution with a three- electrode system at different scanning speeds (FIG. 9a). Rectangular CV curve shows the electric double layer capacitance behavior of the system. According to the following formula, the specific capacitance of a single electrode reaches 313 F g at a scanning speed of 5 mV s', which is much higher than that of most carbon materials. With the increase of scanning speed, at 10, 20, 50 and 100 mV s”!, the capacitance decreased to 300, 287, 267 and 253 F g”*, respectively, and the minimum capacitance is 81%. CA-1-

NMOF shows good rate performance. In addition, the CV curve has a redox at about -0.3

V. The electric pair can be attributed to Faradic reaction of oxygen-doped functional groups, which leads to a small amount of pseudo-capacitance behavior. Generally speaking, the excellent capacitance characteristics of CA-1-NMOF are the result of the synergistic effect of large specific surface area, high porosity, optimal pore size distribution (micro/meso/macroporous coexistence), good conductivity and appropriate O doping.

Csingle = Sare/2VAVM

For practical application, we assembled two equivalent CA-1-NMOF electrodes into a symmetrical electrical double-layer capacitor (SSC). In order to obtain a stable maximum working voltage, at the scanning speed of 50 mV s!, we gradually increased the voltad&/503905 window to conduct CV test on SSC. From 0.8 to 1.4 V, the CV curves all remain rectangular. When the potential window is 1.5 V, the CV curves begin to deform due to some irreversible reactions. Therefore, the optimal operating voltage is set to 1.4 V. We then carried out galvanostatic charge-discharge test (GCD) under different current densities (FIG. 9b). The GCD curve also shows the electric double layer capacitance characteristics of isosceles triangle. When the current density is 0.5, 1, 2, 5 and 10 g”, the specific capacitance (Ccer) of SSC is 76, 70, 66, 63 and 60 F g', respectively. At last, we calculated the energy density (ED, Wh Kg”) and power density (PD, W Kg”) of SSC, and drew a Ragone diagram (FIG. 9c). When SSC is 350 W kg", ED reaches 20.7 Wh kg‘. When PD rose sharply to 6,986 W kg, ED is still 16.3 Wh kg”. We compare SSC with the excellent carbon-based capacitors reported before, such as NPCs, 3DCN@BIC,

PGBC, NCGS and MWCNT/NPC. Our CA-1NMOF has obvious advantages in both energy density and power density. More significantly, SSC only loses 4.8% of its capacitance performance after 10,000 cycles, which proves that CA-1NMOF has perfect cycle stability (FIG. 9d). The synthesis of CA-1NMOF with high capacitance, excellent multiplying power and cyclic stability has opened up a new era for the development of

MOF-derived supercapacitors.

Cceu=1AtH/AVm

ED=0.5C(AV)¥3.6

PD=3600x SE/At

In the invention, a carbon aerogel CA-1-NMOF is prepared by calcining a Zn-MOF wafer, which has large specific surface area, extremely low density and ultra-high porosity. The cost of CA-1-NMOF is very low. On the scale of synthesis in a small laboratory, the cost of one gram is $2.6. More importantly, CA-1-NMOF has good practical application value in cleaning up oil spill, controlling dye pollution, formaldehyde purification and energy storage.

The content of the present invention is not limited to the embodiments listed, and any equivalent transformation of the technical scheme of the present invention taken by ordinary technicians in the field by reading the specification of the present invention 18503905 covered by the claims of the present invention.

Claims

CLAIMS LU503905

1. A method for preparing carbon aerogel based on MOFs wafer calcination, characterized by comprising the following steps: step 1, synthesizing 4,4'-bisimidazole biphenyl, which is called bibp; bibp is prepared by the copper-catalyzed N-arylation of azoles with aryl bromides: 800 mL DMF is added to the mixture of 120 mmol 4,4 -bisimidazole biphenyl, 480 mmol of imidazole, 6 mmol of Cul, 12 mmol of 1,10-phenanthroline and 600 mmol K2CO3, and the mixture is heated and refluxed for 4 days, then cooled to room temperature; filtering to remove solid reactant, pouring DMF solution into 4L distilled water, and rapidly stirring to form white precipitate; continue to stir for 1 h, filter again, and wash the filter cake with ethanol for 3 times to finally obtain white powder of bibp; step 2: increase the porosity of MOF-derived carbon materials by using the pore-forming effect of perchloric acid and zinc ions to synthesize {[Zn(bibp)z] (CIO4)2(CHCI3)2(CH30H)} >, Which is called Zn-MOF for short:

3.6 mmol of bibp and 1.8 mmol of Zn (Cl04)2-6H20 are dissolved in 100 mL of chloroform and 50 mL of methanol, respectively, and then the two solutions are mixed and stirred at room temperature, then filtered, and the filter cake is washed with ethanol; finally, vacuum drying to obtain Zn-MOF white powder; step 3: preparing carbon aerogel CA-1NMOF:

40.0 mg of Zn-MOF white powder is pressed into round pieces, put into a tube furnace, heated to 1,000°C at the rate of 5°C min” in nitrogen atmosphere, and naturally cooled to room temperature after 3 h, thus obtaining a strip-shaped monolithic carbon material, namely carbon aerogel CA-1NMOF.

2. The method for preparing carbon aerogel based on MOF s wafer calcination according to claim 1, characterized in that in step 2, two solutions are mixed at room temperature and then stirred for 4 h.

3. The method for preparing carbon aerogel based on MOFs wafer calcination according/503905 to claim 2, characterized in that in step 2, the filter cake is washed with ethanol for 3 times, and then dried in vacuum at 80°C for 4 h to obtain Zn-MOF white powder.

4. The method for preparing carbon aerogel based on MOF s wafer calcination according to claim 3, characterized in that in step 3, Zn-MOF white powder is pressed into a ® 6.0x

0.9 mm wafer at 6 MPa.

5. The method for preparing carbon aerogel based on MOFs wafer calcination according to claim 4, characterized in that in the step 3, the size of the strip-shaped monolithic carbon material is ® 6.0x50.0 mm.

6. A carbon aerogel obtained by the method for preparing carbon aerogel based on MOFs wafer calcination according to claim 5.

7. An application of the carbon aerogel in environmental protection according to claim 6, characterized in that: as a green adsorbent, the carbon aerogel is applied to the adsorption treatment of dye pollution, the purification of formaldehyde in the air and the treatment of oil leakage.

8. The application of carbon aerogel in energy storage according to claim 6, characterized in that: the carbon aerogel is used as an electrode material to prepare a supercapacitor, start a hybrid vehicle with high power, and supply power to precision instruments for a long time.