A photothermal MOF material based on anthraquinone derivatives, its preparation method and application

Abstract

The present invention discloses a photothermal MOF material based on anthraquinone derivatives and a preparation method thereof, belonging to the technical field of preparation of photothermal materials, and solving the problem of poor photothermal performance of traditional MOF materials. The photothermal MOF material uses zirconium ions as central atoms and forms coordination bonds with oxygen atoms of carboxylic acid ligands to form the photothermal MOF material; the carboxylic acid ligand is 9,10-anthraquinone-2,6-dicarboxylic acid. The visible light absorption rate of the photothermal MOF material of the present invention is greater than 60%; the maximum water adsorption capacity of the photothermal MOF material is above 900 cm<supgt;3< / supgt>·g<supgt;‑1< / supgt>, and it has both excellent photothermal performance and water adsorption capacity, and can be applied to the field of solar-driven atmospheric water collection technology.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of photothermal materials, and particularly relates to a photothermal MOF material based on anthraquinone derivatives, a preparation method thereof, and an application thereof. Background Art

[0002] In recent years, the problem of water resource shortage has become increasingly serious, threatening human health and life. Although people have taken measures such as seawater desalination and reverse osmosis, the effects are very limited in inland areas. Humidity in the atmosphere is one of the sources of fresh water. It is estimated that about 10 21 liters of water exists in the atmosphere on which we depend for survival in the form of steam and droplets, which is equivalent to 10% of the total amount of water in global lakes. If water vapor can be effectively collected, the problem of fresh water shortage will be greatly solved. In recent years, the adsorption-based atmospheric water collection technology has been widely studied due to its advantages such as low cost, easy operation, and being not restricted by geographical environment.

[0003] The adsorption-based atmospheric water collection technology has the following advantages: 1. Water resources can be collected anywhere: The adsorption-based atmospheric water collection technology does not need to rely on traditional water resources such as groundwater or surface water. As long as there is water vapor in the atmosphere, water sources can be collected. Therefore, water resource development can be achieved anywhere. 2. Wide application range: The adsorption-based atmospheric water collection technology has a very wide application range and can collect water resources in various environments such as deserts, wastelands, and the ocean. 3. Low energy consumption: Compared with traditional water resource development methods, the adsorption-based atmospheric water collection technology has lower energy consumption because it does not require a large amount of energy-consuming processes such as pumping and water conveyance. 4. Environmentally friendly: The adsorption-based atmospheric water collection technology has very little impact on the environment. Compared with the exploitation of groundwater or surface water, it reduces the damage to the environment.

[0004] Among many adsorbents, metal-organic framework materials (MOFs) have become one of the most promising adsorbents in the field of atmospheric water collection due to their advantages such as large specific surface area and adjustable structural properties. For the application of MOF materials in atmospheric water collection technology, they need to meet the advantages of high adsorption capacity, good hydrophilicity, fast adsorption and desorption, and good cycle stability.

[0005] Previously, researchers mainly improved the hydrophilicity and adsorption capacity of materials through structural design, synthesizing MOF materials with hydrophilic microporous networks, introducing hydrophilic functional groups (such as -OH, -NH2, -COOH), introducing nitrogen / oxygen / sulfur atoms to increase the polarity of the materials, or composite methods. Or through external auxiliary measures: such as radiative cooling, increasing light intensity, using heat-insulating substances to promote water desorption, often ignoring the research on the photothermal properties of MOF materials, which is not conducive to directly realizing solar-driven atmospheric water collection.

[0006] MOFs materials are porous frameworks formed by the coordination between metal centers or metal clusters and organic ligands. As a result, many MOFs materials do not exhibit the surface plasmon resonance effect of metal materials, nor do they have a unique band structure like semiconductor materials, which can achieve electron-hole transfer and strong light absorption. Therefore, they show poor photothermal performance. In addition, although some photothermal MOFs materials have been reported, these materials often introduce large hydrophobic organic ligands, such as porphyrin rings and benzopyrenes, which prevent water molecules from approaching the metal center, thus affecting the water absorption performance of MOFs materials. The above limitations make it challenging to achieve MOFs materials with both good photothermal performance and water absorption performance.

[0007] Therefore, it is necessary to develop a new type of photothermal MOFs material that exhibits excellent water absorption performance during the adsorption stage and excellent photothermal performance during the desorption stage, achieving a high solar energy utilization rate and enabling rapid desorption of water through the photothermal-heating effect without additional energy input. Summary of the Invention

[0008] Aiming at the problem of poor photothermal performance of MOFs materials in the prior art, the present invention provides a photothermal MOFs material based on anthraquinone derivatives and its preparation method. This MOFs material combines excellent photothermal performance and water absorption performance.

[0009] The technical solution adopted by the present invention is as follows:

[0010] A photothermal MOFs material based on anthraquinone derivatives, with zirconium ions as the central atoms, forms coordination bonds with the oxygen atoms of carboxylic acid ligands to form the photothermal MOFs material; the carboxylic acid ligand is 9,10-anthraquinone-2,6-dicarboxylic acid.

[0011] The structure of the 9,10-anthraquinone-2,6-dicarboxylic acid is shown in formula (I):

[0012]

[0013] The photothermal MOFs material of the present invention uses metal zirconium ions as the central atoms and forms coordination bonds with the oxygen atoms on the carboxylic acid ligands, thereby forming metal centers and organic ligands. Among them, the secondary building units (SBUs) of metal zirconium salts have a high coordination number and connectivity, and can form a stable structure with carboxylic acid ligands. Since 9,10-anthraquinone-2,6-dicarboxylic acid (DDD) contains multiple conjugated structures, with a relatively large π electron density, it is easy to absorb visible light and ultraviolet light, and has good light absorption ability after forming ligands. In addition, DDD also has a high molar absorptivity, which is beneficial to absorbing light energy; at the same time, DDD is used as a precursor to synthesize MOFs materials, which can combine excellent photothermal performance and water adsorption ability, and thus can be applied to the field of solar-driven atmospheric water collection.

[0014] Preferably, the visible light absorption rate of the photothermal MOF material is greater than 60%; the water adsorption capacity of the photothermal MOF material is 900 cm 3 ·g -1 or more.

[0015] Preferably, the particle size of the photothermal MOF material is 50 - 100 nm.

[0016] The present invention also provides a method for preparing the photothermal MOF material, including: dispersing a zirconium metal salt, 9,10 - anthraquinone - 2,6 - dicarboxylic acid, and a regulator into an organic solvent, heating for reaction, and then washing and drying to obtain the photothermal MOF material.

[0017] In the preparation method of the present invention, by controlling the ratio of the zirconium metal salt and the carboxylic acid ligand, the regulator concentration, the reaction temperature, and the reaction time, the crystallinity, morphology, light absorption ability, and water adsorption capacity of the photothermal MOF material can be regulated.

[0018] Preferably, the ratio of 9,10 - anthraquinone - 2,6 - dicarboxylic acid, the zirconium metal salt, and the organic solvent is 0.5 - 1.5 mg: 0.4 - 1.25 mg: 1 mL.

[0019] Preferably, the zirconium metal salt is zirconium tetrachloride; the organic solvent is N,N’ - dimethylacetamide.

[0020] Preferably, the regulator is glacial acetic acid and / or trifluoroacetic acid; the volume ratio of the regulator to the organic solvent is 0.05 - 0.16: 1.

[0021] When the heating reaction temperature is relatively low, the synthesized photothermal MOF material has poor crystallinity and serious agglomeration between particles; as the heating reaction temperature increases, the crystallinity and particle dispersion of the synthesized photothermal MOF material improve, but when the heating reaction temperature is too high, the crystallinity of the photothermal MOF material decreases and the particles become irregular. Therefore, too low or too high heating reaction temperature is not conducive to the growth of the photothermal MOF material.

[0022] Preferably, the heating reaction temperature is 120 - 180 °C, and the reaction time is 1 - 3 days.

[0023] More preferably, the heating reaction temperature is 140 - 160 °C, and the reaction time is 2 - 3 days; most preferably, the heating reaction temperature is 150 °C, and the reaction time is 3 days.

[0024] The photothermal MOF material of the present invention has both excellent photothermal performance and water absorption performance. Based on this, the present invention also provides an application of the photothermal MOF material in atmospheric water collection.

[0025] Preferably, solar energy is used to drive dehydration in atmospheric water harvesting.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] (1) During the synthesis of MOFs, zirconium metal ions serve as central atoms and form coordination bonds with oxygen atoms on carboxylic acid ligands, thus constituting metal centers and organic ligands. The SBUs of zirconium metal salts have high coordination numbers and connectivity and can form stable structures with carboxylic acid ligands. Since DDD contains multiple conjugated structures, it has good light absorption ability after forming ligands. Among them, the π electron density is relatively large, making it easy to absorb visible light and ultraviolet light. In addition, DDD also has a high molar absorptivity, which is conducive to absorbing light energy. When applied to the field of solar-driven atmospheric water harvesting, it can absorb a large amount of sunlight and convert it into heat, enabling the adsorbed water molecules in the photothermal MOFs material to desorb rapidly, improving the desorption kinetics of the MOFs material and saving energy. At the same time, DDD is used as a precursor to synthesize MOFs materials, which can possess excellent photothermal performance and water adsorption capacity, and thus can be applied to the field of solar-driven atmospheric water harvesting.

[0028] (2) The photothermal MOFs material synthesized based on anthraquinone derivatives in the present invention has good thermal stability, and the decomposition temperature is greater than 400 °C, showing progressiveness compared with many MOFs materials reported in the literature that are prone to decomposition.

[0029] (3) The synthesized photothermal MOFs material of the present invention has a large specific surface area, the pore size distribution is in the micropore range, the MOFs particle size is small, and it contains abundant oxygen polar adsorption sites, which is conducive to full contact with water molecules in the air, reducing the diffusion resistance within and between crystals, and enabling a high water adsorption capacity and adsorption kinetics. Description of the Drawings

[0030] Figure 1 are X-ray diffraction pictures of the MOFs materials prepared in Examples 1-3 of the present invention at different temperatures;

[0031] Figure 2 are scanning electron microscope images of the MOFs materials prepared in Examples 1-3 of the present invention at different temperatures; Figures (a, b) correspond to Example 1, Figures (c, d) correspond to Example 2, Figures (e, f) correspond to Example 3, and the scales are 1 μm for (a, d), 300 nm for (b), 500 nm for (c), and 200 nm for (e, f);

[0032] Figure 3 is the Fourier infrared spectroscopy image of the MOFs material, ZrCl4, and DDD ligand prepared in Example 2 of the present invention;

[0033] Figure 4It is the thermogravimetric curve of the MOFs material prepared in Example 2 of the present invention;

[0034] Figure 5 It is the ultraviolet-visible-near-infrared absorption spectrum of the MOFs material prepared in Example 2 of the present invention;

[0035] Figure 6 It is the water vapor adsorption curve of the MOFs material prepared in Example 2 of the present invention;

[0036] Figure 7 They are the (a) nitrogen adsorption-desorption curve and (b) pore size distribution curve of the MOFs material prepared in Example 4 of the present invention;

[0037] Figure 8 They are the (a) carbon dioxide adsorption-desorption curve and (b) micropore size distribution curve of the MOFs material prepared in Example 4 of the present invention;

[0038] Figure 9 It is the water vapor adsorption curve of the MOFs material prepared in Example 4 of the present invention. Detailed implementation manners

[0039] The present invention will be further described in detail below in conjunction with the drawings and embodiments. It should be noted that the following embodiments are intended to facilitate the understanding of the present invention and do not limit it in any way.

[0040] Example 1

[0041] Weigh 45 mg of 9,10-anthraquinone-2,6-dicarboxylic acid (DDD) and 30 mg of ZrCl4 into 60 mL of DMA solution, ultrasonically mix them evenly, then add 4.5 mL of glacial acetic acid and further mix evenly. Transfer the above mixture to a 50 mL polytetrafluoroethylene inner liner, seal the reaction kettle, and then transfer it to an oven preheated to 120 °C for 3 days. After the reaction is completed, wash the product 3 times with DMA and ethanol respectively, centrifuge, and dry to obtain the Zr-MOFs material.

[0042] Example 2

[0043] Weigh 59.24 mg of 9,10-anthraquinone-2,6-dicarboxylic acid (DDD) and 46.6 mg of ZrCl4 into 60 mL of DMA solution, ultrasonically mix them evenly, then add 5.7 mL of glacial acetic acid and further mix evenly. Transfer the above mixture to a 50 mL polytetrafluoroethylene inner liner, seal the reaction kettle, and then transfer it to an oven preheated to 150 °C for 3 days. After the reaction is completed, wash the product 3 times with DMA and ethanol respectively, centrifuge, and dry to obtain the Zr-MOFs material.

[0044] Figure 3The Fourier infrared spectroscopy images of the MOFs material prepared in Example 2, ZrCl4 and DDD ligand. It can be seen that in the Zr-MOFs material, the vibrations related to ZrCl4 disappear. In addition, the C=O vibration corresponding to the DDD ligand changes, indicating that Zr 4+ coordinates with the carboxylic acid oxygen on the DDD ligand, further proving the successful synthesis of Zr-MOF. After thermogravimetric curve measurement ( Figure 4 ), the Zr-MOF synthesized in Example 2 has good thermal stability. At 400 °C, the mass loss is only about 10-15%, which is beneficial for application in atmospheric water harvesting under extreme environments.

[0045] The light absorption of the Zr-MOF synthesized in Example 2 in the visible light range is greater than 60% ( Figure 5 ), and the optical color is black-brown, indicating that it has good photothermal conversion ability and can effectively convert sunlight into heat. After water vapor adsorption curve measurement ( Figure 6 ), the maximum water adsorption capacity of the Zr-MOF synthesized in Example 2 is about 930 cm 3 ·g -1 , and the performance is better than the water vapor adsorption capacity of most reported MOFs materials, indicating that it has good application prospects in the field of atmospheric water harvesting.

[0046] Example 3

[0047] Weigh 70 mg of 9,10-anthraquinone-2,6-dicarboxylic acid (DDD) and 55 mg of ZrCl4 into 60 mL of DMA solution, ultrasonically mix evenly, and then add 5.7 mL of glacial acetic acid and further mix evenly. Transfer the above mixture to a 50 mL polytetrafluoroethylene liner, seal the reaction kettle, and then transfer it to an oven preheated to 180 °C and react for 3 days. After the reaction is completed, wash the product 3 times with DMA and ethanol respectively, centrifuge, and dry to obtain the Zr-MOFs material.

[0048] Figure 1 、 Figure 2 are the X-ray diffraction images and scanning electron microscope images of the MOFs materials synthesized in Examples 1-3 respectively. When the reaction temperature is 120 °C (Example 1), the synthesized MOFs material has poor crystallinity and serious agglomeration between particles ( Figure 2 in (a), (b)); when the temperature is raised to 150 °C (Example 2), the obtained MOFs material has the best crystallinity and the synthesized MOFs particles are relatively evenly dispersed ( Figure 2 in (c), (d)); when the temperature is further raised to 180 °C (Example 3), the crystallinity of the synthesized MOFs material decreases and the particles become irregular, indicating that too high synthesis temperature is not conducive to the growth of MOFs materials ( Figure 2In (e) and (f)), therefore, the optimal synthesis temperature is 150 °C and the reaction time is 3 days.

[0049] Example 4

[0050] Weigh 59.24 mg of 9,10-anthraquinone-2,6-dicarboxylic acid (DDD) and 46.6 mg of ZrCl4 into 60 mL of DMA solution, ultrasonically mix them evenly, then add 5.7 mL of trifluoroacetic acid and further mix evenly. Transfer the above mixture to a 50 mL polytetrafluoroethylene liner, seal the reaction kettle, and then transfer it to an oven preheated to 150 °C for reaction for 3 days. After the reaction is completed, wash the product 3 times with DMA and ethanol respectively, centrifuge, and dry to obtain the Zr-MOFs material.

[0051] The nitrogen and carbon dioxide adsorption isotherms of the Zr-MOF synthesized in Example 4 were tested ( Figure 7 , Figure 8 ), and the results showed that the Zr-MOF synthesized under this reaction condition had a high specific surface area of up to 366 m 2 ·g -1 , contained micropores in the structure, the pore diameters were concentrated in the range of 1.18 and 1.35 nm, and the pore volume was 0.49 cm 3 ·g -1 . The hydrophilic microporous network was more conducive to the formation of hydrogen bond networks during the water adsorption process, ultimately achieving continuous pore filling. The larger pore volume also provided a large amount of space for the storage of water molecules, which also indirectly proved that the excellent water adsorption performance of this MOFs material was closely related to its hydrophilic structure, indicating the feasibility of the present invention. In addition, the carbon dioxide adsorption isotherm showed that the carbon dioxide adsorption capacity of this material at 273 K was about 0.43 mmol·g -1 , the particle size was about 80 nm, and there were a large number of micropores in the structure.

[0052] Since trifluoroacetic acid was used as a regulator during the reaction, it would increase the hydrophobicity of the structure, resulting in a decrease in the water vapor adsorption performance of the synthesized MOFs material compared with that using glacial acetic acid (Example 2) as a regulator, only 339 cm 3 ·g -1 ( Figure 9 ). The above results showed that selecting a suitable regulator to regulate and optimize the structure of MOFs materials was beneficial to improving the water adsorption capacity and further applying it to the field of atmospheric water harvesting.

[0053] The above embodiments only represent the specific implementation manners of the present application. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the protection scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the technical solution of the present application, several variations and improvements can still be made, and these all belong to the protection scope of the present application.

Claims

1. Application of an anthraquinone derivative-based photothermal MOF material in atmospheric water collection, characterized in that, The described photothermal MOF material based on anthraquinone derivatives uses zirconium ions as the central atom, forming coordination bonds with the oxygen atoms of the carboxylic acid ligand to constitute the described photothermal MOF material; the carboxylic acid ligand is 9,10-anthraquinone-2,6-dicarboxylic acid; The preparation method of the described photothermal MOF material based on anthraquinone derivatives includes: Disperse metal zirconium salt, 9,10-anthraquinone-2,6-dicarboxylic acid and a regulator into an organic solvent, heat and react at 140 - 160 °C for 2 - 3 days, and then obtain the photothermal MOF material through washing and drying; The ratio of 9,10-anthraquinone-2,6-dicarboxylic acid, metal zirconium salt and organic solvent is 0.5 - 1.5 mg : 0.4 - 1.25 mg : 1 mL.

2. The application of the anthraquinone derivative-based photothermal MOFs material according to claim 1 in atmospheric water collection, characterized in that, The visible light absorption rate of the described photothermal MOFs material is greater than 60%; the water adsorption capacity of the described photothermal MOFs material is 900 cm 3 ·g -1 or more.

3. Use of the anthraquinone derivative-based photothermal MOF material according to claim 1 in atmospheric water collection, characterized in that, The metal zirconium salt is zirconium tetrachloride; the organic solvent is N,N'-dimethylacetamide.

4. Use of the anthraquinone derivative-based photothermal MOF material according to claim 1 in atmospheric water collection, characterized in that, The regulator is glacial acetic acid and / or trifluoroacetic acid; the volume ratio of the regulator to the organic solvent is 0.05 - 0.16 : 1.

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