Metal organic gel type composite adsorbent as well as preparation method and application thereof

Abstract

The invention relates to a metal organic gel type composite adsorbent as well as a preparation method and application thereof. The metal organic gel type composite adsorbent comprises metal organic gel and hygroscopic salt, the hygroscopic salt comprises any one or a combination of at least two of calcium chloride, magnesium chloride, sodium chloride, barium chloride, cesium chloride, lithium bromide, calcium bromide, magnesium bromide, sodium bromide, barium bromide or cesium bromide. According to the preparation method of the metal organic gel type composite adsorbent, synthesis conditions are mild, large-scale preparation is easy, a reaction product is blocky gel, a final product is a granular integral adsorbent after drying, the adsorbent has efficient water vapor adsorption capacity, and the adsorbent has good application prospects. The metal organic gel type composite adsorbent has excellent adsorption and desorption performance and good cycle stability on water vapor.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of air pollution purification, in particular to a metal-organic gel type composite adsorbent and a preparation method and application thereof. BACKGROUND

[0002] Water vapor is an important component in air, and is one of the important factors directly affecting the thermal comfort of personnel, air quality and the service life of electronic equipment. The suitable indoor environment relative humidity range in summer is 40-80%, and in winter is 30-60%. Traditional solid adsorbents such as molecular sieves and silica gel have the advantages of reliable adsorption life and low cost, but the adsorption capacity is limited and the regeneration temperature is high. New solid adsorbents such as metal-organic framework compounds (MOFs) have the advantages of structural adjustability and high specific surface area, but the synthesis process is complex and the technology is not mature. It should be particularly pointed out that the above-mentioned adsorbents are mostly powder adsorbents, and secondary forming treatment is mostly required before final application.

[0003] For humidity control, current research mainly focuses on the development of adsorbent materials (for example CN114917879A) and the forming of powder adsorbent materials (for example CN115364822B and CN119100838A). The two parts of work have a chronological relationship, especially represented by MOFs materials, the product is mostly in powder form (for example CN118994925A), and mechanical forming or adding binder is required for application, which will directly affect the adsorption performance of the adsorbent.

[0004] Considering the actual application requirements, it is less to directly prepare monolithic adsorbent and solve the problems of material development and material forming at the same time. At the same time, such adsorbent should have the advantages of simple synthesis process and excellent performance.

[0005] Therefore, how to develop a monolithic adsorbent with excellent adsorption performance and simple synthesis for humidity control in closed spaces such as indoor and in-vehicle has broad application prospects, and has become a technical problem to be solved at present. SUMMARY

[0006] To solve the above technical problems, the present application aims to provide a metal-organic gel type composite adsorbent and a preparation method and application thereof. The preparation method of the metal-organic gel type composite adsorbent has relatively mild synthesis conditions and is easy to prepare on a large scale. The reaction product is a block-shaped gel, and the final product is a granular monolithic adsorbent after drying, and has high water vapor adsorption capacity. Moreover, the metal-organic gel type composite adsorbent has excellent water vapor adsorption and desorption performance and good cycle stability.

[0007] To achieve the above object, the present application adopts the following technical solutions:

[0008] In a first aspect, the present application provides a metal organic gel type composite adsorbent, which comprises a metal organic gel and a hygroscopic salt; the hygroscopic salt comprises any one or a combination of at least two of calcium chloride, magnesium chloride, sodium chloride, barium chloride, cesium chloride, lithium bromide, calcium bromide, magnesium bromide, sodium bromide, barium bromide or cesium bromide, and typical but non-limiting combinations include a combination of calcium chloride and magnesium chloride, a combination of sodium chloride and barium chloride, a combination of cesium chloride and lithium bromide, a combination of calcium bromide, magnesium bromide and sodium bromide, a combination of sodium bromide, barium bromide and cesium bromide, a combination of calcium chloride, magnesium chloride, calcium bromide, magnesium bromide and sodium bromide, or a combination of sodium chloride, barium chloride, cesium chloride, lithium bromide, calcium bromide, sodium bromide and barium bromide.

[0009] The metal organic gel comprises an aluminum-based and / or iron-based metal organic gel.

[0010] The metal organic gel type composite adsorbent provided by the present application is a granular adsorbent, which is different from the traditional metal organic framework material MOFs, and the obtained granular material does not need to be additionally added with a binder for granulation, and is more convenient for direct application, while if the obtained material is in a powder form, a binder needs to be additionally added for granulation before use, and the performance of a part of the adsorbent is lost in the granulation process, and the adsorption capacity is reduced, and the present application avoids the problem of material performance loss.

[0011] Preferably, the metal organic gel type composite adsorbent is in a granular form with an average particle size of 0.2 cm-5 cm, for example, can be 0.2 cm, 0.5 cm, 1 cm, 1.5 cm, 2 cm, 2.5 cm, 3 cm, 3.5 cm, 4 cm, 4.5 cm or 5 cm, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0012] Preferably, the specific surface area of the metal organic gel type composite adsorbent is 500 m 2 / g-1500 m 2 / g, for example, can be 500 m 2 / g, 550 m 2 / g, 600 m 2 / g, 650 m 2 / g, 700 m 2 / g, 750 m 2 / g, 800 m 2 / g, 850 m 2 / g, 900 m 2 / g, 950 m 2 / g, 1000 m 2 / g, 1050 m2 / g, 1100 m 2 / g, 1150 m 2 / g, 1200 m 2 / g, 1250 m 2 / g, 1300 m 2 / g, 1350 m 2 / g, 1400 m 2 / g, 1450 m 2 / g or 1500 m 2 / g, but not limited to the listed values, other unlisted values within the range are also applicable.

[0013] In a second aspect, the present application provides a preparation method of the metal-organic gel type composite adsorbent according to the first aspect, the preparation method comprising the following steps:

[0014] Mixing the metal salt, the organic ligand, the hygroscopic salt and the solvent, and obtaining the metal-organic gel type composite adsorbent through a sol-gel reaction.

[0015] The present application prepares the metal-organic gel type composite adsorbent through a sol-gel method, and the hygroscopic salt is added in the mixing stage of raw materials for preparing the metal-organic gel, which promotes the formation of the metal-organic gel, and the hygroscopic salt is introduced in the mixing stage, so that the hygroscopic salt is more uniformly dispersed.

[0016] The preparation method provided by the present application has mild synthesis conditions, simple preparation process and easy large-scale preparation.

[0017] The following is a preferred technical solution of the present application, but not as a limitation on the technical solutions provided by the present application, through the following preferred technical solution, the technical purpose and beneficial effects of the present application can be better achieved and realized.

[0018] Preferably, the molar ratio of the metal salt, the organic ligand, the solvent and the hygroscopic salt is 3:1-3:400-600:0-48, not including 0, for example, it can be 3:1:400:2, 3:2:400:2, 3:3:400:2, 3:1:500:2, 3:1:550:2, 3:1:600:2, 3:1:400:5, 3:2:400:10, 3:2:400:15, 3:3:400:20, 3:1:500:25, 3:1:550:30, 3:1:600:35, 3:1:400:40, 3:1:600:45 or 3:1:600:48, but is not limited to the listed values, other unlisted values within the value range are also applicable, preferably 3:1.8-2.2:450-550:1.5-9.

[0019] The present application further controls the molar ratio of the metal salt, the organic ligand, the solvent and the hygroscopic salt to be 3:1-3:400-600:0-48. If the content of the hygroscopic salt is too much, the porous structure of the metal organic gel cannot limit the salt, and after the salt absorbs water, the "salt overflow" phenomenon is easy to occur, and the overflowed salt solution is harmful to metal devices or human body. If the content of the hygroscopic salt is too little, the water vapor adsorption amount is greatly reduced, and the hygroscopic salt plays a role of a structure directing agent, interfering with the nucleation process of the metal organic gel. The addition of an appropriate amount of salt can make the product powder more uniform.

[0020] Preferably, the metal salt includes an aluminum salt and / or an iron salt.

[0021] Preferably, the metal salt is a single aluminum salt or a single iron salt or the molar ratio of the aluminum salt and the iron salt is 1:1 and 2:1.

[0022] Preferably, the aluminum salt includes any one or a combination of at least two of aluminum nitrate, aluminum chloride, aluminum bromide, aluminum sulfate or aluminum acetate, typical but non-limiting combinations include a combination of aluminum nitrate and aluminum chloride, a combination of aluminum chloride and aluminum bromide, a combination of aluminum bromide and aluminum sulfate, a combination of aluminum sulfate and aluminum acetate, a combination of aluminum nitrate and aluminum bromide, a combination of aluminum chloride, aluminum bromide and aluminum acetate, or a combination of aluminum nitrate, aluminum chloride, aluminum bromide, aluminum sulfate and aluminum acetate, preferably aluminum nitrate.

[0023] Preferably, the iron salt includes any one or a combination of at least two of iron nitrate, iron chloride or iron sulfate, typical but non-limiting combinations include a combination of iron nitrate and iron chloride, a combination of iron chloride and iron sulfate, a combination of iron nitrate and iron sulfate, a combination of iron nitrate, iron chloride and iron sulfate.

[0024] Preferably, the organic ligand further includes a tridentate ligand and / or a bidentate ligand.

[0025] Preferably, the tridentate ligand comprises 3,5-pyridinedicarboxylic acid.

[0026] Preferably, the bidentate ligand comprises any one or a combination of at least two of terephthalic acid, isophthalic acid, 2,5-pyridinedicarboxylic acid or 2,6-pyridinedicarboxylic acid.

[0027] The present application uses trimesic acid as the main ligand, assisted by other organic ligands, a typical but non-limiting combination includes a combination of trimesic acid and 3,5-pyridinedicarboxylic acid, a combination of trimesic acid and isophthalic acid.

[0028] In the present application, trimesic acid as a tridentate ligand, its three carboxyl groups can form a stable three-dimensional network with Al³⁺ and Fe³⁺ through "chelation-bridging" dual action: when coordinated with Al³⁺, the three carboxyl groups of each trimesic acid molecule can form a bidentate chelate structure with two Al³⁺ respectively, theoretically 3 trimesic acid molecules can be fully coordinated with 2 Al³⁺, at this time the gel network has the highest crosslinking density and the most stable porous structure; similarly, when coordinated with Fe³⁺, due to the similar coordination geometry and the close ion radius of Fe³⁺ (0.645 Å) and Al³⁺ (0.535 Å), the optimal ratio is also 3:2. Taking 3,5-pyridinedicarboxylic acid (tridentate ligand) as an example, due to the electronic effect of the pyridine ring, a small amount of auxiliary ligand can enhance the coordination ability of the ligand and the metal ion.

[0029] Preferably, the solvent comprises ethanol and / or an ethanol aqueous solution, preferably ethanol.

[0030] The selected solvent of the present application further preferably comprises ethanol and / or an ethanol aqueous solution, wherein ethanol plays a dual role of solvent and crosslinking. Trimesic acid and ethanol form a porous crosslinked network through hydrogen bonding, Π-Π stacking and van der Waals bonding to obtain a gel, which can be dried to obtain a particulate metal-organic gel-type composite adsorbent. Other solvents, such as methanol, propanol or water, etc., cannot react to obtain a gel, and subsequent particulate metal-organic gel-type composite adsorbents cannot be obtained, and the adsorption performance of the obtained product is also significantly poorer. Commonly used organic solvents such as N,N-dimethylformamide and dimethyl sulfoxide affect the coordination rate of metal ions and ligands due to their strong polarity, and under the same reaction conditions, gels cannot be obtained. Considering that N,N-dimethylformamide and dimethyl sulfoxide are harmful to the environment and the human body, pure ethanol is still preferred.

[0031] Preferably, the hygroscopic salt comprises any one or a combination of at least two of lithium chloride, calcium chloride or lithium bromide, a typical but non-limiting combination includes a combination of lithium chloride and calcium chloride, a combination of calcium chloride and lithium bromide, a combination of lithium chloride and lithium bromide, a combination of lithium chloride, calcium chloride and lithium bromide.

[0032] Preferably, the temperature of the sol-gel reaction is 100-150℃, for example, it can be 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃, 140℃, 145℃ or 150℃, but is not limited to the listed values, other values not listed in the range of values are also applicable.

[0033] Preferably, the time of the sol-gel reaction is 2-12h, for example, it can be 2h, 4h, 6h, 8h, 10h or 12h, but is not limited to the listed values, other values not listed in the range of values are also applicable.

[0034] Preferably, the reaction container of the sol-gel reaction is a closed steel or glass reaction kettle with a polytetrafluoroethylene liner or a polytetrafluoroethylene gasket.

[0035] Preferably, after the sol-gel reaction, drying is further included before obtaining the metal-organic gel type composite adsorbent.

[0036] Preferably, the drying is by means of baking and / or freeze-drying.

[0037] Preferably, the temperature of the baking is 50-100℃, for example, it can be 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃ or 100℃, but is not limited to the listed values, other values not listed in the range of values are also applicable.

[0038] Preferably, the time of the baking is 2-12h, for example, it can be 2h, 4h, 6h, 8h, 10h or 12h, but is not limited to the listed values, other values not listed in the range of values are also applicable.

[0039] Preferably, the temperature of the freeze-drying is -60℃ to -80℃, for example, it can be -60℃, -65℃, -70℃, -75℃ or -80℃, but is not limited to the listed values, other values not listed in the range of values are also applicable.

[0040] Preferably, the time of the freeze-drying is 4-24h, for example, it can be 4h, 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h or 24h, but is not limited to the listed values, other values not listed in the range of values are also applicable.

[0041] As a preferred technical solution of the preparation method of the present application, the preparation method comprises the following steps:

[0042] Mixing aluminum nitrate nonahydrate, trimesic acid, hygroscopic salt and ethanol according to the molar ratio of 3:1.8-2.2:1.5-9:450-550, sol-gel reaction at 100-150℃ for 2-12h, drying at 50-100℃ for 2-12h, to obtain a metal organic gel type composite adsorbent.

[0043] In a third aspect, the present application provides a use of the metal organic gel type composite adsorbent according to the first aspect for water vapor adsorption.

[0044] The metal organic gel type composite adsorbent provided by the present application exhibits excellent adsorption and desorption performance and good cycle stability for water vapor at room temperature. The adsorption amount of water vapor reaches 1.07g / g at room temperature 25℃ and relative humidity 80%; the adsorption amount of water vapor is as high as 3.31g / g at room temperature 25℃ and relative humidity 95%, and in particular, the performance of the adsorbent can still maintain more than 90% of the initial performance after 30 cycles, which exhibits extremely excellent adsorption performance compared with molecular sieves, pure MOFs and other adsorbents.

[0045] The numerical range described in the present application includes not only the point values listed above, but also any point values between the above numerical ranges that are not listed, and the present application does not exhaustively list the specific point values included in the range for the sake of brevity and simplicity.

[0046] Compared with the prior art, the present application has at least the following beneficial effects:

[0047] (1) The metal organic gel type composite adsorbent provided by the present application is a granular adsorbent, which is different from the traditional metal organic framework material MOFs, and the obtained granular material does not need to be additionally added with a binder for granulation, and is more convenient for direct application, while if the obtained material is in powder form, a binder needs to be additionally added for granulation before use, and the performance of a part of the adsorbent will be lost during the granulation process, and the adsorption capacity is reduced, and the present application avoids the problem of material performance loss.

[0048] (2) The metal organic gel type composite adsorbent is prepared by a sol-gel method, and the hygroscopic salt is added during the mixing stage of the raw materials for preparing the metal organic gel, and the hygroscopic salt promotes the generation of the metal organic gel, and the hygroscopic salt is introduced during the mixing stage, so that the hygroscopic salt is more uniformly dispersed; compared with the process of adding the hygroscopic salt after preparing the metal organic gel and then mixing separately, the preparation process is simplified, and the adsorption performance and cycle stability of the obtained metal organic gel type composite adsorbent are more excellent.

[0049] (3) The metal organic gel type composite adsorbent provided by the application has excellent adsorption and desorption performance and good cycle stability for water vapor. The adsorption amount of water vapor is 1.07 g / g under the condition of room temperature 25 DEG C and relative humidity 80%; the adsorption amount of water vapor is as high as 3.31 g / g under the condition of room temperature 25 DEG C and relative humidity 95%. In particular, the performance of the adsorbent can still be maintained at more than 95% of the initial performance after 30 cycles, which shows extremely excellent adsorption performance compared with molecular sieves, pure MOFs and other adsorbents. BRIEF DESCRIPTION OF DRAWINGS

[0050] Figure 1 is the nitrogen adsorption and desorption curve of the metal organic gel type composite adsorbent prepared in Example 1 and Comparative Example 1 of the application;

[0051] Figure 2 is the pore size distribution graph of the metal organic gel type composite adsorbent prepared in Example 1 and Comparative Example 1 of the application;

[0052] Figure 3 is the optical photograph of the metal organic gel type composite adsorbent prepared in Example 1 of the application;

[0053] Figure 4 is the optical photograph of the metal organic gel type composite adsorbent prepared in Comparative Example 1 of the application;

[0054] Figure 5 is the cycle stability performance graph of the metal organic gel type composite adsorbent prepared in Example 1 of the application;

[0055] Figure 6 is the cycle stability performance graph of the metal organic gel type composite adsorbent prepared in Comparative Example 2 of the application. DETAILED DESCRIPTION

[0056] The technical solutions of the application will be further described below by specific embodiments in combination with the drawings. However, the following examples are only simple examples of the application and do not represent or limit the protection scope of the application, and the protection scope of the application is subject to the claims.

[0057] In the following examples and comparative examples, all reagents and consumables are purchased from conventional reagent manufacturers in the field unless otherwise specified; and the experimental methods and technical means used are conventional methods and means in the field unless otherwise specified.

[0058] Example 1

[0059] The embodiment provides a metal organic gel type composite adsorbent, which comprises metal organic gel and hygroscopic salt lithium chloride;

[0060] The preparation method of the metal organic gel type composite adsorbent includes the following steps:

[0061] The aluminum nitrate nonahydrate, trimesic acid, lithium chloride and ethanol are mixed in a molar ratio of 3:2:3:500, a sol-gel reaction is performed at 120°C for 4h, the product is placed in a vacuum drying oven, and is dried at 65°C for 8h to obtain the metal organic gel type composite adsorbent.

[0062] Example 2

[0063] The present example provides a metal organic gel type composite adsorbent, which includes a metal organic gel and a hygroscopic salt calcium chloride;

[0064] The preparation method of the metal organic gel type composite adsorbent includes the following steps:

[0065] The aluminum chloride, trimesic acid, calcium chloride and ethanol are mixed in a molar ratio of 3:2:3:450, a sol-gel reaction is performed at 100°C for 6h, the product is placed in a freeze-drying oven, and is dried at -80°C for 12h to obtain the metal organic gel type composite adsorbent.

[0066] Example 3

[0067] The present example provides a metal organic gel type composite adsorbent, which includes a metal organic gel and a hygroscopic salt lithium bromide;

[0068] The preparation method of the metal organic gel type composite adsorbent includes the following steps:

[0069] The aluminum bromide, trimesic acid, lithium bromide and ethanol are mixed in a molar ratio of 3:2:1.5:600, a sol-gel reaction is performed at 120°C for 4h, the product is placed in a vacuum drying oven, and is dried at 80°C for 6h to obtain the metal organic gel type composite adsorbent.

[0070] Example 4

[0071] The present example provides a preparation method of a metal organic gel type composite adsorbent, which is different from that of Example 1 only in that the aluminum nitrate nonahydrate in Example 1 is replaced by a mixture of equal molar amounts of aluminum nitrate nonahydrate and ferric nitrate nonahydrate (the molar ratio of aluminum nitrate nonahydrate to ferric nitrate nonahydrate is 1:1).

[0072] Example 5

[0073] The present example provides a preparation method of a metal organic gel type composite adsorbent, which is different from that of Example 1 only in that the molar ratio of aluminum nitrate nonahydrate, trimesic acid and lithium chloride is 3:2:0.01.

[0074] Example 6

[0075] The embodiment provides a preparation method of a metal organic gel type composite adsorbent, and only difference from the embodiment 1 is that the molar ratio of aluminum nitrate nonahydrate, trimesic acid and lithium chloride is 3:2:50.

[0076] Embodiment 7

[0077] The embodiment provides a preparation method of a metal organic gel type composite adsorbent, and only difference from the embodiment 1 is that the ethanol solvent is replaced by methanol of equal molar amount.

[0078] Embodiment 8

[0079] The embodiment provides a preparation method of a metal organic gel type composite adsorbent, and only difference from the embodiment 1 is that the ethanol solvent is replaced by N,N-dimethylformamide of equal molar amount.

[0080] Comparative Example 1

[0081] The comparative example provides a preparation method of a metal organic gel type composite adsorbent, and only difference from the embodiment 1 is that the hygroscopic salt is not added.

[0082] The optical photograph of the prepared pure-phase metal organic gel type adsorbent is shown in the figure, and the inserted figure is a partial enlarged view, and the centimeter-level particles in yellow transparent irregular shape. Figure 4

[0083] Comparative Example 2

[0084] The comparative example provides a preparation method of a metal organic gel type composite adsorbent, and only difference from the embodiment 1 is that the hygroscopic salt is not added in the raw material before the sol-gel reaction, and the product obtained by mixing the dried product with equal amount of hygroscopic salt and ethanol solution after stirring for 2 hours is dried and prepared.

[0085] Comparative Example 3

[0086] The comparative example provides a preparation method of an adsorbent, and only difference from the embodiment 1 is that the aluminum nitrate nonahydrate and trimesic acid are replaced by MIL-100 (Al) MOFs material, that is, the MOFs material, the hygroscopic salt and the ethanol are directly mixed to obtain the adsorbent.

[0087] Test:

[0088] The metal organic gel type composite adsorbents prepared in the embodiment and the comparative examples are dried in a vacuum drying box at 100 DEG C for 4 hours, the adsorbent activation process before the adsorption test is completed, the test conditions are 25 DEG C, and the test is completed in the environment with relative humidity of 80% and 95% respectively, and the mass change of the adsorbent is recorded in real time. The test results are shown in the following table 1. ​

[0089] The nitrogen adsorption-desorption curves of the metal-organic gel composite adsorbents prepared in Example 1 and Comparative Example 1 are shown below. Figure 1 As shown in the figure, the pure metal-organic gel possesses a large specific surface area (~1393 m² / g) and pore volume (~1.020 cm³ / g), which is rare in previous studies on metal-organic gels. The pure metal-organic gel exhibits a type IV isotherm, rising sharply under low pressure (p / p0 < 0.1), and undergoing capillary condensation at p / p0 ~ 0.5, with the adsorption capacity gradually increasing. The presence of a hysteresis loop confirms the existence of mesopores. Both the pure metal-organic gel and the LiCl composite metal-organic gel adsorbent exhibit H₂a type hysteresis loops, indicating that they possess uniform mesopores, similar to the typical mesoporous material SBA-16, or have dense intergranular gaps.

[0090] The pore size distribution diagrams of the metal-organic gel composite adsorbents prepared in Example 1 and Comparative Example 1 are shown below. Figure 2 As shown in the figure, the metal-organic gel composite adsorbent exhibits a hierarchical pore structure of micropores and mesopores, confirming the layered porosity of the sample. The mesopore sizes of the pure metal-organic gel are approximately 5.2 nm and 7.0 nm. The incorporation of LiCl leads to a reduction in both micropore and mesopore volumes. This indicates that LiCl is uniformly distributed within both the internal micropores and interstitial mesopores formed during nanoparticle assembly. Furthermore, LiCl acts as a structure-directing agent; optimizing the LiCl content results in a more ordered mesopore distribution in the LiCl-composite metal-organic gel adsorbent.

[0091] Optical photographs of the metal-organic gel composite adsorbent prepared in Example 1 are shown below. Figure 3 As shown, compared to Figure 4 In Comparative Example 1, the composite particles were smaller and more uniform in size, and were white, indicating that the addition of an appropriate amount of salt could act as a structure guiding agent, promoting a more ordered gel system.

[0092] The cyclic stability experiment of the metal-organic gel composite adsorbent prepared in Example 1 is as follows: Figure 5 As shown, in the initial cycle, the adsorption capacity was 955 mg / g after 2 hours. After 30 cycles over a total duration of 5 days, the adsorption capacity remained at 895 mg / g, with an adsorption ratio as high as 94%. Meanwhile, desorption was carried out at 90℃ and 4% RH. The initial residual water vapor was about 121 mg / g, accounting for 12% of the initial adsorption ratio. After cycling, this value changed to a residual water vapor of about 85 mg / g, accounting for 9% of the initial adsorption ratio. This fully demonstrates the significant impact of adding hygroscopic salt first on the adsorption capacity and cycle stability of the composite adsorbent in Implementation Case 1.

[0093] The cycling stability performance of the metal-organic gel adsorbent prepared in Comparative Example 2 is shown in the figure below.Figure 6 As shown, in the initial cycle, the adsorption capacity of 2h is 800 mg / g, and after 30 cycles in a total duration of 5 days, the adsorption capacity can only be maintained at 610 mg / g, and the adsorption ratio decays to 76%; meanwhile, under the desorption condition of 90℃ and RH4%, the initial water vapor residual amount is about 154 mg / g, accounting for 19% of the initial adsorption ratio, and after the cycle, the value changes to a water vapor residual amount of about 116 mg / g, accounting for 15% of the initial adsorption ratio. It is fully proved that in the traditional impregnation method, i.e. in Comparative Example 2, the metal organic gel is synthesized first, and then the hygroscopic salt is impregnated, the porous network of the metal organic gel cannot well encapsulate the salt, and under the same load of the hygroscopic salt, the adsorption performance is much lower than that of Example 1.

[0094] Table 1

[0095]

[0096] From the test results, it can be seen that:

[0097] (1) From Example 1 to Example 4, it can be seen that the metal organic gel type composite adsorbent is prepared by the sol-gel method, the hygroscopic salt is added in the mixing stage of the raw materials in the preparation of the metal organic gel, the hygroscopic salt promotes the generation of the metal organic gel, and the hygroscopic salt is introduced in the mixing stage, so that the hygroscopic salt is more uniformly dispersed; compared with the process of adding the hygroscopic salt after the preparation of the metal organic gel and then mixing separately, not only is the preparation process simplified, but also the utilization rate of lithium chloride of the hygroscopic salt is higher, and at the same time, the adsorption performance of the obtained metal organic gel type composite adsorbent is more excellent; replacing lithium chloride with lithium bromide and other lithium salts can obtain a composite material with excellent water vapor adsorption performance; freeze-drying can retain the pores of the composite material through the direct sublimation of the condensed ethanol in the pores, but compared with direct drying, the process is more complicated, and the total energy consumption of the production process is greatly increased; replacing aluminum nitrate nonahydrate with an equimolar mixture of aluminum and iron salt will lead to competition between aluminum and iron for coordination, and the system disorder degree in the gel crosslinking process will increase, so pure aluminum salt is preferred.

[0098] (2) From Example 1 and Example 5 to Example 6, it can be seen that the molar ratio of the further metal salt, the organic ligand, the solvent and the hygroscopic salt is 3:1-3:400-600:0-48, if the content of the hygroscopic salt is too low, the water vapor adsorption amount will be greatly reduced, and at the same time, the hygroscopic salt plays a role of structure directing agent, which interferes with the nucleation process of the metal organic gel, and the addition of an appropriate amount of salt can make the product powder more uniform; if the content of the hygroscopic salt is too high, the porous structure of the metal organic gel cannot limit the salt, and after the salt absorbs water, the "salt overflow" phenomenon is easy to occur, and the overflowed salt solution is harmful to metal equipment or human body, and in Example 6, a serious "salt overflow" phenomenon occurs, and the adsorption performance of the material for repeated use will be greatly reduced.

[0099] (3) By comparing Example 1 with Examples 7-8, it can be seen that the solvent selected by the present application is further preferably composed of ethanol and / or an ethanol aqueous solution, wherein ethanol plays a dual role of solvent and crosslinking, and can enable the reaction to obtain a gel, and after drying, a particulate metal organic gel type composite adsorbent can be obtained. Other solvents, such as methanol, propanol or water, etc., cannot obtain a gel in the reaction, and cannot obtain a particulate metal organic gel type composite adsorbent subsequently, and the adsorption performance of the obtained product is also significantly poorer. Commonly used organic solvents such as N,N-dimethylformamide and dimethyl sulfoxide cannot obtain a gel under the same reaction conditions due to their strong polarity, which affects the coordination rate of metal ions and ligands. Considering that N,N-dimethylformamide and dimethyl sulfoxide are harmful to the environment and human body, pure ethanol is preferred.

[0100] (4) By comparing Example 1 with Comparative Example 1, it can be seen that the introduction of the hygroscopic salt not only greatly improves the water vapor adsorption amount, but also plays a role of a structure directing agent in the porous channel, optimizes the mesopore size distribution of the metal organic gel, makes the pore size more uniform, and improves the adsorption and desorption performance and good cycle stability of the metal organic gel type composite adsorbent.

[0101] (5) By comparing Example 1 with Comparative Example 2, it can be seen that the metal organic gel type composite adsorbent prepared by the sol-gel method in the present application is prepared by adding the hygroscopic salt in the raw material mixing stage of the preparation of the metal organic gel. The hygroscopic salt promotes the generation of the metal organic gel, and the hygroscopic salt is introduced in the mixing stage, so that the hygroscopic salt is more uniformly dispersed. Compared with adding the hygroscopic salt after the preparation of the metal organic gel and then carrying out a separate mixing process, the metal organic gel composite material prepared in Comparative Example 2 produces a large amount of waste ethanol or waste water, has low impregnation efficiency, has low utilization rate of the hygroscopic salt, and the process characteristics determine that the salt diffuses into the porous network of the metal organic gel from the outside to the inside. The salt is easy to be unevenly distributed, and is easy to form clusters in the neck region of the pore channel in the porous carrier, which affects the diffusion of water in the subsequent adsorption or desorption process, and seriously damages the adsorption kinetics. In contrast, Example 1 not only simplifies the preparation process, but also makes the adsorption performance of the obtained metal organic gel type composite adsorbent more excellent.

[0102] (6) As can be seen from Example 1 and Comparative Example 3, the present application can obtain a granular product by using ethanol or a mixture of ethanol and water as a reaction solvent, and then simply drying after hydrothermal reaction. In contrast, in Comparative Example 3 in which aluminum salt and trimesic acid are used as main reaction products, MOFs such as MIL-100(Al) or MIL-96(Al) need more stringent synthesis conditions, and the synthesis reagents are mostly dangerous reagents such as N,N-dimethylformamide and methanol. Similarly, after the synthesis of MOFs is completed, a mixing process of MOFs and a hygroscopic salt solution needs to be performed, and the same problems as in Comparative Example 2, such as uneven salt dispersion, low salt utilization rate, and poor kinetics, exist.

[0103] In summary, the metal-organic gel type composite adsorbent prepared by the sol-gel method of the present application has the following advantages: the hygroscopic salt is added in the mixing stage of raw materials during the preparation of the metal-organic gel, the hygroscopic salt promotes the formation of the metal-organic gel, and the hygroscopic salt is introduced in the mixing stage, so that the hygroscopic salt is more uniformly dispersed, the hygroscopic salt acts as a hygroscopic component and a structure directing agent, greatly improves the water vapor adsorption capacity, makes the original mesopore size distribution of the metal-organic gel more regular, and greatly improves the cycle stability; the metal-organic gel type composite adsorbent has excellent water vapor adsorption and desorption performance and good cycle stability. The metal-organic gel type composite adsorbent provided by the present application is a granular adsorbent, which is different from the traditional metal-organic framework material MOFs, and the obtained granular material does not need to be additionally added with a binder for granulation, and is more convenient for direct application.

[0104] The applicant declares that the above description is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. It should be understood by those skilled in the art that any changes or replacements within the technical scope disclosed by the present application can be easily thought of by those skilled in the art, and all fall within the protection scope and disclosure scope of the present application.

Claims

1. A metal organic gel type composite adsorbent, characterized by, The metal organic gel type composite adsorbent comprises a metal organic gel and a hygroscopic salt; The hygroscopic salt comprises any one or a combination of at least two of calcium chloride, magnesium chloride, sodium chloride, barium chloride, cesium chloride, lithium bromide, calcium bromide, magnesium bromide, sodium bromide, barium bromide or cesium bromide; The metal organic gel comprises an aluminum-based and / or iron-based metal organic gel.

2. The metal organic gel type composite adsorbent according to claim 1, characterized by, The metal organic gel type composite adsorbent is in a granular form with an average particle size of 0.2 cm-5 cm. Preferably, the specific surface area of the metal-organic gel type composite adsorbent is between 500 m 2 / g and 1500 m 2 / g.

3. A method for producing the metal-organic gel type composite adsorbent according to claim 1 or 2, characterized by, The preparation method comprises the following steps: mixing a metal salt, an organic ligand, a hygroscopic salt and a solvent to obtain a metal organic gel type composite adsorbent through a sol-gel reaction; The organic ligand comprises trimesic acid.

4. The production method according to claim 3, characterized by, The molar ratio of the metal salt, the organic ligand, the solvent and the hygroscopic salt is 3:1-3:400-600:0-48, excluding 0. Preferably, the molar ratio of the metal salt, the organic ligand and the hygroscopic salt is 3:1.8-2.2:1.5-9.

5. The production method according to claim 3 or 4, characterized by, The metal salt comprises an aluminum salt and / or an iron salt; Preferably, the aluminum salt comprises any one or a combination of at least two of aluminum nitrate, aluminum chloride, aluminum bromide, aluminum sulfate or aluminum acetate, preferably aluminum nitrate; Preferably, the iron salt comprises any one or a combination of at least two of iron nitrate, iron chloride or iron sulfate, preferably iron nitrate; Preferably, the solvent comprises ethanol and / or an ethanol aqueous solution, preferably ethanol.

6. The method of any one of claims 3-5, wherein, The hygroscopic salt comprises any one or a combination of at least two of lithium chloride, calcium chloride or lithium bromide.

7. The method of any one of claims 3-6, wherein, The temperature of the sol-gel reaction is 100℃-150℃; Preferably, the time of the sol-gel reaction is 2h-12h.

8. The method of any one of claims 3-7, wherein, After the sol-gel reaction, drying is further included before obtaining the metal organic gel type composite adsorbent. Preferably, the drying is performed through baking and / or freeze-drying.

9. The method of any one of claims 3-8, wherein, The preparation method comprises the following steps: mixing aluminum nitrate nonahydrate, trimesic acid, a hygroscopic salt and ethanol according to a molar ratio of 3:1.8-2.2:1.5-9:450-550, performing a sol-gel reaction at 100℃-150℃ for 2h-12h, and baking at 50℃-100℃ for 2h-12h to obtain a metal organic gel type composite adsorbent.

10. Use of the metal organic gel type composite adsorbent according to claim 1 or 2, characterized in that, The metal organic gel type composite adsorbent is used for water vapor adsorption.

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