阅读说明：本技术 一种金属有机骨架mil-101的合成方法 (synthesis method of metal organic framework MIL-101 ) 是由 陈恒 张会良 张学伟 于 2019-08-09 设计创作，主要内容包括：本发明属于金属有机骨架合成技术领域,公开了一种金属有机骨架MIL-101的合成方法,包括以下步骤：1)依次向去离子水中添加对苯二甲酸、九水硝酸铬和氯化铵,并搅拌均匀；2)将步骤1)所得的混合液转移至反应釜中,并在恒温条件下进行晶化反应；3)反应釜完成反应并冷却至室温后,取出反应釜内的反应液,将反应液置入离心机中进行离心分离,得到晶体沉淀；4)对晶体沉淀进行干燥,得到MIL-101的晶体颗粒；本发明采用添加氯化铵的方式实现对传统MIL-101合成方法的进一步改进,具体通过氯化铵的添加能有效促进对苯二甲酸进行配位,从而降低MIL-101晶体中的对苯二甲酸杂质,并促使合成原料晶化形成更多的MIL-101晶体,有效提高MIL-101的合成率。(The invention belongs to the technical field of metal organic framework synthesis, and discloses a synthesis method of a metal organic framework MIL-101, which comprises the following steps: 1) sequentially adding terephthalic acid, chromium nitrate nonahydrate and ammonium chloride into deionized water, and uniformly stirring; 2) transferring the mixed solution obtained in the step 1) to a reaction kettle, and carrying out crystallization reaction under a constant temperature condition; 3) after the reaction kettle finishes the reaction and is cooled to room temperature, taking out the reaction liquid in the reaction kettle, and putting the reaction liquid into a centrifugal machine for centrifugal separation to obtain crystal precipitate; 4) drying the crystal precipitate to obtain crystal particles of MIL-101; the method realizes further improvement of the traditional MIL-101 synthesis method by adding ammonium chloride, and particularly can effectively promote the terephthalic acid to coordinate by adding the ammonium chloride, so that the terephthalic acid impurities in the MIL-101 crystal are reduced, the synthesis raw materials are promoted to crystallize to form more MIL-101 crystals, and the synthesis rate of the MIL-101 is effectively improved.)

1. A method for synthesizing a metal organic framework MIL-101 is characterized by comprising the following steps:

1) Sequentially adding terephthalic acid, chromium nitrate nonahydrate and ammonium chloride into deionized water, and uniformly stirring at room temperature;

2) Transferring the mixed solution obtained in the step 1) to a reaction kettle, and carrying out crystallization reaction at a constant temperature of 180 ℃;

3) after the reaction kettle finishes the reaction and is cooled to room temperature, taking out the reaction liquid in the reaction kettle, putting the reaction liquid into a centrifugal machine, and carrying out centrifugal separation to obtain crystal precipitate;

4) The crystal precipitate was dried to obtain crystal particles of MIL-101.

2. the method for synthesizing metal organic framework MIL-101 according to claim 1, wherein the method comprises the following steps: stirring for multiple times according to the adding sequence in the step 1), wherein the stirring time is not less than 15 minutes each time.

3. the method for synthesizing metal organic framework MIL-101 according to claim 1, wherein the method comprises the following steps: the molar ratio of the terephthalic acid to the chromium nitrate nonahydrate in the step 1) is 1: 1.

4. The method for synthesizing metal organic framework MIL-101 according to claim 1, wherein the method comprises the following steps: the constant temperature condition in the step 2) is formed by an electric heating type air blowing drying box.

5. The method for synthesizing metal organic framework MIL-101 according to claim 1, wherein the method comprises the following steps: and 3) centrifuging for 10 minutes at the rotating speed of 10000 r/min to complete crystal separation and collection.

6. The method for synthesizing metal organic framework MIL-101 according to claim 1, wherein the method comprises the following steps: the temperature at which the crystals are dried in step 4) is 50 ℃.

Technical Field

The invention belongs to the technical field of metal organic framework synthesis, and particularly relates to a synthesis method of a metal organic framework MIL-101.

Background

the metal organic framework is a novel crystalline porous material which is formed by metal ions or metal clusters and organic ligands through coordination bonds and has a periodic infinite topological structure, and has the advantages of high porosity, large specific surface area, various structures and the like;

MIL-101 is a novel porous material synthesized and reported by Ferey project group in France, the material has larger specific surface area, can stably exist in the air for a long time, and the framework structure of the material can not be changed at high temperature; meanwhile, the MIL-101 also has a Lewis acid site and an unsaturated metal site, so that the MIL-101 has wide application prospects in the aspects of gas adsorption and catalysis.

however, since the discovery of MIL-101, synthesis of MIL-101 with a larger specific surface area has not been achieved due to limitations of synthesis technology, due to the following reasons: a large amount of terephthalic acid is adhered in the pore canal of the synthesized MIL-101 crystal, so that the specific surface area and the pore volume of the MIL-101 are reduced, and high terephthalic acid impurities exist in the formed MIL-101 crystal, and the impurities can be removed only by subsequent cleaning operation in the traditional synthesis method, which wastes time and labor;

in addition, if terephthalic acid is required to participate in coordination during crystallization of the MIL-101 crystal, the coordination cannot be performed after the terephthalic acid is attached, and the synthesis rate of the MIL-101 crystal is also affected.

therefore, it is necessary to provide a method for synthesizing MIL-101 with high quality, high synthesis rate and simple operation.

disclosure of Invention

the invention aims to provide a synthesis method of a metal organic framework MIL-101, which aims to effectively solve the problems of low synthesis rate, poor molding quality and complex operation of MIL-101 crystals in the prior art.

In order to achieve the purpose, the invention provides the following technical scheme: a method for synthesizing a metal organic framework MIL-101 comprises the following steps:

1) Adding terephthalic acid and chromium nitrate nonahydrate into deionized water in a molar ratio of 1: 1, and stirring uniformly at room temperature;

2) Adding ammonium chloride into the mixed solution obtained in the step 1), and continuously stirring uniformly.

3) transferring the mixed solution obtained in the step 2) to a stainless steel reaction kettle with a lining, and placing the reaction kettle in a constant-temperature electric heating type blast drying oven at 180 ℃ for crystallization reaction;

4) Closing the drying box after crystallization is finished, taking out reaction liquid in the reaction kettle after the drying box and the reaction kettle are cooled to room temperature, placing the reaction liquid in a centrifugal machine, setting the centrifugal rotation speed of centrifugation to 10000 revolutions per minute and the centrifugal time to 10 minutes, starting the centrifugal machine for centrifugal separation, and collecting crystal precipitate obtained after separation;

5) The collected crystal precipitate was dried in a drying oven at 50 ℃ to obtain crystal particles of MIL-101.

compared with the prior art, the invention has the following beneficial effects:

according to the invention, the ammonium chloride is added to realize further improvement of the traditional MIL-101 synthesis method, and particularly, the addition of the ammonium chloride can effectively promote the coordination of terephthalic acid, so that the impurities of the terephthalic acid in the MIL-101 crystal are reduced, the synthesis raw material is promoted to crystallize to form more MIL-101 crystals, and the synthesis rate and the BET specific surface area of the MIL-101 are effectively improved; moreover, the subsequent cleaning operation can be effectively omitted after the terephthalic acid impurities are reduced, so that the MIL-101 synthesis step is simpler.

in addition, the synthesis quality of the MIL-101 crystal can be effectively improved based on the addition of ammonium chloride, so that the finally formed crystal can effectively form an octahedral structure, and the framework structure of the MIL-101 is more stable.

Drawings

FIG. 1 is an XRD contrast spectrum of MIL-101 prepared in three examples of the present invention;

FIG. 2 shows FT-IR comparison spectra of MIL-101 prepared in three examples of the present invention;

FIG. 3 is a scanning electron micrograph of MIL-101 prepared in three examples of the present invention;

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

1. the synthesis of the metal-organic framework MIL-101 was carried out with reference to the following embodiment:

the first embodiment:

weighing 4mol of terephthalic acid solution with the concentration of 0.1mol/L, 4mol of chromium nitrate nonahydrate with the concentration of 0.1mol/L and 4mol of ammonium chloride with the concentration of 0.05mol/L, and sequentially dissolving in quantitative deionized water, wherein 70ml of deionized water is taken as an example in the embodiment; stirring in sequence in the mixing and dissolving process, and ensuring that the stirring time is not less than 15 minutes; after stirring, transferring the mixed solution into a stainless steel reaction kettle with a lining, then placing the reaction kettle in an electric heating type forced air drying box with the internal temperature of 180 ℃, and carrying out crystallization reaction on the mixed solution in the drying box for 24 hours; closing the drying box after crystallization is finished, taking the reaction kettle out of the drying box after the drying box and the reaction kettle are cooled to room temperature, transferring reaction liquid in the reaction kettle into a centrifugal machine, setting the centrifugal rotation speed of centrifugation to 10000 revolutions per minute and the centrifugal time to 10 minutes, starting the centrifugal machine for centrifugal separation, and collecting crystal precipitate obtained after separation; drying the collected crystal precipitate in a drying box at 50 ℃ to obtain MIL-101 crystal particles marked as MIL-101-4 Nlm-X-Y-180;

Specifically, 4Nlm represents ammonium chloride, X represents the amount of ammonium chloride added, Y represents the crystallization reaction time, and 180 represents the crystallization temperature of 180 deg.C, which is labeled MIL-101-4 Nlm-0.05-24-180;

Second embodiment:

the synthesis procedure is the same as that of the first embodiment, and the amount of ammonium chloride used in this embodiment is still 4mol, but the concentration of ammonium chloride is 0.1mol/L, so that MIL-101-4Nlm-0.1-24-180 is finally obtained;

2. The crystal particles formed in the above two examples were subjected to X-ray diffraction analysis and infrared diffraction analysis according to the measurement method commonly used in the art for MIL-101, to form an XRD contrast pattern shown in fig. 1 and an FT-IR contrast pattern shown in fig. 2, respectively:

specifically, as shown in fig. 1, a relatively obvious diffraction peak appears in the range of 2 θ ═ 8 ° to 10 °, and a characteristic peak of MIL-101 is shown according to the method provided in the technical literature, thereby indicating that the synthesis of MIL-101 crystals exists at this time, and proving that the addition of ammonium chloride does not damage the crystal structure of MIL-101;

in addition, a characteristic diffraction peak of terephthalic acid occurred in the range of 18 ° -29 ° 2 θ, and in combination with the graphical comparison of the two examples, the peak value of terephthalic acid at an ammonium chloride concentration of 0.05mol/L was greater than that of terephthalic acid at a concentration of 0.1mol/L, thereby indicating that more terephthalic acid impurities were present in the MIL-101 crystals obtained by the reaction at an ammonium chloride concentration of 0.05 mol/L;

In conclusion, the impurity content of terephthalic acid in the crystal structure of MIL-101 can be effectively reduced by adding ammonium chloride, and the crystal structure of MIL-101 itself is not affected;

Further, as shown in FIG. 2, a vibration peak of terephthalic acid appears in a range of a wave number of about 3000cm-1, i.e., it is illustrated that terephthalic acid having a completed coordination exists in the range; by combining the graphical comparison of the ammonium chloride concentrations of 0.05mol/L and 0.1mol/L, the peak amplitude of the generated terephthalic acid vibration peak is smaller as the ammonium chloride concentration is increased, thereby indicating that more terephthalic acid participates in coordination when the ammonium chloride concentration is 0.1mol/L, and more MIL-101 crystals are formed through crystallization;

In summary, it is found that ammonium chloride has an accelerating effect on the coordination of terephthalic acid in the synthesis process of MIL-101 crystals, and that the larger the concentration of ammonium chloride, the larger the accelerating effect.

3. scanning the MIL-101 crystal particles formed in the two examples according to an image-capturing method commonly used in the art, and scanning under a 4 μm image to form an electron microscope image shown in fig. 3:

specifically, wherein a is a crystal diagram of MIL-101 formed in example 1; panel b is a crystal diagram of MIL-101 formed in example 2;

according to the crystal structures shown in the figures, the MIL-101 crystals formed by the two examples are both of typical octahedral structures, wherein the sizes of the crystal particles in the a diagram are relatively small, the sizes of the crystal particles in the b diagram are larger, and no particle aggregation phenomenon exists;

from the above, it is understood that the addition of ammonium chloride has a certain effect of promoting the molding quality of the MIL-101 crystal, and that the higher the ammonium chloride concentration, the better the molding quality.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.