A preparation method of a MIL-125 (Ti)-Cr material and improvement of water stability thereof

Abstract

The application belongs to the technical field of material preparation, and discloses a MIL-125(Ti)-Cr material and a preparation method for improving water stability of the MIL-125(Ti)-Cr material, which comprises the following steps: dissolving terephthalic acid and isopropyl titanate in a mixed solvent of N,N-dimethylformamide and methanol to obtain a first reaction solution; performing a hydrothermal reaction on the first reaction solution at a set temperature to obtain MIL-125(Ti); and performing a modification reaction on the MIL-125(Ti) by using Cr 3+ source to obtain the MIL-125(Ti)-Cr. The preparation method has the advantages of simple process, easy operation, wide raw material sources, low cost, and the like, and the prepared MIL-125(Ti)-Cr material has stable structure and wide application prospect.

Description

TECHNICAL FIELD

[0001] The application relates to a MIL-125(Ti)-Cr material and a preparation method for improving water stability of the MIL-125(Ti)-Cr material, and belongs to the technical field of material preparation. BACKGROUND

[0002] Metal-organic framework materials (MOFs) are a kind of porous crystalline structure materials formed through coordination between metal nodes and organic ligands. The types of metal ions and organic ligands are various, the connection modes are various, and different reaction conditions will lead to different structures of the formed MOFs materials. Therefore, the structures of MOFs are various and complex. Compared with traditional molecular sieves and porous materials, MOFs have the characteristics of large specific surface area, adjustable structure-function, permanent pores and the like, so that the MOFs exhibit great application potential in catalysis, energy storage and separation and the like.

[0003] Since the metal-organic coordination bonds of the MOFs materials are mostly unstable, the water stability of the MOFs materials is poor, and the MOFs materials are very sensitive to water, especially difficult to maintain the skeleton stable for a long time in an aqueous solution. After the MOFs adsorb water molecules, the metal-organic coordination bonds are destroyed until the structure skeleton collapses. However, gaseous water and liquid water inevitably exist in the production and life processes such as material preparation, storage and transportation, which puts forward higher requirements for the water stability of the MOFs materials, and greatly limits the practical application of the MOFs materials. At present, the common method for improving the stability of the MOFs materials is to use the hydrophobic groups modified in the ligands and cover the hydrophobic layer on the crystal surface to improve the water stability of the framework materials, and there is no related research on improving the long-time water stability of the MIL-125(Ti) material framework structure. SUMMARY

[0004] The application aims at overcoming the defects in the prior art, and provides a MIL-125(Ti)-Cr material with high water stability and a preparation method thereof, which are used for preparing the MIL-125(Ti)-Cr material capable of maintaining the structure stable for a long time in an aqueous solution.

[0005] To achieve the above object, the technical scheme adopted by the application is as follows:

[0006] The application provides a preparation method for improving the water stability of a MIL-125(Ti)-Cr material, which comprises the following steps:

[0007] Dissolve terephthalic acid and isopropyl titanate in a solvent to obtain a first reaction solution; wherein the solvent is a mixture of N,N-dimethylformamide and methanol;

[0008] The first reaction solution is subjected to hydrothermal reaction at a set temperature to obtain MIL-125(Ti);

[0009] with Cr 3+ The MIL-125(Ti) is subjected to a modification reaction with a Cr source to obtain MIL-125(Ti)-Cr.

[0010] Further, the mass-volume ratio of terephthalic acid to isopropyl titanate is 1.1 g / mL-1.9 g / mL.

[0011] The Cr 3+ source is Cr(NO3)3 or a hydrate thereof. 3+ The amount-of-substance ratio of the Cr

[0012] Further, the volume ratio of N,N-dimethylformamide to methanol is (8-10):1, preferably 9:1.

[0013] Further, the set temperature is 160℃-190℃, preferably 180℃, and the hydrothermal reaction time is at least 72 h.

[0014] Further, the Cr 3+ source is a soluble trivalent chromium salt or a hydrate thereof, preferably Cr(NO3)3 or a hydrate thereof.

[0015] Further, the method further comprises, after the hydrothermal reaction is completed, subjecting the reaction product to suction filtration, first washing, to obtain MIL-125(Ti).

[0016] And / or, after the modification reaction is completed, subjecting the reaction product to suction filtration, second washing, to obtain MIL-125(Ti)-Cr.

[0017] Further, the first washing is performed at least three times using N,N-dimethylformamide and anhydrous ethanol, respectively.

[0018] Further, the second washing is performed at least three times using deionized water and anhydrous ethanol, respectively.

[0019] The application also provides a MOF MIL-125(Ti) material prepared according to any of the above methods.

[0020] Further, the MOF MIL-125(Ti) material can remain stable in an aqueous solution for more than 72 h.

[0021] Compared with the prior art, the application has the following beneficial effects:

[0022] The application prepares a MIL-125(Ti) material through a simple hydrothermal reaction, and the MIL-125(Ti) material is modified with a Cr 3+The metal ion modification obtains the MIL-125 (Ti)-Cr material, the framework structure of which can be stable in a severe environment such as an aqueous solution for more than three days, and the long-time water stability of the framework structure of the MIL-125 (Ti)-Cr is improved;

[0023] The method for preparing the MOF MIL-125 (Ti) material is simple, raw materials are widely available and easy to obtain, the cost is low, the process is simple and easy to operate, the obtained MIL-125 (Ti)-Cr material has a stable structure, and has a wide application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is an SEM image of a MIL-125 (Ti) sample synthesized in an embodiment of the present application;

[0025] Figure 2 is an SEM image of a MIL-125 (Ti)-H2O sample synthesized in a comparative example of the present application;

[0026] Figure 3 is an SEM image of a MIL-125 (Ti)-Cr sample synthesized in an embodiment of the present application;

[0027] Figure 4 is an XRD image of the products MIL-125 (Ti) and MIL-125 (Ti)-Cr in an embodiment of the present application, and MIL-125 (Ti)-H2O in a comparative example;

[0028] Figure 5 is an FT-IR image of the products MIL-125 (Ti) and MIL-125 (Ti)-Cr in an embodiment of the present application, and MIL-125 (Ti)-H2O in a comparative example. DETAILED DESCRIPTION

[0029] The present application will be further described below in conjunction with the drawings. The following examples are only used to more clearly illustrate the technical solutions of the present application, and cannot be used to limit the protection scope of the present application.

[0030] The present application provides a preparation method of a MIL-125 (Ti)-Cr material with high water stability, specifically comprising the following steps:

[0031] The terephthalic acid is dissolved in a mixed solution of N,N-dimethylformamide and methanol, and then isopropyl titanate is added, and after stirring and ultrasonic treatment in a temperature range of 20-30 DEG C, it is transferred into a reaction kettle, wherein the mass / volume ratio of terephthalic acid to isopropyl titanate is in the range of 1.1 g / mL-1.9 g / mL;

[0032] The reactor is placed in the oven for heating, and then cooled to 20-30 DEG C, the reaction product is filtered, washed for the first time, and dried at 20-30 DEG C to obtain a white powder, which is MIL-125 (Ti);

[0033] The Cr 3+ source is dissolved in deionized water, MIL-125 (Ti) is added, and the reaction is carried out at 20-30 DEG C for at least 72 h, the reaction product is filtered, washed for the second time, and dried at room temperature to obtain the product MIL-125 (Ti)-Cr, wherein the Cr 3+ The molar ratio of the Cr

[0034] The Cr 3+ source in the embodiment of the application is a soluble trivalent chromium salt or a hydrate thereof, preferably Cr(NO3)3 or a hydrate thereof, and in some embodiments, Cr(NO3)3.9H2O is selected, and the mass ratio of Cr(NO3)3.9H2O to MIL-125 (Ti) is (0.1-2):1.

[0035] Specifically, the volume ratio of N,N-dimethylformamide and methanol in the preparation process is (8-10):1, preferably 9:1; the temperature for placing the reactor in the oven for heating is 160-190 DEG C, preferably 180 DEG C; and the temperature range of room temperature is 20-30 DEG C.

[0036] The first washing is carried out by using N,N-dimethylformamide and anhydrous ethanol for at least three times, respectively; and the second washing is carried out by using deionized water and anhydrous ethanol for at least three times, respectively.

[0037] The application further provides a MOF MIL-125 (Ti) material prepared according to the preparation method of the MIL-125 (Ti)-Cr material with high water stability, wherein the prepared MOF MIL-125 (Ti) material can remain stable in an aqueous solution for more than 72 h.

[0038] The raw reagents used in the application include isopropyl titanate, terephthalic acid, N,N-dimethylformamide, methanol, anhydrous ethanol, chromium nitrate 9H2O, and deionized water. The medicines used are all of analytical reagent (A.R.) grade.

[0039] The application preferably adds 16-20 mmol of terephthalic acid, 5-10 mmol of isopropyl titanate, and 0.025-0.5 mmol of Cr(NO3)3.9H2O.

[0040] Example 1:

[0041] The MOF MIL-125(Ti) material is prepared according to a preparation method of the MIL-125(Ti)-Cr material with high water stability, and the preparation method specifically comprises the following steps:

[0042] Preparation of MIL-125(Ti): 2.66 g of terephthalic acid is dissolved in a mixed solution of 54 mL of N,N-dimethylformamide and 6 mL of methanol, and then 1.42 mL of isopropyl titanate is added. After the mixed solution is magnetically stirred and ultrasonically treated for 5 min at room temperature, the mixed solution is transferred into a 100 mL reaction kettle;

[0043] The reaction kettle is placed into a 180 DEG C oven for heating reaction for 72 h, and is naturally cooled to room temperature. The reaction product is subjected to suction filtration, and then is washed with N,N-dimethylformamide and anhydrous ethanol respectively for 3 times. After being naturally dried, a white solid powder is obtained, which is the MIL-125(Ti) sample.

[0044] Preparation of MIL-125(Ti)-Cr: 100 mg of the MIL-125(Ti) sample is placed into 50 mL of deionized water, and then 0.025 mmol of Cr(NO3)3·9H2O is added. After being magnetically stirred for 72 h at room temperature, suction filtration is performed, and then washing with deionized water and anhydrous ethanol is performed for 3 times. After being dried in air at room temperature, the product MIL-125(Ti)-Cr sample is obtained.

[0045] Example 2

[0046] The MOF MIL-125(Ti) material is prepared according to a preparation method of the MIL-125(Ti)-Cr material with high water stability, and the preparation method specifically comprises the following steps:

[0047] Preparation of MIL-125(Ti): 2.66 g of terephthalic acid is dissolved in a mixed solution of 54 mL of N,N-dimethylformamide and 6 mL of methanol, and then 1.42 mL of isopropyl titanate is added. After the mixed solution is magnetically stirred and ultrasonically treated for 5 min at room temperature, the mixed solution is transferred into a 100 mL reaction kettle;

[0048] The reaction kettle is placed into a 180 DEG C oven for heating reaction for 72 h, and is naturally cooled to room temperature. The reaction product is subjected to suction filtration, and then is washed with N,N-dimethylformamide and anhydrous ethanol respectively for 3 times. After being naturally dried, a white solid powder is obtained, which is the MIL-125(Ti) sample.

[0049] Preparation of MIL-125(Ti)-Cr: Weigh 100 mg of MIL-125(Ti) sample, put it into 50 mL of deionized water, and then add 0.5 mmol Cr(NO3)3·9H2O. After stirring magnetically at room temperature for 72 h, filter the reaction product, wash it three times with deionized water and anhydrous ethanol respectively, and air dry it at room temperature to obtain the product MIL-125(Ti)-Cr sample.

[0050] Example 3:

[0051] This embodiment describes the preparation of MOF MIL-125(Ti) material based on a method for preparing a water-stable MIL-125(Ti)-Cr material. The preparation method specifically includes the following steps:

[0052] Preparation of MIL-125(Ti): 2.75 g of terephthalic acid was dissolved in a mixed solution of 54 mL of N,N-dimethylformamide and 6 mL of methanol, and then 1.48 mL of isopropyl titanate was added. The mixture was magnetically stirred and sonicated for 5 min at room temperature, and then transferred to a 100 mL reaction vessel.

[0053] The reaction vessel was placed in an oven at 180℃ and heated for 72 hours, then allowed to cool naturally to room temperature. The reaction product was filtered and washed three times each with N,N-dimethylformamide and anhydrous ethanol, and then air-dried. The resulting white solid powder was the MOF MIL-125(Ti) sample.

[0054] like Figure 1 The image shown is a scanning electron microscope (SEM) image of the MIL-125(Ti) sample synthesized in this embodiment. The image shows that the synthesized MIL-125(Ti) samples are all disc-shaped structures with a diameter of less than 1 μm and a thickness of less than 200 nm. The particles are uniformly dispersed and the interfaces are clear.

[0055] Preparation of MIL-125(Ti)-Cr: Weigh 100 mg of MIL-125(Ti) sample, put it into 50 mL of deionized water, and then add 0.25 mmol Cr(NO3)3·9H2O. After stirring magnetically at room temperature for 72 h, filter the reaction product, wash it three times with deionized water and anhydrous ethanol respectively, and air dry it at room temperature to obtain the product MIL-125(Ti)-Cr sample.

[0056] Figure 3 The image shows a SEM image of the MIL-125(Ti)-Cr sample synthesized in an embodiment of the present invention. The image shows that the synthesized MIL-125(Ti)-Cr retains the morphology and structure of the original MIL-125(Ti) material.

[0057] Figure 3 and Figure 1The results of the comparison show that the MIL-125(Ti) material can maintain structural stability in the Cr 3+ aqueous solution for a long time, and the obtained MIL-125(Ti)-Cr material maintains the framework structure of the original MIL-125(Ti) material. That is, after doping Cr 3+ ions, the water stability of the MIL-125(Ti) sample is obviously enhanced.

[0058] Comparative Example:

[0059] The MIL-125(Ti)-H2O material was prepared by the following preparation method, and the specific process is as follows:

[0060] Preparation of MIL-125(Ti): 2.75 g of terephthalic acid was dissolved in a mixed solution of 54 mL of N,N-dimethylformamide and 6 mL of methanol, and 1.48 mL of titanium isopropylate was added. After the mixed solution was stirred and ultrasonicated at room temperature for 5 min, it was transferred into a 100 mL reaction kettle;

[0061] The reaction kettle was placed in a 180℃ oven for reaction for 72 h, and then naturally cooled to room temperature. After suction filtration, washing with N,N-dimethylformamide, anhydrous ethanol for 3 times respectively, and drying at room temperature, a white solid powder was obtained, which was the MIL-125(Ti) sample.

[0062] Preparation of MIL-125(Ti)-H2O: 100 mg of the MIL-125(Ti) sample was weighed and placed in 50 mL of deionized water. After magnetic stirring at room temperature for 72 h, suction filtration, washing with deionized water, anhydrous ethanol for 3 times respectively, and natural drying at room temperature, the product MIL-125(Ti)-H2O sample was obtained.

[0063] Figure 2 The SEM photograph of the product MIL-125(Ti)-H2O sample in the comparative example of the present application shows that after stirring in water, the morphology and structure of the original MOF MIL-125(Ti) are destroyed, and the original sample is corroded and ashed. Figure 1 and Figure 2 The results of the comparison show that the MIL-125(Ti) material has poor stability in water.

[0064] Figure 4X-ray diffraction (XRD) patterns of the products MIL-125(Ti), MIL-125(Ti)-Cr in the examples and MIL-125(Ti)-H2O in the comparative example. The XRD curves show that the structure of MIL-125(Ti)-Cr remains unchanged compared with the original material MIL-125(Ti), while the structure of the synthesized MIL-125(Ti)-H2O collapses. It is illustrated that MIL-125(Ti) has poor water stability, while the addition of Cr 3+ ions significantly improves the water stability of MIL-125(Ti).

[0065] Figure 5 Fourier transform infrared (FT-IR) spectra of the products MIL-125(Ti), MIL-125(Ti)-Cr in the examples and MIL-125(Ti)-H2O in the comparative example. In the FT-IR graph, the stretching vibration peak at 450-700 cm -1 is regarded as the fingerprint peak of the Ti-O bond in the structure of the original material MIL-125(Ti), and the characteristic peaks of the examples MIL-125(Ti) and MIL-125(Ti)-Cr remain unchanged. Moreover, the stretching vibration peak of the O=C-O bond in the structure of the examples MIL-125(Ti) and MIL-125(Ti)-Cr also does not change. The results show that the Ti-O bond in the sample MIL-125(Ti)-Cr obtained after stirring in the aqueous solution containing Cr 3+ ions for 72 h still exists stably and maintains the structure of the original MOF MIL-125(Ti) unchanged.

[0066] According to Figure 5 it can be known that: the stretching vibration peak of the Ti-O bond of the product MIL-125(Ti)-H2O obtained after stirring in water for 72 h in the comparative example disappears, and the stretching vibration peak of the O=C-O bond changes, further illustrating that MIL-125(Ti) has poor water stability, and with the addition of Cr 3+ ions, the water stability of the MIL-125(Ti) material is greatly enhanced, and the structure can be kept stable in the aqueous solution for a long time.

[0067] The preparation method of the application has universality and potential design research value, and is not only suitable for MIL-125(Ti), but also suitable for other MOFs, COFs and the like materials which cannot exist stably in an aqueous solution.

[0068] The above only describes the preferred embodiments of the application, and it should be noted that for those skilled in the art, without departing from the technical principles of the application, a number of improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the application.

Claims

1. A method for preparing a water stable MIL-125(Ti)-Cr material, characterized in that, The method comprises the following steps: dissolving terephthalic acid and isopropyl titanate in a solvent to obtain a first reaction solution; wherein the solvent is a mixture of N,N-dimethylformamide and methanol; carrying out a hydrothermal reaction on the first reaction solution at a set temperature to obtain MIL-125(Ti); Using Cr 3+ The source was modified with MIL-125(Ti) to obtain MIL-125(Ti)-Cr, wherein the Cr 3+ Cr in source 3+ The molar ratio of MIL-125(Ti) ranges from 0.4 to 7.

8.

2. The production method according to claim 1, characterized by, the mass-volume ratio of the terephthalic acid to the isopropyl titanate ranges from 1.1 g / mL to 1.9 g / mL.

3. The preparation method according to claim 1, characterized in that, the volume ratio of the N,N-dimethylformamide to the methanol ranges from 8 to 10.

4. The method of claim 1, wherein, the volume ratio of the N,N-dimethylformamide to the methanol is 9:

1.

5. The production method according to claim 1, characterized by, the set temperature ranges from 160 ℃ to 190 ℃, and the hydrothermal reaction time is at least 72 h.

6. The production method according to claim 1, characterized by, the set temperature is 180 ℃.

7. The preparation method according to claim 1, characterized in that, The Cr 3+ source is a soluble trivalent chromium salt or hydrate thereof.

8. The method of claim 1, wherein, The Cr 3+ source is Cr(NO3)3or a hydrate thereof.

9. The method of claim 1, wherein, the method further comprises: after the hydrothermal reaction is completed, performing suction filtration on the reaction product, and first washing to obtain MIL-125(Ti); and / or, after the modification reaction is completed, performing suction filtration on the reaction product, and second washing to obtain MIL-125(Ti)-Cr.

10. The method of claim 9, wherein, the first washing is performed at least three times using N,N-dimethylformamide and anhydrous ethanol respectively.

11. The preparation method according to claim 9, characterized in that, the second washing is performed at least three times using deionized water and anhydrous ethanol respectively.

12. A MIL-125(Ti)-Cr material characterized in that, obtained by any one of the methods according to claims 1-11.

13. The MIL-125(Ti)-Cr material of claim 12, wherein, the MIL-125(Ti)-Cr material can remain stable in an aqueous solution for more than 72 h.

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