Chromium-based metal organic framework material and application thereof

Abstract

The application discloses a chromium-based metal organic framework material and application thereof, and the framework material is a non-symmetrical coordination structure formed by chromium metal ions in a six-coordination mode and 5-sulfonic acid group phthalic acid monosodium, and is a crystalline material containing micro-pores and mesopores at the same time. The micro-morphology of the framework material is a bundle structure composed of fine bundles. The framework material has excellent water and thermal stability and catalytic performance of esterification of organic acid and alcohol.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal organic framework materials, in particular to a chromium-based metal organic framework material and application thereof. BACKGROUND

[0002] Metal organic framework material is a kind of porous crystalline material formed by metal ions and organic ligands through coordination bonding. Due to the diversity of coordination assembly mode and the diversity of metal ions and organic ligands, this kind of material has high structural adjustability and rich structural variability, and is widely studied and applied in catalysis, adsorption, separation, sensing and other fields, and the related research reports are increasing year by year.

[0003] In particular, the metal ions in the structure of metal organic framework material provide potential possibility for Lewis acid sites, and by precisely controlling the synthesis conditions to regulate the coordination mode of the metal ions and the ligands, the metal ions exist in a non-full coordination state, and the unsaturated coordination sites generated can serve as Lewis acid sites. The organic ligands in the structure provide conditions for Bronsted acid sites, and by selecting ligands with specific functional groups such as sulfonic acid groups, Bronsted acid sites can be introduced into the structure. By fine-tuning the synthesis conditions, the metal ions and the ligands with sulfonic acid groups are coordinated and assembled, so that the Lewis acid sites and the Bronsted acid sites are organically distributed in the highly ordered porous structure, which can efficiently catalyze organic reactions.

[0004] The stability of metal organic framework material is not as good as that of carbon material and zeolite molecular sieve material. Most metal organic framework materials have poor hydrothermal stability, such as metal organic framework materials synthesized by zinc metal ions and terephthalic acid ligands, copper metal ions and terephthalic acid ligands, copper metal ions and trimesic acid ligands, nickel metal ions and terephthalic acid ligands, etc. The poor hydrothermal stability limits the application of these materials. At the same time, the existing metal organic framework materials still have the problem of poor catalytic effect. SUMMARY

[0005] In order to solve the above technical problems, the present application provides a chromium-based metal organic framework material and application thereof, which has water and thermal stability and excellent performance in catalyzing esterification reaction of organic acid and alcohol.

[0006] Specifically, the present application is realized by the following scheme:

[0007] A chromium-based metal organic framework material, wherein the framework material is a non-symmetrical coordination structure formed by chromium metal ions in a hexa-coordinated manner and 5-sulfonic acid group m-terephthalic acid monosodium.

[0008] Further, the framework material is a crystalline material with multi-scale pores including micropores and mesopores.

[0009] Further, the micro-morphology of the framework material is a bundle structure composed of thin bundles.

[0010] Further, the framework material is prepared by the following steps:

[0011] (1) dissolving a chromium salt, an organic ligand 5-sulfonic acid isophthalic acid monosodium and an additive hydrofluoric acid in a solvent deionized water to obtain a precursor solution;

[0012] (2) transferring the precursor solution obtained in step (1) to a sealed high-pressure reactor for reaction;

[0013] (3) after the reactor in step (2) is cooled to room temperature after the reaction is completed, the crude product is washed and dried to obtain a primary product;

[0014] (4) treating the primary product in step (3) with an acid solution, washing away the residual acid, and drying to obtain the chromium-based metal organic framework material.

[0015] Further, the molar ratio of the chromium salt to 5-sulfonic acid isophthalic acid monosodium, hydrofluoric acid and deionized water in step (1) is 1:(1-5):(0.5-2.5):(200-1200).

[0016] Further, the temperature of the reaction in step (2) is 150-220℃, and the reaction time is 16-72h.

[0017] Further, the way of washing the crude product in step (3) is to wash with deionized water and then with methanol.

[0018] Further, the acid solution treatment in step (4) is to treat the primary product with an HCl solution with a concentration of 0.02mol / L-0.2mol / L for 30-240 minutes, and the residual acid is washed away by first washing with a mixed solution of deionized water and methanol with a volume ratio of (1-5):1, and then washing with methanol.

[0019] Further, the application also provides a chromium-based metal organic framework material as a catalyst in catalysis.

[0020] Further, the application is used for catalyzing the esterification reaction of organic acid and alcohol.

[0021] Beneficial effects:

[0022] 1、The framework material of the present application has excellent stability because the chromium metal ions form an asymmetric coordination structure with the monosodium 5-sulfonic isophthalate in a six-coordinated manner. The framework material of the present application has excellent hydrothermal stability because it does not change significantly after being soaked in water for three days and can withstand a temperature of 250 DEG C.

[0023] 2、The framework material of the present application has excellent stability because the chromium metal ions form an asymmetric coordination structure with the monosodium 5-sulfonic isophthalate in a six-coordinated manner. The framework material of the present application has excellent hydrothermal stability because it does not change significantly after being soaked in water for three days and can withstand a temperature of 250 DEG C.

[0024] 3、The framework material of the present application has excellent stability because the chromium metal ions form an asymmetric coordination structure with the monosodium 5-sulfonic isophthalate in a six-coordinated manner. The framework material of the present application has excellent hydrothermal stability because it does not change significantly after being soaked in water for three days and can withstand a temperature of 250 DEG C.

[0025] 4、The framework material of the present application has excellent stability because the chromium metal ions form an asymmetric coordination structure with the monosodium 5-sulfonic isophthalate in a six-coordinated manner. The framework material of the present application has excellent hydrothermal stability because it does not change significantly after being soaked in water for three days and can withstand a temperature of 250 DEG C. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The product powder X-ray diffraction patterns of Example 1 and Comparative Example 1 and Comparative Example 2.

[0027] Figure 2The micro-morphology and macro-morphology observation figures of the products of Example 1 and Comparative Example 1, Comparative Example 2.

[0028] Figure 3 The thermogravimetric test figures and their first derivative figures of the products of Example 1 and Comparative Example 1, Comparative Example 2.

[0029] Figure 4 The nitrogen adsorption-desorption test figures of the products of Example 1 and Comparative Example 1, Comparative Example 2 at 77K.

[0030] Figure 5 The pore size distribution figures of the products of Example 1 and Comparative Example 1, Comparative Example 2.

[0031] Figure 6 The in-situ adsorption saturated infrared spectra of the products of Example 1 and Comparative Example 1, Comparative Example 2 in deuterated acetonitrile at 25℃ and the in-situ desorption infrared spectra at different temperatures.

[0032] Figure 7 The deconvolution results figures of the in-situ adsorption saturated spectra of the products of Example 1 and Comparative Example 1, Comparative Example 2 in deuterated acetonitrile at 25℃.

[0033] Figure 8 The performance figures of the products of Example 1 and Comparative Example 1, Comparative Example 2 in catalyzing the esterification reaction of levulinic acid and ethanol.

[0034] Figure 9 The powder X-ray diffraction figures of the product of Example 1 before and after being soaked in water for 3 days. DETAILED DESCRIPTION

[0035] The technical solutions provided by the present application will be described more clearly in combination with the embodiments and the accompanying drawings, but the scope of protection required by the present application is not limited to the following embodiments.

[0036] Example 1

[0037] In 60 mL of deionized water, 20 mmol of 5-sulfonic isophthalic acid monosodium and 0.348 mL of 40 wt% hydrofluoric acid aqueous solution were sequentially added under stirring, and after stirring for 30 minutes, 10 mmol of chromium nitrate nonahydrate was added, and stirring was continued for 30 minutes. The above mixed solution was transferred into the inner liner of a high-pressure reaction kettle after ultrasonic treatment for 30 minutes. After the high-pressure reaction kettle was sealed, it was placed in an oven and reacted at 190°C for 24 hours. After the reaction was completed and the high-pressure reaction kettle was cooled to room temperature, the crude product was washed with deionized water for 3 times, and then washed with methanol for 3 times, and dried in a 90°C air oven overnight to obtain the primary product. 0.5 g of the primary product was weighed and added to 50 mL of 0.04 mol / L HCl (two-thirds volume of deionized water and one-third volume of methanol mixture as solvent) and stirred at room temperature for 90 minutes. The residual acid was washed with a mixture of two-thirds volume of deionized water and one-third volume of methanol for 3 times, and then washed with methanol for 3 times, and dried in a 90°C air oven overnight to obtain the chromium-based metal organic framework material.

[0038] Comparative Example 1

[0039] The difference between Example 1 and Comparative Example 1 is only that the acid solution treatment is not performed, and only the primary product, i.e. the nascent chromium-based metal organic framework material, is obtained.

[0040] Comparative Example 2

[0041] The difference between Example 1 and Comparative Example 2 is only that 2-sulfonic terephthalic acid monosodium is used instead of 5-sulfonic isophthalic acid monosodium in Example 1, and the crude product is washed with N,N-dimethylformamide for 3 times instead of deionized water in Example 1.

[0042] Performance test:

[0043] 1. The products of Example 1 and Comparative Examples 1 and 2 were subjected to powder X-ray diffraction experiments, and the results are shown in Figure 1 . The results show that the diffraction peak type of the product of Example 1 is similar to that of the product of Comparative Example 1, and the main difference is that the diffraction peak intensity near 2.4° is significantly enhanced. In addition, the diffraction peak type of the product of Example 1 is completely different from that of the product of Comparative Example 2, which are two completely different crystal structure MOF materials.

[0044] 2. The products of Example 1 and Comparative Examples 1 and 2 were observed for micro-morphology and macro-morphology, and the results are shown in Figure 2 . The results show that the product of Example 1 of the present application is a bundle structure composed of fine bundles, and the micro-morphology of the product of Comparative Example 1 is similar to that of the product of Example 1, with no obvious difference. The product of Comparative Example 2 is a regular octahedral structure. The above three products are all dark green powders in macroscopic appearance.

[0045] 3、The elemental analysis results of the products of Example 1 and Comparative Examples 1 and 2 are shown in Table 1. The results show that the molar ratio of S / Cr of the product of Example 1 is the same as that of Comparative Example 1, both being 1.01, while the molar ratio of S / Cr of the product of Comparative Example 2 is 0.78. Under the same reference conditions, a high molar ratio of S / Cr represents a large number of sulfonic acid groups.

[0046] Table 1 Elemental analysis results

[0047] Sample Cr (wt%) S (wt%) C (wt%) H (wt%) F (wt%) O (wt%) Chemical Formula Example 1 12.56 7.79 28.86 2.83 0.36 47.60 Cr1S 1.01 C 9.95 H 11.63 F 0.08 O 12.32 ]]> Comparative Example 1 12.13 7.55 32.07 3.59 0.39 44.26 Cr1S 1.01 C 11.45 H 15.25 F 0.09 O 11.86 ]]> Comparative Example 2 12.66 6.08 23.60 3.34 0.62 53.70 Cr1S 0.78 C 8.07 H 13.60 F 0.13 O 13.78 ]]>

[0048] 4、The products of Example 1 and Comparative Examples 1 and 2 were subjected to thermogravimetric testing, and the results are shown in Figure 3 . The results show that the product of Example 1 can withstand a temperature of 250℃, the product of Comparative Example 1 has the same temperature resistance as that of Example 1, and the product of Comparative Example 2 can withstand a temperature of 260℃, which shows that the product of Example 1 of the present application has thermal stability comparable to that of the products of the comparative examples.

[0049] 5、The products of Example 1 and Comparative Examples 1 and 2 were subjected to nitrogen adsorption-desorption testing at 77K, and the results are shown in Figure 4 . The pore size distribution was analyzed using non-local density functional theory, and the results are shown in Figure 5 . The specific surface area, micropore volume and mesopore volume were analyzed by BET equation and T-PLOT method, and the results are shown in Table 2. From the above results, it can be seen that the product of Example 1 of the present application has a pore structure with both micropores and mesopores, and its BET specific surface area and pore volume are slightly higher than those of Comparative Example 1, but are about half of those of Comparative Example 2.

[0050] Table 2 BET specific surface area and pore volume data

[0051] Sample BET specific surface area (m 2 g -1 )]]> Micropore volume (cm3 / g 3 g -1 )]]> Mesopore volume (cm3 / g 3 g -1 )]]> Total pore volume (cm3 / g 3 g -1 )]]> Example 1 591.63 0.271 0.136 0.407 Comparative Example 1 533.48 0.220 0.097 0.319 Comparative Example 2 1345.00 0.645 0.215 0.860

[0052] 6、With deuterated acetonitrile as a probe molecule, the in-situ adsorption saturated infrared spectra of deuterated acetonitrile of Example 1 and Comparative Examples 1 and 2 at 25℃ and the in-situ desorption infrared spectra at different temperatures were tested, and the results are shown in Figure 6 . Figure 7 The deconvolution results of the in-situ adsorption saturated spectra of deuterated acetonitrile of Example 1 and Comparative Examples 1 and 2 at 25℃ are shown in Figure 2, and the peak position and peak area of the deconvolution of the in-situ adsorption saturated spectra of deuterated acetonitrile at 25℃ are shown in Table 3:

[0053] Table 3 Peak position and peak area of the deconvolution of the in-situ adsorption saturated spectra of deuterated acetonitrile at 25℃

[0054]

[0055] The results show that the number of medium-strength Lewis acid sites and the number of super-strong Lewis acid sites contained in the product of Example 1 of the present invention are comparable to those of Comparative Example 1; the number of weak Bronsted acid sites is 0.29 times less than that of Comparative Example 1; while the number of medium-strength Bronsted acid sites is 0.29 times greater than that of Comparative Example 1, the number of strong Bronsted acid sites is 0.57 times greater than that of Comparative Example 1, the number of weak Lewis acid sites is 0.08 times greater than that of Comparative Example 1, and the number of strong Lewis acid sites is 0.24 times greater than that of Comparative Example 1. In addition, the number of weak Bronsted acid sites, the number of weak Lewis acid sites, the number of medium-strength Lewis acid sites, and the number of strong Lewis acid sites contained in the product of Example 1 are comparable to those of Comparative Example 2; while the number of medium-strength Bronsted acid sites is 1.35 times greater than that of Comparative Example 2, the number of strong Bronsted acid sites is 0.98 times greater than that of Comparative Example 2, and the number of super-strong Lewis acid sites is 0.41 times greater than that of Comparative Example 2.

[0056] 7. The products of Example 1 and Comparative Examples 1 and 2 were used as catalysts to catalyze the reaction of levulinic acid and ethanol to produce ethyl levulinate. Specifically, in a 10 mL sealed reaction bottle with a reflux condenser, the total volume of the reactants was fixed at 1 mL, the acid-alcohol molar ratio was 1:5, the amount of catalyst was 3 wt% of the total mass of the reactants, and the reaction temperature was 130°C. The reaction products were analyzed by gas chromatography using ethyl laurate as an internal standard using the internal standard method to test the catalytic performance. The results are shown in Table 1. Figure 8 The results show that the conversion rates, from highest to lowest, are as follows: Example 1, Comparative Example 1, and Comparative Example 2. The conversion rate of the product of Example 1 is approximately 12% higher than that of Comparative Example 1, and approximately 21% higher than that of Comparative Example 2. In particular, the selectivity of the esterification reaction product, ethyl levulinate, is 100% in all cases, but is not shown in the figure for clarity.

[0057] 8. The product of Example 1 was soaked in water for three days, and the powder X-ray diffraction patterns before and after soaking were tested. The results are shown in Table 1. Figure 9 The results show that the product of Example 1 has excellent water stability.

[0058] In summary, the present invention prepares a chromium-based metal-organic framework material with a completely new structure, which has excellent hydrothermal stability and acid catalytic performance, and its cost advantage is very significant.

[0059] The above embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be noted that for ordinary skilled in the art, without departing from the concept of the present application, several modifications and improvements can be made, which are within the scope of protection of the present application.

Claims

1. A chromium-based metal-organic framework material, characterized in that: The framework material is an asymmetric coordination structure formed by chromium metal ions in a hexacoordinated manner with 5-sulfoisophthalic acid monosodium; The frame material is prepared by the following steps: (1) dissolving chromium salt, organic ligand 5-sulfoisophthalic acid monosodium salt and additive hydrofluoric acid in deionized water as a solvent to obtain a precursor solution; (2) transferring the precursor solution obtained in step (1) into a sealed high-pressure reactor for reaction; (3) After the reaction kettle in step (2) is cooled to room temperature, the crude product is washed and dried to obtain a primary product; (4) treating the primary product in step (3) with an acid solution, washing away the residual acid, and drying to obtain the chromium-based metal-organic framework material; The molar ratio of the chromium salt to monosodium 5-sulfoisophthalate, hydrofluoric acid and deionized water in step (1) is 1: (1-5): (0.5-2.5): (200-1200); The reaction temperature in step (2) is 150-220°C, and the reaction time is 16-72 h; In the step (4), the acid solution treatment is performed by using a mixed solution of deionized water and methanol in a volume ratio of (1-5):1 as a solvent and an HCl solution with a concentration of 0.02 mol / L-0.2 mol / L.

2. The chromium-based metal-organic framework material according to claim 1, characterized in that The framework material is a crystalline material with multi-scale pores containing both micropores and mesopores.

3. The chromium-based metal-organic framework material according to claim 1, characterized in that The microstructure of the frame material is a bundle-like structure composed of thin bundles.

4. The chromium-based metal-organic framework material according to claim 1, characterized in that The crude product is washed in step (3) by washing with deionized water and then with methanol.

5. The chromium-based metal-organic framework material according to claim 1, characterized in that In the step (4), the acid treatment time is 30-240 minutes; the method for washing away the residual acid is to first wash with a mixed solution of deionized water and methanol in a volume ratio of (1-5):1, and then wash with methanol.

6. Use of the chromium-based metal organic framework material as a catalyst in catalysis according to any one of claims 1 to 5, characterized in that: Used to catalyze the esterification reaction of organic acids and alcohols.

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