PROCESS FOR PREPARING A ZIRCONIUM-BASED METAL ORGANIC FRAMEWORK

Abstract

There is provided a process for preparing a zirconium-based metal organic framework (Zr-MOF), the process comprising the steps (i) preparing a reaction mixture comprising zirconium ions, sulfate ions and at least one organic linker compound in an aqueous solvent; and (ii) heating the reaction mixture from step (i).

Claims

1. A process for preparing a zirconium-based metal organic framework (Zr-MOF), comprising the steps: (i) preparing a reaction mixture comprising zirconium ions, sulfate ions and at least one organic linker compound in an aqueous solvent; and (ii) heating the reaction mixture from step (i).

2. A process as claimed in claim 1, further comprising step (iii) isolating the Zr-MOF, wherein step (iii) is carried out by filtration.

3. A process as claimed in claim 1, wherein the zirconium ions are provided in the form of at least one zirconium salt

4. A process as claimed in claim 3, wherein said zirconium salt(s) is selected from the group consisting of zirconium acetate, zirconium acrylate, zirconium carboxylate, zirconium sulfate, zirconium hydroxide, zirconium nitrate, zirconium oxynitrate, zirconium oxide, zirconium oxychloride and zirconium chloride, or mixtures thereof.

5. A process as claimed in claim 3, wherein said zirconium salt(s) is selected from the group consisting of zirconium sulfate and zirconium hydroxide, or mixtures thereof.

6. A process as claimed in claim 1, wherein the sulfate ions are provided in the form of sulfuric acid or at least one sulfate salt (e.g. zirconium sulfate)

7. A process as claimed in claim 1, wherein both the zirconium and sulfate ions are provided in the form of zirconium sulfate.

8. A process as claimed in claim 1, wherein the at least one organic linker compound comprises at least two functional groups selected from the group consisting of carboxylate (COOH), amine (NH.sub.2), anhydride and hydroxyl (OH) or a mixture thereof.

9. A process as claimed in claim 1, wherein the at least one organic linker compound comprises a linear or branched C.sub.1-20 alkyl group, a C.sub.3-12 cycloalkyl group and/or an aromatic moiety, preferably an aromatic moiety such as benzene, naphthalene, biphenyl, bipyridyl or pyridyl.

10. A process as claimed in claim 1, wherein the organic linker compound is selected from the group consisting of 1,4-benzene dicarboxylic acid (BDC), 2-amino-1,4-benzene dicarboxylic acid, 1,2,4-benzene tricarboxylic acid, 2-nitro-1,4-benzene dicarboxylic acid and 1,2,4,5-benzene tetracarboxylic acid, or mixtures thereof.

11. A process as claimed in claim 1, wherein in step (ii) of the process, the reaction mixture from step (i) is heated to a temperature in the range 50-120° C.

12. A process as claimed in claim 1, wherein step (ii) is performed for a time period of at least 20 minutes.

13. A process as claimed in claim 1, wherein the aqueous solvent consists of water.

14. A process as claimed in claim 1, wherein the Zr-MOF is produced as a crystalline powder

15. A zirconium-based metal organic framework (Zr-MOF) produced by the process as defined in claim 1.

Description

FIGURES

[0073] FIG. 1: CuK.sub.α1 powder X-ray diffraction pattern of UiO-66(Zr)—COOH produced by process of the invention clearly identifying the product as analogue of the UiO-66(Zr)-structure.

[0074] FIG. 2: TG/DSC curves for UiO-66(Zr)—COOH produced by process of the invention, showing the weight loss (solid line) and energy connected to combustion of the material (dashed line) upon heating under a flow of nitrogen. This illustrates the high thermal stability of the obtained material of ˜300° C.

[0075] FIG. 3: Adsorption isotherms measured with N.sub.2 on UiO-66-COOH at 77 K produced by the process of the invention. The shape of the isotherm clearly proves the microporous nature of the products. Filled symbols show the adsorption, empty symbols the desorption branch of the isotherm.

[0076] FIG. 4: CuK.sub.α1 powder X-ray diffraction pattern of UiO-66(Zr)—COOH produced by process of the invention after thermal activation and physisorption measurement. The data clearly shows the retention of the UiO-66(Zr)-structure after thermal treatment and sorption measurement.

[0077] FIG. 5: DRIFT spectrum of UiO-66(Zr)—COOH produced by process of the invention.

EXAMPLES

[0078] Techniques

[0079] Surface Area measurement

[0080] The specific surface area was determined by means of N.sub.2 physisorption measured on a Belsorp-mini apparatus at 77 K. Prior to the measurement the sample was activated at 373 K under vacuum for 3 h to remove occluded water molecules. The surface area was calculated by the BET-method (DIN 66131) and the Langmuir method (DIN 66135).

[0081] X-Ray Crystallography

[0082] The crystal structure was investigated by means of powder X-ray diffraction under ambient conditions in Bragg-Brentano-geometry utilizing Cu-K.sub.α1-radiation.

[0083] Stability

[0084] The thermal stability was investigated by means of thermogravimetry coupled with differential scanning calorimetry. Therefore the sample was heated up with a rate of 1 K/min under a flow of nitrogen gas, constantly monitoring weight loss and the resulting heat of combustion.

[0085] IR-Spectroscopy

[0086] In-situ Diffuse Reflectence Infrared Fourier transform spectra (DRIFT) were recorded on KBr mixed with UiO-66(Zr)—COOH produced by the process of invention. Spectra were recorded at a resolution of 2 cm.sup.−1 on a Bruker Vertex 70 spectrophotometer equipped with DTGS (Deutarated triglycine sulfate) detector.

[0087] Synthesis

[0088] Synthesis in a Microwave oven. The starting materials 1,2,4-benzenetricaboxylic acid (3.36 g) and Zr(SO.sub.4).sub.2.4H.sub.2O (1.42 g) are mixed in 20 mL of water in a microwave-vial equipped with a magnetic stirring bar. The mixture is heated at 95° C. under stirring for 60 minutes. After cooling down to room temperature by compressed air the resulting white solid is separated by filtration, washed with 20 mL of water and dried for 12 h at 90° C. to yield 1.0 g of UiO-66(Zr)—COOH.

[0089] Synthesis in a conventional oven. The starting materials 1,2,4-benzenetricaboxylic acid (6.72 g) and Zr(SO.sub.4).sub.2.4H.sub.2O (5.68 g) are mixed in 40 mL of water in a Teflon-lined steel autoclave equipped with a magnetic stirring bar. The mixture is heated at 95° C. under stirring for 60 minutes in an oven. After cooling down to room temperature the resulting white solid is separated by filtration, washed with 40 mL of water and dried for 12 h at 90° C. to yield 2.3 g of UiO-66(Zr)—COOH.

[0090] Synthesis in a capped bottle. The starting materials 1,2,4-benzenetricaboxylic acid (4.2 g) and Zr(SO.sub.4).sub.2.4H.sub.2O (3.55 g) are mixed in 25 mL of water in a Pyrex-glass bottle with screw-cap equipped with a magnetic stirring bar. The mixture is heated at 95° C. under stirring for 60 minutes in an oil bath. After cooling down to room temperature the resulting white solid is separated by filtration, washed with 25 mL of water and dried for 12 hat 90° C. to yield 1.45 g of UiO-66(Zr)—COOH.

[0091] Synthesis in a round bottom flask. In a round bottom flask (50 ml volume) with a reflux condenser, 1 g of Zr(SO.sub.4).sub.2.4H.sub.2O was dissolved in 14 mL water while stirring. Once the clear solution is obtained 2.67 g of 1,2,4-benzenetricarboxylic acid was added under stirring. This reaction mixture was placed in Oil bath which was set at 98° C. and kept stirring for 90 min. The resulting white solid separated by filtration, washed with water and acetone and dried in air to yield 1.09 g of UiO-66(Zr)—COOH. The exemplary data shown in FIGS. 1-4 was measured on a sample obtained in this way. The PXRD-patterns unambiguously prove the UiO-66-framework structure. The thermal stability is ˜300° C. under nitrogen. The apparent specific surface area according to the BET-method is 797 m.sup.2/g, applying the Langmuir method the specific surface area is 914 m.sup.2/g.