MOF NANOCRYSTALS

• US 20120247328A1
• Filed: 02/17/2012
• Published: 10/04/2012
• Est. Priority Date: 04/04/2011
• Status: Active Grant

• Current Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Original Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Inventors: NAIR, Sankar, BROWN, Andrew, SHOLL, David, CARSON, Cantwell
• Granted Patent: US 8,668,764 B2
• Time in Patent Office: Days
• US Class Current: 95/51
• CPC Class Codes: B01D 2256/10 Nitrogen
• CPC Class Codes: B01D 2256/16 Hydrogen
• CPC Class Codes: B01D 2256/245 Methane
• CPC Class Codes: B01D 53/228 characterised by specific membranes
• CPC Class Codes: B01D 71/028 Molecular sieves carbon B01D71/021
• CPC Class Codes: Y02C 20/40 of CO2
• CPC Class Codes: Y02P 10/146 Perfluorocarbons [PFC]; Hydrofluorocarbons [HFC]; Sulfur hexafluoride [SF6]

Abstract

MOF nanocrystals having a narrow size distribution, as well as methods of making and using same are disclosed.

Claims

1. A method for preparing uniformly small MOF crystals, comprising the step of growing a MOF crystal with ultrasound at a temperature of −

5 to 5°

C. with a morphology control additive for a period of time so as to obtain isotropic MOF crystals of average size less than one micron and a size distribution of less than +/−

20%.

2. The method of claim 1, wherein the morphology control additive is ethanol, or 2-propanol.

3. The method of claim 1, wherein size distribution is less than +/−

10%.

4. The method of claim 1, wherein size distribution is less than +/−

5%.

5. The method of claim 1, wherein the MOF is Cu(4,4′

-hexafluoroisopropylidene-bis-benzoate) and the control additive is 2-propanol.

6. A method for preparing uniformly small MOF crystals, comprising:

a) dissolving the ligand precursor in a suitable solvent and mixing;

b) adding a non-solvent (for said ligand precursor) to the mixture in step a) and mixing;

c) adding metal ions to the mixture in step b) and mixing, so as to make MOF crystals of average size less than one micron and the size distribution is less than +/−

20%.

7. The method of claim 6, wherein size distribution is less than +/−

10%.

8. The method of claim 6, wherein size distribution is less than +/−

5%.

9. The method of claim 6, wherein the non-solvent is methanol or water.

10. The method of claim 6, wherein the MOF is ZIF-90 and the non-solvent is methanol.

11. The method of claim 6, wherein the MOF is ZIF-7 and the non-solvent is methanol.

13. The method of claim 11, wherein the size distribution is less than +/−

10%.

14. The method of claim 11, wherein the size distribution is less than +/−

5%.

15. The method of claim 11, wherein the MOF is MOF508b.

16. The method of claim 11, wherein the metal ion is a metal anion.

17. The method of claim 11, wherein the metal ion is a metal acetate.

12. A method for preparing uniformly small MOF crystals, comprising

a) making a mixture of metal ion plus solvent;

b) making a separate mixture of ligand precursor plus solvent plus 2-4 fold excess of linker;

c) quickly combining samples a) and b) and mixing, so as to make MOF crystals of average size less than one micron and a size distribution of less than +/−

20%.

18. A composition of MOF crystals that are less than one micron in average size (without having been size reduced after synthesis) and have a size distribution of less than +/−

20%.

19. The composition of claim 19, having a size distribution of less than +/−

10%.

20. A membrane comprising Cu(4,4′

-hexafluoroisopropylidene-bis-benzoate) crystals of less than one micron average size (that are not size reduced after synthesis) plus a porous support.

21. A membrane comprising MOF508b crystals of less than one micron average size (that are not size reduced after synthesis) plus a porous support.

22. A membrane comprising ZIF-90 crystals of less than one micron average size (that are not size reduced after synthesis) plus a porous support.

23. A membrane comprising ZIF-7 crystals of less than one micron average size (that are not size reduced after synthesis) plus a porous support.

24. A method for preparing uniformly small MOF crystals, comprising the steps of:

a) growing a MOF crystal with sonication at a temperature of −

5 to 5°

C. with a morphology control additive selected from ethanol or 2-propanol for a period of time;

or

b) b1) dissolving the ligand precursor in a suitable solvent and mixing for a time, b2) separately adding a non-solvent (for said ligand precursor) and metal ions with the mixture in step b1) and growing MOF crystals for a period of time;

or

c) c1) making a mixture of metal ion plus solvent, c2) making a separate mixture of ligand precursor plus solvent plus 2-5 fold excess of linker, quickly combining mixtures c1) and c2) and growing MOF crystals for a period of time; and

d) said period of time sufficient to obtain isotropic MOF crystals of average size less than one micron and a size distribution of less than +/−

20%.

25. A membrane comprising the MOF crystals of claim 25.

26. A method of separating CO₂ from other gases, comprising subjecting a mixture of gases to the membrane of claim 26, and separating CO₂ from said mixture of gases, wherein said mixture of gases includes CO₂ plus at least one gas selected from H₂, N₂, CH₄, O₂ and combinations thereof.

27. A method of making nanosized MOF crystals, said method comprising growing MOF crystals and increasing crystal nucleation, such that isotropic MOF crystals of average size less than one micron and a size distribution of less than +/−

20% are obtained, wherein crystal nucleation is increased by keeping metal ions and ligand precursors separated until fully solvated and then quickly bringing them together or by agitation plus a crystal growth inhibitor or combinations thereof.