Modified zeolites that include hafnium-containing organometallic moieties and methods for making such

1. A modified zeolite comprising:

a microporous framework comprising a plurality of micropores having diameters of less than or equal to 2 nm, wherein the microporous framework comprises at least silicon atoms and oxygen atoms; and

organometallic moieties each bonded to a nitrogen atom of a secondary amine functional group comprising a nitrogen atom and a hydrogen atom, wherein the organometallic moieties comprise a hafnium atom that is bonded to the nitrogen atom of the secondary amine functional group, and wherein the nitrogen atom of the secondary amine function group bridges the hafnium atom of the organometallic moiety and a silicon atom of the microporous framework.

2. The modified zeolite of claim 1 , further comprising a plurality of mesopores having diameters of greater than 2 nm and less than or equal to 50 nm.

3. The modified zeolite of claim 1 , wherein the average pore size of the modified zeolite is greater than 2 nm.

4. The modified zeolite of claim 1 , wherein the modified zeolite comprises particles of from 25 nm to 900 nm in size.

5. The modified zeolite of claim 1 , wherein the modified zeolite is a ZSM-5 zeolite.

6. The modified zeolite of claim 1 , wherein the microporous framework further comprises aluminum atoms.

7. The modified zeolite of claim 1 , wherein the organometallic moieties comprise HfR 1 R 2 R 3 , wherein:

R 1 is chosen from any of an alkyl group, a hydride group, a hydroxyl group, an alkoxy group, an allyl group, a cyclopentadienyl group, an amino group, an amido group, an imido group, a nitrido group, a carbene group, a carbyne group, a halogen group, a benzyl group, a phenyl group, an acetyl group, or an oxide group;

R 2 is chosen from any of an alkyl group, a hydride group, a hydroxyl group, an alkoxy group, an allyl group, a cyclopentadienyl group, an amino group, an amido group, an imido group, a nitrido group, a carbene group, a carbyne group, a halide group, a benzyl group, a phenyl group, an acetyl group, or an oxide group; and

R 3 is chosen from any of an alkyl group, a hydride group, a hydroxyl group, an alkoxy group, an allyl group, a cyclopentadienyl group, an amino group, an amido group, an imido group, a nitrido group, a carbene group, a carbyne group, a halide group, a benzyl group, a phenyl group, an acetyl group, or an oxide group.

8. The modified zeolite of claim 1 , wherein the organometallic moieties comprise HfR 1 R 2 R 3 , wherein:

R 1 is an alkyl group;

R 2 is an alkyl group; and

R 3 is an alkyl group.

9. The modified zeolite of claim 1 , wherein the organometallic moieties comprise tris(neopentyl)hafnium.

10. The modified zeolite of claim 1 , wherein a concentration of organometallic moieties in the modified zeolite is at least 0.4 mmol/g.

11. A method for making a modified zeolite, the method comprising:

reacting an organometallic chemical with an amine functionalized zeolite, wherein the amine functionalized zeolite comprises a microporous framework comprising a plurality of micropores having diameters of less than or equal to 2 nm, wherein the microporous framework comprises at least silicon atoms and oxygen atoms, and wherein the amine functionalized zeolite comprises isolated terminal primary amine functionalities bonded to silicon atoms of the microporous framework;

wherein the reacting of the organometallic chemical with the amine functionalized zeolite forms the modified zeolite comprising organometallic moieties each bonded to a nitrogen atom of a secondary amine functional group comprising a nitrogen atom and a hydrogen atom, wherein the organometallic moieties comprise a hafnium atom that is bonded to the nitrogen atom of the secondary amine functional group, and wherein the nitrogen atom of the secondary amine function group bridges the hafnium atom of the organometallic moiety and a silicon atom of the modified zeolite, wherein the organometallic moieties comprises a portion of the organometallic chemical;

wherein the organometallic chemical comprises hafnium.

12. The method of claim 11 , wherein the modified zeolite comprises a plurality of mesopores having diameters of greater than 2 nm and less than or equal to 50 nm.

13. The method of claim 11 , wherein the average pore size of the modified zeolite is greater than 2 nm.

14. The method of claim 11 , further comprising contacting a dehydroxylated zeolite with ammonia to form the amine functionalized zeolite, wherein the dehydroxylated zeolite comprises isolated terminal silanol functionalities comprising hydroxyl groups bonded to silicon atoms of the microporous framework, and wherein the contacting of the dehydroxylated zeolite with the ammonia forms the amine functionalized zeolite.

15. The method of claim 14 , further comprising dehydroxylating an initial zeolite to form the dehydroxylated zeolite, wherein the initial zeolite primarily comprises vicinal silanol functionalities, and wherein dehydroxylating the initial zeolite forms the isolated terminal silanol functionalities.

16. The method of claim 15 , wherein the dehydroxylation temperature is 800° C. or less, and wherein the contacting of the dehydroxylated zeolite with ammonia is at a temperature of less than 800° C.

17. The method of claim 11 , herein the organometallic chemical comprises HfR 1 R 2 R 3 R 4 , wherein:

R 1 is chosen from any of an alkyl group, a hydride group, a hydroxyl group, an alkoxy group, an allyl group, a cyclopentadienyl group, an amino group, an amido group, an imido group, a nitrido group, a carbene group, a carbyne group, a halide group, a benzyl group, a phenyl group, an acetyl group, or an oxide group;

R 2 is chosen from any of an alkyl group, a hydride group, a hydroxyl group, an alkoxy group, an allyl group, a cyclopentadienyl group, an amino group, an amido group, an imido group, a nitrido group, a carbene group, a carbyne group, a halide group, a benzyl group, a phenyl group, an acetyl group, or an oxide group;

R 3 is chosen from any of an alkyl group, a hydride group, a hydroxyl group, an alkoxy group, an allyl group, a cyclopentadienyl group, an amino group, an amido group, an imido group, a nitrido group, a carbene group, a carbyne group, a halide group, a benzyl group, a phenyl group, an acetyl group, or an oxide group; and

R 4 is chosen from any of an alkyl group, a hydride group, a hydroxyl group, an alkoxy group, an allyl group, a cyclopentadienyl group, an amino group, an amido group, an imido group, a nitrido group, a carbene group, a carbyne group, a halide group, a benzyl group, a phenyl group, an acetyl group, or an oxide group.

18. The method of claim 11 , wherein the organometallic chemical comprises HfR 1 R 2 R 3 R 4 , wherein:

R 1 is an alkyl group;

R 2 is an alkyl group;

R 3 is an alkyl group; and

R 4 is an alkyl group.

19. The method of claim 11 , wherein one or more of:

the organometallic chemical comprises tetrakis(neopentyl)hafnium; and

the organometallic moieties of the modified zeolite comprise hafnium.

20. The method of claim 11 , wherein the microporous framework further comprises aluminum atoms.