In situ fabrication of metal-organic framework films and mixed-matrix membranes
Provided herein are in situ methods for fabricating a mixed-matrix membrane or a mixed-matrix hollow fiber membrane for increasing formation of zeolitic imidazolate framework nanoparticles inside the mixed-matrix membrane. Generally, in the method a polyimide polymer coated onto at least one support is hydrolzed with a base and the poly(amic acid)-salt film formed thereby undergoes ion exchange with a metal ion, treatment of the formed poly(amic acid)-metal salt film with an organic linker to produce metal-organic framework nanoparticles in situ, and imidization of the treated poly(amic acid)-metal salt film produces a polyimide/metal-organic framework mixed-matrix membrane or a mixed-matrix hollow fiber membrane module. Also provided is the mixed-matrix membrane and the polymer mixed-matrix hollow fiber membrane module fabricated by the methods and methods for separating a binary gas mixture via the fabricated mixed-matrix membrane.
1. An in situ method for fabricating a mixed-matrix membrane, comprising:
coating a polyimide polymer onto at least one support;
hydrolyzing the polyimide polymer with a base to produce a poly(amic acid)-salt film;
exchanging salt ions in the poly(amic acid)-salt film with metal ions in an aqueous metal salt solution to produce a poly(amic acid)-metal salt film;
treating the poly(amic acid)-metal salt film with an organic linker to produce metal-organic framework nanoparticles in situ; and
imidizing the treated poly(amic acid)-metal salt film to produce a polyimide/metal-organic framework mixed-matrix membrane.
2. The method of claim 1 , wherein the polyimide polymer is (4,4-(Hexafluoroisopropylidene)diphthalic anhydride-2,4,6-trimethyl-1,3-phenylene diamine (6FDA-DAM), pyromellitic dianhydrides oxidianiline (PMDA-ODA), 3,3-4,4-benzophenone tetracarboxylic dianhydride diaminophenylindane (BTDA-DAPI).
3. The method of claim 1 , wherein the support is at least one hollow fiber or at least one hollow fiber membrane, a fiber, a flat sheet, or a film.
4. The method of claim 1 , wherein the base is sodium formate, sodium hydroxide, potassium hydroxide, barium hydroxide, cesium hydroxide, strontium hydroxide, calcium hydroxide, lithium hydroxide, or rubidium hydroxide.
5. The method of claim 1 , wherein the aqueous metal salt solution is a nitrate, acetate, sulfate or chloride salt solution of zinc, cobalt, magnesium, manganese, iron, nickel, copper, or cadmium or a combination thereof.
6. The method of claim 1 , wherein the organic linker is imidazole, 2-methylimidazole, 2-ethylimidazole, 2-nitroimidazole, benzimidazole, 6-nitrobenzimidazole, or purine.
7. The method of claim 6 , wherein the organic linker is 2-methylimidazole (Hmim).
8. The method of claim 1 , wherein the hydrolyzing step opens imide rings in the polyimide polymer to produce a poly(amic acid) sodium salt.
9. The method of claim 8 , wherein the exchanging step exchanges sodium ions in the poly(amic acid) sodium salt with zinc ions to form a poly(amic acid) zinc salt film.
10. The method of claim 9 , wherein the hydrolyzed polyimide polymer has an increase in free volume and hydrophilicity such that diffusion of the zinc ions inside the polymer is increased.
11. The method of claim 9 , wherein the treating step produces zeolitic imidazolate framework nanoparticles inside the poly(amic acid) zinc salt film to form a poly(amic acid)-Zn/zeolitic imidazolate framework.
12. The method of claim 11 , wherein the zeolitic imidazolate framework is ZIF-8 or ZIF-67.
13. The method of claim 11 , wherein the imidizing step produces a polyimide/zeolitic imidazolate framework mixed-matrix membrane.
14. The method of claim 13 , wherein the polyimidazole/zeolitic imidazolate framework mixed-matrix membrane is polyimide/ZIF-8.
15. The method of claim 1 , wherein the support is a plurality of hollow fiber membranes, the coating step comprising:
coating a layer of the polyimide polymer onto each of the plurality of hollow fiber membranes to produce a plurality of polyimide polymer hollow fiber membranes; and
assembling the plurality of polyimide polymer hollow fiber membranes into a module.
16. A mixed-matrix membrane hollow fiber module fabricated by the method of claim 15 .
17. The mixed-matrix membrane hollow fiber module of claim 16 that is a 6FDA-DAM/ZIF-8 mixed-matrix hollow fiber membrane module.
18. A method for separating a propylene/propane gas mixture, comprising:
flowing the propylene/propane gas mixture through the mixed-matrix membrane hollow fiber module of claim 16 .
19. A mixed-matrix membrane fabricated by the method of claim 1 .
20. The mixed-matrix membrane of claim 19 , wherein the mixed-matrix membrane is doped with at least one of zinc, cobalt, magnesium, manganese, iron, nickel, copper, or cadmium.
21. The mixed-matrix membrane of claim 20 that is a polyimide/ZIF-8 mixed-matrix membrane doped with zinc or a polyimide/ZIF-67 mixed-matrix membrane doped with cobalt.
22. The mixed-matrix membrane of claim 19 , said mixed-matrix membrane fabricated from each of a plurality of polymer hollow fiber membranes comprising a module.
23. The mixed-matrix membrane of claim 22 that is a 6FDA-DAM/ZIF-8 mixed-matrix hollow fiber membrane.
24. A method for separating a binary gas mixture, comprising:
flowing the binary gas mixture through the mixed-matrix membrane of claim 19 .
25. The method of claim 24 , wherein the binary gas mixture is a propylene/propane gas mixture.