Methods for preparing high crystallinity and surface area porous metal oxides
Exemplary embodiments provide materials and methods of forming a metal oxide composite and a porous metal oxide, which can be used for applications including catalysis, sensors, energy storage, solar cells, heavy metal removal and separations, etc. In one embodiment, a one-step solvothermal process can be used to form the metal oxide phase with high crystallinity and high surface area.
1. A method of forming a metal oxide composite comprising:
forming a water-free solution by mixing a polymer having a polymer chain comprising a hydrophilic portion and a rigid non-hydrophilic portion, an organic solvent capable of a dehydration reaction, and one or more metal precursor compounds; and
treating the water-free solution to dehydrate the organic solvent such that the one or more metal precursor compounds react to form a metal oxide phase within the hydrophilic portion of the polymer, wherein the rigid non-hydrophilic portion of the polymer supports the metal oxide phase.
2. The method of claim 1 , further comprising selecting the organic solvent such that the polymer is soluble in the organic solvent.
3. The method of claim 1 , wherein the hydrophilic portion of the polymer comprises a polymer segment comprising an ether group, an acrylic acid group, an acrylamide group, a maleic anhydride group, an amine group, or a combination thereof.
4. The method of claim 1 , wherein the rigid non-hydrophilic portion of the polymer comprises polyamide, polyacetylene, polythiophene, polyphenylene, polyfluorene, polyetherketone, polyethersulfone, polyimide, polyimidazo, pyrrolone, or a combination thereof.
5. The method of claim 1 , wherein the polymer comprises a block copolymer.
6. The method of claim 5 , wherein the block copolymer has a general formula of (A-B) n , wherein A is a rigid non-hydrophilic polymer block, B is a hydrophilic polymer block, and n ranges from about 10 to about 200.
7. The method of claim 1 , wherein the organic solvent comprises ethanol, isopropanol, butanol, glycol, glycerol, benzene, dimethylformamide, tetrahydrofuran, or a combination thereof.
8. The method of claim 1 , further comprising forming a metal oxide phase comprising titanium oxide, aluminum oxide, zirconium oxide, zinc oxide, tin oxide, germanium oxide, cerium oxide, manganese dioxide, copper oxide, ruthenium oxide, or a combination thereof.
9. A method of forming a crystalline metal oxide comprising:
forming a water-free solution by mixing a block copolymer comprising a hydrophilic polymer block and a rigid non-hydrophilic polymer block, an alcohol solvent capable of a dehydration reaction, and one or more metal precursor compounds;
solvothermally treating the water-free solution to generate water for a sol-gel reaction of the one or more metal precursor compounds to form a crystalline metal oxide phase within the hydrophilic polymer block and supported by the rigid polymer block of the block copolymer; and
removing the block copolymer to form a porous crystalline metal oxide.
10. The method of claim 9 , wherein the block copolymer comprises poly-(ether block amide), poly-(ether block imide), poly(ether block aramide), or a combination thereof.
11. The method of claim 9 , further comprising increasing a temperature of the water-free solution to a dehydration temperature of the organic solvent, wherein the dehydration temperature ranges from about 100° C. to about 200° C.
12. The method of claim 9 , wherein the alcohol solvent comprises ethanol, isopropanol, butanol, glycol, glycerol, or a combination thereof.
13. The method of claim 9 , wherein the one or more metal precursor compounds comprise TiCl 4 , TiOSO 4 , tetraisopropyl titanate (TIPT), titanium diisopropoxide bis(acetylacetonate), AlCl 3 , aluminum alkoxide, aluminum formate, zirconium n-butoxide, zirconium acetylacetonate, or a combination thereof.
14. The method of claim 9 , wherein the porous crystalline metal oxide has a BET surface area ranging from about 200 m 2 /g to about 650 m 2 /g.
15. The method of claim 9 , wherein the porous crystalline metal oxide has an average pore size ranging from about 1 nm to about 10 nm.
16. A method of forming a crystalline titanium oxide comprising:
forming a water-free homogeneous solution by mixing a block copolymer comprising a hydrophilic polymer block and a rigid hydrophobic polymer block, an alcohol solvent capable of a dehydration reaction, and at least one titanium precursor compound comprising TiCl 4 , TiOSO 4 , tetraisopropyl titanate (TIPT), titanium diisopropoxide bis(acetylacetonate), or a combination thereof;
increasing a temperature of the water-free solution to dehydrate the alcohol solvent such that the titanium precursor compounds react to form a crystalline titanium oxide phase within the hydrophilic polymer block and supported by the rigid hydrophobic polymer block; and
removing the block copolymer to form a porous crystalline titanium oxide.
17. The method of claim 16 , wherein the block copolymer is a poly-(ether block amide) having a general formula of (A-B) n , where A is a rigid hydrophobic polyamide and B is a soft hydrophilic polyether.
18. The method of claim 16 , further comprising forming a porous crystalline titanium oxide comprising an anatase, a rutile, a brookite, or a combination thereof.
19. The method of claim 16 , further comprising forming an anatase phase, a mixture of anatase and rutile, or a rutile by increasing a ratio of TiCl 4 /TIPT.
20. The method of claim 16 , further comprising increasing a surface area of the porous crystalline titanium oxide by increasing a ratio of the block copolymer to Ti from the titanium precursor compound, wherein the surface area ranges from about 250 m 2 /g to about 350 m 2 /g for the porous crystalline titanium oxide.