FUNCTIONAL POROUS PARTICLES EMBEDDED/IMMOBILIZED WITHIN POROUS STRUCTURES, FORMATION & USES THEREOF

Abstract

In one aspect, a composite porous composition is disclosed, which comprises a porous structure including a plurality of pores, and a plurality of functional particles distributed within at least some of said pores of the porous structure, wherein the particles comprise porous particles.

Claims

1. A composition, comprising: a macroscopic porous structure including a plurality of pores, and a plurality of functional particles coupled to said macroscopic porous structure, wherein said functional particles comprise porous particles.

2. The composition of claim 1, wherein said pores of said macroscopic porous structure have pore sizes in a range of about 100 nm to about 5 mm.

3. The composition of claim 1, wherein each of said functional porous particles comprises a plurality of pores with sizes in a range of about 0.5 nm to about 100 microns.

4. The composition of claim 3, wherein said functional porous particles have a size in a range of about 50 nm to about 2 mm.

5. The composition of claim 1, wherein said functional porous particles are distributed within at least a portion of the pores of the macroscopic porous structure.

6. The composition of claim 5, wherein at least one of said pores of the macroscopic porous structure comprises a plurality of functional porous particles.

7. The composition of claim 1, wherein at least a portion of said functional porous particles are at least partially embedded in one or more structural elements of said macroscopic porous structure.

8. The composition of claim 1, further comprising at least one functional component coupled to at least one of said functional porous particles.

9. The composition of claim 8, wherein said at least one functional component is deposited on an inner surface of a wall of a pore of said at least one of said functional porous particles.

10. The composition of claim 8, wherein said at least one functional component is embedded at least partially within a wall of a pore of said at least one of said functional porous particles.

11. The composition of claim 8, wherein said functional components have a size in a range of about atom size to about 500 nm.

12. The composition of claim 8, wherein said at least one functional component comprises a metallic particle.

13. The composition of claim 1, wherein said macroscopic porous structure comprises a plurality of discrete structures assembled relative to one another to form said macroscopic porous structure.

14. The composition of claim 1, wherein said macroscopic porous structure comprises a single unitary structure.

15. The composition of claim 1, wherein said macroscopic porous structure comprises a material of natural origin.

16. The composition of claim 15, wherein said material of natural origin comprises any of a protein- or polysaccharide-based material, silk fibroin, chitin, shellac, cellulose, hemp, chitosan, alginate, gelatin, or a mixture thereof.

17. The composition of claim 1, wherein said macroscopic porous structure comprises an inorganic material.

18. The composition of claim 17, wherein said inorganic material comprises any of silica, alumina, titania, ceria, zirconia, vanadia, yttria, neodia, hafnia, and combinations thereof.

19. The composition of claim 1, wherein said macroscopic porous structure comprises a polymeric material.

20. The composition of claim 19, wherein said polymeric material comprises any of polyurethane, polystyrene, poly(methyl methacrylate), polyacrylate, poly(alkyl acrylate), substituted polyalkylacrylate, polystyrene, poly(divinylbenzene), polyvinylpyrrolidone, poly(vinylalcohol), polyacrylamide, poly(ethylene oxide), polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, other halogenated polymers, hydrogels, organogels, and combinations thereof.

21. The composition of claim 1, wherein said functional porous particles comprise any of metallic, inorganic, organic, and biological materials or combinations thereof.

22. The composition of claim 21, further comprising at least one functional component coupled to at least one of said functional porous particles.

23. The composition of claim 22, wherein said at least one functional component comprises any of a metal, a metal oxide, a polymer, a natural or a biological material.

24. The composition of claim 1, wherein said macroscopic porous structure exhibits a porosity in a range of about 10% to about 90%.

25. The composition of claim 1, wherein said macroscopic porous structure comprises any of a metal, a metal alloy or a combination thereof.

26. The composition of claim 25, wherein said metal comprises any of copper, nickel, cobalt, gold, silver, titanium, tungsten, aluminum, palladium, platinum.

27. The composition of claim 25, wherein said metal alloy comprises any of stainless steel, brass, FeCrAl (iron-chromium-aluminum alloy), ferritic steel, austenitic steel (a chromium-nickel alloy).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0047] FIG. 1A schematically depicts a CPM according to an embodiment of the present teachings,

[0048] FIG. 1B schematically depicts the MPS matrix of the CPM depicted in FIG. 1A,

[0049] FIG. 1C schematically depicts the assembly of various components forming the CPM depicted in FIG. 1A,

[0050] FIG. 2A schematically depicts a CPM according to another embodiment of the present invention,

[0051] FIG. 2B schematically depicts the MPS matrix of the CPM depicted in FIG. 2A,

[0052] FIG. 2C schematically depicts the assembly of various components of the CPM depicted in FIG. 2A,

[0053] FIG. 3A schematically depicts a CPM according to another embodiment of the present teachings,

[0054] FIG. 3B schematically depicts the MPS matrix of the CPM depicted in FIG. 3A,

[0055] FIG. 3C schematically depicts the assembly of various components of the CPM depicted in FIG. 3A,

[0056] FIGS. 4A and 4B are flow charts depicting various steps in examples of methods for forming a CPM according to some embodiments of the present teachings,

[0057] FIG. 5A shows SEM images of porous alumina microparticles (alumina FPPs) exhibiting a non-spherical shape,

[0058] FIG. 5B shows SEM images of spherical silica microparticles (silica FPPs),

[0059] FIG. 5C shows SEM images of mixed compositioncopper/alumina FPPs with a spherical shape,

[0060] FIG. 5D shows SEM images of compound alumina/polystyrene microparticles with a spherical shape,

[0061] FIG. 5E shows SEM images of Pd/alumina FPPs having a bawl-like shape,

[0062] FIG. 5F shows a magnified SEM image of Pd/alumina FPPs shown on FIG. 5E where Pd FCs (indicated with arrows) are distributed on the surface of a porous structure according to an embodiment of the present teachings,

[0063] FIGS. 6A and 6B present photographs of a material having a plurality of channels in which at least a portion of some of the channels are coated with a CPM according to some embodiments of the present teachings,

[0064] FIG. 6C shows an SEM image the CPM deposited on internal channels of the porous substrate depicted in FIGS. 6A and 6B,

[0065] FIG. 6D is a magnified view of an encircled portion of the SEM image depicted in FIG. 6C,

[0066] FIG. 7A presents a photograph of a foam-like scaffold coated with a CPM according to an embodiment of the present teachings,

[0067] FIG. 7B presents an SEM image of a portion of the coated foam-like scaffold depicted in FIG. 7A,

[0068] FIG. 7C is a high magnification SEM image showing the CPM shown in FIG. 7B (the inset shows a magnification of a portion of the SEM image),

[0069] FIG. 8A presents light-off conversion curve of cyclohexane to CO.sub.2 by a Pd/Alumina FPPs powder according to an embodiment of the present teachings, and

[0070] FIG. 8B presents the light-off curve for the conversion of cyclohexane using a corrugated FrCrAl monolith modified by a CPM incorporating Pd/Alumina FPPs.

DETAILED DESCRIPTION

[0071] The present teachings are generally directed to porous matrices, functional porous particles (FPPs), functional components (FCs), which can be combined in composite porous materials (CPMs), which can be employed in a plurality of different applications. Various terms are used herein according to their ordinary meanings in the art. The term about as used herein to modify a numerical value is intended to indicate variation of at most 10 percent around that numerical value. The term nanoparticle as used herein refers to particles having a maximum dimensional size (e.g., a diameter or a maximum cross-sectional size) equal to or less than 1 micrometer (micron), e.g., in a range of about 0.5 nm to about 100 nm.

[0072] With reference to FIGS. 1A, 1B, and 1C, a CPM 100 according to an embodiment includes an MPS 102 formed by a plurality of discrete components 102a, which are assembled so as to form a porous matrix with pore sizes, e.g., diameters or other cross sections, e.g., in the case of high aspect ratio pores, in a range of about 100 nm to about 5 mm, e.g., in a range of about 400 nm to about 3 mm, or in a range of about 600 nm to about 1 mm, or in a range of about 800 nm to about 0.8 mm, or in a range of about 1000 nm to about 500 microns, or in a range of about 2000 nm to about 200 microns, or in a range of about 2500 nm to 100 micron. In some embodiments, the porosity of the MPS (i.e., the ratio of the volume of the pores relative to the total volume of the MPS) can be, for example, in a range of about 10% to 90%, e.g., in a range of 20% to about 80%, or in a range of about 30% to about 70%, or in a range of about 40% to about 60%, or in the range of about 50% to about 70%.

[0073] MPS 102 can be formed of a variety of suitable materials, such as the materials discussed above including various combinations of those materials. A plurality of FPPs 110 can be distributed within the pores of the porous matrix generated via assembly of the discrete components 102a. In some embodiments, the FPPs can have a size, for example, a diameter or another cross-sectional dimension, in a range of about 50 nm to about 2 mm, (e.g., in a range of about 200 nm to about 1 mm, or in a range of about 600 nm to about 0.5 mm), such as in a range of about 1000 nm to about 200 microns (e.g., in a range of about 2000 nm to about 100 microns), or in a range of about 5000 nm to about 50 microns.

[0074] In some embodiments, the FPPs 110 are fixedly attached to the porous matrix while in other embodiments, at least a portion of the FPPs 110 can move through some of the pores of the porous matrix without exiting the porous matrix due to physical barriers such as narrow channels (smaller than the FPP size) connecting adjacent pores of the MPS.

[0075] The discrete components 102a and the FPPs can be formed, for example, of the materials discussed above. Further, the FPPs can be functionalized with a variety of FCs, such as those discussed above. Some examples of FCs can include, without limitation, metal and/or metal oxide nanoparticles having sizes in the range of about 1 nm to about 20 nm, complex salts with alkali, alkali-earth, and group (III) metals and/or transition metal salts such as salts of nickel, copper, cobalt, manganese, magnesium, chromium, iron, platinum, tungsten, zinc, or other metals. In some embodiments, the FPPs can exhibit a porosity in a range of about 10% to about 90%, for example, in a range of about 28% to about 80%, or in a range of about 30% to about 70%, or in a range of about 30% to about 70%.

[0076] In some embodiments, the material(s) from which the MPS 102 is formed can be the same as the material(s) from which the FPPs are formed, but without the FCs that are added to the FPPs for their functionalization. In other embodiments, the MPS 102 and the FPPs can be formed of different materials.

[0077] In some embodiments, the FCs include one or more biologically derived materials, such as enzymes and proteins.

[0078] While in this embodiment a plurality of FPPs is distributed within one or more pores of the porous matrix generated via assembly of the discrete components 102a, in other embodiments the porous matrix formed, for example, via assembly of the discrete components 102a does not include the FPPs. In other words, in some such embodiments, the present teachings can provide a porous macroscopic structure having a plurality of pores having the sizes described above. For example, in some embodiments, the porous matrix can have pore sizes, e.g., diameters or other cross sections, e.g., in the case of high aspect ratio pores, in a range of about 100 nm to about 5 mm, e.g., in a range of about 400 nm to about 3 mm, or in a range of about 600 nm to about 1 mm, or in a range of about 800 nm to about 0.8 mm, or in a range of about 1000 nm to about 500 microns, or in a range of about 2000 nm to about 200 microns, or in a range of about 2500 nm to 100 micron. In some embodiments, the porosity of the MPS (i.e., the ratio of the volume of the pores relative to the total volume of the MPS) can be, for example, in a range of about 10% to 90%, e.g., in a range of 20% to about 80%, or in a range of about 30% to about 70%, or in a range of about 40% to about 60%, or in the range of about 50% to about 70%. Further, while in some embodiments such a porous matrix can be formed as an assemblage of a plurality of discrete components in other embodiments, the porous matrix can be formed as an integral unit, e.g., via fusing the discrete components together. Such a macroscopic porous structure can be employed in a variety of different applications, e.g., without limitation, gas or liquid phase purification, sorption, separation, energy conversion and storage, catalysis, sensing, electronics, drug delivery, tissue engineering, construction, and additive manufacturing.

[0079] In some embodiments in which CPMs according to the present teachings are employed for catalysis, the catalytic function can be achieved, for example, via heating the CPMs to elevated temperatures, for example, to a temperature in a range of about 50 C. to about 1500 C., e.g., 100 C., 150 C., 200 C., or 500 C.

[0080] As noted above, in some embodiments, a CPM according to the present teachings can be used to at least partially coat the inner surfaces of one or more pores of a porous structure. In some such embodiments, the coating as well as the coated porous structure can be considered as a CPM as disclosed herein. In other words, in some embodiments, a material structure according to the present teachings can include a hierarchy of CPMs, e.g., where a CPM can incorporate one or more other CPMs.

[0081] Referring again to FIGS. 1A, 1B, and 1C as well as the flow charts of FIG. 4A and 4B, one method for fabrication of the CPM 100 includes generating a formulation including compound FPPs (pores are still filled), an MPS precursor, a plurality of FCs, optionally binders, dispersants, stabilizers, pore forming agents, surface modifiers, and other additives. The formulation can be extruded, casted, sprayed, and applied onto a substrate in the form of a coating and at least a part of the templating portion of the FPPs can be removed. The fabrication method can further include post modifying the CPMs.

[0082] An example of post modification of the CPMs include, without limitation, thermal treatment, irradiation, deposition of catalytic nanoparticles, impregnation with various salts, binding of enzymes, surface functionalization with a function providing improved dispersibility, stimuli-responsive molecules (e.g., oligonucleotides, and hydrogels), and functions to adjust surface hydrophobicity. An example includes hydroxylation of surface, silanization of surface using organosilanes (e.g., octadecylotrichlorosilane, fluoroalkyl silane, aminopropyltriethoxy silane, aminopropyltrimethoxy silane) and modification with thiol derivatives. The post modification can be performed homogeneously throughout the exposed surfaces or predominantly at specific locations.

[0083] Another example includes generating a formulation including FPPs from which at least part of the templating material was removed, an MPS precursor, a plurality of FCs, optionally binders, dispersants, stabilizers, pore forming agents, surface modifiers, and other additives and applying the formulation onto a substrate in the form of a coating, casting, or an extruded layer. The final steps of fabrication may include post modification of the CPMs.

[0084] With reference to FIGS. 2A, 2B, and 2C, a CPM material 200 according to another embodiment includes an MPS 201 formed as an arrangement of a plurality of elongated elements 202 that are assembled relative to one another so as to form a porous structure. Similar to the porous material 100, a plurality of FPPs 203 are distributed within the pores of the MPS 201. The FPPs 203 are similar to the FPPs 110. Similar to the FPPs 110, the porous particles 203 can be functionalized, e.g., in a manner discussed above. Some examples of functional components can include, without limitation, precious metals, non-precious metals, and metal oxide nanoparticles, complex salts with alkali, alkali-earth, and group (III) metals and/or transition metal salts.

[0085] A fabrication method similar to that described above in connection with the CPM 100 can be employed to fabricate the CPM material 200.

[0086] As noted above, in some embodiments, the FPPs can be at least partially embedded in the structural elements of the porous matrix (MPS). With reference to FIGS. 3A, 3B, and 3C, a CPM 300 according to such an embodiment can include a plurality of elements 301 that are formed in the presence and around a plurality of FPPs to form a CPM 300. A plurality of FPPs 303 are partially or wholly embedded in at least some of the elements 301.

[0087] Further, in some embodiments, some of the FPPs can be distributed within the pores of the porous matrix and some of the FPPs can be embedded within the structural elements of the matrix, for example, as shown in FIG. 3C.

[0088] As noted above, a variety of FPPs formed of a variety of different materials and having a variety of different shapes can be used in the practice of the present teachings. By way of example, FIGS. 5A, 5B, 5C, 5D, and 5E show Scanning Electron Microscopy (SEM) images of some examples of FPPs that can be employed. Specifically, FIG. 5A shows porous alumina microparticles exhibiting a deflated ball shape. FIG. 5B shows porous spherical silica microparticles, FIG. 5C shows spherical microparticles formed as a mixed copper/alumina oxide composition exhibiting internal porous structure (inset), FIG. 5D shows compound FPPs formed of alumina matrix and spherical polystyrene templating colloids; FIG. 5E shows porous alumina microparticles having a bowl-like shape, and FIG. 5F shows Pd functional nanoparticles (FCs, indicated with arrows) that are distributed on the surface of a porous structure according to an embodiment of the present teachings.

[0089] The FPPs shown in FIGS. 5A, 5B, 5C and 5E were synthesized using spray drying. The FPPs employed in the practice of the present teachings can have a variety of shapes and are generally formed as high surface area porous materials with an interconnected network of pores. Some shapes can have especially advantageous properties for specific applications. For example, FPPs with a spherical, toroid-like, bowl-like, or punctured/deformed sphere morphology, e.g., as shown in FIG. 5E, can enable improved diffusion and mass transport properties in catalytic applications.

[0090] FIGS. 6A, 6B, and 6C show examples of CPM-modified internal channels of a FeCrAl monolith and FeCrAl foam, respectively, with a CPM including Pd/Alumina FPPs shown in FIG. 5E. More specifically, FIGS. 6A and 6B show the top view (FIG. 6A) and side view (FIG. 6B) photographic images of FeCrAl monolith substrate. FIG. 6C shows an SEM image of the CPM deposited on internal channels of the monolith. FIG. 6D presents a zoomed-in image of an FPP similar to the encircled portion in FIG. 6C.

[0091] FIG. 7A presents a photograph of a foam-like scaffold coated with a CPM according to an embodiment of the present teachings, where the scaffold is formed of FeCrAl alloy and the CPM coating includes Pd/Alumina FPPs. FIG. 7B presents an SEM image of a portion of the coated foam-like scaffold depicted in FIG. 7A. And FIG. 7C is a high magnification SEM image showing the CPM depicted in FIG. 7B (the inset shows a magnification of a portion of the SEM image)

[0092] The structures shown in FIGS. 6A, 6B, and 6C, as well as FIGS. 7A, 7B, and 7C are examples of material structures that can be viewed as being formed as a plurality of hierarchical CPMs. For example, the coating provided on the surfaces of the internal pores can be viewed as a CPM. Further, the entire material structure can also be viewed as a CPM.

[0093] By way of further illustration, FIGS. 8A and 8B present light-off curves (concentration as a function of the reaction temperature) for the conversion of cyclohexane to carbon dioxide using Pd/Alumina FPPs (i.e., alumina FPPs with Pd nanoparticles as FCs, shown in FIG. 5E) in a form of a powder subjected to a stream of 0.6 L/min cyclohexane (FIG. 8A) and as a part of a CPM on a FeCrAl monolith subjected to 5 L/min cyclohexane stream (FIG. 8B), according to some embodiments of the present teachings.

[0094] The porous materials according to the present teachings can find a variety of different applications. Some examples of such applications include, without limitation, gas or liquid phase purification, sorption, separation, energy conversion and storage, catalysis, sensing, electronics, drug delivery, tissue engineering, construction, and additive manufacturing.

[0095] Example of an Experimental Procedure for the Synthesis of FPPs

[0096] The FPPs discussed above in connection with FIGS. 5A-E were fabricated using a spray drying method. Dispersions of polystyrene templating colloids and matrix precursors were atomized using a spray nozzle. The inlet temperature for various experiments was kept in the range of 100-190 C. The obtained microparticles were heat treated at 500-800 C. to remove templating colloids to form FPPs. Compound alumina microparticles (FIG. 5D) and alumina FPPs (FIG. 5A) were synthesized using aqueous dispersions of polystyrene colloids with alumina precursor (3 wt. %). Silica FPPs (FIG. 5B) and mixed Cu/alumina FPPs (FIG. 5C) were synthesized in a similar manner using a dispersion of silica nanoparticles and a mixture of alumina precursor and copper (II) nitrate accordingly. Alumina FPPs decorated with Pd FCs (FIG. 5E) were obtained using Pd modified polystyrene colloids as a templating material.

Coating of FeCrAl Monoliths and Foams by CPM

[0097] Commercially available FeCrAl corrugated monoliths with parallel channels and FeCrAl foams were used as substrates for the deposition of a CPM including Pd/alumina FPPs on their internal channels. The samples (2 inch length and 1 inch in diameter) were first cleaned by sonication in acetone to remove soluble impurities and any dust produced during manufacturing processes. Cleaned and dried samples were submerged in a slurry containing aqueous Pd/a lumina FPPs (15 wt.%) for 1 min, then the excess slurry was removed via air blowing through the channels. The samples were then dried followed by heat treatment at 500 C. for 2 h.

[0098] Those having ordinary skill in the art will appreciate that various changes can be made to the above embodiments without departing from the scope of the invention.