Graphene oxide membranes, methods of making same, and uses thereof

Abstract

Graphene oxide (GO) membranes, methods of making graphene oxide membranes, and uses of GO membranes. In various examples, a GO membrane (e.g., a "stitched" GO membrane) comprises one or more layer(s), each layer comprising GO oxide flakes, where the only fluidic connection between opposite sides of the layer(s) is / are formed by in-plane defect(s) and / or pore(s) of the GO flakes and / or the GO membrane comprises a plurality of impermeable material domains disposed on a surface or surfaces of the GO flakes. In various examples, a method of making a GO layer comprises contacting a layer comprising GO flakes (e.g., in a molecular layer deposition process) with one or more vapor-phase precursor(s) and, optionally, one or more vapor-phase carbon precursor(s), such that a plurality of material domains are formed. In various examples, a system or a method for small molecule separation and / or enrichment uses or comprises one or more GO membrane(s).

Description

GRAPHENE OXIDE MEMBRANES, METHODS OF MAKING SAME, AND USES THEREOFCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 596,293, filed November 5, 2023; the contents of the above-identified application are hereby fully incorporated herein by reference in their entirety.BACKGROUND

[0002] The separation of small molecules, such as, for example, hydrocarbons with 5 to 8 carbon atoms, xylenes, alcohols, with similar polarity and sizes between 4 and 7 A, is both industrially important and highly challenging. Traditional separation methods, such as, for example, distillation, involve phase changes and utilize volatility differences, making them highly energy-intensive and sometimes requiring many stages. As a promising alternative technology, membrane-based organic solvent reverse osmosis (OSRO) can eliminate phase change, and thus drastically reduce energy consumption. Membranes fabricated from various building blocks / materials, including inorganic materials, such as, for example, MFI zeolite and carbon molecular sieves, hybrid materials, such as, for example, metal-organic frameworks, and polymers, such as, for example, cellulose acetate butyrates, polytriazole, and contorted polymers, have been investigated for these separations. Due to the similar polarity of these molecules and moderate to high operation pressure in OSRO, microporous membranes utilizing small molecular size / shape differences and having rigid pores under separation conditions are highly desired. Current OSRO membranes with rigid micropores, typically inorganic and hybrid membranes, often require a substantial thickness, sometimes up to a few micrometers, to ensure the formation of a defect-free, continuous layer, thus significantly compromising permeance. Furthermore, tuning micropores within the range of 4 to 7 A to precisely differentiate organic molecules and thus achieve highly selective OSRO remains very challenging for current OSRO membranes.

[0003] Many membrane-based separations rely on the polarity of solvents; for example, polymers like cellulose acetate butyrate have been used for such separation but have shown promising separation performance for molecule pairs such as, for example, methanol / pentane or methanol / heptane, where one of the molecules is polar in nature and another non-polar in nature. In such cases, the surface of the membrane and the polarity of the membrane pore plays an imp critical role. Having a membrane which is polar in nature will attract the polar molecules from the mixture preferentially over the non-polar ones. With a pore size close tothe molecular sizes, the preferential adsorption of the polar molecule will block the transport of the non-polar molecule in the mixture, thus separating them into their pure components. In such a case, the degree of polarity of the membrane and its pore sizes (pore sizes do not have to be in between the two molecules of interest, but in the range close to the molecules) plays the major role in determining the efficiency of the membrane.

[0004] Whenever these membranes are challenged with a mixture of molecules having the same or similar polarity, these membranes fail to separate them. Nevertheless, separation of such molecules having similar polarity is critical in industry, especially separation of high value hydrocarbon separation in the downstream of the petroleum refinery, for example, o- xylene / p-xylene separation is crucial as p-xylene is used as a feedstock for the synthesis terephthalic acid (TP A), a monomer for the polyethylene terephthalate (PET) plastics. Such separations in the industry are very energy inefficient, as these molecules often have very close boiling points and other similar physiochemical properties. Thus, their size differences are the only feature that could be exploited for designing a physical separation process. For this reason, a membrane that has pores sizes right in between the molecules of interest, could serve as an ultimate separation medium.

[0005] However, like the challenges in designing adsorbents, designing size-sieving membranes is extremely challenging. Although there are numerous zeolitic or zeotype, and MOF materials (for example, zeolites such as NaA, SAPO-34 or MOFs like ZIF-8) that can serve as material for size sieving in the 3-4 A range, there is a clear gap in materials having pore sizes suitable for separation of molecules having kinetic diameter in the size range of 4- 7 A. The only two materials that have been well studied, and having pore sizes in this range, are zeolites having MFI type frameworks (for example, Zeolite Socony Mobil-5 zeolite) and carbon molecular sieves (CMS). Thus there is a clear lack of materials targeting size-based separation for molecules between 4-7 A, and new microporous materials have to be designed, or preexisting materials have to be re-designed in innovative ways to fill up this material gap.

[0006] Thickness reduction is an obvious route to realize high permeance. Two dimensional (2D) materials, such as, for example, graphene oxide (GO), MXenes, and hexagonal boron nitrides, are promising for fabricating ultrathin membranes due to their atomic thinness and high aspect ratio and presence of in-plane pores / defects for transport. GO flakes, owing to ease of synthesis, rich oxygen-containing functional groups, and favored water dispersibility, are the most widely investigated 2D material for membrane fabrication. They are typically stacked into ultrathin membranes with lamellar structures for separation applications. In such membranes, interlayer nanochannels play an important role to provideselectivity but often fail to reject small organic solvent molecules due to relatively large nanochannel width and membrane swelling in liquid.SUMMARY OF THE DISCLOSURE

[0007] The present disclosure provides, inter alia, graphene oxide membranes. The present disclosure also provides methods of making and uses of graphene oxide membranes.

[0008] In an aspect, the present disclosure provides graphene oxide membranes. In various examples, a graphene oxide membrane comprises a plurality of “stitched” graphene oxide flakes (e.g., graphene oxide flakes laterally and / or vertically “stitched”). In various examples, a graphene oxide membrane is made by a method of the present disclosure. In various examples, a graphene oxide membrane comprises a substrate; and a layer (a graphene oxide layer) comprising a plurality of graphene oxide flakes, where at least a portion of, substantially all, or all the graphene oxide flakes are disposed on at least a portion or all the exterior surface(s) of the substrate. In various examples, the only fluidic connection between opposite sides of the layer (the graphene oxide layer) is formed by in-plane defect(s) and / or pore(s) of the graphene oxide flakes and / or the graphene oxide membrane comprises a plurality of material domains comprising a material (e.g., an impermeable material, such as, impermeable to hydrocarbons, alcohols, and the like, and any combination thereof) and each of the material domains is disposed on a surface or surfaces, or an in-plane defect or in-plane defect edges, or the like, or any combination thereof of one or more of the graphene oxide flake(s) and / or seal at least a portion of or all the pores or in plane defects of one or more of the graphene oxide flakes. The layer may comprise a plurality of individual layers. In various examples, the graphene oxide flakes of the layer(s) (the graphene oxide layer or layers) are, independently, single-layer graphene flakes, multilayer graphene flakes, or the like, or any combination thereof. In various examples, at least a portion of, substantially all, or all the graphene oxide flakes each comprise one or more in-plane defects and / or pores.

[0009] In an aspect, the present disclosure provides methods of making graphene oxide membranes. In various examples, a method produces one or more graphene oxide membrane(s) of the present disclosure. In various examples, a method of making one or more graphene oxide membrane(s) comprises forming a layer (a graphene oxide layer) comprising a plurality of graphene oxide flakes on at least a portion of, substantially all, or all of the exterior surfaces of a substrate (e.g., using an aqueous dispersion of graphene oxide flakes or the like); optionally, drying the layer; and contacting the layer (e.g., the dried layer) with one or more vapor-phase precursor(s) (e.g., using a molecular layer deposition) and, optionally,one or more vapor-phase carbon precursor(s), such that a plurality of material domains are formed. In various examples, the graphene oxide flakes are, independently, single-layer graphene oxide flakes, multilayer graphene oxide flakes, or the like. In various examples, a combination of two or more different (e.g., structurally and / or compositionally different) graphene oxide flakes is used. In various examples, the graphene oxide flakes comprise a plurality of oxygen-containing groups (such as, for example, hydroxyl groups, carboxylate groups, ketone groups, or the like, or any combination thereof). In various examples, a least a portion, substantially all, or all the graphene oxide flakes comprise a plurality of oxygencontaining groups disposed on the edges and / or edges of the in-plane pores and / or in-plane defects of the graphene oxide flakes. In various examples, the graphene oxide flakes are present in an aqueous solvent (e.g., water or the like) (such as, for example, an aqueous dispersion of graphene oxide flakes or the like). In various examples, the contacting a layer with one or more vapor-phase precursor(s) is carried out in (or as part of) a vapor-phase molecular layer deposition (MLD) process or the like.

[0010] In an aspect, the present disclosure provides systems. In various examples, a system comprises one or more graphene oxide membrane(s) of the present disclosure and / or one or more graphene oxide membrane(s) made by a method of present disclosure. In various examples, the system is a separation system, filtration system, or the like. In various examples, the separation system is an organic solvent reverse osmosis system, a membrane based organic solvent reverse osmosis (ORSO) system or the like), a reverse osmosis desalination system, a gas separation system, or the like comprising one or more graphene oxide membrane(s) of the present disclosure and / or one or more graphene oxide membrane(s) made by a method of present disclosure.

[0011] In an aspect, the present disclosure provides uses of graphene oxide membranes of the present disclosure and / or graphene oxide membranes made by a method of present disclosure. In various examples, a graphene oxide membrane or graphene oxide membranes (or a system comprising graphene oxide membrane(s)) is / are used in a separation and / or enrichment process. In various examples, the separation process is an organic solvent reverse osmosis (OSRO) process / application (such as, for example, a membrane based organic solvent reverse osmosis (ORSO) process / application, a reverse osmosis desalination process / application, a gas separation process / application, or the like. In various examples, the method separates one or more small molecule(s) and / or enriches one or more small molecule(s) (which may be present in a composition). In various examples, a method of separating one or more small molecule(s) from and / or enriching one or more smallmolecule(s) of a composition comprising two or more small molecules (e.g., different and / or distinct small molecules) (such as, for example, hydrocarbons, alcohols, or any combination thereof) comprises contacting the composition (e.g., the mixture or the like) with one or more graphene oxide membrane(s) of the present disclosure and / or one or more graphene oxide membrane(s) made by a method of present disclosure, where one or more of the small molecule(s) (such as, for example, the hydrocarbon(s)) is / are separated from the composition and / or enriched in the composition. A method can be used to separate or enrich various small molecules in or from various compositions. In various examples, the composition is a petroleum distillation product (e.g., a petroleum distillation fraction), a gas composition, seawater, or the like.

[0012] In various examples, the present disclosure provides graphene oxide membranes (e.g., an ultrathin OSRO membrane) fabricated by combining a 2D material and a MLD process and achieved precise pore size control in 0.4 to 0.7 nm range for organic solvent separation.BRIEF DESCRIPTION OF THE FIGURES

[0013] For a fuller understanding of the nature and objects of the disclosure, reference should be made to the following detailed description taken in conjunction with the accompanying figures.

[0014] FIGS. 1A-1E show a fabrication and characterization of “stitched” graphene oxide (SGO) membranes. FIG. 1A shows a schematic showing the fabrication of lamellar GO coating on porous ceramic substrate, followed by vapor phase preferential titanicone deposition (green) by molecular layer deposition (MLD) at the edges and in-plane pores of GO flakes to form SGO membrane. This forces molecules to be transported through the modified in-plane pores on the GO flakes. FIG. IB shows an atomic force micrograph of a single GO flake modified with MLD, showing preferential deposition of titanicone at the edges of the GO flake (left); the height profile of the modified GO flake along the blue line (right). FIG. 1C shows a scanning electron microscopy (SEM) image of SGO membrane surface, showing preferential titanicone deposition along GO flake edges by 60 cycles of MLD. FIG. ID shows a SEM image of the cross section of SGO membrane modified by 10 MLD cycles; a selective layer thickness of 30 nm can be seen. FIG. IE shows interlayer spacing of lamellar-stacked GO coatings, determined by X-ray diffraction patterns; MLD cross-links the GO flakes in the vertical direction (schematic), preventing GO coatings from swelling in liquids.

[0015] FIGS. 2A-2C show pure hydrocarbon permeation, proposed permeation mechanisms of SGO membranes, and molecular dynamics (MD) simulation for permeation through different pathways. FIG. 2A shows permeation of pure hydrocarbons through SGO membranes modified with different MLD cycles. FIG. 2B shows a schematic showing titanicone deposition preferentially blocks the transport through edges of GO, while simultaneously modifying the in-plane pores through which molecular transport takes place. FIG. 2C shows MD simulation investigating the effect of transport in two different pathways. I shows the schematic model shows the microstructure of SGO and effective transport pathway; II shows the estimated pore size distribution of in-plane pores of GO and how they are modified by MLD; and III shows a comparison of the selectivity estimated from MD simulation to that obtained from experiments.

[0016] FIGS. 3 A-3F show organic solvent reverse osmosis (OSRO) performance of SGO membranes for hydrocarbon mixtures. FIG. 3 A shows the enrichment of n-hexane from its binary mixtures with isooctane using SGO- 10 membrane; three mixtures with different n- hexane compositions (95 mol.%, 90 mol.%, and 85 mol.%, respectively) were used as feed; feed pressures were from 20 to 35 bar, as labelled in the figure, and permeate pressure was 1.01 bar. The dashed line represents the estimated composition of the permeating mixture, calculated based on the pure component permeance. FIG. 3B shows the separation factor (top) and osmotic pressure corrected permeance (bottom) for binary n-hexane mixtures as a function of MLD cycles. GO coatings with 30 nm thickness were used for MLD modification. The dashed line indicates pure n-hexane permeance. FIG. 3C shows a comparison of SGO membranes (for n-hexane / isooctane mixtures) with various OSRO membranes reported in the literature for binary mixture separation. Hydraulic permeance is used as x-axis. Grey points denote permeating components are smaller than n-hexane, and black points denote permeating components are larger than n-hexane. Membranes with permeance < 1 x 10'10mol nr2s'1Pa'1are not included in the figure. Details of all reported OSRO membranes are given in Table 2. FIG. 3D shows a proposed application of SGO membranes to separate out the high-octane fraction and sulfur-containing compounds from light naphtha stream before the catalytic reformer. This allows feeding the reformer with only low-octane fraction and thus can reduce its workload. FIG. 3E shows the relative composition of the permeate with respect to the feed for a complex synthetic naphtha mixture separation using SGO- 15 membrane; the composition of the synthetic naphtha is shown in Table 4. The permeated stream gets enriched with linear hydrocarbons that have lower octane number. FIG. 3F shows that over 100-h continuous operation for separation of complex naphthamixture shows a stable performance with a hydraulic permeance of -1.15 X 10'7mol m'2s'1Pa'1for about 70 hours; the permeated stream shows a stable RON of 33, corresponding to -95% of the largest possible RON reduction. The largest possible RON reduction is defined as the RON difference between feed and a hypothetical stream composed of only linear alkanes with the same molar ratio as the feed.

[0017] FIGS. 4A-4F show characterizations to demonstrate successful preparation of graphene oxide from expandable graphite. FIG. 4A shows X-ray photoelectron spectroscopy shows introduction of oxygen groups as opposed to graphite. FIG. 4B shows a detailed deconvolution of Ols peak of graphene oxide showing the different functional groups present in GO. FIG. 4C shows X-ray diffraction patterns showing the formation of single layer graphene oxide. The shift of peak in the reciprocal place from 26° to 10° indicates the spacing between layers to be in between 0.9 to 1 nm indicating formation of graphene oxide. FIG. 4D shows a thermogravimetric analysis that shows loss of functional groups when graphene oxide is heated in nitrogen atmosphere, which is typical of graphene oxide. FIGS. 4E and 4F shows AFM image of a GO flake showing height of -1 nm, consistent with previous literature reports.

[0018] FIG. 5A shows scanning electron microscopy of pristine GO membrane showing a thickness of - 40 nm. This corresponds to a GO loading of 44.3 mg m'2. FIG. 5B shows a GO membrane thickness for a corresponding GO loading.

[0019] FIG. 6 shows a detailed chemical reaction of MLD showing two self-limiting surface reactions (1. TiCh reacts with hydroxyl groups and 2. Reaction of hydroxyl groups of glycols with the chlorines) with noble gas purge and vacuum in between to remove excess reactant and byproducts form the reactor.

[0020] FIG. 7A shows X-ray photoelectron spectrographs of full scan of Stitched-GO. FIG. 7B shows X-ray photoelectron spectrographs of full scan of pristine graphene oxide. FIG. 7C shows a detailed scan of O-l s region of stitched-GO. FIG. 7D shows a detailed scan of O-l s region of pristine graphene oxide. FIG. 7E shows a detailed scan of Ti region of the stitched-GO.

[0021] FIG. 8A shows FTIR spectrograph stitched GO (15 cycle) and pristine GO. FIG. 8B shows a detailed scan around the 4000 - 2000 cm'1region of pristine graphene oxide. FIG. 8C shows stitched-GO after 15-cycle MLD. FIG. 8D shows stitched-GO after 30-cycle MLD. FIG. 8E shows stitched-GO after 45-cycle MLD.

[0022] FIGS. 9A-9H show AFM images and height profiles of single flakes of GO deposited on a silicon wafer. FIG. 9A shows AFM image of single GO flakes. FIGS. 9B and9C show height profiles along the line marked as I and II on the AFM image in FIG. 9A shows a consistent ~ 1 nm height of the GO flakes. FIG. 9D shows an AFM image showing a GO flake after 2 cycles of MLD. FIG. 9E shows the height profile of the flake along the line on AFM image in FIG. 9D. FIG. 9F shows an AFM image showing another GO flake after 2 cycles of MLD. FIG. 9G shows the height profile of the flake along the line down on the flake in FIG. 9F. From both the height profiles in FIGS. 9E and 9G, it is evident that there is an increase in height along the edges of the GO. This increase in height along the edges of the GO flakes is due to the titanicone growth after 2 cycles of MLD. The increase in height at the edges is ~1 nm, which is less than the increment seen after 5 cycles of MLD (~3 nm, FIG. IE). These results indicate preferential growth of titanicone on the edges. FIG. 9H shows the surface roughness is reduced due to titanicone deposition.

[0023] FIG. 10 shows a surface SEM image of a 30-nm thick graphene oxide coating after 10 cycles of MLD. Undulation of the undulating nature of the bottom ceramic support is visible due to the thinness of the fabricated graphene oxide coating.

[0024] FIGS. 11 A-l IB show a molecular layer deposition stitches of graphene oxide flakes into a continuous membrane by sealing the gaps between two adjacent parallel flakes at the edges. It also crosslinks the flakes, locking them to form a stable membrane.

[0025] FIGS. 12A-12F show X-ray diffraction patterns of graphene oxide coatings and Stitched-GO in dry and wet (submerged in mixture of hydrocarbons) conditions.

[0026] FIG. 13A-13B show contact angle measurements using 3 pl of ultrapure water. FIG. 13 A shows pristine graphene oxide coating (contact angle = 35.3±1.5°) and FIG. 13B shows stitched GO coating modified with 15 cycle MLD (contact angle = 86.4±0.8°). The reduction of hydroxyl groups is indicated by the higher hydrophobicity of the stitched GO membrane compared to pristine GO membrane as observed clearly from the water contact angle measurement.

[0027] FIG. 14 shows an ideal selectivity of linear hydrocarbon (n-hexane, 4.3 A) over hydrocarbons of different sizes (1-branched: 5.2 A, 2-branched: 6.2 A, 3 branched: 6.9 A, cyclic and aromatic: 6.6 A) for stitched-GO modified with different MLD cycles; GO coating thickness is 30 nm. The selectivity between linear / 1-branched and linear / 2-branched increases from SGO-10 to SGO-15. This is due to shrinkage of pores that allows transport of 1-branched and 2-branched hydrocarbons with increase of MLD cycles, suggesting tunability by changing MLD cycles. Pores available for linear hydrocarbon transport also diminishes. This cuts down permeance of linear hydrocarbon on increasing MLD cycles (30 and 45cycles). This causes lowering of selectivity between linear / 3 -branched, linear / cyclic and linear / aromatic as the number of MLD cycles increases.

[0028] FIGS. 15A-15B show a change in permeance properties of n-hexane and its isomer 2,3-dimethyl butane across SGO-10 (MLD cycles: 10) and SGO-15 (MLD cycles: 15); GO coating thickness is 30 nm. FIG. 15A show 5 additional MLD cycles cause 0.3 times decrease in n-hexane permeance, while larger 2,3-dimethyl butane permeance decreases by 4 times. FIG. 15B show that this causes a 3.34 times increase in ideal selectivity. This shows the A-scale tunability of stitched-GO membranes.

[0029] FIGS. 16A-16D show ideal selectivity between hydrocarbons remains same across stitched-GO membranes with varying GO coating thickness (modified with the same number of MLD cycles). The selectivity between linear (hexane) and 1-branched (3-methyl pentane) (FIG. 16A), linear (hexane) and 2-branched (2,3-dimethyl butane) (FIG. 16B), linear (hexane) and 3-branched (isooctane) (FIG. 16C), and linear (hexane) and cyclic (cyclohexane) (FIG. 16D) is shown.

[0030] FIGS. 17A-17F show that the permeance of hydrocarbons decreases with the thickness of the GO coating in stitched-GO membranes. The decrease in permeance of n- hexane (FIG. 17A), 3-methyl pentane (FIG. 17B), 2,3-dimethyl butane (FIG. 17C), isooctane (FIG. 17D), cyclohexane (FIG. 17E), and toluene (FIG. 17F), is shown across the stitched- GO prepared with different MLD cycles.

[0031] FIG. 18 shows the relationship between permeance and ideal selectivity to describe desired thickness of GO coatings.

[0032] FIG. 19 shows two distinct pathways for entry into a lamellar stacked graphene oxide. Pathway - 1 is the entry into the nanochannel through the edges of the flakes and pathway - 2 is the entry into the nanochannel through the in-plane pores on the GO flake. Stacked GO membranes which have significant flow through pathway - 1, obtains its selectivity from the geometric constraints of the nanochannel spacing, which is hard to tune below its natural size. When transport through pathway - 1 is eliminated, molecules follow pathway - 2, where the sizes of the in-plane pores / defects determine selectivity.

[0033] FIG. 20 shows titanicone deposition with less than 10 MLD cycles is not enough to stitch GO membranes. Less than 10 cycles MLD does not deposit enough material to block the transport pathways through the GO edges. This yields no selectivity. Once the pathways at the edges are sealed (10 MLD cycles and up), the SGO membranes become selective for n- hexane over isooctane. The numbers on the data point represent the number of MLD cycles used to modify a 30-nm GO coating.

[0034] FIG. 21 shows enrichment of n-hexane from 95 mol.% n-hexane / isooctane mixture for SGO-15 membrane under different transmembrane pressures.

[0035] FIGS. 22A-22B show variations of flux (FIG. 22A) and separation (FIG. 22B) factor with transmembrane pressure for 95 mol.% n-hexane / 5 mol.% isooctane mixture through 30 nm thick SGO-10 and SGO-15 membranes.

[0036] FIGS. 23A-23B show variations of hydraulic permeance (FIG. 23 A) and separation factor (FIG. 23B) with the feed n-hexane composition (mol.%) for a binary mixture of n-hexane and isooctane. Transmembrane pressure was set to 30 bar for all feed mixtures, except for 85% n-hexane (transmembrane pressure for this feed mixture is 35 bar).

[0037] FIG. 24 shows the comparison of pure n-hexane permeance and osmotic pressure corrected permeance for n-hexane / isooctane mixture.

[0038] FIG. 25 shows the enrichment of n-hexane from 85 mol.% n-hexane / isooctane mixture using 30 nm thick SGO membrane prepared with 15 cycle MLD having different thickness.

[0039] FIGS. 26A-26B show hydraulic permeance and separation factor variation with GO thickness in SGO membranes with 15 MLD cycles for separation of n-hexane / isooctane binary mixtures. 95 mol.% n-hexane / isooctane mixtures (FIG. 26A); 85 mol.% n- hexane / isooctane mixtures (FIG. 26B).

[0040] FIG. 27 show separation factor and permeance with variation of thickness in SGO membranes modified with 10 MLD cycles for separation of n-hexane / isooctane binary mixtures (composition indicated in figure legend). GO coating thicknesses are 30 and 40 nm, respectively, as labelled in the figure.

[0041] FIGS. 28A-28B show variations of enrichment of n-hexane in permeate with the MLD cycles for a 30-nm thick SGO membrane for 90 mol.% n-hexane / 10 mol.% isooctane mixture (FIG. 28A) and 85 mol.% n-hexane / 15 mol.% isooctane mixture (FIG. 28B).

[0042] FIG. 29A-29C show variations of hydraulic permeance and separation factor for a 30-nm thick SGO membrane with different MLD cycles for 95 mol.% (FIG. 29 A), 90 mol.% (FIG. 29B), and 85 mol.% (FIG. 29C) n-hexane and isooctane mixtures.

[0043] FIG. 30 shows enrichment n-hexane from binary mixtures of 85 mol.% n-hexane and isooctane, toluene, 2,3-dimenthyl butane, and 3-methyl pentane using a 30 nm thick SGO membrane modified with various MLD cycles (the cycle numbers are mentioned in the figure).

[0044] FIG. 31 shows gas chromatography spectra of complex synthetic naphtha feed and permeate (1 : n-pentane, 2: 3-methyl pentane, 3: 2,3-dimethyl butane, 4: n-hexane, 5:thiophene, 6: cyclohexane, 7: isooctane, 8: heptane, 9: toluene). From the thiophene peak (5), it can be observed that a -70% decrease in thiophene concentration in permeate, compared to the feed. It is considered the permeate may be processed in a catalytic reformer. Partially removing thiophene from the reformer feed could reduce the workload for the subsequent hydrodesulfurization process that is essential for preventing the catalytic reformer’s catalyst from poisoning.

[0045] FIG. 32 shows change in the concentration of 8 major hydrocarbon components in the permeate compared to the feed (1 : n-pentane, 2: n-hexane, 3: n-heptane, 4: 3-methyl pentane, 5: 2,3-dimethyl butane, 6: cyclohexane, 7: isooctane, 8: toluene).

[0046] FIG. 33 shows permeance of linear hydrocarbons for 100-hour on stream permeation through SGO-15 membrane. The top line represents total linear hydrocarbons’ permeance.

[0047] FIG. 34 shows molar flux of enriched fraction and stripped fraction and the separation factor between them during 100-hour on stream membrane operation.

[0048] FIGS. 35A-35B show GO membranes assembled into modules.DETAILED DESCRIPTION OF THE DISCLOSURE

[0049] Although subject matter of the present disclosure is described in terms of certain embodiments and examples, other embodiments and examples, including embodiments and examples that do not provide all the benefits and features set forth herein, are also within the scope of this disclosure. For example, various structural, logical, and process step changes may be made without departing from the scope of the disclosure.

[0050] As used herein, unless otherwise indicated, “about”, “substantially”, or “the like”, when used in connection with a measurable variable (such as, for example, a parameter, an amount, a temporal duration, or the like) or a list of alternatives, is meant to encompass variations of and from the specified value including, but not limited to, those within experimental error (which can be determined by, e.g., a given data set, an art accepted standard, etc. and / or with, e.g., a given confidence interval (e.g., 90%, 95%, or more confidence interval from the mean), such as, for example, variations of + / - 10% or less, + / -5% or less, + / -1% or less, and + / -0.1% or less of and from the specified value), insofar such variations in a variable and / or variations in the alternatives are appropriate to perform in the instant disclosure. As used herein, the term “about” may mean that the amount or value in question is the exact value or a value that provides equivalent results or effects as recited in the claims or taught herein. That is, it is understood that amounts, sizes, compositions,parameters, and other quantities and characteristics are not and need not be exact, but may be approximate and / or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off, measurement error, or the like, or other factors known to those of skill in the art such that equivalent results or effects are obtained. In general, an amount, size, composition, parameter, or other quantity or characteristic, or alternative is “about” or “the like,” whether or not expressly stated to be such. It is understood that where “about,” is used before a quantitative value, the parameter also includes the specific quantitative value itself, unless specifically stated otherwise.

[0051] Ranges of values are disclosed herein. The ranges set out a lower limit value and an upper limit value. Unless otherwise stated, the ranges include the lower limit value, the upper limit value, and all values between the lower limit value and the upper limit value, including, but not limited to, all values to the magnitude of the smallest value (either the lower limit value or the upper limit value) of a range. It is to be understood that such a range format is used for convenience and brevity, and thus, should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. To illustrate, a numerical range of “0.1% to 5%” should be interpreted to include not only the explicitly recited values of 0.1% to 5%, but also, unless otherwise stated, include individual values (e.g., 1%, 2%, 3%, and 4%) and the sub-ranges (e.g., 0.5% to 1.1%; 0.5% to 2.4%; 0.5% to 3.2%, and 0.5% to 4.4%, and other possible sub-ranges) within the indicated range. It is also understood (as presented above) that there are a number of values disclosed herein, and that each value is also herein disclosed as “about” that particular value in addition to the value itself. For example, if the value “10” is disclosed, then “about 10” is also disclosed. Ranges can be expressed herein as from “about” one particular value, and / or to “about” another particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms a further disclosure. For example, if the value “about 10” is disclosed, then “10” is also disclosed.

[0052] As used herein, unless otherwise stated, the term “group” refers to a chemical entity that is monovalent (i.e., has one terminus that can be (is) covalently bonded to other chemical species), divalent, or polyvalent (i.e., has two or more termini that can be (are) covalently bonded to other chemical species). The term “group” also includes radicals (e.g., monovalent radicals and multivalent radicals, such as, for example, divalent radicals, trivalentradicals, and the like). Illustrative examples of groups include:the like.

[0053] As used herein, unless otherwise indicated, the term “aliphatic” refers to branched or unbranched hydrocarbon groups (or compounds comprising an aliphatic group, e.g., an aliphatic compound) that, optionally, contain one or more degree(s) of unsaturation. Degrees of unsaturation can arise from, but are not limited to, carbon-carbon double bond group(s), carbon-carbon triple bond group(s), cyclic aliphatic group(s), or the like, or any combination thereof. In various examples, an aliphatic group is a Ci to Cio aliphatic group, including all integer numbers of carbons and ranges of numbers of carbons therebetween (e.g., Ci, C2, C3, C4, Cs, Ce, C7, Cs, C9, or Cio). Aliphatic groups include, but are not limited to, alkyl groups, alkene groups, and alkyne groups, and the like. In various examples, an aliphatic group is unsubstituted or substituted with one or more substituent(s). In various examples, a substituent is a charged substituent (such as, for example, a static charged substituent or a condition (e.g., pH) specific charged substituent). Examples of substituents include, but are not limited to, various substituents such as, for example, halogen groups (-F, -Cl, -Br, and -I), aliphatic groups (e.g., alkyl groups, alkenyl groups, alkynyl groups, and the like), halogenated aliphatic groups (e.g., trifluoromethyl group and the like), aryl groups, halogenated aryl groups, hydroxyl group, amine groups, nitro group, cyano group, isocyano group, azide group, silane groups (e.g., alkyl silane groups, aryl silane groups, alkyl / aryl silane groups, or the like), alkoxide groups, alcohol groups, ether groups, ketone groups, carboxylate groups, carboxylic acid group, ester groups, amide groups, thioether groups, thioester groups, and the like, and any combination thereof.

[0054] As used herein, unless otherwise indicated, the term “alkyl” refers to branched or unbranched hydrocarbon groups (or compounds comprising an alkyl group, e.g., an alkyl compound) that include only single bonds between carbon atoms (not including substituent(s), if any). In various examples, an alkyl group is a Ci to Cio alkyl group (e.g., Ci, C2, C3, C4, C5, C6, C7, C8, C9, or Cio), including all integer numbers of carbons and ranges of numbers of carbons therebetween. In various examples, an alkyl group is a saturated group. In various examples, an alkyl group is a cyclic alkyl group, which may be a heterocyclic alkyl group, e.g., a monocyclic alkyl group or a polycyclic alkyl group or the like, or the like. Examples of alkyl groups include, but are not limited to, methyl groups, ethyl groups, propyl groups, butyl groups, isopropyl groups, tert-butyl groups, cyclohexylgroups, adamantyl groups, benzyl groups and the like. In various examples, an alkyl group is unsubstituted or substituted with one or more substituent(s). In various examples, a substituent is a charged substituent (such as, for example, a static charged substituent or a condition (e.g., pH) specific charged substituent). Examples of substituents include, but are not limited to, various substituents such as, for example, halogen groups (-F, -Cl, -Br, and -I), aliphatic groups (e.g., alkyl groups, alkenyl groups, alkynyl groups, and the like), halogenated aliphatic groups (e.g., trifluoromethyl group and the like), aryl groups, halogenated aryl groups, hydroxyl group, amine groups, nitro group, cyano groups, isocyano groups, azide group, silane groups (e.g., alkyl silane groups, aryl silane groups, alkyl / aryl silane groups, or the like), alkoxide groups, alcohol groups, ether groups, ketone groups, carboxylate groups, carboxylic acid groups, ester groups, amide groups, thioether groups, thioester groups, and the like, and any combination thereof.

[0055] As used herein, unless otherwise indicated, the term “aryl” refers to Cs to C30 fully aromatic or partially aromatic carbocyclic groups (or compounds comprising an aryl group, e.g., an aryl compound). In various examples, an aryl group is a Cs to C12 aromatic or partially aromatic carbocyclic group (e.g., Cs, Ce, C7, Cs, C9, C10, C11, or C12), including all integer numbers of carbons and ranges of numbers of carbons therebetween. In various examples, an aryl group comprises (or is) one or more polyaryl group(s) (such as, for example, fused ring group(s), biaryl group(s), or the like, or any combination thereof) or the like, or any combination thereof. In various examples, an aryl group is unsubstituted or substituted with one or more substituent(s). In various examples, a substituent is a charged substituent (such as, for example, a static charged substituent or a condition (e.g., pH) specific charged substituent). Examples of substituents include, but are not limited to, substituents such as, for example, halogen groups (-F, -Cl, -Br, and -I), aliphatic groups (e.g., alkyl groups, alkenyl groups, alkynyl groups, and the like), halogenated aliphatic groups (e.g., trifluorom ethyl group and the like), aryl groups, halogenated aryl groups, hydroxyl group, amine groups, nitro group, cyano groups, isocyano groups, azide group, silane groups (e.g., alkyl silane groups, aryl silane groups, alkyl / aryl silane groups, or the like), alkoxide groups, alcohol groups, ether groups, ketone groups, carboxylate groups, carboxylic acid groups, ester groups, amide groups, thioether groups, thioester groups, and the like, and any combination thereof. In various examples, an aryl groups comprises one or more heteroatom(s) (such as, for example, oxygen(s), nitrogen(s) (e.g., pyridinyl groups and the like), sulfur(s), and the like, and any combination thereof), which may be referred to as heteroaryl groups. Examples of aryl groups include, but are not limited to, phenyl groups,biaryl groups (e.g., biphenyl groups and the like), fused ring groups (e.g., naphthyl groups and the like), hydroxybenzyl groups, tolyl groups, xylyl groups, furanyl groups, pyrrolyl groups, thiophenyl groups, benzofuranyl groups, indolyl groups, imidazolyl groups, benzimidazolyl groups, pyridinyl groups, and the like.

[0056] The present disclosure provides, inter alia, graphene oxide membranes. The present disclosure also provides methods of making and uses of graphene oxide membranes.

[0057] In an aspect, the present disclosure provides graphene oxide membranes. In various examples, a graphene oxide membrane or membranes are referred to herein as a “stitched” graphene oxide membrane or membranes. In various examples, a graphene oxide membrane comprises a plurality of “stitched” graphene oxide flakes (e.g., graphene oxide flakes laterally and / or vertically “stitched”). In various examples, a graphene oxide membrane is made by a method of the present disclosure. Non-limiting examples of graphene oxide membrane layers are disclosed herein.

[0058] In various examples, a graphene oxide membrane (e.g., a separation and / or enrichment substrate or the like) comprises a substrate (which may be a porous substrate); and a layer (a graphene oxide layer) comprising a plurality of graphene oxide flakes (e.g., where the longest linear dimension of the graphene oxides flakes are substantially parallel or parallel), where at least a portion of, substantially all, or all the graphene oxide flakes are disposed on at least a portion or all of the exterior surface(s) of the substrate (e.g., a layer comprising a plurality of first graphene oxide flakes disposed on an exterior surface or surfaces of the substrate and a plurality of second graphene oxide flakes disposed on at least a portion, substantially all, or all of the first graphene oxide flakes). In various examples, the only fluidic connection between opposite sides of a layer is formed by in-plane defect(s) and / or pore(s) of the graphene oxide flakes and / or the graphene oxide membrane comprises a plurality of material domains comprising a material (e.g., an impermeable material, such as, impermeable to hydrocarbons (e.g., a hydrocarbon or hydrocarbons comprising 5, 6, 7, 8, 9, or 10 carbons), hydrocarbon solvents, and the like), alcohols, or the like, or any combination thereof) and each of the material domains is disposed on (or chemically bonded, such as, for example, by a plurality of covalent bonds to) a surface or surfaces (e.g., an exterior edge or edges, an in-plane pore edge or in-plane pore edges (e.g., where the in-plane pore is sealed), or an in-plane defect (e.g. defect edge or the like) or in-plane defect edges (e.g. defect edge or the like) (e.g., where the defect is sealed), or the like, or any combination thereof) of one or more graphene oxide flake(s) (e.g., at least a portion of the domains (e.g., the individual domains) crosslink two or more of the graphene oxide flakes (e.g., vertically adjacentgraphene oxide flakes, two or more coplanar graphene oxide flakes) and / or seal at least a portion of, substantially all, or all the pores or in plane defects of the graphene oxide flakes).

[0059] In various examples, a layer (a graphene oxide layer) has (or comprises) a lamellar structure (such as, for example, an ordered lamellar structure or the like). In various examples, a layer (a graphene oxide layer) has (or comprises) a lamellate comprising a plurality of graphene oxide flakes.

[0060] A layer (a graphene oxide layer) can have various thicknesses. In various examples, a layer (a graphene oxide layer) comprises at least one linear dimension (which may be a cross-sectional dimension or a linear dimension substantially perpendicular (or perpendicular) to a longest linear dimension of a layer, or a thickness, or the like) of about 3 nanometers (nm) to about 100 nm, including all 0.1 nm values and ranges therebetween.

[0061] A layer (a graphene oxide layer) may further comprise one or more non-lamellar graphene oxide layer(s). In various examples, a non-lamellar graphene oxide layer comprises a randomly packed structure (e.g., randomly packed graphene oxide flakes). In various examples, a layer further comprises a non-lamellar graphene oxide layer disposed between a graphene oxide membrane comprising material domains (or a layer (a graphene oxide layer)) and a substrate.

[0062] A layer (a graphene oxide layer) may comprise a plurality of individual layers. In various examples, one or more or all of the individual layers of a plurality of layers is distinct (e.g., structurally and / or compositionally distinct) from one or more or all of the other layers of the plurality of layers. In various examples, a layer (a graphene oxide layer) comprises a plurality of layers (graphene oxide layers), each layer (a graphene oxide layer) independently comprising a plurality of the graphene oxide flakes where a longest linear dimension of the graphene oxides flakes are substantially parallel or parallel). In various examples, the edges of the graphene oxide flakes are substantially sealed or sealed by a material.

[0063] Graphene oxide flakes can have various structures. In various examples, the graphene oxide flakes of a layer or layers (a graphene oxide layer or layers) are, independently, single-layer graphene flakes, multilayer graphene flakes, or the like, or any combination thereof. In various examples, at least a portion of, substantially all, or all the graphene oxide layer(s) independently comprise an interlayer distance (e.g., a wet interlayer distance) (e.g., d-spacing) of about 5 to about 10 A, including all 0.1 A values and ranges therebetween. In various examples, substantially all or all the graphene oxide layers comprise substantially the same (e.g., + / - 0.1 A, + / - 0.2 A, + / - 0.25 A, + / - 0.5 A, + / - 0.75, + / - 1 A, + / - 1.5 A, or + / - 2 A, or the like).

[0064] In various examples, at least a portion of, substantially all, or all the graphene oxide flakes each comprise one or more in-plane defects and / or pores. In various examples, each in-plane defect of at least a portion of, substantially all, or all the graphene oxide flakes comprises a size (e.g., a dimension of plane defining the pore aperture, the in-plane defect, or the like) of about 4 Angstroms (A) to about 7 A, including all 0.1 A values and ranges therebetween, forming one or more (e.g., a plurality of) continuous channel(s) (e.g., nanochannel (s) or the like) fluidically connecting opposite sides of a layer (a graphene oxide layer). In various examples, substantially all or all the graphene oxide flakes each comprise one or more in-plane defects and / or pores having substantially the same size (e.g., + / - 0.05 A, + / - 0.1 A, + / - 0.15 A, or + / - 0.2 A, + / - 0.25, + / - 0.5 A, + / - 0.75, + / - 0.9, + / - 0.95, or + / - 1 A, or the like).

[0065] A graphene oxide membrane can comprise various types of porosity. In various examples, the pores of a graphene oxide membrane layer are interconnected (e.g., highly interconnected or the like) or the like and / or the substrate comprises a desirable pore density.

[0066] In various examples, the only fluidic connection between opposite sides of a layer (a graphene oxide layer) is formed by in-plane defect(s) and / or pore(s). In various examples, the in-plane defect(s) and / or pore(s) independently or on averages comprise a size (e.g., a dimension of plane defining the pore aperture, the in-plane defect, or the like) of about 4 Angstroms (A) to about 7 A, including all 0.1 A values and ranges therebetween, and / or forming one or more (e.g., a plurality of) continuous channel(s) (e.g., nanochannel(s) or the like).

[0067] A graphene oxide membrane may comprise one or more (e.g., a plurality) of material domains. In various examples, a material domain comprises one or more material(s). In various examples, a material is an impermeable material (such as, for example, a material impermeable to one or more small molecules (e.g., one or more hydrocarbon(s), one or more alcohol(s), or the like, or any combination thereof)). In various examples, a material preferentially seals substantially all or all of the lateral gaps between and / or pores having a size greater than about 7 A of the graphene oxide flakes of a layer. In various examples, at least a portion of, substantially all, or all of the in-plane pores and / or in-plane defects of the graphene oxide flakes in a layer are not substantially sealed or sealed by one or more material domain(s).

[0068] In various examples, a material is a hydrophobic material, an inert material (e.g., thermally inert, hydrocarbon inert, or the like, or any combination thereof), or the like, or any combination thereof. In various examples, a material is a metal oxide material (or acombination of metal oxide materials), a hybrid material (such as, for example, a carbon- containing metal oxide material (or a combination of carbon-containing metal oxide materials), or the like, or the like, or any combination thereof.

[0069] A metal of a metal oxide material or carbon-containing metal oxide material can be any metal that can form a volatile precursor suitable for use in a molecular layer deposition process. In various examples, a metal oxide material or carbon-containing (such as, for example, carbon doped or the like) metal oxide material comprises one or more metal(s). Non-limiting examples of metals include titanium, zirconium, tungsten, tin, zinc, aluminum, or the like, or any combination thereof. In various examples, a material is a titanicone material, a zirconicone material, or the like, or any combination thereof.

[0070] In various examples, a carbon-containing (e.g., carbon-doped) metal oxide layer is (or comprises) a carbon-containing (e.g., carbon-doped) titanium oxide, a carbon-containing (e.g., carbon-doped) zirconium oxide (e.g., a carbon-doped zirconium dioxide or the like), a carbon-containing (e.g., carbon-doped) tungsten oxide, a carbon-containing (e.g., carbon- doped) zinc oxide, a carbon-containing (e.g., carbon-doped) tin oxide, or the like, or any combination thereof.

[0071] A graphene oxide membrane can comprise various substrates. A substrate can have various forms, compositions, etc.

[0072] In various examples, a substrate is a porous substrate or non-porous substrate. In various examples, a substrate is planar (e.g., a planar substrate), non-planar (e.g., a non- planar substrate), a fiber (which may be a hollow fiber or the like), or a plurality of fibers, or the like. In various examples, a fiber is a hollow fiber comprising a hollow wall (or at least a portion of a wall is hollow), and the hollow wall or the hollow portion of a wall comprises a plurality of pores (such as, for example a plurality of pores comprising at least one linear dimension (which may be a cross-sectional dimension, such as, for example, a diameter, or the like) (which may be average pore dimension(s) of from about 1 nm to about 100 nm, including all 0.1 nm values and ranges therebetween (e.g., about 5 nm to about 50 nm, about 5 nm, about 10 nm, about 10 nm, or about 50 nm). In various examples, a substrate is aluminum oxide (AAO) (such as, for example, flat AAO (e.g., anodic flat AAO or the like)), cylindrical a-alumina hollow fiber (HF) or a plurality thereof, or the like.

[0073] In various examples, a substrate comprises is (or comprises) one or metal(s), one or more organic material(s) (such as, for example, polymer material(s) or the like), one or more inorganic material(s), or any combination thereof. In various examples, a substrate is (or comprises) one or more polymer material(s), one or more ceramic material(s), or the like,or any combination thereof. In various examples, a substrate is (or comprises) one or more metal(s) and / or ceramic metal(s). Non-limiting examples of metals include stainless steel, titanium, zirconium, tin, tungsten, or the like, or any combination thereof. Non-limiting examples of ceramic materials include aluminum oxide, titanium oxide, zirconium oxide, tin oxide, tungsten oxide, or the like, or any combination thereof. In various examples, the efficacy of a graphene oxide membrane is independent of the morphology of the substrate (e.g., hollow fiber, planer flat sheet, or the like). In various examples, a substrate is a hollow fiber and a layer (graphene oxide layer) is disposed on at least a portion of or all of the exterior surfaces of the fiber.

[0074] A substrate may be porous. In various examples, at least a portion of, substantially all, or all the one or metal(s), the one or more organic material(s), the one or more inorganic material(s), or the like, or the combination thereof is porous. In various examples, at least a portion of, substantially all, or all the organic material(s) is / are porous. In various examples, at least a portion of, substantially all, or all the ceramic material(s) is / are porous.

[0075] A graphene oxide membrane can have various sizes (areas, thicknesses, or the like, or any combination thereof). The area of a graphene oxide membrane is not particularly limited. Processing methods / equipment that can be used to fabricate graphene oxide membranes of a wide range of areas and thicknesses are known in the art. In various examples, the area of a graphene oxide membrane is an area typically used in membrane separation and / or enrichment process (such as, for example, an ORSO process or the like) or the like.

[0076] A graphene oxide membrane can have various forms. In various examples, a graphene oxide membrane is a membrane, a film (e.g., a thin film), a sheet, a coating, a skin layer, or the like.

[0077] In various examples, a graphene oxide membrane is configured for substantially all or all pathway -2 molecular permeation. In various examples, a graphene oxide membrane is configured to not permit substantial or any pathway- 1 molecular permeation.

[0078] In various examples, a graphene oxide membrane exhibits one or more desirable propert(ies). In various examples, a graphene oxide membrane exhibits desirable permeance and / or one selectivity (e.g., hydrocarbon selectivity or the like) (e.g., size selectivity), which may be size-selective permeance). In various examples, a graphene oxide membrane exhibits a hydrocarbon size selectivity of less than 1 A.

[0079] In various examples, a graphene oxide membrane is suitable for and / or configured for small molecule separation (such as, for example, a small molecule separation method ofthe present disclosure. In various examples, a separation and / or enrichment substrate comprises one or more graphene oxide membrane(s). In various examples, a separation and / or enrichment substrate is an organic solvent reverse osmosis (ORSO) membrane (such as, for example, a membrane based organic solvent reverse osmosis membrane or the like), a reverse osmosis desalination membrane, a gas separation membrane, or the like.

[0080] In an aspect, the present disclosure provides methods of making graphene oxide membranes. In various examples, a method produces one or more graphene oxide membrane(s) of the present disclosure. Non-limiting examples of methods of making graphene oxide membranes are disclosed herein.

[0081] In various examples, a method of making one or more graphene oxide membrane(s) comprises forming a layer comprising a plurality of graphene oxide flakes on at least a portion of, substantially all, or all of the exterior surfaces of a substrate (which may be a porous substrate) (e.g., using an aqueous dispersion of graphene oxide flakes or the like); optionally, drying the layer; and contacting the layer (e.g., the dried layer) with one or more vapor-phase precursor(s) (e.g., using a molecular layer deposition) and, optionally, one or more vapor-phase carbon precursor(s), such that a plurality of material domains are formed (e.g., on a surface or surfaces of at least a portion of, substantially all, or all of the graphene oxide flakes). In various examples, a method (e.g., one or more or all of the steps of a method) is repeated a desired number of times (e.g., to form a multilayer structure).

[0082] In various examples, a method comprises selective deposition of an impermeable material at the edges of the surface 2D flakes. In various examples, selective deposition of an impermeable material at the edges of the surface 2D flakes results in graphene oxide flakes integrated or “stitched” into, for example, a continuous nanofilm or the like, eliminating transport through lateral gaps between edges, forcing molecular transport only through inplane pores.

[0083] In various examples, graphene oxide flakes are, independently, single-layer graphene oxide flakes, multilayer graphene oxide flakes, or the like. In various examples, a combination of two or more different (e.g., structurally and / or compositionally different) graphene oxide flakes is used. In various examples, the graphene oxide flakes comprise a plurality of oxygen-containing groups (such as, for example, hydroxyl groups, carboxylate groups, ketone groups, or the like, or any combination thereof). In various examples, a least a portion, substantially all, or all the graphene oxide flakes comprise a plurality of oxygencontaining groups disposed on the edges and / or edges of the in-plane pores and / or in-plane defects of the graphene oxide flakes.

[0084] In various examples, graphene oxide flakes are present in an aqueous solvent (e.g., water or the like) (such as, for example, an aqueous dispersion of graphene oxide flakes or the like). Without intending to be bound by any particular theory, it is considered that the thickness of a graphene oxide layer can be selected by choosing an appropriate concentration of the graphene oxide flakes.

[0085] A method can use various vapor-phase carbon precursor(s). Combinations of vapor-phase carbon precursors can be used. Without intending to be bound by any particular theory, it is considered a vapor-phase carbon precursor or vapor-phase carbon precursors react(s) to form at least a portion of or all the carbon in a carbon-containing material. In various examples, a vapor-phase carbon precursor is a carbon source or the like. In various examples, a vapor-phase carbon precursor comprises one or more (e.g., 2, 3, or 4) hydroxyl groups. In various examples, at least a portion of or all the vapor-phase carbon precursor(s) is / are chosen from polyols, alcohols, and the like, and any combination thereof. In various examples, the alcohol(s) are C2, C3, or C4 alcohols or the like. In various examples, the polyol(s) are C2, C3, or C4 polyols or the like. In various examples, the polyol(s) are glycols (e.g., C2, C3, or C4 glycols) or the like. In various examples, vapor-phase carbon precursor(s) exhibit(s) desirable vapor pressure. In various examples, contacting a layer with one or more vapor-phase precursor(s) is carried out in (or as part of) one or more vapor-phase molecular layer deposition (MLD) process(es) (e.g., 1 to 40, including all integer values and ranges therebetween, independent MLD processes) or the like.

[0086] A method can use various metal oxide precursor(s). Without intending to be bound by any particular theory, it is considered a vapor-phase metal oxide precursor reacts to form at least a portion of or all the metal oxide in a carbon-containing material. In various examples, a vapor-phase metal oxide precursor comprises one or more metal(s) (such as, for example, transition metal(s) or the like). In various examples, a vapor-phase metal oxide precursor / precursors is / are a metal halide or the like, or a combination thereof. In various examples, vapor-phase metal oxide precursor(s) is / are chosen from metal halides (e.g., metal fluorides, metal chlorides, metal bromides, or metal iodides) or the like. In various examples, the metal halide(s) are chosen from titanium halides, zirconium halides, zinc halides, tungsten halides, tin halides, aluminum halides, or the like, or any combination thereof. In various examples, a vapor-phase metal oxide precursor is (or all vapor-phase metal oxide precursors are) stable at a temperature and / or pressure at which the precursor(s) exhibit(s) desirable vapor pressure.

[0087] The methods comprise various reactions and processes. A reaction or process can be performed under various reaction conditions (e.g., time, temperature, pressure, or the like, or any combination thereof).

[0088] A reaction can be carried out for various times. The reaction time can depend on factors such as, for example, temperature, atmosphere, pressure, presence and / or reactivity of the carbon source(s), if present, and vapor-phase metal oxide precursor(s), presence and / or intensity of an applied energy source, mixing (e.g., stirring, grinding, or the like), or the like, any a combination thereof. Determination of an appropriate reaction time is within the purview of one of ordinary skill in the art.

[0089] In an aspect, the present disclosure provides systems. In various examples, a system comprises one or more graphene oxide membrane(s) of the present disclosure and / or one or more graphene oxide membrane(s) made by a method of present disclosure. Nonlimiting examples of systems are disclosed herein.

[0090] In various examples, a system is a separation system, filtration system, or the like. In various examples, a separation system is an organic solvent reverse osmosis system, a membrane based organic solvent reverse osmosis (ORSO) system or the like), a reverse osmosis desalination system, a gas separation system, or the like comprising one or more graphene oxide membrane(s) of the present disclosure and / or one or more graphene oxide membrane(s) made by a method of present disclosure.

[0091] In various examples, one or more graphene membrane(s) is / are disposed in a housing, the housing comprising one or more orafic(es). In various examples, a system further comprises one or more additional components typically used in a separation system (such as, for example, pump(s), mass / flow controller(s), reservoir(s), tank(s), pressure gauges, or the like, or any combination thereof, which may or may not be in fluid contact with one or more of the graphene oxide membrane(s). In various examples, the graphene oxide membrane(s) is / are disposed in a housing, the housing comprising one or more orafic(es), which may be in fluid contact with one or more additional component(s). In various examples, a system comprises one or more or all the features of a system described herein. In various examples, a system is configured for normal flow, tangential flow filtration, or the like, or any combination thereof.

[0092] In various examples, a system comprises a module as shown in FIGS. 35 A and 35B. In various examples, this system is operated as a stand-alone equipment. In various examples, an industrial process comprises use of one or more of the modules.

[0093] In an aspect, the present disclosure provides uses of graphene oxide membranes of the present disclosure and / or graphene oxide membranes made by a method of present disclosure. Non-limiting examples of uses of graphene oxide membrane(s) layers are disclosed herein.

[0094] In various examples, a graphene oxide membrane or graphene oxide membranes (or a system comprising graphene oxide membrane(s)) is / are used in a separation and / or enrichment process. In various examples, a separation process is an organic solvent reverse osmosis (OSRO) process / application (such as, for example, a membrane based organic solvent reverse osmosis (ORSO) process / application, a reverse osmosis desalination process / application, a gas separation process / application, or the like.

[0095] In various examples, a method separates one or more small molecule(s) and / or enriches one or more small molecule(s). In various examples, a method separates one or more small molecule(s) from and / or enriches one or more small molecule(s) of a composition comprising two or more small molecules (e.g., different and / or distinct small molecules). In various examples, the method is (or comprises) an organic solvent reverse osmosis (ORSO) method (such as, for example, a membrane based organic solvent reverse osmosis (ORSO) method or the like), a reverse osmosis desalination method, or a gas separation method or the like.

[0096] A separation and / or enrichment process may be carried out under an applied pressure. In various examples, a contacting is carried out under applied pressure. In various examples, a separation and / or enrichment is carried out with no observable phase change (e.g., of small molecule(s), such as, hydrocarbon(s) or the like) or the like. A separation and / or enrichment process can be carried out at various temperatures and / or pressures.

[0097] In various examples, a method of separating one or more small molecule(s) from and / or enriching one or more small molecule(s) of a composition comprising two or more small molecules (e.g., different and / or distinct small molecules) (such as, for example, hydrocarbons (e.g., independently, C4, Cs, Ce, C7, Cs, C9, or C10 hydrocarbons, which may be linear or branched or comprise an aryl group, an alkyl group, an aliphatic group, or the like, or any combination thereof, alcohols (e.g., independently, Ci, C2, C3, C4, Cs, Ce, C7, Cs, C9, or C10 hydrocarbons, which may be linear or branched or comprise an aryl group, an alkyl group, an aliphatic group, or the like, or any combination thereof, or the like or any combination thereof) (e.g., a mixture of two or more small molecules, such as, for example, hydrocarbons, alcohols, or the like, or any combination thereof) comprises contacting the composition (e.g., the mixture or the like) with one or more graphene oxide membrane(s) ofthe present disclosure and / or one or more graphene oxide membrane(s) made by a method of present disclosure, where one or more of the small molecule(s) (such as, for example, the hydrocarbon(s)) is / are separated from the composition and / or enriched in the composition.

[0098] A method can be used to separate or enrich various small molecules. In various examples, a small molecule is a hydrocarbon, an alcohol, or the like. In various examples, a hydrocarbon is an alkane (which may be linear or branched) (e.g., comprising an alkyl group), an aliphatic compound (such as, for example, an alkene, an alkyne, or the like) (which may be linear or branched) (e.g., comprising an aliphatic group), an aryl compound (e.g., comprising an aryl group, such as, for example, xylenes and isomers thereof and the like). In various examples, a small molecule or the small molecules is / are independently a C4, C5, Ce, C7, Cs, C9, or C10 hydrocarbon, which may be linear or branched and / or comprise an aryl group, an alkyl group, an aliphatic group, or the like, or any combination thereof), Ci, C2, C3, C4, Cs, Ce, C7, Cs, C9, or C10 alcohol, which may be linear or branched and / or comprise an aryl group, an alkyl group, an aliphatic group, or the like, or any combination thereof), or the like or any combination thereof. In various examples, a method separates or enriches one or more small molecule(s) in or of a composition comprising one or more small molecule(s) (at least a portion or all which may be one or more isomer(s) of one or more of the small molecule(s)). In various examples, a composition comprises two or more different (e.g., structurally different or the like) small molecule(s).

[0099] In various examples, a method provides (e.g., after one or more contating(s)) one or more small molecule(s) (such as, for example, hydrocarbon(s) or the like) at a purity of 98.5% or greater, 99% or greater, 99.5% or greater, 99.9% or greater (based on the total amount of small molecule(s) (e.g., hydrocarbon(s) or the like) present), for example, where the composition (e.g., mixture or the like) comprises the one or more small molecule(s) at a lower (e.g., substantially lower) concentration prior to a contacting or contactings. In various examples, a composition prior to use in a method (e.g., prior to any contating) comprises 1% by weight or more, 5% by weight or more, or 10% by weight for each of one or more small molecule(s) (such as, for example, hydrocarbon(s) or the like).

[0100] A method can be used to separate or enrich various small molecules in or from various compositions. In various examples, a composition is a petroleum distillation product (e.g., a petroleum distillation fraction), a gas composition, seawater, or the like.

[0101] In various examples, there is no substantial or any or any observable pathway- 1 molecular permeation during the separation and / or enrichment and / or there is substantially or only pathway -2 molecular permeation. In various examples, there is no observable pathway- 1molecular permeation during the separation and / or enrichment and / or only pathway-2 molecular permeation is observed.

[0102] One or more or all the graphene oxide membrane(s) may be reused in a method. In various examples, a graphene oxide membrane or membranes is / are reused in a subsequent separation and / or enrichment (such as, for example, a second separation and / or enrichment, a third separation and / or enrichment, etc.). In various examples, the graphene oxide membranes(s) are cleaned prior to use in each of the subsequent separation(s) and / or enrichment(s).

[0103] The following Statements describe various examples of graphene oxide membranes, methods of making graphene oxide membranes, and uses thereof of the present disclosure and are not intended to be in any way limiting:Statement 1. A graphene oxide membrane (e.g., a separation and / or enrichment substrate or the like) comprising a substrate (which may be a porous substrate); and a layer comprising a plurality of graphene oxide flakes (e.g., where the longest linear dimension of the graphene oxides flakes are substantially parallel or parallel), where at least a portion of, substantially all, or all the graphene oxide flakes are disposed on at least a portion or all of the exterior surface(s) of the substrate (e.g., a layer comprising a plurality of first graphene oxide flakes disposed on an exterior surface or surfaces of the substrate and plurality of second graphene oxide flakes disposed on at least a portion of, substantially all, or all of the first graphene oxide flakes), where i) the only fluidic connection between opposite sides of the layer is formed by in-plane defect(s) and / or pore(s) of the graphene oxide flakes and / or ii) the graphene oxide membrane comprises a plurality of material domains comprising a material (e.g., an impermeable material, such as, impermeable to hydrocarbon(s) (e.g., a hydrocarbon comprising 5, 6, 7, 8, 9, or 10 carbons) or hydrocarbon solvent, or alcohol(s), or the like) and each of the material domains is disposed on (or chemically bonded, such as, for example, by a plurality of covalent bonds to) a surface (e.g., an exterior edge or edges, an in-plane pore edge or in-plane pore edges (e.g., where the in-plane pore is sealed), or an in-plane defect (e.g. defect edge or the like) or in-plane defect edges (e.g. defect edge or the like) (e.g., where the defect is sealed), or the like, or any combination thereof) of one or more graphene oxide flake(s) (e.g., at least a portion of the domains (e.g., the individual domains) crosslink two or more of the graphene oxide flakes (e.g., vertically adjacent graphene oxide flakes, two or more coplanar graphene oxide flakes) and / or seal at least a portion of, substantially all, or all the pores or in plane defects of the graphene oxide flakes).Statement 2. A graphene oxide membrane according to Statement 1, where at least a portion of, substantially all, or all the graphene oxide flakes each comprise one or more in-plane defects and / or pores, each in-plane defect or pore comprising a size (e.g., a dimension of plane defining the pore aperture, the in-plane defect, or the like) of about 4 Angstroms (A) to about 7 A, including all 0.1 A values and ranges therebetween, forming one or more (e.g., a plurality of) continuous channel(s) (e.g., nanochannel (s) or the like) fluidically connecting opposite sides of the layer.Statement 3. A graphene oxide membrane according to Statement 1 or 2, where the substrate is planar, a fiber (which may be a hollow fiber or the like), or the like.Statement 4. A graphene oxide membrane according to any one of the preceding Statements, where the substrate comprises is (or comprises) one or metal(s), one or more organic material(s) (such as, for example, polymer material(s) or the like), one or more inorganic material(s), or the like, or any combination thereof.Statement 5. A graphene oxide membrane according to any of the preceding Statements, where the substrate is (or comprises) a metal chosen from stainless steel, titanium, zirconium, tin, tungsten, or the like, or any combination thereof.Statement 6. A graphene oxide membrane according to any of the preceding Statements, where the substrate is (or comprises) a ceramic material chosen from aluminum oxide, titanium oxide, zirconium oxide, tin oxide, tungsten oxide or the like, or any combination thereof.Statement 7. A graphene oxide membrane according to any of the preceding Statements, where the layer has (or comprises) at least one linear dimension (which may be a cross- sectional dimension or a dimension linear dimension substantially perpendicular (or perpendicular) to a longest linear dimension of the layer, a thickness, or the like) of about 3 nanometers (nm) to about 100 nm, including all 0.1 nm values and ranges therebetween (e.g., about 3 nm to about 50 nm, about 5 nm to about 50 nm, about 10 nm to about 50 nm, about 20 nm to about 50 nm, about 30 nm to about 50 nm, about 35 nm to about 50 nm, about 3 nm to about 60 nm, about 5 nm to about 60 nm, about 10 nm to about 60 nm, about 20 nm to about 60 nm, about 30 nm to about 60 nm, or about 35 to about 60 nm).Statement 8. A graphene oxide membrane according to any one of the preceding Statements, further comprising a non-lamellar graphene oxide layer disposed between the graphene oxide membrane comprising the material domains (or a layer (a graphene oxide layer)) and the substrate.Statement 9. A graphene oxide membrane according to any of the preceding Statements, where the graphene oxide membrane exhibits a permeance of 10'6mol • m'2• s'1• Pa'1or greater (e.g., a permeance of 1 x 10'6to 1 x 10'8mol • m'2• s'1• Pa'1, including all 1 x 10'8mol • m'2• s'1• Pa'1values and ranges therebetween.

[0104] Statement 10. A method of making a graphene oxide membrane of the present disclosure (e.g., a graphene oxide membrane of any one of Statements 1 to 9), the method comprising forming a layer comprising a plurality of graphene oxide flakes on at least a portion of, substantially all, or all of the exterior surfaces of a substrate (which may be a porous substrate); optionally, drying the layer; and contacting the layer with one or more vapor-phase precursor(s) and, optionally, one or more vapor-phase carbon precursor(s), such that a plurality of material domains are formed.Statement 11. A method according to Statement 10, where the vapor-phase carbon source(s) is / are chosen from polyols, and the like, and any combination thereof.Statement 12. A method according to Statement 10 or 11, where the vapor-phase metal oxide precursor(s) is / are independently chosen from metal halides (e.g., metal fluorides, metal chlorides, metal bromides, or metal iodides) and the like.Statement 13. A system comprising one or more graphene oxide membrane(s) of the present disclosure (such as, for example, a graphene oxide membrane / graphene oxide membranes of any of Statements 1-9 and / or a graphene oxide membrane / graphene oxide membranes made by a method of present disclosure, such as, for example, a method of any of Statements 10- 12).Statement 14. A system according to Statement 13, where the graphene oxide membrane(s) is / are disposed in a housing, the housing comprising one or more orafic(es).Statement 15. A method of separating one or more small molecule(s) (such as, for example, hydrocarbon(s) (e.g., C4, C5, Ce, C7, Cs, C9, or C10 hydrocarbon(s), which may be linear or branched or comprise an aryl group, an alkyl group, an aliphatic group, or the like, or any combination thereof) from and / or enriching one or more small molecules (such as, for example, hydrocarbon(s) (e.g., C4, C5, Ce, C7, Cs, C9, or C10 hydrocarbon(s), which may be linear or branched or comprise an aryl group, an alkyl group, an aliphatic group, or the like, or any combination thereof) a composition comprising two or more small molecules (such as, for example, hydrocarbons (e.g., independently, C4, C5, Ce, C7, Cs, C9, or C10 hydrocarbons, which may be linear or branched or comprise an aryl group, an alkyl group, an aliphatic group, or the like, or any combination thereof) (e.g., a mixture of two or more small molecules, such as, for example, hydrocarbons), the method comprising contacting thecomposition (e.g., the mixture or the like) with one or more graphene oxide membrane(s) of the present disclosure (such as, for example, a graphene oxide membrane / graphene oxide membranes substrate / substrates of any of Statements 1-8 and / or a graphene oxide membrane / graphene oxide membranes made by a method of present disclosure, such as, for example, a method of any of Statements 9-11, and / or a system of the present disclosure, such as, for example, a system of Statement 12 or 13), where one or more of the small molecule(s) (such as, for example, the hydrocarbon(s)) is / are separated from the composition and / or enriched in the composition.Statement 16. A method according to Statement 15, where the method is an organic solvent reverse osmosis (ORSO) method (such as, for example, a membrane based organic solvent reverse osmosis (ORSO) method or the like), a reverse osmosis desalination method, a gas separation method, or the like.Statement 17. A method according to Statement 15 or 16, where the composition is a petroleum distillation product (e.g., a petroleum distillation fraction), a gas composition, seawater, or the like.Statement 18. A method according to any one of Statements 15-17, where the graphene oxide membrane(s) is / are reused in a subsequent separation and / or enrichment (such as, for example, a second separation and / or enrichment, a third separation and / or enrichment, etc.). Statement 19. A method according to Statement 18, where the graphene oxide membranes(s) are cleaned prior to use in each of the subsequent separation(s) and / or enrichment(s).

[0105] The steps of the methods described in the various embodiments and examples disclosed herein are sufficient carry out the methods of the present disclosure. Thus, in an embodiment or example, a method consists essentially of a combination of the steps of the methods disclosed herein. In another embodiment or example, a method consists of such steps.

[0106] The following Example is presented to illustrate the present disclosure. It is not intended to be limiting in any manner.EXAMPLE

[0107] The following is an example of graphene oxide membranes of the present disclosure and methods of making and uses of same.

[0108] This example provides a description of stitched two-dimensional (2D) material flakes as a continuous membrane for size-selective hydrocarbon separation. Utilizing the distribution of functional groups on single-layered graphene oxide (GO) provided molecularlayer deposition to “stitch” flakes laterally to eliminate leakage from edges, “lock” flakes vertically to prevent swelling, and fine-tune the flake defects to allow size-based permeation. These “stitched” GO membranes exhibit sized-based separation for small hydrocarbons and 1-2 orders of magnitude higher permeance than reported membranes with similar separation factors.

[0109] Described is an effective approach for fabricating stable continuous nanofilms comprised of stacked GO flakes by “stitching” together the surface flakes, “locking” GO flakes vertically, and modifying structural defects of GO via preferential vapor-phase alkoxide deposition utilizing the distribution of functional groups on GO flakes. Effective size / shape selective permeation of small hydrocarbon molecules (4-7 A), for example, linear alkanes vs. their branched counterparts, through the “stitched” GO membranes, likely via the modified in-plane defects / pores, was obseved. Owing to the ultrathin, selective GO skin layer, ultrahigh solvent permeance was achieved, which is 1-2 orders of magnitude higher compared to the reported OSRO membranes. This allowed for the efficient extraction of linear alkanes from complex hydrocarbon mixtures, demonstrating potential for use of “stitched” GO membranes in petroleum and other industries.

[0110] Materials and Methods. Chemicals and other materials. Expanded graphite (EAG grade 1721), purchased from Asbury Carbon Inc. NJ, USA, was used to prepare graphene oxide (GO). Aqueous hydrogen peroxide solution (H2O2, 30 wt. %), concentrated sulfuric acid (H2SO4, 98 wt. %), potassium permanganate (KMnO4), and hydrochloric acid (HC1, 36 wt. %) were purchased from Fisher Scientific Inc. 50 nm pore size (outer surface), 1.5 mm outer diameter ceramic hollow fiber membrane, used as the support for membrane fabrication, was purchased from Media and Process Technology Inc. (PA, USA). Deionized (DI) water used for the experiments was obtained from a PURELAB Flex system (ELGA LabWater, Woodridge, IL, US). Titanium Chloride (TiCL, >99.995 %) and ethylene glycol (C2H6O2, 99.8 %) were purchased from Sigma-Aldrich Corp. (St. Louis, MO, US). Ethylene glycol was dehydrated using heated 5A zeolite pellets (purchased form Sigma-Aldrich Corp.) before it was loaded into the Molecular Layer Deposition (MLD) precursor tank. n-Hexane (99%) and n-Pentane (99+%) were purchased from Acros Organics. Benzene (for HPLC, 99.9%), 3 Methyl Pentane (> 99%), and 2, 3 Dimethyl Butane (98%) were purchased from Sigma Aldrich. Toluene (99.9%) was purchased from Fisher Scientific Co. Isooctane (2, 2, 4 Trimethylpentane, 99%) was purchased from Honeywell. n-Octane (98%) and n-Heptane (99+%) were purchased from Alfa Aesar. All fittings used to build the MLD system, and the permeation system were procured from Swagelok.

[0111] Graphene Oxide Synthesis. Graphene oxide was prepared by a modified Hummer’s method. A certain amount (10-15 g) of expandable graphite was taken in a large beaker and irradiated in a microwave (1,000 W (W = watt(s)) for a short period (30 s (s = second(s))). This expands the graphite to about 100 times of its original volume. This microwaved, expanded graphite was then mixed with 1 L of 98 wt.% sulfuric acid in a large beaker and kept under continuous stirring for 0.5 h (h = hour(s)) in an ice bath to maintain the temperature at 4°C. The temperature of the reaction mixture was constantly monitored using a mercury thermometer. To this mixture, 50 g of KMnCh was added slowly and the reaction was allowed to continue under constant stirring for 3 h more. After this, the reaction temperature was raised to 10°C by adding 2 L of DI water into the reaction mixture slowly, as the reaction beaker was left in the ice bath. After the temperature reached 10°C, to the reaction mixture 100 ml of H2O2 (30 wt. % (wt. % = weight percent) was added and stirred for 0.5 h more. After the reaction was complete, the product was centrifuged and washed several times with 5 wt. % HC1 solution. Then it was repeatedly washed with DI water to completely remove the acid and then centrifuged at 8,000 rpm until the pH of the solution was about 7. The resulting aqueous solution of the GO was ~ 1 wt.% in total of 2 kg GO suspension in DI water. The whole GO dispersion was dried in an air oven to get dry GO powder which was then re-dispersed (via bath sonication) in a known volume of DI water to prepare a GO dispersion with a known concentration.

[0112] Graphene Oxide Coating. Graphene oxide was coated on the outer surface of the 50 nm pore size hollow fiber membrane via vacuum-assisted coating by drawing a vacuum in the lumen side of the hollow fiber, as shown in FIGS. 4A-4F. The thickness of the GO coating was estimated from the BET surface area of the GO flakes in the following way:Membrane area = 2 x n x r x L (1) where, r is the outside diameter of the hollow fiber membrane (r = 1.5 mm) and L is the length of the membrane (usually, L = 5 cm). Assuming each GO layer thickness ~ 1 nm, for a GO coating thickness of ‘f nm, the total surface area to be coated was calculated asT otal Area = 2 x n X r x L X t (2)

[0113] This total area to be covered by GO sheets is then equated to the half of the BET surface area of GO (-700 m2g'1) because only one surface of the flake would be required to cover the total area calculated. Using this method, the concentration and volume of GO dispersion required to provide a GO coating of thickness ‘f on the porous hollow fiber support was computed. The surface area of GO is in agreement to many theoretical calculations.

[0114] The ceramic hollow fiber support was wetted with a few drops of NaOH solution and cleaned thoroughly with water before the coating process. A certain volume of aqueous GO solution of calculated concentration was filtered through the ceramic hollow fiber membrane fixed in the coating module which loaded the desired amount of GO on the surface of the ceramic hollow fiber support. The concentration of GO in the coating solution before and after the coating remained the same as measured from UV-Vis spectroscopy. This allows for estimating the coating thickness on the ceramic hollow fiber. Say concentration of GO is CGO (gm L'1) and the volume of coating solution filtered out is V (L), then the amount of GO loaded on the membrane surface was CGOXV (g). The coating module was then taken out from the aqueous GO solution and left to dry for 30 min (min = minute(s)) while the vacuum was still maintained in the lumen side of the hollow fiber membrane. The membrane was then kept in an oven (Yamato Scientific ADP-200C) at atmospheric pressure overnight for drying.

[0115] Molecular Layer Deposition on GO coatings. Molecular layer deposition is a vapor phase deposition technique that involves a self-limiting surface reaction carried out sequentially in a repeated manner. In this case, the MLD was carried out using Titanium Chloride (TiCL, >99.995 %, Sigma Aldrich) and ethylene glycol (C2H6O2, 99.8 %, Sigma Aldrich). The two ends of the GO membrane were sealed with Teflon tape to ensure that the MLD growth takes place only on the outer surface of the hollow fiber membrane having the GO coating and no growth is allowed in the lumen side of the hollow fiber. A tubular reactor was used for MLD. Before the deposition, the dried GO coated membranes were degassed at 60°C (under 5 mtorr), to remove adsorbed water from the substrate. Such a temperature is maintained to ensure that there is no loss of oxygen containing functional groups in GO at such high degree of vacuum. The MLD deposition is done at 60°C. Pneumatic valves controlled by a Lab VIEW (V2012, National Instrument) software were used to introduce each precursor discreetly at a time followed by excess reactor purge to maintain a repetitive cycle as described above. Each cycle starts with a 240 s vacuum after which TiCL was dosed in the chamber to achieve about 150 mtorr vapor pressure above the baseline pressure, followed by a 120 s time for the reactant to settle on the GO coated membranes. This is followed by a 270 s vacuum purge to remove excess TiCh. After this, a vacuum purge and a N2 purge is done to clean the reactor. This purge is done after every time one of the excess reactants is purged away. The second precursor (ethylene glycol) is introduced into the reactor and allowed to achieve a 50 mtorr vapor pressure above baseline pressure. This organic precursor was also allowed to settle on the substrate for 120 s. This follows a 270 s vacuum purge to remove excess ethylene glycol. This follows a N2 purge and a vacuum of240 s. The number of the cycle was set to control the growth of MLD. Membranes prepared were stored in an air oven at 60°C prior to testing.

[0116] Characterization. The surface and the cross-sectional morphology of the GO membranes were observed by Field Emission Scanning Electron Microscope (FEI Versa 3D Dual Beam). All samples were mounted on SEM holder using conducting carbon tape and were made to undergo 60 s of platinum spluttering. Samples for cross-section were crisply broken by applying force on two ends of the hollow fiber membrane.

[0117] The elemental composition and the behavior of the chemical bonds the atoms present makes were studied using Thermo Scientific™ Theta Probe Angle-Resolved X-ray Photoelectron Spectrometer. Samples were mounted on a brass plate using conducting carbon tape and dehydrated in vacuum overnight at 60°C. For the full scan, the scanning averaged over two times of scanning whereas for the detailed elemental scan the data averaged over 10 scans. Measurements were done under a vacuum of less than 5 * 10'8torr.

[0118] The ^ / -spacing of the GO membranes was investigated using a wide-angle X-ray diffraction spectrum measured using Bruker D8 - Discover X-ray Diffractometer. Dry membranes were dried overnight in a vacuum oven at 60°C before the testing. Wet membranes were submerged in mixture of solvent for 5-6 hours followed by 30 min of air drying them at room temperature. The d-spacing of the GO-based membrane were calculated using Bragg’s law as indicated below: nA = 2d sin 6 (3) where n is the number of diffraction (1, 2, 3 . . .), A is the wavelength of the X-ray (A = 0.154 nm, for Copper K-a), 0 is the incident angle and d is the spacing between diffraction planes.

[0119] The thermal stability of the membrane was determined by measuring the weight change of the membrane material with the increase in temperature using TA Instrument TGA - Q50. TGA was performed under an oxygen atmosphere with 90 SCCM flowrate of compressed air. The heating rate was 10°C min'1and the sample was held at isothermal for 10 min at 40°C before ramping up the temperature.

[0120] The ordering and the stacking of the GO deposition on the porous support were estimated using Raman Spectroscopy. Raman measurement of the GO coated membranes was collected using a Witec Alpha 300 confocal Raman microscope. The power used was 17 mW and the laser wavelength was 532.1 nm for all the measurements. A spot size of about 721 nm was produced by a 100X objective lens (721 nm = 1.22 x wavelength / numericalaperture of 0.9 for the 100X objective lens). The resolution of the Raman scattering data which is collected was 0.02 cm’1. Data were collected between 0 and 3500 cm’1.

[0121] To understand the chemical properties of the membrane, attenuated total reflectance - Fourier transform infrared spectroscopy was collected using Nicolet™ iS™ 5 FTIR Spectrometer. Spectrum was recorded between 400 and 4000 cm’1and was averaged over 16 scans.

[0122] The hydrophilicity and hydrophilicity of the GO and stitched GO membranes were investigated by measuring the receding water contact angle on the surface of the membrane. The measurements were done using Drop Shape Analyzer - DSA100, KRUSS GmbH. 3 pL of water was dropped on the surface of the membrane and the drop profile was captured and analyzed.

[0123] AFM was conducted in Park Fx40 system AFM. The probes used for the measurements were gold coated Multi 75E with a frequency of ~ 75 kHz. 2-3 pL of very dilute suspension of GO was dropped on a clean silicon wafer. The wafer was kept on a heat plate at 80°C to ensure the fast evaporation of water to prevent the agglomeration of GO flakes.

[0124] Organic Solvent Permeation. Solvent permeation was carried out in a Swagelok stainless steel (316L) permeation system. The hollow fiber membranes were fixed in a stainless steel module using JB Weld 8272 Marine weld epoxy. For single component permeation, a certain mole (n, moles = mass / molar mass) of liquid is collected (after steady state is reached) over a certain period of time to calculate the molar flux (J) under the given transmembrane pressure (Ap, Ap = PFeed— Ppermeate) provided in the dead-ended cell by pressurized N2. The transmembrane pressure was changed by controlling the pressure of the N2. The hydraulic permeance (P, in mol.m^.s'hPa'1) through the membrane is given by the following equation:where A is the active membrane area (given in m2), and t is the time period for sample collection (given in s), and Ap is the transmembrane pressure given in Pascal (Pa). For the single component permeation, ideal selectivity (a ideal (l / .) ) between any two solvent was calculated by taking the ratio of permeance (P£ j) of each of the component as follows: auideal(l■fj) pj

[0125] For mixture components permeation in cross flow set-up, a pressure higher than osmotic pressure of the mixture was maintained by a ReaXus LS single headed, positive displacement pump. The collected in a sealed vial and the mixture composition was measured using gas chromatography with a fitted with a flame ionization detector. The molar mass used to find the moles of permeate was calculated using the weighted average molar mass (Mavg) of the permeating component as follows.where xtand Mtare the mole fraction and molar mass of the solvent ‘i’ in the permeate.

[0126] It was ensured that the total permeate collected was less than 3% of the total feed. The separation performance of the membrane was evaluated by calculating the separation factor (<z) of membrane for the given mixture. The separation factor (a) was calculated from the feed composition (xi F, xi F) and permeate composition (xi P, xi P) using the following equation:

[0127] The osmotic pressure corrected permeance (P^) was calculated as follows:where fl P is the transmembrane pressure and TI is the osmotic pressure for the permeating component in the mixture as calculated in Example 5. The osmotic pressure corrected permeance represents the permeance of the solvent for the given transmembrane pressure in absence of the osmotic pressure. The lowering of permeance in mixture separation (calculated using transmembrane pressure) compared to pure solvent permeance is due to osmotic pressure.

[0128] The mixture composition was also estimated from the pure solvent permeance using the chemical potential difference of the ithcomponent in the mixture (A^tz) . The chemical potential difference for each of the component was calculated using its mole fraction in the feed and the permeate (xi F, xl P) and molar volume of each component (P), using the following equation (S):

[0129] For the given composition, the driving force based on the equation (9) which gives the ‘actual driving force’ for each component was calculated. Using this driving force, and the flux of pure components (measured from pure solvent permeation), the permeance of eachof the component for the given ‘external driving force’ was calculated which allowed to estimate the composition of the permeate.

[0130] Separation of complex synthetic naphtha. To demonstrate the applicability of SGO membranes, a pressurized OSRO for a complex synthetic naphtha was performed, composed of straight chain alkanes, branched alkanes, cyclo-alkanes, aromatics, and sulfur containing thiophene. The molar composition and research octane number (RON) of each of the component of the feed is given in Table 3. The complex synthetic naphtha mimics the light naphtha stream coming out of the atmospheric distillation column. It is considered a membrane-based process may be used to separate out the high RON molecules from the naphtha and reduce the sulfur content of the resultant permeating stream. It is also considered the low RON permeating stream with low sulfur content may be sent through a hydrodesulfurization (HDS) into the catalytic reformer. This would reduce the volumetric load of the catalytic reformer and the HDS unit prior to the reformer as a big volume of the naphtha containing the high RON molecules and sulfur containing thiophenes are separated out from the reformer’s input stream. The output stream of the reformer can be blended with the retentate of the membrane process to achieve the desired blend of the gasoline as schematically shown in FIG. 3D. The retentate of the membrane process may or may not be processed in a HDS to reduce it sulfur content based on the requirement of final product. The RON of the feed and permeate (RONavg) of the separation process of complex synthetic naphtha is calculated using the following formula:where xtand RONtare the mole fraction and RON of the solvent ‘i’ in the permeate / feed.

[0131] Molecular Dynamics Simulation: Membrane Model Generation and Permeation. The molecular dynamics (MD) simulations were performed using the GROMACS package (9). The hydrocarbon molecule permeation tests were run in the canonical (NVT) ensemble with a two-chamber setup. The porous GO membrane was frozen in the middle of the simulation box to separate the feed side and permeate side. The dimension of GO membrane is about 25 A x 50 A. A specific number of hydrocarbon molecules were initially placed on the feed chamber with a height of 50 A to achieve various feed pressures, which was computed using the ideal gas law. The number of permeate molecules was monitored to calculate flux in the simulation course. The global velocity rescaling thermostat was applied to keep the fluid temperature at 400 K.

[0132] The force field parameters of hydrocarbon molecules were generated in consistent with the generalized Amber force field (GAFF) following the established procedure. A single layer GO membrane was created by removing a certain number of benzene rings from a pristine graphene membrane, then decorating with 10 -20% oxygen groups using the HierGO tool. The OPLS-AA van der Waals parameters were used to model the GO membrane with neutral graphene carbons and charged oxygen groups. A stacked GO membrane was created by aligning three single-layer GO membranes with an inter-layer spacing of 8.4, 12.2 or 15.0 A. A group of 8 different sized pores was assembled in a single layer GO with the dimension of 49.4 x 51.3 A labeled as “pristine”. Molecular layer deposition was modeled by grafting - Ti(OCH2CH2OH)3 group on oxygen of hydroxyl groups of GO membrane. The resulting GO membrane with the lower level of grafting was denoted as “A Grafted”, while the higher as “B Grafted”. The grafted groups are fully flexible and can implicitly decrease the effective pore size. The selectivity between two molecule was calculated by taking the ratio of the flux of each molecule during the simulation course. The overall selectivity was estimated by multiplying the selectivity from interlayer spacing (8.4 A) and the selectivity from modified in-planes of GO.

[0133] Results. FIG. 1 A shows a schematic of the preferential deposition of an impermeable alkoxide material at the lateral gaps and in-plane pores of a lamellar-stacked GO membrane. A facile vacuum-assisted coating method was used to deposit a stacked GO layer on a porous hollow fiber ceramic support (pore size: 50 nm), followed by vapor-phase molecular layer deposition (MLD) using titanium tetrachloride (TiCk) and ethylene glycol (EG) as the precursors to preferentially deposit alkoxide at the edges and in-plane defects of GO flakes to prepare a continuous “stitched” GO membrane with in-plane pores / structural defects as the dominant transport pathway (FIG. 1 A). For “stitched” GO membranes, SGO was used to represent them in the following discussion. GO was prepared by a previously reported Hummer’s method with slight modifications. Characterization of the synthesized GO by atomic force microscopy (AFM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) (FIGS. 4A-4F) confirmed the single layer feature, GO structure, and various oxygen-containing groups. The concentration of the GO coating solution was adjusted to vary the thickness of the ultrathin GO layer (30-60 nm) on the porous support (FIGS. 5A-5B). With the increase of the GO coating thickness, a structural transition of the stacked GO layers from a relatively “messy” structure was observed for coatings thinner than 30 nm to a more ordered lamellar structure on the top layer for coatings thicker than 30 nm, as suggested by the water permeation measurements (Example 2). A similar variablemicrostructure has been previously reported for GO membranes. The variation of the ratio of the intensity of defects band to graphitic band observed in Raman spectroscopy of the GO coatings with different thicknesses might manifest due to this improper stacking. This lamellar structure of the top GO layer is critical for effective “stitching”.

[0134] Once a lamellar-stacked layer of ultrathin GO was formed, MLD, a vapor-phase deposition technique involving double displacement reactions with two rate-limiting steps was used (FIG. 6), which nucleates at the hydroxyl / high energy sites. After overnight drying of the GO coatings in vacuum, MLD was carried out at 60°C. The high propensity of functional groups (hydroxyl, carboxyl, and carbonyl) at the edges and at in-plane pore / defect sites on GO flakes triggers alkoxide growth. The preferentially deposited alkoxide material is expected to seal the edges, while simultaneously modifying the in-plane pores. XPS and Fourier-transform infrared (FTIR) spectra indicate the formation of new Ti-0 bonds in MLD modified GO, and intensity decrease of the functional groups (carboxylic and hydroxyl) affirms their consumption during the MLD process (FIGS. 7A-7E and 8A-8E).

[0135] As shown in FIGS. 7A and 7B, the full scan of the XPS plot indicates introduction of titanium and some tiny amount of unreacted residual chlorine (from TiCL) in the stitched GO structure which are absent in the pristine GO membrane. As shown in FIGS. 7C and 7D, XPS of the Ols region reveals the formation of new O-Ti bonds in the membrane structure which is absent in the Ols region of the pristine GO membrane. There is notable decrease in the peaks of functional groups (carboxylic and hydroxyl) seen in the Oxygen 1 s region of the XPS scan of stitched GO as compared to that of the pristine GO suggesting the consumption of hydroxyl and carboxylic groups which are present in high concentration at the edges of the GO flakes. As shown in FIG. 3E, the Titanium region of the XPS confirms the formation of Ti-0 bonds which is indicative of the reaction during the MLD process.

[0136] As shown in FIGS. 8A-8E, Fourier-transform infrared (FTIR) spectrograph shows the Ti-O-C bond vibration in stitched GO as opposed to pristine GO membrane. New bands seen at 2900 cm’1are indicative of the newly formed O-Ti-C bonds that are formed during the MLD process (24). The relative decrease of the stretching of the OH bonds (1,700 cm’1) relative to the C=O bonds (1,550 cm’1) in the stitched GO (FIG. 7A) as compared to pristine GO asserts the consumption of hydroxyl groups during MLD. Vibration due to O-Ti-C bonds around 2900 cm’1are absent in pristine GO (FIG. 8B). The intensity of vibration due to O-Ti-C bonds increases with the increase in MLD cycle (FIGS. 7C-7E). Scales of y-axis are same for FIGS. 7B-7E.

[0137] Preferential alkoxide growth at the edges of the single-layered GO flakes deposited on silicon wafer was found, as indicated by the AFM image (FIG. IB). The height profile shows an increment of ~3 nm at the edges, compared to the flat profile of a GO flake (FIG. 4E) and the middle profile of the MLD modified GO flake (FIG. IB), after 5 cycles of MLD. Similar preferential alkoxide deposition at the edges of GO flakes is expected in stacked GO coatings. Therefore, the resulting deposition would be expected to take place preferentially at the edges of GO flakes and might fill the gaps at the edges between laterally adjacent flakes if sufficient MLD cycles were conducted. Ab-initio molecular dynamics (MD) simulation suggests that functional groups have a higher density at edge sites and at larger inplane pores, but a lower density at smaller in-plane pores. Therefore, it is expected that MLD will exhibit preferential growth at the edges and larger in-plane pores, as evidenced from the preferential deposition in AFM images (FIGS. 9A-9H).

[0138] As shown in FIGS. 9A-9H, the surface profile was plotted along a line across the GO flakes (before and after MLD) for the flat part (without edges). A decrease in roughness after 2 cycles of MLD and prominent decrease in roughness after 5 cycles of MLD was observed. It was hypothesized that the titanicone deposition should be taking place preferentially at the larger in-plane pores of GO. Even though the AFM tip cannot pick up nanometer sized in-plane pores on GO, it feels its presence which manifests as surface roughness. As MLD preferentially shrinks these pores, the AFM tip cannot experience these larger in-plane pores, and hence manifests as low roughness.

[0139] After substantial preferential alkoxide deposition (by 60 MLD cycles), the deposition was visible under scanning electron microscopy (SEM), as ridges that trace edges of surface GO flakes (FIG. 1C). Previous literature reports have shown that the deposited alkoxide is non-porous. As expected, N2 permeance (detection limit: I MO'12mol m^ s^ Pa'1) was not observed through a 30 nm GO coating modified by 80 MLD cycles (denoted as SGO-80; similar definition was used in the following discussion if GO coating thickness is 30 nm), sufficient deposition cycles to close the edges as well as in-plane pores. This clearly indicates that alkoxide deposition at edges can effectively block the entrance into the relatively larger and often non-selective interlayer nanochannels for small molecules (4-7 A). Although alkoxide growth via fewer MLD cycles did not show clear patterns of “stitching” under SEM (FIG. 10 for SGO-10), it was adequate to seal the edges, forcing molecules to permeate through modified in-plane pores on GO flakes. SGO membranes were fabricated down to 30 nm having their edges sealed (FIG. ID), as supported by permeation results.

[0140] MLD can also crosslink vertically adjacent GO flakes, stabilizing the membrane nanostructure. This addresses a major issue of swelling in lamellar-stacked GO membranes in solvents. Since the MLD precursors are smaller than the width of the GO interlayer nanochannels, they can diffuse into the entire thickness of the stacked GO layer. This would crosslink GO flakes with each other via alkoxide anchorage at available planar functional groups, “locking” stacked flakes to one another (FIGS. 11 A-l IB). Interlayer nanochannel size, as indicated by the ^ / -spacing (calculated from the XRD patterns, FIGS. 12A-12F), was almost the same in dry and solvent- soaked SGO (MLD cycles > 1) (FIG. IE). In contrast, the pristine GO coating swelt significantly after soaking (FIG. IE) (0 MLD cycle), consistent with the previous literature reports. Only 5 MLD cycles were sufficient to fully “lock” the GO flakes, and no obvious change was observed in the interlayer spacing (FIG. IE). As MLD consumes the hydrophilic functional groups of GO and introduces more carbon atoms, it makes the GO coatings more hydrophobic (FIGS. 13A-13B) compared to the pristine GO, which is a desirable attribute for membranes intended for non-polar solvent separation. Thus, by preferentially depositing alkoxide via MLD, not only were gaps between the edges and modified in-plane pores in lamellar-stacked GO were sealed, but also “locked” (or crosslink) GO flakes in different layers together. This forms a 2D material based ultrathin membrane, as thin as 30 nm, where molecules are forced through the structural defects / pores on the flakes. This disclosure calls this technique “stitching” and the membranes thus formed as SGO membranes.

[0141] The permeance of pure liquid hydrocarbons (FIG. 2A) with 5-8 carbon atoms and varying numbers of branches and different molecular shapes (properties in Table 1) was measured using a permeation system. Due to their chemical inertness and similar properties, the permeation of hydrocarbons offers a good estimate of the pore sizes and size / shape- selective nature of membranes. For SGO-10 (black curve), linear n-hexane (kinetic diameter: 4.3 A) with permeance of 1.23 x K)"6mol m^ s ^Pa'1, permeated -250 times faster than larger, branched isooctane (6.9 A), suggesting an effective membrane pore size between these two molecules. Furthermore, it showed high ideal selectivity (>200; defined as the permeance ratio) for linear n-alkanes over cyclic (cyclohexane and toluene; -6.4 A) and 3-branched (6.9 A) molecules (FIGS. 2A and 14) but low ideal selectivity (<10) over 1-branched (5.0 A) and 2 -branched (5.8 A) ones. This suggests the membrane pore size of SGO-10 should still be larger than 5.8 A. With 5 more MLD cycles (SGO- 15), n-hexane permeance only decreased by 30%, whereas that of slightly larger 2-branched alkane (2,3 -dimethyl butane) decreased by 400%, leading to a n-hexane / 2, 3 -dimethyl butane ideal selectivity of 35 (FIGS. 15A-15B;FIG. 2 A). The additional 5 cycles of MLD, therefore, shrinks the effective pore size to be smaller than 5.8 A. This suggests angstrom-scale pore tunability of the SGO membranes by simply altering the MLD cycles. Further increasing MLD cycles (SGO-30 and SGO-45) resulted in 5 to 10 times decrease of n-alkanes permeance (FIG. 2 A); permeance of larger molecules (isooctane, toluene, and cyclohexane) kept almost the same, probably because of the existence of very small amount of relatively large membrane defects that cannot be effectively sealed by MLD. The highest ideal selectivity of linear over 1 -branched alkane (n- hexane / 3 -methyl pentane) was ~13 for SGO-15. Therefore, SGO membranes have tunable pores between 4.2 and 6.4 A, well in the pore size range of OSRO membranes. In addition, SGO membranes have the thinnest thickness among all the OSRO membranes, thus providing the highest permeance.

[0142] SGO membranes with thicker GO coatings (>30 nm) showed similar ideal selectivity to that of SGO-x (x: 10-45), when number of MLD cycles (x) was the same (FIGS. 16A-16D). However, the thicker membranes exhibited lower permeance (FIGS. 17A-17F). It was hypothesized that a few top “stitched” layers contribute towards selectivity, whereas the bottom layers add more transport resistance. SGO membranes were much less selective (selectivity <10) when GO coating thickness was less than 30 nm (FIG. 18), possibly resulting from the wider openings at the edges of GO flakes in non-lamellar GO coatings, whose morphology was influenced by the support pores. A certain thickness of GO coating is needed for efficient stitching of GO. The thinner GO coating (~20 nm) yields low selectivity when modified with MLD compared to MLD modification (stitching) on 30 nm GO coatings. It was speculated that GO coatings with a thickness less than 20 nm are messier, having wider openings at the edges. With titanicone deposition via MLD in 20 nm GO coatings, it takes more MLD cycles to close the transport pathways through the edges. With such a large number of MLD cycles for titanicone deposition, the pores on the GO flakes get diminished as well. Thus, the dominant effect of selective transport through pores was not obseved. Therefore, formation of lamellar GO layers is essential for effective “stitching” of the GO flakes into a continuous nanofilm, keeping selective in-plane pores open for permeation while sealing edges.

[0143] The bottom messy layers (< 30 nm) act as buffer and are critical for the formation of the top lamellar structure. Increasing thickness of the lamellar layers does not benefit separation but simply hinders permeance, as evidenced by the experimental results and indicated by the series resistance model (Example 4). Reduction of SGO membrane thicknessdown to only a few GO layers it considered possible, provided the starting GO coating forms a lamellar structure for effective “stitching”.

[0144] It was considered that preferential alkoxide deposition by MLD seals the edges of GO flakes, preventing entry of molecules through edges (pathway- 1) into the interlayer nanochannels, and modifies in-plane pores of GO for molecular permeation (pathway-2), as shown schematically in FIGS. 2B and 19; pathway 2 allows permeation of smaller molecules, while hindering larger molecules. Interlayer nanochannels were fixed at 8.4 A after MLD (FIG. IE), which is significantly larger than the linear and branched alkanes in the study. Therefore, good selectivity for such small molecules permeating via pathway- 1 (Fig. 2B-2I) is not expected. However, for SGO-15, a significant difference in permeance of n-hexane and 2,3-dimethyl butane (FIG. 2A) was observed, suggesting openings at GO edges should be sealed and transport pathway-1 should be eliminated (FIG. 2B-II). If transport pathway-1 were not eliminated, both molecules could enter GO nanochannels and would be expected to exhibit viscosity-dependent permeance. Such viscosity-dependent transport was observed in pristine GO membranes, similar to previous literature reports. Furthermore, it was found that by varying the MLD cycles from 10 to 15, permeance for n-hexane decreased by 30%, while for slightly larger 2,3-dimethyl butane, it decreased by more than 400%. Since nanochannel size of SGO membranes remains constant with MLD cycles (FIG. IE), the drastic 2,3- dimethyl butane permeance reduction could be reasonably explained by the shrinkage of inplane pores on GO due to alkoxide growth (FIG. 2B-III). These permeation results suggest that sufficient MLD modification eliminates pathway-1 and modifies pathway-2. Fewer MLD cycles (<10 cycles) was effective to fix the interlayer spacing (FIG. IE) but not enough to block pathway- 1, and thus no obvious selectivity between hydrocarbons with different branches was observed (FIG. 20). Apparently, fixed interlayer spacing may be inadequate to provide good selectivity for small molecules with sizes between 4 and 7 A. Modified in-plane pores on GO act as selective pathways, only when transport through edges is eliminated. The permeation results, along with structural characterization, indicate that via “stitching” non- selective transport through edges (pathway- 1) were eliminated and the modified in-plane pores on GO flakes (pathway-2) for selective molecular transport were utilized.

[0145] To further understand the size / shape selective behavior of MLD modified in-plane defects of GO, MD simulations were performed to study permeation of n-hexane, 3 -methyl pentane, 2,3-dimethyl butane, and cyclohexane (FIGS. 2C-2I). The simulation shows that for entry through the edges, there is no difference in the rate of transport of molecules. On fixing the GO interlayer spacing to 8.4 A (equivalent to that of SGO, FIG. IE), moderate selectivity(~9.5) was observed between the smallest n-hexane and the larger cyclohexane, but negligible selectivity between n-hexane and 2,3-dimethyl butane. Experimentally, SGO-15 exhibited significant selectivity between n-hexane and 2,3-dimethyl butane, which cannot be achieved in the simulation if 2,3-dimethyl butane is allowed through pathway-1. This indicates the importance of edge sealing. Moreover, the simulation shows that MLD can tune the in-plane pores of GO; with increasing MLD cycle (Table 3), the distribution of pores narrows and shifts towards smaller pore sizes (FIG. 2C-II) and provides selectivity for molecules that exhibit no selectivity while traversing pathway- 1. The combination of moderate selectivity from d-spacing and significant selectivity from narrowed structural defects by MLD yields overall selectivity comparable with the experimental results (FIG. 2C- III).

[0146] Liquid hydrocarbon separation is critical in the petroleum industry, and processes like OSRO, which involve no phase change, can save energy substantially. OSRO was conducted by pressurizing liquid hydrocarbon mixtures through SGO membranes (feed pressure: up to 35 bar; permeate pressure: 1.01 bar). Size-based separation was observed for molecules with size difference >1.5 A, allowing to enrich the smaller hydrocarbon (n-hexane) in permeate from its binary mixtures with isooctane (FIG. 3 A). Increasing transmembrane pressure boosts flux (FIG. 3A); n-hexane with >99 mol.% purity from mixtures having varying compositions (FIGS. 3A and 21), with purity marginally higher at higher pressures were recovered. These purity values are close to those estimated from pure solvent fluxes using chemical potential gradient (details in methods, dashed line in FIG. 3 A). The separation factor (SF), defined as molar ratio of components in permeate to that in feed, remained fairly constant up to 35 bar (FIGS. 22A-22B), suggesting rigid nature of SGO. The flux through SGO is 1-2 orders of magnitude higher than most reported OSRO membranes (Table 2). Thus, separation processes designed using SGO are expected to have small industrial footprint. Hydraulic permeance for mixture, defined as total flux normalized by transmembrane pressure, was higher for mixtures having higher n-hexane fractions (FIGS. 23 A-23B), apparently because of the lower osmotic pressure at higher n-hexane fractions.Although thicker GO coatings led to lower hydraulic permeance, n-hexane enrichment, hence SF was fairly constant for different SGO thicknesses (FIGS. 25, 26A-26B, 27). This suggests the top few layers dominate the selectivity, while bottom layers contribute to transport resistance.

[0147] A fairly constant SF for binary mixtures of n-hexane and larger hydrocarbons (isooctane, toluene) for SGO modified with different MLD cycles (FIG. 3B, top) wasachieved. Increasing MLD cycles, however, improves the separation of n-hexane from its mixture with smaller hydrocarbons (3-methyl pentane and 2,3-dimentyl butane; FIG. 3B, top). This indicates tunability of SGO by varying MLD cycles, as supported by pure solvent permeation and MD simulation (FIG. 2A-2C). SGO provided SF (-2) slightly higher than viscosity-dependent permeation for n-hexane / 3 -methyl pentane mixtures (size difference: ~0.7 A). For n-hexane / 2, 3 -dimethyl butane mixtures (size difference: -1.5 A), SF increased from 1.8 to 9 by increasing MLD cycles from 10 to 15 and then kept almost constant with more MLD cycles. All SGO exhibited high SF (-20) for separation of n-hexane from larger molecules (isooctane and toluene; size differences: > 2 A).

[0148] FIG. 3B (bottom) shows the osmotic pressure corrected permeance, defined as total flux normalized by transmembrane pressure excess of osmotic pressure, as a function of MLD cycles for different n-hexane mixtures. Since a portion of applied pressure is required to overcome osmotic pressure (calculated in Example 5), the osmotic pressure corrected permeance might better represent the intrinsic permeation behavior. It was found that the permeance increased with the increase of the molecular size of larger permeating molecules (FIG. 3B, bottom; 10 and 15 MLD cycles), suggesting less interruption / blocking of n-hexane, apparently resulting from the better sized-based sieving for larger molecules; with largest isooctane, permeance of mixture was very close to pure n-hexane permeance (dashed line in FIG. 3B, bottom; FIG. 24). With more MLD cycles (30 and 45 MLD cycles), negligible permeance difference for different mixtures was observed, probably because the dominant transport resistance for n-hexane is from the narrowed surface pores (and probably less pores too), instead of the blocking by larger molecules. Generally, increasing MLD cycles led to lower permeance for separation of n-hexane mixtures (FIGS. 28A-28B, 29A-29C, and 30), suggesting pore shrinkage, probably along with significant reduction of number of pores too.

[0149] FIGS. 3 A-3F show the comparison of SGO membranes with various reported OSRO membranes. Note hydraulic permeance is used as x-axis and separation factor is used as y-axis, therefore only experimentally measured values are compared. Overall permeance (highest permeance: -0.7* 10'6mol m'2- s'1Pa'1) for binary mixture separation using our SGO membranes is over 2 orders of magnitude higher than most reported OSRO membranes, while demonstrating similar or higher SF (Fig. 3C). SGO membranes have two alternative flow pathways - vertically flow through in-plane pores and horizontal flow in 2D nanochannels between flakes. In such cases, the permeation is likely not obstructed by transport of the slowest permeating molecule in mixture. This, along with the ultrathin natureof SGO membranes (top selective layer is thinner than most OSRO membranes, Table 2), allows for the realization of high permeance.

[0150] In petroleum refinery, top product of atmospheric distillation unit - naphtha is composed of low-octane linear and mono-branched alkanes (>50%) along with high-octane branched, cyclic, and aromatic molecules. Typically, naphtha is processed in catalytic reformer to convert linear alkanes into branched / cyclic isomers. High-octane compounds in naphtha are also fed into the reformer, increasing its volumetric load. It was hypothesized that extracting low-octane, linear alkanes from naphtha using SGO membranes and only feeding extracted molecules to catalytic reformer would significantly reduce its volumetric load and increase the process efficiency (Fig. 3D). Rejected high-octane (also larger hydrocarbons) can be blended to achieve the desired research octane number (RON) of gasoline.Considering enormous volume of hydrocarbons processed (3), high permeance membranes are ideal, making SGO a suitable candidate. SGO-15 membrane to complex synthetic naphtha (Table 4) was challenged and fractionation of hydrocarbons based on their sizes and RON was found (FIG. 3E). The permeate was enriched with linear alkanes having low RON, while the high-RON branched / cyclic molecules were rejected (FIG. 31 and 32). Over 100-h continuous operation demonstrated capability of SGO to achieve -95% of the possible reduction of RON (lowest RON is indicated as dashed line in FIG. 3F), while maintaining a stable hydraulic permeance of ~1.23>< 10'7mol in’2s'1Pa'1(FIGS. 3F and 33). An average SF of -43 was maintained between the linear and larger (branched / cyclic) hydrocarbons (FIG. 34). Furthermore, this also reduced -70% thiophene (sulfur containing molecule that poisons catalyst in reformer) from the naphtha stream (FIGS. 4C and 31). This demonstrated potential of SGO membranes for applications in petroleum industry.

[0151] In summary, a versatile vapor-phase preferential deposition process to fabricate ultrathin membranes comprised of stacked 2D GO flakes was demonstrated. The preferential deposition seals edges of GO, interlocks the layers, and shrinks the structural defects, thus forming a continuous, stable “stitched” GO membrane. This eliminates unwanted, non- selective transport pathways and exploits in-plane pores / defects, which are tuned between 4.2 and 7 A by MLD, for size-based separation of small molecules. Because of the ultrathin thickness, SGO membranes showed 2 orders of magnitude higher hydraulic permeance compared to reported OSRO membranes with similar separation factors. As expected, SGO membranes demonstrated efficient RON based fractionation of complex synthetic naphtha. This “stitching” method may open a new avenue for utilizing 2D materials in fabricatingmolecular sieving membranes; by eliminating undesirable transport pathways and exploiting their in-plane defects, membranes can be rationally designed for specific applications.

[0152] Table 1. Dipole moment, dielectric constant, kinetic diameter, molecular weight and boiling point of hydrocarbons used in the example.Dipole Dielectric Kinetic Molecular BoilingHydrocarbon ViscosityMoment Constant Diameter Weight Point p Debye K nm g mol1°C mPa s n-hexane 0.08 1.88 0.43 86.18 68.7 0.29523 -methyl0.01 1.89 0.50 86.2 63.0 0.2909 pentane 2,3 dimethyl0 1.89 0.58 86.18 58.0 0.3898 butane n-pentane 0 1.84 0.43 72.15 36.1 0.2246 n-heptane 0 1.92 0.43 100.21 98.4 0.3959Toluene 0.31 2.38 0.66 92.14 110.6 0.552Cyclohexane 0 2.02 0.67 84.16 80.7 0.887Isooctane 0 1.94 0.69 114.22 99.0 0.48

[0153] Table 2. Comparison of permeance and separation factor of SGO membranes with the state-of-the-art membranes reported in the literature for OSRO applications.

[0154] Table 3. Permeation of the 4 hydrocarbons studied through each of the in-plane pores on GO flake.Permeation RateSerial Pores 3-Methyl 2,3-Dimethyl _ , , n-Hexane „ „ CyclohexaneNo. Size Pentane ButanePristine / A- Pristine / A- Pristine / A-(Ax A) Grafted / B- Grafted / B- Grafted / B-Grafted Grafted Grafted1 12.4x7.6 21 / 14 / 0.3 22 / 5 / 0.1 11 / 4.2 / 0.01 11 / 4.1 / 0.012 11.2x7.6 14 / 11 / 0.01 18 / 4.9 / 0.01 8 / 0.6 / 0.01 19 / 1.2 / 0.013 10.2x6.6 20 / 3 / 1.2 12 / 0.5 / 0.2 10 / 0.15 / 0.1 12 / 0.1 / 0.14 8.5 x 6.6 12 / 2 / 0.9 14 / 0.2 / 0.01 6 / 0.1 / 0.01 2 / 0.01 / 0.015 7.4x6.6 0.01 / 0.01 / 0.01 0.01 / 0.01 / 0.01 0.01 / 0.01 / 0.01 0.01 / 0.01 / 0.016 6.4x5.3 0.01 / 0.01 / 0.01 0.01 / 0.01 / 0.01 0.01 / 0.01 / 0.01 0.01 / 0.01 / 0.017 4.5 x4.3 0.01 / 0.01 / 0.01 0.01 / 0.01 / 0.01 0.01 / 0.01 / 0.01 0.01 / 0.01 / 0.01

[0155] Table 4. Composition of the complex synthetic light naphtha mixture used for demonstration.Hydrocarbon Mole % RON n-Pentane 19 61.7 n-Hexane 60 24.8 n-Heptane 3.5 5.093-Methyl Pentane 3.5 74.52,3-Dimethyl Butane 3.5 100.3Isooctane 3.5 100Cyclohexane 3.5 83Toluene 3.5 118Thiophene <0.1 NA

[0156] The pure water permeance was measured through GO membranes of varying thickness. In thinner GO, the structure may be much looser and not stacked in a lamellar fashion. This may create a messier structure with more probability of water molecules havingstraight through transport pathway along the thickness of the membrane without having to traverse horizontally along the interlayer nanochannels.

[0157] The thinner GO coatings (less than 25 nm) showed an exponential decline in pure water permeance as the thickness of GO coating increases. This contrasts with linear decline in pure water permeance with increase in thickness in the thicker (> 30 nm) GO membranes. This may be due to formation a lamellar stacking after a critical thickness (tc: ~ 30 nm in this example) that forms a continuous layer forcing molecules to traverse horizontally, rather than find short-circuit pathways through pinholes which arises from messy stacking of GO flakes. This critical thickness greatly depends on the porous support on which the membrane is fabricated, and the GO nanosheets and fabrication procedure.

[0158] Two distinct pathways can be considered for transport in a GO membrane. Firstly, through in-plane defects or pinholes formed due to improper stacking of GO nanosheets and secondly, through nanochannels between the two GO sheets. The second pathway is the rate limiting step for transport in a stacked GO membrane. Below the certain critical thickness (tc), there is more probability of finding short-circuit paths (paths where molecules don’t need to traverse the horizontal distance through interlayer nanochannels) across a stacked GO membrane. As thickness increases, these paths diminish and so does the probability of a permeating molecules following such a path. From this probabilistic approach, the permeance (P) through a GO membrane as a function of its thickness (t) is given by the following equation: p = ke{~^ (1)

[0159] This represents the exponential drop of permeance with increasing thickness for a stacked GO membrane. However, the deviation of water permeation from this exponential decay was observed. As thickness increases above a critical thickness, the horizontal flow through nanochannels is rate limiting and determines the permeance. Due to presence of significant graphitic regions within a GO flake, there exists parts of the interlayer nanochannel where water experiences no-slip flow, which increases its transport by three orders of magnitude. For this reason, the water permeance for thicker GO membranes follows linear decay.

[0160] This behavior was also probed using surface Raman spectroscopy (FIGS. 5A-5B). The defect (D) band around ~ 1400 cm’1, indicates various forms of defects in graphene oxide, starting from in-plane lattice defect to out of plane stacking defects. Because the GO material is constant all the different thickness of GO membrane prepared, the effect of in-plane defects on any change in D band observed in Raman was eliminated. To standardize this, the relative intensity of D band was taken, normalized by the intensity of the graphitic (G) band which appears at ~ 1600 cm’1. It was observed that thinner GO membranes have a high value of ratio of intensity of D to G band, compared to the thicker, more lamellar GO coatings, possibly corresponding to messier stacking in thinner GO membranes as opposed to thicker ones. The change from high ratio of intensity of D to G corresponds to the transition of exponential pure water permeance decay with thickness to linear pure water permeance decay as thickness of GO increases.

[0161] Molecular layer deposition stitching of graphene oxide membranes. The interlayer spacing when graphene oxide (GO) flakes are stacked in a lamellar manner, is around -0.85 nm. Due to the presence of large amount of functional groups, especially highly reactive carboxylic groups, the Titanium alkoxide growth, following the chemistry of Molecular Layer Deposition (MLD), which is well established in the literature, should grow preferentially at the edges of the flakes. The growth of the material within a confined space is expected to be a bit different from that on the free single flake deposited on the freshly cleaved mica. It was observed that ten cycles of MLD was enough to grow enough material within the space between the two parallel GO flakes (in a lamellar stacked GO structure) at the edges. This growth completely blocks the space between two layers at the edges, impeding any molecules due to the dense nature of the material. This forms a structure as shown below in the figures included herein and the extended version of this would result in a continuous layer of GO flakes whose edges are sealed as seen in FIG. 1 A. In this disclosure, this phenomenon may be called ‘stitching’. The in-plane defects on the flakes suffer similar fate. However, due to their larger size, they still remain open and contribute to selective transport of molecules up to certain MLD cycles.

[0162] The precursor of MLD (Largest, TiCh, kinetic diameter - 0.46 nm) being smaller than that of the interlayer spacing of stacked GO structure, during the initial cycles of MLD has ample scope to penetrate into the entire structure of stacked GO. This may cause a reaction between the planer hydroxyl groups and the MLD precursors to grow this alkoxide chains that extends from one flake to the adjacent one and finally connecting the two flakes (one possible crosslinking scenario is shown in FIG. IE. This possible cross-linking manifests in the non-swelling behavior of stitched GO membrane as opposed to pristine GO membrane as clearly seen from the XRD peaks in FIGS. 12A-12F.

[0163] For a stacked GO membrane which is perfectly lamellar, should ideally have a sharp pore size distribution from the transport path through the edges. This should be uniformall around the GO sheet and would be equivalent to the nanochannel spacing of GO, i.e., ~ 0.9 nm. With a vapor deposition technique like molecular layer deposition (MLD), it may be easy to close such a uniform sized opening. However, with messy GO structure, where the subsequent layer of GO is not stacked in a lamellar fashion, the distribution of transport pathway at the edges may be large, with larger openings at the edges. This demands more MLD cycles to close the gaps at the edges to seal those unwanted transport paths. This large number of MLD cycles might close the structural defects of GO flakes as well. So, in this example, it was speculated that it is more difficult to see the dominant effect of MLD modified structural defects because of flux contribution from the non-sealed edges. It is considered this is why low selectivity for stitched-GO whose thickness is less than 30 nm was observed in certain instances.

[0164] Transport modeling for stitched-GO membranes, such as, for example, a series resistance model. From the initial assessment from water and solvent permeation, it was estimated that the stitched-GO membrane was composed of 4 distinct layer; 1) the highly porous ceramic support, 2) the messy non-lamellar GO layer (bottom 20-22 nm), 3) the lamellar stacked GO layer, and 4) the skin stitched-GO layer. The structure of the composite membrane is shown in FIG. 1 A. A series resistance model was used to determine the layer that provides the maximum resistance to transport through a stitched-GO membrane. Hexane permeance was measured through ceramic support . P support) and the permeance through MLD modified 20 nm non-lamellar GO membrane on ceramic support (PNLG0, total) - Resistance offered by the ceramic support (RSupport) and the non-lamellar GO coating RNLGO, total is the inverse of the permeance. Using the series resistance model, the resistance can be determined from just the non-lamellar GO layer (RNLG0) '-

[0165] In this example, the total permeance was measured through the composite stitched-GO membrane (Pstitched-Go) • However, the permeance through the two distinct top layers of GO - the lamellar GO layer (PL-G0) and top skin layer (PS-GO) of stitched-GO cannot be measured separately. The resistance from these layer (Rstitched-Go) is just the inverse of the permeance. A fair assumption was made that the top skin layer of the stitched- GO layer is constant for a certain MLD cycle (since the selectivity is fairly constant for stitched-GO membranes with varying thickness for a given MLD cycle). The resistance from the lamellar GO layer was considered to be RL -G0and that from the skin layer to be RS-GO -Thus, the series resistance model for a 30 nm thick stitched-GO membrane can be written as follows:

[0166] When the thickness of the stitched-GO membrane is increased, a fair estimate can be made that the lamellar layer GO is getting thicker, but the skin layer remains the same when modified with the same number of MLD cycles. Thus, the new resistance cannot be considered from the thicker lamellar GO layers as R[-G0, RL-GOandRL-GO for 40 nm, 50 nm and 60 nm thick stitched GO membranes. Similarly, the total resistance from the complete stitched-GO membrane is also varying (as permeance varies) as Rstitched-Go ,Rstitched-Go and Rstitched—Go f°r40 nm, 50 nm and 60 nm thick stitched GO membranes. Hence, the following equations for thicker stitched-GO membranes can be written as:Equations 2 - 5 are for stitched-GO of thickness of 30, 40, 50 and 60 nm respectively.

[0167] The thickness of NL-GO was observed to be around ~25 nm and the total thickness of the thinnest membrane showing lamellar GO structure is 30 nm. From this, it can be concluded that the greatest thickness of the skin layer would be around 5 nm. Under this assumption, the contribution to resistance towards flow for each of the four sections of the stitched-GO membrane could be calculated.

[0168] Calculations for osmotic pressure for OSRO process. The osmotic pressure, 7t, is defined based on the activity, a (= yx), as shown in Equation (1).

[0169] In Equation (1), R is the gas constant, 8.314 J mol'1K’1; T is the operation temperature, K; v is the molar volume, m3mol’1; r is the activity coefficient; x is the molar faction. For practical hexane (A) / toluene (B) separation, the activity coefficient is also considered and is obtained via the Wilson model, which is expressed as Equations (2)-(5) for a binary system:In Equations (2)-(5), VA and VB are the molar volumes of components A and B, respectively, in m3mol'1. The AA(refers to the interaction energy parameters (kJ mol'1) between the zthand jthcomponents; For a hexane (A) / toluene (B) system, the molar volumes of Hexane and Toluene are 130.7 and 106.8 cm3mol'1. ^ABand AAB / qare equal to 220.1 and 634.8 J mol'1, respectively.

[0170] Example of osmotic pressure calculation at the feed side using a 90 / 10 (mole / mole) hexane (A) / toluene (B) feed mixture at 25°C

[0171] Hexane molar fraction in the feed (xA) = 0.9, the toluene molar fraction in feed

[0173] Although the present disclosure has been described with respect to one or more particular embodiment(s) and / or example(s), it will be understood that other embodiment s) and / or example(s) of the present disclosure may be made without departing from the scope of the present disclosure.

Claims

CLAIMS:

1. A graphene oxide membrane comprising a substrate; and a layer comprising a plurality of graphene oxide flakes, wherein at least a portion of, substantially all, or all the graphene oxide flakes are disposed on at least a portion or all of the exterior surface(s) of the substrate, wherein i) the only fluidic connection between opposite sides of the layer is formed by in-plane defect(s) and / or pore(s) of the graphene oxide flakes and / or ii) the graphene oxide membrane comprises a plurality of material domains comprising a material and each of the material domains is disposed on a surface or surfaces of one or more of the graphene oxide flake(s).

2. The graphene oxide membrane of claim 1, wherein at least a portion of, substantially all, or all the graphene oxide flakes each comprise one or more in-plane defects and / or pores, each in-plane defect or pore comprising a size of about 4 Angstroms (A) to about 7 A, forming one or more continuous channel(s) fluidically connecting opposite sides of the layer.

3. The graphene oxide membrane of claim 1, wherein the longest linear dimension of the graphene oxides flakes are substantially parallel or parallel.

4. The graphene oxide membrane of claim 1, wherein the layer comprises a plurality of first graphene oxide flakes disposed on an exterior surface or surfaces of the substrate and a plurality of second graphene oxide flakes disposed on at least a portion, substantially all, or all of the first graphene oxide flakes.

5. The graphene oxide membrane of claim 1, wherein the material is an impermeable material, and wherein the impermeable material is impermeable to one or more hydrocarbon(s) or a hydrocarbon solvent.

6. The graphene oxide membrane of claim 1, wherein at least a portion of the material domains crosslink two or more of the graphene oxide flakes and / or seal at least a portion of, substantially all, or all or all the pores or in plane defects of the graphene oxide flakes.

7. The graphene oxide membrane of claim 6, wherein the two or more graphene oxide flakes are two or more vertically adjacent graphene oxide flakes or two or more coplanar graphene oxide flakes.

8. The graphene oxide membrane of claim 1, wherein the substrate is planar, a fiber, or a hollow fiber.

9. The graphene oxide membrane of claim 1, wherein the substrate comprises one or metal(s), one or more organic material(s), one or more inorganic material(s), or any combination thereof.

10. The graphene oxide membrane of claim 1, wherein the substrate comprises a metal chosen from stainless steel, titanium, zirconium, tin, tungsten, or any combination thereof.

11. The graphene oxide membrane of claim 1, wherein the substrate comprises a ceramic material chosen from aluminum oxide, titanium oxide, zirconium oxide, tin oxide, tungsten oxide, or any combination thereof.

12. The graphene oxide membrane of claim 1, wherein the layer comprises at least one linear dimension of about 3 nanometers (nm) to about 100 nm.

13. The graphene oxide membrane of claim 1, further comprising a non-lamellar graphene oxide layer disposed between the layer and the substrate.

14. The graphene oxide membrane of claim 1, wherein the graphene oxide membrane exhibits a permeance of 10'6mol • m'2• s'1• Pa'1or greater.

15. A method of making a graphene oxide membrane, the method comprising forming a layer comprising a plurality of graphene oxide flakes on at least a portion of, substantially all, or all of the exterior surfaces of a substrate; optionally, drying the layer; and contacting the layer with one or more vapor-phase precursor(s) and, optionally, one or more vapor-phase carbon precursor(s), such that a plurality of material domains are formed.

16. The method of claim 16, wherein the vapor-phase carbon source(s) is / are chosen from polyols and any combination thereof.

17. The method of claim 16, wherein the vapor-phase metal oxide precursor(s) is / are independently chosen from metal halides.

18. The graphene oxide membrane of claim 17, wherein metal halide(s) is / are chosen from metal fluorides, metal chlorides, metal bromides, metal iodides, and any combination thereof.

19. A system comprising one or more graphene oxide membrane(s) of claim 1.

20. The system of claim 19, wherein the graphene oxide membrane(s) is / are disposed in a housing, the housing comprising one or more orafic(es).

21. A method of separating one or more small molecule(s) from and / or enriching one or more small molecule(s) from / in or of a composition comprising two or more different small molecules, the method comprising contacting the composition with one or more graphene oxide membrane(s) of claim 1, wherein one or more of the small molecule(s) is / are separated from the composition and / or enriched in the composition.

22. The method of claim 21, wherein the method provides one or more small molecule(s) at a purity of 98.5% or greater, 99% or greater, 99.5% or greater, 99.9% or greater (based on the total amount of small molecule(s) present).

23. The method of claim 21, wherein one or more or all of the small molecule(s) is / are independently chosen from hydrocarbons, alcohols, and any combination thereof.

24. The method of claim 23, wherein the hydrocarbon(s) is / are independently a C4, Cs, Ce, C7, Cs, C9, or C10 hydrocarbon and / or the alcohol(s) is / are independently a Ci, C2, C3, C4, Cs, Ce, C7, Cs, C9, or C10 alcohol.

25. The method of claim 21, wherein the method is an organic solvent reverse osmosis (ORSO) method, a reverse osmosis desalination method, or a gas separation method.

26. The method of claim 21, wherein the composition is a petroleum distillation product, a gas composition, or seawater.

27. The method of claim 21, wherein the graphene oxide membrane(s) is / are reused in a subsequent separation and / or enrichment.

28. The method according to claim 27, wherein the graphene oxide membranes(s) are cleaned prior to use in each of the subsequent separation(s) and / or enrichment(s).

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