Selective Gas Transport Research Articles

2D Carbonaceous Materials for Molecular Transport and Functional Interfaces: Simulations and Insights.

ConspectusCarbon-based two-dimensional (2D) functional materials exhibit potential across a wide spectrum of applications from chemical separations to catalysis and energy storage and conversion. In this Account, we focus on recent advances in the manipulation of 2D carbonaceous materials and their composites through computational design and simulations to address how the precise control over material structure at the atomic level correlates with enhanced functional properties such as gas permeation, selectivity, membrane transport, and charge storage. We highlight several key concepts in the computational design and tuning of 2D structures, such as controlled stacking, ion gating, interlayer pillaring, and heterostructure charge transfer.The process of creating and adjusting pores within graphene sheets is vital for effective molecular separation. Simulations show the power of controlling the offset distance between layers of porous graphene in precisely regulating the pore size to enhance gas separation and entropic selectivity. This strategy of controlled stacking extends beyond graphene to include covalent organic frameworks (COFs) such as covalent triazine frameworks (CTFs). Experimental assembly of the layers has been achieved through electrostatic interactions, thermal transformation, and control of side chain interactions.Graphene can interface with ionic liquids in various forms to enhance its functionality. A computational proof-of-concept showcases an ion-gating concept in which the interaction of anions with the pores in graphene allows the anions to dynamically gate the pores for selective gas transport. Realization of the concept has been achieved in both porous graphene and carbon molecular sieve membranes. Ionic liquids can also intercalate between graphene layers to form interlayer pillaring structures, opening the slit space. Grand canonical Monte Carlo simulations show that these structures can be used for efficient gas capture and separation. Experiments have demonstrated that the interlayer space can be tuned by the density of the pillars and that, when fully filled with ionic liquids and forming a confined interface structure, the graphene oxide membrane achieves much higher selectivity for gas separations. Moreover, graphene can interface with other 2D materials to form heterostructures where interfacial charge transfers take place and impact the function. Both ion transport and charge storage are influenced by both the local electric field and chemical interactions.Fullerene can be used as a building block and covalently linked together to construct a new type of 2D carbon material beyond a one-atom-thin layer that also has long-range-ordered subnanometer pores. The interstitial sites among fullerenes form funnel-shaped pores of 2.0-3.3 Å depending on the crystalline phase. The quasi-tetragonal phases are shown by molecular dynamics simulations to be efficient for H2 separation. In addition, defects such as fullerene vacancies can be introduced to create larger pores for the separation of organic solvents.In conclusion, the key to imputing functions to 2D carbonaceous materials is to create new interactions and interfaces and to go beyond a single-atom layer. First-principles and molecular simulations can further guide the discovery of new 2D carbonaceous materials and interfaces and provide atomistic insights into their functions.

Microscopic molecular mobility of high-performance polymers of intrinsic microporosity revealed by neutron scattering - bend fluctuations and signature of methyl group rotation.

Polymers of intrinsic microporosity exhibit a combination of high gas permeability and reasonable permselectivity, which makes them attractive candidates for gas separation membrane materials. The diffusional selective gas transport properties are connected to the molecular mobility of these polymers in the condensed state. Incoherent quasielastic neutron scattering was carried out on two polymers of intrinsic microporosity, PIM-EA-TB(CH3) and its demethylated counterpart PIM-EA-TB(H2), which have high Brunauer-Emmett-Teller surface area values of 1030 m2 g-1 and 836 m2 g-1, respectively. As these two polymers only differ in the presence of two methyl groups at the ethanoanthracene unit, the effect of methyl group rotation can be investigated solely. To cover a broad dynamic range, neutron time-of-flight was combined with neutron backscattering. The demethylated PIM-EA-TB(H2) exhibits a relaxation process with a weak intensity at short times. As the backbone is rigid and stiff this process was assigned to bend-and-flex fluctuations. This process was also observed for the PIM-EA-TB(CH3). A further relaxation process is found for PIM-EA-TB(CH3), which is the methyl group rotation. It was analyzed by a jump-diffusion in a three-fold potential considering also the fact that only a fraction of the present hydrogens in PIM-EA-TB(CH3) participate in the methyl group rotation. This analysis can quantitatively describe the q dependence of the elastic incoherent structure factor. Furthermore, a relaxation time for the methyl group rotation can be extracted. A high activation energy of 35 kJ mol-1 was deduced. This high activation energy evidences a strong hindrance of the methyl group rotation in the bridged PIM-EA-TB(CH3) structure.

Metal Confined in 2D Membranes for Molecular Recognition and Sieving towards Ethylene/Ethane Separation.

Membranes with nanochannels have exhibited great potential in molecular separations, while it remains a great challenge to separate molecules with very close physical properties and kinetic diameters (e.g., ethylene/ethane) owing to the lack of size-sieving property and specific affinity. Herein, a metal confined 2Dsub-nanometer channel is reported to successfully discriminate ethylene over ethane via molecular recognition and sieving. Transition metal cations are paired with polyelectrolyte anions to achieve high dissociation activity, forming reversible complexation with ethylene. Aberration-corrected transmission electron microscopy observes that the metals with size of ≈2nm are uniformly confined in graphene oxide (GO) interlayer channels with average height of ≈0.44nm, thereby cooperating the size-sieving effect with a molecular recognition ability toward ethylene and stimulating its selective transport over ethane. The resulting ultrathin (≈60nm) membrane exhibits superior ethylene/ethane separation performance far beyond the polymeric upper-bound. Density functional theory (DFT) and molecular dynamic simulations reveal that the metal@2D interlayer channel provides a molecular recognition pathway for selective gas transport. The proposed metal confined in 2D channel with molecular recognition and sieving properties would have broad application in other related fields such as single-atom catalysis, sensor and energy conversion.

Gas permeation through graphdiyne-based nanoporous membranes

Nanoporous membranes based on two dimensional materials are predicted to provide highly selective gas transport in combination with extreme permeance. Here we investigate membranes made from multilayer graphdiyne, a graphene-like crystal with a larger unit cell. Despite being nearly a hundred of nanometers thick, the membranes allow fast, Knudsen-type permeation of light gases such as helium and hydrogen whereas heavy noble gases like xenon exhibit strongly suppressed flows. Using isotope and cryogenic temperature measurements, the seemingly conflicting characteristics are explained by a high density of straight-through holes (direct porosity of ∼0.1%), in which heavy atoms are adsorbed on the walls, partially blocking Knudsen flows. Our work offers important insights into intricate transport mechanisms playing a role at nanoscale.

Ultrafast and selective gas transport through highly ordered black phosphorene nanochannels

Two-dimensional (2D) materials bring a great opportunity to fabricate molecular sieving membranes that can potentially break the permeability-selectivity trade-off. Although 2D laminar membranes with interlayer nanochannels as molecular sieving channel were widely studied, for most of reported 2D laminar membranes, it is of a great challenge to fabricate highly ordered interlayer nanochannels for mass transport. Herein, we report a novel kind of black phosphorene membrane which is made from the stacking of highly ordered 2D black phosphorene nanoflakes. The as prepared black phosphorene membrane shows H2 permeance > 1000 GPU and H2/CO2 selectivity > 100 for H2/CO2 mixed gas, demonstrating an extremely high gas separation performance. The DFT calculation results demonstrate that the interlayer galleries in the black phosphorene membrane allow the H2 passing through easily while block the other gases with bigger kinetic diameters, matching well with the experimental findings. The present results indicate that the interlayer galleries in the black phosphorene membrane can be applied as molecular sieving channels for gas separation.

Ladder polymers of intrinsic microporosity from superacid-catalyzed Friedel-Crafts polymerization for membrane gas separation

Polymers of intrinsic microporosity have attracted comprehensive attention in membrane-mediated gas separation because of their rigid and contorted structure that facilitates well-defined microporosity for fast and selective gas transport. We report a new macromolecular design synthesizes semi-ladder and fully-ladder polymers of intrinsic microporosity containing 9H -xanthene units by superacid-catalyzed Friedel-Crafts polymerization named SACPs. The prepared SACP membranes display high microporosity with amorphous chain packing structure, high FFV, and high BET surfaces areas. In particular, SACP-3 exhibited the most elevated BET surfaces area of 568 m 2 /g, fractional free volume (FFV) of 0.243, and bimodal micropore size distribution with two maxima at ∼5 and ∼8 Å, respectively. Due to its fully ladder architecture, SACP-3 exhibits highly permeable gas transport with CO 2 permeability of 6497 Barrer and CO 2 /CH 4 selectivity of 7.8, respectively. The microporosity and gas permeation properties of SACP membranes are also demonstrated to be highly tailorable by employing different monomers. The facile polymerization procedure, excellent solubility and processability, highly diverse tunability, and outstanding gas separation performance render SACP membranes attractive for many membrane-mediated gas separation processes. • A new spirobisindane-based fully-ladder polymer of intrinsic microporosity is synthesized with high BET surface area and FFV. • Superacid-catalyzed ladder polymer of intrinsic microporosity displays a bimodal micropore size distribution. • Rigid ladder polymer shows superior plasticization resistance than less microporous semi-ladder polymer.

Hollow-Fiber Membrane Contactor for Biogas Recovery from Real Anaerobic Membrane Bioreactor Permeate.

This study demonstrates the application of hollow-fiber membrane contactors (HFMCs) for the recovery of biogas from the ultrafiltration permeate of an anaerobic membrane bioreactor (AnMBR) and synthetic effluents of pure and mixed CH4 and CO2. The developed membrane degassing setup was coupled with a pilot-scale AnMBR fed with synthetic domestic effluent working at 25 °C. The membrane degassing unit was able to recover 93% of the total dissolved CH4 and 83% of the dissolved CO2 in the first two hours of permeate recirculation. The initial recovery rates were very high (0.21 mg CH4 L−1 min−1 and 8.43 mg CO2 L−1 min−1) and the membrane was able to achieve a degassing efficiency of 95.7% for CH4 and 76.2% for CO2, at a gas to liquid ratio of 1. A higher mass transfer coefficient of CH4 was found in all experimental and theoretical evaluations compared to CO2. This could also be confirmed from the higher transmembrane mass transport resistance to CO2 rather than CH4 found in this work. A strong dependency of the selective gas transport on the gas and liquid side hydrodynamics was observed. An increase in the liquid flow rate and gas flow rate favored CH4 transport and CO2 transport, respectively, over each component. The results confirmed the effectiveness of the collective AnMBR and membrane degassing setup for biogas recovery. Still, additional work is required to improve the membrane contactor’s performance for biogas recovery during long-term operation.

Permeability and selectivity of polymeric membranes based on Poly(ethylene oxide) for carbon dioxide separation.

In membrane industry, recent developments have shown the combination or replacement of classical glassy polymers with crystalline Metallic Organic Frameworks (MOFs), Zeolite Imidazolate Frameworks (ZIFs) or zeolites provides molecularly controlled permeability and selectivity of membranes. However, the main challenges are to get mechanically stable and homogeneous layers of the membranes. By taking advantage of high permeability observed with the rubbery polymers and to their flexible casting properties, Rubbery Organic Frameworks (ROFs) could be used as alternative as gas separation membrane systems. Therefore, nanometric macro-monomers and core connectors have been used to conceive dense (ROFs) for the preparation of polymeric membranes for selective gas transport. With the above concept, in this project, new polymeric membranes based on supramolecular polymeric structures using covalent bonds, were designed selectively for CO2 separation from light gases like N2, and CH4. Then the resulting polymer membranes were characterized spectrometry by (FTIR,1HNMR), their thermal stability were characterized by (TGA and DSC), and the morphological structure was characterized by (SEM and contact angle). The gas permeability measurements for the tested polymeric membranes showed that the permeability of CO2 is higher than other tested gases (N2 and CH4) for the polymeric membranes.

Constructing low-resistance and high-selectivity transport multi-channels in mixed matrix membranes for efficient CO2 separation

Conventional two-dimensional (2D) fillers in membranes have undesirable gas transport resistance owing to their interfacial barriers. In this work, 2D microporous carbon nanoplates (MCNs) were proposed to construct low-resistance and high-selectivity gas transport channels in mixed-matrix membranes (MMMs) to enhance the CO2 separation performance. MCNs were synthesized using a phase-transition material as a removable template and incorporated with Pebax-1657 to prepare MMMs. Micropores measuring 0.58 nm in the MCNs provided low-resistance CO2 diffusion channels that significantly improved CO2 permeability, as confirmed by the diffusion coefficient calculated through molecular simulation. Meanwhile, the random and effective stacking of the MCNs in the MMMs created highly selective gas transport channels that dramatically enhanced CO2/N2 selectivity. The MMMs with 0.5 wt% MCNs showed the best separation performance. In the mixed-gas test, the CO2 permeability reached 160.69 Barrer, and the CO2/N2 selectivity reached 61.2. In the pure-gas test, the CO2 permeability and CO2/N2 selectivity were 123 Barrer and 76, exhibiting distinct increases of 53.0% and 28.8% compared to those of the pristine Pebax membrane. Notably, the best CO2 separation performance of the prepared MMMs exceeded Robeson's upper bound. The proposed template-removal 2D MCNs with low-resistance and high-selectivity transport multi-channels facilitate a new process for molecularly selective and energy-efficient CO2 separation.

Synergy of selective gas transport in bilayered membranes

Dense bilayer PTMSP/PIM-1 membranes and PTMSP/PIM-1 blends were prepared and studied in order to obtain insight into the recently observed synergistic effect of increased CO2/N2 selectivity for thin-film composite (TFC) membranes consist of PIM-1 (selective layer) and PTMSP (gutter layer). It was shown that the mixing of these two polymers does not lead to a synergistic effect in gas permeance, since dense films made by blending of PIM-1 and PTMSP showed classical trade-off permeation/selectivity behavior. Analysis of gas-transport property data using a bicomponent resistance-in-series model allowed us to conclude that the increased N2 transport resistance of the layer formed on the border of the two polymers is presumably responsible for the increased ideal selectivity.

Tuning Selectivities in Gas Separation Membranes Based on Polymer-Grafted Nanoparticles.

Polymer membranes are critical to many sustainability applications that require the size-based separation of gas mixtures. Despite their ubiquity, there is a continuing need to selectively affect the transport of different mixture components while enhancing mechanical strength and hindering aging. Polymer-grafted nanoparticles (GNPs) have recently been explored in the context of gas separations. Membranes made from pure GNPs have higher gas permeability and lower selectivity relative to the neat polymer because they have increased mean free volume. Going beyond this ability to manipulate the mean free volume by grafting chains to a nanoparticle, the conceptual advance of the present work is our finding that GNPs are spatially heterogeneous transport media, with this free volume distribution being easily manipulated by the addition of free polymer. In particular, adding a small amount of appropriately chosen free polymer can increase the membrane gas selectivity by up to two orders of magnitude while only moderately reducing small gas permeability. Added short free chains, which are homogeneously distributed in the polymer layer of the GNP, reduce the permeability of all gases but yield no dramatic increases in selectivity. In contrast, free chains with length comparable to the grafts, which populate the interstitial pockets between GNPs, preferentially hinder the transport of the larger gas and thus result in large selectivity increases. This work thus establishes that we can favorably manipulate the selective gas transport properties of GNP membranes through the entropic effects associated with the addition of free chains.

Highly selective gas transport channels in mixed matrix membranes fabricated by using water-stable Cu-BTC

Application of metal-organic frameworks (MOFs) in the field of gas separation has been widely explored, however most of the reported MOFs are sensitive to hydrolysis, restricting their applications under practical environments. In this work, Cu-BTC with distinguishing high resistance to hydrolysis was prepared through in-situ functionalization with sodium citrate (SC). The obtained Cu-BTC-SC can hold its structure integrity and preserve its original gas adsorption capacity even after 10 days' immersion in water. On this basis, mixed matrix membranes (MMMs) containing different loadings of Cu-BTC-SC in Pebax® 1657 were fabricated and applied for CO2/N2 and CO2/CH4 separation under humid conditions. The MMMs displayed excellent long-term stability towards humidified test conditions as well as improved CO2 separation performance compared with the pristine Pebax® 1657 membrane. Specifically, the membrane incorporated with 15 wt% of Cu-BTC-SC demonstrated a CO2 permeance of 1102.5 GPU together with a CO2/N2 selectivity of 54.8 for the CO2/N2 mixed gas, and a CO2 permeance of 1069.6 GPU together with a CO2/CH4 selectivity of 32.5 for the CO2/CH4 mixed gas, surpassing the Robeson upper bounds for CO2/N2 and CO2/CH4 separation. These results demonstrate a potential effective strategy for improving the water stability of MOFs and suggest a promising candidate for the fabrication of high performance membranes for practical large-scale CO2 separation applications.

Pore size effect on selective gas transport in shale nanopores

In shale gas production, gas composition may vary over time. To understand this phenomenon, we use molecular dynamics simulations to study the permeation of CH4, C2H6 and their mixture from a source container through a pyrophyllite nanopore driven by a pressure gradient. For a pure gas, the flow rate of CH4 is always higher than that of C2H6, regardless of pore size. For a 1:1 C2H6: CH4 mixture, however, C2H6:CH4 flow rate ratio is higher than the compositional ratio in the container (i.e., 1:1) when the pore size is smaller than ~1.8 nm. The selective transport is caused by the competitive adsorption of C2H6 over CH4 in the nanopore. The selectivity is also determined by the interplay between the surface diffusion of the adsorbed molecules and the viscous flow in the center of the pore, and it diminishes as the viscous flow becomes to dominate the surface diffusion when the pore size becomes larger than 1.8 nm. Our work shows that compositional differentiation of shale gas in production is a consequence of nanopore confinement and therefore a key characteristic of an unconventional reservoir. The related compositional information can potentially be used for monitoring the status of a production well such as its recovery rate.

Understanding Gas Transport Behavior through Few-Layer Graphene Oxide Membranes Controlled by Tortuosity and Interlayer Spacing.

Here, we elucidate the gas transport behavior through few-layer graphene oxide membranes (FGOMs) that have a systematically controlled diffusion pathway, including tortuosity and channel width. The obtained unusual gas permeation order (especially, CH4 > O2 > N2) of the FGOM provides strong evidence that gas molecules can indeed penetrate through the empty voids created by horizontally assembled GO, which allows selective gas transport features. These unique transport features of the FGOM originate from its continuously connected channel structure, which is an analogue of an ultrapermeable glassy polymer with extremely large free volumes in dense films. Furthermore, variation of the channel width in the range of 0.50-0.55 nm leads to notable changes in the gas permeance orders related to CH4, indicating that there is a transition region for switching the gas transport mechanism between a molecular sieving character and the solution-diffusion model.

Enhanced quality of transfer-free graphene membrane for He/CH4 separation

Atomically thin porous graphene as a selective layer is believed to be a promising candidate to exhibit superior gas separation performance. While small-area graphene membranes have been successfully fabricated, crack-free and large-area graphene transfer onto the porous substrate remains a great challenge. Large defects, up to micron-scale, can emerge during the conventional graphene transfer techniques. In this work, we improved transfer-free graphene membrane fabrication through small pore introduction into copper foil. We apply the typical photolithography process to establish a patterned mask on the backside of the graphene-covered copper foil followed by a chemical etching process to drill small-sized pores into the copper foil, with pore sizes varying between 200 nm and 4 µm. To measure the membrane performance, He/CH4 separation is carried out. The observed selectivity ~3.5 shows 28% enhancement in comparison to the membrane prepared through the transfer step (~2.5). The maximum measured selectivity achieved in this work is higher compared to the Knudsen selectivity (2), which can confirm the molecular-sieving-based selective gas transport through the angstrom-size intrinsic defects of the graphene film. In addition to the high permeance (1.19 × 10−5 mol/m2·s·Pa) achieved through the graphene-based membrane, its selectivity also exceeds the Robeson upper bound for polymeric membranes, proving the higher performance acquired compared to other polymeric membranes. The enhancement in transfer-free graphene membrane quality can bring us one step closer to realizing graphene’s full potential and developing large-area and crack-free graphene membranes.

Molecular tunneling in large tubes of 3D nitrogenated micropore materials

We study new 3D materials, π-conjugated microporous polymers (aza-CMPs), where 2D layers are connected by methanoic and ethanoic acid groups. The crystal parameters and the band structures are calculated. The energy gaps for a 3D crystal with the ethanoic (Eg3D=1.04eV) and methanoic (Eg3D=1.26eV) acid connecting groups are smaller than those for a 2D material (Eg2D=1.64eV). The symmetry of a 3D crystal becomes lower than for a 2D aza-CMP by changing selection rules and optical spectra. The upper hole bands become non-degenerate for an aza-CMP with ethanoic acid and are doubly degenerate for an aza-CMP with methanoic acid connecting groups. The upper bands in the valence zone become more flat implying heavier hole masses that lead to lower hole mobilities. We also investigate molecular transport through the channels. We find that a CH4 molecule moves easily along the tube in a large pore material and is hindered in a small pore (with ethanoic acid connecting groups) crystal. The ammonia molecule is attached to the tube walls with a large activation energy (about 0.39eV). For the large molecules NR4 (R=CH3, C2H5), chemical reactions take place in the narrow tubes. In particular, an N(CH3)4 molecule decays in the fragments. The two atoms, N and C, are attached to the tube walls, and the three molecular fragments, CH4, C2H6, and H2, can further tunnel along the channels. The low energy gaps and tunable transport properties of π-conjugated microporous polymeric structures can be used for electronics, energy harvesting, gas separation, selective gas transport, hydrogen storage, and biomedicine (drug delivery).

Novel Protic Ionic Liquid Composite Membranes with Fast and Selective Gas Transport Nanochannels for Ethylene/Ethane Separation.

Protic ionic liquids (PILs) were utilized for the fabrication of composite membranes containing silver salt as the C2H4 transport carrier to perform C2H4/C2H6 separation for the first time. The intrinsic nanostructures of PILs were adopted to construct fast and selective C2H4 transport nanochannels. The investigation of structure-performance relationships of composite membranes suggested that transport nanochannels (polar domains of PILs) could be tuned by the sizes of cations, which greatly manipulated activity of the carrier and determined the separation performances of membranes. The role of different carriers in the facilitated transport was studied, which revealed that the PILs were good solvents for dissolution and activation of the carrier due to their hydrogen bond networks and waterlike properties. The operating conditions of separation process were investigated systemically and optimized, confirming C2H4/C2H6 selectivity was enhanced with the increase of silver salt concentration, the flow rate of sweep gas, and the feed ratio of C2H4 to C2H6, as well as the decrease of the transmembrane pressure and operating temperature. Furthermore, the composite membranes exhibited long-term stability and obtained very competitive separation performances compared with other results. In summary, PIL composite membranes, which possess good long-term stability, high C2H4/C2H6 selectivity, and excellent C2H4 permeability, may have a good perspective in industrial C2H4/C2H6 separation.

Molecular origins of fast and selective gas transport in pentiptycene-containing polyimide membranes and their physical aging behavior

This paper reports comprehensive characterization and detailed analyses of microporous structure and fundamental gas transport properties for a series of new pentiptycene-containing polyimide gas separation membranes prepared from custom-synthesized pentiptycene-based diamines and 4,4′-hexafluoroisopropylidene bisphthalic dianhydride (6FDA) to identify the molecular origins for fast and selective gas transport. Both experimental characterizations of inter-chain spacing and microporosity and molecular modeling analysis of chain conformations and rigidity suggested that rigid H-shape pentiptycene units effectively disrupted chain packing, resulting in large fractional free volume and consequent high gas permeabilities in these membranes. Atomic-level detection of free volume architecture by positron annihilation lifetime spectroscopy (PALS) analysis revealed a bimodal microcavity size distribution with cavity sizes of d4~7–8Å and d3~3–4Å in this series of membranes. The microcavity size and size distribution were found to be sensitively affected by the substituent groups in the pentiptycene monomer structure based on the mechanism of “partial filling” of internal molecular cavities defined by the shape of pentiptycene units. Analysis of fundamental gas transport properties in terms of diffusivity (D) and solubility (S) coefficients demonstrated that size sieving mechanism (diffusivity contribution) dominates the gas transport in these polymers and bimodal microcavity size distribution with ultrafine microporosity is responsible for the excellent H2-related gas separation performance. Superior resistance against physical aging was observed for these high-free-volume polymers, which is ascribed to the stable, configuration-induced microcavity structure constructed by the rigid pentiptycene units.

Preparation and gas transport properties of triptycene-containing polybenzoxazole (PBO)-based polymers derived from thermal rearrangement (TR) and thermal cyclodehydration (TC) processes

Triptycene-containing PBO-based polymers with ultrafine microporosity promoting ultrafast and highly selective gas transport.

Enhancing Separation and Mechanical Performance of Hybrid Membranes through Nanoparticle Surface Modification.

Membranes with selective gas transport properties and good mechanical integrity are increasingly desired to replace current energy intensive approaches to gas separation. Here, we report on the dual enhancement of transport and mechanical properties of hybrid cross-linked poly(ethylene glycol) membranes with aminopropyl-modified silica nanoparticles. CO2 permeability in hybrid membranes exceeds what can be predicted by Maxwell's equation and surpasses values of the pure polymer. Furthermore, dynamic mechanical and thermogravimetric analyses reveal increases in both the storage modulus and thermal stability in hybrid membranes, with respect to silica nanoparticle loading.