•Based on molecular simulations and predictive permeation models, amulti scale methodwas developed in order topredict CO2 and CH4 permeability and selectivity of mixed matrix membranes (MMMs) with ...ZIF fillers. The validity our computational approach was confirmed by actual permeability and selectivity experiments on ZIF-8 MMMs based on Pebax and 6FDA-DAM polymers.•With the aid of molecular simulations, CO2 and CH4 permeabilities were calculated for a large number of ZIF analogues, in which the building units (metal, linker and functional group) have been systematically modified.•MMMs with the aforementioned ZIF analogues as fillers, exhibitunprecedentedCO2/CH4separation performance.•The enhanced performance of these MMMs is attributed mainly to the smaller and/or less flexible pores of the modified ZIFs that enhance the kinetic-based separation of the smaller CO2 over the larger CH4.
Zeolitic-imidazolate frameworks (ZIFs) are considered as promising nanoporous solids for the development of membranes with exceptional gas separation properties. In this work, we show how molecular-scale modifications can lead to ZIF variants, which can greatly enhance the CO2/CH4 separation performance of mixed-matrix membranes (MMMs) when used as additives. First the permeabilities of CO2 and CH4 in ZIF-8 are estimated with the help of molecular simulations. Based on these results and a macroscopic model, the performance of MMMs with ZIF-8 as fillers is deduced. The validity of this approach is confirmed through experiments by developing flat-sheet ZIF-8 based nanocomposite membranes with two typical polymers (rubbery Pebax® MH1657 and glassy 6FDA-DAM) having different permeability properties. In a subsequent step, we design computationally new ZIF crystals, by changing the original metal, organic linker and functional group of ZIF-8, and the CO2/CH4 separation performance of MMMs with the new ZIF variants is predicted. Our results reveal that some of these MMMs exhibit an unprecedented CO2/CH4 separation performance, which surpasses any reported MMM and is directly attributed to the enhanced sieving capacity of the modified ZIF fillers. In conclusion, this work highlights the effectiveness of ZIF nanoengineering as a means to develop highly selective CO2 membranes.
Highly proton conductive nanocomposite membranes were synthesized by incorporating modified silica nanoparticles bearing different kinds of acid functionalities into Nafion. The short oligomeric ...corona, containing either phosphonate or sulfonate functional groups, leads to membranes with non-aggregated, discrete nanoparticles acting synergistically with the polymer. The new membranes exhibit significantly increased proton conductivity in all relative humidities and temperatures, however unprecedented behavior is observed at elevated temperatures (>80 °C) and/or low relative humidity. Pulse Field Gradient NMR measurements demonstrate that, in contrast to neat Nafion, which shows a precipitous decrease in the self-diffusion of water above 80 °C, the nanocomposite membranes were able to maintain high proton diffusivities pointing to adequate hydration levels for several hours at 130 °C without any external humidification. Furthermore, thermal and dynamic mechanical analysis reveal that the nanocomposite membranes retain their stiffness at much higher temperatures up to 200 °C compared to recast Nafion opening the way for high temperatures applications. The overall high ionic conductivity of the nanocomposite membranes especially above 80 °C coupled with their exceptional water retention capability and mechanical robustness makes them very attractive for potential use in fuel cell applications.
•Development of new highly proton conductive Nafion nanocomposite membranes.•Incorporation of functionalized silica nanoparticles bearing ionic groups.•Enhanced proton conductivity, water retention and stability are observed.•Remarkable performance above 80 °C surpassing state-of-the art polymer systems.
Encapsulation of poorly water-soluble drugs into mesoporous materials (e.g. silica) has evolved as a favorable strategy to improve drug solubility and bioavailability. Several techniques (e.g. spray ...drying, solvent evaporation, microwave irradiation) have been utilized for the encapsulation of active pharmaceutical ingredients (APIs) into inorganic porous matrices. In the present work, a novel chalcone (KAZ3) with anticancer properties was successfully synthesized by Claisen-Schmidt condensation. KAZ3 was loaded into mesoporous (SBA-15 and MCM-41) and non-porous (fumed silica, FS) materials via two techniques; electrohydrodynamic atomization (EHDA) and solvent impregnation. The effect of both loading methods on the physicochemical properties of the particles (e.g. size, charge, entrapment efficiency, crystallinity, dissolution and permeability) was investigated. Results indicated that EHDA technique can load the active in a complete amorphous form within the pores of the silica particles. In contrast, reduced crystallinity (~79%) was obtained for the solvent impregnated formulations. EHDA engineered formulations significantly improved drug dissolution up to 30-fold, compared to the crystalline drug. Ex vivo studies showed EHDA formulations to exhibit higher permeability across rat intestine than their solvent impregnated counterparts. Cytocompatibility studies on Caco-2 cells demonstrated moderate toxicity at high concentrations of the anticancer agent. The findings of the present study clearly show the immense potential of EHDA as a loading technique for mesoporous materials to produce poorly water-soluble API carriers of high payload at ambient conditions. Furthermore, the scale up potential in EHDA technologies indicate a viable route to enhance drug encapsulation and dissolution rate of loaded porous inorganic materials.
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A novel, one-step, wet-free, environmental friendly and high-yield method for producing few-layer graphene powders with large surface areas (up to 800 m2/g) and narrow nanopore sizes (0.7–0.8 nm) ...using plasma-induced exfoliation of natural graphite is presented. Advanced characterization techniques were employed, including scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction and N2 gas adsorption/desorption measurements at 77 K, to investigate the morphological, elemental, structural and textural/porosity properties of these nanomaterials. Fully reversible H2 gas adsorption/desorption isotherms with maximum gravimetric capacities of up to ∼2 wt.% at 77 K and ∼60 bar are reported here. The H2 storage performance at 77 K is well correlated with certain textural features such as specific surface area and microporosity. The results of this work provide a valuable feedback for further research on plasma-processed graphene-based materials towards efficient H2 storage via cryo-adsorption.
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•Few-layer graphene-like flakes were prepared by plasma-processing of natural graphite.•Demonstrated large surface areas (up to 800 m2/g) and nanopore sizes (below 0.8 nm).•Characterization was performed using SEM, TEM, XPS, XRD and N2 porosimetry methods.•H2 storage behavior was evaluated by adsorption/desorption at 77 K and up to 100 bar.•Reversible H2 adsorption isotherms with maximum uptake of up to ∼2 wt.% at ∼60 bar.
•Preparation of highly stable CaO-based sorbents for energy storage purposes.•SEM and XRD analysis of synthesized CaO-based sorbents.•Analysis of cyclic stability and maximum CO2 uptake capacity over ...20 cycles.•Influence of hydration temperature on intermediate regeneration of CaO.•Comprehensive energetic evaluation of different natural and synthesized materials.
The cyclic carbonation/calcination reaction of CaO is discussed as a thermochemical energy storage system. Especially the high reaction temperature enables high theoretical energetic efficiencies. A severe issue is the strong cycle-to-cycle degradation of the material due to sintering. In order to overcome this, two different approaches are studied in this work: (1) Intermediate hydration of natural CaO to regenerate the sorbent. (2) Preparation of pure CaO and CaO/Al2O3 composites with different Ca/Al molar ratios. All materials prepared are structurally and morphologically characterized and for the evaluation of the sorbents, the CO2 uptake capacity during carbonation reaction is measured over multiple cycles. Besides the successful proof of an optimized cyclic stability, the energetic efficiency and storage density of the synthesized samples is calculated and compared to the benchmark material, natural CaO. In case of storage density, values of up to 3.5 times and in case of energetic efficiency, a factor of 1.2 referred to natural CaO are obtained within the 20th cycle.
The targeted synthesis of metal–organic frameworks (MOFs) with open metal sites, following reticular chemistry rules, provides a straightforward methodology toward the development of advanced porous ...materials especially for gas storage/separation applications. Using a palladated tetracarboxylate metalloligand as a 4-connected node, we succeeded in synthesizing the first heterobimetallic In(III)/Pd(II)-based MOF with square-octahedron (soc) topology. The new MOF, formulated as In3O(L)1.5(H2O)2Cl·n(solv) (1), features the oxo-centered trinuclear clusters, In3(μ3-O)(−COO)6, acting as trigonal-prismatic 6-connected nodes that linked together with the metalloligand trans-PdCl2(PDC)2 (L 4– ) (PDC: pyridine-3,5-dicarboxylate) to form a 3D network. After successful activation of 1 using supercritical CO2, high-resolution microporous analysis revealed the presence of small micropores (5.8 Å) with BET area of 795 m2 g–1 and total pore volume of 0.35 cm3 g–1. The activated solid shows high gravimetric (92.3 cm3 g–1) and volumetric (120.9 cm3 cm–3) CO2 uptake at 273 K and 1 bar as well as high CO2/CH4 (15.4 for a 50:50 molar mixture) and CO2/N2 (131.7 for a 10:90 molar mixture) selectivity, with moderate Q st 0 for CO2 (29.8 kJ mol–1). Slight modifications of the synthesis conditions led to the formation of a different MOF with an anionic framework, having a chemical formula Me2NH2In(L)·n(solv) (2). This MOF is constructed from pseudotetrahedral, mononuclear In(−COO)4 nodes bridged by four L 4– linkers, resulting in a 3D network with PtS topology.
A nanoporous metal–organic framework material, exhibiting an IRMOF-1 type crystalline structure, was prepared by following a direct solvothermal synthesis approach, using zinc nitrate and ...terephthalic acid as precursors and dimethylformamide as solvent, combined with supercritical CO2 activation and vacuum outgassing procedures. A series of advanced characterization methods were employed, including scanning electron microscopy, Fourier-transform infrared radiation spectroscopy and X-ray diffraction, in order to study the morphology, surface chemistry and structure of the IRMOF-1 material directly upon its synthesis. Porosity properties, such as Brunauer–Emmet–Teller (BET) specific area (∼520 m2/g) and micropore volume (∼0.2 cm3/g), were calculated for the activated sample based on N2 gas sorption data collected at 77 K. The H2 storage performance was preliminary assessed by low-pressure (0–1 bar) H2 gas adsorption and desorption measurements at 77 K. The activated IRMOF-1 material of this study demonstrated a fully reversible H2 sorption behavior combined with an adequate gravimetric H2 uptake relative to its BET specific area, thus achieving a value of ∼1 wt.% under close-to-atmospheric pressure conditions.
•IRMOF-1 powder synthesized by solvothermal method and supercritical CO2 activation.•Cubic nano-sized crystals with ∼520 m2/g specific area and ∼0.2 cm3/g pore volume.•Fully reversible H2 sorption isotherms with an uptake of ∼1 wt.% at 77 K and ∼1 bar.•High ratio of H2 uptake to specific area under low pressures compared to other MOFs.
Excellent-quality graphene sheets produced via the direct liquid phase exfoliation of highly crystalline graphite (avoiding any oxidative treatment), were employed for the first time as 2D scaffolds ...for the in-situ synthesis of zeolitic-imidazolate-framework (ZIF-8) material. Our synthetic approach involved the efficient, urea-assisted exfoliation of natural graphite (without using any acids), and the subsequent selective, mild functionalization of the resulting high-quality graphene sheets with benzoic acid functional groups. The graphene derivatives were next decorated via the in-situ development of ultrasmall (approx. 30 nm) ZIF-8 nanocrystals. We discuss the critical role of the functionalized graphene to the selective nucleation and crystal growth of ZIF-8 nanocrystals exclusively at their surface. In-depth gas sorption studies of different gases revealed that the novel ZIF-8@Graph nano-composites exhibited improved porosity (in terms of surface area and pore volume) compared to analogous Graphene Oxide/ZIF-8 hybrids. In addition, the gate effect of the ZIF-8 nanocrystals anchored onto the high-quality graphene, was found very different compared to bulk ZIF-8, a behavior that is attributed mainly to the significantly smaller crystal size and the perfect 2D confinement of ZIF-8 along graphene. Finally, preliminary CO2 adsorption properties of the synthesized novel nano-composites are reported, at near ambient temperature.
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•Excellent-quality graphene (avoiding any oxidative treatment), was employed as 2D scaffold.•In-situ growth of Zeolitic-Imidazolate-Framework (ZIF-8) material at graphene sheets.•Full and uniform decoration of graphene sheets with crystalline ZIF-8 ultra-small nanocrystals.•The nanocomposites exhibited significantly improved values of surface area and pore volume.
In the present work, a nanoporous (pore width~0.7nm) graphene-based sponge-like material with large surface area (~350m2/g) was synthesized by wet chemical reduction of graphene oxide in combination ...with freeze-drying. Surface morphology and elemental composition were studied by scanning and transmission electron microscopy combined with energy dispersive X-ray spectroscopy. Surface chemistry was qualitatively examined by Fourier-transform infrared spectroscopy, while the respective structure was investigated by X-ray diffraction analysis. Textural properties, including Brunauer–Emmet–Teller (BET) surface area, micropore volume and surface area as well as pore size distribution, were deduced from nitrogen gas adsorption/desorption data obtained at 77K and up to 1bar. Potential use of the spongy graphene for gas storage and separation applications was preliminarily assessed by low-pressure (0–1bar) H2, CO2 and CH4 sorption measurements at different temperatures (77, 273 and 298K). The adsorption capacities for each gas were evaluated up to ~1bar, the isosteric enthalpies of adsorption for CO2 (28–33kJ/mol) and CH4 (30–38kJ/mol) were calculated using the Clausius–Clapeyron equation, while the CO2/CH4 gas selectivity (up to 95:1) was estimated using the Ideal Adsorbed Solution Theory (IAST).
•Nanoporous sponge produced by chemical reduction of graphene oxide and freeze-drying•Characterization performed using SEM, EDS, TEM, FT-IR, BET and XRD methods•Gas storage performance evaluated towards H2, CO2 and CH4 adsorption up to 1bar•CO2 over CH4 gas selectivity estimated between 45 and 95 at 273K using the IAST model
We report grand canonical Monte Carlo studies of nitrogen (77 K) and carbon dioxide (253 K) adsorbed in graphitic slit pores with surface oxygen functionalities. The analysis is focused on the ...molecular orientation within the adsorption layers and the influence of surface heterogeneity on molecular density distributions. The oxygen-containing surface functionalities act like additional adsorption sites along the graphitic basal plane that interacts also electrostatically with the fluid. Our simulations reveal that the molecular orientation of both adsorbate particles changes greatly upon increasing surface heterogeneity, while the effect of the pore size on the adsorption behaviour is also discussed. The detailed microscopic description of the adsorbed layer on oxygen modified carbon surfaces can be used to highlight thermodynamic features of gas adsorption on real surfaces such as layering transitions and surface area calculations.
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