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International audience; As global energy demand increases, natural gas recovery from source rocks is attracting considerable attention since recent development in shale extraction techniques has made the recovery process economically viable. Kerogens are thought to play an important role in gas recovery; however, the interactions between trapped shale gas and kerogens remain poorly understood due to the complex, heterogeneous microporous structure of kerogens. This study examines the diffusive behavior of methane molecules in kerogen matrices of different types (Type I, II, and II) and maturity levels (A to D for Type II kerogens) on a molecular scale. Models of each kerogen type were developed using simulated annealing. We employed grand canonical Monte Carlo simulations to predict the methane loadings of the kerogen models and then used equilibrium molecular dynamics simulations to compute the mean square displacement of methane molecules within the kerogen matrices under reservoir-relevant conditions, that is, 365 K and 275 bar. Our results show that methane self-diffusivity exhibits some degree of anisotropy in all kerogen types examined here except for Type I-A kerogens, where diffusion is the fastest and isotropic diffusion is observed. Self-diffusivity appears to correlate positively with pore volume for Type II kerogens, where an increase in diffusivity is observed with increasing maturity. Swelling of the kerogen matrix up to a 3% volume change is also observed upon methane adsorption. The findings contribute to a better understanding of hydrocarbon transport mechanisms in shale and may lead to further development of extraction techniques, fracturing fluids, and recovery predictions

Biohybrid nanopores combine the durability of solid-state nanopores with the precise structure and function of biological nanopores. Particular care must be taken to control how biological nanopores adapt to their surroundings once they come into contact with the solid-state nanopores. Two major challenges are to precisely control this adaptability under dynamic conditions and provide predesigned functionalities that can be manipulated for engineering applications. In this work, we report on the computational design of a distinctive class of biohybrid active membrane layers, built from the directed-insertion of an aquaporin-incorporated lipid nanodisc into a model alkyl-functionalized silica pore. We show that in an aqueous environment when a pressure difference exists between the two sides of the solid-state nanopore, the preferential interactions between the hydrocarbon tail of the lipid molecules that surround the aquaporin protein and the alkyl group functionalizing the interior surface of the silica nanopore enable the insertion of the aquaporin-incorporated lipid shell into the nanopore by forcing out the water molecules. The same preferential interactions are responsible for the structural stability of the inserted aquaporin-incorporated lipid shell as well as the water sealing properties of the lipid-alkyl interface. We further show that the aquaporin protein stabilized in the alkyl-functionalized silica nanopore preserves its biological structure and function in both pure and saline water, and, remarkably, its water permeability is equal to the one measured in the biological environment. The designed biohybrid membrane could pave the way for the development of durable transformative devices for water filtration.

A one‐dimensional nanotubular metal–organic framework (MOF) [Ni(Cu‐H4TPPA)]⋅2 (CH3)2NH2 + (H8TPPA=5,10,15,20‐tetrakis[p‐phenylphosphonic acid] porphyrin) constructed by using the arylphosphonic acid H8TPPA is reported. The structure of this MOF, known as GTUB‐4, was solved by using single‐crystal X‐ray diffraction and its geometric accessible surface area was calculated to be 1102 m2 g−1, making it the phosphonate MOF with the highest reported surface area. Due to the extended conjugation of its porphyrin core, GTUB‐4 possesses narrow indirect and direct bandgaps (1.9 eV and 2.16 eV, respectively) in the semiconductor regime. Thermogravimetric analysis suggests that GTUB‐4 is thermally stable up to 400 °C. Owing to its high surface area, low bandgap, and high thermal stability, GTUB‐4 could find applications as electrodes in supercapacitors., A 1D nanotubular MOF, GTUB‐4, was constructed by using the highly conjugated arylphosphonic acid H8‐TPPA. The structure of this metal–organic framework (MOF) was solved by using single‐crystal X‐ray. GTUB‐4 is characterized by high surface area and, due to the extended conjugation of its porphyrin core, possesses narrow indirect and direct bandgaps in the semiconductor regime. Owing to its high surface area, low band gap, and high thermal stability, GTUB‐4 could find applications as electrode material in supercapacitors.

Herein, we report a semiconductive, proton-conductive, microporous hydrogen-bonded organic framework (HOF) derived from phenylphosphonic acid and 5,10,15,20‐tetrakis[p‐phenylphosphonic acid] porphyrin (GTUB5). The structure of GTUB5 was characterized using single crystal X-ray diffraction. A narrow band gap of 1.56 eV was extracted from a UV-Vis spectrum of pure GTUB5 crystals, in excellent agreement with the 1.65 eV band gap obtained from DFT calculations. The same band gap was also measured for GTUB5 in DMSO. The proton conductivity of GTUB5 was measured to be 3.00 × 10−6 S cm−1 at 75 °C and 75% relative humidity. The surface area was estimated to be 422 m2 g−1 from grand canonical Monte Carlo simulations. XRD showed that GTUB5 is thermally stable under relative humidities of up to 90% at 90 °C. These findings pave the way for a new family of organic, microporous, and semiconducting materials with high surface areas and high thermal stabilities., Research in hydrogen-bonded organic frameworks (HOFs) has gained interest in recent years due to their facile design and synthesis but no semiconducting HOF has been reported to date. Here the authors report a thermally stable and proton-conductive organic semiconductor based on a porphyrin HOF.

Natural methane hydrates are estimated to be the largest source of unexploited hydrocarbon fuel. The ideal conditions for methane hydrate formation are low temperatures and high pressures. On the other hand, recent experimental studies suggest that porous materials, thanks to their confinement effects, can enable methane hydrate formation at milder conditions, although there has not been a consensus on this. A number of studies have investigated methane hydrate growth in confinement by employing molecular simulations; however, these were carried out at either very high pressures or very low temperatures. Therefore, the effects of confinement on methane hydrate growth at milder conditions have not yet been elaborated by molecular simulations. In order to address this, we carried out a systematic study by performing molecular dynamics (MD) simulations of methane water systems. Using a direct phase coexistence approach, microsecond-scale MD simulations in the isobaric-isothermal (NPT) ensemble were performed in order to study the behavior of methane hydrates in the bulk and in confined nanospaces of hydroxylated silica pores at external pressures ranging from 1 to 100 bar and a simulation temperature corresponding to a 2 °C experimental temperature. We validated the combination of the TIP4P/ice water and TraPPE-UA methane models in order to correctly predict the behavior of methane hydrates in accordance to their phase equilibria. We also demonstrated that the dispersion corrections applied to short-range interactions lead to artificially induced hydrate growth. We observed that in the confinement of a hydroxylated silica pore, a convex-shaped methane nanobuble forms, and methane hydrate growth primarily takes place in the center of the pore rather than the surfaces where a thin water layer exists. Most importantly, our study showed that in the nanopores methane hydrate growth can indeed take place at pressures which would be too low for the growth of methane hydrates in the bulk.

Herein, we report on the synthesis of a microporous, three-dimensional phosphonate metal-organic framework (MOF) with the composition Cu 3 (H 5 -MTPPA) 2 ·2 NMP (H 8 -MTPPA = methane tetra- p -phenylphosphonic acid and NMP = N-methyl-2-pyrrolidone). This MOF, termed TUB1, has a unique one-dimensional inorganic building unit composed of square planar and distorted trigonal bipyramidal copper atoms. It possesses a (calculated) BET surface area of 766.2 m 2 /g after removal of the solvents from the voids. The Tauc plot for TUB1 yields indirect and direct band gaps of 2.4 eV and 2.7 eV, respectively. DFT calculations reveal the existence of two spin-dependent gaps of 2.60 eV and 0.48 eV for the alpha and beta spins, respectively, with the lowest unoccupied crystal orbital for both gaps predominantly residing on the square planar copper atoms. The projected density of states suggests that the presence of the square planar copper atoms reduces the overall band gap of TUB1, as the beta-gap for the trigonal bipyramidal copper atoms is 3.72 eV.

Herein, we report on the synthesis of a microporous, three-dimensional phosphonate metal-organic framework (MOF) of the composition Cu3(H5-MTPPA)2·2 NMP (H8-MTPPA = methane tetra-p-phenylphosphonic acid and NMP = N-methyl-2-pyrrolidone). This MOF, termed TUB1, has a unique one-dimensional inorganic building unit composed of square planar and distorted trigonal bipyramidal copper atoms. It possesses a (calculated) BET surface area of 766.2 m2/g after removal of the solvents from the voids. The Tauc plot for TUB1 yields indirect and direct band gaps of 2.4 eV and 2.7 eV, respectively. DFT calculations reveal the existence of two spin-dependent gaps of 2.60 eV and 0.48 eV for the alpha and beta spins, respectively, with the lowest unoccupied crystal orbital for both gaps predominantly residing on the square planar copper atoms. The projected density of states suggests that the presence of the square planar copper atoms reduces the overall band gap of TUB1, as the beta-gap for the trigonal bipyramidal copper atoms is 3.72 eV.

Porous graphene membranes emerged as promising alternatives for gas separation applications due to their atomic thickness enabling ultra-high permeance, but suffer from low gas selectivity. Whereas decreasing the pore size below 3 nm is expected to increase the gas selectivity due to molecular sieving, it is rather challenging to generate large number of uniform small pores on the graphene surface. Here, we introduce a pore narrowing approach via gold deposition onto porous graphene surface to tune the pore size and thickness of the membrane to achieve large number of small pores. Through our systematic approach, we determined the ideal combination as pore size below 3 nm obtained at the thickness of 100 nm to attain high selectivity and high permeance. The resulting membrane showed a H2/CO2 separation factor of 31.3 at H2 permeance of 2.23x105 GPU (1 GPU = 3.35x10-10 mol s-1 m-2 Pa-1), which is the highest value reported to date in the 105 GPU permeance range. This result is explained by comparing the predicted binding energies of gas molecules with the Au surface, -5.3 vs -21 kJ mol-1 for H2 and CO2, respectively, increased surface-gas interactions and molecular sieving effect with decreasing pore size.

The dehydration of bioalcohols is considered one of the major factors contributing to the cost of biofuel production. In this study, liquid phase separation of water from methanol and ethanol in a siliceous MFI pervaporation membrane was studied by performing concentration gradient driven molecular dynamic (CGD-MD) simulations. CGD-MD simulations work by imposing a higher concentration in the feed side and a lower concentration in the permeate side of the membrane. This creates a concentration gradient across the membrane that facilitates the diffusion of molecules from the feed to the permeate side, mimicking the experimental pervaporation membrane set up. Fluxes of methanol, ethanol and water were calculated in single component permeation simulations and in equimolar methanol–water and ethanol–water mixture separation simulations. It was found that water formed hydrogen bonds with the silanol (Si-OH) groups on the external surface of the MFI and did not enter the membrane in the single component permeation simulation. While this may suggest that MFI can be used to effectively dehydrate bioalcohols, our simulations showed that water permeated through the MFI membrane when it was in a mixture with either methanol or ethanol. Furthermore, in the alcohol-water mixture simulations, the fluxes of methanol and ethanol were significantly lower than that of expected based on their single component fluxes. A detailed analysis of hydrogen bonding in the alcohol-water mixture separation simulations revealed that water preferred making hydrogen bonds with methanol and ethanol rather than with the silanol groups. This resulted in drifting of water molecules along with permeating alcohol molecules in to the MFI membrane in mixture simulations, while slowing the permeation of methanol and ethanol fluxes. The hydrogen bonding between water and alcohol molecules indicates that it may not be possible to achieve complete alcohol selectivity even if defect-free membranes were manufactured; however, our findings also hint at the possibility of functionalizing membrane surfaces with chemical groups that will overcome water-alcohol hydrogen bonding and retain water molecules in order to approach complete selectivity.

The intercalation of non-aqueous fluids in the nanopores of organic and inorganic materials is of significant interest, particularly in the energy science community. Recently, XRD and computational modeling results have shown that structural F- for OH- substitution in layered silicates makes them more hydrophobic. Here, we use Grand Canonical Molecular Dynamics (GCMD) calculations to investigate how increasing the F-/(F-+OH-) ratio of a prototypical layered silicate (the smectite Na-hectorite) impacts the intercalation behavior of CO2 and H2O at elevated temperature and pressure. At the conditions of this study (T = 323 K, P = 90 bar, water-saturated CO2), increasing F- for OH- substitution causes decreasing total CO2+H2O intercalation, increasing CO2/(CO2+H2O) ratios in the interlayer galleries, and an increasing energy barrier to CO2 and H2O intercalation. CO2 intercalation is greatest at monolayer basal spacings, and the results support the idea that with Na+ as the exchangeable cation the interlayers must be propped open by some H2O molecules to allow CO2 to enter the interlayer galleries. The computed immersion energies suggest that the bilayer or a more expanded structure is the stable state under these conditions, in agreement with experimental results, and that the basal spacings of the minimum energy 2L structures increase with increasing F- for OH- substitution. These results are consistent with a wide range of experimental data for smectites at ambient conditions and elevated pressures and temperatures and suggest that F- for OH- substitution in conjunction with reduced structural charge and exchange with large, low charge cations may increase the ability of smectite minerals to incorporate hydrophobic species such as CH4, CO2, H2, and other organic compounds.

Herein, the design and synthesis of a highly photoluminescent and electrically conductive metal–organic framework [Zn{Cu‐p‐H6TPPA}]⋅2 [(CH3)2NH] (designated as GTUB3), which is constructed using the 5,10,15,20‐tetrakis [p‐phenylphosphonic acid] porphyrin (p‐H8TPPA) organic linker, is reported. The bandgap of GTUB3 is measured to be 1.45 and 1.48 eV using diffuse reflectance spectroscopy and photoluminescence (PL) spectroscopy, respectively. The PL decay measurement yields a charge carrier lifetime of 40.6 ns. Impedance and DC measurements yield average electrical conductivities of 0.03 and 4 S m−1, respectively, making GTUB3 a rare example of an electrically conductive 3D metal–organic framework. Thermogravimetric analysis reveals that the organic components of GTUB3 are stable up to 400 °C. Finally, its specific surface area and pore volume are calculated to be 622 m2 g−1 and 0.43 cm3 g−1, respectively, using grand canonical Monte Carlo. Owing to its porosity and high electrical conductivity, GTUB3 may be used as a low‐cost electrode material in next generation of supercapacitors, while its low bandgap and high photoluminescence make it a promising material for optoelectronic applications.

On account of its nonbiodegradable nature and persistence in the environment, perfluorooctanoic acid (PFOA) accumulates in water resources and poses serious environmental issues in many parts of the world. Here, we present the development of two fluorine-rich calix[4]arene-based porous polymers

We report the first one-dimensional tubular metal-organic framework (MOF) [Ni(Cu-H6TPPA)]∙2DMA (H8TPPA = 5,10,15,20-tetrakis[p-phenylphosphonic acid] porphyrin) in the literature. The structure of this MOF, known as GTUB4, was solved using single crystal X-ray diffraction and its surface area was calculated to be 1102 m2/g, making it the phosphonate MOF with the highest reported surface area. GTUB4 also possesses a narrow indirect band gap of 1.9 eV and a direct band gap of 2.16 eV, making it a semiconducting MOF. Thermogravimetric analysis of GTUB4 suggests that it is thermally stable up to 400°C. Owing to its high surface area, low band gap, and thermal stability, GTUB4 could find applications as electrodes in supercapacitors.

International audience; The intercalation of H2O, CO2, and other fluid species in expandable clay minerals (smectites) may play a significant role in controlling the behavior of these species in geological C-sequestration and enhanced petroleum production and has been the subject of intensive study in recent years. This paper reports the results of a computational study of the effects of the properties of the charge balancing, exchangeable cations on H2O and CO2 intercalation in the smectite mineral, hectorite, in equilibrium with an H2O-saturated supercritical CO2 fluid under reservoir conditions using Grand Canonical Molecular Dynamics (GCMD) methods. The results show that the intercalation behavior is greatly different with cations with relatively low hydration energies and high affinities for CO2 (here Cs+) than with cations with higher hydration energies (here Ca2+). With Cs+, CO2 intercalation occurs in a 1-layer structure and does not require H2O intercalation, whereas with Ca2+ the presence of a sub-monolayer of H2O is required for CO2 intercalation. The computational results provide detailed structural, dynamical and energetic insight into the differences in intercalation behavior and are in excellent agreement with in situ experimental XRD, IR, quartz crystal microbalance, and NMR results for smectite materials obtained under reservoir conditions.

The adsorptive removal of atrazine, an agricultural herbicide, from water by three water stable MOFs, ZIF-8, UiO-66, and UiO-67, and a commercial activated carbon, F400, was investigated. UiO-67, ZIF-8, and F400 were found to remove up to 98% of the atrazine from water, whereas UiO-66 is found to be ineffective. In an exceptional performance compared to the other adsorbents considered in our study, UiO-67 removed 98% of atrazine from water within only 2 min, whereas ZIF-8 and F400 took over 40 and 50 min, respectively, to remove the same amount of atrazine. Upon regeneration of UiO-67, minimal loss of adsorption capacity was observed, affirming its effective use for atrazine removal from water.

International audience; In situ XRD and NMR experiments combined with molecular dynamics simulations using the grand canonical ensemble (GCMD) show that cation size, charge and solvation energy play critical roles in determining the interlayer expansion of smectite clay minerals when exposed to dry supercritical CO2 under conditions relevant to the earth’s upper crust, petroleum reservoirs, and geological CO2 sequestration conditions (323 K and 90 bar). The GCMD results show that the smectite mineral, hectorite, containing interlayer alkali and alkaline earth cations with relatively small ionic radii and high solvation and hydration energies (e.g., Li+, Na+ Mg2+, and Ca2+) does not intercalate dry CO2 and that the fully collapsed interlayer structure is the energetically most stable configuration. With increasing cation size and decreasing cation solvation energy, the energy barrier to CO2 intercalation decreases. With K+, Rb+, Cs+, Sr2+, and Ba2+ the monolayer structure is the stable configuration, and CO2 should spontaneously enter the interlayer. With Cs+ there is not even an energy barrier for CO2 intercalation, in agreement with the experimental XRD and NMR results that show clay layer expansion and CO2 incorporation. The number of intercalated CO2 molecules decreases with increasing size of the alkali cation but does not vary with ion size for the alkaline earth cations. 13C NMR spectroscopy and the GCMD simulations show that the average orientation of the intercalated CO2 molecules is with their O-C-O axes parallel to the basal clay surface and that they undergo a combination of rapid rotation about an axis perpendicular to the main molecular axis and wobbling motion with respect to the basal surface. Incorporation of CO2 in the interlayer decreases the coordination of Cs+ by the oxygen atoms of the basal surfaces, which is compensated by CO2 molecules entering their solvation shell, as predicted based on previously published NMR results. The GCMD simulations show that the strength of the interaction between the exchangeable cation and the clay structure dominates the intercalation energetics in dry scCO2. With relatively small cations, the cation-clay interactions outcompete cation solvation by CO2 molecules. The computed residence times for coordination among of interlayer species are consistent with the computed energetics.

We present a systematic computational study which provides a plausible route to control the rotation of organic linkers in isoreticular metal–organic frameworks (IRMOF) by using an external electric field in order to manipulate the diffusion of molecules in nanopores. We achieve this by halogenating the organic linkers of IRMOF-1 and IRMOF-7 to create permanent dipole moments on the linkers, hence making them responsive to changes in the strength and direction of an electric field. More importantly we show that by varying the ligand size and the halogen type, number and substitution positions, the strength of the electric field required to control the rotation of linkers can be reduced significantly. Cl substitution is most effective in making the organic linkers electric field responsive since a greater dipole moment is created compared to those obtained by F or Br substitution. Cl substitution of a larger organic linker, i.e. 1,4-naphthalenedicarboxylate (IRMOF-7) rather than 1,4-benzenedicarboxylate (IRMOF-1), results in a greater dipole moment and reduces the electric field strength required for the rotation of the ligand. Furthermore, double Cl substitution and the optimization of the Cl substitution positions enable controlled rotation of the IRMOF-7 linkers with an electric field strength as low as 0.5 V nm−1. Finally, using the electric field induced rotation of organic linkers we show that it is possible to enhance the diffusion of methane molecules in a chosen direction while limiting their mobility in other directions. Our study hints at the potential of using MOFs for flow control in nanofluidic systems.

Carbamazepine is a persistent contaminant detected in surface and ground waters. In this study we present the adsorptive removal of carbamazepine from water in the metal–organic frameworks UiO-66 and UiO-67 in comparison with a commercial activated carbon F400. While UiO-66 was ineffective in removing carbamazepine, UiO-67 showed superior performance by removing 95% of carbamazepine from a 100 mg L–1 aqueous carbamazepine solution in just 2 min. In contrast, it took F400 more than an hour to remove 88% of the carbamazepine under the same conditions. We further show that UiO-67 can be regenerated repeatedly with no or negligible carbamazepine removal capacity loss, which demonstrates its potential as a durable and promising adsorbent that can be used for the removal of carbamazepine from water.

Layered aluminosilicates play a dominant role in the mechanical and gas storage properties of the subsurface, are used in diverse industrial applications, and serve as model materials for understanding solvent–ion-support systems. Although expansion in the presence of H2O is well-known to be systematically correlated with the hydration free energy of the interlayer cation, particularly in environments dominated by nonpolar solvents (i.e., CO2), uptake into the interlayer is not well-understood. Using novel high-pressure capabilities, we investigated the interaction of dry supercritical CO2 with Na-, NH4-, and Cs-saturated montmorillonite, comparing results with predictions from molecular dynamics simulations. Despite the known trend in H2O and that cation solvation energies in CO2 suggest a stronger interaction with Na, both the NH4- and Cs-clays readily absorbed CO2 and expanded, while the Na-clay did not. The apparent inertness of the Na-clay was not due to kinetics, as experiments seeking a stable expa...

Zorlu, Yunus/0000-0003-2811-1872; Worle, Michael/0000-0001-8087-5779; Yucesan, Gundog/0000-0002-5105-7280; Yazaydin, A. Ozgur/0000-0001-8562-723X WOS:000408644100018 We report two novel 3D porous metal-organophosphonate metal organic frameworks (MOFs) [{Cu(4,4'-bpy)(0.5)(1,4-NDPA-H-2)] (1), [{Cu-2(4,4'-bpy)(0.5)}(1,4-NDPA)] (2) and a non-porous [{Cu(4,4'-bpy)}(2,6-NDPA-H-2)] (3) constructed using the structurally rigid 1,4-naphthalenediphosphonic acid (1,4-NDPA-H-4) and 2,6-naphthalenediphosphonic acid (2,6-NDPA-H-4). 1 and 2 exhibit high surface areas obtained using the structurally rigid and short aromatic organophosphonate linkers with copper. The compound 1 has been further analyzed by TGA and Quantum Design PPMS vibrating sample magnetometer. Turkiye Bilimsel ve Teknolojik Arastirma KurumuTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [TUBITAK 212T060]; COST actionEuropean Cooperation in Science and Technology (COST) [TD1304] Financial support by the Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK 212T060) and the COST action TD1304 are gratefully acknowledged.

In this study we propose and computationally demonstrate the concept of electric field controlled molecular gates mounted on the open-metal coordination sites in metal–organic framework (MOF) materials. The MOF-molecular gate complex functions by opening and closing under the effect of an electric field. Our design involves Mg-MOF-74, a MOF with hexagonal channels with open-metal coordination sites at each corner, and a multifunctional gate molecule with permanent dipole which anchors itself on the host MOF material and responds to changes in the direction of an electric field by rotating around its backbone which acts as an axle. By carrying out density functional theory (DFT) calculations and molecular dynamics (MD) simulations we show that the MOF-molecular gate complex can be switched between two stable configurations, open and closed, by turning on and off an external electric field. We further show that the molecular gate can be controlled to block or allow the diffusion of methane molecules through the channels of the MOF like a nanoscale butterfly valve. Electric field controlled molecular gates mounted on MOFs can pave the way for new molecular machines and nanodevices which can store, deliver or select molecules on demand and with atomic precision.

Membrane-based separation technologies offer a cost-effective alternative to many energy-intensive gas separation processes, such as distillation. Mixed matrix membranes (MMMs) composed of polymers and metal-organic frameworks (MOFs) have attracted a great deal of attention for being promising systems to manufacture durable and highly selective membranes with high gas fluxes and high selectivities. Therefore, understanding gas transport through these MMMs is of significant importance. There has been longstanding speculation that the gas diffusion behavior at the interface formed between the polymer matrix and MOF particles would strongly affect the global performance of the MMMs due to the potential presence of nonselective voids or other defects. To shed more light on this paradigm, we have performed microsecond long concentration gradient-driven molecular dynamics (CGD-MD) simulations that deliver an unprecedented microscopic picture of the transport of H-2 and CH4 as single components and as a mixture in all regions of the PIM-1/ZIF-8 membrane, including the polymer/MOF interface. The fluxes of the permeating gases are computed and the impact of the polymer/MOF interface on the H-2/CH4 permselectivity of the composite membrane is clearly revealed. Specifically, we show that the poor compatibility between PIM-1 and ZIF-8, which manifests itself by the presence of nonselective void spaces at their interface, results in a decrease of the H-2/CH4 permselectivity for the corresponding composite membrane as compared to the performances simulated for PIM-1 and ZIF-8 individually. We demonstrate that CGD-MD simulations based on an accurate atomistic description of the polymer/MOF composite is a powerful tool for characterization and understanding of gas transport and separation mechanisms in MMMs.

A new family of porous metal-organic frameworks (MOFs), namely alkali phosphonate MOFs, is reported. [Na2 Cu(H4 TPPA)]⋅(NH2 (CH3 )2 )2 (GTUB-1) was synthesized using the tetratopic 5,10,15,20-tetrakis[p-phenylphosphonic acid] porphyrin (H8 -TPPA) linker with planar X-shaped geometrical core. GTUB-1 is composed of rectangular void channels with BET surface area of 697 m2 g-1 . GTUB-1 exhibits exceptional thermal stability. The toxicity analysis of the (H8 -TPPA) linker indicates that it is well tolerated by an intestinal cell line, suggesting its suitability for creating phosphonate MOFs for biological applications.

The interactions among fluid species such as H2O, CO2, and CH4 confined in nano- and meso-pores in shales and other rocks is of central concern to understanding the chemical behavior and transport properties of these species in the earth’s subsurface and is of special concern to geological C-sequestration and enhanced production of oil and natural gas. The behavior of CO2, and CH4 are less well understood than that of H2O. This paper presents theresults of a computational modeling study of the partitioning of CO2 and CH4 between bulk fluid and nano- and meso-pores bounded by the common clay mineral montmorillonite. The calculations were done at 323 K and a total fluid pressure of 124 bars using a novel approach (constant reservoir composition molecular dynamics, CRC-MD) that uses bias forces to maintain a constant composition in the fluid external to the pore. This purely MD approach overcomes the difficulties in making stochastic particle insertion-deletion moves in dense fluids encountered in grand canonical Monte Carlo and related hybrid approaches. The results show that both the basal siloxane surfaces and protonated broken edge surfaces of montmorillonite both prefer CO2 relative to CH4 suggesting that methods of enhanced oil and gas production using CO2 will readily displace CH4 from such pores. This preference for CO2 is due to its preferred interaction with the surfaces and extends to approximately 20 Å from them.

Zorlu, Yunus/0000-0003-2811-1872; Yucesan, Gundog/0000-0002-5105-7280; Yazaydin, A. Ozgur/0000-0001-8562-723X; Beckmann, Jens/0000-0002-8548-1821 WOS:000460731900031 PubMed: 30734794 We report a novel metal-organic framework (MOF) based on a cobalt arylphosphonate, namely, [Co-2(H-4-MTPPA)]center dot 3NMP center dot H2O (1.3NM center dot H2O), which was prepared solvothermically from the tetrahedral linker tetraphenylmethane tetrakis-4-phosphonic acid (H-8-MTPPA) and CoSO4 center dot 7H(2)O in N-methyl-2-pyrrolidone (NMP). Compound 1 has the highest porosity (BET surface area of 1034m(2) g(-1)) ever reported for a MOF based on an aryl phosphonic acid linker. The indigo blue crystals of 1.3NMP center dot H2O are composed of edge-shared eight-membered Co2P2O4 rings, and are thermally very stable up to 500 degrees C.

Grain boundaries are an unavoidable microstructural feature in intergrown polycrystalline metal-organic framework (MOF) membranes. They have been suspected to be less size-selective than a MOF’s micropores, resulting in suboptimal separation performances – a speculation recently confirmed by transmission electron microscopy of MOF ZIF-8. Single-crystal membranes, without grain boundaries, should confine mass transport to micropores and reflect the intrinsic selectivity of the porous material. Here, we demonstrate the feasibility of fabricating single-crystal MOF membranes and directly measuring gas permeability through such a membrane using ZIF-8 as an exemplary MOF. Our single-crystal ZIF-8 membranes achieved ideal selectivities up to 28.9, 10.0, 40.1 and 3.6 for gas pairs CO2/N2, CO2/CH4, He/CH4 and CH4/N2 respectively, much higher than or reversely selective to over 20 polycrystalline ZIF-8 membranes, unequivocally proving the non-selectivity of grain boundaries. The permeability trend obtained in single-crystal membranes aligned with a force field that had been validated against multiple empirical adsorption isotherms.

International audience; The interactions among fluid species such as H2O, CO2, and CH4 confined in nano- and meso-pores in shales and other rocks is of central concern to understanding the chemical behavior and transport properties of these species in the earth's subsurface and is of special concern to geological C-sequestration and enhanced production of oil and natural gas. The behavior of CO2, and CH4 is less well understood than that of H2O. This paper presents the results of a computational modeling study of the partitioning of CO2 and CH4 between bulk fluid and nano- and meso-pores bounded by the common clay mineral montmorillonite. The calculations were done at 323 K and a total fluid pressure of 124 bars using a novel approach (constant reservoir composition molecular dynamics, CRC-MD) that uses bias forces to maintain a constant composition in the fluid external to the pore. This purely MD approach overcomes the difficulties in making stochastic particle insertion–deletion moves in dense fluids encountered in grand canonical Monte Carlo and related hybrid approaches. The results show that both the basal siloxane surfaces and protonated broken edge surfaces of montmorillonite both prefer CO2 relative to CH4 suggesting that methods of enhanced oil and gas production using CO2 will readily displace CH4 from such pores. This preference for CO2 is due to its preferred interaction with the surfaces and extends to approximately 20 Å from them.

International audience; Classical molecular dynamics simulations were performed for the smectite clay hectorite with charge-balancing Cs+ cations using a newly developed structural model with a disordered distribution of Li/Mg substitutions in the octahedral sheet and the fully flexible CLAYFF force field. Calculations for systems with interlayer galleries containing 0–19 H2O/Cs+ suggest that the monolayer hydrate is the only stable state at all relative humidities at ambient pressure and temperature, in agreement with experimental results and previous molecular calculations. The basal spacing of this structure is also in good agreement with experimental values. In contrast to previous molecular modeling results, however, the new simulations show that interlayer Cs+ occurs on 2 different inner sphere adsorption sites: above the center of ditrigonal cavities and above Si tetrahedra. Unlike previous simulations, which employed a rigid clay model and fixed orientations of the structural −OH groups, the present results are obtained for an unconstrained clay substrate structure, where the structural -OH groups are able to assume various orientations, including being nearly parallel to the clay layers. This flexibility allows the Cs+ ions to approach the surface more closely above the centers of the hexagonal rings. In this structural arrangement, Cs+ ions are not hydrated by the H2O molecules which share the same interlayer plane, but rather by the H2O molecules coordinated to the opposite surface. In contrast, on the external basal surface, a significant fraction of H2O molecules are adsorbed above the centers of ditrigonal cavities adjacent to adsorbed Cs+ ions. For these H2O molecules, both H(H2O) atoms coordinate and H-bond to Ob surface oxygen atoms. The mean residence times for the Cs+ - H2O, Cs+ - Ob, and H2O - Ob coordination pairs show that Cs+ ions are more strongly coordinated with Ob atoms than H2O molecules. This result is the opposite of the behavior in Ca-hectorite, due to the much smaller hydration energy of Cs+ compared to that of Ca2+.

Variable-temperature X-ray diffraction and 2H NMR spectroscopy of the smectite mineral, hectorite, containing interlayer Na+, K+, Cs+, Mg2+, Ca2+, Sr2+, and Pb2+ equilibrated at 43% relative humidity (RH) and mixed with 2H2O to form a paste provide a comprehensive picture of the structural environments and dynamics of interlayer 2H2O and the relationships of these properties to interlayer hydration state, the hydration energy and polarizability of the cation, temperature, and the formation of ice-1h in the interparticle pores. The variation in basal spacing shown by the XRD data correlates well with the 2H NMR behavior, and the XRD data show for the first time in hectorites that crystallization of interparticle ice-1h causes a decrease in the interlayer spacing, likely due to removal of interlayer 2H2O. The variation of the 2H NMR behavior of all the samples with decreasing temperature reflects decreasing frequencies of motion for the rotation of the 2H2O molecules around their dipoles, reorientation of t...

A conductive phosphonate metal–organic framework (MOF), [{Cu(H2O)}(2,6‐NDPA)0.5] (NDPA = naphthalenediphosphonic acid), which contains a 2D inorganic building unit (IBU) comprised of a continuous edge‐sharing sheet of copper phosphonate polyhedra is reported. The 2D IBUs are connected to each other via polyaromatic 2,6‐NDPA's, forming a 3D pillared‐layered MOF structure. This MOF, known as TUB40, has a narrow band gap of 1.42 eV, a record high average electrical conductance of 2 × 102 S m−1 at room temperature based on single‐crystal conductivity measurements, and an electrical conductance of 142 S m−1 based on a pellet measurement. Density functional theory (DFT) calculations reveal that the conductivity is due to an excitation from the highest occupied molecular orbital on the naphthalene‐building unit to the lowest unoccupied molecular orbital on the copper atoms. Temperature‐dependent magnetization measurements show that the copper atoms are antiferromagnetically coupled at very low temperatures, which is also confirmed by the DFT calculations. Due to its high conductance and thermal/chemical stability, TUB40 may prove useful as an electrode material in supercapacitors.

A ‘lawn-like’ distribution of interconnected zinc oxide nanorods, coated with a metal-organic compound based on zeolitic imidazolate frameworks – ZIF-8 was prepared on microstructured thin-film interdigitated Pt-electrodes forming ZnO@ZIF-8 core-shell heterostructures and investigated as gas sensor material in relation to the identical, but uncovered pure ZnO-layer. This composite combines the gas sensing properties of the metal oxide ZnO with the specific properties of the metal-organic framework material which result in a distinct change of the conditions of gas sensing at the ZnO/ZIF-8-interface. Herein, for the first time it is reported that as prepared ZnO@ZIF-8 composite material is an attractive choice to reduce the cross-sensitivity to water vapour (humidity) in the gas sensing response towards propene and ethene. The observed change of sensitivity in relation to uncovered ZnO is discussed to be due to (i) the specific interaction of the ZIF-8 at the interface with the ZnO taking influence on the gas reaction processes, (ii) the diffusivity of ZIF-8 for the different gas components, and (iii) the sorption behaviour of the used gases at the ZnO interface and inside the ZIF-8 material.

Layered aluminosilicates play a dominant role in the mechanical and gas storage properties of the subsurface, are used in diverse industrial applications, and serve as model materials for understanding solvent-ion-support systems. Although expansion in the presence of H

In this study, we introduce a new non-equilibrium molecular dynamics simulation method to perform simulations of concentration driven membrane permeation processes. The methodology is based on the application of a non-conservative bias force controlling the concentration of species at the inlet and outlet of a membrane. We demonstrate our method for pure methane, ethane and ethylene permeation and for ethane/ethylene separation through a flexible ZIF-8 membrane. Results show that a stationary concentration gradient is maintained across the membrane, realistically simulating an out-of-equilibrium diffusive process, and the computed permeabilities and selectivity are in good agreement with experimental results., Chemical Science, 8 (5), ISSN:2041-6520, ISSN:2041-6539

This work was supported by The Scientific and Technological Research Council of Turkey TUBITAK under the contract No. 214M397. For work at Northwestern, J. T. H. and O. K. F. and gratefully acknowledge support from the Dept. of Energy, Office of Science, Basic Energy Science through grant DE-FG02-08ER155967. Bridging ligand replacement in zeolitic imidazolate frameworks, ZIF-8 and ZIF-67, by 1,2,3-triazole was investigated. A complete substitution of 2-methylimidazole by 1,2,3-triazole resulted in a topological transformation of the parent framework from a sodalite (SOD) network to a diamond (DIA) network. Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) 214M397 Dept. of Energy, Office of Science, Basic Energy Science DE-FG02-08ER155967

Separation of H2 in a ZIF‐8 membrane from a syngas mixture composed of CO2, H2, and N2 at 300 K and 35 atm is simulated with the concentration gradient driven molecular dynamics (CGD‐MD) method. Steady‐state fluxes are computed to predict the H2 selectivity of the ZIF‐8 membrane using four different flexible force fields developed for ZIF‐8. The permselectivities predicted by the CGD‐MD method are compared with those obtained from the grand canonical Monte Carlo+equilibrium molecular dynamics (GCMC+EMD) approach, which is based on the solution‐diffusion model and widely used to predict permselectivities for mixture separations. The permselectivities obtained by using the CGD‐MD method accurately predict that ZIF‐8 is H2 selective over CO2 and N2. On the other hand, permselectivities predicted with the GCMC+EMD approach are found to be incorrect, that is, ZIF‐8 not selective for H2. The study suggests that a reliable non‐equilibrium molecular dynamics approach should be employed in order to obtain accurate predictions for the permselectivity of a membrane for a multicomponent mixture separation process which happens at moderate or high pressure conditions.

Correction for ‘A cobalt arylphosphonate MOF – superior stability, sorption and magnetism’ by Yunus Zorlu et al., Chem. Commun., 2019, DOI: 10.1039/c8cc09655d.

In this work we computationally studied eight Metal–Organic Frameworks (MOFs) which showed or is expected to have ultrahigh surface areas (NU-100, NU-108, NU-109, NU-110, MOF-180, MOF-200, MOF-210 and MOF-399). Successful activation for some of these MOFs have not been possible since their synthesis, and for most of them experimental surface area, pore volume and hydrogen and methane adsorption data do not exist. Geometric surface areas and pore volumes of these eight MOFs were calculated, and in order to assess their hydrogen and methane storage capacities adsorption isotherms were computed using grand canonical Monte Carlo simulations. Our results reveal that if it can be successfully activated MOF-399 will have the highest gravimetric surface area and pore volume (exceeding 7100 m2/g and 7.55 cm3/g) among all MOFs synthesized until now. Thanks to its substantially large pore volume MOF-399 is predicted to store much more hydrogen and methane in gravimetric terms compared to other ultrahigh surface area MOFs.

Amorphous calcium carbonate (ACC) is a critical transient phase in the inorganic precipitation of CaCO3 and in biomineralization. The calcium carbonate crystallization pathway is thought to involve dehydration of more hydrated ACC to less hydrated ACC followed by the formation of anhydrous ACC. We present here computational studies of the transition of a hydrated ACC with a H2O/CaCO3 ratio of 1.0 to anhydrous ACC. During dehydration, ACC undergoes reorganization to a more ordered structure with a significant increase in density. The computed density of anhydrous ACC is similar to that of calcite, the stable crystalline phase. Compared to the crystalline CaCO3 phases, calcite, vaterite, and aragonite, the computed local structure of anhydrous ACC is most-similar to those of calcite and vaterite, but the overall structure is not well described by either. The strong hydrogen bond interaction between the carbonate ions and water molecules plays a crucial role in stabilizing the less hydrated ACC compositions compared to the more hydrated ones, leading to a progressively increasing hydration energy with decreasing water content.