Vanadium redox flow batteries have applications for large-scale electricity storage. This paper reports the influence of carbon structural characteristics of sustainable walnut shell-derived carbons in carbon/polyvinylidene fluoride composite electrodes on vanadium redox reactions. Pyrolysis, gasification, and chemical treatment procedures were used to modify the structural characteristics of carbons. Carbon functional groups were modified by chemical treatment with HNO3, heat treatment with K2CO3, and high-temperature NH3 treatment. Carbon porous structures were characterized using gas adsorption studies. Raman spectroscopy and X-ray diffraction were used to characterize the carbon molecular structure. Functional groups were characterized using X-ray photoelectron spectroscopy, acid/base titrations, temperature-programmed desorption, and Fourier transform infrared spectroscopy. The influence of carbon structure, porosity, and surface functional groups on the redox reactions of vanadium was investigated using cyclic voltammetry and electrical impedance spectroscopy. The VO2+/VO2 + and V2+/V3+ couples had well-defined peaks in cyclic voltammetry, with the former being the most intense, but the V3+/VO2+ couple was not observed for samples carbonized under nitrogen. The results show that V2+/V3+ and VO2+/VO2 + couples observed in cyclic voltammograms were enhanced for carbonization temperatures up to 800 °C. Electrical impedance spectroscopy also showed impedance trends. The electrochemistry results are primarily related to changes in carbon structure and the catalysis of V3+ oxidation by surface functional groups in the carbon structure. The V3+/VO2+ couple was limited by slow kinetics, but it occurs on specific oxygen and nitrogen sites in the carbon structure. The oxidation of V(iii) to V(iv) only occurs on a limited number of surface sites, and the outer-sphere electron transfer to oxidize V(iii) takes place at much more positive potentials. The coulombic, voltage, and energy efficiency of the carbon electrodes were suitable for batteries.

Shale gas from unconventional resources will contribute to meeting the energy demand during the transition to a net-zero carbon economy. In this minireview, the current status of understanding methane adsorption on kerogens and shales is discussed in relation to methane storage capacity. Standard subcritical adsorption studies provide characterization data (micropore volumes, total pore volumes, surface areas, and pore size distributions) for the porous structures of shales and kerogens. However, supercritical methane adsorption measurements under simulated geological conditions are necessary to assess realistic methane adsorption storage capacities. Supercritical methane adsorption on shale and shale components (kerogens and clays) under high pressure and temperature conditions that simulated geological conditions is compared. Kerogen structural characteristics are discussed in relation to supercritical methane isotherms and isobars. The contribution of adsorbed methane gas relative to "free" or compressed gas to the total gas stored in shale is considered. The importance of kerogens in both storage of the adsorbed phase and as the source of methane is highlighted, and the areas where knowledge and understanding are deficient are identified, in particular, the relationship of kerogen type and maturity with supercritical methane adsorption under simulated geological conditions. The competitive adsorption of water on methane capacity is also an area where more detailed studies are necessary. These are challenges to address gaps in the current knowledge and understanding, which require future research.

There is extensive interest in postcombustion flue gas treatment for mitigating CO2 emissions and removal of acid gases. In this study we investigate the adsorption of the main flue gas components (CO2, N-2, SO2, and water vapor) on Filtrasorb 400 activated carbon to understand adsorption characteristics of the main components and competitive adsorption effects. The adsorption isotherms of the pure components of flue gas, CO2 (273.15-318.15 K and 0-50 bar), N-2 (298.15-313.15 K and 0-150 bar), SO2 (273.15-303.15 K and 0-3.6 bar), and water vapor (293.15-303.15 K and 0-41 mbar), were investigated. The isosteric enthalpies of adsorption were determined to be a function of surface excess. The enthalpies at zero surface coverage have the order SO2 > H2O > CO2 > N-2. However, the SO2 isosteric enthalpy decreases with increasing surface excess and is lower than that of water vapor at high surface excess uptake values. The temperature range for CO2 adsorption covers the subcritical to supercritical gas transition. There was no evidence for isosteric enthalpy differences over this temperature range. The adsorption kinetics for SO2 (290.65-303.15 K) and H2O (293.15-303.15 K) adsorption were measured for each isotherm pressure increment. In both cases the adsorption kinetics followed the linear driving force model. The adsorption mechanisms for both SO2 and H2O kinetic trends are discussed in terms of the adsorption mechanisms. The water vapor adsorption kinetics showed a minimum in the region where water molecules form clusters around functional groups, which merge in the pores. The SO2 adsorption kinetics also show a minimum with increasing surface coverage, and this is attributed to dipole-dipole interactions. The activation energies for diffusion of both SO2 and H2O into F400 were very low. Both the N-2 and CO2 adsorption kinetics were too fast to be measured accurately by the gravimetric method used in this study. Ideal adsorbed solution theory (IAST) was used to calculate competitive adsorption of SO2/CO2 and CO2/N-2 from the isotherms of the pure components. The competitive adsorption of CO2/N-2 was investigated by using the integral mass balance (IMB) experimental method, and this was used for validation of the IAST. The results provide an insight into the role of competitive adsorption in the capture of CO2 and SO2 from flue gases by adsorption from both thermodynamic and kinetic perspectives.

The demand for xylenes is projected to increase over the coming decades. The separation of xylene isomers, particularly p- and m -xylenes, is vital for the production of numerous polymers and materials. However, current state-of-the-art separation is based upon fractional crystallisation at 220 K which is highly energy intensive. Here, we report the discrimination of xylene isomers via refinement of the pore size in a series of porous metal–organic frameworks, MFM-300, at sub-angstrom precision leading to the optimal kinetic separation of all three xylene isomers at room temperature. The exceptional performance of MFM-300 for xylene separation is confirmed by dynamic ternary breakthrough experiments. In-depth structural and vibrational investigations using synchrotron X-ray diffraction and terahertz spectroscopy define the underlying host–guest interactions that give rise to the observed selectivity ( p -xylene < o -xylene < m -xylene) and separation factors of 4.6–18 for p- and m -xylenes.

Shale gas is an important hydrocarbon resource in a global context. It has had a significant impact on energy resources in the US, but the worldwide development of this methane resource requires further research to increase the understanding of the relationship of shale structural characteristics to methane storage capacity. In this study a range of gas adsorption, microscopic, mercury injection capillary pressure porosimetry and pycnometry techniques were used to characterize the full range of porosity in a series of shales of different thermal maturity. Supercritical methane adsorption methods for shale under conditions which simulate geological conditions (up to 473 K and 15 MPa) were developed. These methods were used to measure the methane adsorption isotherms of Posidonia shales where the kerogen maturity ranged from immature, through oil window, to gas window. Subcritical methane and carbon dioxide adsorption studies were used for determining pore structure characteristics of the shales. Mercury injection capillary pressure porosimetry was used to characterize the meso and macro porosity of shales. The sum of the CO 2 sorption pore volume at 195 K and mercury injection capillary pressure pore volumes (1093–5.6 nm) were equal to the corresponding total pore volume (< 1093 nm) thereby giving an equation accounting for virtually all the available shale porosity. These measurements allowed quantification of all the available porosity in shales and were used for estimating the contributions of methane stored as ‘free’ compressed gas and as adsorbed gas to overall methane storage capacity of shales. Both the mineral and kerogen components of shale were studied by comparing shale and the corresponding isolated kerogens so that the relative contributions of these components could be assessed. The results show that the methane adsorption characteristics were much higher for the kerogens and represented 35–60% of the total adsorption capacity for the shales used in this study, which had total organic contents in range 5.8–10.9 wt%. Microscopy studies revealed that the pore systems in clay-rich, organic-rich and microfossil-rich parts of shale are very different, and also the importance of the inter-granular organic-mineral interface.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

The development of highly active and durable noble-metal-free electrocatalysts for overall water splitting is a great challenge. Herein, a microdroplet flow reaction is used for ultrafast and continuous synthesis of a nickel metal-organic framework material with 4,4'-bipyridine and phosphonate ligands. A one step pyrolysis of this metal-organic framework to various heat treatment temperatures and hold times at maximum temperature give a range of electrocatalysts, containing crystalline Ni2P nanoparticles dispersed in a porous carbonaceous matrix incorporating relatively high concentrations of both nitrogen and phosphorus derived from the original metaleorganic framework. The Ni2P electrocatalysts inherite the morphology of the metal-organic framework precursor, have a uniform dispersion of Ni2P sites and Brunauer-Emmett-Teller surface areas in the range 558-754 m(2) g(-1). The Ni2P electrocatalysts exhibit excellent catalytic performance for both hydrogen and oxygen evolution reactions in 1.0 M KOH and an electrolyzer using Ni2P electrocatalysts as both cathode and anode generates a current density of 10 mA cm(-2) at a voltage of 1.62 V with superior durability. This facile and scalable synthesis strategy for the rational design of electrocatalysts represents a proof-of-concept with the potential for scale-up for use in practical applications. (C) 2018 Elsevier Ltd. All rights reserved.

Mudstones exert a fundamental control on the flow of both aqueous and nonaqueous fluids in sedimentary basins. Predicting their flow and storage properties requires an understanding of pore size and connectivity, yet there are very few quantitative descriptions of pore systems of mineralogically and texturally well‐characterized mudstones. We use a combination of electron microscopy, mercury injection capillary pressure porosimetry, and CO2 sorption methods to generate a quantitative description of the size distribution, connectivity, and evolution of pore systems in a sequence of Posidonia Shale mudstones buried to 100–180 °C. We place the pore data into a detailed mineralogical, petrographical, and textural context to show that the nature and evolution of porosity and pore systems can be described in terms of associations with clay‐rich, microfossil‐rich, and organic matter‐rich domains, common to many mudstones. Pore size distributions are described by power laws, and pore systems are well connected across the full nanometer‐micrometer spectrum of pore sizes. However, connected networks occur primarily through pores <10 nm radius, with typically 20–40% of total porosity associated with pores with radii < ~3 nm, within both organic matter and the clay matrix. Clay‐rich, microfossil‐rich, and organic matter‐rich domains have distinct pore size distributions which evolve in very different ways with increasing thermal maturity. We suggest that the flow of aqueous and nonaqueous fluids depends not only on the overall connectivity of pores but also the larger‐scale connectivity and wetting state of clay‐rich, microfossil‐rich, and organic matter‐rich domains.

Direct synthesis of the ultrathin and discrete 2D metal organic framework (MOF) nanosheets is extremely challenging. Herein, we present the first facile continuous bottomup strategy for preparing ultrathin (similar to 3 nm) 2D MOF nanosheets with high crystallinity comprising assemblies of a few layers. Unlike conventional solvothermal synthetic methods for 2D MOFs, the weak interlayer interaction in the vertical direction of the 2D materials is restricted under microdroplet flow reaction conditions. The 2D MOF nanosheets with a large lateral area and a few layers thick were directly synthesized by suppressing the lamellar stacking of the nanosheets under the dynamic growth conditions. The 2D MOF nanosheets were characterized by scanning and transmission electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, powder X-ray diffraction, infrared spectroscopy, thermogravimetric analysis, gas adsorption, and light scattering techniques, which were supported by density functional theory (DFT) calculations and molecular simulations. The properties of the "asprepared" 2D MOF nanosheets were compared with the corresponding pristine solvothermal MOF with extended structure perpendicular to the laminar assembly. The ultrathin 2D MOF nanosheets have greater external surface area, resulting in a far higher gas adsorption and colloidal suspensions that exhibit the Tyndall effect. This synthetic methodology for 2D MOF nanosheets has potential for scaleup of materials production.

Nitrogen dioxide (NO2) is a major air pollutant causing significant environmental1,2 and health problems3,4. We report reversible adsorption of NO2 in a robust metal–organic framework. Under ambient conditions, MFM-300(Al) exhibits a reversible NO2 isotherm uptake of 14.1 mmol g−1, and, more importantly, exceptional selective removal of low-concentration NO2 (5,000 to <1 ppm) from gas mixtures. Complementary experiments reveal five types of supramolecular interaction that cooperatively bind both NO2 and N2O4 molecules within MFM-300(Al). We find that the in situ equilibrium 2NO2 ↔ N2O4 within the pores is pressure-independent, whereas ex situ this equilibrium is an exemplary pressure-dependent first-order process. The coexistence of helical monomer–dimer chains of NO2 in MFM-300(Al) could provide a foundation for the fundamental understanding of the chemical properties of guest molecules within porous hosts. This work may pave the way for the development of future capture and conversion technologies. High and reversible nitrogen dioxide (NO2) uptake, and low-concentration NO2 removal from gas mixtures, is observed in a metal–organic framework. The NO2 is bound within the pores by cooperative supramolecular interactions.

Resistant hypertension (RH) is defined as blood pressure (BP) that remains above target levels despite adherence to at least three different antihypertensive medications, typically including a diuretic. Epidemiological studies estimate that RH is increasing in prevalence, and is associated with detrimental health outcomes. The pathophysiology underlying RH is complex, involving multiple, overlapping contributors including activation of the renin-angiotensin aldosterone system and the sympathetic nervous system, volume overload, endothelial dysfunction, behavioural and lifestyle factors. Hypertension guidelines currently recommend specific pharmacotherapy for 1st, 2nd and 3rd-line treatment, however no specific fourth-line pharmacotherapy is provided for those with RH. Rather, five different antihypertensive drug classes are generally suggested as possible alternatives, including: mineralocorticoid receptor antagonists, α1-adrenergic antagonists, α2-adrenergic agonists, β-blockers, and peripheral vasodilators. Each of these drug classes vary in their efficacy, tolerability and safety profile. This review summarises the available data on each of these drug classes as a potential fourth-line drug and reveals a lack of robust clinical evidence for preferred use of most of these classes in the setting of RH. Moreover, there is a lack of direct comparative trials that could assist in identifying a preferred fourth-line pharmacologic approach and in providing evidence for hypertensive guidelines for adequate treatment of RH.

Physisorption drives structural change leading to thermally stable CO chemisorption.

A phosphonate based MOF was synthesized, the structure determined and gas/vapor adsorption characteristics studied.

Porous MFM-202a (MFM = Manchester Framework Material, replacing the NOTT designation) shows an exceptionally high uptake of acetylene, 18.3 mmol g(-1) (47.6 wt %) at 195 K and 1.0 bar, representing the highest value reported to date for a framework material. However, at 293 K and 10 bar C2H6 uptake (9.13 mmol g(-1)) is preferred. Dual-site Langmuir-Freundlich (DSLF)- and Numerical Integration (NI)-based LAST methods have been used to analyze selectivities for C-1 to C-3 hydrocarbons. MFM-202a exhibits broadly hysteretic desorption of acetylene; such behavior is important for practical gas storage since it allows the gas to be adsorbed at high pressure but stored at relatively low pressure. Stepwise uptake and hysteretic release were also observed for adsorption of other unsaturated light hydrocarbons (ethane and propene) in MFM-202a but not for saturated hydrocarbons (methane, ethane, and propane). MFM-202a has been studied by in situ synchrotron X-ray powder diffraction to reveal the possible phase transition of the framework host as a function of gas loading. A comprehensive analysis for the selectivities between these light hydrocarbons has been conducted using both LAST calculation and dual-component mixed-gas adsorption experiments, and excellent agreement between theory and experiment was achieved.

Low and high resolution petrographic studies have been combined with mineralogical, TOC, RockEval and porosity data to investigate controls on the evolution of porosity in stratigraphically equivalent immature, oil-window and gas-window samples from the Lower Toarcian Posidonia Shale formation. A series of 26 samples from three boreholes (Wickensen, Harderode and Haddessen) in the Hils syncline was investigated. The main primary components of the shales are microfossiferous calcite (30-50%), clay minerals (20-30%) and Type II organic matter (TOC = 7-15%, HI = 630-720 mg/gC in immature samples). Characteristic sub-centimetric light and dark lamination reflects rapid changes in the relative supply of these components. Total porosities decrease from 10 to 14% at Ro = 0.5% to 3-5% at Ro = 0.9% and then increase to 9-12% at Ro = 1.45%. These maturity-related porosity changes can be explained by (a) the primary composition of the shales, (b) carbonate diagenesis, (c) compaction and (d) the maturation, micro-migration, local trapping and gasification of heterogeneous organic phases. Calcite undergoes dissolution and reprecipitation reactions throughout the maturation sequence. Pores quantifiable in SEM (>ca. 50 nm) account for 14-25% of total porosity. At Ro = 0.5%, SEM-visible macropores1 are associated mainly with biogenic calcite. At this maturity, clays and organic matter are not visibly porous but nevertheless hold most of the shale porosity. Porosity loss into the oil window reflects (a) compaction, (b) carbonate cementation and (c) perhaps the swelling of kerogen by retained oil. In addition, porosity is occluded by a range of bituminous phases, especially in microfossil macropores and microfractures. In the gas window, mineral-hosted porosity is still the primary form of macroporosity, most commonly observed at the organic-inorganic interface. Increasing porosity into the gas window also coincides with the formation of isolated, spongy and complex meso- and macropores within organic particles, related to thermal cracking and gas generation. This intraorganic porosity is highly heterogeneous: point-counted macroporosity of individual organic particles ranges from 0 to 40%, with 65% of organic particles containing no macropores. We suggest that this reflects the physicochemical heterogeneity of the organic phases plus the variable mechanical protection afforded by the mineral matrix to allow macroporosity to be retained. The development of organic macroporosity cannotalone account for the porosity increase observed from oil to gas window; major contributions also come from the increased volume of organic micro- and meso-porosity, and perhaps by kerogen shrinkage. (C) 2016 Elsevier Ltd. All rights reserved.

Metal-organic frameworks (MOFs) are known to facilitate energy-efficient separations of important industrial chemical feedstocks. Here, we report how a class of green MOFs-namely CD-MOFs-exhibits high shape selectivity toward aromatic hydrocarbons. CD-MOFs, which consist of an extended porous network of γ-cyclodextrins (γ-CDs) and alkali metal cations, can separate a wide range of benzenoid compounds as a result of their relative orientation and packing within the transverse channels formed from linking (γ-CD)6 body-centered cuboids in three dimensions. Adsorption isotherms and liquid-phase chromatographic measurements indicate a retention order of ortho- > meta- > para-xylene. The persistence of this regioselectivity is also observed during the liquid-phase chromatography of the ethyltoluene and cymene regioisomers. In addition, molecular shape-sorting within CD-MOFs facilitates the separation of the industrially relevant BTEX (benzene, toluene, ethylbenzene, and xylene isomers) mixture. The high resolution and large separation factors exhibited by CD-MOFs for benzene and these alkylaromatics provide an efficient, reliable, and green alternative to current isolation protocols. Furthermore, the isolation of the regioisomers of (i) ethyltoluene and (ii) cymene, together with the purification of (iii) cumene from its major impurities (benzene, n-propylbenzene, and diisopropylbenzene) highlight the specificity of the shape selectivity exhibited by CD-MOFs. Grand canonical Monte Carlo simulations and single component static vapor adsorption isotherms and kinetics reveal the origin of the shape selectivity and provide insight into the capability of CD-MOFs to serve as versatile separation platforms derived from renewable sources.

We report two isoreticular 3D peptide-based porous frameworks formed by coordination of the tripeptides Gly-L-His-Gly and Gly-L-His-L-Lys to Cu-II which display sponge-like behaviour. These porous materials undergo structural collapse upon evacuation that can be reversed by exposure to water vapour, which permits recovery of the original open channel structure. This is further confirmed by sorption studies that reveal that both solids exhibit selective sorption of H2O while CO2 adsorption does not result in recovery of the original structures. We also show how the pendant aliphatic amine chains, present in the framework from the introduction of the lysine amino acid in the peptidic backbone, can be post-synthetically modified to produce urea-functionalised networks by following methodologies typically used for metal-organic frameworks built from more rigid classical linkers.