New materials capable of storing hydrogen at high gravimetric and volumetric densities are required if hydrogen is to be widely employed as a clean alternative to hydrocarbon fuels in cars and other mobile applications. With exceptionally high surface areas and chemically-tunable structures, microporous metal–organic frameworks have recently emerged as some of the most promising candidate materials. In this critical review we provide an overview of the current status of hydrogen storage within such compounds. Particular emphasis is given to the relationships between structural features and the enthalpy of hydrogen adsorption, spectroscopic methods for probing framework–H2 interactions, and strategies for improving storage capacity (188 references).

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Hydrogen storage in metal–organic frameworks

Natural gas hydrates are solid, non-stoichiometric compounds of small gas molecules and water. They form when the constituents come into contact at low temperature and high pressure. The physical properties of these compounds, most notably that they are non-flowing crystalline solids that are denser than typical fluid hydrocarbons and that the gas molecules they contain are effectively compressed, give rise to numerous applications in the broad areas of energy and climate effects. In particular, they have an important bearing on flow assurance and safety issues in oil and gas pipelines, they offer a largely unexploited means of energy recovery and transportation, and they could play a significant role in past and future climate change.

Fundamental principles and applications of natural gas hydrates

Dihydrogen, methane, and carbon dioxide isotherm measurements were performed at 1−85 bar and 77−298 K on the evacuated forms of seven porous covalent organic frameworks (COFs). The uptake behavior and capacity of the COFs is best described by classifying them into three groups based on their structural dimensions and corresponding pore sizes. Group 1 consists of 2D structures with 1D small pores (9 A for each of COF-1 and COF-6), group 2 includes 2D structures with large 1D pores (27, 16, and 32 A for COF-5, COF-8, and COF-10, respectively), and group 3 is comprised of 3D structures with 3D medium-sized pores (12 A for each of COF-102 and COF-103). Group 3 COFs outperform group 1 and 2 COFs, and rival the best metal−organic frameworks and other porous materials in their uptake capacities. This is exemplified by the excess gas uptake of COF-102 at 35 bar (72 mg g−1 at 77 K for hydrogen, 187 mg g−1 at 298 K for methane, and 1180 mg g−1 at 298 K for carbon dioxide), which is similar to the performance of COF...

http://yaghi.berkeley.edu/pdfPublications/Furukawa09.pdf

Storage of Hydrogen, Methane, and Carbon Dioxide in Highly Porous Covalent Organic Frameworks for Clean Energy Applications

To progress from the laboratory to commercial applications, it will be necessary to develop industrially scalable methods to produce large quantities of defect-free graphene. Here we show that high-shear mixing of graphite in suitable stabilizing liquids results in large-scale exfoliation to give dispersions of graphene nanosheets. X-ray photoelectron spectroscopy and Raman spectroscopy show the exfoliated flakes to be unoxidized and free of basal-plane defects. We have developed a simple model that shows exfoliation to occur once the local shear rate exceeds 10(4) s(-1). By fully characterizing the scaling behaviour of the graphene production rate, we show that exfoliation can be achieved in liquid volumes from hundreds of millilitres up to hundreds of litres and beyond. The graphene produced by this method performs well in applications from composites to conductive coatings. This method can be applied to exfoliate BN, MoS2 and a range of other layered crystals.

/pdf/scalable-production-of-large-quantities-of-defect-free-few-2ehr40fw5v.pdf

Scalable production of large quantities of defect-free few-layer graphene by shear exfoliation in liquids

When Szent-Gyorgyi called water the “matrix of life”,1 he was echoing an old sentiment. Paracelsus in the 16th century said that “water was the matrix of the world and of all its creatures.”2 But Paracelsus’s notion of a matrixsan active substance imbued with fecund, life-giving propertiess was quite different from the picture that, until very recently, molecular biologists have tended to hold of water’s role in the chemistry of life. Although acknowledging that liquid water has some unusual and important physical and chemical propertiessits potency as a solvent, its ability to form hydrogen bonds, its amphoteric naturesbiologists have regarded it essentially as the backdrop on which life’s molecular components are arrayed. It used to be common practice, for example, to perform computer simulations of biomolecules in a vacuum. Partly this was because the computational intensity of simulating a polypeptide chain was challenging even without accounting for solvent molecules too, but it also reflected the prevailing notion that water does little more than temper or moderate the basic physicochemical interactions responsible for molecular biology. What Gerstein and Levitt said 9 years ago remains true today: “When scientists publish models of biological molecules in journals, they usually draw their models in bright colors and place them against a plain, black background”.3 Curiously, this neglect of water as an active component of the cell went hand in hand with the assumption that life could not exist without it. That was basically an empirical conclusion derived from our experience of life on Earth: environments without liquid water cannot sustain life, and special strategies are needed to cope with situations in which, because of extremes of either heat or cold, the liquid is scarce.4-6 The recent confirmation that there is at least one world rich in organic molecules on which rivers and perhaps shallow seas or bogs are filled with nonaqueous fluidsthe liquid hydrocarbons of Titan7smight now bring some focus, even urgency, to the question of whether water is indeed a * E-mail: p.ball@nature.com. Philip Ball is a science writer and a consultant editor for Nature, where he worked as an editor for physical sciences for more than 10 years. He holds a Ph.D. in physics from the University of Bristol, where he worked on the statistical mechanics of phase transitions in the liquid state. His book H2O: A Biography of Water (Weidenfeld & Nicolson, 1999) was a survey of the current state of knowledge about the behavior of water in situations ranging from planetary geomorphology to cell biology. He frequently writes about aspects of water science for both the popular and the technical media.

https://www.philipball.co.uk/images/stories/docs/pdf/ChemRev_final.pdf

Water as an Active Constituent in Cell Biology

PREFACE Overview and Historical Perspective Hydrates as a Laboratory Curiosity Hydrates in the Natural Gas Industry Hydrates as an Energy Resource Environmental Aspects of Hydrates Safety Aspects of Hydrates Relationship of This Chapter to Those That Follow Molecular Structures and Similarities to Ice Crystal Structures of Ice Ih and Natural Gas Hydrates Comparison of Properties of Hydrates and Ice The What and the How of Hydrate Structures Hydrate Formation and Dissociation Processes Hydrate Nucleation Hydrate Growth Hydrate Dissociation Estimation Techniques for Phase Equilibria of Natural Gas Hydrates Hydrate Phase Diagrams for Water + Hydrocarbon Systems Three-Phase (LW-H-V) Equilibrium Calculations Quadruple Points and Equilibrium of Three Condensed Phases (LW-H-LHC) Effect of Thermodynamic Inhibitors on Hydrate Formation Two-Phase Equilibrium: Hydrates with One Other Phase Hydrate Enthalpy and Hydration Number from Phase Equilibrium Summary and Relationship to Chapters Which Follow A Statistical Thermodynamic Approach to Hydrate Phase Equilibria Statistical Thermodynamics of Hydrate Equilibria Application of the Method to Analyze Systems of Methane + Ethane + Propane Computer Simulation: Another Microscopic-Macroscopic Bridge Summary Experimental Methods and Measurements of Hydrate Properties Experimental Apparatuses and Methods for Macroscopic Measurements Measurements of the Hydrate Phase Data for Natural Gas Hydrate Phase Equilibria and Thermal Properties Summary and Relationship to Chapters that Follow References Hydrates in the Earth The Paradigm Is Changing from Assessment of Amount to Production of Gas Sediments with Hydrates Typically Have Low Contents of Biogenic Methane Sediment Lithology and Fluid Flow Are Major Controls on Hydrate Deposition Remote Methods Enable an Estimation of the Extent of a Hydrated Reservoir Drilling Logs and/or Coring Provide Improved Assessments of Hydrated Gas Amounts Hydrate Reservoir Models Indicate Key Variables for Methane Production Future Hydrated Gas Production Trends Are from the Permafrost to the Ocean Hydrates Play a Part in Climate Change and Geohazards Summary Hydrates in Production, Processing, and Transportation How Do Hydrate Plugs Form in Industrial Equipment? How Are Hydrate Plug Formations Prevented? How Is a Hydrate Plug Dissociated? Safety and Hydrate Plug Removal Applications to Gas Transport and Storage Summary of Hydrates in Flow Assurance and Transportation APPENDICES INDEX

Clathrate hydrates of natural gases

Thermodynamic, x-ray diffraction, and Raman and nuclear magnetic resonance spectroscopy measurements show that clusters of H2 can be stabilized and stored at low pressures in a sII binary clathrate hydrate. Clusters of H2 molecules occupy small water cages, whereas large water cages are singly occupied by tetrahydrofuran. The presence of this second guest component stabilizes the clathrate at pressures of 5 megapascals at 279.6 kelvin, versus 300 megapascals at 280 kelvin for pure H2 hydrate.

https://science.sciencemag.org/content/sci/306/5695/469.full.pdf

Stable Low-Pressure Hydrogen Clusters Stored in a Binary Clathrate Hydrate

Despite the industrial implications and worldwide abundance of gas hydrates, the formation mechanism of these compounds remains poorly understood. We report direct molecular dynamics simulations of the spontaneous nucleation and growth of methane hydrate. The multiple-microsecond trajectories offer detailed insight into the process of hydrate nucleation. Cooperative organization is observed to lead to methane adsorption onto planar faces of water and the fluctuating formation and dissociation of early hydrate cages. The early cages are mostly face-sharing partial small cages, favoring structure II; however, larger cages subsequently appear as a result of steric constraints and thermodynamic preference for the structure I phase. The resulting structure after nucleation and growth is a combination of the two dominant types of hydrate crystals (structure I and structure II), which are linked by uncommon 5 12 6 3 cages that facilitate structure coexistence without an energetically unfavorable interface.

http://science.sciencemag.org/content/sci/326/5956/1095.full.pdf

Microsecond simulations of spontaneous methane hydrate nucleation and growth.

This paper reports on three-phase equilibrium conditions of hydrates (water-rich liquid, hydrate, and vapor) of carbon dioxide and methane binary mixtures that were investigated in the temperature range of 273-288 K and the pressure range of 1.2-11.0 MPa. The vapor-phase concentrations were measured by a gas chromatograph. The results obtained were in good agreement with previous measurements done by researchers at the University of Michigan who had calculated the carbon dioxide concentration in the vapor phase. The data obtained in this work did not show unusual hydrate phenomena, as reported in a more recent publication by researchers in Hungary.

E. Dendy Sloan

Papers

Clathrate hydrates of natural gases

Fundamental principles and applications of natural gas hydrates

Stable Low-Pressure Hydrogen Clusters Stored in a Binary Clathrate Hydrate

Microsecond simulations of spontaneous methane hydrate nucleation and growth.

Hydrates of carbon dioxide and methane mixtures