Crystalline metal-organic frameworks (MOFs) are formed by reticular synthesis, which creates strong bonds between inorganic and organic units. Careful selection of MOF constituents can yield crystals of ultrahigh porosity and high thermal and chemical stability. These characteristics allow the interior of MOFs to be chemically altered for use in gas separation, gas storage, and catalysis, among other applications. The precision commonly exercised in their chemical modification and the ability to expand their metrics without changing the underlying topology have not been achieved with other solids. MOFs whose chemical composition and shape of building units can be multiply varied within a particular structure already exist and may lead to materials that offer a synergistic combination of properties.

The Chemistry and Applications of Metal-Organic Frameworks

New materials hold the key to fundamental advances in energy conversion and storage, both of which are vital in order to meet the challenge of global warming and the finite nature of fossil fuels. Nanomaterials in particular offer unique properties or combinations of properties as electrodes and electrolytes in a range of energy devices. This review describes some recent developments in the discovery of nanoelectrolytes and nanoelectrodes for lithium batteries, fuel cells and supercapacitors. The advantages and disadvantages of the nanoscale in materials design for such devices are highlighted.

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Nanostructured materials for advanced energy conversion and storage devices

Adsorptive separation is very important in industry. Generally, the process uses porous solid materials such as zeolites, activated carbons, or silica gels as adsorbents. With an ever increasing need for a more efficient, energy-saving, and environmentally benign procedure for gas separation, adsorbents with tailored structures and tunable surface properties must be found. Metal–organic frameworks (MOFs), constructed by metal-containing nodes connected by organic bridges, are such a new type of porous materials. They are promising candidates as adsorbents for gas separations due to their large surface areas, adjustable pore sizes and controllable properties, as well as acceptable thermal stability. This critical review starts with a brief introduction to gas separation and purification based on selective adsorption, followed by a review of gas selective adsorption in rigid and flexible MOFs. Based on possible mechanisms, selective adsorptions observed in MOFs are classified, and primary relationships between adsorption properties and framework features are analyzed. As a specific example of tailor-made MOFs, mesh-adjustable molecular sieves are emphasized and the underlying working mechanism elucidated. In addition to the experimental aspect, theoretical investigations from adsorption equilibrium to diffusion dynamics via molecular simulations are also briefly reviewed. Furthermore, gas separations in MOFs, including the molecular sieving effect, kinetic separation, the quantum sieving effect for H2/D2 separation, and MOF-based membranes are also summarized (227 references).

Selective gas adsorption and separation in metal–organic frameworks

Metal–Organic Frameworks for Separations

Kenji Sumida, David L. Rogow, Jarad A. Mason, Thomas M. McDonald, Eric D. Bloch, Zoey R. Herm, Tae-Hyun Bae, Jeffrey R. Long

Carbon Dioxide Capture in Metal–Organic Frameworks

High-purity coal useful in the production of high-purity carbon is produced by treating coal to remove the impurities therein. The coal, which may be subject to conventional pretreatment processes such as beneficiation processes or the like, digested in a caustic solution to solubilize certain of the impurities in the coal and to chemically react with other impurities to form acid soluble products. The digested coal is then filtered to separate the partially purified coal from the caustic and soluble impurities dissolved therein. The coal is then treated with a mineral acid to dissolve the acid soluble products contained in the coal. Finally, the coal is subjected to a nitric acid treatment to remove metal sulfides. The resultant high-purity carbon contains less than 0.1% by weight ash or metal sulfides.

Process for producing high-purity coal

Fundamental differences in the mechanisms of carbon gasification by steam and by carbon dioxide

Composite sorbents were prepared by depositing molybdenum dioxide on Super A activated carbon. The adsorption isotherms of CH4 and N2 were measured. The adsorption capacities and BET surface areas of these adsorbents decreased with an increase in the amount of MoO2; however, the equilibrium selectivity ratio (CH4/N2) increased significantly. Therefore, an optimum quantity of MoO2 should be used to produce a sorbent with high adsorption capacity and selectivity ratio (CH4/N2). An adsorbent containing 18.2 wt% MoO2 was found to be optimum which showed a CH4/N2 selectivity ratio of 4.25. The selectivity ratio decreased with pressure, and leveled off to about 3 at 12 atm. The separation of a CH4/N2 (50/50) mixture by pressure swing adsorption (PSA) was studied by using an equilibrium model. A new PSA cycle is described by which pipeline quality methane (>90% CH4 purity) could be produced using the composite sorbent at a recovery of 73% and a throughput of 200 L STP/h/kg.

A New Composite Sorbent for Methane-Nitrogen Separation by Adsorption

The tunneling action of group VIII metal particles in catalyzed graphite hydrogenation

Etude de la production d'azote a partir de l'air en utilisant un tamis moleculaire de carbone. Etude du comportement de rupture du processus en comparaison avec l'equilibre d'absorption en general

Ralph T. Yang

Papers

Process for producing high-purity coal

Fundamental differences in the mechanisms of carbon gasification by steam and by carbon dioxide

A New Composite Sorbent for Methane-Nitrogen Separation by Adsorption

The tunneling action of group VIII metal particles in catalyzed graphite hydrogenation

Roll‐up in fixed‐bed, multicomponent adsorption under pore‐diffusion limitation