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.

https://img62.chem17.com/1/20140715/635410323829886334962.pdf

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

A system and method for reducing nitrous oxides in diesel exhaust with hydrogen and carbon monoxide over a palladium based catalyst. The catalyst comprises a compound represented by the formula: X% Pd - Y% V2O5 / Z, where X is between about 0.1 to about 2.0, Y is between about 0.1 to about 7.0, and Z is an oxide support.

Selective catalyst reduction of nitrogen oxides with hydrogen

Binary mixtures can be separated into two high-purity products by a new pressure swing adsorption (PSA) cycle. The product purity depends on the purge/feed ratio of the respective gases in the PSA cycle. The process characteristics of the new PSA cycle, using activated carbon as the sorbent, can be adequately predicted by an equilibrium model.

Separation of binary gas mixture into two high-purity products by a new pressure swing adsorption cycle

Apparent turnover frequency (TOF) rates for the C−NO reaction were calculated on the basis of overall rates measured for three graphite samples with different dimensions at various temperatures (500−750 °C) and partial pressures. These TOF rates were rates per edge site on the edges of the crystals. The TOF rates were also determined for one of these graphites for the C−N2O reaction. Temperature breaks on the Arrhenius plots were observed for the C−NO reaction while no such temperature break was observed in TOF rates measured by directly following the etch pit growth rates (using STM). The temperature break phenomenon is attributed to pitting (and the ensuing pit growth) by O atoms dissociated from NO. The TOF rates appeared to be inversely proportional to the basal plane crystal size. This result was attributed to the steps and defects that also contributed significantly to the overall rates.

Kinetics of C−NO and C−N2O Reactions

Gaseous diffusion in porous solids at elevated temperatures.

Although sulfur dioxide is generated in most combustion processes involving carbonaceous fuels, not much attention has been paid to its effect on combustion. However, it has been found that, below 500/sup 0/C, SO/sub 2/ retards the oxidation reaction of carbon by O/sub 2/; and a sulfoxy species was found on the carbon surface which was held responsible for the retardation. In this report, the observation of a prominent transient effect caused by SO/sub 2/ at higher temperatures is presented.

Ralph T. Yang

Papers

Selective catalyst reduction of nitrogen oxides with hydrogen

Separation of binary gas mixture into two high-purity products by a new pressure swing adsorption cycle

Kinetics of C−NO and C−N2O Reactions

Gaseous diffusion in porous solids at elevated temperatures.

Combustion of carbon. Effect of sulfur dioxide