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

Modeling of fixed-bed columns for gas physical adsorption

An analytical expression for an overall adsoption isotherm was derived which accounts for both lateral interaction of the Bragg-Williams kind and surface heterogeneity via a random distribution of sites described by a uniform distribution of energies. The isotherm reduces to the Langmuir, Fowler and Guggenheim, and Langmuir uniform distribution isotherms when the appropriate limits are taken

Localized adsorption with lateral interaction on random and patchwise heterogeneous surfaces

Evidence for temperature-driven carbon diffusion mechanism of coke deposition on catalysts

Pillared interlayered clay catalysts (PILC) are formed and used in the selective reduction (SCR) of nitrogen oxides (NO x ) in exhaust gases in the presence of ammonia. Cr 2 O 3 -PILC, Fe 2 O 3 PILC, TiO 2 -PILC, ZrO 2 -PILC and Al 2 O 3 -PILC each have considerable activities in the SCR of NO by NH 3 . Forming the catalysts in a bimodal pore structure provides increases poison resistance and increases reaction rates. Doping the catalyst with CeO 2 and/or Ce 2 O 3 can promote increased activities. The PILC SCR catalysts do not oxidize SO 2 to undesirable SO 3 in any detectable amount.

Ralph T. Yang

Papers

Modeling of fixed-bed columns for gas physical adsorption

Localized adsorption with lateral interaction on random and patchwise heterogeneous surfaces

Evidence for temperature-driven carbon diffusion mechanism of coke deposition on catalysts

Pillared interlayered clay catalysts for the selective reduction of nitrogen oxides with ammonia

Adsorption of mixtures of water vapor and hydrocarbons by activated carbon beds: thermodynamic model for adsorption equilibrium and adsorber dynamics.