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

A study of adsorption of thiophenic sulfur compounds, thiophene (T), benzothiopnene (BT), and dibenzothiophene (DBT), in normal alkane solvents (n-octane and hexadecane) on NaY and 13X zeolites was performed. Adsorption isotherms of pure-component n-octane, hexadecane, and T from the vapor phase were also measured. Analysis of the heats of adsorption (including differential and integral heats) calculated by using the Clausius−Clapeyron equation were in agreement with the results obtained by Ng et al. using flow calorimetry for the same systems. The simple theory estimating the relationship between the heat of adsorption from liquid solution and that from the vapor phase proposed in our previous work was tested using the experimental data. The enthalpies of solvation for T−octane and T−hexadecane were also used to validate the simple theory. The theoretical predictions were in close agreement with experiments. The simple theory is easy to use and can explain and provide insight into adsorption from liquid ...

Heats of Adsorption from Liquid Solutions and from Pure Vapor Phase: Adsorption of Thiophenic Compounds on NaY and 13X Zeolites

CO2 capture (including direct air capture) and natural gas desulfurization of amine-grafted hierarchical bimodal silica

Pillared interlayered clays (PILC), or pillared clays, are two-dimensional layer materials prepared by exchanging the charge-compensating cations (e.g. Na+, K+ and Ca2+) between the swelling phyllosilicate clay layers with larger inorganic hydroxy cations, which are polymeric or oligomeric hydroxy metal cations formed by hydrolysis of metal salts. Upon heating, the metal hydroxy cations undergo dehydration and dehydroxylation, forming stable metal oxide clusters which act as pillars keeping the silicate layers separated and creating interlayer spacing (gallery spaces) of molecular dimensions. Pillared clay development started in the mid 1950s by Barrer and co-workers1,2 who synthesized high surface area materials by pillaring montmorillonite clay with cations of N(CH3)4 and N(C2H5)4. However, these materials have low thermal and hydrothermal stabilities i.e., up to ca. 250°C for the decomposition temperature of interlayer cations, and are therefore of limited use as adsorbents and catalysts. Much interest and research have, since the 1970s, been directed toward the synthesis of pillared clays with high thermal and hydrothermal stabilities. The most promising ones for use as adsorbents and catalysts are as follows; Al-PILC3-l8, Zr-PILC4,5,19-23, Cr-PILC6,24-28, Fe-PILC29-35, Ti-PILC36-38, Ni-PILC39 and Si-PILC40-41. The choices of hydroxy cations are not limited to those mentioned; in fact any metal oxide or salt that forms polynuclear species upon hydrolysis42 can be inserted as pillars, and all layered clays of the abundant phyllosilicate family as well as other layered clays can be used as the hosts16,43-49. In order to increase the thermal and hydrothermal stabilities and the catalytic activities of pillared clays, mixed pillars have been synthesized using mixed hydroxycations obtained by isomorphous substitution of mvalent cations (e.g. Ga3+, Ce3+, Fe3+, Cr3+) with Al3+ in the AI polyoxocation12,50-52. In addition, positively charged sol

Pillared Clays and Ion-Exchanged Pillared Clays as Gas Adsorbents and as Catalysts for Selective Catalytic Reduction of No

New directions in sorption technology

A Diffusion Cell Method for Studying Heterogeneous Kinetics in the Chemical Reaction/Diffusion Controlled Region. Kinetics of C + CO2→ 2CO at 1200-1600° C

Ralph T. Yang

Papers

Heats of Adsorption from Liquid Solutions and from Pure Vapor Phase: Adsorption of Thiophenic Compounds on NaY and 13X Zeolites

CO2 capture (including direct air capture) and natural gas desulfurization of amine-grafted hierarchical bimodal silica

Pillared Clays and Ion-Exchanged Pillared Clays as Gas Adsorbents and as Catalysts for Selective Catalytic Reduction of No

New directions in sorption technology

A Diffusion Cell Method for Studying Heterogeneous Kinetics in the Chemical Reaction/Diffusion Controlled Region. Kinetics of C + CO2→ 2CO at 1200-1600° C