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 volumetric apparatus to measure hydrogen adsorption and desorption at room temperature and up to 100 atm has been constructed and studied for accuracy, reproducibility, and stability. The design principles are presented and considerable attention to detail is given to examine the effects of diurnal temperature changes in the manifold and helium adsorption by carbon-based adsorbents during free volume measurement. A heuristic for helium correction is derived from a model with a basis in literature and verified through calculation of adsorbent density. Several materials with well-known hydrogen capacities are studied to examine reproducibility. The microporous carbon AX-21 is studied to examine the effects of pressure step size and approach to equilibrium caused by gas mixing and the Joule-Thomson effect. Hydrogen spillover on a hybrid material, Pt on templated carbon, is examined for several loadings of metal. Kinetics of both physisorption and spillover are compared via the diffusion time constant (D/R(2)) estimated by fitting models for pore and surface diffusion to time-dependent adsorption profiles. No concentration dependence was found for pore diffusion; however, the surface diffusion time constant was shown to decrease with respect to increasing hydrogen concentration.

A robust volumetric apparatus and method for measuring high pressure hydrogen storage properties of nanostructured materials

Selective removal of carbon dioxide and hydrogen sulfide from other gases is usually difficult to achieve because most of the available sorbents will also adsorb other unwanted molecules. SAPO-43 is a microporous sorbent with appropriate dimensions and characteristics for these types of separations, but previous studies have shown that, because of low thermal stability, it is not suitable. This study discusses a procedure developed to partially remove the organic moiety used for synthesis of SAPO-43 while preserving the framework. The thermal process to remove the template (isopropylamine) results in decomposition of the species, which is believed to be a result of a Hofmann elimination process. Afterward, the partially calcined silicoaluminophosphate can be used as a selective adsorbent to separate molecules like CO2, H2O, and H2S while excluding molecules such as N2, CH4, and O2. In general, it was found that SAPO-43 has adsorption capacities of 1.1, 4.93, and 2.52 mmol/g for CO2, H2O, and H2S, respecti...

Partially calcined gismondine type silicoaluminophosphate SAPO-43: Isopropylamine elimination and separation of carbon dioxide, hydrogen sulfide, and water

Mechanism of catalyzed graphite oxidation by monolayer channeling and monolayer edge recession

The mechanism of methane formation from the reaction between graphite and hydrogen

The adsorption isotherms of naphthalene on three typical mesoporous adsorbents, mesosilicas MCM-41 and SBA-15, and mesocarbon CMK-3 were determined by column tests at 125 °C, with feed concentrations ranging from 7.63 × 10−5 to 4.64 × 10−2 mol m−3 (1.88 to 1140 ppm). The Langmuir model and constant-pattern wave propagation model were found to well fit the isotherms and the breakthrough curves, respectively. Regenerabilities of the mesoporous samples and a benchmark activated carbon (AC) were characterized based on thermogravimetric analysis (TGA). The results show mesoporosity significantly reduced the internal mass-transfer resistance, contributing to facile desorption and to fast adsorption kinetics shown by high overall mass-transfer rate coefficient following the order of: CMK-3 > SBA-15 > MCM-41. Micropore–mesopore coexisting structures present in CMK-3 and SBA-15 facilitated the adsorption at very low concentrations due to micropore-filling, while greater surface hydrophobicity and micropore abundance on CMK-3 exhibited larger affinity for nonpolar naphthalene, rendering the highest adsorption capacity (1.014 mol m−3) among all sorbents including ACs. SBA-15 showed higher regenerability with a desorption temperature below 440 K, owing to the weaker binding and diffusion advantages contributed by the interconnectivity between primary mesopores.

https://ir.nctu.edu.tw:443/bitstream/11536/133207/1/2cfee3f01e72d297d4f91e3cca0b0194.pdf

Performance of mesoporous silicas (MCM-41 and SBA-15) and carbon (CMK-3) in the removal of gas-phase naphthalene: Adsorption capacity, rate and regenerability

Ralph T. Yang

Papers

A robust volumetric apparatus and method for measuring high pressure hydrogen storage properties of nanostructured materials

Partially calcined gismondine type silicoaluminophosphate SAPO-43: Isopropylamine elimination and separation of carbon dioxide, hydrogen sulfide, and water

Mechanism of catalyzed graphite oxidation by monolayer channeling and monolayer edge recession

The mechanism of methane formation from the reaction between graphite and hydrogen

Performance of mesoporous silicas (MCM-41 and SBA-15) and carbon (CMK-3) in the removal of gas-phase naphthalene: Adsorption capacity, rate and regenerability