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Oversolubility effects refer to a large increase of the solubility of gases in liquids confined in nanoporous solids with respect to the value predicted by Henry's law. This review presents the state of the art of oversolubility by discussing the molecular mechanisms responsible for such effects and the conditions for their observation. Both experimental and theoretical approaches are reviewed, in a non-exhaustive fashion, with special emphasis on results that have helped to unravel the oversolubility phenomenon. Different porous materials including metal-organic frameworks (MOF), ordered porous silicas, and zeolites are considered in combination with various nanoconfined liquids and gases relevant to practical applications in energy and environmental science. Depending on the gas/liquid/solid system considered, oversolubility is shown to pertain either to adsorption (increased concentration at solid/gas and liquid/gas interfaces) or to confinement-induced solubility increase. We also critically discuss when oversolubility effects are expected to lead to improved performance in catalysis or environmental applications such as for air purification. Image 1 • We present the state of the art on oversolubility in nanoporous materials. • Molecular mechanisms are presented and discussed. • Both experimental and theoretical approaches are reviewed with special emphasis on results that have helped unravel the oversolubility phenomenon. • We provide suggestions for future investigations and application perspectives. [ABSTRACT FROM AUTHOR]

Abstract: Continuous thin zeolite NaA films have been synthesized on macroporous α-alumina supports subjected to a simple pretreatment and without seeding. By modifying the supports with a cationic polymer and even with glucose or polyethylene glycol and subsequent calcination at 673K, a substantial improvement in terms of layer continuity and crystal intergrowth is observed compared to coatings prepared on unmodified supports. We attribute this positive effect to a fine interplay between the presence of a monolayer formed by carbon–oxygen species, mainly of the carboxylic type, on top of the calcined supports and to the negative net charge of the surface under synthesis conditions. The resulting double layer of solvated Na+ ions on the support would act as nucleation promoter and formation of the NaA thin film. This new method presents several advantages and may form the basis to scale up membrane synthesis in view of the simple and cheap pretreatment together with the elimination of pre-seeding steps. [Copyright &y& Elsevier]

Abstract: For economic and environmental reasons, there is a strong incentive to replace of homogeneous by green and efficient heterogeneous processes in catalysis. The Friedel-Crafts alkylation of aromatics is a marking example. Numbers of homogeneous catalysts (such as HF, H2SO3, and AlCl3) have been replaced by H-form zeolites. However, large pore zeolite can not accommodate bulk aromatic molecules and/or alkylating agents avoiding the reaction to take place within the porous network. Due to their larger pore size, metal-organic frameworks (MOFs) open the doors to the alkylation of very large poly-aromatic compounds. We report different approaches for the design of acid shape selective MOFs. The first refers to a “zeolite mimetic” approach. It deals with the design of porous Zn or Al based MOF exhibiting bridging –OH species (MOF-69, MIL-53 Al) like those found in zeolites [Si–O(H)–Al]. The second approach aims at synthesizing MOF materials having structural defects to generate active catalytic centers. Two different synthetic strategies were investigated, either by fast precipitation or by the partial substitution of dicarboxylic by mono-carboxylic acid linkers. Acid centers have been characterized by solid 1H NMR and Diffuse Reflectance IR. The mono-alkylation of biphenyl with tert-BuCl is achieved with 100% of para-selectivity, well superior to H-MOR and H-BEA reference zeolites. [Copyright &y& Elsevier]

Nano-zeolites and hierarchical zeolites have shown enhanced transport properties that are generally attributed to a shorter diffusion path length (L). However, the concomitant increase in the external surface of these types of zeolites may also affect overall transport as the interfaces may act as diffusion barriers. Recently, hollow zeolite crystals have been presented as an alternative zeolite morphology. They possess a large inner cavity and an overall size and shape similar to those of plain microporous zeolite. In contrast to classic hierarchical zeolite materials, the inner cavity of the hollow zeolite induces a shortened diffusion path length with no effect on external surface area. In this work, we have studied the impact of diffusion path length on transport properties by comparing the characteristic time of transport of hydrocarbons in plain zeolite crystals and their hollow counterparts, using zero-length column (ZLC) measurements. Our results show that hollow morphology doubles or quadruples the transport speed for Silicalite-1 and Beta zeolites, respectively. Compared to other reports focusing on nanosized or hierarchical zeolites, this study is free of any bias due to major modifications in external surface area, because hollow and plain zeolites have very similar crystal dimensions. 3 Main results• Hollow zeolites allow faster transport than plain zeolites• The faster transport is directly linked to the shortening of diffusion path length.• While keeping hollow and plain zeolite crystals with the same crystal size, we can investigate the impact of a different diffusion path length, without bias from different external surface area. Image 1 • Hollow zeolites allow faster transport than plain zeolites. • The faster transport is directly linked to the shortening of diffusion path length. • The impact of diffusion on hollow and plain zeolithe is investigated without bias of different external surface. [ABSTRACT FROM AUTHOR]