'Hierarchy' is a property which can be attributed to a manifold of different immaterial systems, such as ideas, items and organisations or material ones like biological systems within living organisms or artificial, man-made constructions. The property 'hierarchy' is mainly characterised by a certain ordering of individual elements relative to each other, often in combination with a certain degree of branching.Especially mass-flow related systems in the natural environment feature special hierarchically branched patterns. This review is a survey into the world of hierarchical systems with special focus on hierarchically porous zeolite materials. A classification of hierarchical porosity is proposed based on the flow distribution pattern within the respective pore systems. In addition, this review might serve as a toolbox providing several synthetic and post-synthetic strategies to prepare zeolitic or zeolite containing material with tailored hierarchical porosity. Very often, such strategies with their underlying principles were developed for improving the performance of the final materials in different technical applications like adsorptive or catalytic processes. In the present review, besides on the hierarchically porous allzeolite material, special focus is laid on the preparation of zeolitic composite materials with hierarchical porosity capable to face the demands of industrial application.

During the past several years, different kinds of hierarchical structured zeolitic materials have been synthesized due to their highly attractive properties, such as superior mass/heat transfer characteristics, lower restriction of the diffusion of reactants in the mesopores, and low pressure drop. Our contribution provides general information regarding types and preparation methods of hierarchical zeolitic materials and their relative advantages and disadvantages. Thereafter, recent advances in the preparation and characterization of hierarchical zeolitic structures within the crystallites by post-synthetic treatment methods, such as dealumination or desilication; and structured devices by in situ and ex situ zeolite coatings on open-cellular ceramic foams as (non-reactive as well as reactive) supports are highlighted. Specific advantages of using hierarchical zeolitic catalysts/structures in selected catalytic reactions, such as benzene to phenol (BTOP) and methanol to olefins (MTO) are presented.

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Layered materials, such as layered sodium silicates and layered double hydroxides (LDHs), are well-known for their remarkable adsorption, intercalation and swelling properties. Their tunable interlayers offer an interesting avenue for the fabrication of pillared nanoporous materials, organic-inorganic hybrid materials and catalysts or catalyst supports. This perspective article provides a summary of the reactivity and applications of layered materials including aluminium-free layered sodium silicates (kanemite, ilerite (RUB-18 or octosilicate) and magadiite) and layered double hydroxides (LDHs). Recent developments in the use of layered sodium silicates as precursors for the preparation of various porous, functional and catalytic materials including zeolites, mesoporous materials, pillared layered silicates, organic-inorganic nanocomposites and synthesis of highly dispersed nanoparticles supported on silica are reviewed in detail. Along this perspective, we have attempted to illustrate the reactivity and transformational potential of LDHs in order to deduce the main differences and similarities between these two types of layered materials.

Zeolites are microporous crystalline aluminosilicates with molecular sieving capabilities (pore size < 1.3 nm).[1±3] The use of zeolite coatings on different supports (metal substrates, porous glass, ceramic honeycombs, mesoporous materials) has recently been proposed for catalysis, adsorption, and separation.[4±8] Open-cell ceramic foams [9±15] (connected pores in the 0.1±4 mm range) are gaining interest as zeolite carriers [11±15] due to their unique properties, for the development of new reactor concepts (monolithic, catalytic wall configurations) for technical catalytic and adsorption±separation processes. [15,16] Here we present, for the first time, a novel zeolite±ceramic composite material, with a bimodal (nano-, macroscale) pore system, obtained by coating the cell walls of microcellular polymer-derived ceramic foams (cell size~8 lm) with a thin, binder-free layer of MFI-type zeolite (Silicalite-1 and ZSM-5), produced by an in-situ conventional supported hydrothermal synthesis. To our knowledge, these materials represent the smallest microreactors/separators fabricated to date.Ceramic foams, with low thermal expansion coefficients and high thermal, mechanical, and chemical stability, are suitable as zeolite supports because they provide enhanced mass and heat transfer and a low pressure drop when compared to zeolite pellets used in fixed-bed reactors. [9,10] The fabrication of ceramic foams from preceramic polymers allows tailoring of the composition and morphology, and therefore of the final properties, of the porous material. [17,18] Very recently, [19,20] we fabricated mechanically stable ceramic microcellular [21,22] foams with a homogeneous interconnected porosity and an average cell size in the range of~1±100 lm, bulk density from 0.2±0.6 g cm ±3, and cell density from~10 7 ±10 12 cells cm ±3 . The starting materials were poly(methyl methacrylate) (PMMA) microbeads, acting as sacrificial template, and a COMMUNICATIONS

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The density of stacking faults was estimated following the Warren method [30]. For the (10.1) line, and taking into account only the stacking faults of growth type, d is given bywhere d is the reticular distance corresponding to the (10.1) reflection and c is the cell parameter of the hexagonal phase [30]. B c (2h) is the FWHH corrected for broadening due to the finite size of the crystallites, according to the relationScanning electron microscopy (SEM) observations were carried out with a Hitachi 4500 field emission gun microscope. Transmission electron microscopy (TEM) observations were carried out with a Jeol CXII microscope operating at 100 kV. The metal powder was dispersed in ethanol; one drop of the suspension was deposited on the carbon membrane of the microscope grid, and the solvent was evaporated at room temperature. High-resolution TEM (HRTEM) was performed with a Jeol JEM 2010F UHR operating at 200 kV. Local EDX analyses were performed using a PGT IMIX PC system with an analysis spot of 25 nm.Magnetic measurements on compacted powders were performed with a Quantum Design MPMS-5S superconducting quantum interference device (SQUID) magnetometer at 300 K.