Micro‐Macroporous Composite Materials – Preparation Techniques and Selected Applications: A Review

Abstract

Pores, on several orders of magnitude in size, control the properties of a solid material to a large extent. This is just as true for materials containing pores in the sub‐nanometer range like zeolites as for cellular foam structures with pores of several millimeters in size. All these porous materials have their distinct potential application ranging from heterogeneous catalysis to metal melt filtration. In many cases, the (hierarchical) combination of pores with different size regimes can improve the performance of the respective porous material or can lead to entirely new properties and applications. This review addresses the preparation and properties of microporous‐macroporous composite materials based on cellular foam supports (ceramic, metal, polymer) with a coating of a microporous compound (zeolite, zeotype framework, metal‐organic framework). The manufacturing of these materials can either be performed by dispersion‐based techniques, where the microporous coating is applied from a dispersion onto the cellular support (ex situ), or in situ by crystallization of the microporous compound directly onto the struts of the foam structure. In both cases, the general procedure can be modified by a pretreatment of the cellular support in order to improve the coating layer adherence, the overall amount of deposited material, or to control of the crystal morphology of the microporous compound.

Hierarchical Metal–Organic Frameworks with Macroporosity: Synthesis, Achievements, and Challenges

“…There has been a recent trend towards the development of new porous materials incorporating pores with different size regimes to form hierarchical systems with interconnected pores and entirely new properties for desired applications. While the concept of introducing meso-and macropores into microporous materials has been extensively investigated in zeolitic porous systems [19][20][21], development of metal-organic frameworks (MOFs) with open framework structures comprised of metal nodes and organic ligands has seen a rapid expansion of recent research interest. Advances in synthetic chemistry have reported numerous MOF structures (> 70,000 structures reported so far [22]) with potential use in gas storage [23][24][25], gas separation [26][27][28][29], catalysis [30,31], carbon dioxide capture [32][33][34], and as semiconductor materials [35,36].…”

Synthesis and characterization of thermoresponsive ZIF-8@PNIPAm-co-MAA microgel composites with enhanced performance as an adsorption/release platform

“…31 Namely, the synthesis of poly(methyl methacrylate) and polystyrene composites with water-sensitive Zn-based MOF-5 (which results in an increased stability towards hydrolysis, without compromising available pore volume), 32,33 the use of surface-graed MOF particles integrated with PNIPAm as thermoresponsive emulsiers and drug-delivery platforms, 34,35 and the use of hydrogels containing MOFs for adsorption from aqueous environments. 36 Inspired by such examples and the already reported possibility of combining colloidal templates and nanostructures, 37,38 we envisioned the possibility of synthesizing well dispersed polymer-MOF composites following a straightforward approach; i.e., by using pre-designed microgel particles featuring moieties able to trigger MOF heterogeneous nucleation, which would add microporosity to the thermoresponsive polymer. The main drive for such interest was to explore the possibility of attaining further control over adsorptiondesorption processes, colloidal stability, and the integration of further components in the composite (e.g.…”

Cellular Nickel-Yttria/Zirconia (Ni–YSZ) Cermet Foams: Manufacturing, Microstructure and Properties

“…Cellular structures are described for all of the material classes: metals, ceramics/glasses and polymers [1,2]. However, the knowledge of cellular composite materials is mostly limited to coated foam structures [3,4]. Cellular composites consisting of an interpenetrating phase network within the strut material are seldom described.…”