Nanoporous metal foams (NMFs) have been a long sought-after class of materials in the quest for high-surface-area conductive and catalytic materials. Herein we present an overview of newly developed synthetic strategies for producing NMFs along with an in-depth discussion of combustion synthesis as a versatile and scalable approach for the preparation of nanoporous, nanostructured metal foams. Current applications of NMFs prepared using combustion synthesis are also presented including hydrogen storage and catalysis.

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The synthesis of low-density, nanoporous materials has been an active area of study in chemistry and materials science dating back to the initial synthesis of aerogels. These materials, however, are most often limited to metal oxides, e.g., silica and alumina, and organic aerogels, e.g., resorcinol/formaldehyde, or carbon aerogels, produced from the pyrolysis of organic aerogels. The ability to form monolithic metallic nanocellular porous materials is difficult and sometimes elusive using conventional methodology. Here we report a relatively simple method to access unprecedented ultralow-density, nanostructured, monolithic, transition-metal foams, utilizing self-propagating combustion synthesis of novel transition-metal complexes containing high nitrogen energetic ligands. During the investigation of the decomposition behavior of the high-nitrogen transition metal complexes, it was discovered that nanostructured metal monolithic foams were formed in a post flame-front dynamic assembly having remarkably low densities down to 0.011 g cm(-3) and extremely high surface areas as high as 270 m(2) g(-1). We have produced monolithic nanoporous metal foams via this method of iron, cobalt, copper, and silver metals. We expect to be able to apply this to many other metals and to be able to tailor the resulting structure significantly.

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The explosive erythritol tetranitrate (ETN) has been known since 1849 and has applications as a vasodilator; however, little is known about its structure and bonding. Here we present the X-ray crystal structure of erythritol tetranitrate (ETN), along with characterization by nuclear magnetic resonance (NMR), infrared spectroscopy (IR), elemental analysis, and X-ray diffraction (XRD). Crystal packing and morphology are discussed in relation to explosive handling sensitivity (impact, spark, and friction testing). We compare the structure and property relationship to a closely related common nitrate ester, pentaerythritol tetranitrate (PETN).