Ultralight Mesoporous Magnetic Frameworks by Interfacial Assembly of Prussian Blue Nanocubes

A facile approach for the synthesis of ultralight iron oxide hierarchical structures with tailorable macro‐ and mesoporosity is reported. This method entails the growth of porous Prussian blue (PB) single crystals on the surface of a polyurethane sponge, followed by in situ thermal conversion of PB crystals into three‐dimensional mesoporous iron oxide (3DMI) architectures. Compared to previously reported ultralight materials, the 3DMI architectures possess hierarchical macro‐ and mesoporous frameworks with multiple advantageous features, including high surface area (ca. 117 m2 g−1) and ultralow density (6–11 mg cm−3). Furthermore, they can be synthesized on a kilogram scale. More importantly, these 3DMI structures exhibit superparamagnetism and tunable hydrophilicity/hydrophobicity, thus allowing for efficient multiphase interfacial adsorption and fast multiphase catalysis. Ultralight: A method for the synthesis of three‐dimensional iron oxide (3DMI) architectures that feature hierarchically porous frameworks, high surface area (ca. 117 m2 g−1), and ultralow density (ca. 6 mg cm−3) has been developed. These 3DMI materials exhibit high superparamagnetism and tunable hydrophilicity and hydrophobicity, and can be cut and tailored into arbitrary shapes.