Self-assembly of ultralight and compressible inorganic sponges with hierarchical porosity by electrospinning

Abstract The construction of three dimensional macroporous architectures holds exciting implications for applications such as catalysis, sensing, tissue engineering and thermal insulation. Here, we report a general self-assembly process for inorganic sponges with hierarchical porosity of intrafibre micro-/meso-/macropores and interfibre macropores. The as-fabricated SiO2-TiO2 sponge possesses a high porosity of >99.86%, ultralow bulk density of 2.9 mg cm−3 and enhanced compressibility (recovery from 50% compression). The self-assembly mechanism of the SiO2-TiO2 sponge has been investigated in detail. The results confirmed that the hydrolysis and polycondensation of mixed inorganic alkoxides could affect the solidification process and the charge transpote during electrospinning, and plays an essential role on the hierarchical porosity and the self-assembly of the sponge macro-structure. The concerted effects of the solidification and electrostatic repulsion between fibres are responsible for the self-assembly process of the electrospun PVP-SiO2-TiO2 sponge. When used as a thermal insulation material, the SiO2-TiO2 sponge shows good fireproof performances. The current contribution may guide more construction of functional inorganic macroporous architectures for advance applications in future.