Superelastic Cobalt Silicate@Resorcinol Formaldehyde Resin Core‐Shell Nanobelt Aerogel Monoliths with Outstanding Fire Retardant and Thermal Insulating Capability

Abstract The practical applications of resorcinol formaldehyde resin (RFR) aerogels are prevented by their poor mechanical properties. Herein, a facile template‐directed method is reported to produce macroscopic free‐standing cobalt silicate (CS)@RFR core‐shell nanobelt aerogels that display superelastic behavior and outstanding thermal insulating and fire‐resistant capability. The synthesis relies on the polymerization of RFR on pre‐formed CS nanobelts which leads to in situ formation of hydrogel monoliths that can be transformed to corresponding aerogels by a freeze‐drying method. The composite nanobelt aerogel can withstand a compressive load of more than 4000 times of its own weight and fully recover after the removal of the weight. It can also sustain 1000 compressive cycles with 6.9% plastic deformation and 91.8% of the maximum stress remaining, with a constant energy loss coefficient as low as 0.16, at the set strain of 30%. The extraordinary mechanical properties are believed to be associated with the structural flexibility of the nanobelts and the RFR‐reinforced joints between the crosslinked nanobelts. These inorganic‐organic composite aerogels also show good thermal insulation and excellent fire‐proof capability. This work provides an effective strategy for fabricating superelastic RFR‐based aerogels which show promising applications in fields such as thermal insulation, energy storage, and catalyst support.