Multifunctional Bicontinuous Composite Foams with Ultralow Percolation Thresholds.

Integrating ultralight weight and strong mechanical performance into cellular monolith is a challenge unresolved yet. Here, we propose a skeleton-assisted self-assembly method to design ultralight bicontinuous composite foams (BCCFs) with high mechanical robustness and ultralow percolation thresholds. Polymer foam was employed as the skeleton to support assembled graphene networks, forming BCCFs with a high tensile strength (∼80 kPa) and breakage elongation (>22.2%). The paraffin and poly(dimethylsiloxane) infiltrated BCCFs show a record low percolation threshold of 0.006 vol % and a relatively high electrical conductivity of 0.81 S m-1 at a low graphene content of 0.216 vol %. The BCCFs demonstrate high and adjustable microwave-absorbing (MA) properties. The effective absorption bandwidth (reflection loss ≤ -10 dB) for BCCFs with a low graphene loading of 3.4 mg cm-3 achieves 9.0 GHz at a thickness of 4 mm, and it further covers 13.6 GHz considering the adjustability of preferred absorption band. The BCCFs with an extremely low graphene load of 0.14 mg cm-3 were further used for durable and efficient oil adsorption, which can adsorb >60 times their own weight. The facile fabrication of bicontinuous composite foams opens the avenue for practical applications of high-strength, multifunctional, and productive graphene-based foams.