With its naturally occurring layered structure, hexagonal boron nitride (h-BN) has emerged as an important 2D material, possessing excellent properties such as high temperature stability, high thermal conductivity, as well as mechanical strength.
The fabrication of three-dimensional porous nanostructures from interconnected two-dimensional (2D) materials such as graphene, clays, metal dichalcogenides, etc. has proven to be a promising technique to exploit their properties for several applications including catalysis, energy storage, biological and environmental applications, mechanical damping, and gas sequestration.
In this new work, the researchers first liquid-phase-exfoliated h-BN in water to separate the layers, and then poly(vinyl alcohol) (PVA) was added (1-1.5 wt %), followed by in situ freeze-drying.
The hybrid structure exhibits enhanced mechanical properties, large surface area, and increased porosity.
According to the team, their fabrication method allows for the creation of intermolecular bonding between h-BN layers, where PVA acts like a bridge to link the individual layers, thus forming a network structure at the nanoscale.
Unlike pristine h-BN foams, which normally disintegrate immediately once removed from a freeze-drier, h-BN/PVA foams show a robust freestanding structure with favorable mechanical stability.
A detailed molecular dynamics study further verified and provided insights on the origins of such interconnections in improving the mechanical integrity.
The foam also exhibits excellent CO2 absorption of 340% and storage under varying pressure values, mainly due to nitrogen functional groups and an increased surface area.
Furthermore, when coated with polydimethylsiloxane (PDMS), the foam shows superior laser shielding properties by withstanding a varied amount of laser energy with minimal structural degradation.