Salt-Assisted Pyrolysis for the Preparation of Three-Dimensional Carbon Structure Composed of Nanosheet and Polyhedra for Efficient Microwave Absorption

Abstract

Metal-organic framework (MOF)-derived carbon materials are considered to be high potential candidates for electromagnetic absorbers, based on their high specific surface area and porosity. However, the rational design of three-dimensional (3D) MOF-derived microwave absorbing (MA) materials with stable structures and ultra-wide microwave absorption bandwidth (EAB) is still a challenge. Herein, a strategy for salt-assisted pyrolysis of MOF is proposed to construct 3D hybrid nanostructure comprising 0D carbon polyhedra and 2D carbon nanosheet. The EAB of the composite can be optimized to 6.23 GHz at a remarkably thin thickness of 2.0 mm by changing the species and proportion of salt in the pyrolysis process to regulate the three-dimensional structure of the product. Numerical simulation results demonstrate that 3D hybrid nanostructures consisting of nanoparticles and nanosheets outperform isolated nanoparticle structures in terms of interfacial polarization and conductivity loss. In addition, when the electromagnetic wave is incident vertically, the maximum radar cross-sectional (RCS) value of the metal plate coated with MA material reaches -4 dBsm, which is much lower than that of a clean metal plate, proving that the product has the potential for large-scale. This work not only proposes a new strategy to construct MOF-derived 3D nanostructures but provides an effective guide to optimize the absorption properties of MOF-derived carbon MA materials.

Keywords: Salt-assisted pyrolysis, Microwave absorbing, 3D hybrid nanostructures, Numerical simulation, Radar cross-sectional.