A hierarchical Co @ mesoporous C/ macroporous C sheet composite derived from bimetallic MOF and oroxylum indicum for enhanced microwave absorption

Recently, biomass-derived carbon absorbing materials have received extensive attention due to their diverse structures, wide sources and low cost. However, it is still a great challenge to construct high-efficiency biomass-based absorbers with hierarchical and multi-component micro-nanoarchitecture. To this end, a novel Co @ mesoporous C/macroporous C sheet hybrid was successfully prepared by in-situ self-assembly of ZnCo MOF nanosheet arrays on biomass-derived porous carbon sheets via hydrothermal and pyrolysis methods. By tuning the molar ratio of Zn2+ to Co2+ ions, the optimal RLmin value was up to −66.9 dB and a wide EAB of 5.6 GHz was simultaneously obtained at the filler loading of 12 wt%. The results showed that this unique 3D micro-nanostructure possessed larger specific surface area, rich heterogeneous interfaces, massive defects and multi-level porosity, which was favorable for multiple reflection and scattering, dielectric loss, magnetic loss, as well as impedance matching. As a consequence, the as-prepared composites displayed significantly enhanced microwave absorption performance than the pristine biomass carbon. In this regard, the integration of MOF monomer and biomass matrix is expected to provide new guidance for the design of hierarchical multi-scale porous heterostructures as lightweight and enhanced microwave absorbing materials.