Creating porous structures and gradient structures are two commonly used design strategies for terahertz (THz) absorption enhancement. However, the synergistic effect of porous structure and gradient structure on THz absorption still remains less explored. Here, we took an almost non-conductive porous carbon foam as raw material, and fabricated an integrated gradient porous carbon foam (PCF) by microwave selective sintering. The experimental results show that the synergistic effect of the porous and gradient structures resulted in a 140% improvement in THz absorption performance. Specifically, an excellent average absorption intensity of ‒38.8 dB (absorptivity is about 99.99%) is obtained in the frequency range from 0.5 to 4.0 THz. COMSOL simulation and transmission line model were applied to explore the formation mechanism and the gradient loss capabilities of gradient structure. This work not only reveals the synergistic enhancement mechanism of porous and gradient structures for the THz absorption, but also provides new insights into the design of high-performance THz absorbers in the future.

Electromagnetic interference (EMI) shielding materials have received considerable attention in recent years. The EMI shielding effectiveness (SE) of materials depends on not only their composition but also their microstructures. Among various microstructure prototypes, porous structures provide the advantages of low density and high terahertz wave absorption. In this study, by using carbonised wood (CW) as a template, 1-mm-thick MAX@CW composites (Ti₂AlC@CW, V₂AlC@CW, and Cr₂AlC@CW) with a porous structure were fabricated through the molten salt method. The MAX@CW composites led to the formation of a conductive network and multilayer interface, which resulted in improved EMI SE. The average EMI SE values of the three MAX@CW composites were > 45 dB in the frequency of 0.6-1.6 THz. Among the composites, V₂AlC@CW exhibited the highest average EMI SE of 55 dB.