In this study, a composite material based on agricultural waste coconut shells was successfully developed as an efficient, lightweight, and sustainable electromagnetic wave (EMW) absorber. Specifically, coconut shells were used as the raw material, and a simple one-step activation charring process was employed to obtain coconut shell porous carbon (CSPC). ZnFe2O4 with a hollow spherical structure was then in situ grown on the surface of CSPC, resulting in a special ZnFe2O4/ CSPC composite material. Due to its unique hollow structure, porous characteristics, and heterogeneous interfaces, the composite material achieved optimized impedance matching, leading to excellent EMW absorption performance. The fabricated ZnFe2O4/ CSPC composite demonstrated a minimum reflection loss ( RLmin) of − 37.32 dB at 10.80 GHz and an effective absorption bandwidth of 2.40 GHz at a thickness of only 2.0 mm. SEM and TEM analyses confirmed that the composite possessed a hollow and porous structure, while the BET specific surface area was measured at 133.709 m2 g⁻1. Based on the synergistic effects of ZnFe2O4 and CSPC, dielectric losses, magnetic losses, and impedance matching, the potential EMW absorption mechanisms were proposed. The ZnFe2O4/ CSPC composite material prepared in this study was a novel, green, and sustainable EMW absorber.

Biomass-derived carbon materials have attracted considerable attention in electromagnetic wave (EMW) absorption applications due to their advantages of low cost, light weight, and sustainability. Herein, bagasse-based porous carbon (BPC) was prepared by canonization and activation process from natural waste bagasse. The porous flower-like MoS2/ BPC composites were successfully prepared for efficient microwave absorption via hydrothermal process by in-situ formation of flower-like MoS2 into the porous structure of BPC. The effect of hydrothermal time and hydrothermal temperature on surface morphology, degree of graphitization, surface chemical composition and impedance matching of the prepared samples was investigated. Results demonstrated that when the hydrothermal temperature was 220 °C, and the hydrothermal time was 24 h, the obtained MoS2/ BPC sample (named as MoS2/ BPC-220 ℃) showed the minimum reflection loss value (RL) of − 41.6 dB at 8.96 GHz and exhibited effective microwave absorption bandwidth (EAB) of 4.32 GHz at a relatively thin thickness of 1.5 mm. This work provides a promising way to prepare novel biomass-derived porous carbon for strong broadband electromagnetic absorption.