Magnetic/conductive biochar frames derived from Fe3O4-coated loofah sponges for green electromagnetic interference shielding application

Several biochar frame electromagnetic interference shielding composites have been developed; however, integrating high shielding effectiveness (SE) and low reflection coefficient ([Formula: see text]) into biochar frames with excellent electrical conductivity have proven to be a great challenge. Herein, because of the abundant groups on the surface of the intricate fibers of the loofah sponge, it absorbed many iron ions, which can form a Fe 3 O 4 coating when they react with hydroxyl groups. After carbonization, the Fe 3 O 4 coating still tightly held the carbonized fibers in a porous structure, forming a biochar frame with consecutive magnetic/conductive interfaces. Furthermore, the incorporation of a Fe 3 O 4 coating did not negatively affect the electrical conductivity of the composites obtained ([Formula: see text]21 S/m) but instead endowed the composites with good magnetic properties. The resultant composites had an SE, specific SE, [Formula: see text] and green index ([Formula: see text]) of 47.2 dB, 363 dB/cm, 0.089, and 10.2, respectively, which were better than those of previously reported biochar-based shielding materials. The synergistic effect of the three-dimensional carbon frame, magnetic coating, and porous structure is responsible for excellent green shielding abilities.