Multiscale design of TEMPO-oxidized cellulose nanofiber/biomass-derived porous composites for electromagnetic wave absorption and multifunctional protection.

Sustainable cellulose-based porous composites are promising candidates for electromagnetic wave (EMW) protection, but integrating efficient attenuation, thermal resistance, and antibacterial activity into a porous architecture remains challenging. Herein, a reed-biomass-derived porous composite was developed through multiscale engineering of magnetic-dielectric absorbers and a nanocellulose porous framework. At the microscale, graphene oxide-assisted pyrolysis produced graphene-modified reed carbon (G-RC) with increased surface roughness, defect density, and polar sites. These structural features enabled the uniform immobilization of poly(diallyldimethylammonium chloride)-modified carbonyl iron particles (P@CIP) and the formation of P@CIP-G-RC (CGR) heterointerfaces. At the macroscale, TEMPO-oxidized cellulose nanofibers (TOCNF) and styrene-acrylic emulsion (SAE) constructed a hierarchical porous-composite network that regulated absorber distribution, contributed to favorable impedance matching, and reduced heat transfer. The optimized TOCNF/SAE-2@CGR exhibited a minimum reflection loss (RLmin) of -57.31 dB at 3.6 mm and an effective absorption bandwidth of 6.65 GHz at 1.6 mm. Moreover, the porous composite showed a lower surface-temperature rise than expanded polystyrene, a residual mass of 98.57% at 800 °C, stability under repeated flame exposure, and effective inhibition of Staphylococcus aureus and Escherichia coli colony formation under the tested conditions. This work provides a cellulose-based multiscale design strategy for porous composites combining EMW absorption, thermal protection, and antibacterial performance.