Stacked assemblies of ultraporous nanocellulose foams and hybrid films as frequency-selective surfaces for 6G wireless telecommunication

• Nanocellulose is applied to design fully bio-based and sustainable frequency-selective surface devices for high-frequency wireless communication. • Nanocellulose aerogels combined with metal–organic framework materials achieve extremely low dielectric properties, providing an ultralight substrate suitable for millimeter-wave and terahertz operation. • Biochar incorporated into nanocellulose films enables conductive, laser-patterned filters that allow controlled transmission and resonance-based attenuation of electromagnetic waves. • Multilayer structures based entirely on nanostructured cellulose demonstrate tunable transmission, broadened attenuation bands, and improved phase modulation across the 60 GHz to 0.51 terahertz range. With rapid progress in wireless communication, the need for advanced frequency-selective surfaces (FSSs) that operate efficiently at high frequencies is growing. This study presents sustainable, high-performance FSSs by laminating cellulose nanofiber (CNF) film filters, laser-patterned with millimeter-scale apertures, onto ultralight cross-linked CNF foams (aerogels). These biogenic FSSs cover a broad frequency range from 60 GHz to 0.51 THz. Added biochar enhances film conductivity, while metal–organic frameworks (MOFs) improve foam dielectric properties and surface area. The resulting foams exhibit near-air permittivity (ε r ≈ 1.01) and low loss tangent, confirming their suitability as high-frequency substrates. The patterned CNF films enable tuning of transmission and reflection properties, achieving high signal transmission (>90%) between 60 and 90 GHz and targeted resonance-based attenuation. Multilayered CNF-based stacks of perforated films and foams show enhanced transmission, wider attenuation bands, and improved phase modulation compared to conventional FSS structures. This work highlights the potential of nanostructured, bio-derived cellulose for next-generation FSS devices, particularly for 5G and 6G applications.