Valorization of 'Waste' MXene through Multifunctional Green Composites with High-Efficiency EMI Shielding
The scalable deployment of MXene-based electromagnetic interference (EMI) shields is constrained by the low yield of delaminated MXenes and the discarding of MXene sediment (MS) by-products, which constitute 80–90 wt.% of synthesized material. This study repurposes MS, comprising incompletely etched MAX phase and multilayer MXenes, into multifunctional nanocomposite films with cellulose nanofibers (CNFs) via aqueous casting. The 80 wt.% MS/CNF film achieves an X-band EMI shielding effectiveness (SE) of 52.3 dB at 0.57 mm thickness, with tunable SE exceeding 53.9 dB at 0.50 mm across X-, Ku-, K-, and Ka-bands. The film exhibits a photothermal response reaching 100 °C within 80 s under 100 mW/cm² irradiation, alongside mechanical robustness and electrical conductivity. By valorizing an industrial waste stream, this approach addresses the cost-ineffectiveness and limited utilization efficiency of MXenes, offering a scalable route for wearable electronics, EMI shielding, and thermal therapy. The findings establish a precedent for waste-to-resource engineering in 2D material composites, with direct implications for reducing precursor costs and enabling high-performance, sustainable shielding solutions.