Synergistic Effect of MOF@CMC‐Derived Magnetic Nanocomposites: Enhancing Electromagnetic Interference Shielding and Joule Heating

Emerging as attractive alternatives for sustainable, low‐cost, and high‐performance electromagnetic interference (EMI) shielding, biomass‐derived carbon is nonetheless constrained by a limited repertoire of shielding mechanisms. Herein, a straightforward method was employed to synthesize self‐supporting Co nanoparticles embedded in porous N‐doped carbon (Co@PNC) composite, which is derived from a film of Co‐MOF and sodium carboxymethyl cellulose (Co‐MOF@CMC). Benefiting from the synergistic effects between the three‐dimensional conductive network formed by porous N‐doped carbon and the embedded Co nanoparticles, the Co@PNC composite incorporates abundant heterogeneous interfaces, which collectively enhance both dielectric loss and magnetic losses. Among them, the Co@PNC‐3 composite exhibited an exceptional average EMI shielding effectiveness (SE) of 63.5 dB in the X‐band at a thickness of 1.2 mm, effectively attenuating 99.99996% of the incident electromagnetic waves. Additionally, it possesses a low density (0.199 g cm −3 ), with a specific EMI shielding effectiveness value as high as 2496.1 dB cm 2 g −1 . Meanwhile, the Co@PNC‐3 composite demonstrated efficient electro‐thermal conversion capabilities, rapidly reaching 158.5°C under a low driving voltage of 4 V, along with excellent flame‐retardant properties. This study provides a simple, green, and feasible strategy for the preparation of cellulose‐derived composites with high EMI shielding effectiveness and multifunctional properties.