| Summary: | The use of electromagnetic interference shielding materials in the mitigation of electromagnetic pollution requires a broader perspective, encompassing not only the enhancement of the overall shielding efficiency (SE<sub>T</sub>), but also the distinct emphasis on the contribution of the absorption shielding efficiency within the total shielding efficiency (SE<sub>A</sub>/SE<sub>T</sub>). The development of lightweight, biodegradable electromagnetic interference shielding materials with dominant absorption mechanisms is of paramount importance in reducing electromagnetic pollution and the environmental impact. This study presents a successful fabrication strategy for a poly(lactic acid)/polycaprolactone/multi-walled carbon nanotube (PCL/PLA/MWCNT) composite foam, featuring a uniform porous structure. In this approach, melt mixing is combined with particle leaching techniques to create a co-continuous phase morphology when PCL and PLA are present in equal mass ratios. The MWCNT is selectively dispersed within the PCL matrix, which facilitates the formation of a robust conductive network within this morphology. In addition, the addition of the MWCNT content reduces the size of the phase domain in the PCL/PLA/MWCNT composite, showing an adept ability to construct a compact and stable conductive network. Based on its porous architecture and continuous conductive network, the composite foam with an 80% porosity and 7 wt% MWCNT content manifests an exceptional EMI shielding performance. The SE<sub>T</sub>, specific SE<sub>T</sub>, and SE<sub>A</sub>/SE<sub>T</sub> values achieved are 22.88 dB, 88.68 dB·cm<sup>3</sup>/g, and 85.80%, respectively. Additionally, the resulting composite foams exhibit a certain resistance to compression-induced deformations. In summary, this study introduces a practical solution that facilitates the production of absorption-dominated, lightweight, and biodegradable EMI shielding materials at scale.
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