Sugar-Templated 3D GnP@PDMS/CoNi@C Composites for Absorption-Dominant EMI Shielding and Efficient Thermal Management

The rapid growth of electronic devices has created an increasing demand for lightweight polymer composites that can provide effective electromagnetic interference (EMI) shielding while also dissipating heat. In this study, a three-dimensional dual-network composite based on graphene nanoplatelets (GnP), polydimethylsiloxane (PDMS), and MOF-derived magnetic nanoparticles was developed for absorption-dominant EMI shielding and enhanced thermal conductivity. A porous GnP@PDMS skeleton was first prepared using a sugar-templating method, followed by vacuum-assisted infiltration of carbonized magnetic nanoparticles derived from Co/Ni metal-organic frameworks. This process produced an interconnected conductive-magnetic network throughout the composite. The combined conductive GnP network and magnetic phase improved impedance matching, magnetic loss, and interfacial polarization, resulting in a transition from reflection-dominant to absorption-dominant shielding. The optimized GnP30@PDMS/CM5 composite achieved an EMI shielding effectiveness of 71.5 dB and an absorption coefficient of 0.69, compared with 0.15 for GnP30@PDMS without the magnetic component. The interconnected dual network also formed efficient heat-transfer pathways, giving a through-plane thermal conductivity of 1.37 W/m·K. In addition, the composite exhibited good heat dissipation, mechanical strength, thermal stability, and hydrophobicity. These results demonstrate that dual-network engineering of conductive and magnetic phases is an effective strategy for developing multifunctional polymer composites for EMI shielding and thermal management in advanced electronic applications.