With the rapid development of electronic equipment and communication technology, it is urgent to develop composites with absorption-dominated and high electromagnetic interference shielding effectiveness (EMI SE) to prevent secondary pollution of electromagnetic (EM) waves. Herein, an effective strategy is employed to fabricate porous Ni-coated melamine foam (Ni@MF)/multi-walled carbon nanotubes (CNT)/temperature-sensitive microspheres (TSM)/polydimethylsiloxane (PDMS) composite foams with an absorption-dominated EMI shielding mechanism and high EMI SE at low filler loading. The bi-conductive network, including a high-efficiency Ni@MF sponge obtained by electroless plating and ordered arrangement and distribution of CNTs induced by the volume exclusion effect, endows the Ni@MF/CNT/TSM/PDMS composite foam with an extremely high conductivity of 2799.8 S m⁻¹ and excellent EMI SE of 45.3 dB with a low CNT loading of 3.0 wt%. The absorption coefficient (A) exceeding 0.72 indicates the absorption-dominated EMI shielding mechanism due to weakened impedance matching and diversiform dissipation mechanisms. What's more, the hydrophobicity, excellent mechanical properties, stable pH resistance and outstanding EMI shielding durability promote the composite foams to maintain impressive performance even in complex and harsh environments. This work establishes an efficient strategy for the absorption-dominated EMI shielding composite foams with a porous structure and bi-conductive network structure, which reveals prospective applications in intelligent electronic equipment and next-generation communication technologies.

With the strong support of the government for emerging technology industries, electromagnetic waves have brought convenience to people's lives, but also become an undeniable new source of pollution. Therefore, it is vital to develop new high-performance electromagnetic shielding materials. Herein, we designed a well-structured asymmetrical gradient multilayer composite film by constructing a controllable electromagnetic gradient. Using cellulose nanofibers as the matrix, a layer-by-layer filtration method was used to rationally distribute FeCo@rGO and MXene fillers to build an ordered multilayer structure that provides alternating conductive and magnetic gradients. Owing to gradient absorption shielding and reflection mechanisms for electromagnetic waves within the film layer, the EMI shielding efficiency (EMI SE) of the asymmetrical gradient alternating six-layer composite film reached 45.2 dB (X-band), and the reflection coefficient was reduced to 0.71 when 20 wt% filler was added. In addition, this composite film has good thermal conductivity and mechanical properties, exhibiting thermal conductivity of 2.90 W (m⁻¹ K⁻¹) and tensile strength of 26.2 MPa. This strategy provides a feasible approach for designing electromagnetic shielding composite materials with adjustable electromagnetic properties and has significant practical significance in expanding the application of MXene-based composite materials.