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Liu et al. Soft Sci. 2025, 5, 7 https://dx.doi.org/10.20517/ss.2024.69 Page 13 of 25

CoNi-MOFs-derived CoNi was anchored onto core-shell Ni@C. By cooperating with PDA, the interface of
CoNi-MOFs and NiO was enhanced by electrostatic interaction. Because of the multiple conductive
networks, magnetic interaction, and interfacial polarization, the composite had good microwave absorption.
[26]
The RLmin reached -51.4 dB at 1.9 mm, and the EAB was 4.6 GHz at 1.3 mm . The zeolitic imidazolate
framework (ZIF)-derived C was introduced into carbonyl iron (Fe/FeCo@C) via in situ dopamine
polymerization on the carbonyl iron and pyrolysis. The multiple polarization effect from heterogeneous
interfaces increased the EMW absorption. The conductive network combined magnetic and dielectric loss
to optimize impedance matching. A Fe/FeCo@C/PP composite was prepared by fused deposition modeling.
The composite with 40% filling had an RLmin reached -60 dB at 1.7 mm, and an EAB of 4.75 GHz at
[21]
1.5 mm . PDA-derived C@MXene composite was fabricated via in-situ polymerization and pyrolysis. The
composite at 2.8 mm with 7.5 wt% filling had an RLmin of -46.92 dB and an EABmax of 7.01 GHz. The
combination of MXene and PDA created defects that caused dipole polarization, triggered heterogeneous
space charge and electron density distribution to increase interfacial polarization and provided excellent
impedance matching . Salt template impregnation was used to prepare a composite foam with resorcinol
[46]
terephthalaldehyde resin and a porous pyrolyzed PDA/carbon nanotube (CNT)-Fe O . The conductivity
3
4
and mechanical characteristics of the foam improved by 168% and 74 times, respectively, because of the pi-
pi interactions and conductivity of the filler. Due to conductivity loss and interfacial polarization, the EAB
was 8.32 GHz and the RLmin was -33.0 dB .
[86]
Insulating polymer-based EMW absorbers
Recently, polymer-based composite materials consisting of insulating polymers and electrically/thermally
conductive fillers have received considerable attention in EMW shielding and absorption due to their
lightweight, abundant varieties, flexibility, easy processing, low cost, resistance to corrosion, excellent
shielding performance, and tunable electrical properties [10,87] . To enhance the EMI shielding, the conductive
fillers are joined to one another to create a conductive channel. To further enhance EMI shielding and
absorption, conductive fillers can be used as dielectric and magnetic loss materials [88,89] .

The insulating polymer matrix for EMW absorption can be both thermosets such as polydimethylsiloxane
(PDMS), epoxy resins (EP) or polyurethanes (PU) and thermoplastics such as poly(vinylidene fluoride)
(PVDF) or cellulose nanofibrils (CNFs) [90-92] .

PDMS
A sandwich structure with a MXene@SiO interlayer was prepared via solvent induced phase separation
2
method, and then compounded with PDMS. The composite had large specific surface area of 545.42 m ·g .
-1
2
The MXene@SiO increased the packing density and sedimentary mode of the filler, and enhanced the EMI
2
[24]
SE to 43.3 dB, mechanical strength of 4.61 MPa . A composite made of layers of metalized polyimide (PI),
Fe O @PDMS dipped melamine-formaldehyde (MF), and Ni-coated melamine foam was prepared via
4
3
layer-by-layer stacking. The multilayer structure enhanced the interface polarization loss and expanded the
propagation pathway. An EMI SE of 54.20 dB was obtained because of the interfacial polarization loss and
EM loss caused by Fe O and Ni. The foam also had flame retardancy with a limiting oxygen index (LOI) of
4
3
27% . A poly (l-lactide) (PLLA)/PDMS/multi-walled CNT (MWCNT) composite with honeycomb-like
[93]
conductive networks was fabricated using PLLA as a volume-occupying phase. The EMI SE of the
composites with etched 300 μm spherical micro-particles with rough surfaces achieved 35.1 dB, with
absorption dominated mechanism . Aligned NCNF/barium titanate (CNF-BaTiO )/PDMS composite was
[68]
3
prepared by electrospinning and carbonization. The composite at 0.24 mm with the aligned fillers had an
EMI SE of 81 dB, while the EMI SE of non-aligned composite was 59.2 dB. The alignment increased
interfacial polarization, internal reflections, electrical conductivity, and electronic conduction in axial
[28]
direction of the fiber . PDMS microcells and the continuous PDMS/CNT were chemically bonded to