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Page 12 of 28 Wang et al. Soft Sci. 2026, 6, 8

EAB of 8.82 GHz. Additionally, the first-principles calculations and far-field simulations comprehensively
validated the contribution of the hetero-atom doping to the microwave absorption performance.

The natural biomass materials, such as chitosan , sodium alginate [96,97] , gelatin [98,99] , and carrageenan , are
[95]
[100]
commonly used as carbon-based precursors for preparing 3D carbon aerogels due to their wide availability
from natural sources, including shrimp, crabs, insects, and mollusks. Chitosan’s molecular chains are rich in
amino groups, providing exceptional metal ion capture capabilities and enabling the formation of magnetic
carbon-based aerogels. Similarly, the remarkable biocompatibility of sodium alginate, an environmentally
friendly carbohydrate extracted from seaweed, allows the formation of a stable gel network upon
cross-linking with metal ions, making it an ideal precursor for synthesizing interconnected carbon
frameworks. In addition, the nitrogen present in these biomolecules facilitates effective heteroatom nitrogen
doping in the carbon framework, thereby enhancing dielectric loss.

Luo et al. grew 0D magnetic cobalt nanoparticles onto a chitosan-derived nitrogen-doped carbon framework
via a simple liquid reaction, freeze-drying, and calcination process . The resulting Co/C aerogel exhibited a
[101]
dielectrically and magnetically coupled network under optimal cobalt content conditions, achieving a
minimum RL of -44.70 dB at a thin thickness of 1.35 mm and a maximum EAB of 5.45 GHz at a thickness of
only 1.5 mm. Peng et al. synthesized lightweight porous Fe O -Fe/carbon aerogels (FFCA) by depositing
3
4
magnetic metals onto a chitosan-reinforced carboxymethyl cellulose matrix with different carbonization
temperatures [102] . The 3D porous structure and non-homogeneous interconnected conductive framework
endowed the carbon-based aerogel with outstanding characteristics. Specifically, the incorporation of
magnetic materials and carbonization at gradient temperatures enabled tunable EM parameters and excellent
impedance matching. The resulting FFCA-900 aerogel exhibited outstanding RL intensity of -45.5 dB at
2.6 mm and an EAB of 3.7 GHz. Guo et al. successfully constructed carbon-based aerogels by in situ growth
of CNTs via chemical vapor deposition and freeze-drying, effectively enhancing polarization relaxation and
optimizing impedance matching, achieving a remarkable RL of -51.6 dB and a wide EAB of 5.9 GHz .
[103]

Carbon materials with sp graphitized structure, such as graphene [104] and CNTs [105] , are commonly used as
2
raw materials for constructing aerogels due to their intrinsic electrical conductivity and abundant functional
groups. Wang et al. prepared the reduced graphene oxide (RGO)-based composite aerogel modified by
nickel nanoparticles from different contents of graphene oxide (GO) nanosheets and nickel-based
metal-organic frameworks after freeze-drying and high-temperature pyrolysis, which exhibited high porosity
and low density [106] . When the content of GO nanosheets was rationally regulated, both the pore structure
and the dielectric loss properties could be tailored, which can effectively enhance the overall dissipating
capability of RGO-based aerogel, thereby broadening the EAB to 5.2 GHz with a promising thickness of 1.5
mm. Besides, Shu et al. prepared 3D porous Co and CoO-loaded RGO aerogels by freeze-drying and
high-temperature reduction techniques [107] . By controlling the pore structure, EM parameters could be
effectively adjusted, achieving the minimum RL value and EAB of -61.8 dB and 4.2 GHz, respectively.

Directional freeze-drying strategy
The conventional freeze-casting method typically involves the solidification of a carbon-containing solution
in a uniformly low-temperature environment. Owing to isotropic ice nucleation and an uncontrolled
crystallization process, both the orientation and the morphology of the resulting ice crystals are difficult to
control, leading to a disordered and unpredictable porous microstructure. In contrast, directional freezing
strategy enables the construction of highly ordered pore architectures through the templating effect of
unidirectionally growing ice crystals under a controllable thermal gradient, which facilitates the rational
design of aligned porous frameworks in carbon-based aerogels with tunable EM response characteristics
effectively .
[108]