Heteroatom‑Doped C@Co₂P Heterostructures for Broadband and High‑Absorption Flexible Porous Microwave Absorbers

Broadband and high‑absorption flexible microwave absorbers are highly desirable in the areas of military, communications, medical, and electronic devices. Herein, the multi-hierarchical heteroatom‑doped carbon@dicobalt phosphide (C@Co₂P) heterostructures with heterogeneous interfaces are successfully developed for broadband and high‑absorption flexible porous microwave absorbers. The zeolitic imidazolate frameworks decorated with poly(cyclotriphosphazene-co-tannic acid-co-4,4'-sulfonyldiphenol) nanobowls (ZIF@PZTS NBs) are synthesized to construct the nitrogen (N), phosphorus (P), and sulfur (S) heteroatom‑doped C@Co₂P heterostructures via high-temperature pyrolysis and in situ phosphidation. The obtained heteroatom‑doped C@Co₂P heterostructures exhibit excellent electromagnetic wave (EMW) absorption performance with a minimum reflection loss (RL_min) of -56.04 dB and a maximum effective absorption bandwidth (EAB) of 8.64 GHz. Subsequently, the broadband and high‑absorption flexible porous C@Co₂P/PDMS composites are developed by integration of C@Co₂P heterostructures and polydimethylsiloxane (PDMS) combined with the sacrificial template method. The flexible porous C@Co₂P/PDMS composites exhibit an RL_min of -53.72 dB, with the full X-band coverage achieved at 8.1 mm, while 75% of the X-band is effectively covered at 2.7 mm, owing to the synergetic mechanisms including dielectric losses, magnetic losses, and multiple reflections and scattering. Therefore, the broadband and high‑absorption flexible porous microwave absorbers containing heteroatom‑doped C@Co₂P heterostructures have excellent application potential for military, communications, medical, and electronic devices.