Yolk–Shell CoNi@N‑Doped Carbon‑CoNi@CNTs for Enhanced Microwave Absorption, Photothermal, Anti‑Corrosion, and Antimicrobial Properties

• Hierarchical cubic sea urchin-like yolk-shell CoNi@NC-CoNi@CNTs mixed-dimensional MCNCs with tunable CNTs content were selectively synthesized via a combined PBA-derived and catalytic CVD strategy. • The unique hierarchical structure imparts excellent microwave absorption with RLmin of −71.70 dB at 2.78 mm and RCS reduction of −53.23 dB m2. • The MCNCs exhibit multifunctional properties including photothermal conversion, antimicrobial activity (~84.03% at 1 mg·mL−1), and anti-corrosion performance. • This work provides a generalizable route to fabricate multifunctional magnetic carbon-based nanocomposites for applications in complex environments.