Hierarchical Assembly of Ternary MOF‐Derived Sandwich Composites for High‐Efficiency Tunable Electromagnetic Wave Absorption

The proliferation of electronic devices drives the adoption of electromagnetic wave (EMW) absorbing materials to mitigate electromagnetic pollution. Metal‐organic frameworks (MOFs) reveal great potential in EMW absorption field due to their unique pore structure and outstanding physicochemical properties. However, single MOFs are difficult to achieve both efficient absorption and wide frequency coverage owing to the limited electromagnetic properties and structural composition. Herein, a sandwich‐like ternary MOF composite is successfully synthesized through a hierarchical assembly strategy. Following high‐temperature treatment, the materials are converted into nitrogen‐doped porous carbon with magnetic metals, non‐magnetic metal oxides, and carbon nanotubes on the surface (labeled as TiO2/C@Co/N/C@CNT). The unique sandwich structure of the resulting derivatives provides a multi‐level microstructure and multi‐component synergistic effects, significantly enhancing electromagnetic wave absorption capabilities and broadening the effective absorption bandwidth (EAB). At 1.8 mm matching thicknesses, the material achieves a reflection loss of −56.3 dB and a 6.6 GHz EAB. Adjusting the matching thicknesses to 2.3 and 3.1 mm extends the EAB to 6.1–18 GHz, with absorption peaks of −47.6 and −47.1 dB. This work offers a novel guidance for constructing advanced MOF‐derived materials with ultra‐broadband EAB and strong EMW absorption through meticulous structural design and multiple components combination. A sandwich‐like ternary metal‐organic framework (MOF)‐derived composite was synthesized through a hierarchical assembly strategy followed by thermal treatment. Benefiting from microstructure‐guided enhanced loss, improved interfacial polarization and charge migration, synergistic magnetic elements with multiple resonance effects, and optimized impedance matching, the composite achieves a minimum reflection loss of ‐56.3 dB and an effective absorption bandwidth of 6.6 GHz, with tunable performance over a wide frequency.