Magnetic-Dielectric Synergetic Strategy for Broadband Microwave Absorption via the Coupling of Flower-Shaped Fe₃O₄ and Conductive Cu/AgHT-NH₂

Achieving broadband microwave absorption requires an optimal balance between conductive loss and magnetic loss. Here, the electrical conductivity of semiconductive MOFs (Cu/AgHT-X, X = –NH₂, –NO₂, and –COOH, HT = benzenethiol) is tuned with different electrophilic substituents via a Schlenk reaction, allowing for effective magnetoelectric coupling and impedance matching, thereby enhancing microwave absorption. Compared to the –COOH and –NO₂ induced semiconductive CuHT–COOH (minimum reflection loss, RL_min = −4.75 dB, 5.0 mm) and CuHT-NO₂ (RL_min = −8.19 dB, 2.8 mm), an enhancement of RL_min of –NH₂ (−37.72 dB, 4.5 mm) facilitates the microwave absorption. The Fe₃O₄/CuHT-NH₂ composite is prepared with coupling flower-shaped Fe₃O₄ nanoparticles (<2 µm) and CuHT-NH₂. The Fe₃O₄/CuHT-NH₂-50% exhibits an effective absorption bandwidth (EAB) of 4.46 GHz at 1.9 mm and a RL_min of −45.73 dB at a thickness of 3.8 mm at room temperature, which is higher than that of the unadulterated CuHT-NH₂ (EAB = 2.71 GHz). By combining the magnetic losses from Fe₃O₄ particles with the resistance losses from Cu─S bonds, the broadband microwave absorption of the composites is enhanced. This work provides fundamental material insights for developing next-generation materials aimed at electromagnetic pollution mitigation.