Defects and interface induced polarization due to morphology regulation based on the synthesis of Zn@Co-ZIFs in different systems to modulate electromagnetic wave absorption performance

Designing the composition and structure of bi-metal hybrids is an available way to regulating the electromagnetic properties. Metal-organic framework (MOFs) materials have attracted profuse attention due to their low density and adjustable structure. Among all MOFs, zeolitic imidazolate framework (ZIFs) is an excellent precursor with diverse morphologies and various structures. This provides great structural designability. In this work, a Zn/Co bi-metal hybrid based on ZIF-8 and ZIF-67 templates was constructed via a novel approach. Solvent environment changing led to changes in morphology and structure. Thus the derivatives exhibited interesting electromagnetic wave (EMW) absorbing properties. In methanol-water mixing ambient solvents of different volume ratio, the Zn@Co-ZIFs present completely different morphologies and topological structures. The corresponding pyrolysis products ZnO/NC@Co/NCs (ZCNCs) inherited the morphologies of precursors and displayed great difference in EMW absorbing properties as a result of variant defects. The ZCNC originated from mixture where methanol volume ratio counted 75% exhibited the best absorption performance: the minimum reflection loss (RL min ) was -48.29 dB, and the effective absorption bandwidth (EAB) was 4.51 GHz (from 10.90 GHz ∼ 15.41 GHz). Besides, ZCNC originated from mixture where methanol occupied 25% of total volume displayed dual-band absorption at 3.6 mm. This work provides a novel perspective for the design of efficient EMW absorbing materials.