<i>In-situ</i> derive hierarchical Ti ₃C ₂@C@ZnO heterointerface for electromagnetic absorption enhancement

Heterointerfaces formed by the intimate connection of different materials with electromagnetic losses are expected to achieve stronger electromagnetic (EM) absorption. However, constructing composites with heterointerfaces still faces great challenges in facile preparation process, optimized impedance matching, high reflection loss (<i>R</i>_L), and ultrathin matching thickness. In this work, we develop ZIF-8 functionalized MXene to produce hierarchical Ti₃C₂@C@ZnO composites with heterointerface to advance EM absorption enhancement. Modified with polydopamine (PDA), few-layer Ti₃C₂T_<i>x</i> MXene sheets enable adsorption of Zn²⁺ metal ions on Ti₃C₂T_<i>x</i>@PDA by electrostatic interaction for <i>in-situ</i> growth of ZIF-8. Ti₃C₂/C/ZnO heterointerface were obtained after heat treatment of Ti₃C₂T_<i>x</i>@PDA@ZIF-8 nanocomposites at various temperatures. The Ti₃C₂/C/ZnO-600 °C with 1.15 mm thickness have a <i>R</i>_L of −50.241 dB and an effective absorption bandwidth of 3.50 GHz. In-depth studies on the electromagnetic loss mechanisms reveal that Ti₃C₂, carbon, and ZnO in nanocomposites generate multiple interfacial polarization losses beyond partial conductivity losses caused by Ti₃C₂ and ZnO. Oxygen vacancy defects in ZnO form dipole losses with carbon. This work not only provides a simple and effective concept for preparing MXene@MOFs heterogeneous composites as an ultrathin and strong electromagnetic wave absorber, but also offers a vital guideline to fabricate various metal oxides derived from the MXene and metal-organic frameworks (MOFs) precursors.