Heterostructured TiO2/C/Co from ZIF-67 Frameworks for Microwave-Absorbing Nanomaterials

Heterostructured TiO2/C/Co nanomaterial has been derived from a carbonized zeolitic imidazolate (ZIF-67) porous framework. The obtained uniform nanospheres wrapped with TiO2 have shown superior microwave absorption properties. Traditionally, the interaction of phonons within a confined system in terms of microwave absorption has not been studied in the literature to date. Here, we demonstrate that the phonon confinement is pivotal in the improvement of impedance matching, besides the multiple interfacial dielectric relaxations at different dielectric media (TiO2/C, C/Co) in the composite. Because of the specially crafted phonon confinement and multiple interface dielectric relaxations, the as-synthesized (TiO2/C/Co) composite manifests a maximum reflection loss of −42 dB with a broad bandwidth of 5 GHz. This work explains the possible mechanism of electromagnetic shielding in a confined system with multiple interfaces and may lead to design of advanced materials for microwave shielding.