Terahertz technology promises broad applications, which calls for terahertz electromagnetic interference (EMI) shielding materials to alleviate radiation pollution. 2D transition metal carbides and/or nitrides (MXenes) with metallic conductivity are promising for EMI shielding, but simultaneously realizing light weight, high stability, and foldability in a MXene shielding material to meet the requirements of increasingly popular portable and wearable equipment has remained a great challenge. Herein, an ion-diffusion-induced gelation method is demonstrated to synthesize free-standing, light-weight, foldable, and highly stable MXene foams, in which MXene sheets are cross-linked by multivalent metal ions and graphene oxide to form an oriented porous structure. The method is highly efficient, controllable, and versatile for scalable generation of functional 3D MXene structures with arbitrary shapes and synergistic properties. The distinctive cross-linked porous structure endows the light-weight MXene foam with good foldability, outstanding durability and stability in wet environments, and an excellent terahertz shielding effectiveness of 51 dB at a small thickness of 85 μm. This work not only provides an insight for the on-target design of high-performance terahertz shielding materials but also expands the applications of MXenes in 3D macroscopic form.
Keywords: MXene foam; gelation; graphene oxide; ion diffusion; terahertz shielding.