Unlocking exceptional EMI shielding in Ti₃C₂T _x MXenes through controlled microstructure and surface chemistry

The rapid advancement of highly integrated electronics demands next-generation electromagnetic interference (EMI) shielding materials that combine lightweight, ultrathin, flexible, and mechanically robust properties with exceptional shielding effectiveness (SE) to mitigate signal crosstalk and ensure device reliability. In this work, we demonstrate the fabrication of high-performance EMI shields using highly conductive, additive-free aqueous Ti₃C₂T _x (T = O, OH, Cl, F) MXene dispersions synthesized under both harsh and mild etching conditions. These dispersions were engineered into freestanding thin films and functionalized cotton fabrics via vacuum-assisted filtration, enabling tunable EMI shielding properties through precise control of etchant chemistry, flake size, microstructure, thickness, and MXene loading. The EMI shielding improved with film thickness, and the 13 μm thick film demonstrated exceptional EMI shielding of 60 dB. The freestanding heat-treated Ti₃C₂T _x film with a minimal thickness of 5 μm achieved a remarkable shielding effectiveness of 71 dB (which is 37% higher than that of the untreated film) corresponding to 99.99999% EMI attenuation. This film also exhibited an ultrahigh absolute shielding effectiveness (SSE _T ) of 72 300 dB cm² g^-1, surpassing all previously reported MXene-based shields of comparable thickness. The improved stability was attributed to the thermal conversion of surface OH groups to O-terminations, reducing interflake spacing and enhancing conductivity. The coated cotton fabric achieved an unprecedented SE of 82 dB due to the excellent wave attenuation associated with its porous structure. Notably, the fabric retained its shielding performance even after six months of ambient exposure, highlighting exceptional environmental stability. This study establishes critical structure-property relationships, revealing that induced porosity, meta-structure effects, large flake size, and optimized surface terminations synergistically enhance EMI shielding. By elucidating the interplay between material parameters and shielding performance, this work provides a foundational framework for designing advanced EMI mitigation technologies, paving the way for scalable, high-performance shielding solutions in next-generation flexible and wearable electronics.