Diisocyanate-induced covalent cross-linking of MXene frameworks for electrically and mechanically robust EMI shielding films

MXenes, two-dimensional transition metal carbides, nitrides, and carbonitrides, have emerged as versatile materials with remarkable physicochemical properties. However, their vulnerability to delamination or degradation in humid or liquid environments poses challenges for long-term stability. In this study, we present a novel approach to enhance MXene stability by synthesizing electrically conductive frameworks through covalent cross-linking using diisocyanates such as 1,4-phenylene diisocyanate (PDI) and hexamethylene diisocyanate (HDI). The resulting frameworks exhibit well-aligned MXene sheets covalently bonded throughout the film. The frameworks not only retained high electrical conductivity but also exhibited improved tensile strength and elongation at break compared to pristine MXene films. Moreover, the frameworks demonstrated exceptional stability under ultrasonic treatment in water, showing their enhanced structural durability. The chemically cross-linked MXene frameworks exhibited hydrophobicity and resistance to water, which contributed to their prolonged chemical stability as well. EMI shielding performance at Ka-band and X-band frequencies was comparable to pristine MXene films, in which SET values around 60 dB were retained in oxidative environments over a week these findings open avenues for the development of robust MXene-based materials with enhanced stability for diverse applications, including electromagnetic interference shielding.