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Flexible, ultralight, and mechanically robust electromagnetic interference (EMI) shielding materials are urgently demanded to manage the increasing electromagnetic radiation pollution, but it remains a great challenge to simultaneously achieve ultralight yet mechanically robust properties while retaining high-efficiency EMI shielding performance. Herein, we fabricate a novel waterborne polyurethane/Ti 3 C 2 T x MXene/nickel ferrite (WPU/MXene/NiFe 2 O 4 ) hybrid aerogel by constructing a strong chemical bonding interaction between an NCOterminated WPU prepolymer and hydroxyl functionalized MXene nanosheets. The resultant aerogels exhibit remarkable lightweight and mechanical properties, particularly high compressive stress far exceeding that of other MXene-based and WPU-based porous materials. Furthermore, synergistic effects of the oriented porous architecture and the multiphase skeleton endow the hybrid aerogels with a high Xband EMI shielding effectiveness (SE) of 64.7 dB at a low density of ∼38.2 mg/cm 3 . The corresponding specific SE value achieves 1694−3124 dB•cm 3 /g, and the SSE/d is up to 15,620 dB•cm 2 /g, surpassing that of most reported EMI shielding materials. Importantly, this aerogel, with excellent electromagnetic radiation protection effects and shielding reliability, is highly promising for long-term and effective EMI shielding service in various application environments.

Gao et al. creatively designed a flexible, superhydrophobic, and highly conductive composite based on non-woven polypropylene fabric for EMI shielding. [7] The introduction of conductive materials on textiles' surface is an effective approach to impart EMI shielding performance while maintaining the features of textiles. [8,9] Previously, interfacial metallization, [10-12] electroless plating, [13] and dip-coating [14] have been applied in the fabrication of EMI shielding textiles. However, these methods tend to use higher content of conductive fillers in polymers with a large thickness, which inevitably causes the EMI shielding materials stiff and heavy, and greatly limited their practical applications. [15,16] It is imperative to develop a novel protective fabric accomplishing with high-level shielding effect and proper flexibility with ultralow thickness. To date, carbonbased materials (graphene oxide, reduced graphene, and 1D carbon nanotubes), [1,7] conductive polymers (polypyrrole and polyaniline (PANI)), [6] and 2D transition MXenes [17] are promising candidates due to their lightweight and good electrical conductivity. Among them, 2D Ti 3 C 2 T X-type MXene nanosheets have certain superiority compared to its counterparts owing to the layered structure, excellent mechanical properties, high metallic conductivity, and polar surfaces. The research of Geng et al. reported that the EMI-shielding effectiveness (SE) of asprepared flexible and highly conductive Ti 3 C 2 T X MXene coated cotton fabric could reach 48.9 dB, which was suitably applied in wearable smart electronics. [18] For instance, Kanthasamy's group also fabricated a coral-like MXene-carbon nanotubes composite textile by a filtration technique and spray coating process, and this lightweight nanocomposite showed excellent EMI SE (50.5 dB) and thermal stability, considered as a potential EMI shielding product. [19] Even then, it is still a huge challenge to achieve the outstanding EMI shielding performance based on textiles with MXene. The design to combine 1D nanowires with 2D MXene nanosheets aims to construct a proper conductive network on the surface of textiles, in which the nanowires can act as interfaces for charge polarization and also as the linkage of MXene to ensure excellent EMI shielding performance. For example, Liu et al. successfully prepared a multifunctional EMI shielding composite textile with biomimetic leaf-like nanostructures by alternatively loading 1D silver nanowires and MXene

Although two-dimensional transition-metal carbides (MXenes) and intrinsic conductive polymers have been combined to produce functional electromagnetic interference (EMI) shielding composites, acid/alkali-responsive EMI shielding textiles have not been reported. Herein, electrically conductive polyaniline (PANI)/MXene/cotton fabrics (PMCFs) are fabricated by an efficient vacuum filtration-assisted spray-coating method for acid/alkali-responsive and tunable EMI shielding applications on the basis of the high electrical conductivity of MXene sheets and the acid/alkali doping/de-doping feature of PANI nanowires. The as-prepared PMCF exhibits a sensitive ammonia response of 19.6% at an ammonia concentration of 200 ppm. The high EMI shielding efficiency of ∼54 dB is achieved by optimizing the decorated structure of the PANI/MXene coating on the cotton fabrics. More importantly, the PMCF can act adaptively as a “switch” for EMI shielding between the efficient strong shielding of 24 dB and the inefficient weak shielding of 15 dB driven by the stimulation of hydrogen chloride and ammonia vapors. This multifunctional fabric would possess promising applications for intelligent garments, flexible electronic sensors, and smart electromagnetic wave response in special environments.

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