Facile and green fabrication of flame-retardant Ti3C2Tx MXene networks for ultrafast, reusable and weather-resistant fire warning

Fire warning sensor capable of rapidly monitoring critical fire risk of combustible materials growingly plays a crucial role in reducing or avioding fire disaster under complicated environments. Unfortunately, to date the rational design of smart fire warning sensors that are reusable and weather-resistant remains a major challenge. Here, we report a facile and green strategy for fabricating biomimetic polyethylene glycol or polyvinyl pyrrolidone polymer decorated Ti3C2Tx MXene networks that possess exceptional flame resistance and sensitive fire cyclic warning performance. Novel fire warning sensors that were constructed based on the as-prepared inherently fire-retardant MXene networks exhibit ultrafast fire warning response and recovery time (~1.8 s and ~1.0 s), resistance switching behavior with >4 orders of magnitude, and stable fire cyclic warning capability for 100 cycles. Structural observation and analysis disclose that, upon flame attack, thermal pyrolysis of the polymer molecules facilitates the oxidation of MXene sheets to form a compact fish scale-like C/N dopped titania network, and meanwhile its electron excitation is thus activated to generate a sensitive resistance transition to trigger a rapid fire cyclic warning signal. More improtantly, the multifunctional MXene networks treated with silane modification not only endow combustible substrate with excellent super-hydrophobicity and outstanding flame resistance, but provide reusable and weather-resistant fire warning responses even after one-year outdoor exposure. Therefore, this work provides an innovative concept of advanced MXene composites and design of fire cyclic warning sensors for fire safety and prevention.