Phosphorus- and metal-free flame-retardant strategy based on π-π stacking enables flexible polyurethane sponge with high compression resistance and oil-water separation properties

The development of adsorbent materials capable of withstanding harsh environmental conditions remains a significant challenge. In this study, a novel flexible polyurethane (FPU) sponge composite (PU@BTC-Abz@Si) was successfully fabricated with outstanding flame retardancy, mechanical robustness, and oil-water separation performance. This was achieved by constructing micro-nano structures on the surface of FPU sponge by in situ self-assembly of dendrimers with π-π stacking interactions, and subsequent grafting with polydimethylsiloxane (PDMS). Notably, the synthesis was accomplished without the incorporation of phosphorus or metal-based flame retardants. Instead, PU@BTC-Abz@Si utilizes a flame-retardant strategy based on π-π stacking, imparting fire safety while minimizing secondary environmental pollution. Compared with pristine FPU sponge, PU@BTC-Abz@Si demonstrated significant reductions in total heat release (THR), total smoke production (TSP), and total carbon monoxide production (TCOP) by 55.4%, 51.9%, and 64.9%, respectively. Furthermore, PU@BTC-Abz@Si exhibited enhanced mechanical stability and high oil-water selectivity. This work offers a sustainable and efficient approach to enhance the functional performance of FPU sponge, with promising implications for environmental protection and fire-safe engineering applications.