Ethylenediamine-intercalated black phosphorus nanosheets (eda-BP NSs) were synthesized via a solvothermal process on a 50-g scale. In contrast to the bare black phosphorus nanosheets (BP NSs) which typically involves high-cost gas-phase synthesis and subsequent complex exfoliation process, eda-BP NSs exhibit superior environmental stability and offer greater potential for industrial application in flame retardancy. A series of eda-BP NSs/waterborne polyurethane (WPU) composites with various loadings were prepared, and their flame-retardant properties were evaluated using thermogravimetric analysis, cone calorimetry, and limiting oxygen index (LOI) measurements. With the incorporation of only 0.2 wt.% eda-BP NSs, the composite showed 40.79% reduction in peak of heat release rate, 55.44% decrease in peak of smoke production rate, and 22.5% reduction in total smoke production, along with 2.5% increase in LOI and 2.17 wt.% rise in residual char compared to pure WPU. At the same filler loading, the flame-retardant performance of eda-BP NSs/WPU composites was comprehensively superior to that of BP NSs/WPU. The enhanced flame retardancy is attributed to the unique quasi-monolayer intercalation structure of eda-BP NSs and a phosphorus-nitrogen synergistic mechanism facilitated by the amine groups. The outstanding flame-retardant behavior observed in WPU underscores the promise of this organic–inorganic intercalated phosphorus material for broadening application prospects. Furthermore, such a flame-retardant mechanism arising from this distinctive intercalation structure may provide valuable insights for the development of next-generation flame retardants.

Flexible inorganic double helical semiconductors similar to DNA have fueled the demand for efficient materials with innovative structures and excellent properties. The recent discovery of tin phosphide iodide (SnIP), the first carbon-free double helical semiconductor at an atomic level, has opened new avenues of research for semiconducting devices such as thermoelectric and sensor devices, solar cells, and photocatalysis. It has drawn significant academic attention due to its high structural flexibility, band gap in the visible spectrum range, and non-toxic elements. Herein, the recent progress in developing SnIP, including its prestigious structure, versatile and intriguing properties, and synthesis, is summarized. Other analogues of SnIP and SnIP-based hybrid materials and their applications in photocatalysis are also discussed. Finally, the review concludes with a critical summary and future aspects of this new inorganic semiconductor.