A novel strategy for efficient fire and smoke safety of epoxy composites based on ferrocene@cucurbituril[n] host–guest structures

Designing composite structures with simultaneous fire and smoke suppression remains challenging due to the stage-dependent pyrolysis behaviors of polymer composites during combustion. Herein, a ferrocene@cucurbituril[n] (Fc@(CB) n ) host–guest system was fabricated via a simple, green, and spontaneous self-assembly strategy and incorporated into epoxy resin as an efficient additive. With only 2 wt% Fc@(CB) n , the limiting oxygen index of the epoxy increased significantly from 23.0% to 27.5%, while the peak heat release rate, total heat release, total smoke release, and CO/CO 2 ratio were reduced by 16%, 29%, 26%, and 26%, respectively. Mechanistic investigations revealed a hierarchical combustion-catalysis behavior across different fire stages. In the gas phase at lower temperatures, iron- and aromatic-derived radicals efficiently scavenged high-energy H· and OH· radicals, suppressing flame propagation. At elevated temperatures, cucurbituril cavities adsorbed small-molecule pyrolysis gases, while ferrocene generated active iron radicals that catalyzed smoke suppression. Notably, in the condensed phase, a continuous and thermally stable char layer composed of (CB) n and Fc@(CB) n was formed for the first time, acting synergistically as a carbonization catalyst and phase-transfer medium to effectively block heat, oxygen, and mass transfer. This work elucidates a multilevel flame-retardant and smoke-suppressive mechanism enabled by host–guest chemistry and provides a novel strategy for developing high-performance fire-safe epoxy composites for architectural, transportation, and electronic applications.