Regulating phosphorus distribution between gas and condensed phases via TiMOFs-modified black phosphorus for enhanced thermal stability and fire safety of polycarbonate

Building fires remain a critical global threat, necessitating advanced strategies to stabilize polycarbonate (PC) against thermal degradation. Inspired by the natural phosphorus cycle, we report a "phosphorus fixation" strategy to modulate the decomposition pathways of PC. By in-situ anchoring MIL-125(Ti) onto black phosphorus (BP) nanosheets, a hybrid black phosphorus-MIL-125(Ti) (BP-TiMOFs) flame retardant was synthesized and characterized. At a minimal loading of 2.0 wt%, BP-TiMOFs remarkably enhanced the thermal oxidative stability, increasing the initial decomposition temperature (T -1% ) by 54.95 °C. More importantly, it achieved a 78.22% reduction in peak heat release rate (PHRR) and significantly suppressed smoke and toxic gas emissions. Systematic mechanistic studies reveal that the Ti cations effectively "fix" the volatile phosphorus fragments into the condensed phase, triggering a robust phosphorus fixation effect and forming a stable protective layer. This work provides molecular-level insights into how metal-coordinated phosphorus regulates the distribution of degradation products between the gas and condensed phases, offering a robust template for designing high-performance fire-safe polymers.