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• BPNSs and RGO were combinated via stable chemical bonds. • BP-RGO nanohybrids showed remarkable decrease in PHRR, THR. • BP-RGO nanohybrids exhibited a significant inhibitory effect on smoke and toxic gases. • EP/BP-RGO nanocomposites exhibited high air stability The black phosphorus (BP) can be compounded with other two-dimensional materials with flame retardant effect to achieve better synergistic effect. Herein, the multifunctional BP-RGO nanohybrids was fabricated by solvothermal strategy to improve the dispersion state of BP in epoxy resin (EP) and enhance its fire safety performance, where the reduced graphene oxide (RGO) was attached on the surface of BP via P C and P O C bonds. With the incorporation of 2.0 wt% BP-RGO into EP matrix, 54.4 % reduction in total heat release (THR) was achieved along with 55.2 % decrease in peak heat release rate (PHRR) compared with neat EP. As a similar trend, the toxic CO and aromatic compounds were significantly inhibited, and the maximum decrease (28.5 %) in total smoke production (TSP) was achieved, indicating the enhanced fire safety performance of EP nanocomposites. These positive results is attributed to the synergistic effect of physical nano-barrier, free radicals trapping and char formation between BP and RGO components. Meanwhile, the EP/BP-RGO2.0 nanocomposites exhibited satisfying air stability even after being immersed in water for a month. This work enriches the strategies for enhancing the air stability of BP, and confirms its potential for smoke toxicity and fire hazard suppression in polymer nanocomposites. [ABSTRACT FROM AUTHOR]

• Cuprous oxides with sheet morphology (Mn@Cu 2 O-M nanosheets) are rationally designed and successfully prepared. • The prepared Mn@Cu 2 O-M sheets could endow epoxy composites with high flame retardancy and smoke suppression properties. • The mechanism are probably due to the physical barrier effect and catalytic carbonization awarded by Mn@Cu 2 O-M sheets. To date epoxy resins have been extensively used in the field of chemical engineering, aerospace and building materials. Nevertheless, the utilization of flammable epoxy resins has posed a huge threat to lives and properties, which restricted their applications. In this work, manganese-based cuprous oxides two-dimensional nanosheets (Mn@Cu 2 O-M) are rationally designed and successfully prepared to improve the toxic effluent elimination of epoxy resin. The fire safety properties of the prepared Mn@Cu 2 O-M based nanocomposites improved the heat release rate (<35 %) and total heat release (<40 %) compared to the control epoxy. Moreover, the production of smoke and toxic volatiles of the composites with Mn@Cu 2 O-M nanosheets is significantly reduced. The mechanism investigations indicate that the improved flame retardancy and toxic effluent elimination of epoxy composites are attributed to the physical barrier effect and catalytic carbonization awarded by Mn@Cu 2 O-M nanosheets during burning. This work provides a promising strategy to develop eco-friendly, efficient and fire-safe polymers by both physical barrier effect and catalytic carbonization. [ABSTRACT FROM AUTHOR]

• The ambient stability was imparted to BP nanosheets. • The radicals quenching effect of TA was developed to reduce the CO release. • The flame retardancy and toxic gases suppression of BP nanosheets was explored. Herein, as a natural antioxidant, tannin (TA) is firstly used to functionalize black phosphorous (BP) nanosheets to improve the ambient stability and toxic suppression, thus decreasing the fire hazards of polymer materials. Compared to pure BP nanosheets, higher temperature for thermal oxidation decomposition is achieved for TA-BP nanosheets, directly confirming the ambient stability of TA-BP nanosheets. Meanwhile, from high resolution TEM and XPS results, TA-BP nanosheets after being exposed at air for 10 days present well-organized crystal structure and low PO x bonds content. Cone calorimeter results illustrate that the incorporation of 2.0 wt% TA-BP nanosheets significantly decreases the peak value of heat release rate (−56.5 %), total heat release (−43.0 %), CO 2 concentration (−57.3 %) of TPU composite. Meanwhile, with addition of low to 1.5 wt%, the release of highly-toxic CO gas is significantly suppressed, confirmed by lower peak value (0.52 mg/m3) and decreased total release amount (−55.1 %). The obviously enlarged tensile strength (36.7 MPa) and desirable elongation at break (622 %) are also observed. This strategy not only firstly adopts bio-based antioxidant to impart excellent environmental stability for BP nanosheets, but also promotes the promising potentials of BP nanosheets in the fire safety application of polymer composites. [ABSTRACT FROM AUTHOR]

• BP nanosheets and MCNTs were combinated via stable phosphorus carbon bonds. • EP/BP-MCNTs exhibits low PHRR, THR, SPR, TSR, FGI and smoke toxicity. • BP-MCNTs possessed naao-barrier, synergistic charring and radicals trapping effect. • MCNTs bonding and EP matrix wrapping improve the air-stable of EP/BP-MCNTs. As a rising star of two-dimensional material, black phosphorus (BP) has attracted tremendous attention in applications of photovoltaics, transistors and batteries due to its unique characteristics. Inspiring, we developed a simple strategy to fabricate BP-MCNTs as highly promising inorganic phosphorus-based flame retardant. After incorporation 2 wt% BP-MCNTs11(the mass ratio of BP:MCNTs=1:1) nanohybrid, the peak of heat release rate and total heat release of EP nanocomposites reduced by 55.81% and 41.17% at a phosphorus content of only 1 wt%, and the comprehensive index FGI for evaluating the flame retardant of materials decreased from 17.35 to 6.97. In addition, the typical flammable volatile are suppressed significantly, and the first stage of carbon monoxide release is disappeared. The improvement of fire safety and inhibition of smoke toxicity could be attributed to the the synergistic effects of nano-barrier, catalytic charring and radicals trapping of BP-MCNTs nanohybrid. More importantly, BP hybrid with MCNTs and wrapped in EP matrix which formed effective isolation protection against the ambient degradation. Raman spectra and SEM results confirmed that EP/BP-MCNTs performed enhanced ambient stability than EP/BP-BS nanocomposites after three months. This study demonstrates its great potential for preparation of air-stable BP based nanocomposites with enhanced fire safety. [ABSTRACT FROM AUTHOR]