Construction of bimetallic metal-organic frameworks/graphitic carbon nitride hybrids as flame retardant for unsaturated polyester resin

The use of unsaturated polyester resin (UPR) as a composite material is limited by its flammability and smoke generation properties, which pose a threat to human life and public safety. To address these concerns, a Co–Cu bimetallic metal-organic frameworks (MOFs)/graphitic carbon nitride (g-C₃N₄) hybrids (BMCN) were synthesized via a co-precipitation method and incorporated into UPR composites. The addition of 4 wt% BMCN was found to significantly improve the fire safety of the UPR composites based on cone calorimetry tests (CCT), LOI, and UL-94 test. The results showed a decrease in peak smoke generation rate (pSPR) by 50%, peak heat release rate (pHRR) by 43.4%, and total smoke production (TSP) by 32.5%. The efficacy of BMCN in suppressing smoke and heat release was further confirmed through thermogravimetric analysis-infrared spectrometer (TG-IR) testing. The improved compatibility of BMCN with the UPR matrix also enhanced the flame retardancy and mechanical performance of the UPR composites. This study provides valuable insights into the development of g–C₃N₄–based flame retardants and bimetallic metal-doped flame retardants.