In　this　work,　a　metal　organic　framework　(Fe-MOF)　with　the　effect　of　absorbing　toxic　gases　and　good　compatibility　was　synthesized　by　chelating　a　novel　organic　ligand　contained　carbonization　groups　(reacted　by　tris(hydroxymethyl)　aminomethane　and　1,4-piperazine　dialdehyde)　with　iron　salt.　Then,　it　was　used　as　the　synergist　to　improve　the　efficiency　of　intumescent　flame　retardant　(IFR)　within　polystyrene　(PS)　substrate.　With　the　addition　of　20%　IFR　and　2%　Fe-MOF,　the　obtained　PS　composites　exhibited　a　limiting　oxygen　index　(LOI)　value　of　28.3%　and　a　UL　rating　of　V-0.　Moreover,　the　peak　heat　release　rate　(pHRR),　total　heat　release　(THR),　and　total　smoke　production　(TSP)　of　PS　composites　were　decreased　by　77.6%,　35.2%,　and　33.7%,　respectively.　According　to　the　mechanism　analysis,　it　was　found　that　Fe-MOF　mainly　acted　in　the　condensed　phase,　contributing　to　the　existence　of　dense　char　residues　with　the　presence　of　IFR　system.　In　addition,　the　good　compatibility　of　organic　ligand　in　Fe-MOF　with　PS　substrate　could　partially　alleviate　the　deterioration　of　mechanical　properties　due　to　the　addition　of　IFR.　For　PS-20%IFR/2%Fe-MOF,　the　impact　strength　was　improved　from　1.7　kJ/m2　(PS-22%IFR)　to　2.2　kJ/m2,　the　tensile　strength　was　also　increased　from　21.3　MPa　(PS-22%IFR)　to　22.4　MPa.　©　2023　John　Wiley　&　Sons　Ltd.