Preparation of a\nCobalt-Based Metal–Organic\nFramework and Its Application as a Synergistic Flame Retardant in\nEpoxy Resins

A cobalt-based organic framework (PNCo-MOF) was prepared\nusing\na phosphonate and triazole containing binary carboxylic acid ligand\nas an organic ligand, which coordinated with Co(NO<sub>3</sub>)<sub>2</sub>·6H<sub>2</sub>O. The potential of PNCo-MOF as a synergistic\nflame retardant was examined, and EP@APP/PNCo-MOF composites were\nformed by combining PNCo-MOF with ammonium polyphosphate (APP) into\nthe epoxy (EP) matrix. The findings revealed that the EP composite\nwith 2 wt % PNCo-MOF and 8 wt % APP (EP@8APP/2PNCo-MOF sample) displayed\nsuperior flame retardant, mechanical, and dielectric properties. In\ncomparison to the neat EP, the peak heat release rate (PHRR), total\nheat release (THR), and total smoke production (TSP) of the EP@8APP/2PNCo-MOF\nsample decreased by 78.7%, 60.8%, and 49.0%, respectively. Furthermore,\nit achieved a V-0 rating in the UL-94 tests. Because of the synergistic\neffect of APP and PNCo-MOF, EP@8APP/2PNCo-MOF exhibited a higher LOI\nvalue and lower PHHR, THR, and TSP values than the EP composite containing\n10 wt % APP (EP@10APP sample). Additionally, the addition of PNCo-MOF\nimproved the dispersion of APP into the EP matrix, leading to enhanced\nmechanical properties of the EP composites. Overall, this study provided\nan effective approach for developing MOF-type synergistic flame retardants\nto improve the flame retardancy and physical properties of polymeric\nmaterials.