Graphitic　carbon　nitride/organic　aluminum　hypophosphites　(g-C3N4/OAHPi)　hybrids,　i.e.,　CPDCPAHPi　and　CBPODAHPi,　were　synthesized　by　esterification　and　salification　reactions,　and　then　incorporated　into　polystyrene　(PS)　to　prepare　composites　through　a　melt　blending　method.　Structure　and　morphology　characterizations　demonstrated　the　successful　synthesis　of　PDCPAHPi,　BPODAHPi　and　their　hybrids.　The　g-C3N4　protected　OAHPi　from　external　heat　and　thus　improved　the　thermal　stability　of　OAHPi.　Combining　g-C3N4　with　OAHPi　contributed　to　reduction　in　peak　of　heat　release　rate,　total　heat　release　and　smoke　production　rate　of　PS　matrix.　Reduced　smoke　released　has　also　been　demonstrated　by　smoke　density　chamber　testing.　Additionally,　introduction　of　the　hybrids　led　to　decreased　release　of　flammable　aromatic　compounds.　These　properties　improvement　could　be　attributed　to　gas　phase　action　and　physical　barrier　effect　in　condensed　phase:　phosphorus-containing　low-energy　radicals　generated　from　OAHPi　effectively　captured　high-energy　free-radicals　evolved　from　PS;　g-C3N4　nanosheets　retarded　the　permeation　of　heat　and　the　escape　of　volatile　degradation　products.　Therefore,　g-C3N4/OAHPi　hybrids　will　provide　a　potential　strategy　to　reduce　the　fire　hazards　of　PS.　(C)　2017　Elsevier　B.V.　All　rights　reserved.