Constructing　novel　graphic　carbon　nitride　(g-C3N4)-based　nanohybrids　via　a　facile　method　for　high-performance　polymeric　materials　which　exhibit　enhanced　fire　safety　properties　are　highly　desirable.　Here,　the　g-C3N4/carbon　sphere/Cu　(denoted　as　CSACS-C)　nanohybrid　was　prepared　by　metal　ions-induced　gel　reaction　using　sodium　alginate　as　a　green　template,　and　thereafter　introduced　into　thermoplastic　polyurethane　(TPU)　matrix　to　prepare　nanocomposites.　Microstructure　analyses　indicated　the　successful　synthesis　of　the　ternary　nanohybrid,　where　both　the　g-C3N4　nanosheets　and　Cu　nanoparticles　were　well-dispersed　in　the　carbon　material.　Moreover,　the　ternary　nanohybrid　showed　good　distribution　in　TPU　matrices,　and　exhibited　strong　interfacial　adhesion　with　the　polymeric　host.　It　is　worth　noting　that　addition　of　these　nanohybrids　led　to　significantly　improved　fire　safety.　Particularly,　remarkably　reduced　pyrolysis　gaseous　products　generation　and　peak　of　heat　release　rate　were　achieved　for　TPU/CSACS-C　system.　This　enhanced　fire　safety　was　due　to　the　interpretations　that　the　SACS　and　g-C3N4　nanosheets　retarded　the　heat　and　mass　propagation,　while　the　incorporation　of　Cu　nanoparticles　induced　earlier　thermal　decomposition　into　more　char　residues　and　less　pyrolysis　gaseous　products.　The　work　provides　a　new,　simple　strategy　to　prepare　nanohybrids　for　polymeric　materials　with　enhanced　fire　safety.　©　2018　Elsevier　Inc.