Form-stable　composite　phase　change　material　(PCM)　with　high　latent　heat　is　widely　used　in　thermal　energy　storage　application.　The　skeleton　structure　and　thermophysical　properties　of　the　supporting　material　are　greatly　important　to　the　energy　efficiency　of　the　composite　PCM.　This　work　is　to　design　the　supporting　material　with　specific　3D　carbon　framework　for　composite　PCMs　using　the　CaCO3-templated　assembly　technique,　following　to　explore　the　electro-heat　conversion　ability　of　composites.　Microcrystalline　graphite　is　used　as　the　skeleton,　CaCO3　as　the　template,　and　monocrystal　white　sugar　as　the　carbon　source.　By　designing　the　content　of　template,　the　3D　framework　structure　of　supports　can　be　tailored.　Results　show　the　designed　support　material　has　a　higher　cumulative　pore　volume　than　the　raw　material　of　64　%,　leading　to　an　increment　of　the　loading　capacity　of　12–20　%,　due　to　the　formation　of　the　cotton-shaped　carbonization　connection　products.　Then,　the　stearic　acid-type　composite　shows　the　thermal　conductivity　is　improved　by　104.86　%　than　the　pure　PCM,　causing　faster　heat　storage　and　release　rate.　At　last,　it　proved　that　the　electro-heat　conversion　of　the　composite　can　be　achieved　at　low　trigger　voltage.　The　conversion　efficiency　increases　with　the　voltage　rising　and　the　bulk　density　improving,　reaching　to　75.61　%　at　a　voltage　of　4.5　V　with　a　bulk　density　of　0.774　g　cm−3.　©　2022　Elsevier　Ltd