The　nano-engineered　cementitious　composites　(NCC)　were　prepared　using　g-C3N4/CoAl-LDH　3　N　4　/CoAl-LDH　nanoflower　(nanoCN/L),　in　combination　with　mineral　admixtures　including　fly　ash　(FA),　metakaolin　(MK),　and　ground　granulated　blast　furnace　slag　(GGBFS).　The　synergistic　effects　and　mechanisms　of　nano-CN/L　and　mineral　admixtures　on　the　mechanical,　chloride　penetration　resistance　and　air　purification　properties　of　NCC　were　investigated.　The　results　show　that　nano-CN/L　promotes　the　early　hydration　of　cementitious　materials　and　improves　the　composition　and　morphology　of　C-S-H　gel.　Furthermore,　the　filling　effect　of　nano-CN/L　significantly　optimizes　the　pore　structure　and　interfacial　crack　width　of　NCC,　thereby　eliminating　the　adverse　impact　of　FA,　MK,　and　GGBFS　on　its　early　mechanical　strengths.　Additionally,　nano-CN/L　enhances　the　chloride　penetration　resistance　and　NOx　x　removal　properties　of　NCC　through　its　strong　ion　adsorption　and　photocatalytic　activity,　respectively.　Incorporating　0.9　%　nano-CN/L　by　mass　of　cementitious　materials　reduces　the　chloride　diffusion　coefficient　of　NCC　at　curing　age　of　56d　by　26.9　%　and　increases　the　NOx　x　removal　ratio　by　11　times.　The　7d＇s　compressive　and　flexural　strengths　of　NCC　increase　by　13.6　%　and　4.6　%,　respectively,　compared　to　the　one　without　nano-CN/L.　As　a　novel　multifunctional　nanomaterial,　nano-CN/L　not　only　provides　a　new　pathway　for　extending　the　service　life　of　cementitious　composites,　but　also　injects　new　momentum　into　their　environmental-friendly　development.