Composition engineering of ZIF-derived cobalt phosphide/cobalt monoxide heterostructures for high-performance asymmetric supercapacitors

•Leaf-like CoPx/CoO heterostructure was synthesized from a ZIF-Co-L precursor.•Synergy of CoPx and CoO guarantees the interfacial property and enhances energy storage.•Controlled phosphidation regulated the bulk/surface composition of CoPx/CoO.•(CoPx)0.9/CoO0.1 showed high capacitance derived from interface-driven metallic Co.•Asymmetric supercapacitor displays high energy density of 12.7 Wh kg−1 at 370 W kg−1.