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Co 9 S 8 nanoparticles embedded in two dimensional/three dimensional (2D/3D) porous carbon foams are synthesized from carbonized melamine foam (CMF) @Co-ZIF-L. Due to the vertical-growth of 2D Co-ZIF-L on the carbonized 3D melamine foam wires, abundant meso- and macropores are formed among Co-ZIF-L nanosheets with sufficient micropores created from the carbonization of ZIF-L; thus 2D/3D carbon foam with hierarchical pores can be obtained. Meanwhile, Co 9 S 8 nanoparticles are formed and uniformly dispersed into porous carbon, and such carbon wrapping can effectively alleviate the volume expansion of metal sulfide; thus high electrochemical performance can be achieved. For example, the specific capacity is as high as 615 mAh g−1 at 500 mA g−1 after 450 cycles, much higher than that of pristine CMF (79.5 mAh g−1). Moreover, due to the excellent flexibility of carbonized melamine foam, such composite can be directly used as free-standing binder-free electrode for lithium ion batteries, which exhibits great potential to be used in wearable electronics. • Co 9 S 8 nanoparticles were embedded in 2D/3D porous carbon foam. • The hybrid composite can be used as free-standing electrode. • The unique porous structure effectively alleviates the volume expansion. [ABSTRACT FROM AUTHOR]

Highly flexible carbon foam with double-layer structure and hierarchical pores is synthesized based on Co-ZIF-L supported on carbonized melamine sponge (MS). Due to the special leaf-like structure of Co-ZIF-L, the uniform in-situ growth of ZIF-L onto carbonized MS makes the three-dimensional carbon wires dendriform-like, which after carbonization and KOH activation, sufficient micro- and mesopores are created resulting from Co-ZIF-L particles and gaps among them. Such hierarchical pore structure significantly improves the specific capacities (238 F/g at 1 A/g compared to that of 92 F/g for carbonized pristine MS). Moreover, due to the excellent mechanical properties inheriting from MS, the obtained sample can be used directly as a flexible electrode and remains high electrochemical performance under different bending states (the capacitance remains 99% and 96.1% respectively when bent at 90° and 180°). When using such foam as all-solid-state supercapacitors, it shows high specific capacity (149 F/g at 5 mV/s), high stability in high operation voltage window (0–1.8 V) and excellent flexibility, which makes such material a potential candidate for high-performance supercapacitors in modern portable and wearable devices. Image 1 • Carbonized melamine sponge@Co-ZIF-L based carbon foam was synthesized. • Such carbon foam has hierarchical pores. • Such carbon foam can be used as flexible free-standing electrode. • Such carbon foam shows good electrochemical performance for supercapacitors. [ABSTRACT FROM AUTHOR]