Utilizing MOFs Melt-Foaming\nto Design Functionalized\nCarbon Foams for 100% Deep-Discharge and Ultrahigh Capacity Sodium\nMetal Anodes

Meltable metal–organic frameworks (MOFs) offer\nsignificant\naccessibility to chemistry and moldability for developing carbon-based\nmaterials. However, the scarcity of low melting point MOFs poses challenges\nfor related design. Here, we propose a MOFs melt-foaming strategy\ntoward Ni single atoms/quantum dots-functionalized carbon foams (NiSA/QD@CFs).\nMelt-foaming highly depends on two factors: flexible metal–phosphorus\nbonds with cage-like ligands bridged in a zipper configuration via\nhydrogen bonds, facilitating MOFs conformational melting below 200\n°C, and high annealing rates that lead to MOFs foaming by reducing\nthe energy barrier and enhancing the pyrolysis enthalpy. When used\nas hosts for sodium metal anodes, foam structure regulates metallic\nNa to preferentially deposit inside the pores, while Ni SA and QD\nsynergistically enhance Na absorption. Consequently, NiSA/QD@CF electrodes\nexhibit stable cyclic performance for 1000 h in symmetrical cells,\nwith a low hysteresis voltage of 98 mV at 100 mA/cm<sup>2</sup>, 100\nmAh/cm<sup>2</sup>, and 100% depth of discharge. Moreover, both full\ncells and anode-free ones exhibit excellent rate and cyclic performances.\nThis strategy enriches the liquid MOFs family and their applications\nin mild-processing CFs for electrochemical energy storage.