Dual-Level Engineering of MOF-Derived Hierarchical Porous Carbon Nanofibers with Low-Coordinated Cobalt Single-Atom Catalysts for High-Performance Lithium–Sulfur Batteries

Abstract Carbon-supported single-atom catalysts (SACs) with metal-N moieties have garnered significant attention for their ability to enhance redox kinetics and suppress the dissolution of lithium polysulfides (LiPSs) in lithium–sulfur (Li–S) batteries. However, fully harnessing the catalytic potential of these SACs requires simultaneous optimization of the carbon substrate structure and modulation of the SACs coordination environment—a challenging feat. We propose a metal–organic framework-engaged dual-level engineering strategy to fabricate a hierarchical porous carbon nanofiber with low-coordinated SACs (CoSA/p-CNF). This strategy integrates both macro- and micro-level designs, resulting in a hierarchical pore structure that enhances ionic conductivity and electrolyte wettability, while providing highly active, low-coordinated Co–N 3 moieties for efficient LiPS adsorption and conversion. Consequently, the CoSA/p-CNF demonstrates a high capacity of 917.7 mA⋅h⋅g −1 with excellent retention (95.3% after 300 cycles at 0.5 C) and outstanding rate performance (745 mA⋅h⋅g −1 at 4.0 C). Under demanding conditions, the Li–S cell with CoSA/p-CNF exhibits exceptional electrochemical performance (858 mA⋅h⋅g −1 at 0.5 C with a sulfur loading of 3.8 mg⋅cm −2 ). X-ray absorption spectroscopy and density functional theory calculations confirm that the low-coordinated Co–N 3 moieties effectively adsorb and convert LiPSs, offering a practical solution to enhance sulfur redox kinetics in Li–S batteries. Graphical Abstract