Spatially Decoupled Polysulfide Trapping and Catalytic Conversion in Pyridine-Rich Covalent Organic Framework for...

The lithium polysulfide (LiPS) shuttle and sluggish redox kinetics remain major challenges for rechargeable Li-S batteries. Herein, a Lewis-basic pyridine-rich covalent organic framework (PCOF) is developed as a dual-functional host that enables effective LiPS trapping and catalytic conversion. Elemental sulfur-loaded PCOF (S@PCOF) and atomically Co-coordinated PCOF-derived framework (Co@PCOF) are synthesized and integrated to construct a Li-S cathode with spatially separated active sites. PCOF exhibits stronger binding affinity and faster binding kinetics for LiPS than pyridine-free COF (BCOF) with an identical imine content, highlighting the role of pyridine groups in LiPS trapping. Moreover, density functional theory (DFT) calculations reveal a lower energy barrier for the potential-determining step (Li₂S₂ → Li₂S) on PCOF than on BCOF, originating from its higher p-band center. The Co@PCOF-integrated PCOF cathode delivers the highest Li₂S nucleation and dissolution capacities with accelerated kinetics, enabling highly reversible sulfur redox reactions. Full cells employing the S@PCOF+Co@PCOF cathode exhibit a high discharge capacity (952 mAh g^-1), superior Coulombic efficiency (98%), excellent long-term cycling stability, and robust rate performance across various C-rates. This work provides a rational design strategy for spatially separating LiPS trapping and catalytic sites in pyridine-rich COF cathodes, offering new insights into the development of high-performance Li-S batteries.