Lithium-sulfur batteries (LSBs) exhibit significant potential as high-energy-density storage systems for next-generation applications. However, the polysulfide shuttling effect and the growth of lithium dendrites significantly hinder the commercialization of LSBs. To address these challenges, we synthesized an amide-rich covalent organic framework (COF-316-CONH2) to modify polypropylene (PP) separators, achieving three key functions: inhibiting polysulfide shuttling, facilitating polysulfide conversion, and regulating lithium ion (Li+) transport. The abundant amide groups in COF-316-CONH2 anchor polysulfide anions through electrostatic interactions and facilitate their in-situ transformation with the help of carbon, thereby enhancing the utilization rate of active materials. Moreover, density functional theory (DFT) calculations demonstrate that the ordered nanoscale pores and amide groups in COF-316-CONH2 exhibit excellent Li+ desolvation properties, thereby improving the rate and uniformity of Li+ transfer. The modified Li-Li symmetric battery delivers stable cycling for over 1500 h with a low voltage hysteresis of 0.015 V, demonstrating effective dendrite suppression. Furthermore, LSBs assembled with COF-316-CONH2 separator show outstanding electrochemical performance, retaining high discharge capacities of 646 mAh g-1 after 600 cycles. This study provides new insights into the rational design of separators for LSBs.