Lithium–sulfur batteries are recognized as promising next-generation energy storage systems owing to their ultrahigh energy density and abundant sulfur reserves. However, their practical applications are severely hindered by the polysulfide shuttle effect, sluggish reaction kinetics, and poor cycling stability at high rates. Herein, phosphorus-doped MoS2/MXene composites are synthesized via a hydrothermal method combined with a gas-phase phosphorization process and used as a functional coating to modify commercial polypropylene (PP) separators. Phosphorus doping effectively expands the interlayer distance of MoS2 and introduces abundant defective active sites, which significantly enhance the polysulfide adsorption capability and bidirectional electrocatalytic activity. Meanwhile, the wettability of the separator and the polysulfide blocking effect are also improved. Electrochemical measurements demonstrate that the P-MoS2/MXene modified separator effectively suppresses the shuttle effect and reduces battery polarization. The assembled cell delivers a high specific capacity of 1433.1 mAh g-1 at 0.1 C and exhibits outstanding rate capability and long-term cycling stability with superior capacity retention after 900 cycles at 1 C and 1400 cycles at 2 C. This work provides an experimental basis for the design of high-performance functional separators for lithium–sulfur batteries.