• Amino functionalization narrows the Ti-MOF pore size to ~0.8 nm, enabling size-sieving to completely block polysulfide shuttling.
• Electrostatic adsorption by positively charged amino groups redistributes and reutilizes blocked polysulfides, enhancing active material utilization.
• Lewis acid-base interaction between amino and lithium ions creates transfer channels, ensuring unimpeded Li+ migration.
• The modified separator achieves an ultralow capacity decay of 0.045% per cycle over 1000 cycles at 1.0C, demonstrating superior long-term stability.