Grafting redox-active thiols into MOF channels for dual-interfacial regulation in Li-S batteries

Lithium-sulfur batteries (LSBs) deliver exceptional theoretical specific capacities yet suffer severe practical restrictions from polysulfide shuttling and lithium dendrite growth. Although metal-organic frameworks (MOFs) are popular separator modifiers for LSBs, they rarely integrate efficient polysulfide adsorption/catalysis with uniform lithium-ion conduction. Herein, redox-active dithiothreitol (DTT) is grafted onto the inner metal sites of MIL-101(Cr) channels to fabricate functional polypropylene (PP) separators. On the cathode side, DTT cooperates with the MOF scaffold to immobilize polysulfides, where thiol moieties streamline their redox transformation. Meanwhile, grafted DTT installs abundant lithiophilic -SH and -OH polar sites across the MOF interior. Coupled with size sieving from regular MOF pores, these sites equalize Li⁺ flux, trigger steady lithium nucleation/deposition, and effectively suppressed the growth of lithium dendrites. Enabled by dual cathode-anode interfacial modulation, this coating clearly elevates battery capacity and cyclability: Li‖Li batteries sustain stable cycling beyond 1000 h, and LSB initial discharge capacity at 0.1C rises from 999 to 1201 mAh g^-1. This universal grafting route can incorporate organosulfur active sites into diverse mesoporous MOFs, with promising extensions to metal anode protection, potassium-sulfur batteries, and general electrocatalysis.