Triple-Site Integrated Redox-Active Metal–Organic Cages Enable Complementary Acceleration Mechanisms for Serially Enhancing Sulfur Redox Kinetics

The development of lithium-sulfur batteries (LSBs) is hindered by the shuttle effect of lithium polysulfides (LiPSs) and sluggish sulfur redox reaction (SRR) kinetics. Herein, we integrate multiple functional units (-SH, -NH₂, Zr) into metal-organic cages (MOCs) to construct a triple-site integrated MOC (TSI-MOC), synergistically suppress the shuttle effect, and promote the SRR. The -SH-decorated ligand forms a sulfur oligomer with LiPSs, promoting faster reaction pathways. The exposed Zr-based clusters catalyze the conversion of LiPSs, while the -NH₂-functionalized ligand adjacent to the metal clusters aids in aggregating LiPSs, further enhancing the catalytic and confinement effects. LSBs with TSI-MOCs deliver a higher discharge capacity (949.7 mAh g^-1) and a lower capacity decay rate (only 0.018% at 1 C) compared to those with single-site MOCs (S-MOCs) and dual-site integrated MOCs (DSI-MOCs). The TSI-MOC also enables LSBs with a high areal capacity of 9.08 mAh cm^-2 under a high sulfur loading of 9.1 mg cm^-2, as well as the stable operation of Li-S pouch cells with a high energy density of 307 Wh kg^-1. This work demonstrated the importance of integrating multiple functional sites to improve the chemical interactions between hosts and redox-active intermediates, facilitating the thoughtful design of MOCs for high-performance LSBs.