Mixed-Metal–Organic Framework with Effective Lewis Acidic Sites for Sulfur Confinement in High-Performance Lithium–Sulfur Batteries

The mixed-metal–organic framework approach and a representative zirconium–metalloporphyrin framework (MOF-525) have been developed to create novel sulfur hosts and Li–S batteries. The different local environments at the centers of the porphyrin moieties in a series of MMOFs—MOF-525(2H), MOF-525(FeCl), and MOF-525(Cu)—have led to their different behaviors for the confinement of sulfur and thus Li–S batteries. The unique structure of MOF-525(Cu) has enabled each Cu2+ site to offer two Lewis acidic sites, featuring it as a very powerful MOF host for the inclusion of sulfur and polysulfides. The S@MOF-525(Cu) cathode has demonstrated the best performance among all reported sulfur/MOFs composite cathode materials, with a reversible capacity of about 700 mAh/g at 0.5 C after 200 cycles.