COFs demonstrate a significant potential as advanced sulfur host materials in Li-S batteries, effectively mitigating the polysulfide shuttle effect as a major bottleneck to commercialization through their tunable pore structures, high surface areas, and designable functional sites. This review systematically outlines the development of COF-based materials in Li-S battery cathodes, from early physical confinement strategies to recent advances involving heteroatom doping, multidimensional architectures, flexible frameworks, and conductive composites. These approaches can collectively enhance sulfur utilization, improve reaction kinetics, and increase cycling stability.

Despite these promising developments, several challenges remain for the practical application of COF-based cathodes. The key issues include the limited intrinsic conductivity of most COFs, difficulties in maintaining crystallinity during large-scale synthesis, insufficient chemical stability under prolonged cycling, and high manufacturing costs. Moreover, optimizing electrolyte/sulfur ratios and interface engineering between COFs and sulfur are critical for improving electrochemical performance.

Future research should prioritize 1) enhancing the electronic and ionic conductivity of COFs through structural design and hybridization with conductive substrates; 2) developing scalable and eco-friendly synthesis methods to facilitate commercial adoption; 3) designing COFs with high sulfur loading capacity and strong polysulfide adsorption; 4) improving chemical and mechanical stability under operating conditions; and 5) employing advanced in-situ characterization techniques to elucidate ion transport and reaction mechanisms. With continued innovation in material design and processing, COF-based sulfur hosts are expected to play a vital role in realizing high-energy, long-lasting, and commercially viable Li-S batteries.