Recent progress on pristine metal/covalent-organic frameworks and their composites for lithium–sulfur batteries

Lithium–sulfur (Li–S) batteries have emerged as promising energy storage devices due to their high theoretical specific energy densities; their practical applications, however, have been restricted due to their poor cycling stability arising from the shuttle effect of the S cathode and dangerous Li dendrite growth. S and Li can be encapsulated into porous framework hosts to address these issues. Metal–organic frameworks (MOFs)/covalent-organic frameworks (COFs) have shown great potential due to their tunable frameworks, structural diversity, and functional versatility. In this review, the applications of MOFs/COFs for Li–S batteries in terms of the sulfur hosts, electrolyte containers, separators, and Li dendrite blocking barriers are systematically summarized. A short conclusion and outlook regarding future research opportunities for pristine MOFs/COFs for Li–S batteries are also provided.