Head-to-tail assembled borphyrins for solid-state lithium extraction

Lithium is a critical mineral for advancing greener technologies. Extraction of lithium ions (Li⁺) from sea salt, minerals, and waste is important, but has been hindered by the lack of extraction methods that offer both high selectivity and strong lithium affinity. Here, we report a dioxaborole-linked, head-to-tail assembled macrocycle - termed borphyrin - featuring a rigid cavity with a 16-crown-4-like configuration. This molecule exhibits strong affinity for lithium and high selectivity over competing cations under dry solid-liquid extraction conditions, owing to its narrow binding cavity and planar macrocyclic core. Borphyrin enabled the extraction of lithium from crystalline solids of ether-insoluble salts, as well as selective extraction of Li⁺ from dried mixed-salt matrices containing alkali, alkaline earth and transition-metal salts. These results establish borphyrin as a potential molecular platform for selective lithium recognition and solid-liquid lithium extraction.