Selective lithium capture from simulated brine by a sulfonic acid-functionalized covalent organic framework

Lithium recovery from high Mg 2+ /Li + brines remain challenging. Herein, a sustainable adsorption strategy based on a sulfonic acid group, triazine-based COFs (TD–COF–S) is proposed for selective lithium extraction. TD–COF–S is a crystalline porous material with well-defined pore sizes of 1.74 and 2.31 nm, a BET surface area of 429 m 2 /g, and 20 wt% sulfonic acid groups. The appropriate pore channels and adsorption sites facilitate the transfer and adsorption of lithium ions. At 200 mg/L Li + , equilibrium is reached within 1.5 h, achieving a capacity of 24.12 mg/g. After ten cycles, TD–COF–S retained 90.5 % of its initial Li + adsorption capacity, demonstrating exceptional cycling stability. Most importantly, the selectivity coefficient of TD–COF–S for Li + reached 111.4 in simulated brine (Mg 2+ /Li + =545). The exceptional adsorption performance of TD–COF–S underscores its promise as a suitable material for efficient capture of lithium-ion from salt-lake brines. • Sulfonic acid group was successfully grafted onto TD-COF via ring-opening nucleophilic substitution. • TD–COF–S showed 2.3-fold higher Li + uptake than TD-COF due to –SO 3 H sites. • TD–COF–S reached adsorption equilibrium in 1.5 h with Mg 2+ /Li + selectivity of 111.4.