Photoinduced synthesis of polymer-coated covalent organic framework microspheres for highly efficient lithium recovery

The increasing demand for lithium-ion batteries has led to a surge in global lithium consumption, calling for efficient extraction and recovery methods. Adsorption-based lithium recovery has gained attention for its simplicity, selectivity, and low energy requirements. However, conventional adsorption materials for lithium-ion (Li+) suffer from low surface area and covered active sites, resulting in slow recovery and inefficient uptake. Herein, we present a facile photoinduced synthesis of crown ether (CE)-based polymer grafted covalent organic framework (COF) microspheres, termed COF-CE, as an efficient lithium adsorbent. The COF-CE hybrid material possesses abundant nanochannels and highly porous surfaces, enabling rapid ion diffusion and enhancing ion accessibility to functional groups with the exclusive selectivity imparted by the grafted CE polymer towards Li+ over other monovalent cations. Notably, COF-CE exhibits exceptional absorption capacity (7.4 mg/g), rapid adsorption rates (k2 = 0.137 g mg−1 min−1) and high selectivity towards Li+, outperforming existing adsorbents. Moreover, COF-CE demonstrates remarkable Li+ regeneration and recycling capabilities, achieving near-unity recovery of lithium during the desorption phase and retaining 97 % of its adsorption capacity after five cycles. These results highlight the potential of COF-CE as an advanced adsorbent for lithium recovery in various applications, including industrial wastewater treatment and environmental remediation efforts.