Self-Polycondensing Hypercross-Linked Polymers from Hydroxybenzyl Alcohols for Efficient Cesium Adsorption

Demand for cesium (Cs) is increasing, and production of Cs from solid ores is energy-intensive. Isolation and extraction of Cs from salt lakes and brines could provide a more sustainable approach to help meet Cs demand, but materials with high selectivity and capacity for Cs are required due to the extremely low concentration of Cs and high concentrations of interfering ions. In this work, we developed self-polycondensing hypercross-linked polymers (HCP-HBAs) from commercial benzyl alcohols substituted by hydroxyl groups at different positions (ortho-, meta-, and para-). Through the cooperative coordination of residual hydroxymethyl groups, mesoporous HCP-HBAs displayed boosted Cs+ capacity and selectivity. Among three polymers, HCP-o-HBA possessed the highest adsorption capacity (302.1 mg g–1) and separation factor (S.F.) values for Cs+/K+ (44.7), Cs+/Rb+ (13.8), and Cs+/Mg2+ (10.1), surpassing most reported porous organic and inorganic adsorbents. Besides, HCP-o-HBA also exhibited rapid adsorption kinetics (5 min, 80% adsorption capacity) and excellent recycle performance (5 cycles, >90% removal efficiency). This study presents the promising application potential of HCP-o-HBA for highly efficient and selective cesium extraction from brines and wastewater.