Metal-organic frameworks for adsorption of alkali metals ions

Abstract

Highly efficient separation and recovery of alkali metal ions (e.g. lithium, sodium, potassium, rubidium, and cesium) from brines, including natural and artificial specieses, remains an urgent task because of the huge reserves and increasing demand in advanced industries. During the past twenty years, porous metal-organic frameworks (MOFs), with controllable channel structures and chemical micro-environments, have been exploited as a new selection to the field of alkali metal ion adsorption and separation. This review focuses on the progress in MOFs and MOF-based adsorbents for the selective capture and co-adsorption of this class of metal ions. The adsorption performances were rationally assessed and compared with regards to adsorption capacity, kinetics, selectivity, and regeneration. The mechanisms were systematically summaried, including chelation, ion exchange, pore sieving, and electrostatic interaction, from the standpoints of adsorption thermodynamics and diffusion dynamics. Finally, we pointed to the faced drawbacks and challenges, and further proposed future opportunities for designing highly efficient MOF-based adsorbents for alkali metal ions adsorption.