Metal organic framework materials for efficient lithium adsorption from aqueous solution – comparative study

Lithium, a critical energy element, is essential for rechargeable batteries, pharmaceuticals, and various industrial applications. Conventional extraction methods from mineral ores and brines are energy-intensive and environmentally damaging. Metal–organic frameworks (MOFs) have emerged as sustainable alternatives due to their tunable porosity, chemical stability, and selective adsorption properties. This study investigates the lithium adsorption performance of six MOFs: MOF-801, MOF-303, aluminium fumarate, MIL-53(Al), MIL-100(Fe), and CPO-27(Ni). Among these, five materials, MOF-801, MOF-303, MIL-53(Al), aluminium fumarate, and CPO-27(Ni), have not been previously reported for lithium adsorption. Adsorption experiments were conducted using synthetic lithium solutions, and the adsorption capacities were determined by using ICP-OES. Structural and morphological analyses were conducted using PXRD, SEM-EDS, and XPS. At 12,000 ppm lithium concentration, CPO-27(Ni) exhibited the highest adsorption capacity (287.2 mg/g), followed by MOF-801 (269.4 mg/g) and MOF-303 (246.0 mg/g), significantly exceeding values reported in the literature. To further explore the capacity limits, the concentration was increased to 36,000 ppm. CPO-27(Ni) and MOF-303 reached maximum capacities of 544.8 mg/g and 494.9 mg/g, respectively, indicating a high density of accessible binding sites and strong lithium-framework interactions. Kinetic studies showed that lithium adsorption by CPO-27(Ni) followed a pseudo-first-order model, while the Freundlich isotherm best described the equilibrium data, indicating multilayer adsorption on a heterogeneous surface. Thermodynamic analysis confirmed that the process was exothermic and non-spontaneous under the studied conditions. While the pH-dependent studies showed optimal uptake at pH 7. Additionally, regeneration tests revealed that CPO-27(Ni) retained 94 % of its initial capacity after three adsorption–desorption cycles. These findings demonstrate the strong potential of CPO-27(Ni) and other underexplored MOFs as efficient, regenerable materials for lithium recovery from aqueous solutions.