Schiff base anchored on metal-organic framework for Co (II) removal from aqueous solution

A novel metal-organic frameworks (MOFs) UiO-66-Schiff base was successfully synthesized by post-synthetic modification to investigate the cobalt sorption behaviour in simulated wastewater. The thermodynamic and kinetic parameters demonstrated the sorption process to be spontaneous, endothermic and pseudo-second-order chemisorption. The maximum cobalt sorption capacity of the synthetic MOFs was approximately 256 mg g−1, and the stable and porous Schiff base-derived material displayed excellent regenerated availability with at least five recycle applications. Moreover, density functional theory (DFT) calculations have been performed to explore the coordination modes between cobalt ions and ligands in UiO-66-Schiff base, which revealed that the Schiff base group could take cobalt (II) from cobalt ions hydrates [Co(H2O)6]2+ and Co-CHES (Co-2-(cyclohexylamino)-ethane sulfonic acid) complex [Co(CHES)(H2O)5]+ to form [CoLN(H2O)5]2+ or [CoLO(H2O)4]+. This study offers a facile approach for developing Schiff base modification MOF sorption of cobalt (II) ions from aqueous solutions and provides theoretical and practical guidance on new MOF designs for selective removal of radionuclides.