Understanding the Mechanism and Ascertaining the Sorption Sites for the Highly Efficient and Selective Sorption of U(VI) and Th(IV) by Graphene/Zeolitic Imidazolate Framework-90 Composites: An Experimental and Theoretical Approach

) for the Th(IV) sorbed sample evidenced the effective sorption, while the red shift in the O 1s spectrum (∼531.7 eV and ∼534.4 eV for ZIF-90G) indicated the coordination of metal ions through chelation of carboxaldehyde functionalities. Elemental mapping using scanning electron microscopy coupled with energy dispersive X-ray spectroscopy also evidenced the uniform sorption of the U(VI) and Th(IV). Density functional theory and X-ray absorption spectroscopy have been employed for the further understanding of the mechanism at the molecular level.