Two-dimensional copper-based metal−organic frameworks nano-sheets composites: One-step synthesis and highly efficient U(VI) immobilization.

• 2D MOFs nano-sheets were successfully prepared in a one-step and cost-effective synthetic route. • The solvent ratios have a great effect on their structural morphologies. • The Qmax of 2D MOFs nano-sheets can be as high as 591.79 mg g−1 for U(VI) immobilization. • The U(VI) immobilization process is exothermic and spontaneous. • The U(VI) immobilization mechanism is proposed via the binding interactions between U(VI) and −OH/C–N(H) groups. In this study, a new kind of thin 2D MOFs nano-sheets (MNS) was successfully prepared through complexation between 2-methylimidazole and Cu(II) by a one-step, and cost-effective route. The structural morphologies can be tuned by adjusting the ratio of MeOH/H 2 O. The synthesized MNS (MNS-1, MNS-2, MNS-3 and MNS-4) were fully characterized and the results indicated that the synthesized MNS were freestanding and possess micro-sized lateral dimensions and nanoscale thickness of sub-25 nm. All the obtained MNS display great performance with the adsorption capacity hierarchy of MNS-2 (591.79 mg·g-1) > MNS-3 (409.49 mg·g−1) > MNS-4 (387.07 mg·g−1) > MNS-1 (384.84 mg·g−1) at pH ˜ 6.0, and 298 K. The thermodynamic parameters indicated the exothermic and spontaneous nature of U(VI) immobilization. The U(VI) immobilization mechanism was achieved through the complexation between U(VI) and C–N(H) /−OH groups. This work supplies a facile and purposeful approach for developing 2D MOFs nano-sheets toward a highly efficient immobilization of U(VI), and it also promotes the preparation of structure-based design of nanomaterials for radionuclide-containing-medium pretreatment. [ABSTRACT FROM AUTHOR]