Assorted functionality-appended UiO-66-NH₂ for highly efficient uranium(vi) sorption at acidic/neutral/basic pH

Area of Science:

• Materials Science
• Environmental Chemistry
• Nanotechnology

Background:

• Metal-organic frameworks (MOFs) offer tunable properties for various applications.
• UiO-66-NH2 is a robust Zr(IV)-based MOF amenable to post-synthetic modification.
• Efficient removal of radionuclides like uranium from aqueous streams is critical.

Purpose of the Study:

• To synthesize and characterize a library of functionalized UiO-66-NH2 MOFs.
• To evaluate the efficacy of these functionalized MOFs as solid-phase extractants for uranyl ions.
• To investigate the influence of pH and functional groups on uranyl ion sorption efficiency.

Main Methods:

• Post-synthetic modification (PSM) of UiO-66-NH2 with various functional groups.
• Characterization using FT-IR, NMR, PXRD, TGA, SEM-EDX, and BET analysis.
• Uranyl ion extraction experiments across a pH range of 1-9, including kinetic and desorption studies.

Main Results:

• Eight distinct functionalized UiO-66-NH2 derivatives were successfully synthesized.
• UiO-66-PO-Ph exhibited the highest sorption capacity (~96%) at pH 3.
• UiO-66-NH2 and UiO-66-IMP showed excellent sorption (~92% and ~90%) at neutral pH 7.
• Sorption efficiencies varied significantly with functional groups and pH conditions.
• Rapid uranium sorption (approx. 2 hours) and efficient elution with dilute nitric acid were achieved.
• MOFs demonstrated moderate recyclability for uranium sorption.

Conclusions:

• Functionalized MOFs, particularly UiO-66-PO-Ph, are effective solid-phase extractants for uranyl ions.
• The choice of functional group and pH significantly impacts sorption efficiency.
• UiO-66-NH2 serves as a versatile platform for developing MOF-based sorbents for radionuclide removal.
• These materials hold potential for treating uranium-contaminated aqueous waste streams.