Advancements in UiO-66-based adsorbents: a critical review of their role in radionuclide sequestration

Abstract

The removal of radionuclides from radioactive waste generated during nuclear fuel fabrication or post-irradiation remains a significant obstacle to the widespread adoption of nuclear power, driven by the waste's complex composition, high radiotoxicity, and the presence of numerous interfering elements. Metal –organic frameworks (MOFs) are promising candidates for radionuclide separation due to their high surface area, excellent pore structure, and tunable surface functional groups. The present review highlights the recent progress in the application of UiO-66-based MOFs for the remediation of radionuclides, concentrating on the adsorption of essential radionuclides such as U, Th, Tc, Pd, Sr, and Cs from aqueous solutions, which are crucial for the management of liquid radioactive waste. Additionally, the removal of I₂ in gaseous and aqueous solutions using different UiO-66-based adsorbents is provided. The review commences with a succinct introduction to nuclear energy and UiO-66-based MOFs. The following sections systematically examine various UiO-66 variants, including the unmodified material, its composites, and derivatives produced through post-synthetic modification (PSM). Special emphasis is placed on structural alterations, along with a comprehensive assessment of their radionuclide sequestration capabilities and a detailed explanation of the interaction mechanisms between these MOF-based materials and various radionuclides. The discussion wraps up with specifying potential research avenues, highlighting the rational design of advanced UiO-66 variants, such as magnetic composites, to enhance separation and targeted functionalization with selective moieties, aiming for improved selectivity toward radionuclides even in complex matrices. Additionally, the creation of sustainable, scalable, and environmentally friendly synthesis methods is underscored as essential for replacing hazardous solvents and facilitating industrial-scale production, emphasizing the necessity for ongoing research to translate these materials into practical applications. Ultimately, these collaborative research initiatives are crucial for bridging the divide between fundamental advancements in material design and real-world applications, thus enabling the deployment of robust, recyclable, and highly selective UiO-66 derived adsorbents in large-scale systems for the remediation of nuclear wastewater and contaminated industrial effluents.