Selective recovery of uranyl ions from sea water using covalent organic framework membranes

Illustrative depiction of resource recovery plant using seawater as input and employing a covalent organic framework (COF)-based membrane to recover and store uranyl ions for further processing. Graphs show performance of different COF membranes, and the cut portion of the COF shows the shape and size (5.7 Å of TpPa-1) of the porous membrane. The plant image was generated using Gemini and subsequently edited in Inkscape (Image: Yogendra Kumar)

Developing efficient technologies to extract uranium from seawater could offer a promising long-term pathway toward securing a sustainable supply of nuclear fuel. At the same time, uranium contamination of groundwater is an important environmental and public health concern.

Over the years, researchers have developed a wide range of materials for capturing uranium from aqueous environments and seawater, including porous organic polymers and functional nanomaterials. Many of these materials rely on strong chemical interactions between functional groups and uranyl ions to selectively capture uranium. However, achieving highly selective uranium separation in the chemically complex environment of seawater remains a major challenge due to the high concentrations of competing ions.

A recent study from the Department of Physics, IISc, presents a new approach to addressing this challenge. The team show that specially designed slipped covalent organic framework (COF) membranes can completely reject uranyl ions while allowing common seawater ions to pass through.

The researchers investigated the molecular-level mechanisms responsible for this selective separation. Their analysis of ion hydration structures, free-energy barriers, and membrane-induced friction revealed how the structural arrangement of the COF layers controls the movement of different ions through the membrane.

Unlike conventional approaches that often depend on extensive chemical functionalization to introduce selective binding sites, the new strategy exploits the intrinsic structural confinement created by slipping the COF layers. This provides a way to control ion transport across the membrane primarily based on its nanoscale structure, rather than relying solely on strong chemical interactions with uranium.

The findings provide important insights into how the architecture of layered COF membranes can be engineered to control ion transport pathways and free-energy landscapes. Overall, the work demonstrates the potential of combining advanced molecular simulations with rational membrane design to develop highly selective separation technologies for challenging environmental and energy-related applications.

The research was carried out by Yogendra Kumar and Binu Varghese, under the mentorship of Prabal K Maiti, and carried out in collaboration with Accenture Labs, Bengaluru.

REFERENCE:
Varghese B, Kumar Y, Sengupta S, Maiti PK, Selective recovery of uranyl ions from sea water using covalent organic framework membranes, Small (2026).
https://doi.org/10.1002/smll.75260

LAB WEBSITE:
https://physics.iisc.ac.in/~maiti/