Researchers from India and Singapore report a crystalline membrane made from polyoxometalate clusters whose intrinsic openings are about 1 nanometer wide, enabling unusually sharp molecular separations that could help lower energy use in some industrial purification and water-reuse steps.
A research team spanning the CSIR–Central Salt and Marine Chemicals Research Institute (CSMCRI), the Indian Institute of Technology Gandhinagar (IITGN), Nanyang Technological University in Singapore and the S. N. Bose National Centre for Basic Sciences has developed an ultrathin filtration membrane built around uniformly sized, ~1-nanometer pores. The study was published in the Journal of the American Chemical Society.
Industrial separations are central to processes such as drug purification and textile dye treatment, but many plants still rely on energy-intensive methods like distillation and evaporation. Membrane filtration can be a lower-energy alternative, but widely used polymer membranes often have non-uniform pores that can change over time, reducing performance in harsh operating conditions.
The new membranes—described by the researchers as “POMbranes”—use polyoxometalate (POM) clusters as building blocks. The clusters are crown-shaped and contain a naturally occurring opening that the team reports is about 1 nanometer wide and structurally stable. To turn these nanoscale units into a practical filter, the team attached flexible chemical chains to the clusters and used self-assembly on water to form large-area, ultrathin films.
By adjusting the chain length, the researchers report that they could control how tightly the clusters pack, effectively limiting transport pathways so that molecules cross primarily through the clusters’ intrinsic pores. In testing described in the report, the membranes separated molecules that differ by roughly 100–200 Daltons—performance the researchers say is about an order of magnitude better than benchmark membranes for such narrow molecular-weight differences.
In comments provided with the work, CSMCRI senior scientist Shilpi Kushwaha said the stability of the fixed pore opening addresses a key weakness of conventional “plastic” filters whose pores can deform. CSMCRI principal scientist Ketan Patel said the membranes combine separation performance with flexibility, stability across different acidity levels (pH), and the ability to be manufactured in large sheets—traits the team argues are important for industrial adoption.
The researchers highlighted potential applications in India’s textile and pharmaceutical industries, including selective dye removal from wastewater to support water reuse, as well as solvent recovery and drug purification steps that require high selectivity. They position the membrane as a platform approach for energy- and resource-efficient separations, while noting that industrial deployment would depend on further engineering and scale-up beyond laboratory demonstrations.
