CAREER: From Single Nanopores to Scalable Membranes: Engineering Ion Selectivity through Confinement and Chemical Patterning

Reliable access to critical minerals like lithium and cobalt is crucial to the nation’s economy. These materials are often found as dissolved ions in aqueous streams such as geothermal brines, water produced from oil drilling, leachates from mining, and industrial wastewater. Extracting these ions is difficult because they are mixed with similar, more abundant ions. Membranes can recover ions effectively, but they struggle to separate the desired ions from the undesired ones. This CAREER project will show how controlling the arrangement of chemical groups inside the pores of a membrane can improve ion separation. It will study how ions move through membrane pores, and how the specific patterns of chemical groups can favor one ion over another. The results will provide rules for designing better materials for ion separation. They will also help improve the domestic supply of critical minerals. Educational activities will integrate research into courses, provide hands-on training, and engage high school students and local communities. Ion–ion separation remains challenging because conventional membranes rely on size exclusion and electrostatic interactions, which are insufficient to distinguish ions with similar physicochemical properties. This CAREER project will establish a mechanistic framework for ion-selective transport. The central hypothesis is that selective ion transport arises from the precise spatial arrangement of ion-interacting functional groups under confinement. This modulates the free energy landscape for ion migration and enables efficient, reversible hopping between binding sites. This hypothesis will be tested by (1) developing well-defined experimental model systems using nanoporous graphene and metal–organic frameworks to independently control pore size, degree of confinement, and the spatial distribution of chemical groups within the pores; (2) quantifying how ion sorption thermodynamics and kinetics depends on the degree of confinement, functional group identity, and spatial arrangement; (3) measuring activation enthalpy and entropy contributions to transport properties; and (4) establishing structure–property–transport relationships between confinement, chemical patterning, and ion selectivity. The results will provide design rules for ion-selective transport in synthetic membranes and have implications for ion separations and electrochemical processes. These advances will contribute to strengthening domestic supply chains for critical materials and enable more efficient technologies for their recovery and purification. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria. NSF Award ID: 2542231 | Program: 01002627DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Luis Francisco Villalobos | Institution: University of Southern California, LOS ANGELES, CA | Award Amount: $593,325 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2542231 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2542231.html