(226e) Subnanometer Pore Control for Chemical Vapor Deposited Inorganic Membranes

Synthesizing subnanometer pores mimicking the functionality of ion-selective biological channels has been challenging. If successful, it promises precise ion-ion separation and solute-selective separations for various applications. We present a novel synthesis by adapting the synthesis for pore-free inorganic coatings to porous membranes. By controlling the chemical precursor and temperatures, we demonstrate a molecular-level design of ceramic thin-film membranes with tunable pores for precise molecular sieving. Specifically, we mixed methanol precursors with water vapor co-reactants during the atomic layer deposition of aluminum oxide. During such surface reactions, methanol terminates oxide growth on a fraction of surfaces by reacting with adsorbed aluminum precursors. Such membranes showed exceptional selectivity towards monovalent and divalent cations. We attribute the observed selectivity to the dehydration of large divalent ions, whereas small monovalent ions can rapidly permeate with an intact hydration shell. Besides, the pore size and charge control allow for the separation of F- from Cl- ions. We also discuss membrane synthesis and microstructure control: the subnanometer porous layer can be integrated over an anodized alumina support or nanoporous polymer support; and in addition to thermal-assisted ALD, light-assisted surface-limited deposition can generate comparable pores. X-ray absorption near-edge spectroscopy and extended X-ray absorption fine structures were employed to build a membrane microstructure database for future high-throughput discovery of functional inorganic membranes.

[1] X. Zhou, R. Shevate, D. Huang, T. Cao, X. Shen, S. Hu, A. U. Mane, J. W. Elam, J.H Kim, M. Elimelech, “Ceramic Thin-Film Composite Membranes with Tunable Subnanometer Pores for Molecular Sieving”, Nature Communications, 14, 7255 (2023).

[2] D. Solanki, C. He, Y. Lim, R., Yanagi, S. Hu, “Where Atomically Precise Catalysts, Optoelectronic Devices, and Quantum Information Technology Intersect: Atomic Layer Deposition of Ternary Materials”, Chemistry of Materials, 36, 3, 1013–1024 (2024).

[3] X. Zhou, Y.-Y. Zhao, S.-R. Kim, M. Elimelech, S. Hu, J. Kim, “Controlled TiO2 Growth on Reverse Osmosis and Nanofiltration Membranes by Atomic Layer Deposition: Mechanisms and Potential Applications”, Environmental Science & Technology, 52(24), 14311–14320 (2018).

[4] X. Zhou, M. Heiranian, M. Yang, R. Epsztein, K. Gong, C. E. White, S. Hu, J.-H. Kim, and M. Elimelech, “Selective Fluoride Transport in Subnanometer TiO2 Pores”, ACS Nano, 15 (10),16828 (2021).