Armin Goelzhaeuser1
Bielefeld University1
To achieve osmotic water transport, nature utilizes membrane proteins (aquaporins) with only 0.3 nm wide channels that efficiently transport water molecules in a “single-file” motion across cell membranes but block all ionic species. This has inspired the creation of artificial membranes with similar “sub-nanometer” channels that combine rapid water flow with superior ion rejection. We show that 1.2 nm thick carbon nanomembranes (CNMs) made from cross-linking of terphenylthiol (TPT) self-assembled monolayers possess an extremely high pore density of ~10<sup>18</sup> m<sup>−2</sup><i>, i.e. one sub-nm channel per square nanometer</i> [1]. It will be demonstrated that TPT CNMs efficiently hinder the translocation of ions, including protons, while they let water molecules rapidly pass through [2]. Their membrane resistance reaches ~10<sup>4 </sup>Ω cm<sup>2 </sup>in 1 M Cl<sup>−</sup> solutions, comparable to lipid bilayers of a cell membrane. Consequently, a single CNM channel yields a ~10<sup>8</sup> higher resistance than pores in lipid membrane channels and carbon nanotubes. The ultra-high ionic exclusion by CNMs is likely dominated by a steric hindrance mechanism, coupled with electrostatic repulsion, surface functional groups and entrance effects. We demonstrate the operation of TPT CNMs as semipermeable membranes in forward osmosis, and discuss possible applications. Our observations highlight the potential of utilizing CNMs for water treatment and open up avenues to create 2D membranes through molecular self-assembly for highly selective and fast separations.<br/>[1] Y. Yang, P. Dementyev, N. Biere, D. Emmrich, P. Stohmann, R. Korzetz, X. Zhang, A. Beyer, S. Koch, D. Anselmetti, A. Gölzhäuser, <i>ACS Nano</i> <b>2018</b>, <i>12</i>, 4695.<br/>[2] Y. Yang, R. Hillmann, Y. Qi, R. Korzetz, N. Biere, D. Emmrich, M. Westphal, B. Büker, A. Hütten, A. Beyer, D. Anselmetti, A. Gölzhäuser, <i>Adv. </i><i>Mater. </i><b>2020,</b><i> </i>1907850<i>.</i>