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Nanoporous thin materials are of central importance for membrane-based applications ranging from hydrogen fuel cells and desalination to CO2 separation and biomedical devices.[1,2] State-of-the-art micrometer-thick polymer membranes exhibit suboptimal performance due to low ionic conductivity, reactant crossover, and high production costs.[3,4] Because ionic conductivity scales inversely with membrane thickness, atomically thin two-dimensional (2D) membranes with nanometer-sized pores offer ultra-high permeability while maintaining strong selectivity, making them promising candidates for energy conversion and separation technologies. Conventional top-down approaches to introduce nanopores into 2D materials, such as electron-beam irradiation, plasma etching, or ion bombardment, offer limited control over pore chemistry, and the scalability of the process remains elusive.[5]
Bottom-up strategies rooted in reticular chemistry, including covalent organic frameworks (COFs) and non-covalent analogues such as supramolecular and hydrogen-bonded frameworks, enable precise tuning of pore size, functionality, and material composition.[6–9]
Within this field, molecular self-assembly via Langmuir–Blodgett techniques provides a versatile route to engineer atomically thin porous membranes through rational design of molecular building blocks.
Over the last five years, we combined computational and experimental approaches to elucidate the formation of free-standing, molecularly thin nanoporous membranes and films from PAH- and borazine-based molecular building blocks composed of abundant elements (H, B, C, N). These materials exhibit thicknesses spanning 0.35–2.50 nm, pore diameters from 0.35 to 3.5 nm, and functionalities tailored for separation and power density generation.[10–13] Our multiscale computational framework integrates density functional theory (DFT) and classical all-atom molecular dynamics (MD) to capture the principal factors guiding molecular self-assembly and pore architecture design: (i) intermolecular non-covalent forces (e.g., π–π stacking, hydrogen bonding), (ii) molecular orientation at the water–air interface, (iii) size of the conjugated core aromatic system, and (iv) steric effects of peripheral groups.
Overall, this series of works demonstrates the effectiveness of a dual theoretical–experimental approach for guiding Langmuir–Blodgett self-assembly of 2D porous materials. By combining rational selection of molecular building blocks with controlled fabrication, it enables versatile, tunable structures with high potential for energy, separation, and electronic applications, and paves the way for descriptor-based, machine-learning–guided design.
| References | [1] Wang, Z.; Wu, A.; Colombi Ciacchi, L.; Wei, G. Recent Advances in Nanoporous Membranes for Water Purification. Nanomaterials 2018, 8. (2), 65. https://doi.org/10.3390/nano8020065. [2] Kidambi, P. R.; Chaturvedi, P.; Moehring, N. K. Subatomic Species Transport through Atomically Thin Membranes: Present and Future Applications. Science 2021, 374 (6568), eabd7687. https://doi.org/10.1126/science.abd7687. [3] Yip, N. Y.; Brogioli, D.; Hamelers, H. V. M.; Nijmeijer, K. Salinity Gradients for Sustainable Energy: Primer, Progress, and Prospects. Environ. Sci. Technol. 2016, 50 (22), 12072–12094. https://doi.org/10.1021/acs.est.6b03448. [4] Geise, G. M.; Hickner, M. A.; Logan, B. E. Ionic Resistance and Permselectivity Tradeoffs in Anion Exchange Membranes. ACS Appl. Mater. Interfaces 2013, 5 (20), 10294–10301. https://doi.org/10.1021/am403207w. [5] Macha, M.; Marion, S.; Nandigana, V. V. R.; Radenovic, A. 2D Materials as an Emerging Platform for Nanopore-Based Power Generation. Nat. Rev. Mater. 2019, 4 (9), 588–605. https://doi.org/10.1038/s41578-019-0126-z. [6] Pfeffermann, M.; Dong, R.; Graf, R.; Zajaczkowski, W.; Gorelik, T.; Pisula, W.; Narita, A.; Müllen, K.; Feng, X. Free-Standing Monolayer Two-Dimensional Supramolecular Organic Framework with Good Internal Order. J. Am. Chem. Soc. 2015, 137 (45), 14525–14532. https://doi.org/10.1021/jacs.5b09638. [7] Hisaki, I. Hydrogen-Bonded Porous Frameworks Constructed by Rigid π-Conjugated Molecules with Carboxy Groups. J. Incl. Phenom. Macrocycl. Chem. 2020, 96 (3–4), 215–231. https://doi.org/10.1007/s10847-019-00972-0. [8] uzuki, Y.; Tohnai, N.; Saeki, A.; Hisaki, I. Hydrogen-Bonded Organic Frameworks of Twisted Polycyclic Aromatic Hydrocarbon. Chem. Commun. 2020, 56 (87), 13369–13372. https://doi.org/10.1039/D0CC06081J. [9] Zheng, Z.; Opilik, L.; Schiffmann, F.; Liu, W.; Bergamini, G.; Ceroni, P.; Lee, L. T.; Schütz, A.; Sakamoto, J.; Zenobi, R.; Vandevondele, J.; Schlüter, A. D. Synthesis of Two-Dimensional Analogues of Copolymers by Site-to-Site Transmetalation of Organometallic Monolayer Sheets. J. Am. Chem. Soc. 2014, 136 (16), 6103–6110. https://doi.org/10.1021/ja501849y. [10] iu, X.; He, M.; Calvani, D.; Qi, H.; Gupta, K. B. S. S.; de Groot, H. J. M.; Sevink, G. J. A.; Buda, F.; Kaiser, U.; Schneider, G. F. Power Generation by Reverse Electrodialysis in a Single-Layer Nanoporous Membrane Made from Core–Rim Polycyclic Aromatic Hydrocarbons. Nat. Nanotechnol. 2020, 15 (4), 307–312. https://doi.org/10.1038/s41565-020-0641-5. [11] Van Der Ham, A.; Liu, X.; Calvani, D.; Melcrová, A.; Kozdra, M.; Buda, F.; Overkleeft, H. S.; Roos, W. H.; Filippov, D. V.; Schneider, G. F. Freestanding Non-Covalent Thin Films of the Propeller-Shaped Polycyclic Aromatic Hydrocarbon Decacyclene. Nat. Commun. 2022, 13 (1), 1920. https://doi.org/10.1038/s41467-022-29429-8. [12] Liu, X.; Calvani, D.; Leist, C.; Makurat, M.; Melcrová, A.; He, M.; Scholma, D.; Sevink, G. J. A.; Buda, F.; Hermans, Y.; Hofmann, J. P.; Qi, H.; Feng, X.; Roos, W. H.; Kaiser, U.; Schneider, G. F. Monolayer Nanocrystalline Graphene Synthesized from Pyrolyzing a Langmuir Monolayer of a Polyaromatic Hydrocarbon. Sci. Adv. 2026, 12 (1), eadv1856. https://doi.org/10.1126/sciadv.adv1856. [13] Calvani, D.; Jiao, A.; Kock, T. J. F.; Siegler, M. A.; Gupta, K. B. S. S.; Filippov, D. V.; De Groot, H. J. M.; Sevink, G. J. A.; Schneider, G. F.; Buda, F. Computational Modeling and Self-Assembly Synthesis of Borazine-Based Free-Standing Molecular-Thin Films. Langmuir 2026, acs.langmuir.5c05963. https://doi.org/10.1021/acs.langmuir.5c05963. |
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