sln-Topological Covalent Organic Frameworks with Shape Dimorphism and Dipolar Rotors
We report herein the first (i) covalent organic frameworks (COFs) with <b>sln</b> topology, (ii) drastic control of the shape of COF crystals with the same topology and chemical composition, (iii) insight that these different shapes are accompanied by conformational isomerism, and (iv) installation of dipolar rotors into three-dimensional (3D) COFs. We used a new building block, hexaarylbenzene with three dipolar 1,2-difluorophenyls. Depending on the solution composition, we generated two types of COF crystals with different shapes: hexagonal prism (<b>TK-COF-P</b>) and membrane (<b>TK-COF-M</b>). Although they exhibit distinctly different powder X-ray diffraction patterns, they are chemically identical. The structural determinations revealed that they have a low-symmetric, low-density <b>sln</b> topology that is yet to be reported for COFs. The two distinct shapes─shape dimorphism─is found to accompany conformational isomerism. Temperature-dependent dielectric and <sup>19</sup>F NMR relaxation-time measurements reveal that the rotor motion is suppressed at room temperature, but the rotors respond to an external electric field at elevated temperatures owing to the high activation energy for rotation (∼20 kcal mol<sup>-1</sup>), which is desired for room-temperature applications including molecular memories. These outcomes have not only expanded the diversity of COFs but have also provided a foundation for installing external-field-responsive functions into COFs that have high thermal stability, which is expected to invoke broad applications.
Authors
- Yutaro Ogaeri (ORCID: https://orcid.org/0000-0002-0814-1698)
- Takanori Fukushima (ORCID: https://orcid.org/0000-0001-5586-9238)
- Daisuke Hashizume (ORCID: https://orcid.org/0000-0001-7152-4408)
- Yoichi Murakami (ORCID: https://orcid.org/0000-0001-9536-1631)
- Yoshiaki Shoji (ORCID: https://orcid.org/0000-0001-8437-1965)
- Takumi Sannomiya (ORCID: https://orcid.org/0000-0001-7079-2937)
- Masaki Kawano (ORCID: https://orcid.org/0000-0001-9886-4226)
- Simon Goto (ORCID: https://orcid.org/0009-0002-1835-3253)
- Koji Yazawa (ORCID: https://orcid.org/0000-0003-2384-3716)
- Yukihito Kondo (ORCID: https://orcid.org/0000-0002-5145-1712)
- Takayuki Kamihara (ORCID: https://orcid.org/0000-0002-6519-7399)
- Kiyohiro Adachi (ORCID: https://orcid.org/0000-0002-8224-8602)
- Ryosuke Takehara (ORCID: https://orcid.org/0000-0003-1711-3469)
- Hidehiro Uekusa (ORCID: https://orcid.org/0000-0001-9809-1411)
- Hiroaki Suzuki (ORCID: https://orcid.org/0000-0003-0442-3687)
- Wang Zhang (ORCID: https://orcid.org/0000-0002-8636-2816)
- Xiaohan Wang (ORCID: https://orcid.org/0000-0001-5273-4223)
- Takuya Miyazaki (ORCID: https://orcid.org/0000-0003-1884-4757)
- Atsuko Kosaka
- K. Kawamura
- T. Ogawa
Institutions
- Tokyo Institute of Technology (JP)
- JEOL (Japan) (JP)
- Global Environment Facility (US)
- Shanghai Institute for Science of Science (CN)
- The Institute of Energy Economics, Japan (JP)
- Life Science Institute (JP)
- RIKEN Center for Emergent Matter Science (JP)
- Zero Emissions Resource Organisation (NO)
- Institute of Science Tokyo (JP)
- The University of Tokyo (JP)
Publication Details
- Journal
- Journal of the American Chemical Society
- Published
- 2025-08-14
- DOI
- https://doi.org/10.1021/jacs.5c10010
- Primary Topic
- Covalent Organic Framework Applications
- Type
- article
- Field-Weighted Citation Impact
- 0.00