Growth mechanisms and anisotropic softness–dependent conductivity of orientation-controllable metal–organic framework nanofilms
Ming‐Shui Yao, Ken‐ichi Otake, Tomoyuki Koganezawa, Moe Ogasawara, Hitoshi Asakawa, Masahiko Tsujimoto, Ziqian Xue, Yanhong Li, Nathan C. Flanders, Ping Wang, Yifan Gu, Tetsuo Honma, Shogo Kawaguchi, Yoshiki Kubota, Susumu Kitagawa
Abstract
Conductive metal–organic frameworks ( c MOFs) manifest great potential in modern electrical devices due to their porous nature and the ability to conduct charges in a regular network. c MOFs applied in electrical devices normally hybridize with other materials, especially a substrate. Therefore, the precise control of the interface between c MOF and a substrate is particularly crucial. However, the unexplored interface chemistry of c MOFs makes the controlled synthesis and advanced characterization of high-quality thin films, particularly challenging. Herein, we report the development of a simplified synthesis method to grow “face-on” and “edge-on” c MOF nanofilms on substrates, and the establishment of operando characterization methodology using atomic force microscopy and X-ray, thereby demonstrating the relationship between the soft structure of surface-mounted oriented networks and their characteristic conductive functions. As a result, crystallinity of c MOF nanofilms with a thickness down to a few nanometers is obtained, the possible growth mechanisms are proposed, and the interesting anisotropic softness–dependent conducting properties (over 2 orders of magnitude change) of the c MOF are also illustrated.