(Invited) Liquid Phase Interfacial Assemblies of Porous Nanosheets with Controlled Orientation and Thickness

Abstract

Development of rational methods for creating ordered two-dimensional (2D) structures with nanometer scale precision is one of the central issues in the nanoscience and nanotechnology fields because of their intrinsic physical-chemical properties which are seen in those of their equivalent bulk state. Inclusion of highly regulated nanopores into the nanosheet structure will further open the possible applications such as nanosieves, molecular/ion storage and sensor devices as well as introducing guest molecules into the nanopores tune variedly the sheet properties (electric conduction, nanoheterojunction). Utilizing molecular building units are suitable for creating such porous nanosheets because of rich variety of design and facile modification of size and shape. Furthermore, various chemical interactions such as covalent bond, coordination and hydrogen bond are applied for assembling molecular-based nanosheets.Here, I present a facile bottom-up synthesis of molecular nanosheets with both positional and size regulated nanopores utilizing air/liquid interfaces. By applying liquid interfaces, growth direction of the object can be well controlled with utilizing self-assembly feature of the molecules under mild conditions. We have succeeded to tune finely the nanosheet structures by rational modification of molecular building units [1-4]. In addition, new methodology we developed based on the liquid interface technique resulted in enlarging the nanosheet size. The highly crystalline structure remains after transferring a solid substrate from the liquid surface as well as without any supports. Notably, such highly oriented porous crystalline structure is obtained specifically by applying bottom up synthesis at air/liquid interfaces, not by other techniques such as drop cast [5]. Makiura, R. et al. Nature Mater. 9, 565 (2010).Motoyama, R. Makiura, O. Sakata, H. Kitagawa, J. Am. Chem. Soc. 133, 5640 (2011).Makiura, R., Konovalov, O. Rep. 3, 2506 (2013).Makiura, R. et al. ChemPlusChem. 79, 1352 (2014).Makiura, R. et al. ACS Nano, 11, 10875–10882 (2017). Figure 1