Air/liquid interfacial formation process of conductive metal-organic framework nanosheets

Takashi Ohata; Akihiro Nomoto; Takeshi Watanabe; Ichiro Hirosawa; Tatsuyuki Makita; Jun Takeya; Rie Makiura

doi:10.1016/j.jcis.2023.05.151

Air/liquid interfacial formation process of conductive metal-organic framework nanosheets

J Colloid Interface Sci. 2023 Dec:651:769-784. doi: 10.1016/j.jcis.2023.05.151. Epub 2023 May 26.

Authors

Takashi Ohata¹, Akihiro Nomoto², Takeshi Watanabe³, Ichiro Hirosawa³, Tatsuyuki Makita⁴, Jun Takeya⁴, Rie Makiura⁵

Affiliations

¹ Department of Materials Science, Graduate School of Engineering, Osaka Prefecture University, 1-2 Gakuen-cho, Nakaku, Sakai, Osaka 599-8570, Japan.
² Department of Applied Chemistry, Graduate School of Engineering, Osaka Metropolitan University, 1-1 Gakuen-cho, Nakaku, Sakai, Osaka 599-8531, Japan.
³ Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan.
⁴ Material Innovation Research Center (MIRC) and Department of Advanced Materials Science, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561, Japan.
⁵ Department of Materials Science, Graduate School of Engineering, Osaka Prefecture University, 1-2 Gakuen-cho, Nakaku, Sakai, Osaka 599-8570, Japan; Department of Materials Science, Graduate School of Engineering, Osaka Metropolitan University, 1-2 Gakuen-cho, Nakaku, Sakai, Osaka 599-8570, Japan. Electronic address: rie.makiura@omu.ac.jp.

PMID: 37336654
DOI: 10.1016/j.jcis.2023.05.151

Abstract

The air/liquid interface is a superior platform to create nanosheets of materials by promoting spontaneous two-dimensional growth of components. Metal-organic frameworks (MOFs)-intrinsically porous crystals-with π-conjugated triphenylene-based ligands show high electrical conductivities. Forming nanosheets of such conductive MOFs should enable their use in electronic devices. Although highly conductive MOF nanosheets have been created at the air/liquid interface, direct control of their continuity, morphology, thickness, crystallinity, and orientation directly influencing device performance remains as an issue to be addressed. Here, we present detailed insights into the formation process of electrically conductive MOF nanosheets composed of 2,3,6,7,10,11-hexaiminotriphenylene (HITP) and Ni²⁺ ions (HITP-Ni-NS) at the air/liquid interface. The morphological and structural features of HITP-Ni-NS strongly depend on the standing time-the time without any external actions involved, but leaving the interface undisturbed after setting the ligand solution onto the metal-ion solution. We find that the fundamental features of HITP-Ni-NS are determined by the standing time with conductivity sensitively influenced by such pre-determined HITP-Ni-NS characteristics. These findings will lead towards the establishment of a rational strategy for creating MOF nanosheets at the air/liquid interface with desired properties, thereby accelerating their use in diverse potential applications.

Keywords: Air/liquid interfaces; Electrically conductive; Langmuir–Blodgett films; Metal–organic frameworks; Nanosheets; Oriented bottom-up growth.