Single Crystals of Electrically Conductive Two-Dimensional Metal-Organic Frameworks: Structural and Electrical Transport Properties

Robert W Day; D Kwabena Bediako; Mehdi Rezaee; Lucas R Parent; Grigorii Skorupskii; Maxx Q Arguilla; Christopher H Hendon; Ivo Stassen; Nathan C Gianneschi; Philip Kim; Mircea Dincă

doi:10.1021/acscentsci.9b01006

Single Crystals of Electrically Conductive Two-Dimensional Metal-Organic Frameworks: Structural and Electrical Transport Properties

ACS Cent Sci. 2019 Dec 26;5(12):1959-1964. doi: 10.1021/acscentsci.9b01006. Epub 2019 Dec 10.

Authors

Affiliations

¹ Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02138, United States.
² Department of Physics and John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, United States.
³ Department of Chemistry, University of California Berkeley, Berkeley, California 94720, United States.
⁴ Department of Chemistry, Materials Science & Engineering, Biomedical Engineering, International Institute for Nanotechnology, Northwestern University, Evanston, Illinois 60208, United States.
⁵ Innovation Partnership Building, University of Connecticut, Storrs, Connecticut 06269, United States.
⁶ Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97401, United States.

Abstract

Crystalline, electrically conductive, and intrinsically porous materials are rare. Layered two-dimensional (2D) metal-organic frameworks (MOFs) break this trend. They are porous crystals that exhibit high electrical conductivity and are novel platforms for studying fundamentals of electricity and magnetism in two dimensions. Despite demonstrated applications, electrical transport in these remains poorly understood because of a lack of single crystal studies. Here, studies of single crystals of two 2D MOFs, Ni₃(HITP)₂ and Cu₃(HHTP)₂, uncover critical insights into their structure and transport. Conductivity measurements down to 0.3 K suggest metallicity for mesoscopic single crystals of Ni₃(HITP)₂, which contrasts with apparent activated conductivity for polycrystalline films. Microscopy studies further reveal that these MOFs are not isostructural as previously reported. Notably, single rods exhibit conductivities up to 150 S/cm, which persist even after prolonged exposure to ambient conditions. These single crystal studies confirm that 2D MOFs hold promise as molecularly tunable platforms for fundamental science and applications where porosity and conductivity are critical.