An Electrically Conducting Metal–Organic Framework Having Two Orthogonal Transport Pathways

Published

December 12, 2024

Author(s)

Shiyu Zhang, Weikang Zhang, Ashok Yadav, Md. Ansari, Jonathan Cromer, Jorge Moreno, Gavin McCarver, Wei Zhou, Sourav Saha

Abstract

Owing to their diverse potential applications in electronics and energy technologies, electrically conducting metal–organic frameworks (EC-MOFs) have emerged as one of the most coveted functional materials of the twenty-first century. Among various MOF architectures, two-dimensional graphitic frameworks composed of square planar metal ions and trigonal planar aromatic ligands consistently display the most impressive electrical conductivities because of their unique abilities to simultaneously support in-plane (through bonds) and out-of-plane (through space) charge transport in two orthogonal directions. However, the large disparities between two orthogonal conduction pathways of 2D MOFs also render their conductivities highly anisotropic and dampen bulk conductivity. To address this issue, herein, we present a novel design strategy, which delivered an unprecedented redox-complementary dual-ligand 2D graphitic MOF (CDL-MOF1), Cu3(HHTP)(HHTQ) featuring a π-donor hexahydroxythiophene (HHTP) ligand and a π-acceptor hexahydroxytricycloquinazoline (HHTQ) ligand located at alternating corners of the hexagonal framework. Computational studies suggested that the AB stacking pattern of hexagonal CDL-MOF1 layers, which created alternating HHTP/HHTQ π-donor/acceptor stacks at each corner of the hexagons, was energetically slightly more favored than AA stacking pattern forming segregated HHTP and HHTQ stacks at alternate corners of the hexagons. Both arrangements, however, present more efficient through-space out-of-plane charge transport pathways than single-ligand isostructural MOFs that contain only homomeric π-stacks. Consequently, Cu3(HHTP)(HHTQ) MOF displayed decisively higher bulk conductivity (0.12 S/m) than isostructural Cu3(HHTP)2 and Cu3(HHTQ)2 MOFs based on each ligand. Since all three catechol-type ligand-based 2D graphitic MOFs possess similar in-plane through-bond charge transport capabilities, the higher bulk conductivity of CDL-MOF1 is attributed to its superior out-of-plane through-space charge transport capability.

Citation

Chemistry of Materials

Pub Type

Journals

Keywords

Porous materials, Electrical conductivity, Band structure

Citation

Zhang, S. , Zhang, W. , Yadav, A. , Ansari, M. , Cromer, J. , Moreno, J. , McCarver, G. , Zhou, W. and Saha, S. (2024), An Electrically Conducting Metal–Organic Framework Having Two Orthogonal Transport Pathways, Chemistry of Materials (Accessed October 13, 2025)