Two-Dimensional Conjugated Metal-Organic Frameworks with a Ring-in-Ring Topology and High Electrical Conductance.

Abstract

Electrically conducting two-dimensional (2D) metal-organic frameworks (MOFs) have garnered significant interest due to their remarkable structural tunability and outstanding electrical properties. However, the design and synthesis of high-performance materials face challenges due to the limited availability of specific ligands and pore structures. In this study, we have employed a novel highly branched D3h symmetrical planar conjugated ligand, dodechydroxylhexabenzotrinaphthylene (DHHBTN) to fabricate a series of 2D conductive MOFs, named M-DHHBTN (M=Co, Ni, and Cu). This new family of MOFs offers two distinct types of pores, elevating the structural complexity of 2D conductive MOFs to a more advanced level. The intricate tessellation patterns of the M-DHHBTN are elucidated through comprehensive analyses involving powder X-ray diffraction, theoretical simulations, and high-resolution transmission electron microscope. Optical-pump terahertz-probe spectroscopic measurements unveiled carrier mobility in DHHBTN-based 2D MOFs spanning from 0.69 to 3.10 cm2 V-1 s-1. Among M-DHHBTN famility, Cu-DHHBTN displayed high electrical conductivity reaching 0.21 S cm-1 at 298 K with thermal activation behavior. This work leverages the "branched conjugation" of the ligand to encode heteroporosity into highly conductive 2D MOFs, underscoring the significant potential of heterogeneous double-pore structures for future applications.