Two-dimensional d-π conjugated metal-organic framework based on hexahydroxytrinaphthylene

The development of new two-dimensional (2D) d-π conjugated metal-organic frameworks (MOFs) holds great promise for the construction of a new generation of porous and semiconductive materials. This paper describes the synthesis, structural characterization, and electronic properties of a new d-π conjugated 2D MOF based on the use of a new ligand 2,3,8,9,14,15- hexahydroxytrinaphthylene. The reticular self-assembly of this large π-conjugated organic building block with Cu(II) ions in a mixed solvent system of 1,3-dimethyl-2-imidazolidinone (DMI) and H₂O with the addition of ammonia water or ethylenediamine leads to a highly crystalline MOF Cu₃(HHTN)₂, which possesses pore aperture of 2.5 nm. Cu₃(HHTN)₂ MOF shows moderate electrical conductivity of 9.01 × 10^-8 S·cm^-1 at 385 K and temperature-dependent band gap ranging from 0.75 to 1.65 eV. After chemical oxidation by I₂, the conductivity of Cu₃(HHTN)₂ can be increased by 360 times. This access to HHTN based MOF adds an important member to previously reported MOF systems with hexagonal lattice, paving the way towards systematic studies of structure-property relationships of semiconductive MOFs.