Synthesis and Characterization of Fe-Phthalocyanine-Based Metal–Organic Framework

This paper reports the successful synthesis of Fe-phthalocyanine-based metal-organic framework (FePc-MOF) by simple thermal polymerization. FePc-MOF is a promising candidate for Lieb lattice, which is a type of Dirac materials with two independent sites in a square unit cell, and it is theoretically predicted to have a unique electronic structure featuring both a Dirac band and a flat band near the Fermi level. The prepared samples exhibit the structure of FePc-MOF, as confirmed by X-ray diffraction, Fourier transform infrared spectroscopy, and transmission electron microscopy. The FePc-MOF pellet demonstrates electrical conductivity approximately a thousand times higher than that of its precursor, octacyano-Fe-phthalocyanine. This significant increase in electrical conductivity compared to the precursor indicates that FePc-MOF has a 2D π-electron system with a FePc-based framework and is consistent with the prediction that FePc-MOF is a semiconductor with a narrow energy gap due to its Lieb lattice-like structure. The synthesis method developed in this study is expected to advance fundamental research on Lieb lattices as new electronic and magnetic functional materials.