Paramagnetic conducting metal-organic frameworks with three-dimensional structure.

Three-dimensional (3D) well-crystallized metal-organic frameworks (MOFs), M-THBQ (M = Fe, Co, Mn, THBQ = tetrahydroxybenzoquinone), are synthesized and characterized. Their structures are determined as cubic cell in the group of Pm-3 from powder X-ray diffraction data, and their properties of electronic, magnetic and spectroscopic are also investigated. They are all semiconductors, and Fe-THBQ exhibits the air-stable n-type thermoelectric characteristic as its Seebeck coefficient reaches -130 μV K-1, and the electrical conductivity is 2.7 x 10-4 S cm-1 at 300 K. Additional, M-THBQ are paramagnetic, and the value of Weiss constant of Fe-THBQ is -219.37 K, indicating the existence of robust intramolecular antiferromagnetic exchanges. Meanwhile, they display strong absorption bands in the range of 220 to 1000 nm, suggest M-THBQ could have the potential to become photoabsorbers, and Fe-THBQ exhibits a narrow bandgap of 0.63 eV according to the ultraviolet absorption edge spectrum. The successful preparation of M-THBQ enriches the family of 3D magnetic conductive MOFs.