A New Electrically Conducting Metal–Organic Framework Featuring U-Shaped cis-Dipyridyl Tetrathiafulvalene Ligands

• Main Authors: Monica A. Gordillo, Paola A. Benavides, Kaybriana Spalding, Sourav Saha
• Format: Article
• Language: English
• Published: Frontiers Media S.A. 2021-10-01
• Series: Frontiers in Chemistry
• Subjects: metal-organic frameworks; redox-active; tetrathiafulvalene; electrical conductivity; iodine
• Online Access: https://www.frontiersin.org/articles/10.3389/fchem.2021.726544/full

A new electrically conducting 3D metal-organic framework (MOF) with a unique architecture was synthesized using 1,2,4,5-tetrakis-(4-carboxyphenyl)benzene (TCPB) a redox-active cis-dipyridyl-tetrathiafulvalene (Z-DPTTF) ligand. While TCPB formed Zn2(COO)4 secondary building units (SBUs), instead of connecting the Zn2-paddlewheel SBUs located in different planes and forming a traditional pillared paddlewheel MOF, the U-shaped Z-DPTTF ligands bridged the neighboring SBUs formed by the same TCPB ligand like a sine-curve along the b axis that created a new sine-MOF architecture. The pristine sine-MOF displayed an intrinsic electrical conductivity of 1 × 10−8 S/m, which surged to 5 × 10−7 S/m after I2 doping due to partial oxidation of electron rich Z-DPTTF ligands that raised the charge-carrier concentration inside the framework. However, the conductivities of the pristine and I2-treated sine-MOFs were modest possibly because of large spatial distances between the ligands that prevented π-donor/acceptor charge-transfer interactions needed for effective through-space charge movement in 3D MOFs that lack through coordination-bond charge transport pathways.