Linker Redox Mediated Control of Morphology and Properties in Semiconducting Iron‐Semiquinoid Coordination Polymers**

Abstract

The emergence of conductive 2D and less commonly 3D coordination polymers (CPs) and metalorganic frameworks (MOFs) promises novel applications in many fields. However, the synthetic parameters for these electronically complex materials are not thoroughly understood. Here we report a new 3D semiconducting CP Fe 5 (C 6 O 6 ) 3 , which is a fusion of 2D Fe-semiquinoid materials and 3D cubic Fe x (C 6 O 6 ) y materials, by using a different initial redox-state of the C 6 O 6 linker. The material displays high electrical conductivity (0.02 S cm À 1 ), broad electronic transitions, promising thermoelectric behavior (S 2 σ = 7.0 × 10 À 9 W m À 1 K À 2 ), and strong antiferromagnetic interactions at room temperature. This material illustrates how controlling the oxidation states of redox-active components in conducting CPs/MOFs can be a "pre-synthetic" strategy to carefully tune material topologies and properties in contrast to more commonly encountered post-synthetic modifications.

Anchoring π‐d Conjugated Metal–Organic Frameworks with Dual‐Active Centers on Carbon Nanotubes for Advanced Potassium‐Ion Batteries

“…The Dirac bands crossing the Fermi level in the X-S and Y-Γ planes indicates that Cu-HATNH has metallic properties in the conjugate plane direction, and that electrons can be transported in the 2D plane direction. [34] Moreover, the extensive overlap between the O 2p and Cu 3d orbitals resulted in orbital hybridization, which is consistent with the large electron delocalization induced by 𝜋-d conjugation.…”

Broad Electronic Modulation of Two-Dimensional Metal–Organic Frameworks over Four Distinct Redox States

“…Discrete redox tuning is a unique feature of 2D MOFs that can influence conductivity by modulating redox-hopping as well as band-like charge transport pathways . Redox changes can occur spontaneously during synthesis or rationally through post-synthetic modification . There are several examples where discrete 1–2 electron redox changes have switched or modified properties in MOF materials, − but their synthetic tunability and porosity suggest that even greater redox-flexibility should be possible with appropriate metal and linker combinations …”

Redox Chemistry Mediated Control of Morphology and Properties in Electrically Conductive Coordination Polymers: Opportunities and Challenges

“…The related quinoidal linkers hexahydroxybenzene (HHB) or tetrahydroxy-1,4-quinone (THQ) have many accessible redox isomers and several possible intermediates as shown in Figure 3A. 36 Materials synthesized with these linkers have demonstrated variable and unpredictable in situ redox chemistry, which has a dramatic effect on both morphology and physical properties. For example, the first 2D semiconducting MOF featuring this motif, Cu-HHB, was synthesized in 2018 by reacting Cu 2+ with either HHB or THQ.…”