Iron-Based 2D Conductive Metal–Organic Framework Nanostructure with Enhanced Pseudocapacitance

Abstract

Electrically conductive metal–organic frameworks have emerged as an attractive class of materials for sensing and energy storage applications with unique electronic properties. However, the field lacks structural diversity often because of the limited choices for metal nodes. In this regard, the incorporation of iron species has been desirable due to its rich redox chemistry. Herein, we report an Fe-based two-dimensional (2D) electrically conductive MOF with 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP), namely, Fe–HHTP, that shows redox features and mesoporosity. Fe–HHTP exhibits an electrical conductivity of 3.55 × 10–5 S cm–1 despite a large interlayer spacing of ∼6.5 Å due to N,N-dimethylformamide (DMF) coordination on the Fe nodes. Spectroscopic results confirm that Fe–HHTP exhibits a mixed valency of Fe(II)/Fe(III) with Fe(II) being dominant. Fe–HHTP boasts exceptional capacitance and apparent redox activity compared to the previously reported analogues using the same ligand. We envision that Fe–HHTP can be an excellent candidate for applications in chemical sensing and energy storage where discrete redox features are essential.