Tuning Electrical‐ and Photo‐Conductivity by Cation Exchange within a Redox‐Active Tetrathiafulvalene‐Based Metal–Organic Framework

Microporous Zr-metal-organic frameworks based-nanocomposites for thermoelectric applications

In the area of energy storage and conversion, Metal-Organic Frameworks (MOFs) are receiving more and more attention. They combine organic nature with long-range order and low thermal conductivity, giving them qualities to be potentially attractive for thermoelectric applications. To make the framework electrically conductive so far, thermoelectricity in this class of materials requires infiltration by outside conductive guest molecules. In this study, an in-situ polymerization of conductive polyaniline inside the porous structure of MOF-801 was conducted to synthesize PANi@MOF-801 nanocomposites for thermoelectrical applications. The growth of polyaniline chains of different loadings inside the host MOF matrix generally enhanced bulk electrical conductivity by about 6 orders of magnitude, leading to Seebeck coefficient value of -141 µVK-1 and improved thermal stability. The unusual increase in electrical conductivity was attributed to the formation of highly oriented conductive PANi chains inside the MOF pores, besides host-guest physical interaction, while the Seebeck coefficient enhancement was because of the energy filtering effect of the developed structure. Modulating the composition of PANi@MOF-801 composites by varying the aniline: MOF-801 ratio in the synthesis bath from 2:1 and 1:1 to 1:2 leads to a change in the semiconductor properties from p-type semiconductor to n-type. Among the examined composites with n-type semiconducting properties exhibited the highest ZT value, 0.015, and lowest thermal conductivity, 0.24 Wm-1 K-1. The synthesized composites have better performance than those recently reported for a similar category of thermoelectric materials related to MOF-based composites.

Interpenetration of Donor-Acceptor Hybrid Frameworks for Highly Sensitive Thermal Sensors

Donor-acceptor (D-A) alignment that integrates D-A pairs into the modular and versatile crystalline metal-organic frameworks is a powerful strategy to precisely fabricate multifunctional materials with unique optoelectronic properties and applications at the molecular level. Herein, we reported an unprecedented threefold interpenetrating D-A hybrid framework by incorporating an electron-deficient linear viologen zwitterion into the lead-halide systems. The 1D iodoplumbate nanoribbon and interpenetrating close-packed D-A structure endowed this hitherto unknown semiconductive alignment with the anisotropic conductivity and high stability. When used in a thermal sensor, it presented exceptional electrical properties with a high sensitivity (high thermal index B of 4671 K) and decent temperature coefficient of resistivity (0.72% °C^-1) in wide operational temperature ranges (40-220 °C), which are among the best of the related thermistors. This work develops a pathway to bridge the gaps between hybrid materials and electron devices.