Mixed Ionic and Electronic Conductivity in a Tetrathiafulvalene-Phosphonate Metal–Organic Framework
Catarina Ribeiro, Bowen Tan, Flávio Figueira, Ricardo F. Mendes, Joaquín Calbo, Gonçalo Valente, Paula Escamilla, Filipe A. Almeida Paz, João Rocha, Mircea Dincă, Manuel Souto
Abstract
Mixed ionic-electronic conductors have great potential as materials for energy storage applications. However, despite their promising properties, only a handful of metal–organic frameworks (MOFs) provide efficient pathways for both ion and electron transport. This work reports a proton–electron dual-conductive MOF based on tetrathiafulvalene(TTF)-phosphonate linkers and lanthanum ions. The formation of regular, partially oxidized TTF stacks with short S···S interactions facilitates electron transport via a hopping mechanism, reporting a room-temperature conductivity of 7.2 × 10 –6 S cm –1 . Additionally, the material exhibits a proton conductivity of 4.9 × 10 –5 S cm –1 at 95% relative humidity conditions due to the presence of free −POH groups, enabling efficient proton transport pathways. These results demonstrate the potential of integrating electroactive building blocks along with phosphonate groups toward the development of mixed ionic-electronic conductors.