Conductive Metal-Organic Frameworks as Ion-to-Electron Transducers in Potentiometric Sensors

This paper describes an unexplored property of conductive metal-organic frameworks (MOFs) as ion-toelectron transducers in the context of potentiometric detection. Several conductive two-dimensional MOF analogues were drop-cast onto a glassy carbon electrode and then covered with an ion-selective membrane to form a potentiometric sensor. The resulting devices exhibited excellent sensing properties toward anions and cations, characterized by a near-Nernstian response and over 4 orders of magnitude linear range. Impedance and chronopotentio-metric measurements revealed the presence of large bulk capacitance (204 +/- 2 mu F) and good potential stability (drift of 11.1 +/- 0.5 mu A/h). Potentiometric water test and contact angle measurements showed that this class of materials exhibited hydrophobicity and inhibited the formation of water layer at the electrode/membrane interface, resulting in a highly stable sensing response with a potential drift as low as 11.1 mu tA/h. The property of ion-to-electron transduction of conductive MOFs may form the basis for the development of this class of materials as promising components within ion-selective electrodes.