Conductive metal organic framework for ion-selective membrane-free solid-contact potentiometric Cu2+ sensing

Abstract

The conductive metal organic framework (MOF) discloses efficient electron transfer ability and its specific framework structure could realize ion recognition. The state-of-the-art solid-contact ion-selective electrodes (SC-ISEs) rely on both solid contact (SC) and ion-selective membrane (ISM) for respective functions of ion-to-electron transduction and ion recognition. Herein, we report an ISM-free SC-ISE by using the conductive MOF of Cu3(HHTP)2 (Cu as metallic nodes and 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) as triphenylene-based organic linkers) as a bifunctional role of SC and ISM for Cu2+ sensing. The experimental results demonstrated a Nernstian and selective response to Cu2+ with a slope of 29.5 ± 0.3 mV dec−1. Compared with traditional Cu2+-ISM-based SC-ISEs, the potentiometric response time has been greatly reduced from ∼ 50 s to 10 s. Moreover, the ISM-free conductive MOF could offer normal potentiometric responses even under a short conditioning time in solution (minutes). In addition, organic solvent tolerance has also been proved for the ISM-free conductive MOF-based SC-ISE. This work demonstrates that the MOF could be feasible for constructing a type of ISM-free solid potentiometric ion sensors.