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

• A MOF-based potentiometric Cu2+ sensor was proposed without ion selective membrane. • The Cu 3 (HHTP) 2 plays a bifunctional role of ion recognition and ion-to-electron transduction. • The sensor discloses features of fast response, organic solvent tolerance and short conditioning. 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 Cu 3 (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. [ABSTRACT FROM AUTHOR]