Inverse conductance signal outputs of solid-state AgCl electrochemistry dependent on counteranions of Ag-MOFs

Metal-organic frameworks (MOFs) as crystalline materials have been extensively applied in the electrochemical sensing. However, the influence of the counteranion of MOFs on electrochemical analysis was rarely reported. In this work, three Ag-MOFs [Ag3(L)3](NO3)3 (A1), [Ag3(L)3](CF3SO3)3 (A2) and [Ag2(L)(NO3)2] (A3) with the same ligand of 1,1,2,2-tetrakis(4-(1H-pyrazol-1-yl)phenyl)ethene (L) but different counteranions were utilized to explore their electrochemical detection performance for chloride (Cl−) ions based on the electrochemical redox of solid-state AgCl. It is interesting to find that the solid-state AgCl derived from A2 with CF3SO3− counteranions exhibits inverse conductance signal output compared with that derived from A1 with counteranions of non-coordinated NO3− or by A3 with coordinated NO3−. Besides, the signals of peak potentials for the solid-state AgCl derived from these Ag-MOFs are stable, which showed excellent linear relationship and high sensitivity, favorable for the further applications. This is the first example of the counteranions of MOFs determined electrochemical sensing of chloride, and revealed the importance of the counteranions of MOFs in the field of the electrochemical sensing.