val A ratiometric electrochemical sensor for simultaneous detection of multiple heavy metal ions based on ferrocene-functionalized metal-organic framework?Based on this ratiometric electrochemical sensing platform, the simultaneous, sensitive and reliable detection of Cd2+, Pb2+ and Cu2+ was realized.The sensing platform was constructed by a composite of ferrocenecarboxylic acid functionalized metal-organic framework (MOF), Fc-NH2-UiO-66, and thermally reduced graphene oxide (trGNO), which was designated as trGNO/Fc-NH2-UiO-66.Herein, a novel ratiometric electrochemical sensing method was established for the simultaneously detection of three main heavy metal ion pollutants (Cd2+, Pb2+ and Cu2+).Xinxing Wang, Youxiao Qi, You Shen, Yue Yuan, Lindi Zhang, Chongyu Zhang, Yanhui Sun?Sensors and Actuators B: Chemical 310, 127756, 2020???????