Cadmium ions have variable degrees of toxicity on the environment and organisms. An electrochemical sensor based on self-doped polyaniline (SPAN) modified Metal-organic Framework (SPAN@UIO-66-NH2) with high electron mobility was developed. Cyclic voltammetry and electrochemical impedance spectroscopy indicated that doping of SPAN enhanced the electron transfer rate of UIO-66-NH2 in SPAN@UIO-66-NH2. The optimized Cd2+ sensor exhibited good linear response from 0.5 mu g L-1 to 100 mu g L-1, low detection limit of 0.17 mu g L-1 (based on S/N=3), good stability, and fast response time. It showed decent reliability for detection of trace Cd2+ in natural lake and urine samples. (C) 2019 The Electrochemical Society.