Bismuth Metal–Organic Framework/Carbon Nanosphere Composites for Ultrasensitive Simultaneous Electrochemical Detection of Lead and Cadmium

An amino-functionalized bismuth metal–organic framework (Bi-BDC-NH2) composited with nitrogen-doped mesoporous carbon nanosphere (NMCS) was prepared to fabricate a Bi-BDC-NH2@NMCS electrochemical sensor for simultaneous determination of Pb(II) and Cd(II). The synthesized Bi-BDC-NH2 was granular, amorphous, and loosely aggregated to form a porous structural composition where NMCS was embedded. The large specific area and exposed sites of Bi-BDC-NH2@NMCS copromote the adsorption and electron transfer of metal ions on the electrode surface. Compared with the traditional bismuth film electrode, the Bi-BDC-NH2@NMCS electrode can improve the charge transfer, stability, and conductivity. The developed method exhibited superior stripping performance with a detection limit of 0.36 ng mL–1 for Pb(II) and 0.44 ng mL–1 for Cd(II), respectively, and a linear range of 1.0–1500 ng mL–1. It was applied to detect Pb(II) and Cd(II) in liver, fish, and shrimp samples with recoveries of 93.6–99.7% and 94.4–103.2%, respectively.