The selective detection of toxic Hg(II) ions is of great significance for industrial processing and environmental remediation. Herein, a novel copper(I) metal–organic framework [Cu3Cl3(bimpy)3] (1) (bimpy = 3,5-bis(1-imidazolyl)pyridine) was constructed by a solvothermal method. Single-crystal X-ray analysis shows that complex 1 is a 2-fold interpenetrated three-dimensional structure with a tfj topology, exhibiting high thermal stability and water stability. Complex 1 was used to modify a glassy carbon electrode (GCE) for the determination of Hg(II) in 0.1 M phosphate buffer solution (PBS) at pH = 7.0. However, on account of the poor electron-conductive property of complex 1, acetylene black (AB) was introduced into complex 1 to improve its electrochemical sensing activity. The electrochemical sensing property of AB and the complex 1 modified GCE was investigated by cyclic voltammetry and chronoamperometric tests. Under the optimal conditions, AB/complex 1/GCE exhibits a high sensitivity of 16.85 μA μM−1 cm−2 and a low limit of detection of 1.01 nM in the wide linear range from 2.0 μM to 64 μM. AB/complex 1/GCE could also be applied for detecting Hg(II) ions in tap water and river water. The aptasensor provides a valuable tool with satisfactory anti-interference, reproducibility, repeatability, simple preparation, and satisfactory applicability for the sensing of Hg(II) ions. [ABSTRACT FROM AUTHOR]