A label-free enrofloxacin electrochemical aptasensor constructed by a semiconducting CoNi-based metal–organic framework (MOF)

•A semiconducting bimetallic MOF material with 2D graphene-like nanostructure.•Strong aptamer immobilization and ultrasensitive detection of enrofloxacin.•Superior sensing performances on selectivity, reproducibility, stability, and applicability.•New aptasensing strategy on MOFs-based electrochemical biosensors. A semiconducting CoNi-based metal–organic framework (MOF), CoxNi3-x(HITP)2, was designed and synthesized using 2,3,6,7,10,11-hexaaminotriphenylene (HATP) as organic linker. Compared with Co3(HITP)2 and Ni3(HITP)2, CoxNi3-x(HITP)2 possesses mixed metal valences of Co2+/Co3+/Ni2+/Ni3+ and more defects within the MOF skeleton, which also shows amino-rich functionality, biocompatibility, and the intrinsic features of semiconducting MOFs, such as two-dimensional graphene-like nanostructure, high stability in water solution, and good electrochemical activity. As a consequence, the CoxNi3-x(HITP)2-based electrochemical aptasensor demonstrates superior sensing performances for enrofloxacin, with an extremely low detection limit of 0.2 fg•mL−1 and a linear range of 0.001−1 pg•mL−1, as well as high selectivity, excellent reproducibility, good stability, and wide applicability. The developed sensing strategy provides new insights into the fabrication of MOFs-based sensors for food safety, environment protection, and medical diagnosis. [Display omitted]