Antimonotungstate-Based Heterometallic Framework Formed by the Synergistic Strategy of In Situ-Generated Krebs-Type Building Units and the Substitution Reaction and Its High-Efficiency Biosensing KRAS Gene

A novel antimonotungstate (AT)-based heterometallic framework {[Er(H₂O)₆]₂[Fe₄(H₂pdc)₄(B-β-SbW₉O₃₃)₂]}·50H₂O (<b>1</b>, H₂pdc = pyridine-2,5-dicarboxylic acid) was obtained through a synergistic strategy of in situ-generated transition-metal-encapsulated polyoxometalate (POM) building units and the substitution reaction. Its structural unit is composed of a tetra-Fe^III-substituted Krebs-type [Fe₄(H₂pdc)₄(B-β-SbW₉O₃₃)₂]^6- subunit and two [Er(H₂O)₆]³⁺ cations. This subunit can be regarded as a product of carboxylic oxygen atoms of H₂pdc ligands replacing active water ligands in the [Fe₄(H₂O)₁₀(B-β-SbW₉O₃₃)₂]^6- species. Apparently, the substitution action of carboxylic oxygen atoms of H₂pdc ligands for active water ligands, together with the coordination function of Er³⁺ ions, plays a connection role in the architecture of the three-dimensional (3-D) heterometallic framework. Based on the stability and high redox activity of <b>1</b>, a glassy carbon electrode modified by <b>1</b> is used for the construction of an electrochemical biosensor (ECBS). Thus, such <b>1</b>-based ECBS can sensitively detect the KRAS gene (a key genetic marker for identifying the occurrence of malignant tumors) and displays a low detection limit (0.106 pM), high selectivity, and reproducibility. This work not only provides a feasible approach to prepare novel multicomponent POM-based heterometallic frameworks but also establishes a new platform for biosensing the KRAS gene and extends the application scope of POM-based functional materials.