Anderson-type polyoxometalate-based complexes constructed from a new ‘V’-like bis-pyridine–bis-amide ligand for selective adsorption of organic dyes and detection of Cr(vi) and Fe(iii) ions

Abstract

By introducing a new ‘V’-like bis-pyridine–bis-amide ligand 4,4′-bis(4-pyridinecarboxamide)phenylmethane (L) into the reaction system based on Anderson-type polyoxometalates [XMo₆(OH)₆O₁₈]³⁻ (X = Al or Cr), four metal–organic complexes (MOCs) 1–4, [Zn(HL)(H₂O)₂(XMo₆(OH)₆O₁₈)]·5H₂O (1: X = Al; 2: X = Cr), [Co(HL)(H₂O)₂(XMo₆(OH)₆O₁₈)]·5H₂O (3: X = Al; 4: X = Cr), have been prepared under solvothermal conditions, which have been characterized by single crystal X-ray diffraction, IR spectra, and PXRD. All structures of 1–4 involved a 2D layer that originated from XMo₆ polyoxoanions and metal ions, on both sides of which the L ligands were hanged. Complexes 1–4 showed not only outstanding selective adsorption capacities for organic dyes crystal violet, methylene blue and neutral red, but also electrochemical sensing behaviors toward Cr(VI) ions and Fe(III) ions with well-pleasing limits of detection of 0.606 nM (6.24 × 10⁻⁵ ppm) and 0.0192 μM (1.08 × 10⁻³ ppm), suggesting their potential application as multifunctional materials.