Two novel Anderson-type polyoxometalate-based metal–organic complexes with high-efficiency photocatalysis towards degradation of organic dyes under UV and visible light irradiation

Abstract

Two novel Anderson-type polyoxometalate (POM)-based metal–organic complexes (MOCs), namely, H{CuL_0.5¹ [CrMo₆(OH)₆O₁₈](H₂O)}·0.5L¹ (1) and {Cu₂(L²)₂[CrMo₆(OH)₅O₁₉](H₂O)₂}·2H₂O (2) (L¹ = N,N′-bis(3-pyridinecarboxamide)-1,2-ethane, L² = N,N′-bis(3-pyridinecarboxamide)-1.3-propane), were hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction, IR spectra, powder X-ray diffraction (PXRD) and thermogravimetric analyses (TGA). In complex 1, the bidentate [CrMo₆(OH)₆O₁₈]³⁻ (CrMo₆) polyoxoanions bridge the Cu^II ions to generate a 1D Cu–CrMo₆ inorganic chain, which is further connected by the μ₂-bridging L¹ ligands to form a 1D ladder-like chain. Complex 2 is a 3D POM-based metal–organic framework exhibiting a {4¹².6³} topology, which is constructed from the quadridentate CrMo₆ polyoxoanions and μ₂-bridging L² ligands. The flexible bis-pyridyl-bis-amide ligands with different spacer lengths have a significant effect on the final structures. In addition, pH shows great influence on the formation of the single-crystal phase. The photocatalytic activities of the title complexes on the degradation of methylene blue (MB) and rhodamine B (RhB) under UV and visible light have been investigated in detail.