Study of a hydrothermal reaction system of copper, imidazole and polyoxometalates: selective assembly of a 3D porous metal–organic pseudo-rotaxane framework and encapsulation of polyoxometalate clusters

Abstract

Three new compounds, [Cu(bimb)]₂(HPW₁₂O₄₀)·3H₂O (1), (H₂bimb)₂SiW₁₂O₄₀ (2) and (H₂bimb)₃CoW₁₂O₄₀ (3) (bimb = 1,4-bis(imidazol-1-ylmethyl)biphenyl), have been synthesized under the same hydrothermal conditions. Structural characterizations by single-crystal X-ray diffraction show that compound 1 possesses a porous metal–organic pseudo-rotaxane framework in which [PW₁₂O₄₀]³⁻clusters are encapsulated, whereas compounds 2 and 3 are common supramolecular compounds. The distinct structure of compound 1 suggests that the porous framework may selectively encapsulate the polyoxometalate clusters, although the three polyoxometalate clusters have subtle structural differences. Catalytic photodegradation of organic dye RhB by compounds 1–3 has been studied.