A new host 3D copper(I/II)-pyrazinecarboxylate framework intercalated with Keggin polyoxotungstates

Two new Cu(I/II) coordination polymers based on α-Keggin polyoxotungstates, Cu₆(2-pzc)₅(H₂O)₂(XW₁₂O₄₀)]·H₂O (X = Si, 1; Ge, 2) (2-pzc = 2-pyrazinecarboxylate), have been synthesized hydrothermally and characterized structurally. Single crystal structure analysis reveals that they are isomorphic, and exhibit a novel 3D framework constructed from Cu(I/II) ions and 2-pzc ligands, in which there exist nano-sized channels viewed along the a axis and the c axis. The XW₁₂O₄₀]⁴⁻ anions are filled in the channels, acting as not only a template, but also a hexa-dentate ligand. Additionally, the photocatalytic hydrogen production of 1 and 2 was investigated. It is found that 1 and 2, as heterogeneous catalysts, exhibit the photocatalytic activity in the UV region.