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.

Graphical abstractTwo isomorphic 3D 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-pyrazinecarboxylates), have been synthesized hydrothermally and characterized structurally. This is the first example of a 3D framework constructed from Cu(I/II) ions and 2-pzc ligands by employing POMs as a template. Additionally, the photocatalytic hydrogen production of 1 and 2 was investigated.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► A 3D Cu(I/II)/2-pzc framework intercalated with Keggin polyoxotungstates. ► A 3D Cu(I/II)/2-pzc framework templated by Keggin polyoxotungstates. ► The nano-size channels in the 3D Cu(I/II)/2-pzc framework. ► Photocatalytic hydrogen production of Cu(I/II) coordination polymers based on POMs.