Two unusual 3D POM-Ag frameworks with tetragonal and dodecagonal helical channels

Two new hybrid compounds with tetragonal and dodecagonal helical channels, K[Ag14(pyttz)4(H2O)2][PW12O40]2⋅(OH)⋅5 H2O (1) and K[Ag14(pyttz)4(H2O)4][HSiW12O40]2⋅H2O (2), have been hydrothermally synthesized and structurally characterized by using routine techniques. X-ray diffraction analysis shows that compounds 1 and 2 are isostructural and crystallize in the monoclinic space group P2(1)/c. A fascinating structural feature of these compounds is that they form 3D POM-Ag frameworks with helical channels, which are the first examples of helical channels that are constructed from POMs and metal atoms. Notably, there are two types of spatial orientation of the POMs, which result in the formations of left- and right-handed helical chains. Furthermore, these different helical chains are perfectly enclosed through shared POMs, thereby forming tetragonal and dodecagonal helical channels. In addition, the photocatalytic degradation of RhB by these compounds was also investigated.