A novel helical compound, Zn(Htib)(tib)PMo12O40 (1) (tib = 1, 3, 5-tris-(1-imidazolyl)-benzene) was hydrothermally synthesized. The structure has been determined by single-crystal X-ray diffraction analyses and characterized by IR, XPS, UV–Vis and XRD and elemental analyses. Single crystal X-ray analysis reveals that compound 1 possesses entangled double helixes, which is formed by a pair of right- and left- handed double helixes sharing Zn atoms and a part of tib ligands. The adjacent entangled double helixes are further fused together, and thus a wavy Zn-tib metal-organic layer is constructed. Finally, through hydrogen bonds, the neighboring Zn-tib metal-organic layers are interconnected in a staggering peak-load manner to give birth to a porous 3D supramolecular framework with large rhombus-like apertures, in which the [PMo12O40]3- (PMo12) anions were encapsulated into the open channel structure and sandwiched by the Zn-tib layers. Additionally, compound 1 exhibits high efficiency and stability, and well reproducibility towards photocatalytic degradation of RhB dye under UV irradiation. The fluorescence property of 1 was also investigated.