Synthesis and characterization of two {Mo6}-based/templated metal–organic frameworks

Abstract

Here, we report two novel POM-based MOFs: a nano-caged hybrid compound [Ni₂(BIMB)₂(Mo^VI₄Mo^V₂O₁₉)] (1), whose cages are based on [Mo₆O₁₉]⁴⁻ units and a [Mo₆O₁₉]²⁻-templated framework [Zn₄(BIMB)₄(PO₄)₂(Mo₆O₁₉)]·2H₂O (2) (BIMB = 1,4-bis(1-imidazolyl)benzene). According to topological analysis, the first is a 3D (4,6)-connected self-penetrating framework with polycatenanes motif. In contrast, the second metal–organic framework has no interpenetration for the templated [Mo₆O₁₉]²⁻ occupying the cavity. The UV-vis absorption spectrum of 1 was investigated to prove the existence of Mo^V atoms and the typical peak at 577 nm can be attributed to Mo^V → Mo^VI charge transfer. Furthermore, the diffuse reflectivity spectrum shows that its band gap can be assessed as 3.06 eV, which can be regarded as a wide gap semiconductor. Additionally, cyclic voltammogram of compound 1 shows two redox peaks in the range of 0–800 mV in H₂SO₄ aqueous solution.