Secondary spacer modulated assembly of polyoxometalate based metal–organic frameworks

To investigate the influence of a secondary spacer on the resulting structures of POMOFs containing pytz, five new compounds with different dimensionalities, [Cu5(2-pytz)6(H2O)4][SiMo12O40]·3H2O (1), [Cu3(2-pytz)4bipy][H2SiMo12O40]·bipy (2), [Cu3(2-pytz)2(bipy)4(H2O)6][H4SiW12O40]2·6H2O (3), [Cu2(2-pytz)(phen)(OH)]2[SiW12O40]·H2O (4), [Cu3(4-pytz)4(H2O)4][H2SiW12O40]·2H2O (5), were synthesized. When only 2-pytz was employed, compound 1 with a 3D framework was obtained, whereas when the secondary spacers (4,4′-bipy, phen and 4-pytz) were introduced into the reaction system of 1, compounds 2–5 were obtained and exhibit a broad range of structures, including 0D, 1D, 2D and 3D frameworks. It can be observed from the architectures of compounds 1–5 that the secondary spacers have a great effect on the structures of the MOFs, which results in the formation of various dimensional POMOF compounds. Additionally, photocatalytic experiments of 1–5 for the photocatalytic degradation of RhB under UV irradiation were also investigated.