Three inorganic–organic hybrid materials based on octamolybdates, d¹⁰ metals, and multidentate N-donor ligands, namely, [Zn₄(htpmb)₂(θ-Mo₈O₂₆)(H₂O)_6.5]·0.5H₂O (1), [Zn₆(htpmb)₂(γ-Mo₈O₂₆)₂(SO₄)(H₂O)₆]·6.5H₂O (2), and [Cd₂(htpmb)(γ-Mo₈O₂₆)(H₂O)₂]·4.5H₂O (3), where htpmb = hexakis(3-(1,2,4-triazol-4-yl)phenoxy-methyl)benzene, have been synthesized under hydrothermal conditions. Compound 1 shows a 3D framework based on a rare [θ-Mo₈O₂₆]⁴⁻ isomer with binodal (5,6)-connected (3²·4³·5·6³·7)(3²·4⁴·5⁴·6²·7³) topology. Compound 2 displays a 3D framework with pentanodal (4,5,6,6,7)-connected (3²·4·5·6²)(3²·4²·5²·6³·8)(3⁴·4²·5²·6⁴·7²·8)(3⁴·4²·5²·6⁶·9)(3⁴·4³·5·6⁸·7⁵) topology. Compound 3 exhibits a 3D framework with pentanodal (3,4,4,6,6)-connected (3·6·7)(3²·4·6²·7)(3⁴·4²)(3²·6⁶·7⁶·10)(3³·4·6³·7⁴·8⁴) topology. Their structures have been characterized by infrared spectra (IR), elemental analyses, powder X-ray diffraction (PXRD), thermogravimetric analysis, and optical band gaps. The luminescent properties and electrochemistry behaviors of compounds 1–3 have been studied. Moreover, the photocatalytic activities for methylene blue (MB) degradation of 1–3 under UV light irradiation have also been investigated in detail.