A novel three-dimensional CdII coordination framework, namely, poly[{μ-bis[4-(2-methylimidazol-1-yl)phenyl] ether-κ2 N 3:N 3′}(μ-naphthalene-1,4-dicarboxylato-κ3 O 1:O 4,O 4′)cadmium(II)], [Cd(C12H6O4)(C20H18N4O)] n or [Cd(1,4-NDC)(BMIOPE)] n , where 1,4-H2NDC is naphthalene-1,4-dicarboxylic acid and BMIOPE is bis[4-(2-methylimidazol-1-yl)phenyl] ether, has been prepared and characterized by single-crystal X-ray diffraction, elemental analysis, IR spectroscopy and thermogravimetric analysis. The compound displays a novel fourfold interpenetrating diamond-like network. In addition, it not only shows a strong fluorescence emission in the solid state, but also exhibits excellent photocatalytic activity for the degradation of methylene blue (MB) at room temperature.