A new birefringent crystal, C₁₀H₆NO₂Cd(NO₃)·2H₂O, was designed by combining a π-conjugated [C₁₀H₆NO₂]⁻ group with a CdO₇N polyhedron. Notably, the experimental energy gap is 0.02 eV higher than that of the organic raw material, which resulted from a covalent edge-sharing connection, implying a new strategy to improve the band-gap of birefringent materials.