C10H6NO2Cd(NO3)·2H2O: a birefringent crystal with an enlarged band-gap derived from covalent edge-sharing connection

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.