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Abstract: Two cuprous iodide polymorphs formulated as [N(CH3)4][Cu2I3] α and β were synthesized, in which N(CH3)4 + template that never existed in the reaction materials are in situ generated via cleavage of C N bonds and N-alkylation reactions. Solvothermal reaction of copper source, hexamethylenetetramine and HI in methanol solution at 150°C led to α and β polymorphs. Two polymorphs have been synthesized via subtle modification of the experimental condition, which indicates that the small force is also sufficient for energy difference for polymorphs. α polymorph contains one-dimensional Cu2I3 − chain in which the copper atoms are arranged into a zigzag lattice; β polymorph is composed of novel ladder-like chains which can be considered as being built up by Cu12I18 and Cu2I3 two types of secondary building units. The UV–vis absorption spectra for α and β polymorphs were investigated in reflectance mode in the solid state at room temperature, exhibiting that they belong to potential semiconductors. The excitation and emission in α and β are very distinct, which highlight that the molecular packing in polymorphs is critical to photophysical properties. [Copyright &y& Elsevier]