A novel 3-D cuprous iodide polymer [CuI(μ6-L)]n with a Cu/I ratio as high as 3 (1, H2L = 1,3-bis(2H-tetrazol-5-yl)benzene) has been hydrothermally synthesized. The 3-D framework of 1 is constructed by the linkages of rare 1-D cationic aggregates [CuI2+]n and anionic bi-tetrazolate bridges. 1 shows unusually thermochromic luminescent and photocatalytic properties, and its density functional theory calculation has also been studied.