Four tetrazole-based three-dimensional (3D) metal- organic frameworks (MOFs), {[Cu-II(btz)]center dot 0.5H(2)O}(n) (1), [Cu-II(btz)](n) (1'), {[Cu-II(btz)]center dot 0.5I(2)}(n) (1'center dot 0.5I(2)), and [(CuCu2I)-Cu-II(btz)(2)](n) (2) [H(2)btz = 1,5-bis(5-tetrazolo)-3-oxapentane)], have been successfully obtained and characterized by crystallography. Compound 1 features a chiral porous framework. The bulk crystallization of 1 is composed of enantiomers la (P4(1)) and 1b (P4(3)), which has been demonstrated by the crystal structure analyses of nine crystals of 1 randomly selected. The Cotton effect displayed in the solid-state circular dichroism spectrum of 1 is therefore attributed to enantiomeric excess rather than enantiopurity. The completely dehydrated phase of 1, that is, 1', can adsorb 0.5 I-2 molecule per formula unit to yield compound 1'center dot 0.5I(2), which has been supported by single-crystal X-ray diffraction, elemental analysis, and thermogravirnetric analysis. The locations of I-2 in the pores were unambiguously determined, and the interactions between I-2 molecules and the pore structures were investigated. Compound 2 crystallizes in an achiral C2/c space group. Interestingly, the formations of chiral 1 and achiral 2 significantly depend on the reaction temperature. Between 80 and 140 degrees C, we got compound 1 as the only product. At 150 degrees C, both 1 and 2 were in coexistence in the final product. From 160 to 180 degrees C, only compound 2 was obtained. More interestingly, treatment of the crystals of 1 or the mixture of 1 and 2 obtained at 150 degrees C in their mother liquor at 170 degrees C yielded the crystals of 2 in a single phase.