Hydrothermal reaction of diaminomaleonitrile and copper salts under different conditions resulted in copper cyanide coordination polymers {[Cu(H 2O)(NH 3) 4][Cu 3(CN) 5].H 2O} n ( 1), {(CH 3) 4N[Cu(H 2O)(NH 3) 4][Cu 4(CN) 7]} n ( 2), and {(CH 3OH 2) 2[Cu 2(CN) 3]} n ( 3). 1 and 2 are new mixed-valence Cu(I,II), two 3D organic-inorganic molecular framework complexes that exhibit ionic inclusion. 3 is an open copper cyanide framework hosting a guest molecule. Cyanides in 1, 2, and 3 are produced by in situ C-C bond cleavage of diaminomaleonitrile, and then the remaining product is oxidized to form an oxalate group. The potential porosity of the hydrated coordination polymer 3 was estimated using a computational method based on Connolly's algorithm.