[Zn(3-tba)2], 1, a 1-D coordination polymer synthesised as 1 DMA, 1α, transformed to a nonporous form, 1β, upon activation. 1β underwent further transformation to the dimeric complex [Zn(3-tba)2(H2O)2], 2, above 40% RH. The reverse transformations, 2 to 1β and 1β to 1α, were accomplished by heating and exposure to DMA, respectively, and were single-crystal-to-single-crystal phase changes. Single crystal X-ray diffraction revealed that the second transformation resulted from Zn-carboxylate bond breakage and concomitant coordination of water molecules. Other solvent molecules did not induce a phase change.