Reversible One‐ to Two‐ to Three‐Dimensional Transformation in CuII Coordination Polymer

A reversible transformation between 1D, 2D, and 3D is demonstrated for the first time in coordination polymers comprising CuII ions and bidentate terephthalate (BDC2−). 1D uniform chains were reversibly transformed into 2D layers with the construction of Cu‐paddlewheels by eliminating water molecules. 2D/3D reversible transformation was achieved by removing/rebinding N,N‐dimethylformamide coordinated to the paddlewheels. These dimensional transformations significantly changed chemical and physical properties such as gas sorption and magnetism. Although the uptake in open‐framework 1D and 2D Cu‐BDC was insignificant, pronounced absorption was observed for 3D Cu‐BDC. Drastic difference in magnetic behavior is consistent with their coordination structures; uniform 1D chain of CuII in 1D Cu‐BDC and 2D sheet based on CuII‐paddlewheel dimers in 2D Cu‐BDC. Ferromagnetic behavior observed in air‐exposed 3D Cu‐BDC is attributed to the 3D structure formed by the connection of 2D sheets.