Reversible single-crystal-to-single-crystal transformation and highly selective adsorption property of three-dimensional cobalt(II) frameworks

Article abstract of DOI:10.1021/ic101618n

A three-dimensional (3D) coordination polymer, [Co₃(L) ₂(BTEC)(H₂O)₂] · 2H₂O [1, HL = 3,5-di(imidazol-1-yl)benzoic acid, H₄BTEC = 1,2,4,5- benzenetetracarboxylic acid], with tfz-d topology has been hydrothermally synthesized. The framework of 1 has high thermal stability and exhibits single-crystal-to-single-crystal (SCSC) transformations upon removing and rebinding the noncoordinated and coordinated water molecules. X-ray crystallographic analyses revealed that the coordination geometry of Co(II) changes from octahedral to square pyramid upon dehydration, accompanying the appearance of one-dimensional (1D) open channels with dimensions of 2.0 × 2.8 A. The dehydrated form [Co₃(L)₂(BTEC)] (2) exhibits highly selective adsorption of water molecules over N₂,CH ₃OH, and CH₃Ch₂OH, which could be used as sensors for water molecules. Furthermore, the magnetic properties of 1 and 2 were investigated, showing the existence of ferromagnetic interaction between the Co(II) atoms within the trinuclear subunit.