Solid-state thermal conversion of a nanoporous metal–organic framework to a nonporous coordination polymer

Abstract

A nanoporous metal–organic framework of Zn(BDC)(4,4′-Bipy)_0.5·(DMF)(H₂O)_0.5 (1·DMF·H₂O; H₂BDC = 1,4-benzenedicarboxylic acid, 4,4′-Bipy = 4,4′-bipyridine, DMF = N,N-dimethylformamide) which was also recognized as MOF-508 and has a pillared 2D square-grid net, was synthesized under reflux conditions. By thermal treatment of 1·DMF·H₂O at 350 °C, it converts to a nonporous three-dimensional coordination polymer of Zn(BDC)(4,4′-Bipy) (2). During the solid-state structural transformation of 1·DMF·H₂O to 2, a Zn(BDC) (3) unit was removed. Thus we have a mixture of compounds 2 and 3 at 350 °C. In addition, 1·DMF·H₂O and a mixture of 2 and 3 powders with microrod morphologies, were used for the preparation of ZnO nanomaterials. With calcination of the host framework of 1·DMF·H₂O, ZnO nanoprticles can be fabricated. The same process with a mixture of 2 and 3 results in the formation of agglomerated ZnO nanoparticles with similar morphology to the initial precursor.