Metal organic frameworks (MOFs) as catalysts:: A combination of Cu2+ and Co2+ MOFs as an efficient catalyst for tetralin oxidation

Two metal-organic frameworks, [Cu(2-pymo)(2)] and [Co(PhIM)(2)] (2-pymo = 2-hydroxypyrimidinolate; PhIM = phenylimidazolate), containing respectively Cu2+ and Co2+ ions and anionic diazaheterocychc ligands (pyrimidinolate and phenylimidazolate) as organic linkers, have been successfully used for the aerobic oxidation of tetralin, yielding a-tetralone (T=O) as the main product. Both materials are stable and recyclable under the reaction conditions. Kinetic studies revealed significant differences between the two MOFs, as a consequence of the different catalytic behavior of their central metal ions. [Cu(2-pymo)(2)] is highly active for the activation of tetralin to produce tetralinhydroperoxide (T-OOH), and less efficient in reacting the peroxide. Meanwhile, the use of the cobalt catalyst involves a long induction period for the reaction. However, once T-OOH is formed, Co2+ rapidly and efficiently transforms this into T=O, with high tetralone-to-tetralol ratio (T=O/T-OH of ca. 7). The combination of both materials has revealed as a convenient strategy for preparing a highly efficient, selective and reusable catalyst for the liquid phase aerobic oxidation of tetralin. (C) 2008 Elsevier Inc. All rights reserved.