Cu(II)-and Co(II)-containing metal–organic frameworks (MOFs) as catalysts for cyclohexene oxidation with oxygen under solvent-free conditions

Aerobic oxidation of cyclohexene over [Cu2(OH)(BTC)(H2O)]n·2nH2O (Cu-MOF, BTC = 1,3,5-benzenetricarboxylic acid) and [M2(DOBDC)(H2O)2]·8H2O (Co-and Ni-MOF, DOBDC = 2,5-dihydroxyterephthalic acid) in the absence of solvent under mild conditions was studied. It is observed that both Cu-MOF and Co-MOF can selectively oxidize cyclohexene to give 2-cyclohexen-1-ol and 2-cyclohexen-1-one as the main products, while Ni-MOF is totally inactive for cyclohexene oxidation. The mechanism of the catalytic oxidation of cyclohexene over Cu-MOF and Co-MOF has been proposed. These MOF-based catalysts are stable and recyclable under current reaction conditions. This study highlights the great potential of developing MOFs as highly stable, molecularly tunable, recyclable and reusable heterogeneous catalysts for alkenes oxidation.