Aerobic Oxidation of Benzylic Alcohols Catalyzed by Metal−Organic Frameworks Assisted by TEMPO

Cu3(BTC)2 (BTC: 1,3,5-benzenetricarboxylate) combined with TEMPO as cocatalyst is an effective and reusable heterogeneous catalyst to effect the aerobic oxidation of benzylic alcohols in acetonitrile to the corresponding benzaldehydes under mild temperature at atmospheric pressure. The main deactivation process was attributed to the formation of carboxylic acids arising from the overoxidation of the aromatic aldehyde acting as poisons, coordinating to the free Cu(II) sites and blocking the pores. Comparison with copper acetate as a soluble, homogeneous system established that immobilization of the Cu(II) in the rigid crystal structure of Cu3(BTC)2 does not diminish the intrinsic catalytic activity of this transition metal ion.