Highly Efficient Cu(II)-Pyrazoledicarboxylate Heterogeneous Catalysts for Base-Free Aerobic Oxidation of Benzylic Alcohol to Benzaldehyde with Hydrogen Peroxide as the Oxidant
A new Cu(II) pyrazoledicarboxylate coordination polymer [Cu(Hpdc)(ImH)]n (1) (H3pdc = 3,4-pyrazoledicarboxylic acid; ImH = imidazole) has been hydrothermally synthesized and characterized by elemental analysis, FT-IR, X-ray diffraction, and thermogravimetric analysis. In 1, the tetradentate Hpdc2– anion coordinated to three Cu(II) ions in a μ3-κO: κN, O’: κN’ mode, forming a two-dimensional (2D) (4,4) network; the other ImH ligand acted as a terminal ligand. Cu(II)-MOF 1 displayed high activity and selectivity in the base-free aerobic oxidation of benzyl alcohol to benzaldehyde combined with green oxidant H2O2. The catalytic system of 1 could be reused for several cycles without any obvious decay of the catalytic efficiency.