Environmentally benign benzyl alcohol oxidation and C-C coupling catalysed by amide functionalized 3D Co(II) and Zn(II) metal organic frameworks

摘要

The new 3D metal-organic frameworks (MOFs) [Co(1 kappa N;2 kappa OO'-mu-L)(2)](n).4n(DMF).1.5n(H2O) (1) and [Zn-2(1 kappa N;2 kappa O-mu-L)(2)(kappa O-4-mu(4)-BTC)](n).3n(DmF).2n(H2O) (2) [L = 4-(pyridin-4-ylcarbamoyl)benzoate; BTC = benzene-1,3,5-tricarboxylate] have been synthesized from the pyridyl amide functionalized benzoic acid (HL). They were characterized by elemental, FT-IR, powder X-ray and single crystal X-ray diffraction analyses. Topological analysis of 1 discloses a 2,3,7-connected trinodal net with a 4-connected uninodal net with 2-fold interpenetrating networks, whereas that of 2 shows a dia topology. The solid-state photoluminescent properties of HL and 2 were also investigated. The heterogeneous catalytic activity of 1 and 2, under eco-friendly conditions, was assessed in benzyl alcohol oxidation and C-C bond formation model reactions. 1 has good activity in the solvent-free microwave-assisted oxidation of benzyl alcohol to benzaldehyde using tert-butyl hydroperoxide ((BuOOH)-Bu-t, TBHP) as oxidizing agent (yields up to 89%). Although with a lower activity, MOF2 with a redox inactive Zn(II) site, also catalyses such alcohol oxidation, which is explained by DFT calculations according to a mechanism of a similar type to that followed by the peroxidative alkane oxidation. 2 is the most active one in the ambient temperature sonochemical Knoevenagel condensation of benzaldehyde and malononitrile (yields up to 94%) and in the ambient temperature Henry C-C coupling reaction of benzaldehyde with nitroethane in water (yields > 99%), showing appreciable diastereoselectivity towards the syn isomer. The recyclability of catalysts 1 and 2 was evaluated. (C) 2020 Elsevier Inc. All rights reserved.