{[Co2(btec)(2,2′-bipy)2]·H2O}n metal–organic framework: Structure and activity in the solvent-free oxidation of cyclohexene with oxygen

A Co (II) metal–organic framework (MOF) {[Co2(btec)(2,2′-bipy)2]·H2O}n (H4btec: 1,2,4,5-benzenetetracarboxylic acid; 2,2′-bipy: 2,2′-bipyridine) was hydrothermally synthesized and characterized using X-ray crystallographic analysis, Fourier transform infrared spectroscopy, elemental analysis, X-ray diffraction, scanning electron microscopy, transmission electron microscopy and N2 adsorption/desorption. Its catalytic performance was examined for the allylic oxidation of cyclohexene with oxygen under solvent-free conditions. It acted as a heterogeneous catalyst, which was deactivated in catalyst recycling and regenerated through treatment with a scCO2-expanded ethanol system. The inhibitive effect of H4btec and other ligands on cyclohexene oxidation was detected, presumed to be caused by hydrogen-bonding interaction between the H4btec and a 2-cyclohexene-1-hydroperoxide intermediate.