Selective oxidation over a metalloporphyrinic metal-organic framework catalyst and insights into the mechanism of bicarbonate ion as co-catalyst

A biomimetic oxidation catalyst, metalloporphyrinic metal-organic framework, was successfully constructed by manganese tetrakis (4-carboxyphenyl) porphyrin as a bridging ligand and Fe ions with a stable 3D framework. The X-ray diffraction (XRD) spectra and X-ray photoelectron spectroscopy (XPS) details demonstrated its structure formed by channels and cavities and a catalysis-promoted electronic environment, which provides a fundamental understanding of this heterogeneous catalyst. Afterwards, it was found that Fe-MMOF can be capable of catalyzing the selective oxidation of versatile natural substrates, acting as an effective peroxidase mimic. The accessibility of the open channels to substrate molecules was also discussed to reveal the steric effect of substrate on catalytic activity. Here, we divided the epoxidation process into three parts, involving formation of HCO4-, the activation of HCO4-, to form porMn(v) = O and the nucleophilic attack of substrate at the electrophilic oxygen of porMn(v) = O. Remarkably, an insight into the role of HCO3- was gained from the proposed mechanism based on the general idea about homolytic peroxide oxidation reaction. (C) 2014 Elsevier B.V. All rights reserved.