Fabrication and spectroscopic, electrochemical, and catalytic properties of a new intercalation compound of K4Nb6O17 with cationic cobalt porphyrin

A new intercalation compound of layered perovskite (K4Nb6O17·3H2O) with cationic Co-porphyrin 5,10,15,20-tetrakis(N-methylpyridinium-4-yl) porphyrinato cobalt(III), CoTMPyP, was successfully synthesized by a guest-exchange method using PrNH3+–Nb6O17 as an intermediate. The resulting nanocomposite CoTMPyP–Nb6O17 has been characterized by X-ray diffraction, elemental analysis, scanning electron microscopy and UV–vis absorption spectra. The glassy carbon (GC) electrode modified with CoTMPyP–Nb6O17 film exhibited two well-defined redox waves at −0.77 and −0.56 V, corresponding to the CoII/ITMPyP and CoIII/IITMPyP couple (vs. SCE, in pH 12.0 phosphate buffer solution). The catalytic performance of the novel catalyst CoTMPyP–Nb6O17 for the epoxidation of cyclohexene was investigated using molecular oxygen as oxidant and isobutylaldehyde as co-reductant. The intercalated cobalt porphyrin appears to be a promising catalyst owing to its good catalytic activity and selectivity. CoTMPyP–Nb6O17 could be reused and showed no appreciable decrease in activity after six reaction cycles.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (173 K)Download as PowerPoint slideHighlights► Cationic metalloporphyrin (CoTMPyP) was successfully intercalated into K4Nb6O17·3H2O. ► The spectroscopic and electrochemical properties of CoTMPyP–Nb6O17 have been studied. ► The catalyst showed good activity and selectivity for the cyclohexene epoxidation. ► The catalyst can be reused without appreciable loss of efficiency.