Novel conjugated nanoporous alkynyl metalloporphyrin framework as effective catalyst for oxidation of toluene with molecular oxygen

A porous alkynylporphyrin conjugated organic polymer (MnE-TPP) was synthesized by Sonogashira coupling reaction with Mn(II) 5,10,15,20-tetrakis(4′-ethynylphenyl)porphyrin and Mn(II) 5,10,15,20-tetrakis(4′-bromophenyl)porphyrin as building blocks. The polymer was characterized using nitrogen adsorption–desorption isotherms, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, Fourier transform infrared and UV–visible spectroscopies, X-ray diffraction, thermogravimetry and inductively coupled plasma atomic emission spectrometry. The electrochemical behaviors of MnE-TPP were investigated by cyclic voltammetry. MnE-TPP was developed as a heterogeneous catalyst for the activation of molecular oxygen to oxidize toluene under mild conditions. The selectivity of total benzaldehyde and benzyl alcohol remained above 70.0% with a conversion of toluene up to 10.2%. The turnover number was as high as 13 653. Also, MnE-TPP remained structurally stable and the toluene conversion rate hardly decreased after 5 h of reaction and five cycles of reuse.