Oxidation of α C H bonds in alkyl aromatics with O2 catalyzed by highly dispersed cobalt(II) coordinated in confined reaction channel of porphyrin-based POFs with simultaneously enhanced conversion and selectivity

Abstract

To obtain oxidative functionalization of αCH bonds in alkyl aromatics with O2, 3D POFs were constructed as heterogeneous catalysts based on metalloporphyrin. In 3D POFs, porosity was designed as confined reaction channel to control excessive expansion of free radical quantity, and heterogeneous catalysis was employed to reduce oxidative transformation of partial oxidation products induced by homogeneous catalytic sites. Applied to partial oxidation of αCH bonds, enhanced conversion and selectivity were achieved simultaneously, especially in employment of POFs with residual -Br and -B[OC(CH3)2]2 being capped. In oxidation of 1-ethyl-4-nitrobenzene, conversion was increased from 38.9% to 63.1%, meanwhile selectivity towards 4-nitroacetophenone was increased from 65.5% to 91.3%. Simultaneously enhanced conversion and selectivity was attributed to controlled expansion of free radical quantity, reduced oxidative transformation of partial oxidation products, and lower temperature. An instructive reference was provided for efficient functionalization of CH bonds with O2, and for other chemical transformations involved free radicals.