Synergetic catalytic oxidation of C-H bonds in cycloalkanes and alkyl aromatics by dimetallic active sites in 3D metalloporphyrinic MOFs employing O2 as oxidant with increased conversion and unconsumed selectivity

Abstract

To realize C-H bond oxidation of hydrocarbons with high-efficiency and high-selectivity, and inhibit selectivity consumption with increased conversion, PCN-224(M1&M2) and PCN-222(M1&M2) were prepared to build dimetallic sites in synergetic catalysis and limiting catalytic region. In the production of partly oxygenated products via C-H bonds oxidation utilizing O2, PCN-224(Co&Cu) exhibited optimal catalytic performance. Conversion was increased without obvious selectivity consumption. For the typical conversion of cyclohexane to partly oxygenated products, an increase from 3.83% to 5.72% was observed from conversion compared with metalloporphyrin TCPPCo as catalyst, meanwhile the selectivity towards partly oxygenated products was slightly decreased to 88.2% from 90.5%. The excellent performance of PCN-224(Co&Cu) was mainly ascribed to that the limiting catalytic region restrained the disordered diffusion of free radicals, dimetallic centers boosted substrates oxidation by cycloalkyl hydroperoxides as oxidant, and heterogeneous catalysis inhibited the contact of partly oxygenated products with catalytic sites. The synergetic catalysis in limiting region presents a promising and innovative approach for the efficient and selective functionalization of C-H bonds with O2, and also for the realization of other fundamental chemical transformations associated with free radicals.