Pei Tang

This review summarizes and provides an outlook on the possible routes for methane conversion to valuable fuel and chemicals.

We report an efficient, highly selective, and low temperature graphene-catalyzed reaction process for one-step oxidation of benzene to phenol with hydrogen peroxide as the oxidant. The chemically converted graphene (CCG) from small graphite was used as the catalyst. The conversion of benzene reaches 18%, with phenol being the sole product. The catalyst was reusable and very stable. By XPS, C K-edge X-ray absorption spectra, benzene-TPD, and kinetic measurements, it was concluded that the moderate H2O2 activation rate, good benzene adsorption ability, and balanced kinetic control over the oxidation reaction are responsible for the outstanding catalytic performance of the metal-free catalyst.

A heterogeneous, inexpensive, and environmentally friendly graphene oxide catalytic system for the C-H bond arylation of benzene enables the formation of biaryl compounds in the presence of aryl iodides. The oxygen functional groups in these graphene oxide sheets and the addition of KOtBu are essential for the observed catalytic activity. Reactions with various model compounds and DFT calculations confirmed that these negatively charged oxygen atoms promote the overall transformation by stabilizing and activating K(+) ions, which in turns facilitates the activation of the C-I bond. However, the graphene π system also greatly facilitates the overall reaction as the aromatic coupling partners are easily adsorbed.

The building blocks of the well-defined and easily modified carbon-bond structure of graphene sheet units bring unique characteristics to carbon materials. Especially when these carbon materials are nanosized, their tunable electronic states, giant conjugated structures, oxygen groups on the defects of graphene sheets, and various dopants all help make the materials active in liquid-phase catalytic reactions. In this mini-review, we mainly focus on the liquid-phase reactions catalyzed by carbon nanomaterials, and the related mechanisms are discussed on the basis of their structure fundamentals. In the final section, we also provide our perspectives on this rapidly developing carbocatalysis field.