Construction of Functional Superhydrophobic Biochars as Hydrogen Transfer Catalysts for Dehydrogenation of N-Heterocycles

To endow metal-free materials with the high catalytic activity that is typically featured by a metal-based catalyst is yet a constant pursuit in the field of catalytic chemistry. In this work, novel functional biochars (DCNs) were prepared from wheat straw for the first time via a simple strategy of reconstructing the catalytic active sites in carbon precursors and subsequent controlled carbonization, which may be further applied in the oxidative dehydrogenation of N-heterocycles with ambient air as the oxidant. Whereas the superhydrophobicity of DCN-850 can effectively remove the only byproduct water to effectively reduce the possible effects of water on the catalyst, it also can decrease mass transfer resistance on active sites, thereby ensuring the reaction with high efficiencies and good generality. Especially, after several reuses, the activity and structures of DCN-850 remained unchanged in the catalytic system with water as a solvent. Furthermore, various characterization technologies and the model reaction were used to investigate the architectural attributes of DCNs, and the results show that there is a positive correlation between the catalytic performance and hydrophobicity of DCNs, as well as reveal that the catalytic active sites may be made up of a five-membered-ring ketone or its enol form and possibly a phenolic unit, which could be encapsulated in internal structures of catalysts and promote the reaction via the recycling of -C-C-OH and -C-C=O groups by the pathway of catalytic hydrogen transfer.