Construction of frustrated Lewis pairs on carbon nitride nanosheets for catalytic hydrogenation of acetylene.

Here, we studied Al or B atom-doped carbon nitride (g-CN and CN) as catalysts for H activation and acetylene hydrogenation using density functional theory calculations. The Al or B could be assembled with the surface N atoms of carbon nitride to form diverse frustrated Lewis pairs (FLPs). The results show that Al-N FLPs had lower barriers of H activation in comparison with B-N FLPs. The heterolytic H dissociation catalyzed by Al-N FLPs led to the formation of Al-H and N-H species. The Al-H species were highly active in the first hydrogenation of acetylene to CH*, yielding a mild barrier, while in the second hydrogenation step, the reaction between CH and the H of N-H species caused a relatively high barrier. Electronic structure analysis demonstrated the electron transfer in the heterolytic H cleavage and explained the activity differences in various FLPs. The results suggest that Al with the surface N of carbon nitride can act as an FLP to catalyze the H activation and acetylene hydrogenation, thus providing a new strategy for the future development of noble metal-free hydrogenation catalysts.