Understanding the nature of active sites in metal-supported catalysts is of great importance towards establishing their structure–property relationships. The outstanding catalytic performance of metal-supported catalysts is frequently ascribed to the synergic effect of different active sites, which is however not well spectroscopically characterized. Herein, we report the direct detection of surface Zn species and ¹H–⁶⁷Zn internuclear interaction between Zn²⁺ ions and Brønsted acid sites on Zn-modified ZSM-5 zeolites by high-field solid-state NMR spectroscopy. The observed promotion of C−H bond activation of methane is rationalized by the enhanced Brønsted acidity generated by synergic effects arising from the spatial proximity/interaction between Zn²⁺ ions and Brønsted acidic protons. The concentration of synergic active sites is determined by ¹H–⁶⁷Zn double-resonance solid-state NMR spectroscopy.

Link:https://onlinelibrary.wiley.com/doi/full/10.1002/anie.201608322