Isolated Indium Hydrides in CHA Zeolites: Speciation and Catalysis for Nonoxidative Dehydrogenation of Ethane

The
study of the formation, characterization, and functionality
of isolated surface hydrides on solid materials is a formidable task
because of the complexity of solid surfaces and the difficulty of
analyzing structures in solids. Herein, we found the formation of
indium (In) hydride species supported by CHA zeolites. The In hydrides
were formed by treatment of an In-exchanged CHA zeolite (In-CHA) with
H2 at high temperatures (>773 K). In situ Fourier transform infrared (FTIR) spectroscopy and density functional
theory (DFT) calculations revealed that an [InH2]+ ion on a framework anionic site is a plausible structure. In-CHA
exhibited high selectivity and durable catalytic activity for the
nonoxidative dehydrogenation of ethane for at least 90 h. Kinetic
and in situ spectroscopic studies as well as transition
state (TS) calculations suggested that [InH2]+ ions serve as catalytically active sites for selective dehydrogenation
using In-CHA.