Nanostructured oxides find multiple uses in a diverse range of applications including catalysis, energy storage, and environmental management, their higher surface areas, and, in some cases, electronic properties resulting in different physical properties from their bulk counterparts. Developing structure-property relations for these materials requires a determination of surface and subsurface structure. Although microscopy plays a critical role owing to the fact that the volumes sampled by such techniques may not be representative of the whole sample, complementary characterization methods are urgently required. We develop a simple nuclear magnetic resonance (NMR) strategy to detect the first few layers of a nanomaterial, demonstrating the approach with technologically relevant ceria nanoparticles. We show that the 17O resonances arising from the first to third surface layer oxygen ions, hydroxyl sites, and oxygen species near vacancies can be distinguished from the oxygen ions in the bulk, with higher-frequency 17O chemical shifts being observed for the lower coordinated surface sites. H217O can be used to selectively enrich surface sites, allowing only these particular active sites to be monitored in a chemical process. 17O NMR spectra of thermally treated nanosized ceria clearly show how different oxygen species interconvert at elevated temperature. Density functional theory calculations confirm the assignments and reveal a strong dependence of chemical shift on the nature of the surface. These results open up new strategies for characterizing nanostructured oxides and their applications.

The acidity and unique porous structures of zeolites play an important role in controlling the activity and selectivity of many zeolite-based catalysts. Although (27)Al, (29)Si and (1)H NMR spectroscopy represent standard analytical tools with which to study these materials, (17)O-NMR investigations are much less routine, owing to the very low natural abundance of (17)O (0.037%), its relatively low resonant frequency and its large quadrupole moment. (17)O-NMR resonances from framework oxygen sites in a variety of zeolites have been detected, but the (17)O-NMR resonance from oxygen directly bound to the Brønsted acid site (Si-O(H)-Al) has remained elusive. Here we report the direct observation of this resonance in dehydrated zeolite HY, by using high magnetic-field strengths. (17)O-(1)H double-resonance NMR experiments are used to prove unambiguously that the (17)O signal arises from O nearby H atoms. A large quadrupolar coupling constant, the measure of the local distortion of this site, of 6.6 MHz is determined, which is similar to that obtained in ab initio calculations of zeolite HY-like clusters; this value drops to 5 MHz on acetone binding. The results presented in this paper open up methods for characterizing zeolite acidity and investigating H(+)-sorbent interactions.

Selective conversion of syngas (CO/H ) into C oxygenates is a highly attractive but challenging target. Herein, we report the direct conversion of syngas into methyl acetate (MA) by relay catalysis. MA can be formed at a lower temperature (ca. 473 K) using Cu-Zn-Al oxide/H-ZSM-5 and zeolite mordenite (H-MOR) catalysts separated by quartz wool (denoted as Cu-Zn-Al/H-ZSM-5|H-MOR) and also at higher temperatures (603-643 K) without significant deactivation using spinel-structured ZnAl O |H-MOR. The selectivity of MA and acetic acid (AA) reaches 87 % at a CO conversion of 11 % at 643 K. Dimethyl ether (DME) is the key intermediate and the carbonylation of DME results in MA with high selectivity. We found that the relay catalysis using ZnAl O |H-MOR|ZnAl O gives ethanol as the major product, while ethylene is formed with a layer-by-layer ZnAl O |H-MOR|ZnAl O |H-MOR combination. Close proximity between ZnAl O and H-MOR increases ethylene selectivity to 65 %.

Oxygen chemistry plays a pivotal role in numerous chemical reactions. In particular, selective cleavage of C–H bonds by metal oxo species is highly desirable in dehydrogenation of light alkanes. However, high selectivity of alkene is usually hampered through consecutive oxygenation reactions in a conventional oxidative dehydrogenation (ODH) scheme. Herein, we show that dual-functional Mo–V–O mixed oxides selectively convert propane to propylene via an alternative chemical looping oxidative dehydrogenation (CL-ODH) approach. At 500 °C, we obtain 89% propylene selectivity at 36% propane conversion over 100 dehydrogenation–regeneration cycles. We attribute such high propylene yieldwhich exceeds that of previously reported ODH catalyststo the involvement and precise modulation of bulk lattice oxygen via atomic-scale doping of Mo and show that increasing the binding energy of V–O bonds is critical to enhance the selectivity of propylene. This work provides the fundamental understanding of metal–oxygen chemistry and a promising strategy for alkane dehydrogenation.