Ceria nanorods were investigated using in situ Raman and FTIR spectroscopies for CO adsorption and subsequent reaction with water at 200 and 350 °C. The involvement of defects in ceria nanorods during CO adsorption and reaction with H 2 O is dependent on the temperature. At 200 °C, most of the carbonate and formate species formed in CO do not involve the formation of defects, while at 350 °C all of the carbonates and formates formed can be correlated to the formation of defects (15% by formates and 85% by mono/bidentate carbonates). Finally, at 350 °C very stable polydentate carbonates are formed that do not induce defects and cannot be regenerated with water.
The
defect chemistry of reduced ceria nanoshapes was investigated
using in situ Raman and FTIR spectroscopy. Octahedral- and rod-shaped
particles behave similarly upon exposure to CO in terms of formation
of anion Frenkel pair defects and oxygen vacancies. This similarity
is attributed to the preferential exposure of (111) surfaces in both
type of particles. Cube-shaped particles terminated with (100)-oriented
surfaces exhibit very different defect behavior in CO, revealing formation
of oxygen vacancy defects at the expense of existing anion Frenkel
pairs. Octahedra and rods, prereduced in H2, can be further
reduced with CO. In contrast, prereduced cubes can reactively adsorb
CO, forming surface-bicarbonate, only via converting Frenkel-pair
defects to oxygen vacancies, without any further net reduction of
the ceria.
Difluoromethylthioester compounds are yet another important kind of organofluorine compound and are reported here for the first time. They can be efficiently synthesized from various aldehydes. The synthetic method features mild reaction conditions, good tolerance of functional groups, broad substrate scope, and importantly, no metal is involved in the reaction. The approach has the potential to become an important tool for the late-stage functionalization of advanced synthetic intermediates, and should have many applications in medicinal chemistry.
The utilization of the transient directing strategy into the direct oxidative dehydrogenative arylation of aldehydes with arenes was reported for the first time. Featured by mild reaction conditions, good functional group compatibility, and great regioselectivity, the method should find broad applications in new medicine and material development and discovery processes.
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