Toward Understanding and Controlling Organic Reactions on Metal Oxide Catalysts

Abstract

Metal oxides have structurally complex surfaces on which a variety of adsorption site types can occur, including cation sites, anion sites, oxygen vacancy sites, and Brønsted acid sites. These sites can catalyze the catalytic transformation of organic molecules via diverse routes, thus enabling H abstraction, O abstraction, C–C bond formation, and other reactions. This Perspective provides an update on recent advances and future directions for various organic reactions on metal oxide catalyst surfaces, particularly for C–H activation of alkanes and for C–C bond formation with organic oxygenate reactants. We put emphasis on the molecular scale details, on the active site structures required to enable the formation of kinetically relevant transition states, energetic descriptors, as well as contemporary ideas to enable low activation energies. This progress has been enabled by specialized experiments and the increased capabilities of modern electronic structure calculations.

Infrared Fingerprints of the CO2 Conversion into Methanol at Cu(s)/ZrO2(s): An Experimental and Theoretical Study

“…As pointed out in Ref. [43][44][45][46], the most viable route to form CO on ZrO 2 consists of CO 2 adsorption at an oxygen vacancy, a step that is followed by the oxygen transferring to fill the vacant site. Upon formation on ZrO 2 surface, the primary interaction of CO occurs through the carbon atom (see Figure 2 (a)) with Zr 4 + centers, which has a CÀ O stretching mode located at 2129 cm À 1 and ṽcalc = 2167 cm À 1 .…”

In Situ Growth of Mn-Co3O4 on Mesoporous ZSM-5 Zeolite for Boosting Lean Methane Catalytic Oxidation

“…It is worth noting that transition metal oxides have shown tremendous potential in this area. Transition metal oxides usually have rich valence state changes, which help to provide multiple active sites in catalytic reactions [6], thereby improving catalytic efficiency. The spinel structure of Co3O4 is the best alternative to precious metal catalysts.…”

Atomically Dispersed Palladium to Enhance the Propyne Semihydrogenation over CeO2 Catalysts

“…Propyne as a type of impurity widely presented in the propylene stream produced by the steam cracking of naphtha and propane dehydrogenation processes is harmful for downstream polymerization and thus needs to be removed from the propylene stream. – Catalytic hydrogenation of propyne achieved with supported Pd-based catalysts is normally employed in industry to purify the propylene stream. Intensive efforts have been devoted in the past decades to regulate the structures of Pd-based catalysts toward enhanced hydrogenation activity and selectivity, such as alloying with another metal and adding metal oxides as a type of promoter. – Given the high cost and scarcity of Pd-based catalysts, developing cost-effective catalysts such as metal oxide catalyst has been emerging as a new approach to address such issue. , For instance, ceria (CeO 2 ) has been shown to be active for several hydrogenation processes, including selective hydrogenation of alkynes – and the reduction of CO 2 to various valuable chemicals, – owing to its unique reversible Ce 3+ /Ce 4+ redox pairs, , tunable oxygen vacancies, , and surface acid–base properties. , Despite great efforts to design and optimize metal oxide catalysts for hydrogenation, the activities remain unfavorable and hence necessitate more precise tailoring for the structures of oxide catalysts, especially at the atomic level.…”