Being negative can be positive: metal oxide anions promise more selective methane to methanol conversion

Abstract

COMPUTAtIONAL STUDIES are performed to show that metal oxide anionic complexes promote the CH4+N2O→CH3OH+N2 reaction with low activation barriers for the C-H activation and the formation of the CH3-OH bond....

Transition metal oxide complexes as molecular catalysts for selective methane to methanol transformation: any prospects or time to retire?

“…Only the structures for [M] = Pd À are shown, 104 but the activation barriers for all three species are listed (blue/green values correspond to 2+2/PCET mechanisms). 49,104 The bottom left values correspond to the energy required for the release of methanol. (b) Structures and interaction energies for the Pd(CH 3 OH) 2+,+,0,À species calculated presently at the MN15 level of theory (see text).…”

“…For example, the two types of mechanisms (PCET, 2+2) are found for anions too. Another interesting observation is that the last oxygen reload step has a near-zero activation barrier for an anion, 49,104 when using N 2 O, generally smaller (certainly not bigger) than neutral and cationic metal oxide units. 18,34,[108][109][110][111] For practical applications, it has to be seen if this holds true for O 2 .…”

“…Recent calculations found that ligands coordinating with a metal–carbon bond, such as methyl 106 or biphenyl, increase the electron capacity of the metal center. 49 Specifically, the electron affinity of the M(CH 3 ) 4 species, M = Ni, Pd, Pt, soars to 2.3–2.7 eV and is nearly insensitive to the metal identity (the range for the atoms is 0.6–2.1 eV; see Fig. 10), which makes Ni an excellent candidate for practical applications as the more naturally abundant metal.…”

“…In response, the use of molecular metal oxide anionic species has been proposed based on quantum mechanical calculations. 48,49 In this case, methanol interacts with a negatively charged metal center with which it binds only weakly. More details for this ''molecular electrocatalysis'' process are presented later.…”

Computational Discovery of Stable Metal-Organic Frameworks for Methane-to-Methanol Catalysis

“…[14][15][16] These metalloenzymes have inspired the design of synthetic homogeneous and heterogeneous catalysts for the direct conversion of methane to methanol via more energy-efficient methods. [17][18][19][20][21][22][23][24][25] Nevertheless, no synthetic catalyst to date is capable of simultaneously achieving high conversions and selectivities as enzymes have, motivating a wider search of candidate catalysts.…”