Reaction mechanism of methanol to formaldehyde over Fe- and FeO-modified graphene.

We employed periodic DFT calculations (PBE-D2) to investigate the catalytic conversion of methanol over graphene embedded with Fe and FeO. Two possible pathways of dehydrogenation to formaldehyde and dehydration to dimethyl ether (DME) over these catalysts were examined. Both processes are initiated with the activation of methanol over the catalytic center through O-H cleavage.

Theoretical studies on electronic structures and photophysical properties of anthracene derivatives as hole-transporting materials for OLEDs.

The electronic structures and photophysical properties of anthracene derivatives as hole-transporting materials (HTM) in OLEDs have been studied by DFT and TD-DFT methods. Thiophene and triphenylamine (TPA) moieties are used as substituents in anthracene based HTMs providing FATn and FAPn compounds (n=1-2), respectively. The calculated electronic levels by B3LYP show proper energy matching of FAPn and hole-injecting layer (HIL), indicating that the hole-transports of the FAPn compounds are better than the FATn compounds.

Comparison of Cu-ZSM-5 zeolites and Cu-MOF-505 metal-organic frameworks as heterogeneous catalysts for the Mukaiyama aldol reaction: a DFT mechanistic study.

The density functional theory (DFT) model ONIOM(M06L/6-311++G(2df,2p):UFF was employed to reveal the catalytic activity of Cu(II) in the paddle-wheel unit of the metal-organic framework (MOF)-505 material in the Mukaiyama aldol reaction compared with the activity of Cu-ZSM-5 zeolites. The aldol reaction between a silyl enol ether and formaldehyde catalyzed by the Lewis acidic site of both materials takes place through a concerted pathway, in which the formation of the CC bond and the transfer of the silyl group occurs in a single step. MOF-505 and Cu-ZSM-5 are predicted to be efficient catalysts for this reaction as they strongly activate the formaldehyde carbonyl carbon electrophile, which leads to a considerably lower reaction barrier compared with the gas-phase system.

Mechanistic studies on the transformation of ethanol into ethene over Fe-ZSM-5 zeolite.

Ethanol, through the utilization of bioethanol as a chemical resource, has received considerable industrial attention as it provides an alternative route to produce more valuable hydrocarbons. Using a density functional theory approach incorporating the M06-L functional, which includes dispersion interactions, a large 34T nanocluster model of Fe-ZSM-5 zeolite in which T is a Si or Al atom is employed to examine both the stepwise and concerted mechanisms of the transformation of ethanol into ethene. For the stepwise mechanism, ethanol dehydration commences from the first hydrogen abstraction of the ethanol OH group to form the ethoxide-hydroxide intermediate with a low activation energy of 17.

Structures, energetics and reaction mechanisms of nitrous oxide on transition-metal-doped and -undoped single-wall carbon nanotubes.

The catalytic activity of carbon nanotubes (CNTs) for the removal of greenhouse gases, like nitrous oxide (N(2)O), can be fine-tuned by metal doping. We modify the inert surfaces of CNTs with Sc, Ti and V transition metals in order to investigate their capability of converting N(2)O to N(2). The stable composite catalysts of Sc-, Ti- and V-doped (5,5)single-walled carbon nanotubes (SWCNTs), along with the unmodified one were investigated by periodic DFT calculations.

Formaldehyde encapsulated in lithium-decorated metal-organic frameworks: a density functional theory study.

The stability of monomeric formaldehyde encapsulated in the lithium-decorated metal-organic framework Li-MOF-5 was investigated by means of density functional calculations with the M06-L functional and the 6-31G(d,p) basis set. To assess the efficiency of Li-MOF-5 for formaldehyde preservation, we consider the reaction kinetics and the thermodynamic equilibrium between formaldehyde and its trimerized product, 1,3,5-trioxane. We propose that trimerization of encapsulated formaldehyde takes place in a single reaction step with an activation energy of 34.

Density functional theory study of the carbonyl-ene reaction of encapsulated formaldehyde in Cu(I), Ag(I), and Au(I) exchanged FAU zeolites.

Carbonyl-ene reactions, which involve C-C bond formation, are essential in many chemical syntheses. The formaldehyde-propene reaction catalyzed by several of the group 11 metal cations, Cu(+), Ag(+), and Au(+) exchanged on the faujasite zeolite (metal-FAU) has been investigated by density functional theory at the M06-L/6-31G(d,p) level. The Au-FAU exhibits a higher activity than the others due to the high charge transfer between the Au and the reactant molecules, even though it is located at a negatively charged site of the zeolite.

Oxidative dehydrogenation of propane over a VO2-exchanged MCM-22 zeolite: a DFT study.

The adsorption and the mechanism of the oxidative dehydrogenation (ODH) of propane over VO(2)-exchanged MCM-22 are investigated by DFT calculations using the M06-L functional, which takes into account dispersion contributions to the energy. The adsorption energies of propane are in good agreement with those from computationally much more demanding MP2 calculations and with experimental results. In contrast, B3LYP binding energies are too small.

Effects of the zeolite framework on the adsorptions and hydrogen-exchange reactions of unsaturated aliphatic, aromatic, and heterocyclic compounds in ZSM-5 zeolite: a combination of perturbation theory (MP2) and a newly developed density functional theory (M06-2X) in ONIOM scheme.

The confinement effect on the adsorption and reaction mechanism of unsaturated aliphatic, aromatic and heterocyclic compounds on H-ZSM-5 zeolite has been investigated by the four ONIOM methods (MP2:M06-2X), (MP2:B3LYP), (MP2:HF), and (MP2:UFF). The H-ZSM-5 'nanoreactor' porous intersection, where chemical reactions take place, is represented by a quantum cluster of 34 tetrahedral units. Ethene, benzene, ethylbenzene, and pyridine are chosen to represent reactions of various adsorbates of aliphatic, aromatic and heterocyclic compounds.

Structures and reaction mechanisms of propene oxide isomerization on H-ZSM-5: an ONIOM study.

The isomerization mechanisms of propene oxide over H-ZSM-5 zeolite have been investigated via the utilization of 5T and 46T cluster models calculated by the B3LYP/6-31G(d,p) and the ONIOM(B3LYP/6-31G(d,p):UFF) methods, respectively. The reactions are considered to proceed through a stepwise mechanism: (1) the epoxide ring protonation, and concurrently the ring-opening, and (2) the 1,2-hydride shift forming the adsorbed carbonyl compound. Because of the asymmetric structure of propene oxide, two different C-O bonds (more or less substituted carbon atom sides) can be broken leading to two different types of products, propanal and propanone.

Decomposition of nitrous oxide on carbon nanotubes.

In this work, we have suggested the possibility of using carbon nanotubes to remove toxic gas. By taking an advantage of the density functional theory, we have investigated the decomposition of nitrous oxide (N(2)O) on the sidewalls of the perfect and the Stone-Wales defect armchair (5,5)-SWNTs at the B3LYP/6-31G(d) level of theory. There are two reaction mechanisms proposed: stepwise and concerted pathways.