We investigate the pH-dependent surface chemistry of three relevant and widely used oxides, MgO, TiO2, and γ-Al2O3, from ab initio molecular dynamics simulations at the level of density functional theory (DFT). We studied the MgO (001), anatase TiO2 (101), and γ-Al2O3 (001) low-index surfaces and considered solvation effects by explicitly simulating the solid/water interfaces. The analysis of the MgO/H2O, TiO2/H2O, γ-Al2O3/H2O interfaces allowed us to access atomistic details of the structure and the effects induced by water on these surfaces. We also investigated the pH dependence by means of the Grand Canonical formulation of species in solution. This allowed us to evaluate acid–base equilibrium constants and the point-of-zero charge (pHPZC) values. The calculated pHPZC values compare well with available experimental measurements. Based on the above result, we also predicted the fraction of charged species (H+ and OH–) and neutral molecules (H2O) present on the surface as a function of pH, a fundamental aspect if one wants to identify suitable catalysts for water splitting reactions.

Oxidation catalysis on reducible oxide-supported small metal clusters often involves lattice oxygen. In the present work, we trace the path of lattice oxygen from Fe3O4(001) onto small Pt clusters during the CO oxidation, aiming at differentiating whether the reaction takes place at the cluster/support interface or on the cluster. While oxygen vacancies form on many other supports, magnetite maintains its surface stoichiometry upon reduction thanks to a high cation mobility. In order to investigate whether size-dependent oxygen affinities play a role, we study two specific cluster sizes, Pt5 and Pt19. By separating different reaction steps in our experiment, lattice oxygen can be accumulated on the clusters. Temperature programmed desorption (TPD) and sophisticated pulsed valve experiments indicate that the CO oxidation takes place on the Pt clusters rather than at the interface. Scanning tunneling microscopy (STM) shows a decrease in apparent height of the clusters, which density functional theory (DFT) explains as a restructuring following lattice oxygen reverse spillover.

1-Methylimidazolium trinitromethanide {[HMIM]C(NO2)3} as a nano structure ionic liquid was applied for the synthesis of pyrazole derivatives with high yields under mild and green conditions.

A dioxomolybdenum complex supported on functionalized Fe3O4 magnetite nanoparticles as a heterogeneous catalyst was synthesized, characterized and used in the synthesis pyrazole derivatives.

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Sometimes, dopants in oxide surfaces are referred to as single-atom catalysts, at least when these species are incorporated in the supporting lattice. Usually, single atom catalysts are transition metal atoms stabilized on an oxide surface, and the activity is due to the valence electrons of these species. However, the surface chemistry can be modified also by the presence of isovalent heteroatoms, where the total number of valence electrons of the active site is the same as for the regular surface. The effect of isovalent dopants on the chemical reactivity of tetragonal ZrO 2 has been studied with first principles calculations. Zr ions in the bulk, subsurface, and surface sites have been replaced with Si, Ge, Sn, Pb, Ti, Hf, and Ce ions. Surface or subsurface sites are clearly preferred. The dopants modify the local structure of the surface and introduce new empty states in the band gap, thus affecting the Lewis acid properties of the surface. We studied the effect of the dopants on the decomposition of HCOOH. This can follow four paths with desorption of (a) H 2, (b) CO, (c) H 2 O, or (d) CO 2 . On pure ZrO 2 reaction (a) dehydrogenation is preferred followed by decarbonylation (b). Ti, Hf, and Ce have some effect on the decomposition but do not change the order of reactivity. On the contrary, in the presence of Si, decarbonylation becomes the preferred path. If Ge occupies surface sites, reaction (d) loss of CO 2 is by far more favorable. With Sn, dehydrogenation remains energetically preferred but the ordering of the other reactions changes, while Pb makes CO 2 desorption slightly preferred over release of H 2 . These effects virtually disappear when the dopants occupy subsurface sites. The study shows that "steric" and/or "orbital" effects of isovalent dopants on a catalyst surface are sufficient to change the reaction products compared to the undoped system.

The synthesis of 2-amino-4-aryl-6-(arylamino)pyridine-3,5-dicarbonitriles was carried out using [TEATNM] and [TEATCM] as catalysts via anomeric-based oxidation.

In this work, a new equation consist of A⋅⋅⋅B, B⋅⋅⋅C, A⋅⋅⋅BC, and AB⋅⋅⋅C interactions is proposed for calculating the total interaction energy of noncyclic ABC triads. New equations are also proposed for calculating the changes in values of A⋅⋅⋅B and B⋅⋅⋅C interactions on the formation of triad from the corresponding dyads. The advantages of equations proposed here in comparison with many-body interaction energy approach are discussed. All proposed equations were tested in F MLi⋅⋅⋅NCH⋅⋅⋅HLH and F MLi⋅⋅⋅HLH⋅⋅⋅HCN (M = C, Si; L = Be, Mg) as well as H N⋅⋅⋅XY⋅⋅⋅HF (X, Y = F, Cl, Br) noncyclic A⋅⋅⋅B⋅⋅⋅C triads. The data show that the total cooperativity of triad correlates well with the sum of the changes in values of A⋅⋅⋅B and B⋅⋅⋅C interactions calculated through new equations proposed here. © 2016 Wiley Periodicals, Inc.