Rhodium atoms for alkane dehydrogenation Nanoparticles of rhodium dispersed on metal oxides are generally poor catalysts because the reactants bind too strongly to metal. Hannagan et al. performed first-principle calculations indicating that single in a copper surface should be stable and selective conversion propane propene hydrogen. Model studies embedded (111) revealed very high selectivity resistance formation carbon would deactivate catalyst. Science , abg8389, this issue p. 1444

C–H bond activation at lattice O atoms on oxides mediates some of the most important chemical transformations small organic molecules. The relations between molecular and catalyst properties energies are discerned in this study for diverse bonds prevalent C1–C4 hydrocarbons oxygenates using with a broad range H atom abstraction properties. These determine, turn, attainable selectivities yields desired oxidation products, which differ from reactants their strength. Brønsted-Evans–Polanyi...

Density functional theory (DFT) calculations of energetic, geometric, vibrational, and electrostatic properties different arrangements CO NO at quarter half monolayer coverage on Pt(111) are presented. Differences in the extents electron back-donation from Pt surface to these molecules cause low-coverage adsorbate dipoles have opposite signs atop more highly coordinated bridge or fcc sites. These sign occupy adjacent positions experimentally observed atop-bridge atop-fcc high -coverage...

M1 phase MoVTeNb mixed oxides exhibit unique catalytic properties that lead to high C2H4 yields in oxidative conversion of C2H6 at moderate temperatures. The role the heptagonal channel micropores regulating reactivity and selectivity is assessed here using reactant size-dependent kinetic probes density functional theory (DFT) treatments for cyclohexane (C6H12) activations inside outside micropores. sizes suggest a tight guest–host fit, but C6H12 cannot access intrapore sites. Measured...

Ethanol dehydrogenation presents a promising pathway toward the production of acetaldehyde, valuable building block in chemicals production. Under nonoxidative conditions, reaction is facilitated by supported Cu nanoparticles, which afford reasonable activity and high selectivity. The stability issues associated with nanoparticle sintering can be addressed addition small amounts Ni, further boost reactivity while retaining Despite promise NiCu single-atom alloys for ethanol dehydrogenation,...

Acid and redox reaction rates of CH3OH-O2 mixtures on polyoxometalate (POM) clusters, together with isotopic, spectroscopic, theoretical assessments catalyst properties pathways, were used to define rigorous descriptors reactivity probe the compositional effects for oxidative dehydrogenation (ODH) dehydration reactions. 31P-MAS NMR, transmission electron microscopy titrations protons di-tert-butylpyridine during catalysis showed that POM clusters retained their Keggin structure upon...

Density functional theory and classical electrostatics are used to develop reactivity descriptors for catalysis by solid acids. Acid strength, as deprotonation energies (DPE), reflects the charge reorganization required disrupt covalent OH bonds in inorganic acids electrostatic forces that resist separation of protons from conjugate anions. Both (covalent) (ionic) components vary monotonically with DPE on different heteroatoms within a given type oxide framework, but their relative...

Brønsted acids mediate chemical transformations via proton transfer to bound species and interactions between the conjugate anion cationic intermediates transition states that are also stabilized by van der Waals forces within voids of molecular dimensions in inorganic hosts. This Feature Article describes relevant descriptors reactivity terms properties molecules determine their ability donate accept protons reorganize respective charges optimize at states. The deprotonation energy (DPE)...

Periodic DFT calculations are used to study the effect of a homogeneous electric field applied perpendicular Pt(111) surface on bond distances, binding energies, and vibrational frequencies atop- fcc-adsorbed CO at various coverages. The observed structural energetic modifications can be understood in terms modest field-induced charge transfer between charged metal adsorbate well-described by classical first second-order Stark models. Electronic differences atop fcc adsorption cause these...

Reactivity descriptors describe catalyst properties that determine the stability of kinetically relevant transition states and adsorbed intermediates. Theoretical descriptors, such as deprotonation energies (DPE), rigorously account for Brønsted acid strength catalytic solids with known structure. Here, mechanistic interpretations methanol dehydration turnover rates are used to assess how charge reorganization (covalency) electrostatic interactions DPE recovered when intermediates interact...

The oxidative dehydrogenation (ODH) of alkanols on oxide catalysts is generally described as involving H-abstraction from alkoxy species formed via O–H dissociation. Kinetic and isotopic data cannot discern between such routes those kinetically-relevant undissociated alkanols. Here, we combine experiments with theoretical estimates activation energies entropies to show that the latter molecular prevail over dissociative for methanol reactions polyoxometalate (POM) clusters at all practical...

M1-phase MoVTeNb mixed oxides contain V-oxo species isolated by dispersion in the Mo-oxo framework and one-dimensional heptagonal micropores that tightly enclose C2H6 molecules. These catalyze oxidation with C2H4 selectivity much higher than V2O5 containing continuous domains without micropores. Here, effects of structures VOx on are discerned using (i) measured rate constant ratios activation barrier differences relevant to two (ii) density functional theory (DFT) analysis steps mediating...

Mechanistic details and product distributions for C3H8–O2 reactions catalyzed by gas-phase NOx species are compared to on solid V2O5 catalysts. C3H8 conversions greatly enhanced addition of small concentrations NO mixtures without catalysts because homogeneous catalytic redox cycles involving oxidation NO2, reduction H-addition form HONO release OH radicals facilitate abstraction H-atoms from strong C–H bonds in C3H8. NOx-mediated exhibit C3H6 selectivity values among the highest reported at...

The identification of thermodynamic descriptors catalytic performance is essential for the rational design heterogeneous catalysts. Here, we investigate how spillover energy, a descriptor quantifying whether intermediates are more stable at dopant or host metal sites, can be used to single-atom alloys (SAAs) formic acid dehydrogenation. Using theoretical calculations, identify NiCu as SAA with favorable energy and demonstrate that formate produced after initial O–H activation Ni sites where...

Enrique Iglesia is an internationally recognized leader in the field of heterogeneous catalysis. His trademark approach places a premium on kinetic and mechanistic descriptions catalytic sequences, complemented by synthetic methods to prepare centers uniform composition computational chemistry adjudicate among competing hypotheses, with aim describing function active sites at level elementary steps reaction mechanisms. began his independent career industry, spending 11 years Exxon Corporate...

We study CO adsorption on a multilayer catalytic diode in which electron transfer at the metal–semiconductor (Pt/TiO2) junction is controlled by an applied external voltage. The structure enhances infrared absorption signals from molecules adsorbed small area Pt surface. find that behaves like Schottky and changes are directly correlated with reversible shifts vibrational frequency of CO. Infrared polarization incidence angle dependent studies show magnitude shift varies orientation being...

This study reports the discovery of CoMoOx moieties with synergistic catalytic roles in C2H6–CO2 catalysis. catalysis occurs through multiple, concomitant cycles, initiated by dual cycles C2H6 activation and CO2 activation, together an undesired coke deposition cycle. requires reactive oxygen species that assist kinetically relevant C–H bond activation; these are generated from cycle within reverse water-gas shift (RWGS) reaction. An efficient RWGS reaction would retain higher O contents...

Herein, the "push effect" strategy combined with "triple-phase-boundary" (TPB) engineering was innovatively employed to target single Fe-N4 sites in an iron porphyrin-based metal-organic framework, axially coordinated 4-octylpyridine groups on (named as PCN-224 (Fe)-1). The amphiphilic donate sufficient electrons toward by Fe-N(pyridine) coordination bond and simultaneously provide effective TBP reactive hydrophobic octyl terminals, resulting enhanced ORR activity of (Fe)-1 E1/2 0.81 V...

We demonstrate that single-atom alloy catalysts can be made by exposing physical mixtures of monometallic supported Cu and Pd to vinyl acetate (VA) synthesis reaction conditions. This induces the formation mobile clusters metal diacetate species drive extensive nanoparticle restructuring, leading atomic dispersion precious metal, smaller sizes than parent catalysts, high activity selectivity for both VA ethanol dehydrogenation reactions. approach is scalable appears generalizable other catalysts.

Alkane dehydrogenation is an enabling route to make alkenes useful as chemical intermediates. This study demonstrates the high reactivity of Lewis acid-base (LAB) site pairs at ZrO