Readily available ascorbic acid was discovered as an environmentally benign hydrogen bond donor (HBD) for the synthesis of cyclic organic carbonates from CO2 and epoxides in the presence of nucleophilic co-catalysts. The ascorbic acid/TBAI (TBAI: tetrabutylammonium iodide) binary system could be applied for the cycloaddition of CO2 to various epoxides under ambient or mild conditions. DFT calculations and catalysis experiments revealed an intriguing bifunctional mechanism in the step of CO2 insertion involving different hydroxyl moieties (enediol, ethyldiol) of the ascorbic acid scaffold.

Combining propane dehydrogenation with propylene metathesis in a single step yields mixtures of propylene, ethylene and butenes, important building blocks for the chemical industry. The open challenges and opportunities in the field are highlighted.

Conversion of greenhouse gases to more valuable chemicals is important from both the environmental and industrial points of view. Herein, the reaction mechanisms of the hydrogenation of carbon dioxide (CO2) to formic acid (HCOOH) over Cu-alkoxide-functionalized metal organic framework (MOF) have been investigated by means of calculations with the M06-L density functional. The reaction can proceed via two different pathways, namely, concerted and stepwise mechanisms. In the concerted mechanism, the hydrogenation of CO2 to formic acid occurs in a single step. It requires a high activation energy of 67.2 kcal/mol. For the stepwise mechanism, the reaction begins with the hydrogen atom abstraction by CO2 to form a formate intermediate. The intermediate then takes another hydrogen atom to form formic acid. The activation energies are calculated to be 24.2 and 18.3 kcal/mol for the first and second steps, respectively. Because of the smaller activation barriers associated with this pathway, it therefore seems to be more favored than the concerted one. The catalytic effect of Cu-MOF-5 is also highlighted by comparing it with the gas-phase uncatalyzed reaction in which the reaction takes place in one step with a barrier of 73.0 kcal/mol. This study also demonstrates that the metal-functionalized MOF can be utilized for the greenhouse gas catalysis in addition to using it to capture and activate CO2.

Catalytic conversion of hazardous gases can solve many of the environmental problems caused by them. We performed a density functional theory (DFT) study with the Perdew−Burke−Ernzerhof (PBE) functional to investigate the CO oxidation by using N 2 O as an oxidizing agent over an iron-embedded graphene (Fe-Graphene) catalyst. The N 2 O molecule was first decomposed on the Fe site yielding the N 2 molecule and an Fe−O intermediate, which was an active species for the CO oxidation. The activation energy for the N 2 O decomposition step was predicted to be 8 kcal/mol. According to the population analysis, the graphene acted as both the electron withdrawing and donating support to assist the charge transfer between the Fe atom and the probe molecules, which are important for the reaction. The reaction was found to be less facile when the Fe site was first covered by the CO which has a higher adsorption energy than that of the N 2 O (−10.0 vs −33.6 kcal/mol). The reaction proceeded via a concerted transition structure and required an activation energy of 19.2 kcal/mol when the CO was prior adsorbed. Thus, control of the adsorbing molecules over Fe-Graphene might be a key factor for the activity of the catalyst. With the higher catalytic activities of Fe-embedded graphene compared to other typical catalysts, this may open new avenues in searching for oxidation of CO at an economical cost.

The development of hydrogen bond donors (HBDs) as catalytic moieties in the cycloaddition of carbon dioxide to epoxides is an active field of research to access efficient, inexpensive and sustainable metalfree systems for the conversion of carbon dioxide to useful chemicals. Thus far, no systematic attempt to correlate the activity of a diverse selection of HBDs to their physico-chemical properties has been undertaken. In this work, we investigate factors influencing the catalytic activity of hydroxyl HBDs from different chemical families under ambient conditions by considering the HBDs Brønsted acidity (expressed as pK a ), the number of hydroxyls and structural aspects. As an effect, this study highlights the crucial role of the hydroxyl protons' Brønsted acidity in determining the catalytic activity of the HBDs, identifies an ideal range for the hydroxyl HBDs proton acidity (9

The oxidation of CO by NO over metal-organic framework (MOF) M(btc) (M = Fe, Cr, Co, Ni, Cu, and Zn) catalysts that contain coordinatively unsaturated sites has been investigated by means of density functional theory calculations. The reaction proceeds in two steps. First, the N-O bond of NO is broken to form a metal oxo intermediate. Second, a CO molecule reacts with the oxygen atom of the metal oxo site, forming one C-O bond of CO. The first step is a rate-determining step for both Cu(btc) and Fe(btc), where it requires the highest activation energy (67.3 and 19.6 kcal/mol, respectively). The lower value for the iron compound compared to the copper one can be explained by the larger amount of electron density transferred from the catalytic site to the antibonding of NO molecules. This, in turn, is due to the smaller gap between the highest occupied molecular orbital (HOMO) of the MOF and the lowest unoccupied molecular orbital (LUMO)  of NO for Fe(btc) compared to Cu(btc). The results indicate the important role of charge transfer for the N-O bond breaking in NO. We computationally screened other MOF M(btc) (M = Cr, Fe, Co, Ni, Cu, and Zn) compounds in this respect and show some relationships between the activation energy and orbital properties like HOMO energies and the spin densities of the metals at the active sites of the MOFs.

Activation of methane has attracted a great deal of interest in laboratory chemical synthesis and in large-scale industrial processes. We performed density functional theory studies to investigate the C–H bond breaking of methane on Au+ and Au2 + ions in vacuum and inside different types of zeolites. The density functional M06-L and the 6-31G(d,p) basis set were employed as this level of theory had already been shown to be reasonably accurate and affordable for transition metal systems. We investigated four industrially important catalysts, ZSM-5, FAU, FER, and MCM-22, each with a particular framework topology, with respect to their performance for methane activation. The bicoordinated character of the cationic site in the ZSM-5 structure provides a higher activity than the FAU structure with a 3-fold coordination of its cationic site. The activation energy of the reaction catalyzed by Au-ZSM-5 is lower than the one with the bare Au+ cation (13.2 vs 21.3 kcal/mol) because of the structural constraint imposed by the zeolite that leads to an earlier transition state with a high charge difference of the C–H atoms where the bond is broken. It is also found that the activity of Au n + decreases already with n = 2, due to the shared positive charge. For the zeolites with large pores, Au-MCM-22 provides a higher activity due to the spacious framework of this particular type of zeolite is perfect for stabilizing the transition state structure but not the corresponding adsorption complex. The small and medium pore-sized zeolites, Au-FER and Au-ZSM-5 stabilize both the adsorption complex and the transition states, thus causing the activation energy to remain the same.

The design of catalysts for CO2 reduction is challenging because of the fundamental relationships between the binding energies of the reaction intermediates. Metal carbides have shown promise for transcending these relationships and enabling low-cost alternatives. Herein, we show that directional bonding arising from the mixed covalent/metallic character plays a critical role in governing the surface chemistry. This behavior can be described by consideration of individual d-band components. We use this model to predict efficient catalysts based on tungsten carbide with a sub-monolayer of iron adatoms. Our approach can be used to predict site-preference and binding-energy trends for complex catalyst surfaces.