The Enigma of Methanol Synthesis by Cu/ZnO/Al2O3-Based Catalysts.

The activity and durability of the Cu/ZnO/Al2O3 (CZA) catalyst formulation for methanol synthesis from CO/CO2/H2 feeds far exceed the sum of its individual components. As such, this ternary catalytic system is a prime example of synergy in catalysis, one that has been employed for the large scale commercial production of methanol since its inception in the mid 1960s with precious little alteration to its original formulation. Methanol is a key building block of the chemical industry. It is also an attractive energy storage molecule, which can also be produced from CO2 and H2 alone, making efficient use of sequestered CO2. As such, this somewhat unusual catalyst formulation has an enormous role to play in the modern chemical industry and the world of global economics, to which the correspondingly voluminous and ongoing research, which began in the 1920s, attests. Yet, despite this commercial success, and while research aimed at understanding how this formulation functions has continued throughout the decades, a comprehensive and universally agreed upon understanding of how this material achieves what it does has yet to be realized. After nigh on a century of research into CZA catalysts, the purpose of this Review is to appraise what has been achieved to date, and to show how, and how far, the field has evolved. To do so, this Review evaluates the research regarding this catalyst formulation in a chronological order and critically assesses the validity and novelty of various hypotheses and claims that have been made over the years. Ultimately, the Review attempts to derive a holistic summary of what the current body of literature tells us about the fundamental sources of the synergies at work within the CZA catalyst and, from this, suggest ways in which the field may yet be further advanced.

Hybrid oxide coatings generate stable Cu catalysts for CO2 electroreduction.

Hybrid organic/inorganic materials have contributed to solve important challenges in different areas of science. One of the biggest challenges for a more sustainable society is to have active and stable catalysts that enable the transition from fossil fuel to renewable feedstocks, reduce energy consumption and minimize the environmental footprint. Here we synthesize novel hybrid materials where an amorphous oxide coating with embedded organic ligands surrounds metallic nanocrystals. We demonstrate that the hybrid coating is a powerful means to create electrocatalysts stable against structural reconstruction during the CO2 electroreduction. These electrocatalysts consist of copper nanocrystals encapsulated in a hybrid organic/inorganic alumina shell. This shell locks a fraction of the copper surface into a reduction-resistant Cu2+ state, which inhibits those redox processes responsible for the structural reconstruction of copper. The electrocatalyst activity is preserved, which would not be possible with a conventional dense alumina coating. Varying the shell thickness and the coating morphology yields fundamental insights into the stabilization mechanism and emphasizes the importance of the Lewis acidity of the shell in relation to the retention of catalyst structure. The synthetic tunability of the chemistry developed herein opens new avenues for the design of stable electrocatalysts and beyond.

Colloidal Atomic Layer Deposition on Nanocrystals Using Ligand-Modified Precursors.

Atomic layer deposition (ALD) is a method to grow thin metal oxide layers on a variety of materials for applications spanning from electronics to catalysis. Extending ALD to colloidally stable nanocrystals promises to combine the benefits of thin metal oxide coatings with the solution processability of the nanocrystals. However, challenges persist in applying this method, which relate to finding precursors that promote the growth of the metal oxide while preserving colloidal stability throughout the process. Herein, we introduce a colloidal ALD method to coat nanocrystals with amorphous metal oxide shells using metal and oxygen precursors that act as colloidal stabilizing ligands. Our scheme involves metal-amide precursors modified with solubilizing groups and oleic acid as the oxygen source. The growth of the oxide is self-limiting and proceeds in a layer-by-layer fashion. Our protocol is generalizable and intrinsically scalable. Potential applications in display, light detection, and catalysis are envisioned.

Capnography access and use in Kenya and Ethiopia.

PURPOSE: Lack of access to safe and affordable anesthesia and monitoring equipment may contribute to higher rates of morbidity and mortality in low- and middle-income countries (LMICs). While capnography is standard in high-income countries, use in LMICs is not well studied. We evaluated the association of capnography use with patient and procedure-related characteristics, as well as the association of capnography use and mortality in a cohort of patients from Kenya and Ethiopia. METHODS: For this retrospective observational study, we used historical cohort data from Kenya and Ethiopia from 2014 to 2020. Logistic regression was used to study the association of capnography use (primary outcome) with patient/procedure factors, and the adjusted association of intraoperative, 24-hr, and seven-day mortality (secondary outcomes) with capnography use. RESULTS: A total of 61,792 anesthetic cases were included in this study. Tertiary or secondary hospital type (compared with primary) was strongly associated with use of capnography (odds ratio [OR], 6.27; 95% confidence interval [CI], 5.67 to 6.93 and OR, 6.88; 95% CI, 6.40 to 7.40, respectively), as was general (vs regional) anesthesia (OR, 4.83; 95% CI, 4.41 to 5.28). Capnography use was significantly associated with lower odds of intraoperative mortality in patients who underwent general anesthesia (OR, 0.31; 95% CI, 0.17 to 0.48). Nevertheless, fully-adjusted models for 24-hr and seven-day mortality showed no evidence of association with capnography. CONCLUSION: Capnography use in LMICs is substantially lower compared with other standard anesthesia monitors. Capnography was used at higher rates in tertiary centres and with patients undergoing general anesthesia. While this study revealed decreased odds of intraoperative mortality with capnography use, further studies need to confirm these findings.

RéSUMé: OBJECTIF: Le manque d'accès à des équipements d'anesthésie et de monitorage sécuritaires et abordables peut contribuer à des taux plus élevés de morbidité et de mortalité dans les pays à revenu faible et intermédiaire (PRFI). Alors que la capnographie est une modalité standard dans les pays à revenu élevé, son utilisation dans les PRFI n'est pas bien étudiée. Nous avons évalué l'association de l'utilisation de la capnographie avec les caractéristiques des patient·es et des interventions, ainsi que l'association de l'utilisation de la capnographie et de la mortalité dans une cohorte de patient·es du Kenya et d'Éthiopie. MéTHODE: Pour cette étude observationnelle rétrospective, nous avons utilisé des données de cohortes historiques du Kenya et de l'Éthiopie de 2014 à 2020. Une régression logistique a été utilisée pour étudier l'association entre l'utilisation de la capnographie (critère d'évaluation principal) et les facteurs patient·es/interventions, ainsi que pour étudier l'association ajustée entre la mortalité peropératoire, à 24 h et à sept jours (critères d'évaluation secondaires) et l'utilisation de la capnographie. RéSULTATS: Au total, 61 792 cas d'anesthésie ont été inclus dans cette étude. Le type d'hôpital tertiaire ou secondaire (par rapport à un établissement primaire) était fortement associé à l'utilisation de la capnographie (rapport de cotes [RC], 6,27; intervalle de confiance [IC] à 95 %, 5,67 à 6,93 et RC, 6,88; IC 95 %, 6,40 à 7,40, respectivement), tout comme l'était l'anesthésie générale (vs régionale) (RC, 4,83; IC 95 %, 4,41 à 5,28). L'utilisation de la capnographie était significativement associée à une probabilité plus faible de mortalité peropératoire chez les patient·es ayant reçu une anesthésie générale (RC, 0,31; IC 95 %, 0,17 à 0,48). Néanmoins, les modèles entièrement ajustés pour la mortalité à 24 heures et à sept jours n'ont montré aucune donnée probante d'association avec la capnographie. CONCLUSION: L'utilisation de la capnographie dans les PRFI est considérablement moins répandue que celle d'autres moniteurs d'anesthésie standard. La capnographie a été utilisée à des taux plus élevés dans les centres tertiaires et chez des patient·es sous anesthésie générale. Bien que cette étude ait révélé une diminution de la probabilité de mortalité peropératoire avec l'utilisation de la capnographie, d'autres études doivent confirmer ces résultats.

The role of collaboration in educating the global pediatric anesthesia workforce.

An estimated 1.7 billion children and adolescents do not have access to safe and affordable surgical care, and the vast majority of these are located in low-middle-income countries (LMICs). Pediatric anesthesia, a specialized field that requires a diverse set of knowledge and skills, has seen various advancements over the years and has become well-established in upper-middle and high-income countries. However, in LMICs, due to a multitude of factors including severe workforce shortages, this has not been the case. Collaborations play a vital role in increasing the capacity of pediatric anesthesiology educators and training the pediatric anesthesia workforce. These efforts directly increase access for children who require surgical intervention. Collaboration models can be operationalized through bidirectional knowledge sharing, training, resource allocation, research and innovation, quality improvement, networking, and advocacy. This article aims to highlight a few of these collaborative efforts. Specifically, the role that the World Federation of Societies of Anaesthesiologists, the Safer Anesthesia from Education program, the Asian Society of Pediatric Anaesthesiologists, Pediatric Anesthesia Training in Africa, the Paediatric Anaesthesia Network New Zealand, the Safe Pediatric Anesthesia Network and two WhatsApp™ groups (global ped anesthesia and the Pediatric Difficult Intubation Collaborative) have played in improving anesthesiology care for children.

Quantifying the Hydration-Dependent Dynamics of Copper Migration and Activity in Zeolite Omega for the Partial Oxidation of Methane.

Copper-exchanged zeolite omega (Cu-omega) is a potent material for the selective conversion of methane-to-methanol (MtM) via the oxygen looping approach. However, its performance exhibits substantial variation depending on the operational conditions. Under an isothermal temperature regime, Cu-omega demonstrates subdued activity below 230 °C, but experiences a remarkable increase in activity at 290 °C. Applying a high-temperature activation protocol at 450 °C causes a rapid deactivation of the material. This behavioral divergence is investigated by combining reactivity studies, neutron and in situ high-resolution anomalous X-ray powder diffraction (HR-AXRPD), as well as electron paramagnetic resonance spectroscopy, to reveal that the migration of Cu throughout the framework is the primary cause of these behaviors, which in turn is governed by the degree of hydration of the system. This work suggests that control over the Cu migration throughout the zeolite framework may be harnessed to significantly increase the activity of Cu-omega by generating more active sites for the MtM conversion. These results underscore the power of in situ HR-AXRPD for unraveling the behavior of materials under reaction conditions and suggest that a re-evaluation of Cu-zeolites priorly deemed inactive for the MtM conversion across a broader range of conditions and looping protocols may be warranted.

Alloying as a Strategy to Boost the Stability of Copper Nanocatalysts during the Electrochemical CO2 Reduction Reaction.

Copper nanocatalysts are among the most promising candidates to drive the electrochemical CO2 reduction reaction (CO2RR). However, the stability of such catalysts during operation is sub-optimal, and improving this aspect of catalyst behavior remains a challenge. Here, we synthesize well-defined and tunable CuGa nanoparticles (NPs) and demonstrate that alloying Cu with Ga considerably improves the stability of the nanocatalysts. In particular, we discover that CuGa NPs containing 17 at. % Ga preserve most of their CO2RR activity for at least 20 h while Cu NPs of the same size reconstruct and lose their CO2RR activity within 2 h. Various characterization techniques, including X-ray photoelectron spectroscopy and operando X-ray absorption spectroscopy, suggest that the addition of Ga suppresses Cu oxidation at open-circuit potential (ocp) and induces significant electronic interactions between Ga and Cu. Thus, we explain the observed stabilization of the Cu by Ga as a result of the higher oxophilicity and lower electronegativity of Ga, which reduce the propensity of Cu to oxidize at ocp and enhance the bond strength in the alloyed nanocatalysts. In addition to addressing one of the major challenges in CO2RR, this study proposes a strategy to generate NPs that are stable under a reducing reaction environment.

Delivery of Safe Pediatric Anesthesia Care in the First 8000 days: Realities, Challenges, and Solutions in Low- and Middle-Income Countries.

BACKGROUND: Worldwide, perioperative mortality has declined over the past 50 years, but the reduction is skewed toward high-income countries (HICs). Currently, pediatric perioperative mortality is much higher in low- and middle-income countries (LMICs) compared to HICs, despite studied cohorts being predominantly low-risk. These disparities must be studied and addressed. METHODS: A narrative review of the literature was undertaken to identify contributing factors and potential knowledge gaps. Interventions aimed at alleviating the outcomes disparities are discussed, and recommendations are made for future directions. RESULTS AND CONCLUSIONS: There is a lack of adequately trained pediatric anesthesia providers in LMICs, and the number must be bolstered by making such training available. Essential anesthesia medications and equipment, in pediatric-appropriate sizes, are often not available; neither are essential infrastructure items. Perioperative staff are underprepared for emergent situations that may arise and simulation training may help to ameliorate this. The global anesthesia community has implemented several solutions to address these issues. The World Federation of Societies of Anaesthesiologists (WFSA) and Global Initiative for Children's Surgery have published standards that outline essential items for the provision of safe perioperative pediatric care. Several short educational courses have been developed and introduced in LMICs that either specifically address pediatric patients, or contain a pediatric component. The WFSA also maintains a collection of discrete tutorials for educational purposes. Finally, in Africa, large-scale, prospective data collection is underway to examine pediatric perioperative outcomes. More work needs to be done, though, to improve perioperative outcomes for pediatric patients in LMICs.

Assessing the Productivity of the Direct Conversion of Methane-to-Methanol over Copper-Exchanged Zeolite Omega (MAZ) via Oxygen Looping.

The methane-to-methanol (MtM) conversion via the oxygen looping approach using copper-exchanged zeolites has been extensively studied over the last decade. While a lot of research has focussed on maximizing yield and selectivity, little has been directed toward productivity-a metric far more meaningful for evaluating industrial potential. Using copper-exchanged zeolite omega (Cu-omega), a material highly active and selective for the MtM conversion using the isothermal oxygen looping approach, we show that this material exhibits unprecedented potential for industrial valorization. In doing so, we also present a novel methodology combining operando XAS and mass spectrometry for the screening of materials for the MtM conversion in oxygen looping mode.

Nitrogen in Diamond.

Nitrogen is ubiquitous in both natural and laboratory-grown diamond, but the number and nature of the nitrogen-containing defects can have a profound effect on the diamond material and its properties. An ever-growing fraction of the supply of diamond appearing on the world market is now lab-grown. Here, we survey recent progress in two complementary diamond synthesis methods-high pressure high temperature (HPHT) growth and chemical vapor deposition (CVD), how each is allowing ever more precise control of nitrogen incorporation in the resulting diamond, and how the diamond produced by either method can be further processed (e.g., by implantation or annealing) to achieve a particular outcome or property. The burgeoning availability of diamond samples grown under well-defined conditions has also enabled huge advances in the characterization and understanding of nitrogen-containing defects in diamond-alone and in association with vacancies, hydrogen, and transition metal atoms. Among these, the negatively charged nitrogen-vacancy (NV-) defect in diamond is attracting particular current interest in account of the many new and exciting opportunities it offers for, for example, quantum technologies, nanoscale magnetometry, and biosensing.

Changes in Surgical Volume and Outcomes During the Coronavirus Disease 2019 Pandemic at Two Tertiary Hospitals in Ethiopia: A Retrospective Cohort Study.

BACKGROUND: Limited data exist concerning how the coronavirus disease 2019 (COVID-19) pandemic has affected surgical care in low-resource settings. We sought to describe associations between the COVID-19 pandemic and surgical care and outcomes at 2 tertiary hospitals in Ethiopia. METHODS: We conducted a retrospective observational cohort study analyzing perioperative data collected electronically from Ayder Comprehensive Specialized Hospital (ACSH) in Mekelle, Ethiopia, and Tibebe Ghion Specialized Hospital (TGSH) in Bahir Dar, Ethiopia. We categorized COVID-19 exposure as time periods: "phase 0" before the pandemic (November 1-December 31, 2019, at ACSH and August 1-September 30, 2019, at TGSH), "phase 1" starting when elective surgeries were canceled (April 1-August 3, 2020, at ACSH and March 28-April 12, 2020, at TGSH), and "phase 2" starting when elective surgeries resumed (August 4-August 31, 2020, at ACSH and April 13-August 31, 2020, at TGSH). Outcomes included 28-day perioperative mortality, case volume, and patient district of origin. Incidence rates of case volume and patient district of origin (outside district yes or no) were modeled with segmented Poisson regression and logistic regression, respectively. Association of the exposure with 28-day mortality was assessed using logistic regression models, adjusting for confounders. RESULTS: Data from 3231 surgeries were captured. There was a decrease in case volume compared to phase 0, with adjusted incidence rate ratio (IRR) of 0.73 (95% confidence interval [CI], 0.66-0.81) in phase 1 and 0.90 (95% CI, 0.83-0.97) in phase 2. Compared to phase 0, there were more patients from an outside district during phase 1 lockdown at ACSH (adjusted odds ratio [aOR], 1.63 [95% CI, 1.24-2.15]) and fewer patients from outside districts at TGSH (aOR, 0.44 [95% CI, 0.21-0.87]). The observed 28-day mortality rates for phases 0, 1, and 2 were 1.8% (95% CI, 1.1-2.8), 3.7% (95% CI, 2.3-5.8), and 2.9% (95% CI, 2.1-3.9), respectively. A confounder-adjusted logistic regression model did not show a significant increase in 28-day perioperative mortality during phases 1 and 2 compared to phase 0, with aOR 1.36 (95% CI, 0.62-2.98) and 1.54 (95% CI, 0.80-2.95), respectively. CONCLUSIONS: Analysis at 2 low-resource referral hospitals in Ethiopia during the COVID-19 pandemic showed a reduction in surgical case volume during and after lockdown. At ACSH, more patients were from outside districts during lockdown where the opposite was true at TGSH. These findings suggest that during the pandemic patients may experience delays in seeking or obtaining surgical care. However, for patients who underwent surgery, prepandemic and postpandemic perioperative mortalities did not show significant difference. These results may inform surgical plans during future public health crises.

Global pediatric surgery and anesthesia inequities: how do we have a global effort?

PURPOSE OF REVIEW: The SARS-CoV-2 (COVID-19) pandemic has highlighted the inequities in access to healthcare while also revealing our global connectivity. These inequities are emblematic of decades of underinvestment in healthcare systems, education, and research in low-middle income countries (LMICs), especially in surgery and anesthesiology. Five billion people remain without access to safe surgery, and we must take appropriate action now. RECENT FINDINGS: The pediatric perioperative mortality in low-resourced settings may be as high as 100 times greater than in high-resourced settings, and a pediatric surgery workforce density benchmark of 4/1 million population could increase survivability to over 80%. Delay in treatment for congenital surgically correctable issues dramatically increases disability-adjusted life years. Appropriate academic partnerships which promote education are desired but the lack of authorship position priority for LMIC-based researchers must be addressed. Five perioperative benchmark indicators have been published including: geospatial access to care within 2 h of location; workforce/100,000 population; volume of surgery/100,000 population; perioperative mortality within 30 days of surgery or until discharged; and risks for catastrophic expenditure from surgical care. SUMMARY: Research that determines ethical and acceptable partnership development between high- and low-resourced settings focusing on education and capacity building needs to be standardized and followed.

Drastic Events and Gradual Change Define the Structure of an Active Copper-Zinc-Alumina Catalyst for Methanol Synthesis.

The copper-zinc-alumina (CZA) catalyst is one of the most important catalysts. Nevertheless, understanding of the complex CZA structure is still limited and hampers further optimization. Critical to the production of a highly active and stable catalyst are optimal start-up procedures in hydrogen. Here, by employing operando X-ray absorption spectroscopy and X-ray diffraction, we follow how the industrial CZA precursor evolves into the working catalyst. Two major events in the activation drastically alter the copper- and zinc-containing components in the CZA catalyst and define the final working catalyst structure: the reduction of the starting copper(II) oxide, and the ripening and re-oxidation of zinc oxide upon the switch to catalytic conditions. These drastic events are also accompanied by other gradual, structural changes. Understanding what happens during these events is key to develop tailored start-up protocols that are aimed at maximal longevity and activity of the catalysts.

Global surgery, obstetric, and anaesthesia indicator definitions and reporting: An Utstein consensus report.

BACKGROUND: Indicators to evaluate progress towards timely access to safe surgical, anaesthesia, and obstetric (SAO) care were proposed in 2015 by the Lancet Commission on Global Surgery. These aimed to capture access to surgery, surgical workforce, surgical volume, perioperative mortality rate, and catastrophic and impoverishing financial consequences of surgery. Despite being rapidly taken up by practitioners, data points from which to derive the indicators were not defined, limiting comparability across time or settings. We convened global experts to evaluate and explicitly define-for the first time-the indicators to improve comparability and support achievement of 2030 goals to improve access to safe affordable surgical and anaesthesia care globally. METHODS AND FINDINGS: The Utstein process for developing and reporting guidelines through a consensus building process was followed. In-person discussions at a 2-day meeting were followed by an iterative process conducted by email and virtual group meetings until consensus was reached. The meeting was held between June 16 to 18, 2019; discussions continued until August 2020. Participants consisted of experts in surgery, anaesthesia, and obstetric care, data science, and health indicators from high-, middle-, and low-income countries. Considering each of the 6 indicators in turn, we refined overarching descriptions and agreed upon data points needed for construction of each indicator at current time (basic data points), and as each evolves over 2 to 5 (intermediate) and >5 year (full) time frames. We removed one of the original 6 indicators (one of 2 financial risk protection indicators was eliminated) and refined descriptions and defined data points required to construct the 5 remaining indicators: geospatial access, workforce, surgical volume, perioperative mortality, and catastrophic expenditure. A strength of the process was the number of people from global institutes and multilateral agencies involved in the collection and reporting of global health metrics; a limitation was the limited number of participants from low- or middle-income countries-who only made up 21% of the total attendees. CONCLUSIONS: To track global progress towards timely access to quality SAO care, these indicators-at the basic level-should be implemented universally as soon as possible. Intermediate and full indicator sets should be achieved by all countries over time. Meanwhile, these evolutions can assist in the short term in developing national surgical plans and collecting more detailed data for research studies.

Factors influencing mothers' decisions regarding obstetrical care in Western Kenya: a mixed-methods study.

BACKGROUND: Siaya County in Western Kenya has one of the highest maternal mortality rates in Kenya. We sought to elucidate factors that influence mothers' decisions regarding where to seek obstetrical care, to inform interventions that seek to promote effective use of obstetric services and reduce maternal mortalities. To guide our research, we used the "Three Delays Model", focusing on the first delay-seeking care. While interventions to reduce maternal mortalities have focused on addressing delays in accessing and receiving care, context-specific data on drivers of the first delay are scarce. METHODS: We used a mixed-method study to assess how maternal decision-making of birth location is influenced by personal, contextual, and cultural factors. We conducted structured interviews with women aged 14 years or older living in Siaya, Bondo, and Yala, rural districts in Western Kenya. We then conducted focus group interviews with a subset of women to elucidate this question: How do drivers of the first delay (i.e., seeking care) affect the decision to seek home versus hospital delivery, potentially negatively influencing maternal mortality. RESULTS: Three hundred and seven women responded to the surveys, and 67 women (22%) from this group participated in focus group interviews. Although we focused on type 1 delays, we discovered that several factors that impact type 2 and type 3 delays directly contribute to type 1 delays. Our findings highlighted that factors influencing women's decisions to seek care are not simply medical or cultural but rather contextual, involving many elements of life, particularly in rural communities. CONCLUSIONS: It is imperative to address multiple-level factors that influence women's decisions to seek care and have in-hospital deliveries. To curtail maternal mortality in rural Western Kenya and comparable settings, targeted interventions must take into consideration these important influencers.

Propofol-induced uric acid crystals: A case of cloudy urine.

Propofol is an intravenous anesthetic agent commonly used intraoperatively as well as in the intensive care unit. Known short-term effects of propofol can include apnea, hypotension, and bradycardia. In children, the rarer adverse sequelae of intravenous anesthetics have received little attention. We present the case of a thirteen-year-old male who incidentally developed uric acid crystals in his urine following a short-duration propofol infusion.

Active sites and mechanisms in the direct conversion of methane to methanol using Cu in zeolitic hosts: a critical examination.

In this critical review we examine the current state of our knowledge in respect of the nature of the active sites in copper containing zeolites for the selective conversion of methane to methanol. We consider the varied experimental evidence arising from the application of X-ray diffraction, and vibrational, electronic, and X-ray spectroscopies that exist, along with the results of theory. We aim to establish both what is known regarding these elusive materials and how they function, and also where gaps in our knowledge still exist, and offer suggestions and strategies as to how these might be closed such that the rational design of more effective and efficient materials of this type for the selective conversion of methane might proceed further.

Heterogeneously Catalyzed Aerobic Oxidation of Methane to a Methyl Derivative.

A promising strategy to break through the selectivity-conversion limit of direct methane conversion to achieve high yields is the protection of methanol via esterification to a more stable methyl ester. We present an aerobic methane-to-methyl-ester approach that utilizes a highly dispersed, cobalt-containing solid catalyst, along with significantly more favorable reaction conditions compared to existing homogeneously-catalyzed approaches (e.g. diluted acid, O2 oxidant, moderate temperature and pressure). The trifluoroacetic acid medium is diluted (<25 wt %) with an inert fluorous co-solvent that can be recovered after the separation of the methyl trifluoroacetate via liquid-liquid extraction at ambient conditions. Silica-supported cobalt catalysts are highly active in this system, with competitive yields and turnovers in comparison to known aerobic transition metal-based catalytic systems.

Mechanistic Study of Carbon Dioxide Hydrogenation over Pd/ZnO-Based Catalysts: The Role of Palladium-Zinc Alloy in Selective Methanol Synthesis.

Pd/ZnO catalysts show good activity and high selectivity to methanol during catalytic CO2 hydrogenation. The Pd-Zn alloy phase has usually been considered as the active phase, though mechanistic studies under operando conditions have not been conducted to verify this. Here, we report a mechanistic study under realistic conditions of methanol synthesis, using in situ and operando X-ray absorption spectroscopy, X-ray powder diffraction, and time-resolved isotope labeling experiments coupled with FTIR spectroscopy and mass spectrometry. Pd-Zn alloy-based catalysts, prepared through reduction of a heterobimetallic PdII ZnII acetate bridge complex, and which do not contain zinc oxide or any PdZn/ZnO interface, produce mostly CO. The Pd-Zn phase is associated with the formation of CO, and does not provide the active sites required to produce methanol from the direct hydrogenation of carbon dioxide. The presence of a ZnO phase, in contact with a Pd-Zn phase, is essential for efficient methanol production.

Methane-to-Methanol on Mononuclear Copper(II) Sites Supported on Al2 O3 : Structure of Active Sites from Electron Paramagnetic Resonance*.

The selective conversion of methane to methanol remains one of the holy grails of chemistry, where Cu-exchanged zeolites have been shown promote this reaction under stepwise conditions. Over the years, several active sites have been proposed, ranging from mono-, di- to trimeric CuII . Herein, we report the formation of well-dispersed monomeric CuII species supported on alumina using surface organometallic chemistry and their reactivity towards the selective and stepwise conversion of methane to methanol. Extensive studies using various transition alumina supports combined with spectroscopic characterization, in particular electron paramagnetic resonance (EPR), show that the active sites are associated with specific facets, which are typically found in γ- and η-alumina phase, and that their EPR signature can be attributed to species having a tri-coordinated [(Al2 O)CuIIO(OH)]- T-shape geometry. Overall, the selective conversion of methane to methanol, a two-electron process, involves two monomeric CuII sites that play in concert.