scholarly journals Co@CoO: a Unique Catalyst for Hydrogenolysis of Biomass-derived 5-Hydroxymethylfurfural to 2,5-Dimethylfuran

2021 ◽  
Author(s):  
Shuang Xiang ◽  
Lin Dong ◽  
Zhiqiang Wang ◽  
Xue Han ◽  
Luke Daemen ◽  
...  
Keyword(s):  
Active Sites ◽  
Oxygen Vacancies ◽  
Computational Modelling ◽  
Renewable Biomass ◽  
Structured Catalyst ◽  
Excellent Activity ◽  
Catalytically Active ◽  
Fuels And Chemicals ◽  
Lignin Model ◽  
First Time

The development of precious-metal-free catalysts to promote the sustainable production of fuels and chemicals from biomass remains an important and challenging target. Here, we report the efficient hydrogenolysis of biomass-derived 5-hydroxymethylfurfural to 2,5-dimethylfuran over a unique core-shell structured catalyst Co@CoO that affords the highest productivity among all catalysts reported to date. Surprisingly, we found that the catalytically active sites reside on the shell of CoO with oxygen vacancies rather than the metallic Co. The combination of various spectroscopic experiments and computational modelling reveals that the CoO shell incorporating oxygen vacancies drives the heterolytic and homolytic cleavage of dihydrogen to yield active Hδ- species, resulting in the exceptional catalytic activity. Co@CoO also exhibits excellent activity toward the direct hydrodeoxygenation of lignin model compounds. This study unlocks, for the first time, the potential of metal-oxide catalysts for the production of renewable biomass-derived fuels.

Ultrathin NiCo2O4 nanosheets with dual-metal active sites for enhanced solar water splitting of a BiVO4 photoanode

2019 ◽  
Vol 7 (39) ◽  
pp. 22274-22278 ◽  
Author(s):  
Chenchen Feng ◽  
Qi Zhou ◽  
Bin Zheng ◽  
Xiang Cheng ◽  
Yajun Zhang ◽  
...  
Keyword(s):  
Water Splitting ◽  
Water Oxidation ◽  
Active Sites ◽  
Oxygen Vacancies ◽  
Solar Water ◽  
Solar Water Splitting ◽  
Highly Efficient ◽  
Dual Metal ◽  
Nico2o4 Nanosheets ◽  
First Time

Spinel-structured NiCo2O4 nanosheets with dual-metal active sites, an ultrathin structure, and abundant oxygen vacancies were decorated for the first time on a BiVO4 photoanode for highly efficient PEC water oxidation.

Structure of theMethanothermobacter thermautotrophicusexosome RNase PH ring

2010 ◽  
Vol 66 (5) ◽  
pp. 522-528 ◽  
Author(s):  
C. Leong Ng ◽  
David G. Waterman ◽  
Alfred A. Antson ◽  
Miguel Ortiz-Lombardía
Keyword(s):  
Rna Processing ◽  
Active Sites ◽  
Polar Regions ◽  
Polynucleotide Phosphorylase ◽  
The Core ◽  
Catalytically Active ◽  
Phosphate Anions ◽  
Methanothermobacter Thermautotrophicus ◽  
The Many ◽  
First Time

The core of the exosome, a versatile multisubunit RNA-processing enzyme found in archaea and eukaryotes, includes a ring of six RNase PH subunits. This basic architecture is homologous to those of the bacterial and archaeal RNase PHs and the bacterial polynucleotide phosphorylase (PNPase). While all six RNase PH monomers are catalytically active in the homohexameric RNase PH, only half of them are functional in the bacterial PNPase and in the archaeal exosome core and none are functional in the yeast and human exosome cores. Here, the crystal structure of the RNase PH ring from the exosome of the anaerobic methanogenic archaeonMethanothermobacter thermautotrophicusis described at 2.65 Å resolution. Free phosphate anions were found for the first time in the active sites of the RNase PH subunits of an exosome structure and provide structural snapshots of a critical intermediate in the phosphorolytic degradation of RNA by the exosome. Furthermore, the present structure highlights the plasticity of the surfaces delineating the polar regions of the RNase PH ring of the exosome, a feature that can facilitate both interaction with the many cofactors involved in exosome function and the processive activity of this enzyme.

Metalloporphyrin immobilized CeO2: in situ generation of active sites and synergistic promotion of photocatalytic water oxidation

2021 ◽  
Author(s):  
Jiao Meng ◽  
Yue Zhao ◽  
Haining Li ◽  
Ruiping Chen ◽  
Xun Sun ◽  
...  
Keyword(s):  
Water Oxidation ◽  
Active Sites ◽  
Oxygen Vacancies ◽  
Electron Coupling ◽  
Catalytically Active ◽  
In Situ Generation ◽  
The Creation

CoTCPP transfer photoexcited electrons to CeO2 by d–f electron coupling. The in situ generation of catalytically active sites: reduction on CeO2 accompanied with the creation of oxygen vacancies and oxidation on CoTCPP that transforms into CoOOH.

scholarly journals Precise Identification and Characterization of Catalytically Active Sites on the Surface of γ-Alumina

2020 ◽  
Author(s):  
Konstantin Khivantsev ◽  
Nicholas R. Jaegers ◽  
Ja-Hun Kwak ◽  
János Szanyi ◽  
Libor Kovarik
Keyword(s):  
Active Sites ◽  
Large Scale ◽  
High Surface ◽  
High Surface Area ◽  
Carbonyl Complexes ◽  
True Nature ◽  
Catalytically Active ◽  
Active Research ◽  
First Time

<p>γ-alumina is one of the oldest and most important commercial catalytic materials with high surface area and stability. These attributes enabled its use as the first commercial large-scale heterogeneous catalyst for ethanol dehydration. Despite progress in materials characterization and over a hundred years of active research, the nature of the specific sites on the surface of γ-alumina which are responsible for its unique catalytic properties has remained obscure and controversial. Herein, we identify for the first time using combined infrared spectroscopy, electron microscopy and solid-state nuclear magnetic resonance measurements that the octahedral amphoteric (O)<sub>5</sub>Al(VI)-OH sites on the massively restructured (110) facets on typical rhombus-platelet γ-alumina as well as (100) segments of irrational surfaces (invariably always present in all γ-alumina samples) are largely responsible for its unique catalytic activity. Such (O)<sub>5</sub>Al(VI)-OH sites are also present on macroscopically defined (100) facets γ-alumina of different, more elongated/rod-like geometry. They anchor organometallic fragments and isolated metal atoms. The exact mechanism by which these sites lose -OH group upon thermal dehydroxylation is clarified, resulting in coordinatively unsaturated penta-coordinate Al<sup>+3</sup>O<sub>5</sub> sites that can activate nitrogen. These coordinatively unsaturated Al penta-coordinate sites demonstrate new chemistry, producing the first well-defined thermally stable Al-carbonyl complexes. Our findings reunite and successfully clarify the contradictory findings in the literature over the last century, illuminating the true nature and the relationship between the catalytically active and coordinatively unsaturated Al sites on the surface of γ-alumina.</p>

scholarly journals Precise Identification and Characterization of Catalytically Active Sites on the Surface of γ-Alumina

2020 ◽  
Author(s):  
Konstantin Khivantsev ◽  
Nicholas R. Jaegers ◽  
Ja-Hun Kwak ◽  
János Szanyi ◽  
Libor Kovarik
Keyword(s):  
Active Sites ◽  
Large Scale ◽  
High Surface ◽  
High Surface Area ◽  
Carbonyl Complexes ◽  
True Nature ◽  
Catalytically Active ◽  
Active Research ◽  
First Time

<p>γ-alumina is one of the oldest and most important commercial catalytic materials with high surface area and stability. These attributes enabled its use as the first commercial large-scale heterogeneous catalyst for ethanol dehydration. Despite progress in materials characterization and over a hundred years of active research, the nature of the specific sites on the surface of γ-alumina which are responsible for its unique catalytic properties has remained obscure and controversial. Herein, we identify for the first time using combined infrared spectroscopy, electron microscopy and solid-state nuclear magnetic resonance measurements that the octahedral amphoteric (O)<sub>5</sub>Al(VI)-OH sites on the massively restructured (110) facets on typical rhombus-platelet γ-alumina as well as (100) segments of irrational surfaces (invariably always present in all γ-alumina samples) are largely responsible for its unique catalytic activity. Such (O)<sub>5</sub>Al(VI)-OH sites are also present on macroscopically defined (100) facets γ-alumina of different, more elongated/rod-like geometry. They anchor organometallic fragments and isolated metal atoms. The exact mechanism by which these sites lose -OH group upon thermal dehydroxylation is clarified, resulting in coordinatively unsaturated penta-coordinate Al<sup>+3</sup>O<sub>5</sub> sites that can activate nitrogen. These coordinatively unsaturated Al penta-coordinate sites demonstrate new chemistry, producing the first well-defined thermally stable Al-carbonyl complexes. Our findings reunite and successfully clarify the contradictory findings in the literature over the last century, illuminating the true nature and the relationship between the catalytically active and coordinatively unsaturated Al sites on the surface of γ-alumina.</p>

Recycling and Reuse in the Roman Economy

2020 ◽  
Keyword(s):  
Building Materials ◽  
Computational Modelling ◽  
Late Antique ◽  
Roman Economy ◽  
Wide Range ◽  
The Status ◽  
Recent Developments ◽  
Methodological Approaches ◽  
First Time ◽  
Site Types

The recycling and reuse of materials and objects were extensive in the past, but have rarely been embedded into models of the economy; even more rarely has any attempt been made to assess the scale of these practices. Recent developments, including the use of large datasets, computational modelling, and high-resolution analytical chemistry, are increasingly offering the means to reconstruct recycling and reuse, and even to approach the thorny matter of quantification. Growing scholarly interest in the topic has also led to an increasing recognition of these practices from those employing more traditional methodological approaches, which are sometimes coupled with innovative archaeological theory. Thanks to these efforts, it has been possible for the first time in this volume to draw together archaeological case studies on the recycling and reuse of a wide range of materials, from papyri and textiles, to amphorae, metals and glass, building materials and statuary. Recycling and reuse occur at a range of site types, and often in contexts which cross-cut material categories, or move from one object category to another. The volume focuses principally on the Roman Imperial and late antique world, over a broad geographical span ranging from Britain to North Africa and the East Mediterranean. Last, but not least, the volume is unique in focusing upon these activities as a part of the status quo, and not just as a response to crisis.

scholarly journals The antimicrobial potential of cannabidiol

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Mark A. T. Blaskovich ◽  
Angela M. Kavanagh ◽  
Alysha G. Elliott ◽  
Bing Zhang ◽  
Soumya Ramu ◽  
...  
Keyword(s):  
Bacterial Infections ◽  
Modern Medicine ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
New Class ◽  
Clostridioides Difficile ◽  
Excellent Activity ◽  
Induce Resistance ◽  
First Time

AbstractAntimicrobial resistance threatens the viability of modern medicine, which is largely dependent on the successful prevention and treatment of bacterial infections. Unfortunately, there are few new therapeutics in the clinical pipeline, particularly for Gram-negative bacteria. We now present a detailed evaluation of the antimicrobial activity of cannabidiol, the main non-psychoactive component of cannabis. We confirm previous reports of Gram-positive activity and expand the breadth of pathogens tested, including highly resistant Staphylococcus aureus, Streptococcus pneumoniae, and Clostridioides difficile. Our results demonstrate that cannabidiol has excellent activity against biofilms, little propensity to induce resistance, and topical in vivo efficacy. Multiple mode-of-action studies point to membrane disruption as cannabidiol’s primary mechanism. More importantly, we now report for the first time that cannabidiol can selectively kill a subset of Gram-negative bacteria that includes the ‘urgent threat’ pathogen Neisseria gonorrhoeae. Structure-activity relationship studies demonstrate the potential to advance cannabidiol analogs as a much-needed new class of antibiotics.

scholarly journals Insights on forming N,O-coordinated Cu single-atom catalysts for electrochemical reduction CO2 to methane

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yanming Cai ◽  
Jiaju Fu ◽  
Yang Zhou ◽  
Yu-Chung Chang ◽  
Qianhao Min ◽  
...  
Keyword(s):  
Energy Barrier ◽  
Active Sites ◽  
Theoretical Calculations ◽  
High Energy ◽  
Single Atom ◽  
Faradaic Efficiency ◽  
High Energy Barrier ◽  
Catalytic Sites ◽  
Electron Reduction ◽  
First Time

AbstractSingle-atom catalysts (SACs) are promising candidates to catalyze electrochemical CO2 reduction (ECR) due to maximized atomic utilization. However, products are usually limited to CO instead of hydrocarbons or oxygenates due to unfavorable high energy barrier for further electron transfer on synthesized single atom catalytic sites. Here we report a novel partial-carbonization strategy to modify the electronic structures of center atoms on SACs for lowering the overall endothermic energy of key intermediates. A carbon-dots-based SAC margined with unique CuN2O2 sites was synthesized for the first time. The introduction of oxygen ligands brings remarkably high Faradaic efficiency (78%) and selectivity (99% of ECR products) for electrochemical converting CO2 to CH4 with current density of 40 mA·cm-2 in aqueous electrolytes, surpassing most reported SACs which stop at two-electron reduction. Theoretical calculations further revealed that the high selectivity and activity on CuN2O2 active sites are due to the proper elevated CH4 and H2 energy barrier and fine-tuned electronic structure of Cu active sites.

scholarly journals Study on the adsorption selection of CH$$_4$$ on CuO (110) versus (111) surfaces: a density functional theory study

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
Long Lin ◽  
Linwei Yao ◽  
Shaofei Li ◽  
Zhengguang Shi ◽  
Kun Xie ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Adsorption Capacity ◽  
Active Sites ◽  
Density Functional ◽  
Oxygen Vacancies ◽  
Density Functional Theory Calculations ◽  
Density Functional Theory Study ◽  
Functional Theory ◽  
Strong Adsorption ◽  
Selection Of

AbstractFinding the active sites of suitable metal oxides is a key prerequisite for detecting CH$$_4$$ 4 . The purpose of the paper is to investigate the adsorption of CH$$_4$$ 4 on intrinsic and oxygen-vacancies CuO (111) and (110) surfaces using density functional theory calculations. The results show that CH$$_4$$ 4 has a strong adsorption energy of −0.370 to 0.391 eV at all site on the CuO (110) surface. The adsorption capacity of CH$$_4$$ 4 on CuO (111) surface is weak, ranging from −0.156 to −0.325 eV. In the surface containing oxygen vacancies, the adsorption capacity of CuO surface to CH$$_4$$ 4 is significantly stronger than that of intrinsic CuO surface. The results indicate that CuO (110) has strong adsorption and charge transfer capacity for CH$$_4$$ 4 , which may provide experimental guidance.

scholarly journals Manganese vacancy-confined single-atom Ag in cryptomelane nanorods for efficient Wacker oxidation of styrene derivatives

2021 ◽  
Author(s):  
Hongling Yang ◽  
Xun Zhang ◽  
Yi Yu ◽  
Zheng Chen ◽  
Qinggang Liu ◽  
...  
Keyword(s):  
Molecular Sieve ◽  
Active Sites ◽  
Single Atom ◽  
Wacker Oxidation ◽  
Catalytically Active ◽  
Styrene Derivatives

Single-atom catalysts provide a pathway to elucidate the nature of catalytically active sites. However, keeping them stabilized during operation proves to be challenging. Herein, we employ cryptomelane-type octahedral molecular sieve...

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