scholarly journals Promoting ethylene production over a wide potential window on Cu crystallites induced and stabilized via current shock and charge delocalization

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Hao Sun ◽  
Ling Chen ◽  
Likun Xiong ◽  
Kun Feng ◽  
Yufeng Chen ◽  
...  
Keyword(s):  
Metal Ion ◽  
Density Functional ◽  
Metal Organic Framework ◽  
Density Functional Theory Calculations ◽  
Catalyst Design ◽  
Potential Range ◽  
Efficient Manner ◽  
Faradaic Efficiency ◽  
Charge Delocalization ◽  
Wide Potential

AbstractElectrochemical CO2 reduction (CO2RR) in a product-orientated and energy-efficient manner relies on rational catalyst design guided by mechanistic understandings. In this study, the effect of conducting support on the CO2RR behaviors of semi-conductive metal-organic framework (MOF) — Cu3(HITP)2 are carefully investigated. Compared to the stand-alone MOF, adding Ketjen Black greatly promotes C2H4 production with a stabilized Faradaic efficiency between 60-70% in a wide potential range and prolonged period. Multicrystalline Cu nano-crystallites in the reconstructed MOF are induced and stabilized by the conducting support via current shock and charge delocalization, which is analogous to the mechanism of dendrite prevention through conductive scaffolds in metal ion batteries. Density functional theory calculations elucidate that the contained multi-facets and rich grain boundaries promote C–C coupling while suppressing HER. This study underlines the key role of substrate-catalyst interaction, and the regulation of Cu crystalline states via conditioning the charge transport, in steering the CO2RR pathway.

Towards a Design of Active Oxygen Evolution Catalysts: Insights from Automated Density Functional Theory Calculations and Machine Learning

2019 ◽  
Author(s):  
Seoin Back ◽  
Kevin Tran ◽  
Zachary Ulissi
Keyword(s):  
Machine Learning ◽  
Oxygen Evolution ◽  
Active Sites ◽  
Density Functional ◽  
Chemical Space ◽  
Density Functional Theory Calculations ◽  
Catalyst Design ◽  
Transition Metal Catalysts ◽  
Oxide Materials ◽  
Design Strategies

<div> <div> <div> <div><p>Developing active and stable oxygen evolution catalysts is a key to enabling various future energy technologies and the state-of-the-art catalyst is Ir-containing oxide materials. Understanding oxygen chemistry on oxide materials is significantly more complicated than studying transition metal catalysts for two reasons: the most stable surface coverage under reaction conditions is extremely important but difficult to understand without many detailed calculations, and there are many possible active sites and configurations on O* or OH* covered surfaces. We have developed an automated and high-throughput approach to solve this problem and predict OER overpotentials for arbitrary oxide surfaces. We demonstrate this for a number of previously-unstudied IrO2 and IrO3 polymorphs and their facets. We discovered that low index surfaces of IrO2 other than rutile (110) are more active than the most stable rutile (110), and we identified promising active sites of IrO2 and IrO3 that outperform rutile (110) by 0.2 V in theoretical overpotential. Based on findings from DFT calculations, we pro- vide catalyst design strategies to improve catalytic activity of Ir based catalysts and demonstrate a machine learning model capable of predicting surface coverages and site activity. This work highlights the importance of investigating unexplored chemical space to design promising catalysts.<br></p></div></div></div></div><div><div><div> </div> </div> </div>

scholarly journals H2O coordination in macropa complexes of f elements (Ac, La, Lu): feasibility of the 11th coordination site

2021 ◽  
Author(s):  
Attila Kovács ◽  
Zoltán Varga
Keyword(s):  
Aqueous Solution ◽  
Metal Ion ◽  
Density Functional ◽  
Molecular Level ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Coordination Site ◽  
Additional Ligand ◽  
Ligand Coordination ◽  
Bonding Properties

AbstractThe feasibility of an additional ligand coordination at the 11th coordination site of actinium, lanthanum, and lutetium ions in 10-fold coordinated macropa complexes has been studied by means of density functional theory calculations. The study covered the two main macropa conformers, Δ(δλδ)(δλδ) and Δ(λδλ)(λδλ), favoured by larger (Ac3+, La3+) and smaller (Lu3+) ions, respectively. At the molecular level, the coordination of H2O is the most favourable to the largest Ac3+ while only slightly less to La3+. Protonation of the picoline arms enhances the coordination by shifting the metal ion closer to the open site of the ligand. The choice of macropa conformer has only a slight influence on the strength and bonding properties of the H2O coordination. Aqueous solution environment decreases considerably the energy gain of H2O coordination at the 11th coordination site.

scholarly journals Selective capture of carbon dioxide from hydrocarbons using a metal-organic framework

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Omid T. Qazvini ◽  
Ravichandar Babarao ◽  
Shane G. Telfer
Keyword(s):  
Carbon Dioxide ◽  
Density Functional ◽  
Metal Organic Framework ◽  
Density Functional Theory Calculations ◽  
Time Lags ◽  
X Ray Crystallography ◽  
Metal Organic ◽  
Adsorption Of Co ◽  
Short Time ◽  
Organic Framework

AbstractEfficient and sustainable methods for carbon dioxide capture are highly sought after. Mature technologies involve chemical reactions that absorb CO2, but they have many drawbacks. Energy-efficient alternatives may be realised by porous physisorbents with void spaces that are complementary in size and electrostatic potential to molecular CO2. Here, we present a robust, recyclable and inexpensive adsorbent termed MUF-16. This metal-organic framework captures CO2 with a high affinity in its one-dimensional channels, as determined by adsorption isotherms, X-ray crystallography and density-functional theory calculations. Its low affinity for other competing gases delivers high selectivity for the adsorption of CO2 over methane, acetylene, ethylene, ethane, propylene and propane. For equimolar mixtures of CO2/CH4 and CO2/C2H2, the selectivity is 6690 and 510, respectively. Breakthrough gas separations under dynamic conditions benefit from short time lags in the elution of the weakly-adsorbed component to deliver high-purity hydrocarbon products, including pure methane and acetylene.

scholarly journals Exposing unsaturated Cu1-O2 sites in nanoscale Cu-MOF for efficient electrocatalytic hydrogen evolution

2021 ◽  
Vol 7 (18) ◽  
pp. eabg2580
Author(s):  
Weiren Cheng ◽  
Huabin Zhang ◽  
Deyan Luan ◽  
Xiong Wen (David) Lou
Keyword(s):  
Hydrogen Evolution ◽  
Density Functional ◽  
Metal Organic Framework ◽  
Density Functional Theory Calculations ◽  
Active Centers ◽  
Functional Theory ◽  
Hollow Nanostructure ◽  
Metal Organic ◽  
X Ray Absorption ◽  
A Current

Conductive metal-organic framework (MOF) materials have been recently considered as effective electrocatalysts. However, they usually suffer from two major drawbacks, poor electrochemical stability and low electrocatalytic activity in bulk form. Here, we have developed a rational strategy to fabricate a promising electrocatalyst composed of a nanoscale conductive copper-based MOF (Cu-MOF) layer fully supported over synergetic iron hydr(oxy)oxide [Fe(OH)x] nanoboxes. Owing to the highly exposed active centers, enhanced charge transfer, and robust hollow nanostructure, the obtained Fe(OH)x@Cu-MOF nanoboxes exhibit superior activity and stability for the electrocatalytic hydrogen evolution reaction (HER). Specifically, it needs an overpotential of 112 mV to reach a current density of 10 mA cm−2 with a small Tafel slope of 76 mV dec−1. X-ray absorption fine structure spectroscopy combined with density functional theory calculations unravels that the highly exposed coordinatively unsaturated Cu1-O2 centers could effectively accelerate the formation of key *H intermediates toward fast HER kinetics.

scholarly journals Zn Doping Induced Band Gap Widening of Ag2O Nanoparticles

2019 ◽  
Author(s):  
Arup Kumar De ◽  
Sourav Majumdar ◽  
Shaili Pal ◽  
Sunil Kumar ◽  
Indrajit Sinha
Keyword(s):  
Metal Ion ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Mole Percent ◽  
Functional Theory ◽  
Ion Density ◽  
Calculated Density ◽  
Zn Doping ◽  
Narrow Bandgap ◽  
Ag2o Nanoparticles

<p></p><p>Semiconductor bandgap widening is a little investigated phenomenon in photocatalysis literature. The present investigation attempts the widening of the narrow bandgap of Ag<sub>2</sub>O to make it a semiconductor with more attractive properties. The synthesis of Zn doped Ag<sub>2</sub>O nanostructures followed a typical hydrothermal synthesis procedure. An increase in the lattice parameters of Ag<sub>2</sub>O with doping indicated the occupation of an interstitial position by the dopant metal ion. Density functional theory calculations also demonstrated the expansion of the Ag<sub>2</sub>O crystal lattice with the dopant at an interstitial location. The bandgap of the Ag<sub>2</sub>O increased to 1.65 eV for 5-mole percent doping. The DFT calculated density of states (DOS) plots also exhibit an increase in the bandgap of Ag<sub>2</sub>O after Zn doping. These doped Ag<sub>2</sub>O nanoparticles were useful in photocatalysis of methyl orange degradation under visible light irradiation.</p><p></p>

scholarly journals Elucidating the Drug Release from Metal-Organic Framework Nanocomposites via in Situ Synchrotron Microspectroscopy and Theoretical Modelling

2019 ◽  
Author(s):  
Barbara Souza ◽  
Lorenzo Dona ◽  
Kirill Titov ◽  
Paolo Bruzzese ◽  
Zhixin Zeng ◽  
...  
Keyword(s):  
Drug Delivery ◽  
Drug Release ◽  
Density Functional ◽  
Metal Organic Framework ◽  
Density Functional Theory Calculations ◽  
Theoretical Modelling ◽  
Time Resolved ◽  
Drug Molecules ◽  
Metal Organic

Nanocomposites comprising metal-organic frameworks (MOFs) embedded in a polymeric matrix are promising carriers for drug delivery applications. While understanding the chemical and physical transformations of MOFs during the release of confined drug molecules is challenging, this is central to devising better ways for controlled release of therapeutic agents. Herein we demonstrate the efficacy of synchrotron microspectroscopy to track the in situ release of 5-fluorouracil (5-FU) anticancer drug molecules from a drug@MOF/polymer composite (5-FU@HKUST-1/polyurethane). Using experimental time-resolved infrared spectra jointly with newly developed density functional theory calculations, we reveal the detailed dynamics of vibrational motions underpinning the dissociation of 5-FU bound to the framework of HKUST-1 upon water exposure. We discover that HKUST-1 creates hydrophilic channels within the hydrophobic polyurethane matrix hence helping to tune drug release rate. The synergy between a hydrophilic MOF with a hydrophobic polymer can be harnessed to engineer a tunable nanocomposite that alleviates the unwanted burst effect commonly encountered in drug delivery.<br>

scholarly journals Mechanochemical Synthesis of a Mercury(II) Metal-Organic Framework Reveals a Two-Dimensional Polymorph Stabilized by Weak Interactions

2019 ◽  
Author(s):  
Isaiah R. Speight ◽  
Igor Huskić ◽  
Mihails Arhangelskis ◽  
Hatem M. Titi ◽  
Robin Stein ◽  
...  
Keyword(s):  
Density Functional ◽  
Weak Interactions ◽  
Metal Organic Framework ◽  
Three Dimensional ◽  
Density Functional Theory Calculations ◽  
Dimensional Structure ◽  
Reaction Monitoring ◽  
Two Dimensional ◽  
Functional Theory ◽  
Metal Organic

Solid-state mechanochemistry revealed a novel polymorph of the mercury(II) imidazolate framework, based on square-grid (sql) topology layers. Reaction monitoring and periodic density functional theory calculations show that the sql-structure is of higher stability than the previously reported three-dimensional structure, with the unexpected stabilization of a lower dimensionality structure explained by contributions of weak interactions, which include short C-H···Hg contacts.

scholarly journals Elucidating the Drug Release from Metal-Organic Framework Nanocomposites via in Situ Synchrotron Microspectroscopy and Theoretical Modelling

2019 ◽  
Author(s):  
Barbara Souza ◽  
Lorenzo Dona ◽  
Kirill Titov ◽  
Paolo Bruzzese ◽  
Zhixin Zeng ◽  
...  
Keyword(s):  
Drug Delivery ◽  
Drug Release ◽  
Density Functional ◽  
Metal Organic Framework ◽  
Density Functional Theory Calculations ◽  
Theoretical Modelling ◽  
Time Resolved ◽  
Drug Molecules ◽  
Metal Organic

Nanocomposites comprising metal-organic frameworks (MOFs) embedded in a polymeric matrix are promising carriers for drug delivery applications. While understanding the chemical and physical transformations of MOFs during the release of confined drug molecules is challenging, this is central to devising better ways for controlled release of therapeutic agents. Herein we demonstrate the efficacy of synchrotron microspectroscopy to track the in situ release of 5-fluorouracil (5-FU) anticancer drug molecules from a drug@MOF/polymer composite (5-FU@HKUST-1/polyurethane). Using experimental time-resolved infrared spectra jointly with newly developed density functional theory calculations, we reveal the detailed dynamics of vibrational motions underpinning the dissociation of 5-FU bound to the framework of HKUST-1 upon water exposure. We discover that HKUST-1 creates hydrophilic channels within the hydrophobic polyurethane matrix hence helping to tune drug release rate. The synergy between a hydrophilic MOF with a hydrophobic polymer can be harnessed to engineer a tunable nanocomposite that alleviates the unwanted burst effect commonly encountered in drug delivery.<br>

scholarly journals Tracking structural evolution: operando regenerative CeOx/Bi interface structure for high-performance CO2 electroreduction

2020 ◽  
Author(s):  
Ruichao Pang ◽  
Pengfei Tian ◽  
Hongliang Jiang ◽  
Minghui Zhu ◽  
Xiaozhi Su ◽  
...  
Keyword(s):  
High Performance ◽  
Density Functional ◽  
Structural Evolution ◽  
Density Functional Theory Calculations ◽  
Active Phase ◽  
Interface Structure ◽  
Operating Conditions ◽  
Faradaic Efficiency ◽  
Co2 Electroreduction ◽  
Water Activation

Abstract Unveiling the structural evolution and working mechanism of catalysts under realistic operating conditions is crucial for the design of efficient electrocatalysts for CO2 electroreduction, yet remains highly challenging. Here, by virtue of operando structural measurements at multiscale levels, it is identified under CO2 electroreduction conditions that an as-prepared CeO2/BiOCl precatalyst gradually evolves into CeOx/Bi interface structure with enriched Ce3+ species, which serves as the real catalytically active phase. The derived CeOx/Bi interface structure compared to pure Bi counterpart delivers substantially enhanced performance with a formate Faradaic efficiency approaching 90% for 24 hours in a wide potential window. The formate Faradaic efficiency can be further increased by using isotope D2O instead of H2O. Density functional theory calculations suggest that the regenerative CeOx/Bi interfacial sites can not only promote water activation to increase local *H species for CO2 protonation appropriately, but also stabilize the key intermediate *OCHO in formate pathway.

scholarly journals Molecular Rh(III) and Ir(III) Catalysts Immobilized on Bipyridine-Based Covalent Triazine Frameworks for the Hydrogenation of CO2 to Formate

Catalysts ◽  
2018 ◽  
Vol 8 (7) ◽  
pp. 295 ◽  
Author(s):  
Gunniya Gunasekar ◽  
Kwangho Park ◽  
Hyeonseok Jeong ◽  
Kwang-Deog Jung ◽  
Kiyoung Park ◽  
...  
Keyword(s):  
Density Functional ◽  
Three Dimensional ◽  
Catalytic Efficiency ◽  
Density Functional Theory Calculations ◽  
Catalyst Design ◽  
Two Dimensional ◽  
Functional Theory ◽  
Hydrogenation Of Co2 ◽  
Catalytic Reactivity ◽  
Reduced Activity

The catalytic reactivity of molecular Rh(III)/Ir(III) catalysts immobilized on two- and three-dimensional Bipyridine-based Covalent Triazine Frameworks (bpy-CTF) for the hydrogenation of CO2 to formate has been described. The heterogenized Ir complex demonstrated superior catalytic efficiency over its Rh counterpart. The Ir catalyst immobilized on two-dimensional bpy-CTF showed an improved turnover frequency and turnover number compared to its three-dimensional counterpart. The two-dimensional Ir catalyst produced a maximum formate concentration of 1.8 M and maintained its catalytic efficiency over five consecutive runs with an average of 92% in each cycle. The reduced activity after recycling was studied by density functional theory calculations, and a plausible leaching pathway along with a rational catalyst design guidance have been proposed.

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