scholarly journals Enhanced Catalysis of Pt3 Clusters Supported on Graphene for N–H Bond Dissociation

CCS Chemistry ◽  
2019 ◽  
Vol 1 (2) ◽  
pp. 215-225 ◽  
Author(s):  
Chaonan Cui ◽  
Zhixun Luo ◽  
Jiannian Yao
Keyword(s):  
Density Of States ◽  
Lewis Acid ◽  
Active Sites ◽  
Metal Cluster ◽  
Catalytic Performance ◽  
Pristine Graphene ◽  
Acid Base ◽  
Activation Barriers ◽  
Bond Dissociation ◽  
Defective Graphene

We report an in-depth study of catalytic N–H bond dissociation with typical platinum clusters on graphene supports. Among all the pristine graphene- and defective graphene-supported Pt clusters of different sizes that were studied, the Pt 3/G cluster possesses the highest reactivity and lowest activation barriers for each step of N–H dissociation in the decomposition of ammonia. In analyzing the reaction coordinates and projected density of states of the outermost orbitals, we found that the standing triangular Pt 3 on graphene creates prominent Lewis acid/base pair sites, which accommodate the adsorption and subsequent dissociation of *NH x . In comparison, Pt 1 lacks complementary active sites (CAS), causing it to be adverse to nucleophilic reactions, and in contrast, the Pt 13 cluster has weakened interactions and depleted charge density from the support, resulting in the elimination of the CAS effect. A stable pyramid-structured Pt 4 also develops Lewis acid/base sites, especially on defective graphene, but the density of states is still lower than the stand-up Pt 3/G. These findings strongly demonstrate the importance and necessity of cluster active sites for catalytic reactions of polar molecules, novel three-atoms metal cluster catalysis, and the selectivity and catalytic performance in the designing of ammonia fuel cells.

Solar-Driven Glucose Isomerization into Fructose via Transient Lewis Acid–Base Active Sites

ACS Catalysis ◽  
2021 ◽  
pp. 12170-12178
Author(s):  
Jiu Wang ◽  
Heng Zhao ◽  
Bicheng Zhu ◽  
Stephen Larter ◽  
Shaowen Cao ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Active Sites ◽  
Acid Base ◽  
Glucose Isomerization

scholarly journals Influence of incorporating a small amount of silica on the catalytic performance of a MoO3/Al2O3 catalyst in ethanol oxidative dehydrogenation

2018 ◽  
Vol 16 (6) ◽  
Author(s):  
Aline Villarreal ◽  
Gabriella Garbarino ◽  
Paola Riani ◽  
Aida Gutiérrez Alejandre ◽  
Jorge Ramírez ◽  
...  
Keyword(s):  
Oxidative Dehydrogenation ◽  
Active Sites ◽  
Catalytic Performance ◽  
Redox Behavior ◽  
Acid Base ◽  
Pure Alumina ◽  
Molybdenum Catalyst ◽  
Al2o3 Catalyst ◽  
Dehydrogenation Of Ethanol

The influence of incorporating a small amount of silica on the catalytic performance of MoO3/Al2O3 catalyst was studied. Molybdenum supported on pure alumina and 5% SiO2-Al2O3 supports were synthesized. The catalysts were characterized by XRD, Raman, UV-Vis and IR spectroscopies, FE-SEM microscopy, and their activity was evaluated in the oxidative dehydrogenation of ethanol to acetaldehyde. Molybdenum supported on pure alumina gives a 74% yield to acetaldehyde (at 573 K) due to the generation of oxy-dehydrogenation active sites by molybdenum and to the decrement of the alumina dehydration sites. For the molybdenum catalyst supported on silica-containing alumina, the molybdenum species were displaced from the strongest alumina’s acid-base couples, located on nanoparticles edges, corners and defects, to weaker ones located on plane faces causing the rise of weakly bonded species with less active redox behavior.  

scholarly journals Interplay of hemilability and redox activity in models of hydrogenase active sites

2017 ◽  
Vol 114 (46) ◽  
pp. E9775-E9782 ◽  
Author(s):  
Shengda Ding ◽  
Pokhraj Ghosh ◽  
Marcetta Y. Darensbourg ◽  
Michael B. Hall
Keyword(s):  
Lewis Acid ◽  
Hydrogen Evolution Reaction ◽  
Resting State ◽  
Active Sites ◽  
Reductive Elimination ◽  
Lewis Base ◽  
Redox Activity ◽  
Production Mechanism ◽  
Acid Base ◽  
Redox Active

The hydrogen evolution reaction, as catalyzed by two electrocatalysts [M(N2S2)·Fe(NO)2]+, [Fe-Fe]+ (M = Fe(NO)) and [Ni-Fe]+ (M = Ni) was investigated by computational chemistry. As nominal models of hydrogenase active sites, these bimetallics feature two kinds of actor ligands: Hemilabile, MN2S2 ligands and redox-active, nitrosyl ligands, whose interplay guides the H2 production mechanism. The requisite base and metal open site are masked in the resting state but revealed within the catalytic cycle by cleavage of the MS–Fe(NO)2 bond from the hemilabile metallodithiolate ligand. Introducing two electrons and two protons to [Ni-Fe]+ produces H2 from coupling a hydride temporarily stored on Fe(NO)2 (Lewis acid) and a proton accommodated on the exposed sulfur of the MN2S2 thiolate (Lewis base). This Lewis acid–base pair is initiated and preserved by disrupting the dative donation through protonation on the thiolate or reduction on the thiolate-bound metal. Either manipulation modulates the electron density of the pair to prevent it from reestablishing the dative bond. The electron-buffering nitrosyl’s role is subtler as a bifunctional electron reservoir. With more nitrosyls as in [Fe-Fe]+, accumulated electronic space in the nitrosyls’ π*-orbitals makes reductions easier, but redirects the protonation and reduction to sites that postpone the actuation of the hemilability. Additionally, two electrons donated from two nitrosyl-buffered irons, along with two external electrons, reduce two protons into two hydrides, from which reductive elimination generates H2.

Cleaving DNA-model phosphodiester with Lewis acid–base catalytic sites in bifunctional Zr–MOFs

2019 ◽  
Vol 48 (23) ◽  
pp. 8044-8048 ◽  
Author(s):  
Ying-Hua Zhou ◽  
Zhiyan Zhang ◽  
Margaret Patrick ◽  
Fan Yang ◽  
Rangling Wei ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Active Sites ◽  
Lewis Base ◽  
Zinc Hydroxide ◽  
Acid Base ◽  
Enhanced Activity ◽  
Nitrophenyl Phosphate ◽  
Catalytic Sites ◽  
Catalytic Active Sites ◽  
Hydrolysis Of

UiO-67-bpydc-Zn with isolated multi-catalytic active sites was fabricated as a catalyst for the hydrolysis of bis(p-nitrophenyl) phosphate as a DNA model. The enhanced activity may likely be attributed to the cooperation effects between the Lewis acid from the zirconium center at the node and the zinc hydroxide Lewis base in the linkers.

Cycloaddition Reactions of Dienes on the SI(100)-2 × 1 Surface

2003 ◽  
Vol 17 (08n09) ◽  
pp. 1205-1210 ◽  
Author(s):  
Cheol Ho Choi ◽  
Mark S. Gordon
Keyword(s):  
Lewis Acid ◽  
Potential Energy Surfaces ◽  
Surface Reaction ◽  
Lewis Base ◽  
Acid Base ◽  
Activation Barriers ◽  
Type Complex ◽  
Mechanical Methods ◽  
Energy Surfaces ◽  
Base Substrate

Quantum mechanical methods were adopted to study the surface reaction mechanisms of 1, 3-cyclohexadiene and acrylonitrile on the Si(100)-2x1 surface. According to the computed potential energy surfaces, both ⌊4+2⌋ and ⌊2+2⌋ cycloaddition products resulting from the reactions of surface dimers are possible due to the negligible activation barriers at the surface. Isomerization reactions among the surface products are very unlikely due to the predicted large activation barriers preventing thermal redistributions of the surface products. As a result, the distribution of the final surface products is kinetically controlled leading to a reinterpretation of recent experiments. An intermediate Lewis acid-base type complex appears in both the ⌊4+2⌋ and ⌊2+2⌋ cycloadditions of acrylonitrile entrance channels, indicating that the surface may act as an electrophile/Lewis acid towards a strong Lewis base substrate.

B-Doped and NH2-functionalized SBA-15 with hydrogen bond donor groups for effective catalysis of CO2 cycloaddition to epoxides

2020 ◽  
Vol 7 (19) ◽  
pp. 3636-3645 ◽  
Author(s):  
Yifei Ye ◽  
Dazhi Li ◽  
Ping Xu ◽  
Jianmin Sun
Keyword(s):  
Hydrogen Bond ◽  
Lewis Acid ◽  
Catalytic Performance ◽  
Solvent Free ◽  
The Novel ◽  
Hydrogen Bond Donor ◽  
Acid Base ◽  
Solvent Free Conditions ◽  
Base Properties

The novel B-SBA-15-NH2 catalyst with Lewis acid–base properties and hydrogen bond donor groups exhibited good catalytic performance for CO2 conversion under metal- and solvent-free conditions.

The design and catalytic performance of molybdenum active sites on an MCM-41 framework for the aerobic oxidation of 5-hydroxymethylfurfural to 2,5-diformylfuran

2019 ◽  
Vol 9 (3) ◽  
pp. 811-821 ◽  
Author(s):  
Zhao-Meng Wang ◽  
Li-Juan Liu ◽  
Bo Xiang ◽  
Yue Wang ◽  
Ya-Jing Lyu ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Active Sites ◽  
Aerobic Oxidation ◽  
Catalytic Performance ◽  
Mcm 41

The catalytic activity decreases as –(SiO)3Mo(OH)(O) > –(SiO)2Mo(O)2 > –(O)4–MoO.

Catalytic Resonance Theory: Parallel Reaction Pathway Control

2019 ◽  
Author(s):  
M. Alexander Ardagh ◽  
Manish Shetty ◽  
Anatoliy Kuznetsov ◽  
Qi Zhang ◽  
Phillip Christopher ◽  
...  
Keyword(s):  
Chemical Reactions ◽  
Active Site ◽  
Active Sites ◽  
Reaction Pathway ◽  
Control Strategies ◽  
Oscillation Amplitude ◽  
Catalytic Performance ◽  
Parallel Reaction ◽  
Resonance Theory ◽  
Static Conditions

Catalytic enhancement of chemical reactions via heterogeneous materials occurs through stabilization of transition states at designed active sites, but dramatically greater rate acceleration on that same active site is achieved when the surface intermediates oscillate in binding energy. The applied oscillation amplitude and frequency can accelerate reactions orders of magnitude above the catalytic rates of static systems, provided the active site dynamics are tuned to the natural frequencies of the surface chemistry. In this work, differences in the characteristics of parallel reactions are exploited via selective application of active site dynamics (0 < ΔU < 1.0 eV amplitude, 10<sup>-6</sup> < f < 10<sup>4</sup> Hz frequency) to control the extent of competing reactions occurring on the shared catalytic surface. Simulation of multiple parallel reaction systems with broad range of variation in chemical parameters revealed that parallel chemistries are highly tunable in selectivity between either pure product, even when specific products are not selectively produced under static conditions. Two mechanisms leading to dynamic selectivity control were identified: (i) surface thermodynamic control of one product species under strong binding conditions, or (ii) catalytic resonance of the kinetics of one reaction over the other. These dynamic parallel pathway control strategies applied to a host of chemical conditions indicate significant potential for improving the catalytic performance of many important industrial chemical reactions beyond their existing static performance.

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