2D covalent organic frameworks with built-in amide active sites for efficient heterogeneous catalysis

2019 ◽  
Vol 55 (96) ◽  
pp. 14538-14541 ◽  
Author(s):  
Yang Li ◽  
Weiben Chen ◽  
Ruidong Gao ◽  
Ziqiang Zhao ◽  
Ting Zhang ◽  
...  
Keyword(s):  
Heterogeneous Catalysis ◽  
Active Sites ◽  
Heterogeneous Catalysts ◽  
Knoevenagel Condensation ◽  
Covalent Organic Frameworks ◽  
Excellent Performance ◽  
Bottom Up

Two new amide functionalized covalent organic frameworks (COFs) were synthesized via a bottom-up strategy and used as heterogeneous catalysts toward Knoevenagel condensation with excellent performance.

An Efficient and Reusable Multifunctional Composite Magnetic Nanocatalyst for Knoevenagel Condensation

Synlett ◽  
2019 ◽  
Vol 30 (06) ◽  
pp. 699-702 ◽  
Author(s):  
Yu Hu ◽  
Nan Yao ◽  
Jin Tan ◽  
Yang Liu
Keyword(s):  
Active Sites ◽  
Heterogeneous Catalysts ◽  
Knoevenagel Condensation ◽  
Metal Organic Framework ◽  
Catalytic Performance ◽  
Significant Loss ◽  
Magnetic Nanocatalyst ◽  
Metal Organic ◽  
Nife2o4 Nanoparticles ◽  
Organic Framework

A range of multifunctional magnetic metal–organic framework nanomaterials consisting of various mass ratios of the metal–organic framework MIL-53(Fe) and magnetic SiO2@NiFe2O4 nanoparticles were designed, prepared, characterized, and evaluated as heterogeneous catalysts for the Knoevenagel condensation. The as-fabricated nanomaterials, especially the nanocatalyst MIL-53(Fe)@SiO2@NiFe2O4(1.0), showed good catalytic performance in the Knoevenagel condensation at room temperature as a result of synergistic interaction between the Lewis acid iron sites of MIL-53(Fe) and the active sites of the magnetic SiO2@NiFe2O4 nanoparticles. In addition, the heterogeneous catalyst was readily recovered and a recycling test showed that it could be reused for five times without significant loss of its catalytic activity, making it economical and environmentally friendly.

scholarly journals Designing Heterogeneous Catalysts for Renewable Catalysis Applications Using Metal Oxide Deposition

2019 ◽  
Vol 73 (9) ◽  
pp. 698-706
Author(s):  
Yuan-Peng Du ◽  
Jeremy S. Luterbacher
Keyword(s):  
Heterogeneous Catalysis ◽  
Metal Oxide ◽  
Active Sites ◽  
Heterogeneous Catalysts ◽  
Catalyst Deactivation ◽  
High Surface ◽  
Catalyst Stability ◽  
Synthetic Control ◽  
High Oxygen Content ◽  
Oxide Deposition

Heterogeneous catalysis has long been a workhorse for the chemical industry and will likely play a key role in the emerging area of renewable chemistry. However, renewable molecule streams pose unique challenges for heterogeneous catalysis due to their high oxygen content, frequent low volatility and the near constant presence of water. These constraints can often lead to the need for catalyst operation in harsh liquid phase conditions, which has compounded traditional catalyst deactivation issues. Oxygenated molecules are also frequently more reactive than petroleum-derived molecules, which creates a need for highly selective catalysts. Synthetic control over the nanostructured environment of catalytic active sites could facilitate the creation of both more stable and selective catalysts. In this review, we discuss the use of metal oxide deposition as an emerging strategy that can be used to synthesize and/or modify heterogeneous catalysts to introduce tailored nanostructures. Several important applications are reviewed, including the synthesis of high surface area mesoporous metal oxides, the enhancement of catalyst stability, and the improvement of catalyst selectivity.

Efficient heterogeneous catalysis by dual ligand Zn(ii)/Cd(ii) MOFs for the Knoevenagel condensation reaction: adaptable synthetic routes, characterization, crystal structures and luminescence studies

2018 ◽  
Vol 5 (10) ◽  
pp. 2630-2640 ◽  
Author(s):  
Bhavesh Parmar ◽  
Parth Patel ◽  
Vishnu Murali ◽  
Yadagiri Rachuri ◽  
Rukhsana I. Kureshy ◽  
...  
Keyword(s):  
Heterogeneous Catalysis ◽  
Crystal Structures ◽  
Heterogeneous Catalysts ◽  
Knoevenagel Condensation ◽  
Condensation Reaction ◽  
Knoevenagel Condensation Reaction ◽  
Synthetic Routes

Chemically stable Zn(ii)/Cd(ii) MOFs as a heterogeneous catalysts for Knoevenagel condensation.

scholarly journals Application of scanning electron microscopy in catalysis

2004 ◽  
pp. 67-77 ◽  
Author(s):  
Gizela Lomic ◽  
Erne Kis ◽  
Goran Boskovic ◽  
Radmila Marinkovic-Neducin
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Heterogeneous Catalysis ◽  
Active Sites ◽  
Heterogeneous Catalysts ◽  
Sem Analysis ◽  
Catalyst Preparation ◽  
Chemical Processes ◽  
Structured Materials ◽  
Scanning Electron

A short survey of various information obtained by scanning electron microscopy (SEM) in the investigation of heterogeneous catalysts and nano-structured materials have been presented. The capabilities of SEM analysis and its application in testing catalysts in different fields of heterogeneous catalysis are illustrated. The results encompass the proper way of catalyst preparation, the mechanism of catalyst active sites formation catalysts changes and catalyst degradation during their application in different chemical processes. Presented SEM pictures have been taken on a SEM JOEL ISM 35 over 25 years of studies in the field of heterogeneous catalysis.

scholarly journals Facile electron delivery from graphene template to ultrathin metal-organic layers for boosting CO2 photoreduction

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jia-Wei Wang ◽  
Li-Zhen Qiao ◽  
Hao-Dong Nie ◽  
Hai-Hua Huang ◽  
Yi Li ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Active Sites ◽  
Heterogeneous Catalysts ◽  
Metal Organic Framework ◽  
Ordered Structure ◽  
Uniform Thickness ◽  
Excellent Performance ◽  
Electron Mediator ◽  
Organic Layers ◽  
Metal Organic

AbstractMetal-organic layers with ordered structure and molecular tunability are of great potential as heterogeneous catalysts due to their readily accessible active sites. Herein, we demonstrate a facile template strategy to prepare metal-organic layers with a uniform thickness of three metal coordination layers (ca. 1.5 nm) with graphene oxide as both template and electron mediator. The resulting hybrid catalyst exhibits an excellent performance for CO2 photoreduction with a total CO yield of 3133 mmol g–1MOL (CO selectivity of 95%), ca. 34 times higher than that of bulky Co-based metal-organic framework. Systematic studies reveal that well-exposed active sites in metal-organic layers, and facile electron transfer between heterogeneous and homogeneous components mediated by graphene oxide, greatly contribute to its high activity. This work highlights a facile way for constructing ultrathin metal-organic layers and demonstrates charge transfer pathway between conductive template and catalyst for boosting photocatalysis.

scholarly journals X-ray spectroscopy for chemical and energy sciences: the case of heterogeneous catalysis

2014 ◽  
Vol 21 (5) ◽  
pp. 1084-1089 ◽  
Author(s):  
Anatoly I. Frenkel ◽  
Jeroen A. van Bokhoven
Keyword(s):  
Heterogeneous Catalysis ◽  
Active Site ◽  
Time Scale ◽  
Active Sites ◽  
Heterogeneous Catalysts ◽  
Time Range ◽  
Bond Breaking ◽  
Single Shot ◽  
X Rays ◽  
X Ray

Heterogeneous catalysis is the enabling technology for much of the current and future processes relevant for energy conversion and chemicals synthesis. The development of new materials and processes is greatly helped by the understanding of the catalytic process at the molecular level on the macro/micro-kinetic time scale and on that of the actual bond breaking and bond making. The performance of heterogeneous catalysts is inherently the average over the ensemble of active sites. Much development aims at unravelling the structure of the active site; however, in general, these methods yield the ensemble-average structure. A benefit of X-ray-based methods is the large penetration depth of the X-rays, enablingin situandoperandomeasurements. The potential of X-ray absorption and emission spectroscopy methods (XANES, EXAFS, HERFD, RIXS and HEROS) to directly measure the structure of the catalytically active site at the single nanoparticle level using nanometer beams at diffraction-limited storage ring sources is highlighted. The use of pump–probe schemes coupled with single-shot experiments will extend the time range from the micro/macro-kinetic time domain to the time scale of bond breaking and making.

scholarly journals A Ru-Complex Tethered to a N-Rich Covalent Triazine Framework for Tandem Aerobic Oxidation-Knoevenagel Condensation Reactions

Molecules ◽  
2021 ◽  
Vol 26 (4) ◽  
pp. 838
Author(s):  
Geert Watson ◽  
Parviz Gohari Derakhshandeh ◽  
Sara Abednatanzi ◽  
Johannes Schmidt ◽  
Karen Leus ◽  
...  
Keyword(s):  
Active Sites ◽  
Noble Metals ◽  
Heterogeneous Catalysts ◽  
Knoevenagel Condensation ◽  
Condensation Reaction ◽  
Aerobic Oxidation ◽  
Catalyst Support ◽  
Catalytic Performance ◽  
Condensation Reactions ◽  
Covalent Triazine Framework

Herein, a highly N-rich covalent triazine framework (CTF) is applied as support for a RuIII complex. The bipyridine sites within the CTF provide excellent anchoring points for the [Ru(acac)2(CH3CN)2]PF6 complex. The obtained robust RuIII@bipy-CTF material was applied for the selective tandem aerobic oxidation-Knoevenagel condensation reaction. The presented system shows a high catalytic performance (>80% conversion of alcohols to α, β-unsaturated nitriles) without the use of expensive noble metals. The bipy-CTF not only acts as the catalyst support but also provides the active sites for both aerobic oxidation and Knoevenagel condensation reactions. This work highlights a new perspective for the development of highly efficient and robust heterogeneous catalysts applying CTFs for cascade catalysis.

What catalysis needs from the electron microscopist

1988 ◽  
Vol 46 ◽  
pp. 694-695
Author(s):  
Alexis T. Bell
Keyword(s):  
Active Sites ◽  
Heterogeneous Catalysts ◽  
Catalyst Deactivation ◽  
Surface Composition ◽  
Internal Surface ◽  
Active Phase ◽  
Atomic Scale ◽  
Metal Catalyst ◽  
Internal Surface Area ◽  
Porous Support

Heterogeneous catalysts, used in industry for the production of fuels and chemicals, are microporous solids characterized by a high internal surface area. The catalyticly active sites may occur at the surface of the bulk solid or of small crystallites deposited on a porous support. An example of the former case would be a zeolite, and of the latter, a supported metal catalyst. Since the activity and selectivity of a catalyst are known to be a function of surface composition and structure, it is highly desirable to characterize catalyst surfaces with atomic scale resolution. Where the active phase is dispersed on a support, it is also important to know the dispersion of the deposited phase, as well as its structural and compositional uniformity, the latter characteristics being particularly important in the case of multicomponent catalysts. Knowledge of the pore size and shape is also important, since these can influence the transport of reactants and products through a catalyst and the dynamics of catalyst deactivation.

scholarly journals Microwaves and Heterogeneous Catalysis: A Review on Selected Catalytic Processes

Catalysts ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 246 ◽  
Author(s):  
Vincenzo Palma ◽  
Daniela Barba ◽  
Marta Cortese ◽  
Marco Martino ◽  
Simona Renda ◽  
...  
Keyword(s):  
Heterogeneous Catalysis ◽  
Energy Saving ◽  
Microwave Heating ◽  
Microwave Radiation ◽  
Heterogeneous Catalysts ◽  
Conventional Heating ◽  
Specific Effects ◽  
Natural Choice ◽  
Future Challenges ◽  
Catalyzed Reactions

Since the late 1980s, the scientific community has been attracted to microwave energy as an alternative method of heating, due to the advantages that this technology offers over conventional heating technologies. In fact, differently from these, the microwave heating mechanism is a volumetric process in which heat is generated within the material itself, and, consequently, it can be very rapid and selective. In this way, the microwave-susceptible material can absorb the energy embodied in the microwaves. Application of the microwave heating technique to a chemical process can lead to both a reduction in processing time as well as an increase in the production rate, which is obtained by enhancing the chemical reactions and results in energy saving. The synthesis and sintering of materials by means of microwave radiation has been used for more than 20 years, while, future challenges will be, among others, the development of processes that achieve lower greenhouse gas (e.g., CO2) emissions and discover novel energy-saving catalyzed reactions. A natural choice in such efforts would be the combination of catalysis and microwave radiation. The main aim of this review is to give an overview of microwave applications in the heterogeneous catalysis, including the preparation of catalysts, as well as explore some selected microwave assisted catalytic reactions. The review is divided into three principal topics: (i) introduction to microwave chemistry and microwave materials processing; (ii) description of the loss mechanisms and microwave-specific effects in heterogeneous catalysis; and (iii) applications of microwaves in some selected chemical processes, including the preparation of heterogeneous catalysts.

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