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12 pages, 3892 KiB

Open AccessArticle

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

by Geert Watson, Parviz Gohari Derakhshandeh, Sara Abednatanzi, Johannes Schmidt, Karen Leus and Pascal Van Der Voort

Molecules 2021, 26(4), 838; https://doi.org/10.3390/molecules26040838 - 5 Feb 2021

Cited by 10 | Viewed by 3188

Abstract

Herein, a highly N-rich covalent triazine framework (CTF) is applied as support for a Ru^III complex. The bipyridine sites within the CTF provide excellent anchoring points for the [Ru(acac)₂(CH₃CN)₂]PF₆ complex. The obtained robust Ru^III [...] Read more.

Herein, a highly N-rich covalent triazine framework (CTF) is applied as support for a Ru^III complex. The bipyridine sites within the CTF provide excellent anchoring points for the [Ru(acac)₂(CH₃CN)₂]PF₆ complex. The obtained robust Ru^III@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. Full article

(This article belongs to the Special Issue Nanomaterials for Catalysis)

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12 pages, 2200 KiB

Open AccessCommunication

Effects of Promoter on Structural and Surface Properties of Zirconium Oxide-Based Catalyst Materials

by Ekaterina S. Borovinskaya, Steffen Oswald and Wladimir Reschetilowski

Molecules 2020, 25(11), 2619; https://doi.org/10.3390/molecules25112619 - 4 Jun 2020

Cited by 4 | Viewed by 2373

Abstract

Ternary mixed oxide systems CuO/ZnO/ZrO₂ and CuO/NiO/ZrO₂ were synthesized by one-pot synthesis for a better understanding of the synthesis-property relationships of zirconium oxide-based catalyst materials. The prepared mixed oxide samples were analysed by a broad range of characterisation methods (XRD, N [...] Read more.

Ternary mixed oxide systems CuO/ZnO/ZrO₂ and CuO/NiO/ZrO₂ were synthesized by one-pot synthesis for a better understanding of the synthesis-property relationships of zirconium oxide-based catalyst materials. The prepared mixed oxide samples were analysed by a broad range of characterisation methods (XRD, N₂-physisorption, Temperature-Programmed Ammonia Desorption (TPAD), and XPS) to examine the structural and surface properties, as well as to identify the location of the potential catalytically active sites. By XPS analysis, it could be shown that a progressive enrichment of the surface composition with copper takes place by changing from ZnO to NiO as a promoter. Thus, by addition of the second component, not only electronic but also the geometric properties of active sites, i.e., copper species distribution within the catalyst surface, can be affected in a desired way. Full article

(This article belongs to the Special Issue Nanomaterials for Catalysis)

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12 pages, 1921 KiB

Open AccessArticle

Passivating Surface States on Water Splitting Cuprous Oxide Photocatalyst with Bismuth Decoration

by Yuhong Huang, Hongkuan Yuan and Hong Chen

Molecules 2019, 24(22), 4156; https://doi.org/10.3390/molecules24224156 - 16 Nov 2019

Cited by 3 | Viewed by 3288

Abstract

To enhance the visible light photocatalystic activity of Cu

_{2}

O(100) surface, we performed first-principles calculations on the structural, electronic and optical properties of a bismuth (Bi)-decorated Cu

_{2}

O(100) surface (Bi@Cu

_{2}

O(100)). It is shown that the Bi prefer to be [...] Read more.

To enhance the visible light photocatalystic activity of Cu

_{2}

O(100) surface, we performed first-principles calculations on the structural, electronic and optical properties of a bismuth (Bi)-decorated Cu

_{2}

O(100) surface (Bi@Cu

_{2}

O(100)). It is shown that the Bi prefer to be loaded to the hollow sites among four surface oxygen atoms and tend to individual dispersion instead of aggregating on the surface due to the lowest formation energy and larger distance between two Bi atoms at the surface than the Bi clusters; the coverage of around 0.25 monolayer Bi atoms can effectively eliminate the surface states and modify the band edges to satisfy the angular momentum selection rules for light excited transition of electrons, and the loaded Bi atoms contribute to the separation of photogenerated electron-holes. The relative positions between the band edges and the redox potentials are suitable for photocatalytic hydrogen production from the redox water, and moreover, the optical absorption spectrum indicates a positive response of the Bi

_{0.25}

@Cu

_{2}

O(100) to visible light, implying that the Bi

_{0.25}

@Cu

_{2}

O(100) is a promising visible light photocatalyst. Full article

(This article belongs to the Special Issue Nanomaterials for Catalysis)

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9 pages, 1390 KiB

Open AccessFeature PaperArticle

One-Pot Cu/TiO₂ Nanoparticles Synthesis for Trans-Ferulic Acid Conversion into Vanillin

by Paulette Gómez-López, Noelia Lázaro, Clemente G. Alvarado-Beltrán, Antonio Pineda, Alina M. Balu and Rafael Luque

Molecules 2019, 24(21), 3985; https://doi.org/10.3390/molecules24213985 - 4 Nov 2019

Cited by 11 | Viewed by 4347

Abstract

In this study, the co-synthesis of TiO₂ and Cu metallic nanoparticles obtained via one-pot cost-efficient hydrothermal process has been addressed. Different nanocatalysts with Cu contents were characterized by X-ray diffraction, nitrogen porosimetry, scanning electron microscopy, and transmission electron microscopy. The TiO₂ [...] Read more.

In this study, the co-synthesis of TiO₂ and Cu metallic nanoparticles obtained via one-pot cost-efficient hydrothermal process has been addressed. Different nanocatalysts with Cu contents were characterized by X-ray diffraction, nitrogen porosimetry, scanning electron microscopy, and transmission electron microscopy. The TiO₂ and Cu metallic nanoparticles were synthesized with copper loading up to one (Cu/Ti atomic ratio). Synthesized catalysts exhibited pore sizes in the mesoporous range and high surface areas above 150 m²/g. The particle size for TiO₂ presented a homogeneous distribution of approximately 8 nm, moreover, Cu nanoparticles varied from 12 to >100 nm depending on the metal loading. The nanostructured materials were successfully tested in the conversion of trans-ferulic acid into vanillin under sustainable conditions, achieving the best performance for 0.3 Cu/Ti atomic ratio (70% vanillin yield). Full article

(This article belongs to the Special Issue Nanomaterials for Catalysis)

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13 pages, 10709 KiB

Open AccessArticle

Palladium Supported on Porous Chitosan–Graphene Oxide Aerogels as Highly Efficient Catalysts for Hydrogen Generation from Formate

by Aicha Anouar, Nadia Katir, Abdelkrim El Kadib, Ana Primo and Hermenegildo García

Molecules 2019, 24(18), 3290; https://doi.org/10.3390/molecules24183290 - 10 Sep 2019

Cited by 23 | Viewed by 4038

Abstract

Adsorption of Pd(NH₃)₄²⁺ in preformed chitosan–graphene oxide (CS-GO) beads and their subsequent reduction with NaBH₄ afford well-dispersed, high dispersion (~21%) of uniformly sized Pd nanoparticles (~1.7 nm). The resulting Pd/CS-GO exhibits interesting catalytic activity for hydrogen generation by [...] Read more.

Adsorption of Pd(NH₃)₄²⁺ in preformed chitosan–graphene oxide (CS-GO) beads and their subsequent reduction with NaBH₄ afford well-dispersed, high dispersion (~21%) of uniformly sized Pd nanoparticles (~1.7 nm). The resulting Pd/CS-GO exhibits interesting catalytic activity for hydrogen generation by ammonium formate decomposition. The optimal GO proportion of 7 wt% allows reaching, at 60 °C, a turnover frequency above 2200 h⁻¹—being outstanding among the highest values reported for this process to date. Interestingly, no formation of CO or CH₄ was detected. The catalyst did not leach, although it underwent gradual deactivation, probably caused by the increase in the Pd average size that became over 3 nm after three uses. Our results are relevant in the context of efficient on-board hydrogen generation from liquid organic hydrogen carriers in transportation. Full article

(This article belongs to the Special Issue Nanomaterials for Catalysis)

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12 pages, 3518 KiB

Open AccessArticle

Solution Combustion Synthesis of Cr₂O₃ Nanoparticles and the Catalytic Performance for Dehydrofluorination of 1,1,1,3,3-Pentafluoropropane to 1,3,3,3-Tetrafluoropropene

by Haili Wang, Wenfeng Han, Xiliang Li, Bing Liu, Haodong Tang and Ying Li

Molecules 2019, 24(2), 361; https://doi.org/10.3390/molecules24020361 - 20 Jan 2019

Cited by 23 | Viewed by 4819

Abstract

Cr₂O₃ nanoparticles were prepared by solution combustion synthesis (SCS) with chromium nitrate as the precursor and glycine as the fuel. Commercial Cr₂O₃ and Cr₂O₃ prepared by a precipitation method were also included for comparison. [...] Read more.

Cr₂O₃ nanoparticles were prepared by solution combustion synthesis (SCS) with chromium nitrate as the precursor and glycine as the fuel. Commercial Cr₂O₃ and Cr₂O₃ prepared by a precipitation method were also included for comparison. The morphology, structure, acidity and particle size of fresh and spent Cr₂O₃ catalysts were investigated by techniques such as XRD, SEM, TEM, BET and NH₃-TPD. In addition, catalytic performance was evaluated for the dehydrofluorination of 1,1,1,3,3-pentafluoropropane (CF₃CH₂CHF₂, HFC-245fa) to 1,3,3,3-tetra-fluoropropene (CF₃CH=CHF, HFO-1234ze). The catalytic reaction rate of Cr₂O₃ prepared by SCS method is as high as 6 mmol/h/g, which is about 1.5 times and 2 times higher than that of precipitated Cr₂O₃ and commercial Cr₂O₃, respectively. The selectivity to HFO-1234ze for all the catalysts maintains at about 80%. Compared with commercial and precipitated Cr₂O₃, Cr₂O₃-SCS prepared by SCS possesses higher specific surface area and acid amount. Furthermore, significant change in the crystal size of Cr₂O₃ prepared by SCS after reaction was not detected, indicating high resistance to sintering. Full article

(This article belongs to the Special Issue Nanomaterials for Catalysis)

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Review

Jump to: Research

17 pages, 3581 KiB

Open AccessReview

Sustainable Carbon as Efficient Support for Metal-Based Nanocatalyst: Applications in Energy Harvesting and Storage

by Mireia Buaki-Sogó, Leire Zubizarreta, Marta García-Pellicer and Alfredo Quijano-López

Molecules 2020, 25(14), 3123; https://doi.org/10.3390/molecules25143123 - 8 Jul 2020

Cited by 12 | Viewed by 3551

Abstract

Sustainable activated carbon can be obtained from the pyrolysis/activation of biomass wastes coming from different origins. Carbon obtained in this way shows interesting properties, such as high surface area, electrical conductivity, thermal and chemical stability, and porosity. These characteristics among others, such as [...] Read more.

Sustainable activated carbon can be obtained from the pyrolysis/activation of biomass wastes coming from different origins. Carbon obtained in this way shows interesting properties, such as high surface area, electrical conductivity, thermal and chemical stability, and porosity. These characteristics among others, such as a tailored pore size distribution and the possibility of functionalization, lead to an increased use of activated carbons in catalysis. The use of activated carbons from biomass origins is a step forward in the development of more sustainable processes enhancing material recycling and reuse in the frame of a circular economy. In this article, a perspective of different heterogeneous catalysts based on sustainable activated carbon from biomass origins will be analyzed focusing on their properties and catalytic performance for determined energy-related applications. In this way, the article aims to give the reader a scope of the potential of these tailor-made sustainable materials as a support in heterogeneous catalysis and future developments needed to improve catalyst performance. The selected applications are those related with H₂ energy and the production of biomethane for energy through CO₂ methanation. Full article

(This article belongs to the Special Issue Nanomaterials for Catalysis)

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31 pages, 1050 KiB

Open AccessFeature PaperReview

Current Trends in the Application of Nanomaterials for the Removal of Emerging Micropollutants and Pathogens from Water

by Petros Kokkinos, Dionissios Mantzavinos and Danae Venieri

Molecules 2020, 25(9), 2016; https://doi.org/10.3390/molecules25092016 - 26 Apr 2020

Cited by 73 | Viewed by 6412

Abstract

Water resources contamination has a worldwide impact and is a cause of global concern. The need for provision of clean water is becoming more and more demanding. Nanotechnology may support effective strategies for the treatment, use and reuse of water and the development [...] Read more.

Water resources contamination has a worldwide impact and is a cause of global concern. The need for provision of clean water is becoming more and more demanding. Nanotechnology may support effective strategies for the treatment, use and reuse of water and the development of next-generation water supply systems. The excellent properties and effectiveness of nanomaterials make them particularly suitable for water/wastewater treatment. This review provides a comprehensive overview of the main categories of nanomaterials used in catalytic processes (carbon nanotubes/graphitic carbon nitride (CNT/g-C₃N₄) composites/graphene-based composites, metal oxides and composites, metal–organic framework and commercially available nanomaterials). These materials have found application in the removal of different categories of pollutants, including pharmaceutically active compounds, personal care products, organic micropollutants, as well as for the disinfection of bacterial, viral and protozoa microbial targets, in water and wastewater matrices. Apart from reviewing the characteristics and efficacy of the aforementioned nanoengineered materials for the removal of different pollutants, we have also recorded performance limitations issues (e.g., toxicity, operating conditions and reuse) for their practical application in water and wastewater treatment on large scale. Research efforts and continuous production are expected to support the development of eco-friendly, economic and efficient nanomaterials for real life applications in the near future. Full article

(This article belongs to the Special Issue Nanomaterials for Catalysis)

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23 pages, 5143 KiB

Open AccessFeature PaperReview

Encapsulation of Metal Nanoparticles within Metal–Organic Frameworks for the Reduction of Nitro Compounds

by Sergio Navalón, Mercedes Álvaro, Amarajothi Dhakshinamoorthy and Hermenegildo García

Molecules 2019, 24(17), 3050; https://doi.org/10.3390/molecules24173050 - 22 Aug 2019

Cited by 23 | Viewed by 6102

Abstract

Nitro group reduction is a reaction of a considerable importance for the preparation of bulk chemicals and in organic synthesis. There are reports in the literature showing that incorporation of metal nanoparticles (MNPs) inside metal–organic frameworks (MOFs) is a suitable strategy to develop [...] Read more.

Nitro group reduction is a reaction of a considerable importance for the preparation of bulk chemicals and in organic synthesis. There are reports in the literature showing that incorporation of metal nanoparticles (MNPs) inside metal–organic frameworks (MOFs) is a suitable strategy to develop catalysts for these reactions. Some of the examples reported in the literature have shown activity data confirming the superior performance of MNPs inside MOFs. In the present review, the existing literature reports have been grouped depending on whether these MNPs correspond to a single metal or they are alloys. The final section of this review summarizes the state of the art and forecasts future developments in the field. Full article

(This article belongs to the Special Issue Nanomaterials for Catalysis)

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