The power of non-hydrolytic sol-gel chemistry: A review

This review is devoted to non-hydrolytic sol-gel chemistry. During the last 25 years, non-hydrolytic sol-gel (NHSG) techniques were found to be attractive and versatile methods for the preparation of oxide materials. Compared to conventional hydrolytic approaches, the NHSG route allows reaction control at the atomic scale resulting in homogeneous and well defined products. Due to these features and the ability to design specific materials, the products of NHSG reactions have been used in many fields of application. The aim of this review is to present an overview of NHSG research in recent years with an emphasis on the syntheses of mixed oxides, silicates and phosphates. The first part of the review highlights well known condensation reactions with some deeper insights into their mechanism and also presents novel condensation reactions established in NHSG chemistry in recent years. In the second section we discuss porosity control and novel compositions of selected materials. In the last part, the applications of NHSG derived materials as heterogeneous catalysts and supports, luminescent materials and electrode materials in Li-ion batteries are described. © 2017 by the authors. Licensee MDPI, Basel, Switzerland.LO1504, MŠMT, Ministerstvo Školství, Mládeže a Tělovýchovy; LQ1601, MŠMT, Ministerstvo Školství, Mládeže a TělovýchovyMinistry of Education, Youth and Sports of the Czech Republic under the project CEITEC [LQ1601]; Ministry of Education, Youth and Sports of the Czech Republic under Program NPU I [LO1504]; Center for Direct Catalytic Conversion of Biomass to Biofuels (C3Bio); Energy Frontier Research Center - U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences [DESC0000997]; DOE BES [DE-FG02-01ER15259

Ag-Cu Colloid Synthesis: Bimetallic Nanoparticle Characterisation and Thermal Treatment

The Ag-Cu bimetallic colloidal nanoparticles (NPs) were prepared by solvothermal synthesis from metalloorganic precursors in a mixture of organic solvents. The nanoparticles were characterized by dynamic light scattering (DLS) and small angle X-ray scattering (SAXS). The properties of metallic core and organic shell of the nanoparticles were studied by direct inlet probe mass spectrometry (DIP/MS), Knudsen effusion mass spectrometry (KEMS), double-pulse laser-induced breakdown spectroscopy (DPLIBS), and differential scanning calorimetry (DSC). The transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used for particle characterization before and after thermal analysis. The experiment yielded results that were for AgCu nanoparticles for the first time. The detected liquidus temperature has been compared with the prediction obtained from calculation of the phase diagram of Ag-Cu nanoalloy. The experimental results show that of near-eutectic composition AgCu nanoparticles possess the fcc crystal lattice. Surprisingly, spinodal decomposition was not observed inside the AgCu nanoparticles at temperatures up to 230C. The depression of the eutectic AgCu melting point was calculated but not observed. The eutectic AgCu microparticles are formed before melting.Ag-Cu bimetalické koloidní nanočástice (NPs) byly připraveny solvotermální syntézou z metalických prekurzorů ve směsi organických rozpouštědel. Nanočástice byly charakterizovány metodami: DLS a SAXS. Vlastnosti kovového jádra a stabilizační obálky z organických látek byly studovány metodou přímého vstupu do hmotnostního spektrometru (DIP/MS), Knutsenovou hmotnostní spektrometrií (KEMS), double -pulse laserovou spektroskopií (DPLIBS) a diferenční skenovací kalorimetrií (DSC). Transmisní elektronová mikroskopie (TEM) a řádkovací elektronová mikroskopie (SEM) byly použity pro charakterizaci částic před a po termické analýze. Teplota likvidu zjištěna experimentálně byla srovnávána s predikcí fázového diagramu Ag-Cu nanoslitiny. Experimentální výsledky ukázaly téměř eutektické složení a fcc krystalovou mřížku AgCu NPs. Překvapivě, spinodální rozklad nanočástic nebyl pozorován při teplotách do 230C

Copper phosphinate complexes as molecular precursors for ethanol dehydrogenation catalysts

Nowadays, the production of acetaldehyde heavily relies on the petroleum industry. Developing new catalysts for the ethanol dehydrogenation process that could sustainably substitute current acetaldehyde production methods is highly desired. Among the ethanol dehydrogenation catalysts, copper-based materials have been intensively studied. Unfortunately, the Cu-based catalysts suffer from sintering and coking, which lead to rapid deactivation with time-on-stream. Phosphorus doping has been demonstrated to diminish coking in methanol dehydrogenation, fluid catalytic cracking, and ethanol-to-olefin reactions. This work reports a pioneering application of the well-characterized copper phosphinate complexes as molecular precursors for copper-based ethanol dehydrogenation catalysts enriched with phosphate groups (Cu-phosphate/SiO2). Three new catalysts (CuP-1, CuP-2, and CuP-3), prepared by the deposition of complexes {Cu(SAAP)}n (1), [Cu6(BSAAP)6] (2), and [Cu3(NAAP)3] (3) on the surface of commercial SiO2, calcination at 500 °C, and reduction in the stream of the forming gas 5% H2/N2 at 400 °C, exhibited unusual properties. First, the catalysts showed a rapid increase in catalytic activity. After reaching the maximum conversion, the catalyst started to deactivate. The unusual behavior could be explained by the presence of the phosphate phase, which made Cu2+ reduction more difficult. The phosphorus content gradually decreased during time-on-stream, copper was reduced, and the activity increased. The deactivation of the catalyst could be related to the copper diffusion processes. The most active CuP-1 catalyst reaches a maximum of 73% ethanol conversion and over 98% acetaldehyde selectivity at 325 °C and WHSV = 2.37 h-1CF BIC; European Regional Development Fund-Project “UP CIISB, (CZ.02.1.01/0.0/0.0/18_046/0015974, LM2018110); Grant Agency of Masaryk University, (CZ.02.01.01/00/22_008/0004572, MUNI/A/1298/2022, MUNI/J/0007/2021, QM4ST); Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT, (LM2018127, LM2023042, LM2023056, RP/CPS/2022/007); Grantová Agentura České Republiky, GA ČR, (GJ20-03636Y); Central European Institute of Technology, CEITECMEYS CR [LM2023042, LM2018127, CZ.02.1.01/0.0/0.0/18_046/0015974]; European Regional Development Fund-Project "UP CIISB" [LM2018110]; Czech Science Foundation [GJ20-03636Y]; Grant Agency of Masaryk University [MUNI/J/0007/2021, MUNI/A/1298/2022]; Quantum Materials for Applications in Sustainable Technologies (QM4ST) [CZ.02.01.01/00/22_008/0004572]; Ministry of Education, Youth and Sports of the Czech Republic [LM2023056]; Ministry of Education, Youth and Sports of the Czech Republic [RP/CPS/2022/007

Propylene metathesis over molybdenum silicate microspheres with dispersed active sites

In this work, we demonstrate that amorphous and porous molybdenum silicate microspheres are highly active catalysts for heterogeneous propylene metathesis. Homogeneous molybdenum silicate microspheres and aluminum-doped molybdenum silicate microspheres were synthesized via a nonaqueous condensation of a hybrid molybdenum biphenyldicarboxylate-based precursor solution with (3-aminopropyl)triethoxysilane. The as-prepared hybrid metallosilicate products were calcined at 500 °C to obtain amorphous and porous molybdenum silicate and aluminum-doped molybdenum silicate microspheres with highly dispersed molybdate species inserted into the silicate matrix. These catalysts contain mainly highly dispersed MoOx species, which possess high catalytic activity in heterogeneous propylene metathesis to ethylene and butene. Compared to conventional silica-supported MoOx catalysts prepared via incipient wetness impregnation (MoIWI), the microspheres with low Mo content (1.5-3.6 wt %) exhibited nearly 2 orders of magnitude higher steady-state propylene metathesis rates at 200 °C, approaching site time yields of 0.11 s-1CF CryoE; European Regional Development Fund-Project “UP CIISB, (CZ.02.1.01/0.0/0.0/18_046/0015974, LM2018110); Francqui Foundation; Grant Agency of Masaryk University, (MUNI/A/1298/2022, MUNI/J/0007/2021); U.S. Department of Energy, USDOE; Basic Energy Sciences, BES, (DE-SC0016214); Massachusetts Institute of Technology, MIT; Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT, (LM2023042, RP/CPS/2022/007); Grantová Agentura České Republiky, GA ČR, (GJ20-03636Y); Central European Institute of Technology, CEITECMinistry of Education, Youth, and Sports of the Czech Republic within the INTER-EXCELLENCE II program; Ministry of Education, Youth, and Sports of the Czech Republic [RP/CPS/2022/007]; U.S. Department of Energy, Office of Basic Energy Sciences [DE-SC0016214]; European Regional Development Fund-Project "UP CIISB" [CZ.02.1.01/0.0/0.0/18_046/0015974, LM2018110]; MEYS CR [GJ20-03636Y, LM2023042]; Czech Science Foundation; Grant Agency of Masaryk University [MUNI/J/0007/2021, MUNI/A/1298/2022]; Francqui Foundation for the Francqui Research Professor chai

Ethanol dehydrogenation over copper-silica catalysts: From sub-nanometer clusters to 15 nm large particles

Non-oxidative ethanol dehydrogenation is a renewable source of acetaldehyde and hydrogen. The reaction is often catalyzed by supported copper catalysts with high selectivity. The activity and long-term stability depend on many factors, including particle size, choice of support, doping, etc. Herein, we present four different synthetic pathways to prepare Cu/SiO2 catalysts (∼2.5 wt % Cu) with varying copper distribution: hydrolytic sol–gel (sub-nanometer clusters), dry impregnation (A̅ = 3.4 nm; σ = 0.9 nm and particles up to 32 nm), strong electrostatic adsorption (A̅ = 3.1 nm; σ = 0.6 nm), and solvothermal hot injection followed by Cu particle deposition (A̅ = 4.0 nm; σ = 0.8 nm). All materials were characterized by ICP-OES, XPS, N2 physisorption, STEM-EDS, XRD, RFC N2O, and H2-TPR and tested in ethanol dehydrogenation from 185 to 325 °C. The sample prepared by hydrolytic sol–gel exhibited high Cu dispersion and, accordingly, the highest catalytic activity. Its acetaldehyde productivity (2.79 g g–1 h–1 at 255 °C) outperforms most of the Cu-based catalysts reported in the literature, but it lacks stability and tends to deactivate over time. On the other hand, the sample prepared by simple and cost-effective dry impregnation, despite having Cu particles of various sizes, was still highly active (2.42 g g–1 h–1 acetaldehyde at 255 °C). Importantly, it was the most stable sample out of the studied materials. The characterization of the spent catalyst confirmed its exceptional properties: it showed the lowest extent of both coking and particle sintering.Web of Science1130109921098

Conductive silver films on paper prepared by atmospheric pressure argon plasma conversion of silver nitrate

Abstract We present a novel approach for deposition of metallic silver films from silver nitrate (AgNO₃) ink. The conversion of AgNO₃ is induced by argon plasma of the diffuse coplanar surface barrier discharge (DCSBD) generated at atmospheric pressure. The macroscopically homogeneous and diffuse plasma of high power density allows fast reduction of AgNO₃ into conductive metallic silver within two minutes. The process is carried out at temperatures below 70 °C and without the need for a complex vacuum chamber and is therefore highly suitable for deposition onto temperature-sensitive materials. In our study we used paper prepared from nanocellulose fibres, which offers mechanical flexibility, translucency and recyclability while having lower surface roughness and enhanced mechanical properties and thermal stability compared to regular paper. As a figure of merit, the resistivity of prepared films was measured. The X-ray photoelectron spectroscopy was used to study the conversion of AgNO₃ into metallic silver. Scanning electron microscopy revealed the morphology of the surface of the films giving insight on the nucleation and the growth process. The silver films prepared according to our methodology are an attractive possibility for applications in sensing devices or as conductive lines and other features in flexible electronics

Non-aqueous synthesis of homogeneous molybdenum silicate microspheres and their application as heterogeneous catalysts in olefin epoxidation and selective aniline oxidation

In this work, a novel synthesis of homogeneous molybdenum silicate spheres under non-aqueous conditions is presented. A preparation method is based on the condensation of molybdenum metal–organic framework-based precursor solution prepared via a microwave-assisted approach from bis(acetylacetonato)dioxomolybdenum and biphenyl-4,4′-dicarboxylic acid with 3-aminopropyltriethoxysilane under non-aqueous conditions. The as-prepared product was calcined at 500 °C to obtain amorphous and porous molybdenum silicate microspheres with homogeneously distributed molybdenum species within silicate matrix. The microspheres exhibit an average size of about 480 nm. This material was further studied as a heterogeneous catalyst for the epoxidation of olefins via the model catalytic epoxidation of cyclohexene with cumylhydroperoxide. High catalytic activity at the moderate temperature (65 °C) with the conversion of 86% after 2 h and the high selectivity to cyclohexene oxide has been achieved. In addition, molybdenum silicate microspheres exhibit catalytic activity and high selectivity in the oxidation of aniline to nitrosobenzene. © 2021 The Korean Society of Industrial and Engineering ChemistryRP/CPS/2020/006; Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT: LM2018110, LM2018127; Grantová Agentura České Republiky, GA ČR: GJ20-03636Y; Central European Institute of Technology, CEITEC; European Regional Development Fund, ERDF: CZ.1.05/2.1.00/19.040

Catalytic performance of micro-mesoporous zirconosilicates prepared by non-hydrolytic sol-gel in ethanol-acetaldehyde conversion to butadiene and related reactions

The open porosity and number of Lewis acid sites in metal silicates (M = Zr, Ta) have been reported as key factors enabling reaching high butadiene (BD) productivity from ethanol. However, some microporous zeolites recently displayed very high BD yields. To gain a deeper insight, we have applied non-hydrolytic sol-gel (NHSG) in the preparation of micro-mesoporous zirconosilicates. The porosity, structure, and acidity of these materials have been described and compared to a benchmark sample prepared by dry impregnation. The detailed characterization proved that NHSG preparation provided highly homogeneous Zr dispersion in silica leading to almost doubled Lewis acid site numbers and higher activity in ethanol-acetaldehyde conversion to BD, Meerwein-Ponndorf-Verley (MPV) reaction, and aldol condensation, in comparison to the catalyst prepared by dry impregnation. The selectivity and stability were similar for catalysts prepared by NHSG and dry impregnation. © 2023 Elsevier B.V.RP/CPS/2022/007; Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT: LM2018110, LM2018127; Grantová Agentura České Republiky, GA ČR: GJ20-03636Y; Central European Institute of Technology, CEITEC: CZ.02.1.01/0.0/0.0/18_046/0015586, LM201812

Microwave-assisted synthesis of platelet-like cobalt metal-organic framework, its transformation to porous layered cobalt-carbon nanocomposite discs and their utilization as anode materials in sodium-ion batteries

In this work a facile microwave-assisted synthesis of a platelet-like cobalt-based metal-organic framework (MOF) material is presented. This material was synthesized from cobalt(II) acetylacetonate and biphenyl-4,4′-dicarboxylic acid (Bpdc) in N,N’-dimethylformamide at 160°C. As-prepared Co-Bpdc MOF product with a platelet-like disc architecture was transformed by heat treatment in a nitrogen atmosphere at 800°C to porous cobalt-carbon nanocomposite discs. It is demonstrated that this synthetic strategy allows for obtaining magnetic microporous carbon layered discs with homogeneously incorporated metallic cobalt nanoparticles with a size of ca. 4 nm. The Co-C nanocomposite material was characterized by a variety of physico-chemical methods. It is shown that both Co-Bpdc MOF and Co-C nanocomposite were electrochemically active in sodium battery system as a material for the negative electrode. The high capacity retention over 80% and capacities over 200 mAh g–1 in the sodium-ion battery systems have been achieved. © 2019 Elsevier LtdMinistry of Education, Youth and Sports of the Czech Republic - Program NPU I [LO1504, LTT19001]; Operational Program Research and Development for Innovations; European Regional Development Fund (ERDF) within the framework of project CPS - strengthening research capacityEuropean Union (EU) [CZ.1.05/2.1.00/19.0409]; national budget of Czech Republic within the framework of project CPS - strengthening research capacity [CZ.1.05/2.1.00/19.0409]; BUT specific research programme [FEKT-S-17-4595

“Activated Borane” – A Porous Borane Cluster Polymer as an Efficient Lewis Acid-based Catalyst

Borane cluster based porous covalent networks, named activated borane (ActB), were prepared by co-thermolysis of decaborane(14) (nido-B10H14) and selected hydrocarbons (toluene – ActB-Tol, cyclohexane – ActB-cyHx, and n-hexane – ActB-nHx) under anaerobic conditions. These amorphous solid powders exhibit different textural and Lewis acid (LA) properties that vary depending on the nature of the constituent organic linker. For ActB-Tol, its LA strength even approaches that of the commonly-used molecular LA, B(C6F5)3. Most notably, ActBs can act as heterogeneous LA catalysts in hydrosilylation/deoxygenation reactions with various carbonyl substrates, as well as in the gas-phase dehydration of ethanol. These studies reveal the excellent potential of ActBs in catalytic applications, showing a) the possibility for tuning catalytic reaction outcomes (selectivity) in hydrosilylation/deoxygenation reactions by changing the material’s composition, and b) the very high activity toward ethanol dehydration that exceeds commonly used γ-Al2O3 by achieving a stable conversion of ~93 % with a selectivity for ethylene production of ~78 % during a 17 h continuous period on stream at 240°C