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This article is part of the themed collection: Chemical Communications HOT Articles 2023., Self-assembly of trans-{EuI2} nodes and ditopic ligands leads to isoreticular 2D frameworks featuring a rare, non-kagome Archimedean tessellation. The topology and intra-layer Eu(II)–Eu(II) antiferromagnetic interactions provide the prerequisites for geometrical spin frustration, which, due to the spin state degeneracy, is key for novel phenomena such as enhanced magnetic refrigeration., The authors acknowledge support from the VILLUM Foundation, the Independent Research Fund Denmark, ESS Lighthouses “SMART” and “Q-MAT”, MICINN (PID2021-124734OB-C21), DGA, Danscatt, and the ESRF (ID12 beamline).

Catalytic dehydrogenation of ethanol produces acetaldehyde, an important precursor for several value-added chemicals such as acetic acid and acetate esters. In this paper, we demonstrate that Zn-containing MFI zeolites are highly active and selective catalysts for this process. Furthermore, we show that their activity and selectivity depend on the chemical composition and preparation of the catalysts. The best catalyst comprises 5 wt% Zn on Silicalite-1 zeolite and results in 65.2% conversion and 94.5% selectivity towards acetaldehyde at 400 ℃. We relate the high selectivity to the absence of Brønsted acidic silanol groups, which suppresses the dehydration of ethanol into ethylene. Furthermore, while pure HZSM-5 and NaZSM-5 zeolites result in dehydration products, such as ethylene and diethyl ether, Zn on NaZSM-5 zeolite also results in acetaldehyde, which confirms that Zn is the active site. Finally, we compare different preparation procedures to show that several Zn-species may be active for the catalytic reaction.

Organoboron compounds are important building blocks in organic chemistry for a variety of key transformations in the production of compounds in the pharmaceutical and agricultural industries. Direct C–H borylation provides many advantages over more traditional transformation via halide groups that lead to stoichiometric waste. In the direct C(sp2)–H borylation of arenes, Ir-bipyridine systems have shown excellent performance. However, to make the formation of borylated products more benign and greener, transformations catalyzed by heterogeneous catalysts are appealing as they provide easier recovery and reuse of the catalyst. In this study, two different porous organic polymers (POPs) based on polystyrene-bearing bipyridine (bpy) ligands were synthesized. These POPs can, upon metal ligation in situ create an active catalyst that is capable of borylation twice per B2pin2 molecule. Our Ir systems were tested with different arenes, and a preliminary mechanistic investigation was performed. The system was recyclable for up to three consecutive recycles, albeit, the polymer backbone had indications of being borylated during the reaction.

Metal dichalcogenides are promising candidates for heterogeneous catalysis. Designing them as a double-shelled hollow nanostructure can enhance their performance owing to the high surface area prov...

The self-assembly of trivalent lanthanide ions with ditopic organic spacers results in the formation of complex tiling patterns that mimic the structural motifs of quasi-periodic 2D materials. The assembly of trans-{LnI2}+ nodes (Ln = Gd, Dy) with both closed-shell and anion radicals of 4,4'-bipyridine affords rare examples of Archimedean tessellations in a metal-organic framework. We furthermore demonstrate occurrence of sizable magnetic exchange interactions and slow relaxation of magnetization behaviour in a complex tessellation pattern. The implementation of Archimedean tessellations in lanthanide(III) coordination solids couriers a strategy to design elusive quasi-periodic metal-organic frameworks with inimitable magnetic properties

The development of novel cost-efficient, high-performing catalysts for CO2 methanation that are active at low temperatures can be optimized through the understanding of the reaction mechanism on different materials. A series of Ni-based catalysts supported on CeO2 and carbon/CeO2 composites was investigated, showing that Ni nanoparticles supported on a carbon/CeO2 composite with a 50:50 weight ratio and on pure CeO2 have excellent low-temperature activity and achieve up to 87% CO2 conversion with full selectivity towards CH4 at 370 °C. Importantly, meaningful insights on the reaction mechanism were gathered for the different types of materials by using the emerging ME−PSD−DRIFTS technique. The study of the rate of formation/consumption of the various intermediates showed that the CO2 methanation reaction follows a combination of the CO and formate pathways in the case of Ni on pure CeO2; however, in the case of Ni on the carbon/CeO2 composite, it follows only the formate pathway.

In this work, we investigated the catalytic effect of adding sulfur on Zn/ZSM-5 catalyst for direct conversion of ethane to aromatics. We show that the continuous addition of hydrogen sulfide (H2S) effectively stabilizes zinc, prevents coking and results in a highly selective and stable catalyst. Considering the high content of sulfur in shale gas resources, these results highlight the importance of investigating catalysts under realistic operating conditions.

The interzeolite transformation of a micronsized FAU zeolite to a nanosized CHA zeolite via alkali treatment is presented. The impact of the selection of the FAU zeolite starting material on the properties of the produced CHA zeolite was analyzed by XRD, ICP, SEM, TEM, N2 and CO2 adsorption, and in situ FT-IR. The analysis showed that the choice of starting FAU zeolite had a large impact on the chemical composition, size, morphology, and porosity of the produced CHA zeolite. The as prepared CHA samples show high capacity toward CO2 (4.26 mmol g-1) and it was demonstrated that the chemisorbed vs. physisorbed CO2 was controlled by varying the amount of alkali cations in the CHA zeolite. This journal is

Mechanochemical activation and steam-assisted interzeolite transformation offer a simple, fast and cost-efficient synthesis route to gmelinite (GME) zeolite. The use of faujasite (FAU) as the parent zeolite precursor facilitates the reaction and results in high yields of high-quality GME in less than 20 h under optimized conditions. The accessible porosity and amounts of stacking-faults were determined by N2 physisorption and XRD analysis, respectively. The results show that the quality of the prepared materials easily competes with GME zeolites synthesized by conventional hydrothermal synthesis, which encourages further research in this area. By changing the reaction parameters, the approach may also be used for the production of several other types of zeolites, including MOR, MFI and ANA.

This work shows that Ru nanoparticles supported on high surface area nano MgO is a highly active and selective catalyst for CO2 methanation, which is a promising method to store renewable energy and limit the emission of greenhouse gasses. We studied the effect of the Ru loading on MgO supports with different surface areas and compared the results to the corresponding Ni-based catalyst. Our results show that high surface area MgO containing 5 wt % Ru has the highest activity. This catalyst was stable for more than 50 h and resulted in 54 % conversion at 375 ◦C, which, under the given reaction conditions, corresponds to a site time yield of 520 molCH4 molRu− 1 h− 1. For comparison, the Ni-based catalyst only resulted in 45 % conversion at 450 ◦C with a low selectivity to CH4 (STY=263 molCH4 molNi − 1 h− 1). Furthermore, Ru on high surface area MgO catalyst was already active at low temperature of 250 ◦C due to chemisorption and activation of CO2 on the MgO support, which is promising for low-temperature CO2 methanation.

Carbonized zeolitic imidazolate frameworks (ZIFs) show potential as mesoporous heterogeneous catalysts with high metal loadings. ZIF-67 and ZIF-8 were used to create mono- and bimetallic CoCu particles supported on nitrogen-doped carbon via self-assembly in methanol at room temperature, followed by carbonization at 675 °C. A Cu precursor, Cu(NO3)2·2H2O, was impregnated into the ZIF-67 before carbonization to obtain bimetallic catalysts. Nanoalloy particles with different CoCu ratio were synthesized and characterized using XRD. The materials were further characterized using TEM, SEM, XRF and nitrogen physisorption. The different alloys were tested in conversion of cyclohexanone to the corresponding silyl ether. Complete conversion of cyclohexanone at 90 °C for 24 h were obtained. The catalyst Co99Cu1@NC gave a 60% increase in yield over a pure Co analogue.

Zeolite encapsulated metal nanoparticle catalysts hold great promise for several green and sustainable processes, ranging from environmental remediation to renewable energy and biomass conversion. In particular, the microporous zeolite framework keeps the nanoparticles in a firm grip that can control selectivity and prevent sintering at high temperatures. While progress in the synthesis of mesoporous zeolites continues, the encapsulation of metal nanoparticles remains a challenge that often requires complex procedures and expensive additives. Here, we report a general method to encapsulate both base and noble metal nanoparticles inside the internal voids of a compartmentalized mesoporous zeolite prepared by carbon templating and steam-assisted recrystallization. This results in a remarkable shell-like morphology that facilitates the formation of small metal nanoparticles upon simple impregnation and reduction. When the materials are applied in catalysis, we for instance demonstrate that zeolite encapsulated Ni nanoparticles are highly active, selective, and stable catalysts for CO2 methanation (49% conversion with 93% selectivity at 450 °C)—a reaction where catalysts often suffer from sintering due to the high reaction temperatures. While the introduction of Ni nanoparticles prior to the steam-assisted recrystallization results in the formation of inactive nickel phyllosilicates, noble metals such as Pt do not suffer from this limitation. Therefore, we also demonstrate the synthesis of an active catalyst prepared by the formation of Pt nanoparticles prior to the shell synthesis. We tested the zeolite encapsulated Pt nanoparticles for hydrogenation of linear and cyclic alkenes with increased chain length. The catalysts are active for hydrogenation of oct-1-ene (66% conversion) and cyclooctene (79% conversion) but inactive for the large cyclododecane (

Herein, ultra-stable Y zeolite (USY) catalysts modified with iron doping (1, 3, and 5 wt%) using FeCl3•6H2O as a precursor have been investigated. Detailed characterization of the synthesized catalysts was implemented through different analytical techniques including XRD, FTIR, UV–vis DRS, NH3-TPD, H2-TPR, N2 physisorption, EDX, FESEM, ICP-EOS, and XRF. The strong Lewis acidity of the precursor bestowed improved acidic properties to the parent USY besides a satisfactory partial dealumination of the zeolite structure. The optimal dispersion and structural properties were obtained in the case of 1 wt% doping of iron, which eventually led to superb olefin productivity (more than 56 wt%) in the upgrading of refinery fuel oil at mild operating conditions (atmospheric pressure and 550 °C). The optimum catalyst (1Fe/USY) has undergone further experiments with varying temperatures and space velocities to assess the apparent kinetics based on the Arrhenius model. A threefold increase in the space velocity (from 18.3 to 54.9 h–1) only slightly reduced the olefin productivity of the catalyst (to 47.1 wt%), which was still notable from a heavy feedstock. Reduction of the reaction temperature to 450 °C led to a decrease in the olefins yield to less than a half (23.3 wt%). Overall, the modified catalysts were capable of producing a high amount of light olefins from heavy fuel oil, with an orientation toward propylene as the most favored building block in the petrochemical industries.

Application of methanol as a coreactant in the atmospheric catalytic cracking of refinery fuel oil (abbreviated as the MFOCC process) over the H-ZSM-5 catalyst has been investigated for the first time with the aim to improve the olefin productivity of the heavy hydrocarbons and mitigate coke formation and catalyst deactivation. The results clearly proved the synergistic influence of cocracking in the MFOCC scenario. The integrated MFOCC process increased both light olefin (C2=–C4=) yield and gasoline (C5–C11) share of the liquid products to more than 36.7 and 78.7 wt %, respectively. Influence of contact time and temperature was also discussed.

Here we report a bifunctional catalyst comprised of Pd nanoparticles encapsulated in a solid acid mesoporous HZSM-5 zeolite for one-step synthesis of methyl isobutyl ketone (MIBK) from acetone at 150 °C and atmospheric pressure. The Pd nanoparticles are encapsulated in conventional HZSM-5 and mesoporous HZSM-5, prepared using a carbon template procedure. The nanoparticles are encapsulated using in situ encapsulation during the zeolite synthesis and post impregnation to investigate the effect of preparation procedure, zeolite confinement and distribution of nanoparticles. Additionally, the influence of Si to Al ratio of HZSM-5 zeolite and hence the effect of acidity was also analyzed. The prepared materials are characterized with various techniques including SEM, TEM, XRF, nitrogen physisorption and XRD among others. Of different materials, palladium nanoparticles encapsulated inside mesoporous zeolite via in situ encapsulation (Pd@MesoHZSM-5) were found to be the most active and highly selective (> 99%) for the formation of MIBK with a conversion of 37%. Moreover, the mesoporous zeolite structure increased the mass transfer and thereby enabling acetone to diffuse easily to the active sites excluding the formation of by-products.

A novel composite nanocatalyst (CNM) was fabricated and identified using XRD, NH3-TPD, FTIR, SEM, EDX, and N2 physisorption, and was further assessed for the catalytic cracking of a heavy feedstock to value-added chemicals, including light alkenes and liquid fuels. Multiple phases (MEL, MFI, CHA, and AlPO) and a moderately tuned acidity different from those in FCC and ZSM-5 catalysts were identified for the investigated catalyst. More than 80 wt% of the dry gas stream was occupied by light olefins (ethylene, propylene, and butenes) with the remarkable propylene-to-ethylene ratio of 2.18, surpassing the two benchmark ZSM-5 and FCC samples. Meanwhile, the total yield of gasoline and diesel fuel amounted to ˜46 wt%. The influence of operating conditions including reaction temperature and contact time on the catalytic performance of CNM was further investigated. The results indicated that a temperature of 823 K was most promising for obtaining notable yields of light olefins, particularly propylene, while at lower temperatures (723 K), the yield of liquid products became almost three times the gaseous species. The observed activation energy was about 36.7 kJ/mol with the CNM catalyst. Interestingly, by increasing the space velocity by a factor of five, the productivity to light olefins increased by 11.4% on a feed basis, indicating the high potential of the new catalyst for the catalytic conversion of heavy hydrocarbons to light olefins. An eight-lump kinetic model with varying orders of reaction successfully described the obtained results. The overall reaction order for the conversion of fuel oil on CNM was 1.47, whereas a negative reaction order for coke formation was observed in reasonable agreement with the phase separation theory.

Here we exploit zeolitic imidazolate frameworks ZIF-67 and ZIF-8 as precursors to obtain nanorattle catalysts with Co3O4 nanoparticles confined inside porous SiO2 shells. The method is simple and uses zeolitic imidazolate frameworks as both structural templates and sacrificial precursors. Nanorattle catalysts of different sizes and metal loadings are designed by varying the Co/Zn ratio in the zeolitic imidazolate frameworks. It is possible to obtain different metal loadings by introduction and removal of Zn using evaporation. Moreover, all produced catalysts contained small Co3O4 nanoparticles. Finally, the different catalysts are tested in CO oxidation to demonstrate the effect of variations as a proof of concept. Thus, the use of metal–organic frameworks to control properties in nanorattle catalysts proposes an alternative method for the preparation of novel catalysts and shows a new pathway for synthesis of nanostructured materials.

Herein, we report a study on the design of new palladium containing catalysts based on Ce- and Ca–Nb-mesocellular foam (MCF) supports for gas-phase conversion of acetone to methyl isobutyl ketone (MIBK). A comparison to other catalyst materials already described in the literature shows that the role of material structure (mesostructured cellular foams, hydroxyapatite or mesoporous aluminophosphate), acid-base character of the support, state of palladium species and the support metal dopants play important roles for the catalytic performance in the conversion of acetone to MIBK. Thus, the new catalytic system Pd/Ce-MCF with 11% of conversion and 94% of selectivity to MIBK (250 °C) is demonstrated to be more attractive in term of stability for the reaction over time than previously described in literature for Pd/hydroxyapatite.

Heterogeneous immobilized molecular catalysis has gained significant attention as a platform for creating more efficient and selective catalysts. A promising type of immobilized molecular catalysts are made from porous organic polymers (POPs) due to their high stability, porosity, and ability to mimic the catalytic activity and selectivity of homogeneous organometallic catalysts. These properties of the POP‐based systems make them very attractive as heterogeneous catalysts for hydrogenation of CO 2 to formate, where predominately homogeneous systems have been applied. In this study, five POPs were synthesized and assessed in the hydrogenation of CO 2 where the active catalysts were made in‐situ by mixing IrCl 3 and the POPs. One of the Ir/POP catalysts provided a turn‐over number (TON) >20,000, which is among the highest for POP‐based systems. Thorough characterization (CO 2 ‐ and N 2 ‐physisorption, TGA, CHN‐analysis, XRD, XPS, SEM, STEM and TEM) was performed. Notably, the developed Ir/POP system also showed catalytic activity for the decomposition of formic acid into H 2 enabling the use of formic acid as a renewable energy carrier.

The interzeolite transformation of a micronsized FAU zeolite to a nanosized CHA zeolite

Carbon supported Cu nanoparticles have a remarkable selectivity towards the catalytic dehydrogenation of bioethanol to acetaldehyde, which is an interesting alternative to the preparation from ethylene. In this work, we prepared a series of catalysts comprised of Cu nanoparticles supported on N‐doped ordered mesoporous carbons to investigate the catalytic effect of nitrogen content. Our study shows that N‐doping has a significant effect on the dispersion of Cu nanoparticles and that the highest content of N results in the highest activity. Furthermore, we show that the combined effects of strong metal‐support interactions and nano‐confinement is an effective method to prevent thermal and steam induced sintering. In contrast, we find no evidence that N‐doping activates the substrate or change the rate‐determining step. At 260 °C, the best catalyst results in >99% selectivity and a site‐time yield of 175 mol acetaldehyde /mol Cu /h. Under these conditions, the catalysts are stable for more than 12 h using an aqueous solution of 10% ethanol as feed.

The effect of introducing mesoporosity on the catalytic stability and selectivity of Zn‐containing ZSM‐5 catalysts was investigated for direct conversion of ethane to high‐value aromatics. Voids and mesopores were created in the zeolite (Si/Al=40) by selective desilication (recrystallization) using ammonium hydroxide and cetyltrimethylammonium bromide. Zinc was incorporated in the samples by incipient wetness impregnation to achieve different concentrations of 0.5, 1 and 5 wt%. The samples were characterized by XRD, N 2 physisorption, TGA, NH 3 ‐TPD, ICP‐OES, FTIR, 1 H, 27 Al and 29 Si solid‐state MAS NMR. The desilicated samples were compared to their parent analogues for ethane conversion to aromatics such as benzene, toluene and xylenes (BTX). All of the desilicated samples showed an improvement in BTX yield and catalytic stability. Thus, the presence of mesoporosity increases the accessibility to the active sites and facilitates the mass transfer of aromatic compounds, which result in higher performance and catalytic stability of the desilicated ZSM‐5 samples containing zinc.

An efficient supported ionic liquid catalyst is designed for condensation reaction of aldehydes and ketones. The Zr-based metal–organic framework (MOF), UiO-66-NH2, was initially functionalized with N,N′-dibutyl imidazolium ionic liquid (UiO-66-NH2-ILBr–), and then urea was attached to the ionic liquid (IL) to form a task-specific IL. Bromide was exchanged with tetrafluoroborate and the catalyst exhibits excellent performance for the synthesis of oximes. The ionic liquid/urea coupling showed a synergistic effect on the efficiency of the reaction. The supported catalyst system was recycled simply by filtration and reused for five times without significant decrease in its activity. The catalyst was characterized with PXRD, FTIR, TGA, XPS, BET, FE-SEM, EDS, elemental mapping and elemental analysis (CHN). Graphic Abstract: MOF/IL/urea catalytic system was used for the synthesis of oximes[Figure not available: see fulltext.]

Catalytic enantioselective C(sp3)–H functionalization remains a difficult task, even more so using heterogeneous catalysts. Here, we report the first example of enantioselective C(sp3)–H functionalization using a chiral porous organic polymer as the heterogeneous catalyst. The catalyst consists of a polystyrene-incorporating chiral phosphoramidite coordinated to palladium, and it provides up to 86% ee for the challenging enantioselective C(sp3)–H functionalization of a range of 3-arylpropanamides. The swelling properties of the catalyst allow for quasi-homogeneous behavior in the reaction mixture while still enabling easy catalyst separation from the reaction medium and reuse. Thorough characterization of the fresh porous organic polymer and recycled catalyst material by 31P CP/MAS NMR, 13C–1H CP/MAS NMR, X-ray diffraction, TEM, STEM, EDX–SEM, ICP, and XRF in combination with modifications to the reaction conditions for the recycled catalyst material reveals potential explanations for catalyst deactivation.

A pre-catalyst, consisting of RuO2 nanoparticles and clusters anchored on TpBD-Me2 COF, was synthesized. During catalytic formic acid dehydrogenation, RuO2 undergoes in situ reduction to metallic Ru, forming an active and selective catalyst, which outperforms the commercial Ru–C catalyst. The chemical structure of the COF supporting material is maintained during stability testing.

Coke formation is a major reason in deactivation of acidic zeolite catalysts in industrial processes such as methanol to hydrocarbons conversion. Protecting the surface of acidic zeolite with an inert porous shell can greatly hinder the coke formation on the surface, and hence boost the lifetime of the catalyst. In this work, a solid-state steam-assisted method for synthesis of such optimized protective shell (silicate-1, ~15 nm thickness) is designed. This general and simple protocol can be applied to acidic zeolite catalysts to improve their catalytic lifetime. The silicalite-1 shell is synthesized on mesoporous ZSM-5 zeolite to explore its catalytic activity in methanol to hydrocarbons conversion. XPS and TEM analysis confirm the coverage of mesoporous zeolite crystals by non-acidic shell. In addition, nitrogen physisorption shows the accessibility of mesoporous ZSM-5 via microporous silicalite-1 network. Applying this protective shell increases the lifetime of the catalyst by 100% and its conversion capacity by 130%, in comparison to mesoporous ZSM-5 without the shell. The controlled formation of thin layer of microporous silicalite-1 around mesoporous ZSM-5 crystals (without growth of individual silicalite-1) accounts for enhanced catalytic improvement.

We report a polystyrene‐incorporated chiral nickel(II)‐bisdiamine complex, which is accessible on gram‐scale. This metal complex functions as a heterogeneous catalyst for the enantioselective Michael addition between malonates and aliphatic nitroalkenes, and it provides yields and enantioselectivities on par with homogeneous catalysts. Good functional group tolerance is reported for this reaction. Upon recycling, the catalyst achieves significantly higher TONs than previously reported. We demonstrate scalability to multigram‐scale, compatibility with continuous flow production (4.43 gram), and application to the synthesis of the blockbuster drug Pregabalin. Finally, a new tandem reaction is disclosed.

Selective hydroxylation of benzene is a felicitous strategy for the production of phenol that is deemed an alternative route for conventional processes. Thus, the development of a durable and highly efficient catalyst for the selective hydroxylation of benzene should be the key topic. In this work, FeOCl was prepared by chemical vapor transition method and characterized using various techniques including XRD, TEM, Raman spectroscopy, N2 adsorption–desorption, DLS and TGA. The prepared FeOCl was applied as heterogeneous catalyst in benzene hydroxylation and the reaction conditions were optimized. The acquired data manifested that FeOCl has shown superiority over the other reported catalysts utilized in benzene hydroxylation. The superiority of FeOCl is attributed to the facile self-redox potential of FeOCl and its exceptional ability for the production of an overwhelming amount of hydroxyl radicals in a short period of time. The catalyst recovery and reusing test showed that FeOCl is able to endure the harsh conditions of benzene hydroxylation for four runs. The mechanism of benzene hydroxylation using FeOCl as a catalyst in the presence of hydrogen peroxide as an oxidant was also illustrated.

Encapsulation of Pt nanoparticles (1‐2 nm) in the small pore zeolite chabazite (CHA) was achieved by a seed‐ and structuredirecting agent‐free interzeolite transformation from zeolite Y (FAU). Prior to the transformation, the Pt nanoparticles were encapsulated in the commercially available large pore zeolite H‐Y by simple incipient wetness impregnation. The H‐Y was then converted into CHA in a solution of KOH under hydrothermal conditions at 95 °C. All catalysts were characterized by XRD, N2‐physisorption, H2‐chemisorption, TEM and XPS and their catalytic activity were tested in CO oxidation. Although the catalytic activity of the encapsulated Pt nanoparticles decreased over time, it still remained more active than a reference catalyst prepared by impregnation. The thermal stability of the catalysts was investigated after calcination at 400 °C for 18 hours. Compared to the other catalysts, the encapsulated Pt nanoparticles only resulted in a small decrease in catalytic activity.

Porous organic polymers (POPs) containing catalytically active mononuclear metal centers can bridge the gap between homogeneous and heterogeneous catalysis. These materials offer catalysts with straightforward control over the active site analogously to homogeneous organometallic catalysts; however, just like classical heterogeneous catalysts, they are easy to separate from reaction mixtures and recycle. The main objective of this review is to provide an overview of the different types of reactions for synthetic organic chemistry where metal-POP catalysts have been utilized. In addition, a brief description of different synthesis strategies for accessing metal-POPs is included. We also propose a uniform naming system for metal-POP catalysts. Finally, current challenges, which could advance the field and facilitate industrial application, are discussed.

Efficient methanation of CO2 relies on the development of more selective and stable heterogeneous catalysts. Herein, we present a simple and effective method to encapsulate Ni nanoparticles in zeolite silicalite‐1. In this method, the zeolite is modified by selective desilication, which creates intraparticle voids and mesopores that facilitate the formation of small and well‐dispersed nanoparticles upon impregnation and reduction. Transmission electron microscopy and X‐ray photoelectron spectroscopy analyses confirm that a significant part of the Ni nanoparticles are situated inside the zeolite rather than on the outer surface. The encapsulation results in increased metal dispersion and, consequently, high catalytic activity for CO2 methanation. With a gas hourly space velocity of 60 000 mL gcatalyst−1 h−1 and H2/CO2=4, the zeolite‐encapsulated Ni nanoparticles result in 60 % conversion at 450 °C, which corresponds to a site‐time yield of approximately 304 molurn:x-wiley:18673880:media:cctc201701946:cctc201701946-math-0001 molNi−1 h−1. The encapsulated Ni nanoparticles show no change in activity or selectivity after 50 h of operation, although postcatalysis characterization reveals some particle migration.

The silylative pinacol coupling of arylaldehydes catalyzed by aneasily accessible, heterogeneous base-metal catalyst is demonstrated. Instead of using the classical combination of catalyst, stoichiometric metal reductants, and chlorosilanes, the developed reaction only requires the use of a catalyst and a hydrosilane, which serves as both reductant and silylating agent. A rare mechanistic investigation in this field focusing on the organic reactants was undertaken using various techniques including experimental rate orders, kinetic isotope effect, radical scavengers, and stoichiometric tests. The obtained results provided evidence for a reaction mechanism which is different from the classical pinacol coupling pathway. We propose that the heterogeneous catalyst facilitates easy access to silyl radicals, thereby circumventing the usual need for explosive initiators to access these species. In addition, leaching tests and recycling of the catalyst were performed, clearly supporting the heterogeneous nature of the catalyst.

Olefin migration in allylarenes is typically performed with precious-metal-based homogeneous catalysts. In contrast, very limited progress has been made with the use of cheap, Earth-abundant base metals as heterogeneous catalysts for these transformations—in spite of the obvious economic and environmental advantages. Herein, we report on the use of an easily prepared heterogeneous catalyst material for the migration of olefins, in particular, for allylarenes. The catalyst material consists of nickel/cobalt alloy nanoparticles encapsulated in nitrogen-doped carbon shells. The encapsulated nanoparticles are stable in air and are easily collected by centrifugation, filtration, or magnetic separation. Furthermore, we demonstrate that the catalysts can be reused several times and provide continuously high yields of the olefin-migration product.

Aerobic oxidation of allylic alcohols to methyl esters using gold nanoparticles supported on different metal oxide carriers has been performed successfully under mild conditions (room temperature, 0.1 MPa O2) without significant loss of catalytic activity. The effects of different reaction parameters are studied to find the suitable reaction conditions. All catalysts are characterised by XRD, XRF and TEM. Among these catalysts, Au/TiO2 showed the most efficient catalytic activity towards the selective oxidation of allylic alcohols to the corresponding esters. Moreover, the same Au/TiO2 catalyst is used to optimize all the reaction parameters including the significance of the base to promote the reaction. Due to the mild reaction conditions and high conversions as well as selectivity, the utilization of titania-supported gold nanoparticle catalysts represents a benign reaction protocol to synthesize methyl esters from allylic alcohols.

Formic acid has recently attracted considerable attention as a safe and convenient source of hydrogen for sustainable chemical synthesis and renewable energy storage. Here, we show that silica encapsulated and amine functionalised gold nanoparticles are highly active catalysts for the production of hydrogen by vapour phase decomposition of formic acid. The core-shell catalysts are prepared in a reverse micelle system that makes it possible to control the size of the Au nanoparticles and the thickness of the SiO 2 shells, which has a large impact on the catalytic activity. The smallest gold nanoparticles are 2.2 ± 0.3 nm in diameter and have a turnover frequency (TOF) of up to 958 h −1 at a temperature of 130 °C. Based on detailed in situ ATR-FTIR studies and results from kinetic isotope labelling experiments we propose that the active site is a low-coordinated and amine functionalised Au atom, while H-assisted formate decomposition into CO 2 and H 2 is the rate limiting step.

The introduction of efficient and selective catalytic methods for aerobic oxidation of lignin and lignin model compounds to aromatics can extend the role of lignin applications in biorefineries. The current study focussed on the catalytic oxidative transformation of guaiacyl glycerol--guaiacyl ether (GGGE)&ndash, a -O-4 lignin model compound to produce basic aromatic compounds (guaiacol, vanillin and vanillic acid) using metal-supported catalysts. Ru/Al2O3, prepared with ruthenium(IV) oxide hydrate, showed the highest yields of the desired products (60%) in acetonitrile in a batch reactor at 160 C and 5-bar of 20% oxygen in argon. Alternative catalysts containing other transition metals (Ag, Fe, Mn, Co and Cu) supported on alumina, and ruthenium catalysts based on alternative supports (silica, spinel, HY zeolite and zirconia) gave significantly lower activities compared to Ru/Al2O3 at identical reaction conditions. Moreover, the Ru/Al2O3 catalyst was successfully reused in five consecutive reaction runs with only a minor decrease in catalytic performance.

Nanostructured carbons with different pore geometries are prepared with a liquid-free nanocasting method. The method uses gases instead of liquid to disperse carbon precursors, leach templates, and remove impurities, minimizing synthetic procedures and the use of chemicals. The method is universal and demonstrated by the synthesis of 12 different porous carbons with various template sources. The effects of pore geometries in catalysis can be isolated and investigated. Two of the resulted materials with different pore geometries are studied as supports for Ru clusters in the hydrogenolysis of 5-hydroxymethylfurfural (HMF) and electrochemical hydrogen evolution (HER). The porous carbon-supported Ru catalysts outperform commercial ones in both reactions. It was found that Ru on bottleneck pore carbon shows a highest yield in hydrogenolysis of HMF to 2,5-dimethylfuran (DMF) due to a better confinement effect. A wide temperature operation window from 110 to 140 °C, with over 75% yield and 98% selectivity of DMF, has been achieved. Tubular pores enable fast charge transfer in electrochemical HER, requiring only 16 mV overpotential to reach current density of 10 mA·cm

The α-alkylation of ketones with alcohols represents a green strategy for the formation of crucial carbon–carbon bonds since it only produces water as byproduct. In terms of reaction mechanism, the evidence for homogeneous catalysis supports a catalytic hydrogen-borrowing pathway; however, the reaction mechanism has not been investigated for heterogeneous Pd/C catalysts. Here, we report an improved method for α-alkylation of ketones with alcohols using commercially available Pd/C, ubiquitous in organic synthesis labs, as catalyst. The reaction conditions are mild compared to state-of-the-art for both homo- and heterogeneous catalysts, and the developed conditions produces quantitative yields for most ketones and alcohols. A hot filtration experiment and recycling of the catalyst supports the heterogeneous nature of catalysis. Importantly, the reaction mechanism is studied for the first time by a combination of stoichiometric experiments and kinetic analyses by in-situ IR (React-IR).

The direct conversion of ethane to higher-valued petrochemical feedstock such as benzene, toluene and xylenes (BTX) has become more economically attractive because of the recent shale gas revolution. The selectivity towards BTX and catalyst deactivation represent significant technical challenges in this process. In this work, we synthesized a series of bi-functional Pt on acidic ZSM-5 catalysts to investigate the effect of platinum nanoparticle distribution and location on selectivity and deactivation. The best catalyst was Pt encapsulated in desilicated ZSM-5 that remained stable after 15 h of reaction resulting in 60% higher conversion and 75% higher BTX selectivity than Pt supported on conventional acidic ZSM-5 zeolite.

Catalytic treating of biomass fast pyrolysis vapors offers a promising route to convert many different types of lignocellulosic biomass into biofuels. Considerable research efforts have focused on using zeolite catalysts, especially the microporous HZSM-5 zeolite. Unfortunately, the zeolite’s initial high activity in forming coke and light gases reduces the overall oil yield. In this contribution, we synthesized conventional HZSM-5 zeolite, mesoporous HZSM-5 zeolite, and a core-shell catalyst consisting of mesoporous HZSM-5 zeolite coated with a thin layer (2 and Ar physisorption, temperature programmed desorption of ammonia (NH3-TPD), diffuse reflectance infrared fourier transform spectroscopy (DRIFT) spectra, and 27Al nuclear magnetic resonance (NMR). The catalysts were tested in a tandem micro-pyrolyzer system for deoxygenation of wheat straw derived fast pyrolysis vapors in a downstream catalytic fixed bed reactor and the quantitative product analysis was performed with GC-MS/FID/TCD and TGA-MS. The change in yields of different product groups was monitored during catalyst deactivation for an increasing number of pyrolysis vapor pulses and the cumulative carbon recoveries of all product streams (char, vapors, gas, and coke) were compared at different biomass-to-catalyst ratios (∼4 and ∼1) for catalyst loadings of 2 and 8 mg, respectively. In addition, the yields were compared for the same number of zeolitic acid sites. Even though the coking propensity was highest for the mesoporous HZSM-5 (5.1% carbon recovery of fed biomass at B:C = 1), it showed improved conversion of oxygenates (wt% O of vapors = 15) and a higher tolerance towards deactivation by coking compared to the conventional HZSM-5 (wt% O of vapors = 20). Coating of mesoporous HZSM-5 with silicalite-1 reduced the number of acid sites per mass of catalyst by ∼20%, which is attributed to the addition of the inert silicalite-1 layer and passivation of the external acid sites of the mesoporous HZSM-5. Compared to mesoporous HZSM-5, the added silicalite-1 shell reduced the coke yield by 43% (from 5.1 to 2.9 wt% of fed biomass carbon) for the same catalyst mass and by 8% (4.7 wt% of fed biomass carbon) for the same total number of acid sites. Furthermore, the tolerance towards deactivation observed for the mesoporous HZSM-5 core was largely preserved—especially for conversion of small oxygenates like acids, alcohols and aldehydes, resulting in vapors with 14 wt% O.

In this article, we report an approach to synthesize alloy Co-Ni nanoparticles encapsulated in carbon by utilization of the MOF, ZIF-67, as a sacrificial template. The alloy CoNi materials are synthesized by incipient wetness impregnation of cobalt-containing ZIF-67 with nickel(ii) nitrate followed by carbonization. The formation of alloy nanoparticles was verified by XRD and TEM analysis showed that they are distributed evenly throughout the entire material. The carbon encapsulating the alloy nanoparticles is N-doped and graphitic according to XPS analysis. Further characterization by ICP, N-2-physisorption, and SEM imaging was also performed. The CoNi materials exhibited promising activity in the catalytic hydrosilylation of ketones. A carbonization temperature of 800 degrees C provided the best catalyst for this transformation. The reaction conditions were optimized, different silanes tested, a time study conducted, and the heterogeneity of the catalysis assessed with different tests. Finally, a substrate scope of various ketones was examined.

In this work, we exploited zeolitic imidazolate framework ZIF-67 as a sacrificial precursor to prepare Co nanoparticles supported on nanoporous nitrogen-doped carbon. The catalysts were tested for hydrolytic dehydrogenation of ammonia borane and the size of the Co nanoparticles and the structural features of the carbon support were shown to have a large effect on the catalytic activity. Furthermore, we investigated the effect of adding Zn to the catalyst precursor (ZIF-67/8). The highest catalytic activity was obtained for ZIF-67/8 with a molar ratio of Co/Zn = 1, which was carbonized at 900 °C to remove Zn by evaporation. At room temperature, this catalyst resulted in a turnover frequency of 7.6 mol H2 per mol Co min−1 and an apparent activation energy of Ea = 44.9 kJ mol−1. The turnover frequency was further increased to 12.7 min−1 in 0.1 M NaOH.

Lignin is a complex polymeric molecule constituting various linkages between aromatic moieties. Typically, the β-O-4 linkage accounts for more than half of the linkage structures present in lignin. The current study focuses on the oxidative transformation of veratryl alcohol (VA)—a compound that can be formed by cleavage of β-O-4 linkages in lignin—to veratraldehyde (VAld) with air using ruthenium supported on γ-alumina or silica as catalyst with water or methanol as solvent in a batch reactor. Ru/Al2O3, prepared with ruthenium(IV)oxide hydrate showed superior catalytic activity, yielding 89 % VAld in water at 160 °C with 5 bar air pressure after 8 h of reaction. Prolonged reaction time led to significant formation of the decarbonylated product veratrol from VAld. When the reaction was completed under 20 bars of argon in methanol instead of water, the methyl ether of VA (i.e. 1,2-dimethoxy-4-(methoxymethyl)benzene) prevailed, indicating that methanol protected the hydroxyl group in VA from being oxidized to VAld. Catalysts containing alternative transition metals (Mn, Co, Cu and Ag) supported on Al2O3 gave significantly lower activities compared to Ru/Al2O3 under identical reaction conditions. The Ru/Al2O3 catalyst was reused in three consecutive reaction runs in water, but a decrease in VAld yield was obtained after the third cycle possibly due to leaching of Ru from the support.

A range of solid and liquid catalysts containing bicarbonate anions were synthesised and tested for the epoxidation of alkenes with aqueous hydrogen peroxide. The combination of bicarbonate anions and quaternary ammonium cations opens up for new catalytic systems that can help to overcome challenges with catalyst separation and reuse.

Reversible absorption of the flue gas components CO2, NO, NO2 and SO2 has been tested for different ionic liquids (ILs) at different temperatures and flue gas compositions where porous, high surface area carriers have been applied as supports for the ionic liquids to obtain Supported Ionic Liquid-Phase (SILP) absorber materials. The use of solid SILP absorbers with selected ILs were found to significantly improve the absorption capacity and sorption dynamics at low flue gas concentration, thus making the applicability of ILs viable in technical, continuous flow processes for flue gas cleaning. The results show that CO2, NO and SO2 can be reversible and selective absorbed using different ILs and that Supported Ionic Liquid-Phase (SILP) absorbers are promising materials for industrial flue gas cleaning. Absorption/desorption dynamics can be tuned by temperature, pressure and gas concentration.