Catalysis: Homogeneous and Heterogeneous

Surface geometry at the atomic level is an important factor related to the activity of a catalytic site. It is important to identify sites with high activity to comprehend the performance of a given catalyst. In this work, it is proposed that the optimal surface for a given reaction step should satisfy the condition $\frac{\partial E}{\partial x_i}{|}_{TS}=0$, where E is the transition state energy and x_i is any variable characterizing the surface. Taking three elementary steps as examples, it is shown that the optimal site found by this method has significantly reduced TS (transition state) energy compared with facets commonly applied in previous studies, and, thus, it can be several orders more active. The method provides an insight into the geometric impact of catalysis, gives a blueprint for an ideal catalyst surface structure, and, thus, provides guidance for catalyst development. Full article

Chiral hydroxamic acid (HA) and bis-hydroxamic acid (BHA) ligands have made significant contributions to the field of asymmetric synthesis, particularly in the synthesis of natural products. These ligands possess unique molecular structures that allow for exceptional stereochemical control, leading to their widespread use in catalytic systems. This review highlights the advancements made in asymmetric synthesis using chiral hydroxamic acid and bis-hydroxamic acid ligands and their impact on the synthesis of complex natural products. This discussion encompasses their role in enantioselective C–C bond formation, the functionalization of C–H bonds, the asymmetric transformations involving heteroatoms, and their application in the total synthesis of natural products. The versatility and efficiency of chiral hydroxamic acid ligands and bis-hydroxamic acid ligands make them invaluable tools for synthetic chemists working towards the efficient and selective synthesis of natural products. This review provides a comprehensive overview of their contributions, showcasing their potential to expand the boundaries of chemical synthesis and access the diverse array of natural product scaffolds. Full article

The oxygen evolution reaction (OER) is a key half-reaction in electrocatalytic water splitting. Large-scale water electrolysis is hampered by commercial noble-metal-based OER electrocatalysts owing to their high cost. To address these issues, we present a facile, one-pot, room-temperature co-precipitation approach to quickly synthesize carbon-nanotube-interconnected amorphous NiFe-layered double hydroxides (NiFe-LDH@CNT) as cost-effective, efficient, and stable OER electrocatalysts. The hybrid catalyst NiFe-LDH@CNT delivered outstanding OER activity with a low onset overpotential of 255 mV and a small Tafel slope of 51.36 mV dec⁻¹, as well as outstanding long-term stability. The high catalytic capability of NiFe-LDH@CNT is associated with the synergistic effects of its room-temperature synthesized amorphous structure, bi-metallic modulation, and conductive CNT skeleton. The room-temperature synthesis can not only offer economic feasibility, but can also allow amorphous NiFe-LDH to be obtained without crystalline boundaries, facilitating long-term stability during the OER process. The bi-metallic nature of NiFe-LDH guarantees a modified electronic structure, providing additional catalytic sites. Simultaneously, the highly conductive CNT network fosters a nanoporous structure, facilitating electron transfer and O₂ release and enriching catalytic sites. This study introduces an innovative approach to purposefully design nanoarchitecture and easily synthesize amorphous transition-metal-based OER catalysts, ensuring their cost effectiveness, production efficiency, and long-term stability. Full article

The preparation of a new class of six bifunctional thiourea organocatalysts having a D-fructose scaffold and a primary amino group was demonstrated. In the present study, the novel organocatalysts exhibited excellent enantio- and moderate diastereoselectivities in the asymmetric Michael addition of aliphatic ketones and 1,3-diketone to substituted nitroolefins at room temperature. In addition, the direct asymmetric aldol reaction between cyclic aliphatic ketone and aromatic aldehydes was also studied in the presence of the saccharide-thiourea organocatalysts giving excellent yield with moderate enantioselectivity. Full article

Recently, sterically demanding N-heterocyclic cyclometalated ruthenium were reported as efficient Z-selective catalysts for cross-metathesis, showing a different reactivity in the function of the auxiliary ligand and the bulky ligand. To understand the origin of this behavior, we carried out density functional (M06-L) calculations to explore the reaction mechanism and insight from the energetic contributions into the determinant step. We emphasize the differences that occur when the 2,6-diisopropylphenyl (Dipp) and 2,6-diisopentylphenyl (Dipep) are employed. The results show that the barrier energies, $\Delta G^{‡}$, increase when the bulky ligand is greater, using nitrate as an auxiliary ligand, while the opposite behavior is obtained when pivalate is the auxiliary ligand. This tendency has its origin in the low reorganization energy and the less steric hindrance (%V_bur) obtained in catalysts that involve nitrate ligand and Dipep group. Moreover, by scrutinizing the energy decomposition analysis (EDA), it is found that the electronic contributions are also dominant and are not uniquely the steric effects that control the Z-selectivity. Full article

Enzymatic polyethylene terephthalate (PET) recycling processes are gaining interest for their low environmental impact, use of mild conditions, and specificity. Furthermore, PET hydrolase enzymes are continuously being discovered and engineered. In this work, we studied a PET hydrolase (PET2), initially characterized as an alkaline thermostable lipase. PET2 was produced in a fusion form with a 6-histidine tag in the N-terminal. The PET2 activity on aromatic terephthalate and new indole-based polyesters was evaluated using polymers in powder form. Compared with IsPETase, an enzyme derived from Ideonella sakaiensis, PET2 showed a lower PET depolymerization yield. However, interestingly, PET2 produced significantly higher polybutylene terephthalate (PBT) and polyhexylene terephthalate (PHT) depolymerization yields. A clear preference was found for aromatic indole-derived polyesters over non-aromatic ones. No activity was detected on Akestra™, an amorphous copolyester with spiroacetal structures. Docking studies suggest that a narrower and more hydrophobic active site reduces its activity on PET but favors its interaction with PBT and PHT. Understanding the enzyme preferences of polymers will contribute to their effective use to depolymerize different types of polyesters. Full article

Supported nanomaterials are becoming increasingly important in many industrial processes because of the need to improve both the efficiency and environmental acceptability of industrial processes. The unique properties of supported nanomaterials have attracted researchers to develop efficient catalytic materials in nanoscale. The extremely small size of the particles maximizes the surface area exposed to the reactant, allowing more reactions to occur. The environmental hazards resulting from the conventional manufacturing procedures for organic fine chemicals and intermediates by classical oxidation catalysis using mineral acids have forced chemical industries to seek less polluting processes. The present study aimed to oxidize p-toluidine by hydrogen peroxide in the presence of magnetite supported on nanocrystalline titanium silicalite-1 (M/NTS) zeolite at ambient temperature. The products detected are 4,4′-dimethylazobenzene as major product and 4,4′-dimethylazoxybenzene as minor product. Good selectivity, low cost, low wastage of materials and enhanced environmental friendliness of heterogeneous magnetite nanoparticle supported zeolite catalysts were observed. The effect of various reaction parameters such as mole ratio, catalyst weight and reusability of catalyst were studied. At the optimum reaction conditions, the oxidation activity of M/NTS catalyst was compared with M/NS catalyst, and it was found that titanium in the framework of M/NTS provided higher activity and selectivity. Full article

Methyl acetate (MA) has a wide range of applications as an important industrial chemical. Traditional MOR zeolite for carbonylation of DME to MA accumulated carbon easily because of a 12-membered ring (12 MR) channel. In this work, we innovatively developed the method of recrystallization ferrierite (FER) zeolite using special chelating ligand sodium oleate which can affect ions other than alkali metals. The characterization results of N₂ adsorption, transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FT-IR) show that hydrothermal recrystallization of ferrierite using sodium oleate resulted in a higher Si/Al ratio, a bigger specific surface area and a larger number of Brønsted acid sites in the eight MR channels, which was more efficient in the reaction of carbonylation of dimethyl ether than ordinary alkali treatment. Full article

A chromate of copper and cobalt (Φy) was synthesized and characterized. Φy activated peroxymonosulfate (PMS) to degrade ciprofloxacin (CIP) in water. The Φy/PMS combination showed a high degrading capability toward CIP (~100% elimination in 15 min). However, Φy leached cobalt (1.6 mg L⁻¹), limiting its use for water treatment. To avoid leaching, Φy was calcinated, forming a mixed metal oxide (MMO). In the combination of MMO/PMS, no metals leached, the CIP adsorption was low (<20%), and the action of SO₄•⁻ dominated, leading to a synergistic effect on pollutant elimination (>95% after 15 min of treatment). MMO/PMS promoted the opening and oxidation of the piperazyl ring, plus the hydroxylation of the quinolone moiety on CIP, which potentially decreased the biological activity. After three reuse cycles, the MMO still presented with a high activation of PMS toward CIP degradation (90% in 15 min of action). Additionally, the CIP degradation by the MMO/PMS system in simulated hospital wastewater was close to that obtained in distilled water. This work provides relevant information on the stability of Co-, Cu-, and Cr-based materials under interaction with PMS and the strategies to obtain a proper catalyst to degrade CIP. Full article

Tungstophosphoric acid (H₃PW₁₂O₄₀) supported on silica-coated magnetite nanoparticles has been prepared and used as a heterogeneous acid catalyst (Fe₃O₄@SiO₂@HPW) in the condensation of benzaldehyde (B) with glycerol (Gly) for the production of cyclic acetals. Physicochemical techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectrometry (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and N2 physisorption were used to characterize the prepared catalyst. The effect of glycerol/benzaldehyde molar ratio (1/1 to 1/1.2), temperature (80–120 °C), and catalyst amount (1–5%) on glycerol conversion and the selectivity in main reaction products: benzoic acid, 2-phenyl-1,3-dioxolan-4-yl)methanol, 2-Phenyl-1,3-dioxan-5-ol, 2-phenyl-1,3-dioxolane, and methyl 2-hydroxy-3-phenylpropanoate was studied to evaluate the catalytic activity of the prepared Fe₃O₄@SiO₂@HPW catalyst. The optimization of these process parameters was conducted using Box–Behnken design (BBD). Using the BBD methodology, the optimal parameters (120 °C, 1:1.15 glycerol: benzaldehyde, 5% catalyst) were determined, for a glycerol conversion of and cyclic acetals yield of 85.95% and 78.36%, respectively. The catalyst also exhibits excellent activity for glycerol acetalization with other aromatic aldehydes such as cinnamaldehyde, p-methyl-benzaldehyde, p-hydroxy-benzaldehyde, and vanillin. Full article

Cyclohexene esterification–hydrogenation for the efficient production of cyclohexanol will be commercialized for the first time. Cu/MgO/Al₂O₃ catalysts with layered double hydroxides as precursors were developed, and the effect of altering the reduction temperature on the catalytic activity was explored. Fresh and spent Cu/MgO/Al₂O₃ catalysts exhibited excellent catalytic performance after thermal treatment during the hydrogenation of cyclohexyl acetate to cyclohexanol. STEM images showed that the Cu particles grew slightly, without obvious aggregation. Based on the results of XAES and in situ FTIR of the adsorbed CO method, optimal performance (conversion rate of 99.59% with 98.94% selectivity) was achieved, which was attributed to the synergistic effect on the surface-active Cu⁰ and Cu⁺ sites with Cu⁰/(Cu⁰ + Cu⁺) of around 0.70, and the ratios could be maintained at temperatures of 513–553 K. The morphology of Cu/MgO/Al₂O₃ catalysts was well preserved during the hydrogenation of cyclohexyl acetate, indicating potential industrial applications. The well-dispersed Cu/MgO/Al₂O₃ catalyst with a stable microstructure possesses an adjustable valence state and thermal stability during the hydrogenation of cyclohexyl acetate, giving it industrial application prospects. Full article

A green one-pot 2,3,6-trifunctionalization of N-alkyl/aryl indoles was achieved by adding three equivalents of N-Br sulfoximine to the indole solution. A variety of 2-sulfoximidoyl-3,6-dibromo indoles were prepared with 38–94% yields using N-Br sulfoximines as both brominating and sulfoximinating reagents. Based on the results of controlled experiments, we propose that a radical substitution involving 3,6-dibromination and 2-sulfoximination occurs in the reaction process. This is first time that 2,3,6-trifunctionalization of indole in one pot has been achieved. Full article

Researchers studying heterogeneous catalysis are intrigued by single-atom catalysts (SACs) due to their ultrahigh atomic utilization. However, only a few reports on SAC-catalyzed classical organic transformations are available. In this work, atomically dispersed Pd sites are confined to a ZrO₂ hybridized N-doped carbon skeleton with a smart design. UiO-66-NH₂ is used to anchor Pd atoms by the coordination of the donor atoms including lone pairs of electrons and metal atoms. Subsequently, the in situ introduction of ZrO₂ doping is achieved using pyrolysis, which helps improve the catalytic performance by modulating the electronic state. The Pd@ZrO₂/N–C catalyst obtained from the unique design exhibits a high yield (99%) in eco-friendly media with an extremely low noble metal dosage (0.03 mol% Pd) for the Suzuki reaction. Moreover, Pd@ZrO₂/N–C remains highly active after being reused several times and possesses versatility in a variety of substrates. This strategy offers a feasible alternative to designing SACs with atomically dispersed noble metals for heterogeneous reactions. Full article

Ferrocenium catalysis is a vibrant research area, and an increasing number of ferrocenium-catalyzed processes have been reported in the recent years. However, the ferrocenium cation is not very stable in solution, which may potentially hamper catalytic applications. In an effort to stabilize ferrocenium-type architectures by inserting a bridge between the cyclopentadienyl rings, we investigated two ferrocenophanium (or ansa-ferrocenium) cations with respect to their stability and catalytic activity in propargylic substitution reactions. One of the ferrocenophanium complexes was characterized by single crystal X-ray diffraction. Cyclic voltammetry experiments of the ferrocenophane parent compounds were performed in the absence and presence of alcohol nucleophiles, and the stability of the cations in solution was judged based on the reversibility of the electron transfer. The experiments revealed a moderate stabilizing effect of the bridge, albeit the effect is not very pronounced or straightforward. Catalytic propargylic substitution test reactions revealed decreased activity of the ferrocenophanium cations compared to the ferrocenium cation. It appears that the somewhat stabilized ferrocenophanium cations show decreased catalytic activity. Full article

The application of early-metal-based catalysts featuring natural chiral pool motifs, such as amino acids, terpenes and alkaloids, in hydroamination reactions is discussed and compared to those beyond the chiral pool. In particular, alkaline (Li), alkaline earth (Mg, Ca), rare earth (Y, La, Nd, Sm, Lu), group IV (Ti, Zr, Hf) metal-, and tantalum-based catalytic systems are described, which in recent years improved considerably and have become more practical in their usability. Additional emphasis is directed towards their catalytic performance including yields and regio- as well as stereoselectivity in comparison with the group IV and V transition metals and more widely used rare earth metal-based catalysts. Full article

Selective semi-hydrogenation of acetylene is an extremely important reaction from both industrial and theoretical perspectives. Palladium, due to its unique chemical and physical properties, is the most active and currently irreplaceable metal for this reaction in industry, but the poor catalytic selectivity towards ethylene is also its inherent shortcoming. Introducing a secondary metal to tune a geometric and electronic structures of Pd nanoparticles and to create a synergistic effect is the most widely used strategy to effectively improve the overall catalytic performance of Pd-based catalysts. Thus, various supported Pd-based bimetallic catalysts for selective semi-hydrogenation of acetylene have been exploited in the past decade. Timely comparison, analysis, and summarizing of various preparation methods may offer a beneficial reference for the subsequent development of such catalysts. In this context, herein, the advances in synthesis strategies of catalysts, including nano-catalysts, single atom alloys (SAAs), as well as bimetallic dual atom catalysts are summarized systematically. Their advantages and disadvantages are comparatively discussed. Finally, future perspectives for the synthetic strategies of supported Pd-based bimetallic catalysts for selective semi-hydrogenation of acetylene are proposed. Full article

Amphiphilic hybrid catalysts were prepared by modifying [SMo₁₂O₄₀]²⁻ with tetrabutylammonium bromide (TBAB), 1-butyl-3-methylimidazole bromide (BMIMBr) and octadecyl trimethyl ammonium bromide (ODAB), respectively. The prepared catalysts were characterized by IR, XRD, SEM, TG and XPS. The desulfurization performance of the catalysts was investigated in model oil and actual diesel using hydrogen peroxide (H₂O₂) as an oxidant and acetonitrile as an extractant. All catalysts exhibited favorable activity for removing sulfur compounds at room temperature. Dibenzothiophene (DBT) can be nearly completely removed using SMo₁₂O₄₀²⁻-organic catalysts within a short reaction time. For different sulfur compounds, the [TBA]₂SMo₁₂O₄₀ catalyst showed a better removal effect than the [BMIM]₂SMo₁₂O₄₀ and [ODA]₂SMo₁₂O₄₀ catalyst. The [TBA]₂SMo₁₂O₄₀ dissolved in extraction solvent could be reused up to five times in an oxidative desulfurization (ODS) cycle with no significant loss of activity. The [BMIM]₂SMo₁₂O₄₀ performed as a heterogeneous catalyst able to be recycled from the ODS system and maintained excellent catalytic activity. The catalysts showed a positive desulfurization effect in real diesel treatment. Finally, we described the ODS desulfurization mechanism of DBT using SMo₁₂O₄₀²⁻-organic hybrid catalysts. The amphiphilic hybrid catalyst cation captures DBT, while SMo₁₂O₄₀²⁻ reacts with the oxidant H₂O₂ to produce peroxy-active species. DBT can be oxidized to its sulfone by the action of peroxy-active species to achieve ODS desulfurization. Full article

By strategic use of the valence difference between hard gold(III) and soft gold(I) catalysts, one-pot synthesis of (Z)-5-benzylidene-4-phenyl-2-(p-tolyl)-4,5-dihydrooxazole (15) from propargylic alcohol (9) and p-toluamide (13) was achieved via gold(III)-catalyzed propargylic substitution followed by gold(I)-catalyzed cyclization. The structure of 15 was confirmed by X-ray crystallographic analysis. Full article

In this study, a combination of the porous carbon (PCN), montmorillonite (MMT), and TiO₂ was synthesized into a composite immobilized Pd metal catalyst (TiO₂-MMT/PCN@Pd) with effective synergism improvements in catalytic performance. The successful TiO₂-pillaring modification for MMT, derivation of carbon from the biopolymer of chitosan, and immobilization of Pd species for the prepared TiO₂-MMT/PCN@Pd⁰ nanocomposites were confirmed using a combined characterization with X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), N₂ adsorption–desorption isotherms, high-resolution transition electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. It was shown that the combination of PCN, MMT, and TiO₂ as a composite support for the stabilization of the Pd catalysts could synergistically improve the adsorption and catalytic properties. The resultant TiO₂-MMT₈₀/PCN₂₀@Pd⁰ showed a high surface area of 108.9 m²/g. Furthermore, it exhibited moderate to excellent activity (59–99% yield) and high stability (recyclable 19 times) in the liquid–solid catalytic reactions, such as the Sonogashira reactions of aryl halides (I, Br) with terminal alkynes in organic solutions. The positron annihilation lifetime spectroscopy (PALS) characterization sensitively detected the development of sub-nanoscale microdefects in the catalyst after long-term recycling service. This study provided direct evidence for the formation of some larger-sized microdefects during sequential recycling, which would act as leaching channels for loaded molecules, including active Pd species. Full article

Pd-based catalysts are widely used in the oxidation of CH₄ and have a significant impact on global warming. However, understanding their active sites remains controversial, because interconversion between Pd and PdO occurs consecutively during the reaction. Understanding the intrinsic active sites under reaction conditions is critical for developing highly active and selective catalysts. In this study, we demonstrated that partially oxidized palladium (PdO_x) on the surface plays an important role for CH₄ oxidation. Regardless of whether the initial state of Pd corresponds to oxides or metallic clusters, the topmost surface is PdO_x, which is formed during CH4 oxidation. A quantitative analysis using CO titration, diffuse reflectance infrared Fourier-transform spectroscopy, X-ray diffraction, and scanning transmission electron microscopy demonstrated that a surface PdO layer was formed on top of the metallic Pd clusters during the CH₄ oxidation reaction. Furthermore, the time-on-stream test of CH₄ oxidation revealed that the presence of the PdO layer on top of the metallic Pd clusters improves the catalytic activity. Our periodic density functional theory (DFT) calculations with a PdO_x slab and nanoparticle models aided the elucidation of the structure of the experimental PdO particles, as well as the experimental C-O bands. The DFT results also revealed the formation of a PdO layer on the metallic Pd clusters. This study helps achieve a fundamental understanding of the active sites of Pd and PdO for CH₄ oxidation and provides insights into the development of active and durable Pd-based catalysts through molecular-level design. Full article

The chemical industry still requires development of environmentally friendly processes. Acid-catalysed chemical processes may cause environmental problems. Urgent need to replace conventional acids has forced the search for sustainable alternatives. Metal-containing ionic liquids have drawn considerable attention from scientists for many years. These compounds may exhibit very high Lewis acidity, which is usually dependent on the composition of the ionic liquid with the particular content of metal salt. Therefore, metal-containing ionic liquids have found a lot of applications and are successfully employed as catalysts, co-catalysts or reaction media in various fields of chemistry, especially in organic chemistry. Gallium(III)- and indium(III)-containing ionic liquids help to transfer the remarkable activity of metal salts into even more active and easier-to-handle forms of ionic liquids. This review highlights the wide range of possible applications and the high potential of metal-containing ionic liquids with special focus on Ga(III) and In(III), which may help to outline the framework for further development of the presented research topic and synthesis of new representatives of this group of compounds. Full article

The performance of a series of cobalt-based composites in catalytic amination of aromatic aldehydes by amines in the presence of hydrogen as well as hydrogenation of quinoline was studied. The composites were prepared by pyrolysis of Co^II acetate, organic precursor (imidazole, 1,10-phenantroline, 1,2-diaminobenzene or melamine) deposited on aerosil (SiO₂). These composites contained nanoparticles of metallic Co together with N-doped carboneous particles. Quantitative yields of the target amine in a reaction of p-methoxybenzaldehyde with n-butylamine were obtained at p(H₂) = 150 bar, T = 150 °C for all composites. It was found that amination of p-methoxybenzaldehyde with n-butylamine and benzylamine at p(H₂) = 100 bar, T = 100 °C led to the formation of the corresponding amines with the yields of 72–96%. In the case of diisopropylamine, amination did not occur, and p-methoxybenzyl alcohol was the sole or the major reaction product. Reaction of p-chlorobenzaldehyde with n-butylamine on the Co-containing composites at p(H₂) = 100 bar, T = 100 °C resulted in the formation of N-butyl-N-p-chlorobenzylamine in 60–89% yields. Among the considered materials, the composite prepared by decomposition of Co^II complex with 1,2-diaminobenzene on aerosil showed the highest yields of the target products and the best selectivity in all studied reactions. Full article

Through the lens of organocatalysis and phase transfer catalysis, we will examine the key components to calculate or predict catalysis-performance metrics, such as turnover frequency and measurement of stereoselectivity, via computational chemistry. The state-of-the-art tools available to calculate potential energy and, consequently, free energy, together with their caveats, will be discussed via examples from the literature. Through various examples from organocatalysis and phase transfer catalysis, we will highlight the challenges related to the mechanism, transition state theory, and solvation involved in translating calculated barriers to the turnover frequency or a metric of stereoselectivity. Examples in the literature that validated their theoretical models will be showcased. Lastly, the relevance and opportunity afforded by machine learning will be discussed. Full article

Diverse reducing mediators have often been used to increase the degradation of emerging pollutants (EPs) and dyes through the Fenton reaction (Fe²⁺ + H₂O₂ → Fe³⁺ + HO^● + HO⁻). Adding reductants can minimize the accumulation of Fe³⁺ in a solution, leading to accelerated Fe²⁺ regeneration and the enhanced generation of reactive oxygen species, such as the HO^● radical. The present study consisted in reviewing the effects of gallic acid (GA), a plant-extracted reductant, on the Fenton-based oxidation of several EPs and dyes. It was verified that the pro-oxidant effect of GA was not only reported for soluble iron salts as a catalyst (homogeneous Fenton), but also iron-containing solid materials (heterogeneous Fenton). The most common molar proportion verified in the studies was catalyst:oxidant:GA equal to 1:10–20:1. This shows that the required amount of both catalyst and GA is quite low in comparison with the oxidant, which is generally H₂O₂. Interestingly, GA has proven to be an effective mediator at pH values well above the ideal range of 2.5–3.0 for Fenton processes. This allows treatments to be carried out at the natural pH of the wastewater. The use of plant extracts or wood barks containing GA and other reductants is suggested to make GA-mediated Fenton processes easier to apply for treating real wastewater. Full article

In this work, two new 1D Cd(II) coordination polymers (CPs), [Cd(L1)(NMF)₂]_n (1) and [Cd(L2)(DMF)(H₂O)₂]_n·n(H₂O) (2), have been synthesized, characterized and employed as catalysts for the microwave-assisted solvent-free Strecker-type cyanation of different acetals. Solvothermal reaction between the pro-ligand, 5-{(pyren-1-ylmethyl)amino}isophthalic acid (H₂L1) or 5-{(anthracen-9-ylmethyl)amino}isophthalic acid (H₂L2), and Cd(NO₃)₂.6H₂O in the presence of NMF or DMF:THF solvent, produces the coordination polymer 1 or 2, respectively. These frameworks were characterized by single-crystal and powder X-ray diffraction analyses, ATR-FTIR, elemental and thermogravimetry analysis. Their structural analysis revealed that both CPs show one-dimensional structures, but CP 1 has a 1D double chain type structure whereas CP 2 is a simple one-dimensional network. In CP 1, the dinuclear {Cd₂(COO)₄} unit acts as a secondary building unit (SBU) and the assembly of dinuclear SBUs with deprotonated ligand (L1²⁻) led to the formation of a 1D double chain framework. In contrast, no SBU was observed in CP 2. To test the catalytic effectiveness of these 1D compounds, the solvent-free Strecker-type cyanation reactions of different acetals in presence of trimethylsilyl cyanide (TMSCN) was studied with CPs 1 and 2 as heterogenous catalysts. CP 1 displays a higher activity (yield 95%) compared to CP 2 (yield 84%) after the same reaction time. This is accounted for by the strong hydrogen bonding packing network in CP 2 that hampers the accessibility of the metal centers, and the presence of the dinuclear Cd(II) SBU in CP 1 which can promote the catalytic process in comparison with the mononuclear Cd(II) center in CP 2. Moreover, the recyclability and heterogeneity of both CPs were tested, demonstrating that they can be recyclable for at least for four cycles without losing their structural integrity and catalytic activity. Full article

N-hydroxyimides are widely known as organocatalysts for aerobic oxidation and oxidative coupling reactions, in which corresponding imide-N-oxyl radicals play the role of catalytically active hydrogen atom abstracting species. The drawbacks of many N-hydroxyimides are poor solubility in low polarity solvents and limited activity in the cleavage of unactivated C–H bonds. To overcome these shortcomings, we have synthesized a new lipophilic N-hydroxyimide, 5,8-di-tert-butyl-2-hydroxy-1H-benzo[de]isoquinoline-1,3(2H)-dione, with high solubility in low-polarity solvents such as DCM. According to the EPR study, the stability of the corresponding imide-N-oxyl radical is comparable to that of the non-tert-butylated analogue, naphthalimide-N-oxyl radical. DFT calculations showed that the NO–H bond dissociation enthalpy (BDE) in the synthesized tert-butylated-N-hydroxynaphthalimide is one of the highest in N-hydroxyimide series, which corresponds to high hydrogen atom abstracting reactivity and may be useful in catalysis of strong C–H bond oxidative cleavage. The synthesized compound can be considered as catalyst for liquid-phase free-radical oxidation and oxidative coupling reactions in non-polar media where solubility was previously the limiting factor. Full article

Aluminosilicate and ZSM-5 catalyst were synthesized from local materials, low-grade Indonesian kaolin. High quartz impurities content in the low-grade kaolin was successfully reduced by the consecutive treatment process including washing, centrifugation, and Fe³⁺ treatment. All the synthesized catalyst showed mesoporous structure with pore diameter around 3.5 nm. The catalytic activity was investigated in the acetalization of 3,4-dimethoxybenzaldehyde and propylene glycol, then the effect of a different base (TPAOH and NaOH) and Fe³⁺ addition in the treatment process to the catalytic activity was discussed. The catalytic activity of the aluminosilicate catalyst outperforms the ZSM-5. Interestingly, it is found that the catalytic activity of the catalyst can be enhanced by addition of Fe³⁺ in the aluminosilicate, with enhanced the conversion from 32.2% to 81.6%, whereas Fe³⁺ addition to ZSM-5 showed slightly increased conversion value from 0% to 3.65%. All catalysts showed high selectivity of 100% of the reaction product 2-(3,4-dimethoxy-phenyl)-4-methyl-1,3-dioxolane. Full article

The effects of reaction conditions on the yield of ethylene and propylene from pentene cracking were investigated in a fixed-bed reactor at 500–750 °C and for a weight hourly space velocity (WHSV) of 15–83 h⁻¹. The total yield of ethylene and propylene reached a maximum (67.8 wt%) at 700 °C and 57 h⁻¹. In order to explore the reaction mechanism at high temperatures, a thermal/catalytic cracking proportion model was established. It was found that the proportion of pentene feed chemically adsorbed with the acid sites and cracked through catalytic cracking was above 88.4%, even at 750 °C. Ethylene and propylene in the products were mainly derived from catalytic cracking rather than thermal cracking at 650–750 °C. In addition, the suitable reaction network for pentene catalytic cracking was deduced and estimated. The results showed that the monomolecular cracking proportion increased from 1% at 500 °C to 95% at 750 °C. The high selectivity of ethylene and propylene at high temperatures was mainly due to the intensification of the monomolecular cracking reaction. After 20 times of regeneration, the acidity and pore structure of the zeolite had hardly changed, and the conversion of pentene remained above 80% at 650 °C. Full article

The activation and transformation of C–F bonds in fluoro-aromatics is a highly desirable process in organic chemistry. It provides synthetic methods/protocols for the generation of organic compounds possessing single or multiple C–F bonds, and effective catalytic systems for further study of the activation mode of inert chemical bonds. Due to the high polarity of the C–F bond and it having the highest bond energy in organics, C–F activation often faces considerable academic challenges. In this mini-review, the important research achievements in the activation and transformation of aromatic C–F bond, catalyzed by transition metal and metal-free systems, are presented. Full article

Iron-based particles loaded on porous carbon materials have attracted extensive attention as catalysts for denitration and desulfurization reactions. However, the carbon support of a high-temperature denitration catalyst is inevitably oxidized in the presence of H₂O and O₂. The mechanism of denitration catalyst oxidation and its influence on the catalytic reaction remain to be further explored. Fe₂O₃-loaded graphene models with carbon vacancy (G_def), hydroxyl (HyG), and carboxyl (CyG) were constructed to investigate the effects of hydroxylation and carboxylation on the catalytic activity of Fe₂O₃/graphene for oxidative desulfurization and denitration by using density functional theory (DFT) calculations. According to the analysis of structural properties and adsorption energy, the adsorption process of Fe₂O₃ on HyG and CyG was observed to have proceeded more favorably than that on G_def. The density-of-states (DOS) results also affirmed that HyG and CyG promote the electron delocalization of Fe₂O₃ around the Fermi level, enhancing the chemical activity of Fe₂O₃. Moreover, adsorption energy analysis indicates that hydroxylation and carboxylation enhanced the adsorption of SO₂ and H₂O₂ on Fe₂O₃/graphene while also maintaining preferable adsorption stability of NO. Furthermore, mechanistic research explains that adsorbed H₂O₂ on HyG and CyG directly oxidizes NO and SO₂ into HNO₂ and H₂SO₄ following a one-step reaction. The results provide a fundamental understanding of the oxidized catalyst on catalytic denitration and desulfurization reactions. Full article

The protocol, 3-methyldec-1-yn-3-ol (1a) was chosen to perform the dimerization process. The optimal conditions for synthesis of 8,13-dimethylicosa-9,11-diyne-8,13 (2a) with high efficiency when using copper-catalyzed, N,N,N′N′-tetramethylethylenediamine as a ligand and CCl₄ and methanol solvents in atmospheric pressure were determined. The structure of the obtained compound was proved by IR, ¹H-NMR and ¹³C-NMR spectroscopy. Full article

We have designed, built, and tested two cells for in situ and, potentially, operando X-ray absorption spectroscopy experiments in transmission and fluorescence modes. The cells were developed for high-pressure and high-temperature conditions to study the catalytic processes under relevant industrial conditions. Operation of the cells was tested for Ru and Rh-based homogeneous and heterogeneous catalytic systems. Using synchrotron-based in situ X-ray absorption spectroscopy we tracked the evolution of active metal species during catalytic reactions. Our setup proved that it was capable to investigate liquid-state homogeneous and heterogenous systems under elevated temperatures, high pressures of reactive gasses, and in the presence of corrosive reagents. Full article

The mechanism of reaction in isobutane/2-butene alkylation systems is extremely complicated, accompanied by numerous side reactions. Therefore, a comprehensive understanding of the reaction pathways in this system is essential for an in-depth discussion of the reaction mechanism and for improving the selectivity of the major products (clean fuel blend components). The alkylation of isobutane/2-butene was studied using a self-made intermittent reaction device with a metering, cooling, reaction, vacuum and analysis system. The alkylates were qualitatively and quantitatively analyzed using a capillary gas chromatography-mass spectrometry-data system (CGC-MS-DS) and capillary gas chromatography with flame ionization detection (CCGC-FID), respectively, and the precision and recovery of the quantitative analytical methods were verified. The results showed that the relative standard deviation (RSD) of the standard sample was below 0.78%, and the recoveries were from 98.53% to 102.85%. Under the specified reaction conditions, 79 volatile substances were identified from the alkylates, and the selectivity of C₈ and trimethylpentanes (TMPs) reached 63.63% and 53.81%, respectively. The changes of the main chemical components in the alkylation reaction with time were tracked and analyzed, based on which reaction pathways were determined, and a complex reaction network containing the main products’ and the by-products’ generation pathway was constructed. Full article

Immobilized poly(ethylene glycol) (PEG 600-PS) was used as an effective phase-transfer catalyst for the synthesis of hydroxypivaldehyde from isobutyraldehyde (IBA) and formaldehyde in the presence of an inorganic base. Studies on the influence of the parameters on the course of the reaction in a batch reactor showed that the use of the PEG 600-PS catalyst allowed one to obtain HPA with high efficiency (IBA conversion >96%, selectivity >98%) in a relatively short time and under mild conditions (2 h, 40 °C). The developed method enables easy separation of the post-reaction mixture by simple phase separation, and the immobilized catalyst can be separated by filtration and then used five times without a loss in its activity. The high activity and stability of the catalyst was also confirmed in a test carried out in a flow reactor. Full article

Succinic acid esters are important compounds that find many applications in various industrial fields. One of the most promising and easy ways of producing these molecules is represented by the bis-alkoxycarbonylation reaction of olefins. In particular, a recently developed catalytic system, consisting of an aryl α-diimine/palladium(II) catalyst and p-benzoquinone as an oxidant, has allowed succinates to be obtained in high yields. A similar methodology was applied here for the unprecedented synthesis of the bis(2-hydroxyethyl) 2-phenylsuccinate in 78% isolated yield, starting from the cheap and commercially available compounds styrene and ethylene glycol. To our knowledge, no other examples of bis-alkoxycarbonylations of olefins involving diols have been reported thus far. The obtained product was fully characterized by NMR and ESI-MS analyses. Full article

A series of CrO_x-ZrO₂-SiO₂ (CrZrSi) catalysts was prepared by a “one-pot” template-assisted evaporation-induced self-assembly process. The chromium content varied from 4 to 9 wt.% assuming Cr₂O₃ stoichiometry. The catalysts were characterized by XRD, SEM-EDX, temperature-programmed reduction (TPR-H₂), Raman spectroscopy, and X-ray photoelectron spectroscopy. The catalysts were tested in non-oxidative propane dehydrogenation at 500–600 °C. The evolution of active sites under the reaction conditions was investigated by reductive treatment of the catalysts with H₂. The catalyst with the lowest Cr loading initially contained amorphous Cr³⁺ and dispersed Cr⁶⁺ species. The latter reduced under reaction conditions forming Cr³⁺ oxide species with low activity in propane dehydrogenation. The catalysts with higher Cr loadings initially contained highly dispersed Cr³⁺ species stable under the reaction conditions and responsible for high catalyst activity. Silica acted both as a textural promoter that increased the specific surface area of the catalysts and as a stabilizer that inhibited crystallization of Cr₂O₃ and ZrO₂ and provided the formation of coordinatively unsaturated Zr⁴⁺ centers. The optimal combination of Cr³⁺ species and coordinatively unsaturated Zr⁴⁺ centers was achieved in the catalyst with the highest Cr loading. This catalyst showed the highest efficiency. Full article

Two new ruthenium complexes with chelating-ether benzylidene ligands bearing a furan moiety were synthesized and characterized, including X-ray crystallography. They initiated fast, also at 0 °C, and were found to be highly active in a variety of ring-closing, ene-yne, and cross-metathesis reactions, including an active pharmaceutical ingredient (API) model, which makes them good candidates for the transformation of complex polyfunctional compounds that require mild reaction conditions. Full article

The mechanism in palladium-catalyzed carboxylation of thiophene and CO₂ is investigated using the density functional theory (DFT) calculations, including three consecutive steps of the formation of carbanion through breaking the C–H bond(s) via the palladium acetate, the elimination of acetic acid and the nucleophile attacking the weak electrophile CO₂ to form C–C bond. Results show that the C–C bond is formed through taking the three-membered cyclic conformation arrangement involving the interaction of the transition metal and the CO₂, and the CO₂ insertion step is the rate-determining step for this entire reaction process. Aiming to precisely disclose what factor determine the origin of the activation energy barrier in this carboxylation reaction, the distortion/interaction analysis is performed along with the entire reaction coordinate. Full article

Coke formation on n-butene cracking catalyst is the main reason for the reducing of its lifetime. To study the effects of acidity and textural properties on the coke formation process, a series of HY zeolite-type catalysts were prepared by ammonium hexafluorosilicate treatment (AHFS). NH₃-TPD and Py-IR-TPD were used to systematically study the change law of zeolite acidity. It was found that with the increase of AHFS concentration, the acid density decreased, whereas the ratio of Brønsted acid to Lewis acid first increased and then decreased. Meanwhile, the percentage of Brønsted acid inside the supper cages increased and the strength of Brønsted acid increased with the degree of dealumination. Combined with in situ IR study on coke formation, the relationship between coking and acid site was revealed. It was found that the rate of coke formation on zeolites was affected by acid density, which is the rate of coke formation decreased with the decline of acid density. When the acid density remains at the same level, it was the acid strength that determined the coke formation rate—the stronger the acid strength, the faster the coke formation rate. Full article

The development of efficient Pt-supported zeolite catalysts with tunable micro/mesopore structures for the removal of volatile organic compounds (VOCs) presents a major challenge. Herein, hierarchical Pt/Y zeolites with tunable mesopores are fabricated by varying the etching time before the surfactant-templated crystal rearrangement method and used as catalyst supports for VOC oxidation. The hierarchical Pt/Y zeolites provided an excellent environment for Pt nanoparticle loading with abundant accessible acidic sites. The catalytic performance of the obtained hierarchical Pt/Y zeolites is analyzed using toluene oxidation, with the modified zeolites exhibiting improved catalytic activities. The hierarchical Pt/Y zeolites exhibited higher catalytic toluene oxidation activities than non-hierarchical Pt/Y zeolites. Pt/Y-6h demonstrated the highest catalytic toluene oxidation activity of the prepared catalysts, with a T₉₀ of 149 °C, reaction rate of 1.15 × 10⁻⁷ mol g_cat⁻¹ s⁻¹, turnover frequency of 1.20 × 10⁻² s⁻¹, and an apparent activation energy of 66.5 kJ mol⁻¹ at 60,000 mL g⁻¹ h⁻¹ at a toluene concentration of 1000 ppm. This study will facilitate the fine-tuning of hierarchically porous materials to improve material properties and achieve higher catalytic performance toward VOC oxidation. Full article

With the consumption of fossil fuels, the level of CO₂ in the atmosphere is growing rapidly, which leads to global warming. Hence, the chemical conversion of CO₂ into high value-added products is one of the most important approaches to reducing CO₂ emissions. Due to being simple, inexpensive and environmentally friendly, the direct synthesis of cyclic carbonates from olefins and CO₂ is a promising project for industrial application. In this review, we discuss the design of the homogeneous and heterogeneous catalytic system for the synthesis of cyclic carbonates from the reaction of olefins and CO₂. Usually, the catalyst contains the epoxidation active site and the cycloaddition active site, which could achieve the oxidation of oleifins and the CO₂-insert, respectively. This review will provide a comprehensive overview of the direct synthesis of cyclic carbonates from olefins and CO₂ catalyzed by homogeneous and heterogeneous catalysts. The focus mainly lies on the rational fabrication of multifunctional catalysts, and provides a new perspective for the design of catalysts. Full article

Converting solar energy to chemical energy through a photocatalytic reaction is an efficient technique for obtaining a clean and affordable source of energy. The main problem with solar photocatalysts is the recombination of charge carriers and the large band gap of the photocatalysts. The plasmonic noble metal coupled with a semiconductor can give a unique synergetic effect and has emerged as the leading material for the photocatalytic reaction. The LSPR generation by these kinds of materials has proved to be very efficient in the photocatalytic hydrolysis of the hydrogen-rich compound, photocatalytic water splitting, and photocatalytic degradation of organic dyes. A noble metal coupled with a low bandgap semiconductor result in an ideal photocatalyst. Here, both the noble metal and semiconductor can absorb visible light. They tend to produce an electron–hole pair and prevent the recombination of the generated electron–hole pair, which ultimately reacts with the chemicals in the surrounding area, resulting in an enhanced photocatalytic reaction. The enhanced photocatalytic activity credit could be given to the shared effect of the strong SPR and the effective separation of photogenerated electrons and holes supported by noble metal particles. The study of plasmonic metal nanoparticles onto semiconductors has recently accelerated. It has emerged as a favourable technique to master the constraint of traditional photocatalysts and stimulate photocatalytic activity. This review work focuses on three main objectives: providing a brief explanation of plasmonic dynamics, understanding the synthesis procedure and examining the main features of the plasmonic metal nanostructure that dominate its photocatalytic activity, comparing the reported literature of some plasmonic photocatalysts on the hydrolysis of ammonia borane and dye water treatment, providing a detailed description of the four primary operations of the plasmonic energy transfer, and the study of prospects and future of plasmonic nanostructures. Full article

The application of layered zeolites of MWW topology in environmental catalysis has attracted growing attention in recent years; however, only a few studies have explored their performance in selective catalytic reduction with ammonia (NH₃-SCR). Thus, our work describes, for the first time, the one-pot synthesis of Fe-modified NH₃-SCR catalysts supported on MCM-22, MCM-36, and ITQ-2. The calculated chemical composition of the materials was Si/Al of 30 and 5 wt.% of Fe. The reported results indicated a correlation between the arrangement of MWW layers and the form of iron in the zeolitic structure. We have observed that one-pot synthesis resulted in high dispersion of Fe³⁺ sites, which significantly enhanced low-temperature activity and prevented N₂O generation during the reaction. All of the investigated samples exhibited almost 100% NO conversion at 250 °C. The most satisfactory activity was exhibited by Fe-modified MCM-36, since 50% of NO reduction was obtained at 150 °C for this catalyst. This effect can be explained by the abundance of isolated Fe³⁺ species, which are active in low-temperature NH₃-SCR. Additionally, SiO₂ pillars present in MCM-36 provided an additional surface for the deposition of the active phase. Full article

Cu₂Y₂O₅ perovskite was reduced at different temperatures under H₂ atmosphere to prepare two Cu-Y₂O₃ catalysts. The results of the activity test indicated that the Cu-Y₂O₃ catalyst after H₂-reduction at 500 °C (RCYO-500) exhibited the best performance in the temperature range from 100 to 180 °C for water gas shift (WGS) reaction, with a CO conversion of 57.30% and H₂ production of 30.67 μmol·g_cat⁻¹·min⁻¹ at 160 °C and a gas hourly space velocity (GHSV) of 6000 mL·g_cat⁻¹·h⁻¹. The catalyst reduced at 320 °C (RCYO-320) performed best at the temperature range from 180 to 250 °C, which achieved 86.44% CO conversion and 54.73 μmol·g_cat⁻¹·min⁻¹ H₂ production at 250 °C. Both of the Cu-Y₂O₃ catalysts had similar structures including Cu°, Cu⁺, oxygen vacancies (Vo) on the Cu°-Cu⁺ interface and Y₂O₃ support. RCYO-500, with a mainly exposed Cu° (100) facet, was active in the low-temperature WGS reaction, while the WGS activity of RCYO-320, which mainly exposed the Cu° (111) facet, was greatly enhanced above 180 °C. Different Cu° facets have different abilities to absorb H₂O and then dissociate it to form hydroxyl groups, which is the main step affecting the catalytic rate of the WGS reaction. Full article

Thiourea was introduced into (R,R)-1,2-diphenylethylenediamine as an organocatalyst to promote the reaction between isobutyraldehydes and maleimides. Enantioselective Michael addition reaction was carried out as an eco-friendly method using water as the solvent. As a result of the reaction between isobutyraldehyde and maleimide, ≥97% yield and 99% enantioselectivity were obtained at a low catalyst loading of 0.01 mol%. The solvent effect can be explained by theoretical calculations that indicate the participation of a transition state, in which the CF₃ substituent of the catalyst is a hydrogen bond activated by the surrounding water molecules. This discovery enabled the use of low catalyst loading in the organic reactions of chiral substances for pharmaceutical applications. Furthermore, a solvent effect for Michael reaction of the organocatalysts was proposed, and the organic reaction mechanisms were determined through quantum calculations. Full article

A series of TiO₂-SiC supported Ni-based catalysts with and without ceria doping were prepared by a traditional impregnation method. CeO₂ was introduced into the catalyst in different steps of the impregnation process. All the samples were characterized by N₂ physisorption, XRD, TPR, and TGA, and were tested for the performance of CO methanation in a fixed-bed reactor under atmospheric conditions through the steam of H₂/CO = 3 without diluent gas. All the Ni-based catalysts supported by TiO₂-SiC exhibited the property of anti-sintering and could efficiently avoid carbon deposition occurring on catalysts. The experimental results show that the performance of all CeO₂ doping samples (more than 80% of CO conversion) was better than the sample without CeO₂ (around 20% of CO conversion). Introducing CeO₂ after the dry step of impregnation achieved complete CO conversion at a lower temperature compared with its introduction through doping at the co-impregnation and step-impregnation methods. The results of further characterization indicate that the addition of CeO₂ in different impregnation steps affected the dispersion of nickel on support, made the size of metal particles smaller, and changed the reducibility of catalysts. Full article

Visible-light-driven heterostructure Ag/Bi₂WO₆ nanocomposites were prepared using a hydrothermal method followed by the photodeposition of Ag on Bi₂WO₆. A photocatalyst with a different molar ratio of Ag to Bi₂WO₆ (1:1, 1:2 and 2:1) was prepared. The catalytic performance of Ag/Bi₂WO₆ towards the photocatalytic oxidation of rhodamine B (RhB) and methylene blue (MB) was explored. Interestingly, the Ag/Bi₂WO₆ (1:2) catalyst exhibited superior performance; it oxidized 83% of RhB to Rh-110 and degraded 68% of MB in 90 min. This might be due to the optimum amount of Ag nanoparticles, which supported the rapid generation and transfer of separated charges from Bi₂WO₆ to Ag through the Schottky barrier. An excess of Ag on Bi₂WO₆ (1:1 and 2:1) blocked the active sites of the reaction and did not produce the desired result. The introduction of Ag on Bi₂WO₆ improved the electrical conductivity of the composite and lowered the recombination rate of charge carriers. Our work provides a cost-effective route for constructing high-performance catalysts for the degradation of toxic dyes. Full article

Three mononuclear 2-picolylamine-containing zinc(III) complexes viz [(2-PA)₂ZnCl]₂(ZnCl₄)] (Zn1), [(2-PA)₂Zn(H₂O)](NO₃)₂] (Zn2) and [Zn(2-PA)₂(OH)]NO₃] (Zn3) were synthesized and fully characterized. Spectral and X-ray structural characteristics showed that the Zn1 complex has a square-pyramidal coordination environment around a zinc(II) core. The hydroxide complex Zn3 was non-covalently functionalized with few layers of graphene oxide (GO) sheets, formed by exfoliation of GO in water. The resulting Zn3/GO hybrid material was characterized by FT-IR, TGA-DSC, SEM-EDX and X-ray powder diffraction. The way of interaction of Zn3 with GO has been established through density functional theory (DFT) calculations. Both experimental and theoretical findings indicate that, on the surface of GO, the complex Zn3 forms a complete double-sided adsorption layer. Zn3 and its hybrid form Zn3/GO have been individually investigated as electrocatalysts for the hydrogen evolution reaction. The hybrid heterogenized form Zn3/GO was supported on glassy carbon (GC) with variable loading densities of Zn3 (0.2, 0.4 and 0.8 mg cm⁻²) to form electrodes. These electrodes have been tested as molecular electrocatalysts for the hydrogen evolution reaction (HER) using linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) in 0.1 M KOH. Results showed that both GC-Zn3 and GC-Zn3/GO catalysts for the HER are highly active, and with increase of the catalyst’s loading density, this catalytic activity enhances. The high catalytic activity of HER with a low onset potential of −140 mV vs. RHE and a high exchange current density of 0.22 mA cm⁻² is achieved with the highest loading density of Zn3 (0.8 mg cm⁻²). To achieve a current density of 10 mA cm⁻², an overpotential of 240 mV was needed. Full article

The titania pulp—a semi product received from the industrial production of titania white—was submitted for the thermal heating at 400–600 °C under Ar and H₂ to obtain TiO₂ with different structure and oxygen surface defects. Heating of titania in H₂ atmosphere accelerated dehydration and crystallisation of TiO₂ compared to heating in Ar. TiO₂ prepared at 500 and 600 °C under H₂ had some oxygen vacancies and Ti³⁺ centres (electron traps), whereas TiO₂ obtained at 450 °C under H₂ exhibited some hole traps centres. The presence of oxygen vacancies induced adsorption of atmospheric CO₂. It was evidenced, that ethylene reacted with TiO₂ after UV irradiation. Formic acid was identified on TiO₂ surface as the reaction product of ethylene oxidation. Hydroxyl radicals were involved in complete mineralisation of ethylene. TiO₂ prepared at 500 °C under H₂ was poorly active because some active sites for coordination of ethylene molecules were occupied by CO₂. The most active samples were TiO₂ with high quantity of OH terminal groups. At 50 °C, the physically adsorbed water molecules on titania surface were desorbed, and then photocatalytic decomposition of ethylene was more efficient. TiO₂ with high quantity of chemisorbed OH groups was very active for ethylene decomposition. The acidic surface of TiO₂ enhances its hydroxylation. Therefore, it is stated that TiO₂ having acidic active sites can be an excellent photocatalyst for ethylene decomposition under UV light. Full article

Nonoxidative dehydrogenation of isobutane is one of the sustainable strategies for producing high value added isobutene. As alternatives for the commercial Pt- and Cr-based dehydrogenation catalysts, supported V-based catalysts are worthy of study. In this work, a series of VO_x/mMgAlO-R catalysts (m = 10, 15, 20, 25 and 30) were designed and prepared by loading VO_x on mMgAlO composite oxide supports derived from mesoporous Al₂O₃-supported layered double hydroxide (LDH) nanocomposites. The calcined and reduced catalysts were characterized by X-ray diffraction (XRD), Raman spectra, Ultraviolet-visible diffuse reflectance (UV-Vis) spectra, NH₃ temperature-programmed desorption (NH₃-TPD), Temperature-programmed reduction (H₂-TPR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TG) and low temperature N₂ adsorption–desorption isotherms. The as-synthesized VO_x/20MgAlO-R with appropriate Mg addition exhibits superior activity (43–56% conversion and 77–81% selectivity), excellent stability and coking-resistance for the isobutane dehydrogenation. The structure–performance relationship reveals that the formation of VO_x species confined in the reconstructed LDH interlayer and porous MgO facilitates dispersing and stabilizing the VO_x species. The low polymerization degree and higher proportion of V⁴⁺ ion for VO_x species, strong acidity of medium acid sites and low concentration of strong acid sites are responsible for the excellent anti-coking and catalytic performance. The strong VO_x–support interaction is beneficial for enhancing the stability of the catalysts. Full article

The incorporation of tungsten trioxide (WO₃) by various concentrations of graphitic carbon nitride (g-C₃N₄) was successfully studied. X-ray diffraction (XRD), Scanning Electron Microscope (SEM), and Diffused Reflectance UV-Vis techniques were applied to investigate morphological and microstructure analysis, diffused reflectance optical properties, and photocatalysis measurements of WO₃/g-C₃N₄ photocatalyst composite organic compounds. The photocatalytic activity of incorporating WO3 into g-C₃N₄ composite organic compounds was evaluated by the photodegradation of both Methylene Blue (MB) dye and phenol under visible-light irradiation. Due to the high purity of the studied heterojunction composite series, no observed diffraction peaks appeared when incorporating WO₃ into g-C₃N₄ composite organic compounds. The particle size of the prepared composite organic compound photocatalysts revealed no evident influence through the increase in WO₃ atoms from the SEM characteristic. The direct and indirect bandgap were recorded for different mole ratios of WO₃/g-C₃N_4, and indicated no apparent impact on bandgap energy with increasing WO₃ content in the composite photocatalyst. The composite photocatalysts’ properties better understand their photocatalytic activity degradations. The pseudo-first-order reaction constants (K) can be calculated by examining the kinetic photocatalytic activity. Full article

CF₄, one of the Perfluorocompounds (PFCs), also known as a greenhouse gas with high global warming potential. In this study, Zr/γ-Al₂O₃ catalysts were developed for CF₄ decomposition. The addition of Zr onto γ-Al₂O₃ achieves a high CF₄ conversion efficiency of 85% at 650 °C and maintain its activity for more than 60 h, which is obviously higher than that of bare γ-Al₂O₃ (50%). The mechanism involved in CF₄ decomposition over the Zr/γ-Al₂O₃ are clarified that the surface Lewis acidity sites are the main active center for CF₄ directly adsorbing and decomposing. The results of NH₃-TPD and FT-IR analyses suggest that the amount of Lewis acidity sites on catalyst surface increases significantly after the introduction of Zr, thereby enhancing the activity of catalyst for CF₄ decomposition. The results of XPS analyses confirms the electrons transfer from Zr to Al, which contribute to the increase in Lewis acidity sites. The results of this work will help the development of more effective catalysts for CF₄ decomposition. Full article

Herein, the design, synthesis, supramolecular interactions and structural analysis of a novel bidentate carboxylate chelating N-heterocylic carbene (NHC) ligand is presented. The NHC structure was modified to strategically incorporate adamantyl moiety for the formation of a supramolecular complex with host molecules such as cucurbiturils. The adamantyl modified NHC ligand could potentially be used in recoverable homogeneous catalysts when Immobilized on a solid support via host–guest chemistry. As a versatile precursor, NHC ligand (8) was synthesized and characterized by ¹H-NMR, ¹³C-NMR, FTIR, single crystal x-ray crystallography and elemental analysis. A proof-of-principle non-covalent immobilization of the NHC ligand (8) with a Cucurbit[7]uril (CB7) host was demonstrated using ¹H-NMR titration. Full article

Chloroaluminate ionic liquid bound on magnetic nanoparticles (Fe₃O₄@O₂Si[PrMIM]Cl·AlCl₃) was prepared and used as a heterogenous Lewis acidic catalyst for the Friedel–Crafts sulfonylation of aromatic compounds with sulfonyl chlorides or p-toluenesulfonic anhydride. The catalyst’s stability, efficiency, easy recovery, and high recyclability without considerable loss of catalytic capability after four recycles were evidence of its advantages. Furthermore, the stoichiometry, wide substrate scope, short reaction time, high yield of sulfones, and solvent-free reaction condition also made this procedure practical, ecofriendly, and economical. Full article

Biomass plays an important role in the green manufacture of high value-added chemicals. Among them, the conversion of furfural (FFA) into 2-methylfuran (2-MF), catalyzed by a copper-chromium catalyst, is important in its industrial application. However, the use of chromium is limited due to its toxicity and pollution of the environment. In this paper, a Cu/SiO₂ catalyst, prepared by the ammonia evaporation method, shows a better catalytic performance compared with that prepared by the co-precipitation method for the vapor-phase hydrodeoxygenation of FFA. The selectivity of 2-MF is higher than 80% with almost a complete conversion of FFA. Combined with the characterizations, the superiority of the ammonia evaporation method is attributed to the reduction of highly dispersed copper species and the increased Cu⁺/(Cu⁺ + Cu⁰) ratio due to the formation of a large content of copper phyllosilicate during the preparation. Moreover, Cu⁺ sites can act as a weak acid site, which improve the surface acidity of the catalyst and facilitate the formation of 2-MF. This new catalytic system provides a feasible and promising strategy for the industrial preparation of 2-MF from FFA, and effectively utilizes biomass resources to promote the development of biomass industry. Full article

The Fenton reaction is one of the most important processes for water and soil remediation, although this process has some drawbacks such as the use of H₂O₂ in large amounts, the formation of sludge due to the use of iron salts, and the need for acid pH values. Here we present the use of a natural clay, modified by acid treatment, as a heterogeneous catalyst to replace soluble iron salts and to avoid the use of water peroxide, resulting in a considerable increase in the attractiveness of the process. Halloysite (HT) clay from the Dunino mine consists of alumina and silica layers with the presence of iron species acting as a source of Fe ions. The etching of alumina layers using hydrochloric acid induces the release of iron species (mainly ions) in the solution, giving rise to the photodegradation activity of organic contaminants in water (i.e., Methyl Orange, MO) under UV irradiation without the need for hydrogen peroxide and avoiding the formation of sludges. MO adsorption properties and MO photodegradation ability were investigated for untreated and acid treated samples, respectively, to achieve the optimal process conditions. MO was not adsorbed on the clay’s surface due to electrostatic repulsion, but a complete degradation was observed after three hours under UV irradiation. The kinetics of photodegradation and the values of the half-life time are presented as a measure of the degradation rate. The proposed process shows a new route for effective remediation of water containing biologically active organic substances dissolved in it. Full article