Acid Catalyst Research Articles

Bifunctional mixed-valence ruthenium heterostructure for robust electrocatalytic water splitting in acid media

The incorporation of non-metal dopants can significantly enhance catalytic activity and improve stability. Furthermore, the creation of heterostructures is particularly advantageous to facilitate charge transfer and optimize electronic properties. This study presents an effective bifunctional mixed-valence Ruthenium heterostructure synthesized through a cascading process involving grinding with carbon nitride and subsequent thermal treatment. The catalyst exhibits outstanding electrocatalytic performance with remarkably low overpotentials of 197 mV for the oxygen evolution reaction (OER) and 24.8 mV for the hydrogen evolution reaction (HER), respectively, with the stability exceeding 24 h at a current density of 10 mA cm⁻2 in acidic media. Additionally, when employed in an acidic oxygen water splitting (OWS) electrolyzer, the bifunctional catalyst demonstrates excellent activity, achieving an ultralow cell voltage of 1.53 V to sustain 10 mA cm⁻2. Enhanced performance is attributed to efficient charge transfer and increased exposure of active sites, providing valuable insights for the development of effective acidic water-electrolysis catalysts for sustainable hydrogen production.

Lemon Juice as a Natural Biodegradable Catalyst for an Ecofriendly One-Pot Pseudo-Three-Component Synthesis of N,1-Dimethyl-6-(methylsulfanyl)-3,5-dinitro-1,4-dihydropyridine-2-amines

AbstractA one-pot pseudo-three-component reaction strategy has been designed for synthesizing all-carbon-functionalized hexasubstituted N,1-dimethyl-6-(methylsulfanyl)-3,5-dinitro-1,4-dihydropyridine-2-amines under neat conditions using inexpensive, readily available, natural, biodegradable lemon juice as a catalyst. The acidic reaction environment induced by lemon juice provided a superior catalytic performance, with a high reaction rate and high product yields, to those of a pool of Lewis and Brønsted acid catalysts. The wide substrate scope and functional-group tolerance permitted diversity creation with electronic and structural variations in a robust and operationally simple manner. The recoverability/reusability of the lemon juice catalyst and the easy purification of the end products by precipitation/filtration avoid the need for column chromatography or hazardous organic solvents and confirm that this is an environmentally benign sustainable technology. Moreover, a gram-scale operation and chemical modifications of the final products demonstrated some promising advantages.

An Unexpected Activity of a Minor Cannabinoid: Cannabicyclol (CBL) Is a Potent Positive Allosteric Modulator of Serotonin 5-HT1A Receptor.

Cannabicyclol ((±)-CBL), a minor phytocannabinoid, is largely unexplored, with its biological activity previously undocumented. We studied its conversion from cannabichromene (CBC) using various acidic catalysts. Montmorillonite (K30) in chloroform at room temperature had the highest yield (60%) with minimal byproducts. Key reaction conditions, such as solvent, temperature, and time, significantly impacted the yield. The structure of (±)-CBL was confirmed via X-ray crystallography. Stability studies showed that (±)-CBL and its MCT oil dilution remain stable at 25-40 °C for three months. Radioligand binding assays revealed high affinity of CBL for the 5-HT1A receptor but weak interaction with CB1 and CB2 receptors. At 10 μM and 1 μM, (±)-CBL inhibited [3H]-8-hydroxy-DPAT binding to 5-HT1A by 75% and 20%, respectively. Functional assays showed that (±)-CBL acts as a weak agonist at high concentrations but a potent positive allosteric modulator of serotonin-induced activation at low concentrations. At 4 μM, (±)-CBL increased serotonin-induced β-arrestin recruitment from 20% to 80%. This unique modulatory profile highlights the potential of (±)-CBL in drug discovery targeting serotonin receptors.

Low-temperature catalytic oxidation of ethanol over doped nickel phosphates.

This work is focused on the synthesis and performance of Ni3(PO4)2-based catalysts doped with Cu, Co, Mn, Ce, Zr, and Mg for the complete oxidation of ethanol, aiming at reducing emissions from ethanol-blended gasoline. Nickel phosphate was prepared via the co-precipitation method, followed by impregnation with the specified dopants. The catalysts were thoroughly characterized by XRD, N2-physisorption, XRF, FTIR and Raman spectroscopy, FESEM, NH3-TPD, CO2-TPD, and H2-TPR to explain their performance. All catalysts achieved complete ethanol conversion (100%) at a temperature below 320°C. The performance of the catalysts was strongly influenced by the dopant type of which Co, Ce, Mn, and Mg showed high CO2 selectivity (selectivity > 90% at 95% ethanol conversion temperature (T95)). The mechanism of oxidation is affected by the acido-basicity of the catalysts and the redox properties leading to a reaction through ethylene formation over the acid catalysts and acetaldehyde over the basic catalysts. The redox properties of the doped catalysts play a crucial role in enhancing the catalytic activity and selectivity toward CO₂, as the redox-active dopants facilitate the activation of oxygen species, which are essential for the complete oxidation of ethanol. In particular, Co and Ce demonstrated superior redox characteristics, facilitating the conversion of intermediate species and leading to higher CO2 selectivity while minimizing undesirable by-products.

Photoinduced Catalytic Alkylation of Active Methine Compounds with Nonactivated Alkenes Using Yttrium Triflate as a Lewis Acid Catalyst

Photoinduced catalytic alkylation reactions of active methine compounds with nonactivated alkenes have been developed using an organophotocatalyst, a metal Lewis acid, an arylthiol, and an amine base catalyst system. The alkylation reactions proceeded smoothly under ambient conditions with blue light irradiation, affording the desired products bearing quaternary carbon centers in high yields. Furthermore, enantioselective alkylation with an nonactivated alkene was achieved using a chiral Lewis acid.

Continuous-Flow Ritter Reaction for Sustainable Amide Synthesis Using a Recyclable m-Phenolsulfonic Acid-Formaldehyde Resin Catalyst.

Herein, a rapid and efficient continuous-flow synthesis of amides is described. The Ritter reaction, catalyzed by a reusable solid acid catalyst composed of m-phenolsulfonic acid-formaldehyde resin (PAFR II), was used to convert nitriles and alcohols to amides in up to 90% yield. The continuous-flow system facilitates short reaction times and maintains activity for several weeks. This method is scalable, environmentally sustainable, and enables catalyst recycling.

Chiral Phosphoric Acid-Catalyzed Enantioselective Synthesis of 2,2-Disubstituted 2,3-Dihydro-4-quinolones from Isatins and 2'-Aminoacetophenones.

Herein, we present the enantioselective synthesis of 2,3-dihydro-4-quinolones bearing chiral tetrasubstituted carbons from isatins and 2'-aminoacetophenones. The transformation is mediated by a chiral phosphoric acid catalyst and proceeds via an in situ generated ketimine and subsequent enantioselective intramolecular cyclization. The methodology features a broad scope and functional group tolerance with yields and enantioselectivities of up to 99% and 98% ee. Detailed density functional theory (DFT) calculations support the proposed reaction mechanism and the origin of asymmetric induction.

Magnetic nano-sized solid acid catalyst bearing sulfonic acid groups for biodiesel synthesis and oxidation of sulfides

In this study, the AlFe2O4@n-Pr@Et-SO3H heterogeneous catalyst was successfully synthesized and utilized to produce biodiesel from oleic acid through an esterification process and to oxidize sulfides. To examine the physicochemical characteristics of the AlFe2O4@n-Pr@Et-SO3H nanomaterial, a variety of advanced techniques were employed, including Fourier Transform infrared spectroscopy (FT-IR), Field emission scanning electron microscopy (FE-SEM), Energy dispersive X-ray spectroscopy (EDX), Vibrating sample magnetometer (VSM), Elemental Mapping, Transmission electron microscopy (TEM), Inductively coupled plasma (ICP), and X-ray diffraction (XRD). The AlFe2O4@n-Pr@Et-SO3H materials demonstrated excellent performance in both the esterification of oleic acid and the oxidation of sulfides. Moreover, the catalyst can be easily recovered and reused multiple times without a significant reduction in its effectiveness.

Highly Effective Catalytic and Modeling Kinetics of Acetylene Dimerization with a Phosphorus-Doped Activated Carbon-Bifunctional Solid Acid Catalyst

Highly Effective Catalytic and Modeling Kinetics of Acetylene Dimerization with a Phosphorus-Doped Activated Carbon-Bifunctional Solid Acid Catalyst

Highly Stereo- and Enantioselective Syntheses of δ-Alkyl-Substituted (Z)-Homoallylic Alcohols.

Highly stereo- and enantioselective synthesis of δ-alkyl-substituted (Z)-homoallylic alcohols via asymmetric allylation is developed. In the presence of a chiral phosphoric acid catalyst, allylation of aldehydes with α-substituted allylboronates provides δ-alkyl-substituted homoallylic alcohols with excellent (Z)-selectivities and enantioselectivities.

A new microporous organic-inorganic hybrid titanium phosphate for selective acetalization of glycerol.

We developed a novel strategy for synthesizing a highly acidic microporous hybrid titanium phosphate material (H-TiPOx) by incorporating 5-aminosalicylic acid (5-ASA) into the titanium phosphate framework. This new H-TiPOx serves as a Brønsted acid catalyst, exhibiting remarkable total surface acidity of 5.9 mmol g-1 and it efficiently catalyzes the acetalization of abundant biomass derived glycerol to solketal with over 99% selectivity.

Characterization of zeolitic imidazole framework (ZIF-8) catalyst for potential biodiesel production from waste cooking oil (WCO)

Heteropoly acids (HPAs) catalysts prove effective in waste cooking oil biodiesel production, considering their high density of Brønsted acidic sites, exhibit significant resilience to elevated levels of free fatty acid (FFA) and moisture content. However, the separation of HPA catalysts after biodiesel production is challenging due to their homogeneous catalytic nature. This study aims to develop magnetic vanadium-substituted HPAbased ZIF-8 composites to create a catalyst for biodiesel production from WCO that is more efficient and easier to separate. In this work, a range of analytical methods was utilized to characterize the catalyst, such as Fouriertransform infrared spectroscopy (FTIR), scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX), highresolution transmission electron microscopy (HRTEM), and a vibrating sample magnetometer (VSM). The successful incorporation of HPA acid into the magnetite ZIF-8 nanocomposite was indicated by prominent bands in the FTIR analysis, and this formation was further validated by EDX analysis. The VSM results also revealed that the nanocomposite has good magnetic responsiveness, facilitating catalyst separation and recycling. The magnetic ZIF-8 composites functionalized with H6PV3MoW8O40 demonstrated significant potential for sustainable biodiesel production from WCO.

Inverse analysis-guided development of acid-tolerant nanoporous high-entropy alloy catalysts for enhanced water-splitting performance

Through material-driven inverse analysis, the acid-tolerant high-entropy catalyst, composed of Al, Au, Ir, Nb, Pt, Rh, Ru, and Ta, exhibited superior catalytic activity and stability in acidic environments, outperforming Pt and IrO2 catalysts.

Asymmetric 'Clip-Cycle' synthesis of 3-spiropiperidines.

3-Spiropiperidines can be synthesized in up to 87% yield and 96 : 4 er using a two step 'Clip-Cycle' approach. The 'Clip' stage of this method is based on efficient and highly E-selective cross metathesis of N-Cbz-protected 1-amino-hex-5-enes with a thioacrylate. This is followed by the 'Cycle' step, in which an intramolecular asymmetric aza-Michael cyclization is promoted by a chiral phosphoric acid catalyst.

Functionalized covalent organic frameworks for catalytic conversion of biomass-derived xylan to furfural.

A direct synthesis strategy was employed to prepare functionalized COFs enriched with acidic sites, using various precursor monomers. The functionalized COFs were applied in the catalytic conversion of biomass-derived xylan to furfural in the liquid phase. The study further assessed the recyclability and reusability of these COFs, explored the relationship between their structural features and catalytic performance, and investigated the reaction mechanism underlying the COF-catalyzed conversion of xylan to furfural. The results revealed the successful solvothermal synthesis of four COFs (COF-LZU1, TP-PA, TB-DAB, and TP-DAB). Among them, TP-DAB exhibited the highest acidity, reaching 2.092mmol/g, due to its rich content of -OH and -COOH. Additionally, TP-DAB demonstrated a well-developed porous structure and excellent thermal stability, essential characteristics for a highly efficient solid acid catalyst. When employed as a catalyst in a mixed solvent system of H2O/THF at 160°C for 180min, TP-DAB achieved complete xylan conversion with furfural yield of 63.49%. Moreover, TP-DAB maintained good stability and reusability, being effective for at least five cycles. This study presents a novel and highly effective green catalyst for the sustainable conversion of biomass-derived sugars into furfural, providing new avenues for the efficient conversion of biomass into fine chemicals.

Highly Efficient and Recycling Acid-Catalysis using High-Temperature Resistant O/W Emulsion Stabilized by Dodecyl Phosphonic Acid

Acid-catalyzed reactions play an important role in the field of organic synthesis in synthesizing a large number of organic compounds. However, conventional acid catalysts have many shortcomings, such as low...

Modulating the crystal phase of Zr-based solid acid catalysts to boost the synthesis of 9,9-bis(4-hydroxyphenyl)fluorene

The crystal phase of Zr-based solid acid was tailored by two-step precipitation for strongly bonding with sulfate groups. The tetragonal ZrO2 was coordinated with sulfate groups to enhance its acidity and thus boosted BHPF synthesis.

Modular assembly of chiral multisubstituted tetrahydropyrans through a cascade asymmetric aldehyde allylboration/oxa-cyclization by a chiral phosphoric acid

Two cascade processes based on asymmetric aldehyde allylboration by a chiral phosphoric acid catalyst have been established for creating chiral multisubstituted tetrahydropyrans.

1,4-Dihydropyrrolo[3,2-b]pyrroles with Two Embedded Heptagons via Alkyne Annulation.

Drastic changes to the character of the acidic catalyst enable the reversal of the double alkyne benzannulation reaction output. In the presence of a strong Brønsted acid, 1,4-dihydropyrrolopyrroles undergo transformation which results in the formation of two 7-membered rings. Computational studies imply that the thermodynamically unfavored 7-membered ring is forged via the kinetically favored 6-endo-dig attack of a protonated alkyne at the position 3a of pyrrolopyrrole followed by a 1,2-vinyl shift.

Laser scribed proton exchange membranes for enhanced fuel cell performance and stability

High-temperature proton exchange membrane fuel cells (HT-PEMFCs) offer solutions to challenges intrinsic to low-temperature PEMFCs, such as complex water management, fuel inflexibility, and thermal integration. However, they are hindered by phosphoric acid (PA) leaching and catalyst migration, which destabilize the critical three-phase interface within the membrane electrode assembly (MEA). This study presents an innovative approach to enhance HT-PEMFC performance through membrane modification using picosecond laser scribing, which optimises the three-phase interface by forming a graphene-like structure that mitigates PA leaching. Our results demonstrate that laser-induced modification of PA-doped membranes, particularly on the cathode side, significantly enhances the performance and durability of HT-PEMFCs, achieving a peak power density of 817.2 mW cm⁻² after accelerated stress testing, representing a notable 58.2% increase compared to untreated membranes. Furthermore, a comprehensive three-dimensional multi-physics model, based on X-ray micro-computed tomography data, was employed to visualise and quantify the impact of this laser treatment on the dynamic electrochemical processes within the MEA. Hence, this work provides both a scalable methodology to stabilise an important future membrane technology, and a clear mechanistic understanding of how this targeted laser modification acts to optimise the three-phase interface of HT-PEMFCs, which can have impact across a wide array of applications.