Activation and Utilization of CO₂ Using Ionic Liquid or Amine-Functionalized Basic Nanocrystalline Zeolites for the Synthesis of Cyclic Carbonates and Quinazoline-2,4(1<i>H</i>,3<i>H</i>)‑dione

CO₂ was activated and used as a reactant for the preparation of cyclic carbonates and quinazoline-2,4­(1<i>H</i>,3<i>H</i>)-dione using functionalized basic nanocrystalline zeolite Nano-ZSM-5 as catalysts. Nano-ZSM-5 was treated with aqueous NH₃ solution to prepare basic Nano-ZSM-5. The surface basicity of the basic Nano-ZSM-5 was systematically varied by the surface modification with various amines and basic ionic liquids. Powder X-ray diffraction, N₂ adsorption–desorption, scanning/transmission electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, ²⁹Si and ¹³C cross polarized-magic angle spin NMR, elemental analysis, and temperature-programmed desorption techniques were used to characterize the materials. Kinetic (rate constant, activation energy) and thermodynamic parameters (change in enthalpy, free energy, and entropy) were calculated for the cycloaddition reaction of CO₂ to epichlorohydrin and 2-aminobenzonitrile by varying the reaction parameters. Basic Nano-ZSM-5 functionalized with methylimidazolium hydroxide exhibited remarkable high activity and selectivity in the preparation of cyclic carbonates and quinazoline-2,4­(1<i>H</i>,3<i>H</i>)-dione. The catalyst was separated and recycled with no significant loss in the activity. In this study mesoporous zeolite was made basic and then the basic property of the nanocrystalline zeolite surface was systemically tuned using various functional amines and ionic liquids under one umbrella

Octahedral MnO₂ Molecular Sieve-Decorated <i>Meso</i>-ZSM‑5 Catalyst for Eco-Friendly Synthesis of Pyrazoles and Carbamates

Octahedral MnO₂ molecular sieve (hereafter designated as OMS) was prepared in the presence of urea, and mesoporous ZSM-5 (designated as <i>Meso</i>-ZSM-5) was prepared using propyltriethoxysilane as additive under hydrothermal synthesis condition. OMS-decorated <i>Meso</i>-ZSM-5 was prepared by heating a grounded mixture of OMS and <i>Meso</i>-ZSM-5. Powder X-ray diffraction, N₂-sorption, SEM, TEM, thermogravimetric analysis, FT-IR, diffuse reflectance UV–vis spectroscopy, and NH₃ and CO₂ temperature-programmed desorption techniques were used to characterize the material. The catalyst was demonstrated in a one-pot, one-step synthesis of pyrazoles via cyclization followed by dehydrogenation as the key reaction steps. Synthesis of carbamates by the reaction of cyclic and acyclic carbonates/di-<i>tert</i>-butyl dicarbonate with amines was another important application of this catalyst. Catalyst exhibited efficient recyclability. No leaching of active species took place even after five recycles. A strong interface between OMS and <i>Meso</i>-ZSM-5 imparts strong acidity and distinguished activity in the synthesis of pyrazole heterocycles and organic carbamates

Simple and Economical Synthesis of Alkyl Phenyl Ethers by the Reaction of Phenols and Alkyl Esters Using Nanocrystalline Beta

A simple, economical, and recyclable catalytic route is developed for the synthesis of alkyl phenyl ethers by the liquid phase reaction of phenol derivatives with alkyl esters using conventional and nanocrystalline zeolite Beta. A wide range of alkyl phenyl ethers can be prepared using this catalytic protocol. Nanocrystalline zeolite Beta exhibited higher activity than conventional zeolite Beta

Synthesis of γ‑Valerolactone from Levulinic Acid with Co/NC, and from Furfural via Cascade Reaction Using Co/NC and H‑Beta

γ-Valerolactone (GVL) has transpired as an ecofriendly solvent, a promising fuel additive, and a precursor to valuable chemicals. The study explores an approach to GVL synthesis by employing non-noble metals in contrast to conventional methods involving noble metals. The selective hydrogenation of levulinic acid (LA) and levulinate esters offers a pathway to GVL production, while the direct transformation from furfural (FA) enhances its potential. The study focuses on 3d transition metal-based N-doped carbon catalysts, highlighting Co/NC as the most effective catalyst for LA to GVL hydrogenation, yielding ∼100% GVL. The catalyst was also employed in a one-pot, three-step cascade reaction: FA hydrogenation to furfuryl alcohol (FOL) was performed using 10% Co/NC, ethanolysis of FOL to ethyl levulinate (EL) was facilitated by H-β, and EL hydrogenation to GVL was performed using 10% Co/NC. Each step was optimized independently. The cascade reaction was executed at 140 °C for 12 h through a comprehensive approach, achieving a noteworthy 92.1% GVL yield from FA, which was further upcycled to the gram scale, offering 86% of the final GVL yield. The catalyst characterization, catalytic activity data, and control experiments culminate in the proposed LA to GVL transformation mechanisms and the one-pot, three-step cascade FA to GVL conversion. The research significantly contributes to advancing sustainable GVL production and its multifaceted applications

One-Step Dual Template Mediated Synthesis of Nanocrystalline Zeolites of Different Framework Structures

A novel, dual template mediated, one-step direct synthesis route is reported here for the preparation of nanocrystalline zeolites of different framework structures (such as ZSM-5, mordenite, and sodalite). In this synthesis strategy, a suitably designed dicationic/tetra-cationic soft template was used along with a conventional zeolite structure director to obtain nanocrystalline zeolites with nanosheet morphology. Nanocrystalline zeolites exhibited large surface area, pore volume, and intercrystalline mesopores. The long hydrophobic chain containing a multiammonium template cooperatively participates in the zeolite crystallization process along with a conventional microporous zeolite structure director to form the ultrathin microporous zeolite framework, while the hydrophobic interaction between the long chains restricted the excessive growth of zeolites and induced the formation of intercrystalline mesopores. Nanocrystalline zeolites exhibited exceptionally high activity in the acid-catalyzed reactions involving large molecules when compared with conventional zeolites. This synthesis strategy can be extended for the preparation of zeolites of different framework structures or other porous materials in the future

Highly Efficient CeO₂ Decorated Nano-ZSM‑5 Catalyst for Electrochemical Oxidation of Methanol

Cerium oxide (CeO₂) decorated nanocrystalline zeolite (Nano-ZSM-5) nanocomposites with different weight ratios were prepared by the calcination of a physical mixture of nanocrystalline CeO₂ and Nano-ZSM-5. Materials were characterized by the complementary combination of X-ray diffraction, N₂-adsorption, transmission electron microscopic, and X-ray photoelectron spectroscopic techniques. The material was investigated as a precious-metal-free electrode catalyst for methanol oxidation. The electrochemical oxidation of methanol was investigated at a CeO₂/Nano-ZSM-5 modified glassy-carbon electrode in alkaline medium using electrochemical impedance spectroscopy, cyclic voltammetry, and chronoamperometry. Comparative investigations were made with commercial Pt(20%)/C catalyst with respect to current density, stability, and CO tolerance capacity. CeO₂/Nano-ZSM-5 with a weight ratio of 30% exhibited remarkably high electrocatalytic activity in the methanol oxidation in comparison to nanocrystalline CeO₂ and commercial Pt (20%)/C catalyst. The material was found to exhibit stable electrocatalytic activity even after 1000 cycles. High electrocatalytic activity in the methanol oxidation can be attributed to the synergistic contribution provided by CeO₂ nanocrystals and Brønsted acidity of the high-surface-area Nano-ZSM-5. Results demonstrate that the excellent current density and high stability of CeO₂/Nano-ZSM-5 would be valuable for its commercial application in direct methanol fuel cells

Highly Efficient Nanocrystalline Zirconosilicate Catalysts for the Aminolysis, Alcoholysis, and Hydroamination Reactions

Nanocrystalline zirconosilicates and titanosilicates with MFI framework structure were hydrothermally synthesized by the addition of organosilanes in the synthesis composition of conventional zirconosilicate and titanosilicate materials. Materials were characterized by a complementary combination of X-ray diffraction, nitrogen sorption, scanning/transmission electron microscopy (S/TEM), ammonia temperature-programmed desorption (TPD), Fourier transform infrared (FT-IR) spectroscopy, and ultraviolet–visible (UV-vis) spectroscopic investigations. Nanocrystalline zeolite catalysts of the present study are reusable. They exhibit significantly higher catalytic activities in aminolysis and alcoholysis compared with the hitherto known catalysts. A range of β-amino alcohols/β-alkoxy alcohols with high regioselectivity were synthesized using zirconosilicates. Application of these materials was also extended in the synthesis of aminoesters by the hydroamination reaction of methyl acrylates and amines. Structure activity relationship was explained based on acidity measurements, reactivity of amines/alcohols, and adsorption of reactants on catalysts

Stimulating the Visible-Light Catalytic Activity of Bi₂MoO₆ Nanoplates by Embedding Carbon Dots for the Efficient Oxidation, Cascade Reaction, and Photoelectrochemical O₂ Evolution

The present work demonstrates the facile synthesis and applications of carbon dots (CD)-embedded Bi₂MoO₆ nanoplates photocatalyst in the oxidative coupling of amines and oxidation of toluene and ethylbenzene. The synthetic protocol is applied to afford good yields of benzimidazole/benzothiazole via the cascade reaction between benzylamine and <i>o</i>-aminothiophenol/<i>o</i>-phenylenediamine. These photocatalytic reactions are performed under very mild conditions using the household light-emitting diode bulb as a light source and O₂ (1 atm). The CD-embedded, 2.4 wt % CD/Bi₂MoO₆ exhibits the best photocatalytic activity. Impressive visible-light absorbance coefficient, quantum confinement, photoluminescence up-conversion, and stable photoelectrochemical properties of CD are contemplating the excellent photocatalytic activity of CD/Bi₂MoO₆ than the pristine Bi₂MoO₆. Generation and influence of various reactive species in these catalytic reactions are investigated by radical scavenging, fluorescence spectroscopy, and cyclic voltammetric (CV) analysis. Both qualitative and quantitative estimation of the in situ generated H₂O₂ in the photocatalytic oxidative coupling of amines was ascertained using CV and redox titration, respectively. Further, the influence of substitution in the benzylamine and involvement of the carbocations are confirmed using Hammett plot. The developed catalysts are also used as photoanode for O₂ evolution from water oxidation in a photoelectrochemical (PEC) cell. Several PEC techniques evaluate the PEC activity of the photoanodes. The reactivity order for various substituted benzylamine and the involvement of reactive oxygen species (O₂·^–) in the oxidation reaction was obtained and confirmed from the band edge potentials of the best photocatalyst using Mott–Schottky analysis. Efficient catalytic recyclability and photostability are additional important features of the present investigation. This study provides a feasible alternative to the development of non-noble metal (CD)-based nanocomposite photocatalysts that can manifest important photocatalytic and photoelectrocatalytic applications in chemical synthesis and solar fuel production

Selective Oxidation of Biomass-Derived Alcohols and Aromatic and Aliphatic Alcohols to Aldehydes with O₂/Air Using a RuO₂‑Supported Mn₃O₄ Catalyst

Selective catalytic oxidation of carbohydrate-derived 5-hydroxymethylfurfural, furfuryl alcohol, and various aromatic and aliphatic compounds to the corresponding aldehyde is a challenging task. The development of a sustainable heterogeneous catalyst is crucial in achieving high selectivity for the desired aldehyde, especially using O₂ or air. In this study, a RuO₂-supported Mn₃O₄ catalyst is reported for the selective oxidation reaction. Treatment of MnO₂ molecular sieves with RuCl₃ in aqueous formaldehyde solution gives a new type of RuO₂-supported Mn₃O₄ catalyst. Detailed catalyst characterization using powder X-ray diffraction, N₂ adsorption, scanning and transmission electron microscopes, diffuse reflectance UV–visible spectrometer, and X-ray photoelectron spectroscopy proves that the RuO₂ species are dispersed on the highly crystalline Mn₃O₄ surface. This catalytic conversion process involves molecular oxygen or air (flow, 10 mL/min) as an oxidant. No external oxidizing reagent, additive, or cocatalyst is required to carry out this transformation. This oxidation protocol affords 2,5-diformylfuran, 2-formylfuran, and other aromatic and aliphatic aldehydes in good to excellent yield (70–99%). Moreover, the catalyst is easily recycled and reused without any loss in the catalytic activity

An Efficient, Visible Light Driven, Selective Oxidation of Aromatic Alcohols and Amines with O₂ Using BiVO₄/g‑C₃N₄ Nanocomposite: A Systematic and Comprehensive Study toward the Development of a Photocatalytic Process

In this study, BiVO₄ was prepared by a hydrothermal synthesis route in the presence of sodium dodecyl sulfate using aqueous NH₃ as precipitant. g-C₃N₄ was prepared by a combustion method using melamine. In order to develop highly efficient photocatalyst, a heterojunction catalyst based on g-C₃N₄ and BiVO₄ was prepared. Different amounts of BiVO₄ and g-C₃N₄ were mixed and annealed to obtain heterojunction photocatalysts. FeVO₄ and LaVO₄ were also prepared for the comparative catalytic investigation. Catalysts were characterized by a series of complementary combinations of powder X-ray diffraction, thermogravimetric analysis, elemental analysis, N₂ adsorption–desorption, scanning electron microscopy, transmission electron microscopy, temperature-programmed desorption of NH₃ and CO₂, diffuse reflectance ultraviolet visible spectroscopy, X-ray photoelectron spectroscopy, photoluminescence spectroscopy, and photoelectrochemical studies. Catalysts were investigated in the visible light driven oxidation of benzyl alcohol, benzyl amine, and aniline with O₂. In order to propose the electrons, holes, and radicals mediated reaction pathways, reactions were performed in the presence of an electron/hole/radical scavenger. Further, in order to confirm various products formed during the photocatalytic oxidation of benzyl alcohol, benzyl amine, and aniline, several model reactions were carried out. Based on the results obtained, the reaction mechanism and structure–activity relationship were established