Solvent-free Conditions Research Articles

Solvent-free deoxygenation of biolipid into liquid alkanes over bifunctional Ni/B2O3-ZrO2 catalyst

The efficient deoxygenation of renewable biolipids into liquid alkanes within the diesel range is a key protocol for producing high-quality biofuels. In this work, the conversion of methyl palmitate and raw palm oil were accomplished utilizing a bifunctional catalyst of Ni catalysts supported on B2O3-ZrO2 under solvent-free conditions. Among various Ni loading ratios investigated, the catalyst featuring a 10 % Ni loading achieved 100 % conversion of methyl palmitate and 84.4 % of liquid yield, with approximately 65 % being C15 alkanes. Additionally, more than 91 % of hydrocarbons were also generated from raw palm oil. These results can be attributed to the synergistic interplay between the acid sites, following B2O3 modification, and the presence of Ni species. Furthermore, the analysis of product distribution, gas product detection and the kinetics calculation strongly supports that the deoxygenation process of methyl palmitate primarily follows the hydrodecarbonylation route, leading to the predominant formation of C15 alkane.

The Facile Synthesis of Nickel-Doped Composite Magnetic Ni@CoO@ZIF-67 as an Efficient Heterogeneous Catalyst for the Ring-Opening Polymerization of L-Lactide

The ring-opening polymerization of L-lactide is a crucial route for producing biodegradable polylactides (PLAs). Developing an efficient catalyst for this process poses significant challenges. Herein, we report the successful incorporation of nickel during the crystallization of ZIF-67, the derivation of the abundant and stable CoO source, to obtain the composite magnetic Ni@CoO@ZIF-67 using the solid-state thermal (SST) method. The characterization of the resulting materials revealed that nickel atoms are well dispersed in the composite CoO@ZIF-67, imparting additional magnetic properties. The composite Ni@CoO@ZIF-67 demonstrated superior performance as a heterogeneous catalyst for the ring-opening polymerization of L-lactide compared to reference materials such as Ni-Hmim, CoO, ZIF-67, and CoO@ZIF-67. Furthermore, the magnetic property of Ni@CoO@ZIF-67 offers practical advantages, enabling easier separation and recycling of the catalyst. Notably, the SST method facilitates the single-step synthesis of composite magnetic Ni@CoO@ZIF-67 under solvent-free conditions, representing a significant advancement in catalyst development. This approach not only simplifies the synthesis process but also inspires further developments of heterogeneous magnetic catalysts for a variety of effective and diverse reactions.

Fe3O4@SiO2@NTMPThio-Cu: a sustainable and eco-friendly approach for the synthesis of heterocycle derivatives using a novel dendrimer template nanocatalyst

In this research, Fe3O4@SiO2@NTMPThio-Cu was introduced as a novel and green heterogeneous nanocatalyst with a dendrimer template that is environmentally friendly and reusable based on Fe3O4@SiO2. In this way, magnetic silica nanoparticles were first modified with cyanuric chloride, followed by melamine and thiosemicarbazide, and ultimately, it’s decorated with the cost-effective metal copper. The synthesized nanocatalyst was characterized by various analyses such as FT-IR, XRD, SEM, TGA, and EDX. The efficiency of Fe3O4@SiO2@NTMPThio-Cu was measured in one-pot synthesis of xanthene and spirooxindole-pyran derivatives under mild solvent-free conditions. High efficiency, excellent yield of products, mild reaction conditions, simple operation, no use of toxic organic solvents, and reusability of this catalyst increase the attractiveness of this technique for large-scale environmentally friendly operations.

Highly efficient capture and conversion of CO2 into cyclic carbonates from actual flue gas under atmospheric pressure

Chemical conversion of CO2 to cyclic carbonates is one of the most attractive strategies for CO2 capture and storage utilization. Herein, a binary organocatalyst of 3-aminobenzylalcohol/n-Bu4NI was used to gently catalyze the insertion of CO2 into the terminal/internal epoxides to generate cyclic carbonates under metal-free and solvent-free conditions. Twelve representative terminal epoxides reacted with CO2 to achieve excellent cyclic carbonate yields of up to 98.3 % at 30 °C and 1 atm CO2 and six low activity internal di-substituted epoxides were converted to corresponding cyclic carbonates with yields of up to 96.2 %. Experiments on actual flue gas and water resistance revealed the potential industrial value of this binary organocatalyst. The yield of cyclic carbonate reached 99 % by using actual flue gas under very mild conditions of 60 °C and 1 atm. The results of 4-fold epoxide amplification experiment showed that the residual CO2 in the flue gas was only 793 ppm after reaction at 1 atm and 60 °C, indicating the good CO2 capture and conversion ability. Reaction kinetics and catalytic mechanism of the cycloaddition were investigated in detail. The synergistic effect among functional groups of catalysts on substrates is the essential factor for the high activity of the catalyst.

Solvent-free synthesis of polysilane-carbazole – A green route to develop fluorescent polysilanes with amplified emission characteristics via bridge intramolecular charge transfer effect

This work presents the synthesis of a new polysilane-carbazole structure (PSCB) by hydrosilylation in solvent-free conditions. For this purpose a polyhydrosilane (PSH) with a high content in methylhydrosilyl groups was mixed with 2-(((2-(9H-carbazol-9-yl)ethoxy)carbonyl)amino)ethyl methacrylate (CB) and triturated in the presence of Karstedt catalyst. The reaction proceeds smoothly in normal conditions of pressure and temperature in a dry atmosphere. The chemical structure of the resulted polymer was determined using Fourier-transform infrared (FTIR) and proton nuclear magnetic resonance (1H NMR) spectroscopies. Gel permeation chromatography (GPC) analysis proved the completion of the addition reaction in high yields. The computational analysis reveals the electronic structures of both CB and the PSCB molecule and highlights the significance of conformational effects on electronic structure and emission properties. The carbazole moiety acts as an electron donor, while the polysilane chain serves as an acceptor, enabling an intra-molecular through bridge charge transfer. Fluorescence measurements validate the unique structure, demonstrating an amplified emission due to the cumulative effect of the polysilane chain. The polysilane-carbazole polymer holds promise for various applications, emphasizing its potential in optoelectronic devices and sensing technologies.

PVP-assisted in-situ self-assembly hierarchical BiOCl with oxygen vacancies for efficient photocatalytic oxidation of cyclohexane under air in solvent-free conditions

Cyclohexane (CHA) selective oxidation reactions are crucial in designing advanced organic intermediates but suffering from very challenges as the products of KA oil (cyclohexanol and cyclohexanone) are more readily oxidized to CO2. Herein, we report that a polyvinylpyrrolidone (PVP) coating of fluffy self-assembled morphology of BiOCl by nanosheets with exposed {001} facets are synthesized via the solvothermal method. Moreover, the as-synthesized hierarchical BiOCl exhibits a significant presence of in-situ produced oxygen vacancies during photocatalysis, thereby facilitating efficient CHA oxidation to KA oil with air as an oxidant in solvent-free at room temperature. The crystallinity, micromorphology, and electronic structure of BiOCl can be significantly influenced by the concentration of NH4Cl and PVP. In the photocatalytic oxidation, oxygen vacancies act as traps to inhibit electrons and holes recombination and adsorb-activate the oxygen molecule, producing h+ and ·O2− radical to achieve 466.7 μmol of KA oil (340.8 μmol of cyclohexanone and 125.9 μmol of cyclohexanol) with a selectivity of 93.9 %. The ∙OH radicals play a predominant role in the production of CHA-one. After conducting 5 experimental cycles, a consistent yield of 92 % towards KA oil and unchanged selectivity can still be maintained. The excellent photocatalytic performance can be attributed to the enhanced photo-absorption and narrow energy gap, abundant oxygen vacancies, high exposed {001} facets, smaller size and large specific surface area, and efficient electron-hole separation. The present work sheds light on the synergistic effect of PVP coating and in-situ formed oxygen vacancies on enhancing photocatalytic activity of Bi-based materials.

Solvent-free Simplistic Synthesis of Bis(indolyl) Methanes Using Tulsion®-8052 MP Resin

Abstract: Tulsion®-8052 MP cation resin catalyst accelerates chemical reaction by creating a suitable environment for the aldehyde and indole reactants to interact and form desired product bis(indolyl) methanes in solvent-free room temperature conditions. The uniqueness of this catalytic method is that it is eco-friendly, recyclable, selective, and operates on a variety of functional groups with good to excellent yield at room temperature conditions without the use of any hazardous solvents, high temperature, and inert atmosphere.

Aqueous organometallic synthesis: Ammonia borane (NH3.BH3) as a convenient metal-free reagent for the reduction of ferrocenyl and ferrocenium carbonyl derivatives in water

Herein, we present a green methodology for the reduction of ferrocene-derived aldehydes and ketones to their respective alcohols, employing ammonia borane as the reducing agent and neat water as the solvent. We also report the deoxygenation of the same precursors to the corresponding alkyl ferrocenes when reactions are performed under solvent-free conditions. Both methods, applicable to various carbonyl derivatives of ferrocene, give product yields in the range of 40–95 % and, in most cases, a product purification that does not require column chromatography. The investigation for the deoxygenation of alkyl derivatives was extended to the cobalt sandwich compound –[(COCH3)C5H4]Co(η4-C4Ph4) and ketone derivatives of ruthenocene as well. Ammonia borane has also been found to be useful as a convenient reducing reagent for the selective reduction of ferrocenium compounds to their respective ferrocene derivatives at room temperature in water medium. Control experiments have been carried out to explore the mechanistic details of these reactions.

A new DES-mediated synthesis of Henna-based benzopyranophenazines and benzoxanthenetriones

MTPPBr/THFTCA-DES was prepared as a new deep eutectic solvent (DES) from a mixture (molar ratio 7:3) of methyltriphenyl-phosphonium bromide (MTPPBr) and tetrahydrofuran-2,3,4,5-tetra-carboxylic acid (THFTCA), and characterized with various spectroscopic techniques, densitometer, and eutectic point. Then, it was used as a new and powerful catalyst for the synthesis of two sets of biologically important compounds, namely the Henna-based benzopyranophenazines and benzoxan-thenetriones. Solvent-free conditions, short reaction time, high efficiency, and easy recycling and separation of the DES catalyst are among the most important features of the presented method. Also, there is a nice consistency between the proposed structure of the DES compound, the integration values of the 1H NMR peaks, and the ratio of MTPPBr to THFTCA obtained from the eutectic point phase diagram. In addition, the reduction of peak splitting patterns in DES compared to the two primary materials can be good evidence of the formation of hydrogen bonds between the two components.

Natural product synthesis by a nanoporous In-MOF Catalyst: Crystallographic insight by incorporating substrate inside its nanopores

Metal-organic frameworks (MOFs) are promising candidates as nanoporous heterogeneous catalysts over other solid catalysts. Herein, utilizing a new tetra-acid ligand and employing high-valent Indium metal source we have strategically developed a 3D robust nanoporous framework, IITKGP-53, which retained its crystallinity over a wide range of pH solutions (2–12). Considering the green synthesis approach IITKGP-53 was explored as a heterogeneous catalyst toward one-pot three-component Strecker reaction under solvent-free condition, with low catalyst loading for a broad range of substrates. Considering practical utility, biologically important natural product, Girgensohnine, was synthesized for the first time by using this catalyst with excellent conversion rate. The substrate binding sites inside the nanopores and host–guest interactions were verified crystallographically by obtaining a substrate inside nanopores of this MOF (aniline@IITKGP-53) and computational modeling. An in-depth theoretical investigation unveiled the most plausible transition states for the first time. This study inaugurates the usage of nanoporous MOFs as heterogeneous catalysts for natural product synthesis.

Efficacy of tethered Pyridinium-Based ionic liquid immobilized on Zn-MOF-NH2 for effectively converting CO2 into cyclic carbonates under Co-Catalyst-free and solvent-free conditions

A new bifunctional heterogeneous catalyst system was developed by immobilization of pyridinium-based ionic liquid on Zn-MOF-NH2 to produce an IL-supported Zn-MOF-NH2 catalyst. The dual-functional one-component system, including both Lewis acid sites and IL functional sites, showed high catalytic activity for the CO2-epoxide cycloaddition reactions under mild solvent-free conditions. Different techniques such as FE-SEM, EDX, FT-IR, XRD, and BET were applied to characterize of the as-prepared catalyst. This efficient low-leaching catalyst system is separated by centrifugation and can be reused successfully for four successive cycles without altering the catalytic activity in CO2 epoxidation to cyclic carbonates. Due to the wide variety seen in both metal–organic frameworks (MOFs) and ionic liquids (ILs), we believe that this research represents a significant step forward in the potential applications of synthetic modification methods within MOFs.

Photocatalytic Tandem Protocol for the Synthesis of Bis(indolyl)methanes using Cu-g-C3N4-Imine Decorated on TiO2 Nanoparticles under Visible Light Irradiation.

In this article, the visible-light-assisted photocatalytic activity of TiO2 nanoparticles functionalized with Cu(II) g-C3N4-imine was exploited for aerobic oxidation of alcohols to aldehydes followed by condensation with indoles in the presence of 2,2,6,6-tetramethylpiperidinyloxy to present a one-pot tandem strategy for the synthesis of bis(indolyl)methanes (BIMs) under solvent-free conditions. The synergistic effect between the components to improve the photocatalytic activity of the as-prepared Cu-g-C3N4-imine/TiO2 nanoparticles resulting from electron-hole separation was approved by PL spectroscopy. Moreover, action spectra showed a light-dependent photocatalysis with effective visible-light responsivity of the photocatalyst. The present method includes different aspects of green chemistry: one-pot tandem synthesis of a variety of BIMs using alcohols that are less toxic, more available, more economical, and more stable than aldehydes; removing the byproducts resulting from overoxidation of alcohols and polymerization of aldehydes and indoles; the use of air as a safe oxidant; visible light as a safe energy source; and solvent-free conditions. A reusability test demonstrated that the catalyst retained its efficiency even after five runs.

Synthesis of ozonides mediated by molecular sieve under solvent-free conditions

An efficient method for the direct synthesis of ozonides via the reaction of alkenes with an ozone stream under solvent-free conditions is described. In this study, the alkene substrates were loaded over a roughly ground molecular sieve and exposed to an ozone stream to give the corresponding ozonides. The new synthetic protocol was successfully applied to the synthesis of various substituted ozonides in good yields.

Stable ionic liquid/Zr-MOF co-modified silica microspheres: Facile construction strategy and promising chromatographic applications

The stability of porous metal-organic frameworks (MOFs) as ideal materials for adsorption and separation has always been a key concern. In this study, an ionic liquid (IL) with excellent properties synthesized under solvent-free conditions was used to modify Zr-MOF@SiO2 for the first time to enhance the stability and improve the separation ability of Zr-MOF@SiO2 for chromatographic applications. The IL serves a dual purpose of supporting the backbone structure of Zr-MOF and acting as a ligand to coordinate with Zr(IV). This facile construction strategy ensures that the overall structural framework of the IL/Zr-MOF composite is more stable. Additionally, the presence of IL with imidazolium and carboxyl groups can facilitate efficient chromatographic separation by providing multiple interaction mechanisms. The results shows that the separation performance of the IL/Zr-MOF composite is significantly superior to that of the original Zr-MOF. Furthermore, the obtained new IL/Zr-MOF@SiO2 column exhibits appreciable stability, repeatability and reproducibility, which also performs well in the analysis of real samples with no significant matrix effects, demonstrating good reliability of the developed method. This study proposes a facile strategy for cleverly synthesizing a novel IL/Zr-MOF@SiO2 as an efficient chromatographic separation material, thereby potentially broadening the application of Zr-MOF in separation science. The facile preparation and promising application of IL/Zr-MOF may also offer a new possibility for employing MOF-based composite materials as effective liquid chromatographic stationary phases.

Synthesis and characterization of bagasse cellulose-based quaternary ammonium peroxyphosphotungstate and their catalytic properties for cyclohexene oxidation in the absence of any solvent

Bagasse cellulose, an industrial waste byproduct of sugar production, was demonstrated to be a viable solid support for a solid-phase ionic oxidation catalyst enabling organic solvent-free aqueous reaction conditions and facile catalyst recovery. Bagasse cellulose-supported quaternary ammonium peroxyphosphotungstate was synthesized from bagasse cellulose-supported quaternary ammonium chloride, phosphotungstic acid, and hydrogen peroxide. The chemical structure of this material was characterized by SEM, XRD, FT-IR, XPS, and 13C NMR, revealing stability of the cellulose matrix to the catalyst loading conditions and effective dispersion of the acicular catalyst crystals throughout the matrix. High catalytic activity of this synthetic complex was demonstrated in the oxidation of cyclohexene to 1,2-cyclohexanediol with hydrogen peroxide in the absence of solvent. Optimized conditions providing trans-1,2-cyclohexanediol with 86.2 % selectivity were 12 wt% catalyst and 4 mL/g 30 % H2O2 (vs. cyclohexene) at 50 °C for 10 h.

Silver Complex Bearing N-Heterocyclic Carbene Bidentate Chelating Ligand as an Efficient Catalyst in Solvent-Free KA2 Coupling.

We report a synthesis of silver complexes bearing chelating bidentate N-heterocyclic carbene, with various substitutions at the terminal positions of the imidazole moiety of the NHC units. The long aliphatic substituents proved to be beneficial in terms of the synthetic efficiency of the complexes, compared to previously reported methyl substitution. The complexes demonstrated excellent suitability for the KA2 coupling reaction, providing quaternary carbon-containing propargylic amines in yields up to 95 %, under solvent-free conditions. The method showed high tolerance for a wide range of substrates, including naturally occurring ketones, underscoring its practicality. To our knowledge, this represents the first use of a well-defined silver species in KA2 coupling, marking an advancement in the field.

Talc: A natural mineral base catalyst for the one pot synthesis of bis(pyrazolyl)methane derivatives under thermal and solvent-free conditions

In this work, we were decontaminated the ore to extract the talc, directly. Then, we used talc as a heterogeneous basic catalyst for one pot synthesis of bis(pyrazolyl)methane derivatives via the condensation of ethylacetoacetate, hydrazine hydrate and aromatic aldehyde derivatives under thermal and solvent-free conditions. This solid type of catalyst was identified by fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), energy-dispersive X-ray spectroscopy (EDS), EDS mapping and Brunauer–Emmett–Teller (BET) theory. Heterogeneous and solvent-free conditions, catalyst recyclability, high yields of the products and short reaction times are some advantages of this method. The reusability of the catalyst was examined for five times and it was successfully used in each run without any significant decreasing in its activity.

Malic Acid as a Green Catalyst for the N-Boc Protection under Solvent-free Condition

Abstract: A protocol for the Chemoselective N-Boc protection of various types of amines has been developed. This includes heteroaryl, aliphatic, and alicyclic amines. The process makes use of malic acid as a catalyst and operates efficiently at ambient temperature without the need for solvents. This technique has been proven to effectively protect a wide range of functionalized amines containing both electron-donating and electron-withdrawing substituents. The benefits of this method include its fast reaction rate, high selectivity, excellent yield, catalyst recyclability, and environmentally friendly conditions.

Catalytic coupling of CO2 and epoxides with metal substituted Keggin based Hybrid Materials

Three hybrid catalytic materials are synthesised using transition metal (CoII, NiII, CuII) substituted lacunary Keggin polyoxometalates and tetrabutylammonium cations (TBA-TMSPOMs) and used for atom-economic cycloaddition of carbon dioxide to various epoxides producing cyclic carbonates under ambient conditions. These hybrid materials have been characterised by powder XRD, TGA, SEM, TEM, FTIR and 31P NMR. A rapid and effective method towards quantitative conversion of aliphatic, cyclic, and aromatic epoxides to their respective cyclic carbonates under solvent-free conditions is described. The percentage conversion of various epoxides into their respective cyclic carbonates is confirmed by 1H NMR and gas chromatography. Of all the cyclcoaddition reactions studied, the epichlorohydrin shows nearly 100% selectivity with turnover frequency of 244 h−1. Among the three hybrid catalysts, ∼0.12 mol% of TBA-PWCo is adequate to achieve highest catalytic efficiency with over 95% conversion in 4 h at RT. This catalyst is recyclable and reusable up to five cycles without significant loss in activity.

The new phthalic acid-based deep eutectic solvent as a versatile catalyst for the synthesis of pyrimido[4,5-d]pyrimidines and pyrano[3,2-c]chromenes

A new DES (MTPPBr-PHTH-DES) was prepared from a mixture of methyltriphenyl-phosphonium bromide (MTPPBr) and phthalic acid (PHTH). The eutectic point phase diagram showed that a one-to-one molar ratio of MTPPBr to PHTH is the optimal molar ratio for the synthesis of new DES. Then, it was characterized with various techniques such as FT-IR, TGA/DTA, densitometer, eutectic point, and NMR and used as a novel acid catalyst in the synthesis of pyrimido[4,5-d]pyrimidines and pyrano[3,2-c]chromes in solvent-free condition. Short reaction time, low temperature, high efficiency, green condition, and easy recycling and separation of the DES catalyst are among the most important features of the presented method.