Solvent-free Approach Research Articles

Thermally Solvent-Free Cross-Linked pH/Thermosensitive Hydrogels as Smart Drug Delivery Systems

An imbalance in the body’s pH or temperature may modify the immune response and result in ailments such as autoimmune disorders, infectious diseases, cancer, or diabetes. Dual pH- and thermo-responsive carriers are being evaluated as advanced drug delivery microdevices designed to release pharmaceuticals in response to external or internal stimuli. A novel drug delivery system formulated as hydrogel was developed by combining a pH-sensitive polymer (the “biosensor”) with a thermosensitive polymer (the delivery component). Thus, the hydrogel was created by cross-linking, using a solvent-free thermal approach, of poly(N-isopropylacrylamide-co-N-hydroyethyl acrylamide), P(NIPAAm-co-HEAAm), and poly(methylvinylether-alt-maleic acid), P(MVE/MA). The chemical structure of the polymers and hydrogels was analyzed using Fourier-transform infrared (FTIR) and proton nuclear magnetic resonance (1H NMR) spectroscopies. The pH/thermosensitive hydrogel loses its thermosensitivity under physiological conditions but, remarkably, can recover the thermosensitive capabilities when certain physiologically active biomolecules, acting as triggering agents, electrostatically interact with pH-sensitive units. Our research aimed to develop a drug delivery system that could identify the disturbance of normal physiological parameters and instantaneously send a signal to thermosensitive units, which would collapse and modulate the release profiles of the drug.

Rapid and solvent-free construction of S-rich covalent organic polymer for efficient removal of mercury

Mercury (Hg(Ⅱ)) is an extremely hazardous heavy metal ubiquitously discovered in the global environment. Covalent organic polymers (COPs) have been recognized as promising adsorbents due to their exceptional properties tailored for Hg(II) sequestration. Nevertheless, the synthesis of the majority of COPs requires rigorous experimental conditions. Herein, a sulfur (S)-rich COP denoted as TpTU was successfully constructed using a solvent-free approach. Compared to TpUrea without S, TpTU exhibited superior Hg(Ⅱ) capture performance. The experimental results demonstrated splendid adsorption performance for Hg(Ⅱ) (187 mg·g−1), and the adsorption isotherm was well-fitted to the Freundlich model (R2 > 0.98). Meanwhile, adsorption equilibrium was achieved within 5 min, and thermodynamic analyses indicate that the adsorption process is endothermic in nature. In addition, TpTU exhibited exceptional selectivity for Hg(II) even in the presence of competing ions. The mechanism investment revealed that the incorporation of heteroatoms, particularly S and nitrogen (N), plays a critical role in enhancing the affinity of COP toward Hg(Ⅱ). Moreover, no significant loss is observed for its capacity even after eighth adsorption–desorption cycles, demonstrating remarkable reusability of TpTU. Furthermore, TpTU also achieved Hg(Ⅱ) removal efficiency of over 98.9 % in actual water samples. These results prove the practical potential of TpTU for the purification of Hg(II) polluted water, offering a promising avenue towards cleaner and safer water resources.

The Catalysts-Based Synthetic Approaches to Quinolines: A Review.

The most common heterocyclic aromatic molecule with potential uses in industry and medicine is quinoline. Its chemical formula is C9H7N, and it has a distinctive double-ring structure with a pyridine moiety fused with a benzene ring. Various synthetic approaches synthesize quinoline derivatives. These approaches include solvent-free synthetic approach, mechanochemistry, ultrasonic, photolytic synthetic approach, and microwave and catalytic synthetic approaches. One of the important synthetic approaches is a catalyst-based synthetic approach in which different catalysts are used such as silver-based catalysts, titanium-based nanoparticle catalysts, new iridium catalysts, barium-based catalysts, iron-based catalysts, gold-based catalysts, nickel-based catalyst, some metal-based photocatalyst, α-amylase biocatalyst, by using multifunctional metal-organic framework-metal nanoparticle tandem catalyst etc. In the present study, we summarized different catalyst-promoted reactions that have been reported for the synthesis of quinoline. Hopefully, the study will be helpful for the researchers.

Solvent-free mechanochemistry induced one-pot scalable fabrication of phosphorus wrapped keratin and its application as a synergistic flame retardant in epoxy resin

Here we synthesized a biomass phosphorus-wrapped wool keratin flame retardant using a one-pot sustainable ball milling method. While many bio-based flame retardants have been developed, most involve organic solvents and complex modification processes. Our study focuses on a solvent-free approach to develop an effective flame retardant through the covalently phosphating modification of keratin recycled from waste wool. With 5 wt% addition, the epoxy resin composites achieved V-0 rating, showing a 46.7% reduction in total heat release and a 23.8% reduction in total smoke production. The flame retardant effectively quenches free radicals in the gas phase and catalyzes char formation in the condensed phase through a synergistic phosphorus-nitrogen effect. This study underscores the significant potential of recycling biomass waste wool keratin for flame retardant applications via a solvent-free and one-pot high-energy ball milling method, offering valuable insights for green chemistry and sustainable low-carbon development.

Flux Synthesis of Robust Polyimide Covalent Organic Frameworks with High-Density Redox Sites for Efficient Proton Batteries.

Aqueous proton batteries are attracting increasing attention in the large-scale next-generation energy storage field. However, the electrode materials for proton batteries often suffer from low specific capacity and unsatisfactory cycle durability. Herein, we synthesize two highly crystalline and robust polyimide covalent organic frameworks (COFs) through a solvent-free flux synthesis approach with benzoic acid as a flux and catalyst. The as-synthesized COFs possess enriched redox-active sites for proton storage and intrinsic Grotthuss proton conduction, rendering them ideal candidates for proton electrode materials. The optimal COF electrodes achieve a high specific capacity of 180 mAh/g at 0.1 A/g, among the highest COF-based proton batteries, and exhibit an outstanding rate capability of up to 100 A/g and long-term cycling stability with capacity retention of 99% after 5000 cycles at 5 A/g. The assembled full cells deliver a specific capacity of 150 mAh/g at 0.2 A/g with a maximum energy density of 72 Wh/kg and a maximum supercapacitor-level power density of 64 kW/kg, surpassing all reported COF-based systems. This work paves a new avenue for the design of electrode materials for aqueous proton batteries with high energy density, power density, rate capability and long-term cycling stability.

A Convenient Approach for the Synthesis of Multidentate N-Heterocyclic Carbene Ligand Precursors.

Multidentate bis-NHCs ligands with various spacers are expected to combine the advantages of coordination chemistry and catalysis. These offer opportunities to construct various organometallic frameworks involving transition metals and main group elements. Therefore, developing a general procedure for synthesizing a variety of carbene salt precursors using a convenient technique is key in this context. The extended protocol of a solvent-free approach for synthesizing various bridged bis-imidazolium carbene salts, including tris and tetrakis-imidazolium precursors, is reported here. This method can be performed in the laboratory, leading to high yields (80-95 %) and isolated as analytically pure, multigram, bench-stable compounds.

Modulating the acidity of bimetallic functionalized Zr-based metal–organic frameworks with hierarchical porosity through solvent-free approach to enhance butyl butyrate production

Design of multivariate metal–organic frameworks (MOFs) provide new avenues to gain ultrahigh catalytic activity for target reactions, however, developing one-pot green approach for synthesizing multivariate MOFs remains challenging. In this work, a one-pot green approach was developed to synthesize bimetallic functionalized UiO-66(Hf-Zr)–COOH with high acidity and hierarchical porosity without the employment of solvent. The optimal UiO-66(Hf1/4-Zr)–COOH displayed an ultrahigh upgradation of catalytic efficiency in esterification reaction of butyric acid and butanol for producing butyl butyrate due to its hydrophilicity, hierarchical porosity, carboxyl group and bimetallic cluster, and the conversion of butyric acid to produce butyl butyrate reached 91.5 % under the optimal reaction condition. UiO-66(Hf1/4-Zr)–COOH showed excellent reusability in the esterification reaction for the conversion of butyric acid, and its activity and stability could be retained after being recycled 6 times. Such outstanding esterification activity could be mainly ascribed to excellent ability for absorbing the reactants, and the easy accessibility of plentiful acid sites. Our work provides a solvent-free approach for one-pot synthesizing multivariate MOFs to boost their catalytic performance for targeted reactions.

Solvent-free mechanochemical synthesis of Mg-gallic acid complex for the fabrication of high-performance supercapacitor porous carbon

At molecular level, it is challenging to construct a porous carbon from magnesium based template and low cost precursor by a facile route for supercapacitive energy storage, e.g. solvent-free approach because the coordination of magnesium ion with organic ligands usually needs participation of solvent. Herein, a balling milling mediated coordination of magnesium acetate and gallic acid was developed in the absence of solvent to prepare porous carbon. The key of the present strategy lies in the generation of volatile HAc, orienting the reaction in a favorable direction for the formation of complexes. The resultant porous carbon (denoted BGMC) owns a high microporostiy ratio (24.2 % vs template-free derived ones of 11.1 %), open accessed microstructure and hydrophobic character. As electrode for supercapacitor, in aqueous electrolyte, the BGMC based supercapacitor achieves a high energy density of 19.2 Wh kg−1@900 W kg−1, while, in organic electrolyte of 1.0 M TEABF4/AN, the symmetric device based on BGMC delivers energy in a wide voltage window of 0–3.5 V with large energy of 34.4 Wh kg−1@1750 W kg−1, which is superior to those of recently reported carbon based devices. And more, at high current density of 10 A g−1, the BGMC device can resist continual charge/discharge for 30 000 cycles, showing an excellent cycling stability. Our strategy involving solvent-freely coordination of template and precursor molecule to prepare porous carbon open up a route with facile, scalable and easy-operable attributes towards the preparation of functional porous carbon.

Chitin nanocrystal Pickering emulsions for sustainable release pesticide microencapsulation with superior leaf adhesion and enhanced safety

Traditional pesticides often exhibit high non-target toxicity, poor stability, short persistence, and susceptibility to wash-off by rain. Pesticide microencapsulation represents a significant advancement in formulation strategies, addressing safety and sustainability concerns associated with conventional pesticides. This study explores the utilization of biodegradable chitin nanocrystals (ChNCs), prepared via acid hydrolysis, for the development of pesticide microcapsules. Specifically, ChNCs were employed to emulsify molten pesticides, followed by interfacial polymerization to fabricate pesticide-loaded microcapsules. Using molten emulsification and Pickering emulsion templates offer a simple and solvent-free approach for microcapsule preparation, eliminating the need for conventional surfactants. The microcapsules displayed a size distribution ranging from hundreds of nanometers to several micrometers, which could be tuned by adjusting the ChNCs content. These microcapsules demonstrated remarkable properties, including a high pesticide loading capacity (reaching 78.7% for lambda-cyhalothrin), excellent storage stability, and enzyme-responsive release behavior. Furthermore, the abundant positive charges enhanced the interaction between the microcapsules and leaf surfaces, leading to improved pesticide retention. Microencapsulation reduces acute insecticidal activity of pesticides due to the slow-release effect; however, field experiments provide compelling evidence that microcapsule formulations significantly prolong pesticide efficacy compared to conventional formulations. Additionally, microencapsulation significantly improved the safety of pesticides, with the LC50 increasing from 0.0116 mg/L to 3.75 mg/L. Overall, this study introduces a promising method for pesticide microencapsulation using ChNCs Pickering emulsion, highlighting its potential advantages and providing valuable insights for the development of environmentally friendly and novel pesticide formulations.

Mechanochemistry: A Resurgent Force in Chemical Synthesis

AbstractMechanochemistry, a solvent-free approach that harnesses mechanical energy, is emerging as a transformative technique in modern chemistry. It has emerged from a niche technique to a versatile tool with broad applications. By inducing physical and chemical transformations, it enables the synthesis of complex molecules and nanostructured materials. Recent advancements have extended its applications beyond simple physical transformations to encompass catalytic processes, unlocking new possibilities for selective synthesis and product design. This account delves into the fundamentals of mechanochemistry and its applications in organic synthesis, also beyond traditional synthetic routes. Mechanochemistry offers new avenues for molecular and materials discovery, expanding the scope of accessible chemical space.1 Introduction2 Organic Synthesis in Ball Mills3 Combination with Different Energy Sources4 Advantages of Mechanochemistry5 Future of Mechanochemistry6 Conclusion

Synthesis of New Xanthene and Acridine Derivatives from Cyclohexan-1,3-dione and the Study of their Antiproliferative Activities

Background: Ionic immobilized liquids and multi-component reactions are integral to green chemistry, facilitating the synthesis of biologically active compounds, such as xanthene and acridine derivatives. These approaches have garnered significant attention in recent years. Objective: The aim of this study was to synthesize novel xanthene and acridine derivatives with diverse substituents and heterocyclic rings. Furthermore, the research sought to evaluate their anticancer activity against various cancer cell lines and analyze their structure-activity relationships (SAR) to determine how structural modifications impact their biological effectiveness. Method: The core compounds in this study were synthesized from cyclohexane-1,3-dione and triethoxymethane under two distinct reaction conditions. The first involved the use of a solvent with either Et₃N or NH₄OAc as a catalyst, while the second employed a solvent-free approach using an ionic liquid catalyst (ILs). Results: The anti-proliferative activity of all synthesized compounds was evaluated against six selected cancer cell lines, revealing that many compounds exhibited significant inhibitory effects. Furthermore, their inhibitory potential against tyrosine kinases and Pim-1 kinases was assessed, along with an investigation of their mechanism of action on tyrosine kinases. Conclusion: The anti-proliferative activity of the newly synthesized compounds was evaluated against six cancer cell lines. Many of the compounds exhibited strong inhibitory effects not only against the tested cancer cell lines but also against tyrosine kinases and Pim-1 kinases.

Promoting proximity to enhance Fe-Ca interaction for efficient integrated CO2 capture and hydrogenation

Integrated CO2 capture and utilization (ICCU) using “capture-conversion” dual functional materials (DFMs) paves a cost-effective path for restricting CO2 emissions by eliminating the energy-intensive intermediate processes. The interactions between catalysts and absorbents are believed pivotal in ICCU; however, there is a lack of environment-friendly strategy to fabricate the interaction for industrial applications. Here, we propose a solvent-free mechanochemical approach to promote the interaction by improving the proximity between natural calcium and iron sources. The interaction was systemically investigated and confirmed using XRD, XPS, TEM, TPR, etc. As a result, the mechanochemical approach derived DFM achieved 5.5 mmol g−1 CO2 capacity, 87 % CO2 conversion, and 100 % CO selectivity at 650 °C, significantly outperforming the CaO-alone benchmark (CO2 capacity < 4.5 mmol g−1, CO2 conversion < 73 %). Further incorporating MgO would alleviate the sintering and promote the CO2 capture stability (< 15 % decrease after 20 cycles) by acting as a thermal-stable barrier. Based on in situ XRD, it is further confirmed that Fe-Ca interaction exhibits a dynamic looping mechanism in ICCU. The techno-economic analysis strongly supports the superiority of ICCU catalyzed by naturally sourced DFMs on eliminating the energy and H2 consumption for CO2 capture and upgradation. As a result, producing CO via ICCU using mechanochemical derived DFMs exhibits 20 % and 10 % cost decrease compared to the conventional CCU and ICCU using CaO alone scenarios, pointing out the potential of ICCU technology in industrial applications.

A Green Solvent-Free Approach Synthesis for Rational Designing of a NiFe-Layered Double Hydroxide [NiFe-LDH] Electrocatalyst for Hydrogen Generation

A Green Solvent-Free Approach Synthesis for Rational Designing of a NiFe-Layered Double Hydroxide [NiFe-LDH] Electrocatalyst for Hydrogen Generation

Biobased recyclable epoxy composites reinforced with carbon nanotubes for electromagnetic interference shielding and Joule heating

AbstractCurrent epoxy thermosets are facing various challenges such as resource scarcity, environmental concern, and limited functionalities. Here, we present a novel solvent free approach to fabricate multifunctional carbon nanotubes (CNTs) reinforced biobased and recyclable epoxy thermoset composites through precuring in an internal mixer followed by curing in an oven. The epoxy matrix, a covalent adaptable network (CAN) based on dynamic imine bonds, was synthesized from entirely biobased feedstocks, including glycerol triglycidyl ether, vanillin, and 1,10‐diaminodecane. The shear force during precuring facilitated dispersion of CNTs in CAN matrix, allowing for high CNTs loading (up to 20 wt%). The well‐dispersed CNTs not only reinforced mechanical properties of CAN but also introduced new functionalities like electrical conductivity, electromagnetic interference (EMI) shielding capacity, and Joule heating performance. The composite with 20% CNTs exhibited a tensile strength and Young's modulus of 78.1 MPa and 3.07 GPa, respectively, marking a 34.2% and 63.6% improvement over pristine CAN. It also demonstrated a high electrical conductivity of 35.3 S/m, resulting in a remarkable EMI shielding effectiveness (22.8 dB) and excellent Joule heating performance (reaching 131.7°C at 27 V input). Furthermore, these composites are thermally and chemically recyclable due to dynamic imine bonds, promoting sustainability and circular economy.

Enzymatic synthesis of ω-3 fatty acids-based structured phospholipids: A novel solvent-free preparation approach and its catalytic mechanism

ω-3 fatty acids-based phospholipids (ω-3-PLs) exhibit higher bioavailability within organisms and stability compared to polyunsaturated fatty acids in their neutral forms. In this study, ω-3 fatty acids enriched partial acylglycerols (ω-3-AGs) were produced from hydrolysis of algal oil firstly. The effects of hydrolysis processing parameters such as enzyme type, enzyme loading, oil-water ratio, reaction temperature, and time were evaluated. Subsequently, ω-3-PLs were prepared via interesterification of ω-3-AGs with PLs catalyzed by PLA1. When monoacylglycerols (MAGs) reached 60% in partial acylglycerols, the interesterification reaction showed a marked improvement, leading to the achievement of the optimal final ω-3-PLs content of 38.93%. Using molecular docking techniques to speculate on the catalytic mechanism, the results indicate that MAGs exhibit an affinity of up to −6.33 kcal/mol with PLA1, verifying their critical role in the interesterification process.

Green synthesis and characterization of titanium dioxide nanoparticles and their photocatalytic activity

In this study, we compared two low-temperature synthesis procedures for the large-scale production of titania nanoparticles (NPs). The first takes place in an aqueous medium with an acidic environment, by using a triblock polymer surfactant (Pluronic 123). The second involves a polycondensation reaction of alkoxide precursors at 70 °C in a water-in-oil (W/O) microemulsion with a volume ratio of 1:1, using cetylpyridinium bromide (CPB) as a cationic surfactant. The morphological and structural characterization of the samples was carried out through Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD). The photoactivity of the nanostructured titania was evaluated by measuring the photodegradation of Methylene Blue (MB). The solvent-free synthetic approach provided spherical titania nanoparticles mainly constituted by rutile crystallites with a very good synthetic yield. However, the photodegradation rate of MB for such titania nanoparticles ranges from 30 % to 40 %, after 1h under solar irradiation. Conversely, titania nanoparticles obtained through microemulsion synthesis show a photodegradation rate of more than 90 % comparable to titania P25. This high-yield synthesis leads to the formation of TiO2 nanoparticles characterized by small crystallite aggregates (rutile and anatase).

Solvent-free green synthesis of anion exchange membranes via photo-polymerization for efficient desalination by electrodialysis

A green anion exchange membrane for electrodialysis desalination was synthesized using a solvent-free photo-polymerization approach. Vinylbenzyl chloride (monomer), tripropylene glycol diacrylate (crosslinker), and photoinitiator were mixed and subjected to UV polymerization for 20 min to create the base membrane, followed by positive charge modification with 1-methylimidazole. This method avoids organic solvents, offering economic and environmental benefits. By adjusting the degrees of crosslinking and positive charge, precise control over the membrane's microstructure and properties was achieved. The optimized membrane showed an area resistance of 1.67 Ω cm2 and a transport number of 0.956, demonstrating exceptional electrochemical performance. Under comparable conditions, the optimized membrane improved the NaCl removal rate by 11.47 %, increased current efficiency by 10.61 %, and reduced energy consumption by 16.75 % compared to commercial AMV membrane, highlighting its potential for scalable seawater desalination through electrodialysis.

In Situ Enzymatic Polymerization of Ethylene Brassylate Mediated by Artificial Plant Cell Walls in Reactive Extrusion.

Herein, we describe a solvent-free bioinspired approach for the polymerization of ethylene brassylate. Artificial plant cell walls (APCWs) with an integrated enzyme were fabricated by self-assembly, using microcrystalline cellulose as the main structural component. The resulting APCW catalysts were tested in bulk reactions and reactive extrusion, leading to high monomer conversion and a molar mass of around 4 kDa. In addition, we discovered that APCW catalyzes the formation of large ethylene brassylate macrocycles. The enzymatic stability and efficiency of the APCW were investigated by recycling the catalyst both in bulk and reactive extrusion. The obtained poly(ethylene brassylate) was applied as a biobased and biodegradable hydrophobic paper coating.

Mechanochemical Polyoxometalate Super-Reduction with Lithium Metal.

In this first systematic investigation of mechanochemical polyoxometalate (POM) reduction, (TBA)3[PMo12O40] was reacted with n equiv of lithium metal (n = 1-24) to generate PMo12/n products which were shown to be mixtures of electron-rich PMo12Lix species. FTIR analysis revealed the lengthening/weakening of terminal Mo═O bonds with increasing levels of reduction, while EXAFS spectra indicated the onset of Mo-Mo bond formation at n ∼ 8 and a significant structural change at n > 12. Successive MoVI reductions were monitored by XANES and XPS, and at n = 24, results were consistent with the formation of at least one MoIV-MoIV bonded {MoIV3} triad together with MoV. Upon dissolution, the PMo12Lix species present in the solid PMo12/n products undergo electron exchange and single-peak 31P NMR spectra were observed for n = 1-12. For n ≥ 16, changes in solid state and solution 31P NMR spectra coincided with the emergence of features in the UV-vis spectra associated with MoV-MoV and {MoIV3} bonding in an ε-Keggin structure. Bonding between {Li(NCMe)}+ and 2-electron-reduced PMo12 in (TBA)4[PMo12O40{Li(NCMe)}] suggests that super-reduction gives rise to more extensive Li-O bonding that ultimately causes lithium-oxide-promoted TBA cation decomposition and POM degradation, which might explain the appearance of XPS peaks for Mo2C at n ≥ 16. This work has revealed some of the complex, unexplored chemistry of super-reduced POMs and establishes a new, solvent-free approach in the search for a better fundamental understanding of the electronic properties and reactivity of electron-rich nanoscale metal oxides.

A microwave-assisted, solvent-free approach for effective grafting of high-permittivity fillers to construct homogeneous polymer-based dielectric film with high energy density

Polymer-based dielectric film capacitors are essential energy storage components in high-power energy storage devices benefiting from their high breakdown strength (Eb) and ultra-fast charge storage/release capability. However, the state-of-the-art commercial capacitor, biaxially oriented polypropylene (BOPP), exhibits limited energy storage density primarily due to low dielectric constant, which hinders the advancement of the film capacitor industry. Introducing high-permittivity (high-k) nanofillers into PP matrix to improve polarization is a promising method but poor filler dispersion leads to a remarkable decrease of Eb, while various strategies to enhance dispersion of fillers typically require sophisticated process involving toxic procedure and consuming significant time and cost. Herein, we show that a novel and scalable surface grafting method for high-k fillers can be achieved by a facile and short-period microwave irradiation with the assistance of silane coupling agent (KH560). As a demonstration, the KH560 is effectively grafted onto the surface of barium titanate (BT), achieving a high grafting ratio of 4.91 % at a yield of 85.1 % within a short time (40s). Furthermore, the surface modified BT nanofillers are introduced into PP matrix and then biaxially stretched. The as-prepared film exhibits excellent dispersion and superior compatibility, resulting in a remarkable enhancement of tensile strength (from 82 MPa to 115.4 MPa), breakdown strength (from 200 MV/m to 254 MV/m), and energy density (from 1.49 J/cm3 to 2.21 J/cm3). This work proposes a new strategy for constructing homogeneous polymer-based dielectric film by microwave activating high-k fillers and is crucial for the design of next-generation energy storage devices.